International Journal of Surgery 16 (2015) 23e30
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Original research
Intraoperative monitoring of cerebral NIRS oximetry leads to better postoperative cognitive performance: A pilot study ski a, Wojciech Gaszyn ski a, Tamara Trafidło a, Tomasz Gaszyn Katarzyna Nowakowska-Domagała b, * a b
skiego 22, Poland Department of Anaesthesiology and Intensive Therapy, Medical University of Lodz, PL 91-153 Lodz, ul. Kopcin Department of Psychosocial Rehabilitation, Medical University of Lodz, Lodz 90-647, 1 Hallera Sq. Building 7, Room 108, Poland
h i g h l i g h t s We use NIRS intraoperative monitoring to prevent incidents of brain desaturations. NIRS monitoring leads to better postoperative cognitive performance. NIRS may be useful in reducing POCD in patients operated on in the prone position.
a r t i c l e i n f o
a b s t r a c t
Article history: Received 10 August 2014 Received in revised form 4 February 2015 Accepted 12 February 2015 Available online 18 February 2015
Objectives: The aim of this study is the assessment of the regional cerebral oximetry e NIRS (near infrared spectroscopy) as an intraoperative monitoring system to protect the patient against the incidents of brain desaturations. We hypothesize that patients monitored with NIRS present a smaller range of postoperative cognitive dysfunctions (POCD) in comparison with those without NIRS monitoring during lumbar spine surgery in a prone position. Settings: This study was performed at the Clinical Department of Neurosurgery and Oncology of the Central Nervous System, Medical University of Lodz, Poland. Participants: The study completed 43 adult patients qualified for the surgical treatment of lumbar spondylosis. Before the procedures they were randomized into two subgroups: one monitored intraoperatively by means of NIRS cerebral oximetry (INVOS 5100), which numbered 13 patients e 30.2% (13 NIRS devices were made available to the authors) and the other without NIRS intraoperative monitoring, totaling 30 people e 69.8%. The patients who presented a history of psychiatric, neurological and cardiovascular disorders which impair cognitive processes were disqualified from the study. Primary and secondary outcome measures: A comprehensive battery of neuropsychological tests was preoperatively performed on all patients. The subjects were then divided into two groups: with and without NIRS monitoring. Both groups were statistically homogeneous. Computerized anesthesia records were used to obtain intraoperative data: mean arterial pressure, heart rate, pulsoximetry and cerebral regional oxygenation. The depth of anesthesia monitor was not used. Besides, all the patients passed the same battery of neurocognitive tests 7 days and 1 month postoperatively. The ManneWhitney test was performed to compare POCD and therefore assess the usefulness of NIRS as a monitoring mechanism during anesthesia in the prone position. Results: There was a significant (p < 0.05) difference in the presence of cognitive deficiencies between the subgroup monitored with NIRS and the subgroup without NIRS. It included: Digit Span Test overall score and forward repetition score 7 days after operation, N- back Test results after 30 days in version 0 “back” e time, N-back Test version 1 “back” results in the number of correct answers and the number of errors.
Keywords: Brain tissue oxygen monitoring Near infrared spectroscopy Prone position Postoperative cognitive dysfunctions (POCD)
* Corresponding author. E-mail addresses: tamara.trafi[email protected] (T. Trafidło), tomasz.gaszynski@ ski), [email protected] (W. Gaszyn ski), umed.lodz.pl (T. Gaszyn [email protected] (K. Nowakowska-Domagała). http://dx.doi.org/10.1016/j.ijsu.2015.02.009 1743-9191/© 2015 Surgical Associates Ltd. Published by Elsevier Ltd. All rights reserved.
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Conclusions: NIRS cerebral oximetry may be useful in reducing postoperative cognitive complications in patients operated on in the prone positioning. Trial registration: RNN/556/08/KB e approval of the ethics committee at Medical University of Lodz, Poland. © 2015 Surgical Associates Ltd. Published by Elsevier Ltd. All rights reserved.
1. Introduction Postoperative cognitive dysfunction (POCD) is a subtle disorder of thought processes, which may influence isolated domains of cognition such as executive functions, verbal and visual memory, language abilities, visuospatial abstraction, attention and concentration [1e3]. Research in the area of POCD reduction and improvement of clinical anesthesia to facilitate cognitive recovery is a high priority in the contemporary anesthesia. The undetected intraoperative incidents of the prefrontal cortex desaturation contribute to the development of cognitive dysfunctions disrupting cognitive performance of patients after the surgery [4,5]. Another early postoperative side effects such as emergence agitation and emergence delirium (possibly connected with desaturation) are resource consuming and may cause serious complications [6e8]. The EEG based depth-of-anesthesia monitors facilitating titration of depth of anesthesia and thus possibly reducing the risk of a too deep anesthesia and subsequent decrease in systemic blood pressure and potentially cerebral perfusion has been shown to have a possible positive effect [9e11]. Simultaneously the monitoring of oxygen saturation in the prefrontal cortex is not yet a routine. Therefore, the hypothesis that monitoring of cerebral oxygenation could improve postoperative cognitive recovery and reduce risk of cognitive side effects is worth of empirical investigation. The aim of this study is to assess the value of the cerebral oximetry monitor (NIRS, near infrared spectroscopy) in detecting and diminishing intraoperative episodes of desaturation of the prefrontal cortex in patients operated on in the prone position due to lumbar spondylosis. It has been analyzed whether there is any correlation between the reduction of intraoperative episodes of desaturation of the prefrontal cortex detected by the NIRS cerebral oximetry and postoperative level of neurocognitive performance in patients operated on in the prone orientation. 2. Methods 2.1. Subgroups of patients After obtaining the approval of the Bioethics Committee (RNN/ 556/08/KB), all 43 adult patients qualified for the surgical treatment of lumbar spondylosis in the Clinical Department of Neurosurgery and Oncology of the Central Nervous System, Medical University of Lodz, Poland in the year 2012, were included in the study. The surgical procedures were performed in the prone positioning and included laminectomy, hemilaminectomy and discectomy within the lumbar spine. Before the procedures the patients were randomized into two subgroups: one monitored intraoperatively by means of NIRS cerebral oximetry (INVOS 5100, Somanetics Corporation, USA), which numbered 13 patients (30.2%) and the other without such monitoring (30 patients 69.8%). The total number of the monitored patients in this pilot study is a result of the temporal limitation and shortage of NIRS sensors. The total number of patients is accidental. Fisher's exact test (p > 0.05) showed no differences between
two subgroups in terms of the participation of women and men, age, years of education, the participation of smokers, the presence of cardiovascular diseases, the presence of the symptoms of depression measured by the Beck Depression Inventory (BDI) or duration of anesthesia. The two groups also did not differ significantly (p > 0.05) in the terms of: atrial fibrillation, cardiac arrhythmias, valvular diseases and the use of pharmacological treatment for the above reasons presence of diabetes, hypertension and antihypertensive therapy, hyperlipidemia and the presence of hypolipemic therapy. 2.2. Exclusion criteria The patients with a history of neurological and psychiatric disorders which impair cognitive processes were disqualified from the study. These include previously established dementia, stroke, schizophrenia and depression. The individuals undergoing or with a history of treatment with hypnotics, antidepressants, anxiolytics and steroids were also excluded from the study. Also those, who reported frequent alcohol consumption (above 50 g per day) and whose preoperative laboratory tests showed elevated GGT (gamma-glutamyl transpeptidase) and macrocytosis with hyperchromia were disqualified. The efficiency of cognitive processes is also affected by the coexistence of cardiovascular disease, smoking and depressed mood. Comparative analysis of the breakdown of tobacco smokers and of individuals with symptoms of depression according to Beck Depression Inventory (BDI) gave similar test results. In those cases, the Fischer test revealed no significant difference between the subgroup monitored with NIRS cerebral oximetry and the one without NIRS (p > 0.05). 2.3. The battery of neuropsychological tests The prefrontal cortex, where a local measurement of NIRS takes place, is the anatomical location of working memory structures, which lie at the basis of executive functions. Its image is not uniform and includes various operational stages, such as planning, initiating and monitoring progress. Therefore, in the evaluation of postoperative cognitive deficiencies a battery of tests must be employed. All trial patients were subject to presurgical neuropsychological examinations in the form of a battery of tests such as visual working memory N-back Test (NBT), Trail Making Test A & B, (TMT A & B), Stroop Color-Word Interference Test Part 1 and 2 (Stroop 1 & 2), Verbal Fluency Test (FAS), Digit Span Test e forward and backward repetition of numbers (DST) and the Mini Mental State Examination (MMSE) [12,13]. The preoperative test results were the basis for the assessment of postoperative cognitive dysfunctions in the entire sample of the patients tested. Re-evaluation of cognitive processes with the same tests was made at 7 and 30 days after the operation. All the participants completed all the tests (there were no missing data). The present study compared cognitive deficiencies between the group supervised with NIRS and the one without such monitoring. Description of the test sequence is shown in Fig. 1. It is assumed that
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Fig. 1. Description of the a battery of tests employed in the evaluation of postoperative cognitive deficiencies.
20% deterioration in repeated neuropsychological acknowledged as cognitive loss [13,14].
tests
is
2.4. Intraoperative conditions Both groups of patients were subjected to anesthesia by entirely intravenous route: propofol 4e10 mg/kg (Propofol, Fresenius Kabi, Germany), remifentanil 0.05e0.10 mg/kg bw (Ultiva, Glaxo Smith Kline, UK), atracurium 0.6 mg/kg (Tracrium, Glaxo Smith Kline, UK). Additionally, each patient was ventilated in CMV mode, FiO2 ¼ 0.50, Vt ¼ 8 ml/kg, respiratory rate - 10/min, normocapnia (pCO2 from 35 to 45 mmHg). After administering anesthesia, the patients were placed in the prone position. Detailed description of this procedure can be found at Edgcombe et al. [15]. Upon the completion of the neurosurgery the patient was again placed in the supine position. The main objective of intraoperative care of the patient during a surgical treatment of lumbar spondylosis is to maintain a normal level of mean arterial pressure (MAP), normocardia and normal ranges of pulse oximetry saturation. Furthermore, in the one of the observed groups, monitoring of cerebral oximetry complemented the standard routine of intraoperative hemodynamic monitoring. In the presented study cerebral oximetry monitoring with INVOS 5100 was employed. In the case of cerebral oximetry, NIR penetration depth is specifically selected in such a way as to bypass the scalp and skull. Based on the differences in absorption, the monitor determines local variations of oxygenated hemoglobin in the tissue capillaries located in the prefrontal cortex [16,17]. NIRS cerebral oximetry reading occurs in real-time, continuously. The onset of the bilateral oximetry measurement in the group of patients monitored with NIRS took place 15 min prior to the induction of anesthesia. A downward tendency of ScrO2 oximetry index (cerebral regional oxygen saturation) by more than 20% from the baseline may be a manifestation of a significant tissue hypoxia [16,17]. The measured values of ScrO2 at the output in INVOS 5100 most frequently
oscillated above 70 units. The definition of significant changes in ScrO2 for interventions was the decline below 40 units, what was considered as an indicator of deep hypoxic CNS. A careful consideration is recommended whenever deliberate hypotension is requested by the surgeon. The observers kept mean arterial pressure above 65 mm Hg. In the present study, intraoperative decreases in values of cerebral oximetry, MAP and pulse oximetry saturation were recorded and statistically analyzed. The number of intraoperative interventions which improve hemodynamic conditions was counted and compared between the two subgroups. Consequently, interventions were introduced in the patients without the NIRS monitoring at the time of changes in parameters: MAP, HR above the range of 60e100/min, SpO2 below 95%. Whereas in the group of patients monitored with NIRS interventions enhancing cerebral oxygen saturation were based additionally on the declines in the value of ScrO2. Detailed parameters set by investigators which instigated intervention are presented in (Fig. 2) which was designed on the basis of the algorithm in the use of brain oximetry proposed by Denault et al.[17]. Observers were not blinded, as the use of NIRS monitoring is non-invasive and does not alter procedures for conducting anesthesia. Besides, the amount of interventions which were taken in the group supervised with NIRS and in the group without such monitoring was additionally observed. It required active observations of NIRS monitor by the investigator. INVOS 5100 records values of ScrO2 in Windows Excel sheets or in the form of Excel graphics. HR and SpO2 parameters were recorded using Datex Ohmeda GE Healthcare printer configured with Cardiocap monitor which is used for routine intraoperative monitoring. The course of anesthesia together with moments of interventions were recorded in protocols of routine anesthesia. Episode of each intervention was also recorded in the files of the INVOS 5100. Intraoperative interventions occurred simple and no
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Fig. 2. Algorithm of procedures applied in the decline in the value of NIRS cerebral oximetry. ScrO2 e local saturation of the cerebral cortex; MAP e mean arterial pressure; SaO2 e oxygen saturation of arterial blood; Hb e hemoglobin; CO e cardiac output; ScvO2 e central venous oxygen saturation; CMRO2 e cerebral metabolic rate of oxygen; ICP e intracranial pressure.
constrictors were used. They focused mainly on improving the head positioning whenever ScrO2 declined by 20% from the baseline. When SpO2 declines were noted, observers improved the orientation of pulse oximeter sensor. If this intervention was not effective the increase of FiO2 took place. When the changes of MAP ±20% of baseline were found, the observers suited the supply of drug intravenous infusion (totally intravenous anesthesia) and the insertion of fluid volume. The total fluid loading during the anesthesia course was 4 ml/kg/hr. In the group of the observed patients there was no need for further cardiovascular support in the form of catecholamines or ephedra. During episodes of bradycardia (HR < 60/min) adequate doses of atropine were given and the depth of anesthesia was reduced. Before arousal from anesthesia all
patients were administered Ketoprofen. Support during the early and intermediate postoperative course was standardized at the Clinical Department of Neurosurgery and Oncology of the Central Nervous System, Medical University of Lodz, Poland. The goal of postoperative pain management was achieved through the supply of Ketoprofen and Paracetamol. No COX-2 inhibitors were used. The patients did not require postoperative supply of steroids or opioids. No local anesthesia was used. No blood loss requiring transfusion occurred. Thromboprophylaxis consisted in the use of adequate doses of low molecular weight heparin (enoxaparin).
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3. Results
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Table 2 Results of ManneWhitney U test for variables in the subgroups.
Statistics of measurable parameters in both subgroups e one monitored with cerebral oximetry and the other without monitoring e are presented in Table 1. Comparative analysis of the values of measurable parameters in both subgroups showed no statistically significant differences for the time of anesthesia, age and years of education (p > 0.05). However, a significant difference (p < 0.05) occurred for both subgroups in the quantities of intraoperative interventions which improve hemodynamic conditions. More interventions occurred in the group without NIRS monitoring. Values of probability for the ManneWhitney U test are demonstrated in Table 2. The statistical analyses of the declines in the intraoperative cerebral oximetry and MAP are presented in Table 3. In some patients, the Pearson correlation coefficient demonstrated a positive correlation between the increase in ScrO2 parameters and the increase of MAP (Fig. 3). This relationship is consistent with the generally acknowledged fact of the cerebral perfusion improvement during an increase in mean arterial pressure. However, the rest of the patients showed no significant relationships for NIRS and MAP. In some cases, declines in NIRS parameters occurred at constant MAP readings (Fig. 4). Therefore, it can be assumed that additional factors, such as excessive tilt of the head of the examined patient must have been involved. Such positioning may affect perfusion and the outflow of blood from the head, despite normal readings of cardiovascular blood circulation parameters. In each of these cases readjustment of the head positioning increased NIRS oximetry readings. In the remaining patients a constant level of NIRS readings was registered with declines in MAP (Figs. 5 and 6). This can be explained by effective mechanisms of autoregulation of cerebral blood flow. In addition, when declines in the values of NIRS readings took place, parameters of SpO2 and HR remained within normal ranges and did not undergo any reduction (Fig. 4). Apart from that, correlative dependence between SpO2 and the values of ScrO2 occurred only in the case of three patients. Then the ScrO2 and SpO2 showed almost no deviation from the normal value. No case of a dramatic fall in the value of arterial blood saturation (SpO2) in the cardiovascular circulation was reported in the entire study sample. The non-parametric ManneWhitney test was used to make a comparison of average values of the cognitive tests. Statistically significant (p < 0.05) difference in the presence of cognitive deficiencies between the subgroup monitored with NIRS and the subgroup without NIRS include: DST overall score and forward repetition score 7 days after operation, NBT results after 30 days in version 0 “back” e time and the results in the NBT version 1 “back” in the number of correct answers and errors. Significant results of ManneWhitney test for differences in cognitive tests in the group with and without NIRS are presented in Table 4. The performance
Parameter
Test U statistics
Normalized statistics
P level
Anesthesia time [min] Number of interventions Age Years of education
177.0000 52.5000 180.5000 184.0000
0.243689 3.549894 0.148921 0.054153
0.807472 0.000385 0.881616 0.956813
Table 3 Characteristics of significant declines in ScrO2 in the group monitored with NIRS. The correlation between cerebral oximetry values and the values of MAP (Pearson's correlation coefficient). Patient number
Number of episodes of ScrO2 reduction
Total duration of episodes of ScrO2 reduction
Number of episodes of MAP reduction
Correlation between NIRS and MAP
1 2 3
0 0 5 (1 unilaterally, 4 on both sides) 0 7 (unilaterally) 10 (both sides) 0 3 (both sides) 0 3 (unilaterally) 1 (both sides) 3 (unilaterally) 0
e e 20 min
4 0 11
Yes No Yes
e 30 min
7 5
No Yes
40 min
7
Yes
e 10 min
5 4
No No
e 10 min
6 36
Yes No
5 min
2
Yes
10 min
10
No
0
Yes
4 5 6 7 8 9 10 11 12 13
e
level of other neuropsychological tests between the subgroups was unchanged. 4. Discussion Assessment of cognitive performance is not a standard element of existing quality of recovery scales. Nevertheless in our opinion the preservation of the patients' quality of life which is certainly influenced by the level of cognitive functioning is of particular importance. There is indeed no full consensus around the definition, the explicit limit, change/decline that defines POCD. The International Study of Postoperative Cognitive Dysfunction (ISPOCD) group used an extensive test battery and used explicit changes where postoperative cognitive function is assessed in isolation from assessment of other recovery domains. Likewise the Postoperative
Table 1 Basic statistics for the measurable variables in the subgroups investigated. Group
Parameter
N
Mean
95% CI
NIRS
Anesthesia time [min] Number of interventons Age Years of education Anesthesia time [min] Number of interventons Age Years of education
12 12 12 12 31 30 31 31
188.75 2.66 50.58 12.25 196.29 7.23 49.22 12.16
143.05 0.59 40.32 11.00 170.44 5.99 44.12 10.83
Without NIRS
234.44 4.73 60.84 13.49 222.14 8.47 54.32 13.49
Median
Minimum
Maximum
Q1
Q3
SD
185.00 2.00 49.50 12.00 185.00 6.00 53.00 12.00
105.00 0.00 30.00 10.00 95.00 3.00 25.00 10.00
380.00 10.0 87.00 17.00 330.00 15.00 69.00 20.00
145.00 0.00 38.50 11.00 150.00 5.00 36.00 11.00
207.50 4.00 58.50 12.50 235.00 10.00 62.00 14.00
71.92 3.25 16.14 1.95 70.47 3.31 13.89 3.62
N e the number of patients, 95% CI e the end of the confidence interval for the mean in the population upon accepting a confidence level of 0.95, Q1 e the lower quartile, Q2 e the upper quartile value, SD e standard deviation.
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T. Trafidło et al. / International Journal of Surgery 16 (2015) 23e30
Fig. 3. Graph of MAP (mean arterial pressure), NIRS1 and NIRS2 (near infrared spectroscopy e cerebral oxygen saturation) correlations in a 32 year e old woman participating in the study. A positive correlation between the recorded parameters was detected.
Fig. 6. Graph of MAP (mean arterial pressure), NIRS1 and NIRS2 (near infrared spectroscopy e cerebral oxygen saturation) correlations in a 29 year e old woman participating in the study. The arrow indicates the decrease in MAP during which no declines in the value of NIRS were detected.
Table 4 Results of ManneWhitney test for differences in cognitive test results in the group with and without NIRS. Significant differences in Test U Normalized P level the tests results statistics statistics DST overall e after 7 days DST forward e after 7 days NBT 0 back e time after 30 days NBT 1 back e number of correct answers after 30 days NBT 1 bac e number of wrong answers after 30 days Fig. 4. Graph of MAP (mean arterial pressure), SpO2 (systemic pulse oximetry saturation), NIRS1 and NIRS2 (near infrared spectroscopy e cerebral oxygen saturation) correlations in a 60 year-old woman participating in the study. No positive correlation between the recorded parameters was detected. The arrow indicates unilateral decreases in the value of NIRS2 despite increases in MAP. SpO2 values remain unchanged, despite the fluctuations in the value of NIRS.
Fig. 5. Graph of MAP (mean arterial pressure), NIRS1 and NIRS2 (near infrared spectroscopy e cerebral oxygen saturation) correlations in a 60 year e old man participating in the study. The arrow indicates the decrease in MAP with no decreases detected in the value of NIRS.
Quality of Recovery Scale that includes cognitive tests is a useful tool for assessment of postoperative cognitive recovery [18,19]. Our study emphasize the clinical importance of NIRS and its impact on the postoperative rehabilitation, patient's quality of life
N (without N (NIRS NIRS) group)
77,0000 2,95134
0,003164 31
12
82,5000 2,80242
0,005072 31
12
84,0000 2,47454
0,013341 31
11
69,0000 2,90366
0,003689 31
11
69,0000 2,90366
0,003689 31
11
and therapy cost effectiveness. The significance of intraoperative desaturation is supported by the findings of Shroyer et al. [20] which showed that postoperative problems caused by desaturation include delirium (incidence 10e60 %) and POCD (incidence 24e53 %) which lead to a longer hospital length of stay. Furthermore the existing literature demonstrates that cognitive dysfunctions after noncardiac surgery were associated with increased mortality, risk of leaving the labor market prematurely, dependency on social transfer over longer term follow-up [2]. We showed that cerebral oximetry intraoperative monitoring reduces postoperative cognitive decline and leads to better postoperative cognitive performance measured by the Digits Span Test and N-back test because a pragmatic intervention to optimize cerebral oxygenation triggered by the NIRS monitoring conferred a significant reduction in postoperative cognitive impairment. Although few studies have specifically investigated the effect of intraoperative NIRS monitoring on the postoperative cognitive performance decline, our results are consistent with the existing literature. In particular they are supported by the findings of: Casati et al. [21] which showed that less cognitive decline was observed among patients where cerebral hypoxia was prevented by adequate monitoring and Slater et al. [22] which showed that cerebral oxygen desaturation predicts cognitive decline. The study of de Tour et al. [23] showed that intraoperative cerebral oxygen nay-Jette desaturation is associated with early and late POCD in elderly patients and that it increases the risk of cognitive dysfunction. Also the study of Colak et al. [24] in the group of patients after coronary artery bypass surgery shows that postoperative cognitive outcome
T. Trafidło et al. / International Journal of Surgery 16 (2015) 23e30
was significantly better in patients with intraoperative cerebral oximetry monitoring. Prolonged rSO2 desaturation is a predictor of cognitive decline and must be avoided. The intraoperative use of NIRS in pediatric heart surgery provided an early warning sign of hemodynamic or metabolic compromise, enabling early and rapid intervention to prevent or reduce the severity of potentially life-threatening complications [25]. There is as yet limited evidence to guide the management of postoperative cognitive losses. Currently the primary action towards POCD reduction has been related with patient-specific perioperative care based on adequate hemodynamic monitoring. Although local hypoperfusion of the prefrontal cortex is influenced by venous pressure, carbon dioxide levels, positioning and autoregulation [26e28] there are studies that showed no correlation between cerebral oximetry and MAP [26]. Other studies show that correlation of MAP and local perfusion of the prefrontal cortex results from the efficiency of the mechanisms of blood flow autoregulation, head position, the metabolic demand of the brain, the presence of hypothermia, the patient's ventilation parameters, the presence of vascular disease, alterations in vascular resistance, vasoactive drugs activity, parameters of cardiac hemodynamic, intraoperative blood loss, fluid therapy, and finally, the effect of the anesthetics alone. All above-mentioned factors make the assessment of the effects of MAP declines on postoperative cognitive losses difficult to quantify clearly and conclusively. Similar conclusions were drawn by Deiner et al. [27] and Closhen et al. [28]. In above context cerebral oximetry is particularly valuable, since it shows regional changes in the capillaries located under the applied sensors. This indicates that simple NIRS monitoring could lead to adequate intervention and better postoperative cognitive performance. 4.1. Strengths and limitations of this study The main strength of this study is the solid identification of the postoperative cognitive state of patients with the use of a comprehensive battery of neurocognitive tests. The study showed correlation between NIRS cerebral oximetry monitoring and the better outcome of the part of the neuropsychological tests. Additionally, neuropsychological performance and its relation to other recovery parameters have rarely been systematically assessed as early after the surgery as in our study. The near infrared spectrometry has recently gained a huge interest. It should be acknowledged that the differences in DST and the NBT results between the group with and without NIRS monitoring are significant (p < 0.05). Our findings are encouraging and indicate the possibility that a simple monitoring procedure can significantly reduce POCD. Howether, since they were based on a sample of modest size, the data do need to be interpreted with some caution. There are also further factors that may influence on the assessment of postoperative cognitive losses: age, history of renal failure, TIA or stroke, gender, cardiac disease, hypertension, current tobacco use. Additionally, the last review by Mashour et al. stated the following perioperative factors: anti-platelet cessation, statin cessation, dysrhythmia (AF), hypotension, anemia, dehydration, hypercoagulable state, myocardial infarction or circulatory failure, b-Blocker initiation [26]. Besides, as other studies proved, the type of assessment algorithm can have significant effects on the depth of patient's recovery qualification [19]. It should be noted that our results were obtained only with the use of INVOS 5100 oximeter and cannot automatically be extrapolated to other devices. Nethertheless the use of any “cerebral oximeter” to gain information about the cerebral oxygen saturation is
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without doubts interesting. Further studies are needed to assess if NIRS can be used as a valuable clinical indicator for cerebral hypoperfusion causing potential neurocognitive side effects. Studies based on a bigger number of active patients may also include the monitoring a depth of anesthesia. Such an approach could facilitate assessment of the impact of the anesthetics alone on postoperative cognitive performance. Therefore the continuation of the observation is planned. 5. Conclusions NIRS cerebral oximetry may be useful in reducing postoperative cognitive complications in patients operated on in the prone positioning. Ethical approval RNN/556/08/KB e approval of the ethics committee at Medical University of Lodz, Poland. Funding We wish to confirm that there has been no significant financial support for this work that could have influenced its outcome. Conflicts of interest The authors declare that there are no known conflicts of interest associated with this publication. Author contribution ski and Authors declare, that Tamara Trafidło, Tomasz Gaszyn Katarzyna Nowakowska-Domagała conducted the work described ski, in the article. All authors e Tamara Trafidło, Wojciech Gaszyn ski, Katarzyna Nowakowska-Domagała planned the Tomasz Gaszyn work. Tamara Trafidło and Katarzyna Nowakowska-Domagała reported data. Tamara Trafidło is responsible for the overall content as guarantor. Data sharing Extra data is available by emailing: tamara.trafi[email protected]. pl. Guarantor Tamara Trafidło is responsible for the overall content as guarantor. Acknowledgments This research was performed at the Norbert Barlicki Memorial Teaching Hospital No. 1 in Lodz, Poland, at the Clinical Department of Neurosurgery and Oncology of the Central Nervous System, Medical University of Lodz. This research was granted by Medical University of Lodz. Project number: 502-03/7-128-03/502-54-004. References [1] M.V. Hansen, Chronobiology, cognitive function and depressive symptoms in surgical patients, Dan. Med. J. 61 (2014). B4914. [2] J. Steinmetz, K.B. Christensen, T. Lund, N. Lohse, L.S. Rasmussen, ISPOCD Group. Long-term consequences of postoperative cognitive dysfunction, Anesthesiology 110 (3) (2009 Mar) 548e555. [3] W. Wang, Y. Wang, H. Wu, L. Lei, S. Xu, X. Shen, X. Guo, R. Shen, X. Xia, Y. Liu,
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T. Trafidło et al. / International Journal of Surgery 16 (2015) 23e30 F. Wang, Postoperative cognitive dysfunction: current developments in mechanism and prevention, Med. Sci. Monit. 20 (2014 Oct 12) 1908e1912. H. Edmonds, Detection and treatment of cerebral hypoxia key to avoiding intraoperative brain injuries, J. Clin. Monit. Comput. 16 (1) (January 2000) 69e74. S. Newman, D.J. Wilkinson, C.F. Royse, Assessment of early cognitive recovery after surgery using the post-operative quality of recovery Scale, Acta Anaesthesiol. Scand. 58 (2) (2014 Feb) 185e191. H.K. Fong, L.P. Sands, J.M. Leung, The role of postoperative analgesia in delirium and cognitive decline in elderly patients: a systematic review, Anesth. Analg. 102 (2006) 1255e1266. B. Saniova, M. Drobny, M. Sulaj, Delirium and postoperative cognitive dysfunction after general anesthesia, Med. Sci. Monit. 15 (5) (2009) CS81e87. S. Deiner, J.H. Silverstein, Postoperative delirium and cognitive dysfunction, Br. J. Anaesth. 103 (Suppl. 1) (2009 Dec) i41e46. J. Bruhn, P.S. Myles, R. Sneyd, M.M. Struys, Depth of anaesthesia monitoring: what's available, what's validated and what's next? Br. J. Anaesth. 97 (1) (2006 Jul) 85e94. Epub 2006 Jun 2. Review. D.D. Rani, S. Harsoor, Depth of general anaesthesia monitors, Indian J. Anaesth. 56 (5) (2012) 437e441. F.M. Radtke, M. Franck, J. Lendner, S. Krüger, K.D. Wernecke, C.D. Spies, Monitoring depth of anaesthesia in a randomized trial decreases the rate of postoperative delirium but not postoperative cognitive dysfunction, Br. J. Anaesth. 110 (Suppl. 1) (2013) i98e105. T.L. Tsai, L.P. Sands, J.M. Leung, An Update on Postoperative Cognitive Dysfunction Advances in Anesthesia 28(1), 2010, pp. 269e284. C. Bodolea, N. Hagau, I. Coman, Postoperative cognitive dysfunction in elderly patients. An integrated psychological and medical approach, J. Cognit. Behav. Psychother. 8 (1) (2008) 117e132. A. Bowyer, J. Jakobsson, O. Ljungqvist, C. Royse, A review of the scope and measurement of postoperative quality of recovery, Anaesthesia 69 (11) (2014 Nov) 1266e1278. H. Edgcombe, K. Carter, S. Yarrow, Anaesthesia in the prone position, Br. J. Anaesth. 100 (2) (2008) 165e183. J. Murkin, M. Arango, Near-infrared spectroscopy as an index of brain and tissue oxygenation, Br. J. Anaesth. (2009) 103. A. Denault, A. Deschamps, J. Murkin, A proposed algorithm for the intraoperative use of cerebral near-infrared spectroscopy, Semin. Cardiothorac. Vasc. Anesth. 11 (2007) 274.
[18] J.T. Moller, P. Cluitmans, L.S. Rasmussen, et al., Long-term postoperative cognitive dysfunction in the elderly ISPOCD1 study, Lancet 351 (1998) 857e861. n-Stomberg, J. Jakobsson, Post[19] M. Lindqvist, C. Royse, M. Brattwall, M. Warre operative quality of recovery scale: the impact of assessment method on cognitive recovery, Acta Anaesthesiol. Scand. 57 (10) (2013 Nov) 1308e1312. [20] A.L. Shroyer, L.P. Coombs, E.D. Peterson, M.C. Eiken, E.R. DeLong, A. Chen, T.B. Ferguson Jr., F.L. Grover, F.H. Edwards, The society of thoracic Surgeons: 30-day operative mortality and morbidity risk models, Ann. Thorac. Surg. 75 (6) (2003) 1856e1864 discussion 1864e1865. [21] A. Casati, G. Fanelli, P. Pietropaoli, R. Proietti, R. Tufano, G. Danelli, G. Fierro, G. De Cosmo, G. Servillo, Continuous monitoring of cerebral oxygen saturation in elderly patients undergoing major abdominal surgery minimizes brain exposure to potential hypoxia, Anesth. Analg. 101 (3) (2005) 740e747. [22] J.P. Slater, T. Guarino, J. Stack, K. Vinod, R.T. Bustami, J.M. Brown 3rd, A.L. Rodriguez, C.J. Magovern, T. Zaubler, K. Freundlich, G.V. Parr, Cerebral oxygen desaturation predicts cognitive decline and longer hospital stay after cardiac surgery, Ann. Thorac. Surg. 87 (1) (2009 Jan) 44e45, 36-44; discussion. , G. Dupuis, L. Bherer, A. Deschamps, R. Cartier, A. Denault, [23] E. de Tournay-Jette The relationship between cerebral oxygen saturation changes and postoperative cognitive dysfunction in elderly patients after coronary artery bypass graft surgery, J. Cardiothorac. Vasc. Anesth. 25 (1) (2011 Feb) 95e104. [24] Z. Colak, M. Borojevic, A. Bogovic, V. Ivancan, B. Biocina, V. Majeric-Kogler, Influence of intraoperative cerebral oximetry monitoring on neurocognitive function after coronary artery bypass surgery: a randomized, prospective study, Eur. J. Cardiothorac. Surg 47 (3) (2015 Mar) 447e454. [25] J.L. Zulueta, V.L. Vida, E. Perisinotto, D. Pittarello, G. Stellin, Role of intraoperative regional oxygen saturation using near infrared spectroscopy in the prediction of low output syndrome after pediatric heart surgery, J. Card. Surg. 28 (4) (2013 Jul) 446e452. [26] G. Mashour, D. Woodrum, M. Avidan, Neurological complications of surgery and anaesthesia, Br. J. Anaesth. 114 (2) (2015) 194e203. [27] S. Deiner, I. Chu, M. Mahanian, H.M. Lin, A.C. Hecht, J.H. Silverstein, Prone position is associated with mild cerebral oxygen desaturation in elderly surgical patients, PLoS One 9 (9) (2014 Sep 12). [28] D. Closhen, K.U. Klein, Werner Ch, P. Schramm, K. Engelhard, Changes in cerebral oxygenation induced by prone position, Anesthesiol. ASA Abstr. (2011). A1250.
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International Journal of Surgery journal homepage: www.journal-surgery.net
Original research
Intraoperative monitoring of cerebral NIRS oximetry leads to better postoperative cognitive performance: A pilot study ski a, Wojciech Gaszyn ski a, Tamara Trafidło a, Tomasz Gaszyn Katarzyna Nowakowska-Domagała b, * a b
skiego 22, Poland Department of Anaesthesiology and Intensive Therapy, Medical University of Lodz, PL 91-153 Lodz, ul. Kopcin Department of Psychosocial Rehabilitation, Medical University of Lodz, Lodz 90-647, 1 Hallera Sq. Building 7, Room 108, Poland
h i g h l i g h t s We use NIRS intraoperative monitoring to prevent incidents of brain desaturations. NIRS monitoring leads to better postoperative cognitive performance. NIRS may be useful in reducing POCD in patients operated on in the prone position.
a r t i c l e i n f o
a b s t r a c t
Article history: Received 10 August 2014 Received in revised form 4 February 2015 Accepted 12 February 2015 Available online 18 February 2015
Objectives: The aim of this study is the assessment of the regional cerebral oximetry e NIRS (near infrared spectroscopy) as an intraoperative monitoring system to protect the patient against the incidents of brain desaturations. We hypothesize that patients monitored with NIRS present a smaller range of postoperative cognitive dysfunctions (POCD) in comparison with those without NIRS monitoring during lumbar spine surgery in a prone position. Settings: This study was performed at the Clinical Department of Neurosurgery and Oncology of the Central Nervous System, Medical University of Lodz, Poland. Participants: The study completed 43 adult patients qualified for the surgical treatment of lumbar spondylosis. Before the procedures they were randomized into two subgroups: one monitored intraoperatively by means of NIRS cerebral oximetry (INVOS 5100), which numbered 13 patients e 30.2% (13 NIRS devices were made available to the authors) and the other without NIRS intraoperative monitoring, totaling 30 people e 69.8%. The patients who presented a history of psychiatric, neurological and cardiovascular disorders which impair cognitive processes were disqualified from the study. Primary and secondary outcome measures: A comprehensive battery of neuropsychological tests was preoperatively performed on all patients. The subjects were then divided into two groups: with and without NIRS monitoring. Both groups were statistically homogeneous. Computerized anesthesia records were used to obtain intraoperative data: mean arterial pressure, heart rate, pulsoximetry and cerebral regional oxygenation. The depth of anesthesia monitor was not used. Besides, all the patients passed the same battery of neurocognitive tests 7 days and 1 month postoperatively. The ManneWhitney test was performed to compare POCD and therefore assess the usefulness of NIRS as a monitoring mechanism during anesthesia in the prone position. Results: There was a significant (p < 0.05) difference in the presence of cognitive deficiencies between the subgroup monitored with NIRS and the subgroup without NIRS. It included: Digit Span Test overall score and forward repetition score 7 days after operation, N- back Test results after 30 days in version 0 “back” e time, N-back Test version 1 “back” results in the number of correct answers and the number of errors.
Keywords: Brain tissue oxygen monitoring Near infrared spectroscopy Prone position Postoperative cognitive dysfunctions (POCD)
* Corresponding author. E-mail addresses: tamara.trafi[email protected] (T. Trafidło), tomasz.gaszynski@ ski), [email protected] (W. Gaszyn ski), umed.lodz.pl (T. Gaszyn [email protected] (K. Nowakowska-Domagała). http://dx.doi.org/10.1016/j.ijsu.2015.02.009 1743-9191/© 2015 Surgical Associates Ltd. Published by Elsevier Ltd. All rights reserved.
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Conclusions: NIRS cerebral oximetry may be useful in reducing postoperative cognitive complications in patients operated on in the prone positioning. Trial registration: RNN/556/08/KB e approval of the ethics committee at Medical University of Lodz, Poland. © 2015 Surgical Associates Ltd. Published by Elsevier Ltd. All rights reserved.
1. Introduction Postoperative cognitive dysfunction (POCD) is a subtle disorder of thought processes, which may influence isolated domains of cognition such as executive functions, verbal and visual memory, language abilities, visuospatial abstraction, attention and concentration [1e3]. Research in the area of POCD reduction and improvement of clinical anesthesia to facilitate cognitive recovery is a high priority in the contemporary anesthesia. The undetected intraoperative incidents of the prefrontal cortex desaturation contribute to the development of cognitive dysfunctions disrupting cognitive performance of patients after the surgery [4,5]. Another early postoperative side effects such as emergence agitation and emergence delirium (possibly connected with desaturation) are resource consuming and may cause serious complications [6e8]. The EEG based depth-of-anesthesia monitors facilitating titration of depth of anesthesia and thus possibly reducing the risk of a too deep anesthesia and subsequent decrease in systemic blood pressure and potentially cerebral perfusion has been shown to have a possible positive effect [9e11]. Simultaneously the monitoring of oxygen saturation in the prefrontal cortex is not yet a routine. Therefore, the hypothesis that monitoring of cerebral oxygenation could improve postoperative cognitive recovery and reduce risk of cognitive side effects is worth of empirical investigation. The aim of this study is to assess the value of the cerebral oximetry monitor (NIRS, near infrared spectroscopy) in detecting and diminishing intraoperative episodes of desaturation of the prefrontal cortex in patients operated on in the prone position due to lumbar spondylosis. It has been analyzed whether there is any correlation between the reduction of intraoperative episodes of desaturation of the prefrontal cortex detected by the NIRS cerebral oximetry and postoperative level of neurocognitive performance in patients operated on in the prone orientation. 2. Methods 2.1. Subgroups of patients After obtaining the approval of the Bioethics Committee (RNN/ 556/08/KB), all 43 adult patients qualified for the surgical treatment of lumbar spondylosis in the Clinical Department of Neurosurgery and Oncology of the Central Nervous System, Medical University of Lodz, Poland in the year 2012, were included in the study. The surgical procedures were performed in the prone positioning and included laminectomy, hemilaminectomy and discectomy within the lumbar spine. Before the procedures the patients were randomized into two subgroups: one monitored intraoperatively by means of NIRS cerebral oximetry (INVOS 5100, Somanetics Corporation, USA), which numbered 13 patients (30.2%) and the other without such monitoring (30 patients 69.8%). The total number of the monitored patients in this pilot study is a result of the temporal limitation and shortage of NIRS sensors. The total number of patients is accidental. Fisher's exact test (p > 0.05) showed no differences between
two subgroups in terms of the participation of women and men, age, years of education, the participation of smokers, the presence of cardiovascular diseases, the presence of the symptoms of depression measured by the Beck Depression Inventory (BDI) or duration of anesthesia. The two groups also did not differ significantly (p > 0.05) in the terms of: atrial fibrillation, cardiac arrhythmias, valvular diseases and the use of pharmacological treatment for the above reasons presence of diabetes, hypertension and antihypertensive therapy, hyperlipidemia and the presence of hypolipemic therapy. 2.2. Exclusion criteria The patients with a history of neurological and psychiatric disorders which impair cognitive processes were disqualified from the study. These include previously established dementia, stroke, schizophrenia and depression. The individuals undergoing or with a history of treatment with hypnotics, antidepressants, anxiolytics and steroids were also excluded from the study. Also those, who reported frequent alcohol consumption (above 50 g per day) and whose preoperative laboratory tests showed elevated GGT (gamma-glutamyl transpeptidase) and macrocytosis with hyperchromia were disqualified. The efficiency of cognitive processes is also affected by the coexistence of cardiovascular disease, smoking and depressed mood. Comparative analysis of the breakdown of tobacco smokers and of individuals with symptoms of depression according to Beck Depression Inventory (BDI) gave similar test results. In those cases, the Fischer test revealed no significant difference between the subgroup monitored with NIRS cerebral oximetry and the one without NIRS (p > 0.05). 2.3. The battery of neuropsychological tests The prefrontal cortex, where a local measurement of NIRS takes place, is the anatomical location of working memory structures, which lie at the basis of executive functions. Its image is not uniform and includes various operational stages, such as planning, initiating and monitoring progress. Therefore, in the evaluation of postoperative cognitive deficiencies a battery of tests must be employed. All trial patients were subject to presurgical neuropsychological examinations in the form of a battery of tests such as visual working memory N-back Test (NBT), Trail Making Test A & B, (TMT A & B), Stroop Color-Word Interference Test Part 1 and 2 (Stroop 1 & 2), Verbal Fluency Test (FAS), Digit Span Test e forward and backward repetition of numbers (DST) and the Mini Mental State Examination (MMSE) [12,13]. The preoperative test results were the basis for the assessment of postoperative cognitive dysfunctions in the entire sample of the patients tested. Re-evaluation of cognitive processes with the same tests was made at 7 and 30 days after the operation. All the participants completed all the tests (there were no missing data). The present study compared cognitive deficiencies between the group supervised with NIRS and the one without such monitoring. Description of the test sequence is shown in Fig. 1. It is assumed that
T. Trafidło et al. / International Journal of Surgery 16 (2015) 23e30
25
Fig. 1. Description of the a battery of tests employed in the evaluation of postoperative cognitive deficiencies.
20% deterioration in repeated neuropsychological acknowledged as cognitive loss [13,14].
tests
is
2.4. Intraoperative conditions Both groups of patients were subjected to anesthesia by entirely intravenous route: propofol 4e10 mg/kg (Propofol, Fresenius Kabi, Germany), remifentanil 0.05e0.10 mg/kg bw (Ultiva, Glaxo Smith Kline, UK), atracurium 0.6 mg/kg (Tracrium, Glaxo Smith Kline, UK). Additionally, each patient was ventilated in CMV mode, FiO2 ¼ 0.50, Vt ¼ 8 ml/kg, respiratory rate - 10/min, normocapnia (pCO2 from 35 to 45 mmHg). After administering anesthesia, the patients were placed in the prone position. Detailed description of this procedure can be found at Edgcombe et al. [15]. Upon the completion of the neurosurgery the patient was again placed in the supine position. The main objective of intraoperative care of the patient during a surgical treatment of lumbar spondylosis is to maintain a normal level of mean arterial pressure (MAP), normocardia and normal ranges of pulse oximetry saturation. Furthermore, in the one of the observed groups, monitoring of cerebral oximetry complemented the standard routine of intraoperative hemodynamic monitoring. In the presented study cerebral oximetry monitoring with INVOS 5100 was employed. In the case of cerebral oximetry, NIR penetration depth is specifically selected in such a way as to bypass the scalp and skull. Based on the differences in absorption, the monitor determines local variations of oxygenated hemoglobin in the tissue capillaries located in the prefrontal cortex [16,17]. NIRS cerebral oximetry reading occurs in real-time, continuously. The onset of the bilateral oximetry measurement in the group of patients monitored with NIRS took place 15 min prior to the induction of anesthesia. A downward tendency of ScrO2 oximetry index (cerebral regional oxygen saturation) by more than 20% from the baseline may be a manifestation of a significant tissue hypoxia [16,17]. The measured values of ScrO2 at the output in INVOS 5100 most frequently
oscillated above 70 units. The definition of significant changes in ScrO2 for interventions was the decline below 40 units, what was considered as an indicator of deep hypoxic CNS. A careful consideration is recommended whenever deliberate hypotension is requested by the surgeon. The observers kept mean arterial pressure above 65 mm Hg. In the present study, intraoperative decreases in values of cerebral oximetry, MAP and pulse oximetry saturation were recorded and statistically analyzed. The number of intraoperative interventions which improve hemodynamic conditions was counted and compared between the two subgroups. Consequently, interventions were introduced in the patients without the NIRS monitoring at the time of changes in parameters: MAP, HR above the range of 60e100/min, SpO2 below 95%. Whereas in the group of patients monitored with NIRS interventions enhancing cerebral oxygen saturation were based additionally on the declines in the value of ScrO2. Detailed parameters set by investigators which instigated intervention are presented in (Fig. 2) which was designed on the basis of the algorithm in the use of brain oximetry proposed by Denault et al.[17]. Observers were not blinded, as the use of NIRS monitoring is non-invasive and does not alter procedures for conducting anesthesia. Besides, the amount of interventions which were taken in the group supervised with NIRS and in the group without such monitoring was additionally observed. It required active observations of NIRS monitor by the investigator. INVOS 5100 records values of ScrO2 in Windows Excel sheets or in the form of Excel graphics. HR and SpO2 parameters were recorded using Datex Ohmeda GE Healthcare printer configured with Cardiocap monitor which is used for routine intraoperative monitoring. The course of anesthesia together with moments of interventions were recorded in protocols of routine anesthesia. Episode of each intervention was also recorded in the files of the INVOS 5100. Intraoperative interventions occurred simple and no
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T. Trafidło et al. / International Journal of Surgery 16 (2015) 23e30
Fig. 2. Algorithm of procedures applied in the decline in the value of NIRS cerebral oximetry. ScrO2 e local saturation of the cerebral cortex; MAP e mean arterial pressure; SaO2 e oxygen saturation of arterial blood; Hb e hemoglobin; CO e cardiac output; ScvO2 e central venous oxygen saturation; CMRO2 e cerebral metabolic rate of oxygen; ICP e intracranial pressure.
constrictors were used. They focused mainly on improving the head positioning whenever ScrO2 declined by 20% from the baseline. When SpO2 declines were noted, observers improved the orientation of pulse oximeter sensor. If this intervention was not effective the increase of FiO2 took place. When the changes of MAP ±20% of baseline were found, the observers suited the supply of drug intravenous infusion (totally intravenous anesthesia) and the insertion of fluid volume. The total fluid loading during the anesthesia course was 4 ml/kg/hr. In the group of the observed patients there was no need for further cardiovascular support in the form of catecholamines or ephedra. During episodes of bradycardia (HR < 60/min) adequate doses of atropine were given and the depth of anesthesia was reduced. Before arousal from anesthesia all
patients were administered Ketoprofen. Support during the early and intermediate postoperative course was standardized at the Clinical Department of Neurosurgery and Oncology of the Central Nervous System, Medical University of Lodz, Poland. The goal of postoperative pain management was achieved through the supply of Ketoprofen and Paracetamol. No COX-2 inhibitors were used. The patients did not require postoperative supply of steroids or opioids. No local anesthesia was used. No blood loss requiring transfusion occurred. Thromboprophylaxis consisted in the use of adequate doses of low molecular weight heparin (enoxaparin).
T. Trafidło et al. / International Journal of Surgery 16 (2015) 23e30
3. Results
27
Table 2 Results of ManneWhitney U test for variables in the subgroups.
Statistics of measurable parameters in both subgroups e one monitored with cerebral oximetry and the other without monitoring e are presented in Table 1. Comparative analysis of the values of measurable parameters in both subgroups showed no statistically significant differences for the time of anesthesia, age and years of education (p > 0.05). However, a significant difference (p < 0.05) occurred for both subgroups in the quantities of intraoperative interventions which improve hemodynamic conditions. More interventions occurred in the group without NIRS monitoring. Values of probability for the ManneWhitney U test are demonstrated in Table 2. The statistical analyses of the declines in the intraoperative cerebral oximetry and MAP are presented in Table 3. In some patients, the Pearson correlation coefficient demonstrated a positive correlation between the increase in ScrO2 parameters and the increase of MAP (Fig. 3). This relationship is consistent with the generally acknowledged fact of the cerebral perfusion improvement during an increase in mean arterial pressure. However, the rest of the patients showed no significant relationships for NIRS and MAP. In some cases, declines in NIRS parameters occurred at constant MAP readings (Fig. 4). Therefore, it can be assumed that additional factors, such as excessive tilt of the head of the examined patient must have been involved. Such positioning may affect perfusion and the outflow of blood from the head, despite normal readings of cardiovascular blood circulation parameters. In each of these cases readjustment of the head positioning increased NIRS oximetry readings. In the remaining patients a constant level of NIRS readings was registered with declines in MAP (Figs. 5 and 6). This can be explained by effective mechanisms of autoregulation of cerebral blood flow. In addition, when declines in the values of NIRS readings took place, parameters of SpO2 and HR remained within normal ranges and did not undergo any reduction (Fig. 4). Apart from that, correlative dependence between SpO2 and the values of ScrO2 occurred only in the case of three patients. Then the ScrO2 and SpO2 showed almost no deviation from the normal value. No case of a dramatic fall in the value of arterial blood saturation (SpO2) in the cardiovascular circulation was reported in the entire study sample. The non-parametric ManneWhitney test was used to make a comparison of average values of the cognitive tests. Statistically significant (p < 0.05) difference in the presence of cognitive deficiencies between the subgroup monitored with NIRS and the subgroup without NIRS include: DST overall score and forward repetition score 7 days after operation, NBT results after 30 days in version 0 “back” e time and the results in the NBT version 1 “back” in the number of correct answers and errors. Significant results of ManneWhitney test for differences in cognitive tests in the group with and without NIRS are presented in Table 4. The performance
Parameter
Test U statistics
Normalized statistics
P level
Anesthesia time [min] Number of interventions Age Years of education
177.0000 52.5000 180.5000 184.0000
0.243689 3.549894 0.148921 0.054153
0.807472 0.000385 0.881616 0.956813
Table 3 Characteristics of significant declines in ScrO2 in the group monitored with NIRS. The correlation between cerebral oximetry values and the values of MAP (Pearson's correlation coefficient). Patient number
Number of episodes of ScrO2 reduction
Total duration of episodes of ScrO2 reduction
Number of episodes of MAP reduction
Correlation between NIRS and MAP
1 2 3
0 0 5 (1 unilaterally, 4 on both sides) 0 7 (unilaterally) 10 (both sides) 0 3 (both sides) 0 3 (unilaterally) 1 (both sides) 3 (unilaterally) 0
e e 20 min
4 0 11
Yes No Yes
e 30 min
7 5
No Yes
40 min
7
Yes
e 10 min
5 4
No No
e 10 min
6 36
Yes No
5 min
2
Yes
10 min
10
No
0
Yes
4 5 6 7 8 9 10 11 12 13
e
level of other neuropsychological tests between the subgroups was unchanged. 4. Discussion Assessment of cognitive performance is not a standard element of existing quality of recovery scales. Nevertheless in our opinion the preservation of the patients' quality of life which is certainly influenced by the level of cognitive functioning is of particular importance. There is indeed no full consensus around the definition, the explicit limit, change/decline that defines POCD. The International Study of Postoperative Cognitive Dysfunction (ISPOCD) group used an extensive test battery and used explicit changes where postoperative cognitive function is assessed in isolation from assessment of other recovery domains. Likewise the Postoperative
Table 1 Basic statistics for the measurable variables in the subgroups investigated. Group
Parameter
N
Mean
95% CI
NIRS
Anesthesia time [min] Number of interventons Age Years of education Anesthesia time [min] Number of interventons Age Years of education
12 12 12 12 31 30 31 31
188.75 2.66 50.58 12.25 196.29 7.23 49.22 12.16
143.05 0.59 40.32 11.00 170.44 5.99 44.12 10.83
Without NIRS
234.44 4.73 60.84 13.49 222.14 8.47 54.32 13.49
Median
Minimum
Maximum
Q1
Q3
SD
185.00 2.00 49.50 12.00 185.00 6.00 53.00 12.00
105.00 0.00 30.00 10.00 95.00 3.00 25.00 10.00
380.00 10.0 87.00 17.00 330.00 15.00 69.00 20.00
145.00 0.00 38.50 11.00 150.00 5.00 36.00 11.00
207.50 4.00 58.50 12.50 235.00 10.00 62.00 14.00
71.92 3.25 16.14 1.95 70.47 3.31 13.89 3.62
N e the number of patients, 95% CI e the end of the confidence interval for the mean in the population upon accepting a confidence level of 0.95, Q1 e the lower quartile, Q2 e the upper quartile value, SD e standard deviation.
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T. Trafidło et al. / International Journal of Surgery 16 (2015) 23e30
Fig. 3. Graph of MAP (mean arterial pressure), NIRS1 and NIRS2 (near infrared spectroscopy e cerebral oxygen saturation) correlations in a 32 year e old woman participating in the study. A positive correlation between the recorded parameters was detected.
Fig. 6. Graph of MAP (mean arterial pressure), NIRS1 and NIRS2 (near infrared spectroscopy e cerebral oxygen saturation) correlations in a 29 year e old woman participating in the study. The arrow indicates the decrease in MAP during which no declines in the value of NIRS were detected.
Table 4 Results of ManneWhitney test for differences in cognitive test results in the group with and without NIRS. Significant differences in Test U Normalized P level the tests results statistics statistics DST overall e after 7 days DST forward e after 7 days NBT 0 back e time after 30 days NBT 1 back e number of correct answers after 30 days NBT 1 bac e number of wrong answers after 30 days Fig. 4. Graph of MAP (mean arterial pressure), SpO2 (systemic pulse oximetry saturation), NIRS1 and NIRS2 (near infrared spectroscopy e cerebral oxygen saturation) correlations in a 60 year-old woman participating in the study. No positive correlation between the recorded parameters was detected. The arrow indicates unilateral decreases in the value of NIRS2 despite increases in MAP. SpO2 values remain unchanged, despite the fluctuations in the value of NIRS.
Fig. 5. Graph of MAP (mean arterial pressure), NIRS1 and NIRS2 (near infrared spectroscopy e cerebral oxygen saturation) correlations in a 60 year e old man participating in the study. The arrow indicates the decrease in MAP with no decreases detected in the value of NIRS.
Quality of Recovery Scale that includes cognitive tests is a useful tool for assessment of postoperative cognitive recovery [18,19]. Our study emphasize the clinical importance of NIRS and its impact on the postoperative rehabilitation, patient's quality of life
N (without N (NIRS NIRS) group)
77,0000 2,95134
0,003164 31
12
82,5000 2,80242
0,005072 31
12
84,0000 2,47454
0,013341 31
11
69,0000 2,90366
0,003689 31
11
69,0000 2,90366
0,003689 31
11
and therapy cost effectiveness. The significance of intraoperative desaturation is supported by the findings of Shroyer et al. [20] which showed that postoperative problems caused by desaturation include delirium (incidence 10e60 %) and POCD (incidence 24e53 %) which lead to a longer hospital length of stay. Furthermore the existing literature demonstrates that cognitive dysfunctions after noncardiac surgery were associated with increased mortality, risk of leaving the labor market prematurely, dependency on social transfer over longer term follow-up [2]. We showed that cerebral oximetry intraoperative monitoring reduces postoperative cognitive decline and leads to better postoperative cognitive performance measured by the Digits Span Test and N-back test because a pragmatic intervention to optimize cerebral oxygenation triggered by the NIRS monitoring conferred a significant reduction in postoperative cognitive impairment. Although few studies have specifically investigated the effect of intraoperative NIRS monitoring on the postoperative cognitive performance decline, our results are consistent with the existing literature. In particular they are supported by the findings of: Casati et al. [21] which showed that less cognitive decline was observed among patients where cerebral hypoxia was prevented by adequate monitoring and Slater et al. [22] which showed that cerebral oxygen desaturation predicts cognitive decline. The study of de Tour et al. [23] showed that intraoperative cerebral oxygen nay-Jette desaturation is associated with early and late POCD in elderly patients and that it increases the risk of cognitive dysfunction. Also the study of Colak et al. [24] in the group of patients after coronary artery bypass surgery shows that postoperative cognitive outcome
T. Trafidło et al. / International Journal of Surgery 16 (2015) 23e30
was significantly better in patients with intraoperative cerebral oximetry monitoring. Prolonged rSO2 desaturation is a predictor of cognitive decline and must be avoided. The intraoperative use of NIRS in pediatric heart surgery provided an early warning sign of hemodynamic or metabolic compromise, enabling early and rapid intervention to prevent or reduce the severity of potentially life-threatening complications [25]. There is as yet limited evidence to guide the management of postoperative cognitive losses. Currently the primary action towards POCD reduction has been related with patient-specific perioperative care based on adequate hemodynamic monitoring. Although local hypoperfusion of the prefrontal cortex is influenced by venous pressure, carbon dioxide levels, positioning and autoregulation [26e28] there are studies that showed no correlation between cerebral oximetry and MAP [26]. Other studies show that correlation of MAP and local perfusion of the prefrontal cortex results from the efficiency of the mechanisms of blood flow autoregulation, head position, the metabolic demand of the brain, the presence of hypothermia, the patient's ventilation parameters, the presence of vascular disease, alterations in vascular resistance, vasoactive drugs activity, parameters of cardiac hemodynamic, intraoperative blood loss, fluid therapy, and finally, the effect of the anesthetics alone. All above-mentioned factors make the assessment of the effects of MAP declines on postoperative cognitive losses difficult to quantify clearly and conclusively. Similar conclusions were drawn by Deiner et al. [27] and Closhen et al. [28]. In above context cerebral oximetry is particularly valuable, since it shows regional changes in the capillaries located under the applied sensors. This indicates that simple NIRS monitoring could lead to adequate intervention and better postoperative cognitive performance. 4.1. Strengths and limitations of this study The main strength of this study is the solid identification of the postoperative cognitive state of patients with the use of a comprehensive battery of neurocognitive tests. The study showed correlation between NIRS cerebral oximetry monitoring and the better outcome of the part of the neuropsychological tests. Additionally, neuropsychological performance and its relation to other recovery parameters have rarely been systematically assessed as early after the surgery as in our study. The near infrared spectrometry has recently gained a huge interest. It should be acknowledged that the differences in DST and the NBT results between the group with and without NIRS monitoring are significant (p < 0.05). Our findings are encouraging and indicate the possibility that a simple monitoring procedure can significantly reduce POCD. Howether, since they were based on a sample of modest size, the data do need to be interpreted with some caution. There are also further factors that may influence on the assessment of postoperative cognitive losses: age, history of renal failure, TIA or stroke, gender, cardiac disease, hypertension, current tobacco use. Additionally, the last review by Mashour et al. stated the following perioperative factors: anti-platelet cessation, statin cessation, dysrhythmia (AF), hypotension, anemia, dehydration, hypercoagulable state, myocardial infarction or circulatory failure, b-Blocker initiation [26]. Besides, as other studies proved, the type of assessment algorithm can have significant effects on the depth of patient's recovery qualification [19]. It should be noted that our results were obtained only with the use of INVOS 5100 oximeter and cannot automatically be extrapolated to other devices. Nethertheless the use of any “cerebral oximeter” to gain information about the cerebral oxygen saturation is
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without doubts interesting. Further studies are needed to assess if NIRS can be used as a valuable clinical indicator for cerebral hypoperfusion causing potential neurocognitive side effects. Studies based on a bigger number of active patients may also include the monitoring a depth of anesthesia. Such an approach could facilitate assessment of the impact of the anesthetics alone on postoperative cognitive performance. Therefore the continuation of the observation is planned. 5. Conclusions NIRS cerebral oximetry may be useful in reducing postoperative cognitive complications in patients operated on in the prone positioning. Ethical approval RNN/556/08/KB e approval of the ethics committee at Medical University of Lodz, Poland. Funding We wish to confirm that there has been no significant financial support for this work that could have influenced its outcome. Conflicts of interest The authors declare that there are no known conflicts of interest associated with this publication. Author contribution ski and Authors declare, that Tamara Trafidło, Tomasz Gaszyn Katarzyna Nowakowska-Domagała conducted the work described ski, in the article. All authors e Tamara Trafidło, Wojciech Gaszyn ski, Katarzyna Nowakowska-Domagała planned the Tomasz Gaszyn work. Tamara Trafidło and Katarzyna Nowakowska-Domagała reported data. Tamara Trafidło is responsible for the overall content as guarantor. Data sharing Extra data is available by emailing: tamara.trafi[email protected]. pl. Guarantor Tamara Trafidło is responsible for the overall content as guarantor. Acknowledgments This research was performed at the Norbert Barlicki Memorial Teaching Hospital No. 1 in Lodz, Poland, at the Clinical Department of Neurosurgery and Oncology of the Central Nervous System, Medical University of Lodz. This research was granted by Medical University of Lodz. Project number: 502-03/7-128-03/502-54-004. References [1] M.V. Hansen, Chronobiology, cognitive function and depressive symptoms in surgical patients, Dan. Med. J. 61 (2014). B4914. [2] J. Steinmetz, K.B. Christensen, T. Lund, N. Lohse, L.S. Rasmussen, ISPOCD Group. Long-term consequences of postoperative cognitive dysfunction, Anesthesiology 110 (3) (2009 Mar) 548e555. [3] W. Wang, Y. Wang, H. Wu, L. Lei, S. Xu, X. Shen, X. Guo, R. Shen, X. Xia, Y. Liu,
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