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EURO-8507; No. of Pages 4 European Journal of Obstetrics & Gynecology and Reproductive Biology xxx (2014) xxx–xxx
Contents lists available at ScienceDirect
European Journal of Obstetrics & Gynecology and Reproductive Biology journal homepage: www.elsevier.com/locate/ejogrb
Steep Trendelenburg position during robotic sacrocolpopexy and heart rate variability Lior Lowenstein a,1,*, Mona Mustafa a,1, Yechiel Z. Burke a, Susana Mustafa a, Dror Segal b, Amir Weissman a a Department of Obstetrics and Gynecology, Rambam Medical Center, Ruth and Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel b Department of Anesthesiology, Rambam Medical Center, Ruth and Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
A R T I C L E I N F O
A B S T R A C T
Article history: Received 9 December 2013 Received in revised form 20 January 2014 Accepted 31 March 2014
Objectives: The objective of this study was to evaluate heart rate variability and hemodynamic parameters following steep Trendelenburg positioning during robotic sacrocolpopexy. Study design: For 19 women, median age 57 (range: 45–72), blood pressure and ECG were recorded during surgery. From the ECG signals interbeat intervals were used to assess heart rate variability, analyzed in time and frequency domains using the Fast Fourier transform. The low frequency and high frequency spectral bands were used to assess sympathetic and parasympathetic pathways respectively. Results: All women underwent robotic supracervical hysterectomy and sacrocolpopexy. A statistically significant decrease in the mean values of the low-frequency and high-frequency spectral bands, representing sympathetic and parasympathetic activity, respectively were demonstrated 5 min following Trendelenburg positioning of the patients (from 3.6 1.4 to 2.9 0.8 ms2/Hz, and from 3.5 1.4 to 2.9 1 ms2/Hz, P < 0.05). These changes correlated with a mean 20% decrease in heart rate, which lasted for 30 min, and with a second drop in sympathetic and parasympathetic activity and heart rate, commencing 2 h from the start of surgery, and lasting until the end of the operation. Conclusions: Steep Tredelenburg positioning during robotic urogynecology surgery results in significant changes in the autonomic nervous system modulation of heart rate variability and in other hemodynamic parameters. ß 2014 Elsevier Ireland Ltd. All rights reserved.
Keywords: Robotic surgery Urogynecology Autonomic nervous system Trendelenburg Heart rate variability
1. Introduction Sacrocolpopexy can be performed through different routes – abdominal, laparoscopic or robotic. Over the past decade the robotic approach has become more common. Robotic assisted surgery was approved by the Food and Drug Administration for gynecologic procedures in 2005 based on preliminary evidence of safety and efficacy [1]. The main advantages of robotic surgery are: the tremor reduction system, high definition 3D vision, the option to use three surgical arms under the surgeon’s control and 7 degrees of freedom for wrist movement. The latter enables less experienced laparoscopic surgeons to perform more complex
* Corresponding author. Tel.: +972 4 8542382. E-mail addresses: [email protected], [email protected] (L. Lowenstein). 1 These authors contributed equally to this work.
procedures. These advantages may explain the rapid increase in adoption of da Vinci1 surgery for gynecology [2]. Among the disadvantages of robotic surgery is the difficulty in changing patient’s position during operation. Since the procedures performed by robotic surgery are usually more complex than those performed through other routes, the effect of long lasting Trendelenburg positioning on the cardiovascular and autonomic system needs investigation. Two issues regarding cardiovascular function during robotic surgery are important to patient safety: the steep Trendelenburg position and the induction of pneumoperitoneum during the operation. Both conditions can alter cardiovascular function and may be hazardous in some patients, particularly those with preexisting cardiac or pulmonary disease. Heart rate variability (HRV) is a common tool for the noninvasive investigation of heart rate modulation by the autonomic nervous system (ANS). HRV is modulated by different central and peripheral inputs, and provides a quantitative marker of autonomic activity. Analysis of HRV by power spectral density is an
http://dx.doi.org/10.1016/j.ejogrb.2014.03.046 0301-2115/ß 2014 Elsevier Ireland Ltd. All rights reserved.
Please cite this article in press as: Lowenstein L, et al. Steep Trendelenburg position during robotic sacrocolpopexy and heart rate variability. Eur J Obstet Gynecol (2014), http://dx.doi.org/10.1016/j.ejogrb.2014.03.046
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L. Lowenstein et al. / European Journal of Obstetrics & Gynecology and Reproductive Biology xxx (2014) xxx–xxx
effective means of studying effects of the autonomic nervous system on heart rate, both in healthy and diseased individuals [3,4]. The existence of adequate HRV is considered a factor of cardiovascular health and integrity, while decreased HRV may be associated with illness, aging and increased mortality rates from cardiovascular disease [5] HRV results from the dynamic interplay between the sympathetic and parasympathetic nervous systems. The interbeat intervals (computed from successive R–R intervals) that compose HRV represent instantaneous interactions of the beat-to-beat control mechanisms mediated by the ANS. The vagal activity is thought to be a major component of the high-frequency (HF) spectral band, whereas the origin of the low-frequency (LF) spectral band is more controversial. Some consider it to represent sympathetic modulation, whereas others consider it to include both sympathetic and vagal influences. However, in most reports, LF is used mainly as a representation of the effect of the sympathetic nervous system [6,7] Previous studies evaluating the effect of Trendelenburg positioning during laparoscopic operations on the autonomic system showed inconsistent or even conflicting findings [8]. One study reported marked activation of the autonomic cardiac response [8]; yet another study reported an absence of significant differences in the spectral components of heart rate between the supine and Trendelenburg positions [9]. Moreover, most studies have examined the effects of moderate levels of head-down tilt (usually less than 20 degrees), and the majority focused on the effects of recovery from prolonged periods of head-down bed rest, but not the acute effects of head-down tilt, as encountered in robotic operations [10,11]. The inconsistency of the findings and the increasing use of robotic operations with patients positioned in a steep Trendelenburg prompted us to research this topic. The aim of the current study was therefore to evaluate the modulation of the autonomic nervous system on heart rate variability following Trendelenburg positioning during robotic sacrocolpopexy. 2. Materials and methods The local Research Ethics Institutional Review Committee of Rambam Health Care Campus approved the study protocol. Women who underwent robotic sacrocolpopexy at our tertiarycare referral center were invited to participate in the study. Informed consent was obtained from all participants. Exclusion criteria were: (1) medical disorders that can interfere with the autonomic nervous system (e.g. coronary heart disease, a history of heart failure or other cardiac disease, hypertension, neurological diseases, diabetes or thyroid disease; (2) the use of medications that can interfere with the autonomic nervous system, including beta-receptor agonists or antagonists, anti-arrhythmic agents or antihypertensive drugs, anticholinergic agents or adrenergic alpha-antagonists, tricyclic or serotoninergic antidepressants. 2.1. Surgical procedure Robotic sacrocolpopexy was performed using the da Vinci Surgical System. Following abdominal insufflation with 14 mm of mercury with CO2, we introduced five ports in a shallow ‘‘W’’ formation: one supra umbilical 12-mm port for the laparoscope; one 10-mm port placed sub-coastally lateral to the rectus muscle on the right side, and three 8-mm robotic ports in bilateral lower quadrants, two on the left and one on the right. Prior to docking of the robotic side cart, patients were positioned in steep Trendelenburg (30 degrees). In women with uterovaginal prolapse, we performed a supracervical hysterectomy, with or without bilateral salpingoopherectomy. The decision for salpingoopherectomy was
based on clinical history and patients’ preference. In addition to the sacrocolpopexy, concomitant procedures were performed as indicated: posterior colpoperineorrhaphy, anterior colporrhaphy and midurethral slings for stress urinary incontinence. 2.2. Signal acquisition and processing Three standard surface chest electrodes were fitted to each participant and were used to record the electrocardiogram (ECG) continuously following patient intubation. We entered into the computer all patient-related events, including changes in position. The ECG was recorded through a 12-bit analog/digital data acquisition card (National Instruments, Austin TX) with a sampling frequency of 200 Hz, and stored in a computer for offline studies. The digitized ECG signals were recorded at baseline in the supine position, immediately following the change to the Trendelenburg position, and every 30 min thereafter, until return to the supine position. The data were then processed and analyzed via dedicated robust software to detect the R wave peaks. The R point of each QRS complex was defined and the interval between two consecutive R points (the R–R interval) was computed. All R–R intervals were visually inspected and manually edited, if necessary, to exclude background noise and artifacts. A ‘‘clean’’ 5-min segment (preferably unedited) was used for the analyses. Time and frequency domain analyses were performed as previously described [12]. Briefly, heart rate variability was evaluated in accordance with the guidelines of the Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology [12]. The power spectral bands were quantified by measuring the area under the following frequency bands: lowfrequency (LF) (0.04–0.15 Hz), known to represent a mixture of sympathetic and vagal activity but mainly the sympathetic activity, and high-frequency (HF) (0.15–0.4 Hz), representing parasympathetic activity. Three distinct frequency bands can be distinguished in the power spectrum of the interbeat interval. The HF band corresponds to the effect of respiratory sinus arrhythmia and is controlled by vagal activity, therefore reflecting parasympathetic influences. The LF component of the power spectrum is generally thought to reflect primarily sympathetic, and to a lesser extent, parasympathetic activity. The very low frequency band (VLF) is a less specific indicator of heart rate variability and is thought to be under the control of thermo-regulation, the renin– angiotensin system, and other mediators of low frequency oscillations in heart rate. The instantaneous heart rate represents the net interactions between vagal and sympathetic regulation, the former decreasing heart rate and the latter increasing heart rate. The higher the numbers in the low-frequency spectral band, the higher the sympathetic tone and vice versa. On the contrary, the higher the numbers in the high-frequency spectral band, the higher the parasympathetic tone. Thus, a rise in heart rate can be the consequence of an increase in sympathetic activity, but it may also result from a decrease in vagal regulation or from simultaneous changes in both regulatory systems. Sociodemographic data, preoperative standardized prolapse assessment according to the Pelvic Organ Prolapse Quantification (POP-Q) system [13], medical history including parity, previous pelvic surgery or hysterectomy, concomitant surgical procedures and estimated blood loss and complications during surgery were retrieved from patients’ electronic charts. 2.3. Statistical analysis We used Statgraphics statistical package (StatPoint technologies, Warrenton, VA) for data management and statistical analysis. Descriptive statistics are reported as mean (SD) for continuous
Please cite this article in press as: Lowenstein L, et al. Steep Trendelenburg position during robotic sacrocolpopexy and heart rate variability. Eur J Obstet Gynecol (2014), http://dx.doi.org/10.1016/j.ejogrb.2014.03.046
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variables, median and interquartile range for ordinal variables and number (percentage) for categorical variables. The normality of HRV data was examined using the Kolmogorov–Smirnov statistic. When the normality assumption was violated, data were transformed using logarithmic transformation prior to further statistical analysis. To evaluate the effect of patient position changes on parameters of heart rate variability, ANOVA Models for repeated measures were used. Spearman’s analysis was used to evaluate the correlation between heart rate and autonomic system activity. Group size was calculated by an a priori power analysis aimed at 80% power to allow a difference of 20% at a two-sided significance level of 5% in each of the variables examined. This indicated that a sample size of 17 participants would be adequate. All tests were considered significant at the 0.05 level. 3. Results Nineteen women participated in the study. Their median age was 57 years (range: 45–72) and median BMI 27 kg/m2 (range: 23– 33). In 4 patients (21%), the American Society of Anesthesiologists (ASA) score was 1, and in 15 (79%), the ASA score was 2. All patients underwent subtotal hysterectomy and sacrocervicopexy. A total of 12 underwent additional procedures at the time of the robotic surgery; 6 TVT-O (Gynecare, Johnson & Johnson), 1 anterior colporrhaphy and 7 salpingo-oophorectomy. The median duration of operation was 174 min (range 110–263). None of the procedures required conversion from robotic to laparoscopic or open surgery. Median blood loss during surgery was 38 ml (range: less than 10– 200 ml). Significant decreases in the mean values of both HF and LF spectral densities were documented 5 min following the change to the Trendelenburg position (from 3.6 1.41 to 2.9 0.8 ms2/Hz, and from 3.5 1.4 to 2.9 1 ms2/Hz, respectively, P < 0.05, Table 1). Thereafter, a gradual recovery of both frequency bands was observed. However, a second decrease was recorded at about 2 h from the beginning of the operation, followed by a slow and gradual recovery that persisted until the conclusion of the operation. Concomitant with the initial decrease in the spectral bands, mean heart rate decreased significantly, and then immediately showed a progressive recovery. A second decrease in mean heart rate occurred 2 h after the beginning of surgery (in 15 of the patients [79%]) and continued until the end of the operation (from 82 16 to 66 10 bpm, P < 0.05, Table 1). Immediately following Trendelenburg positioning, abrupt but transient decreases in mean systolic and diastolic blood pressure were observed (from 132 25 to 108 13 mmHg and from 77 12 to 62 11 mmHg, respectively, P < 0.05, Table 1). A gradual process of recovery followed the decrease. 4. Comments Robotic-assisted laparoscopic operations require the application of steep Trendelenburg positioning and the induction of pneumoperitoneum for a relatively prolonged period. Changing a patient’s positioning during an operation requires undocking the robot from the patient, which entails complex manipulations.
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Therefore, in most cases, the patient is left in the initial position for the entire duration of the operation. Our findings show a statistically significant decrease in the activity of both sympathetic and parasympathetic systems following steep Trendelenburg positioning of patients who underwent robotic operations for the repair of pelvic organ prolapse. These changes occurred immediately following steep Trendelenburg positioning. A trend toward returning to baseline activity could be seen 30 min after the beginning of the operation, while a second phase of decrease in the mean power spectral density was demonstrated following a more prolonged Trendelendburg positioning (two hours from surgery). The changes in sympathetic activity correlated with a mean 20% decrease in patients’ heart rate from an average of 82 to 66 beats per minutes, and with a decrease in both systolic and diastolic blood pressure measurements. The initial response to head down tilt is an instantaneous shift in fluids to the thoracic cavity with an increase in central venous pressure [10,11]. This is followed by a rapid increase in stroke volume and cardiac output [14]. The activity of the renin–angiotensin system is reduced [11], while the concentration of atrial natriuretic peptide may be increased [15]. Further to the placement of the patient in a steep head-down tilt, the induction of pneumoperitoneum can cause other significant circulatory perturbations, including decreased venous return, increased systemic vascular resistance and increased mean arterial pressure. These effects may have deleterious effects in patients with preexisting cardiac disease, or in the aged [16]. Autonomic nervous system activity is intimately associated to body position and the level of gravitational strain imposed on the cardiovascular system [14,16]. The baroreflex feedback loop adjusts sympathetic activity to maintain stable blood pressure, despite variations in venous return to the heart. Therefore, sympathetic activity is increased when venous return is low, as when assuming the upright position; whereas it is suppressed when venous return is increased, such as in the head-down tilt. Most studies that have investigated the effects of head-down tilt, examined cardiovascular and autonomic functions in a relatively moderate level of inclination (usually 6–20 degrees), or during prolonged time periods that assumed the head-down tilt, as in space missions of astronauts [17,18]. However, data regarding the acute effects of the autonomic nervous system in steep Trendelenburg (30 degrees), as applied in robotic operations, is very limited. Healthy cardiac function is characterized by irregular time intervals between successive heart beats. This heart rate variability (HRV) results from rhythmic oscillations of the regulatory mechanisms of cardiac activity that maintain heart rate within a constant range and coordinate responses to the continuously changing conditions. HRV primarily emerges through the activity of the two arms of the autonomic nervous system and the additional influences of humoral, neural, thermoregulatory, and other control and feedback mechanisms [19]. HRV has thus emerged as a simple, noninvasive measure that has been explored in a variety of clinical situations. It is now well accepted that the autonomic nervous system and its modulation of HRV plays an important role in physiological, as well as various pathological
Table 1 Changes in heart rate, blood pressure and autonomic variables during robotic sacrocolpopexy.
Low frequency (LF) High frequency (HF) Heart rate (HR) Systolic blood pressure Diastolic blood pressure
Baseline
5 min
30 min
60 min
90 min
120 min
150 min
180 min
Return to baseline
(n = 19)
Mean (n = 19)
Mean (n = 19)
Mean (n = 19)
Mean (n = 19)
Mean (n = 17)
Mean (n = 17)
Mean (n = 8)
(n = 19)
3.6 1.4 3.5 1.4 82 16 132 25 77 12
2.9 0.8* 2.9 1* 66 10* 108 13* 62 11*
3 0.8 3 1.1 72 11 117 15* 72 14
3.1 0.7 3 0.9 75 22 116 20* 68 10*
3.2 0.9 3.1 0.9 76 20 120 12* 71 10
2.3 1* 2.2 1.1* 68 18* 121 11 72 8
2.4 1.2* 2.3 1.2* 67 11* 119 11* 72 8
2.5 0.8* 2.6 0.9* 68 16* 119 12* 67 8*
3.0 0.9 2.9 1.0 75 17* 119 12* 67 7*
ANOVA test of repeated measures, *P < 0.05.
Please cite this article in press as: Lowenstein L, et al. Steep Trendelenburg position during robotic sacrocolpopexy and heart rate variability. Eur J Obstet Gynecol (2014), http://dx.doi.org/10.1016/j.ejogrb.2014.03.046
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settings. As such, HRV can be considered as a sign of well-being and health, while decreased HRV is associated with disease and risk for mortality [5]. The present study showed statistically significant decreases in the activity of both arms of the autonomic nervous system following Trendelenburg positioning. The changes observed in the autonomic nervous system were parallel in the two arms of the ANS, indicating that the autonomic tone was not changed. The cause of the second phase decrease in the ANS and heart rate is not completely understood. We speculate that the activation of the second phase, which is much slower than that of the first phase, may involve the renin–angiotensin system; this is yet to be determined in future studies. The changes in heart rate following the steep Trendelenburg concur with a previous study, conducted by Choi et al., that reported a statistically significant decrease in heart rate 10 min following pneumoperitoneum and steep Trendelenburg positioning [20]. The researchers in that study recorded heart rate and other hemodynamic parameters for only 120 min, and therefore did not document the second phase decrease. A possible limitation of the current study is the investigation of a homogenous population consisting of only healthy women who underwent one type of surgical procedure. Nevertheless, the study highlights the importance of considering the consequences of prolonged Trendelenburg positioning in the selection of robotic surgery for each patient. Specifically, the findings suggest that precautions should be taken in women with cardiovascular disease, particularly those with arrhythmia or peripheral vascular disease who may not tolerate the acute hemodynamic changes during steep Trendelenburg. In conclusion, the steep Trendelenburg positioning during robotic sacrocolpopexy results in significant changes in the modulation by the autonomic nervous system of heart rate variability, heart rate and blood pressure. These changes are abrupt and occur immediately after steep Trendelenburg positioning. Although these effects are transitory, a second phase of instability in heart rate and autonomic imbalance can be expected in operations that extend beyond 2 h. Close inspection of the patient is therefore imperative. Further studies in different population groups are needed to assess the clinical relevance of these findings and their generalizability, particularly to patients with cardiovascular disease. Funding None. Conflict of interest
References [1] Advincula AP, Reynolds RK. The use of robot-assisted laparoscopic hysterectomy in the patient with a scarred or obliterated anterior cul-de-sac. JSLS 2005;9:287–91. [2] Weinberg L, Rao S, Escobar PF. Robotic surgery in gynecology: an updated systematic review. Obstet Gynecol Int 2011;2011:29. Article ID 852061. [3] Akselrod S, Gordon D, Ubel FA, Shannon DC, Berger AC, Cohen RJ. Power spectrum analysis of heart rate fluctuation: a quantitative probe of beat-tobeat cardiovascular control. Science 1981;213:220–2. [4] Heart rate variability: standards of measurement, physiological interpretation and clinical use. Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology. Circulation 1996;93:1043–65. [5] Goldberger AL, Amaral LA, Hausdorff JM, Ivanov P, Peng CK, Stanley HE. Fractal dynamics in physiology: alterations with disease and aging. Proc Natl Acad Sci USA 2002;99(Suppl. 1):2466–72. [6] Pomeranz B, Macaulay RJ, Caudill MA, et al. Assessment of autonomic function in humans by heart rate spectral analysis. Am J Physiol 1985;248:H151–3. [7] Koizumi K, Terui N, Kollai M. Effect of cardiac vagal and sympathetic nerve activity on heart rate in rhythmic fluctuations. J Auton Nerv Syst 1985;12: 251–9. [8] Ugur B, Odabasi AR, Yuksel H, Sen S, Ogurlu M, Tekten T. Effects of positioning in laparoscopic adnexal surgery on QT dispersion and heart rate variability under sevoflurane anesthesia. J Laparoendosc Adv Surg Tech A 2007;17:26–31. [9] McHugh GJ, Robinson BJ, Galletly DC. Leg elevation compared with Trendelenburg position: effects on autonomic cardiac control. Br J Anaesth 1994;73:836–7. [10] Gaffney FA, Nixon JV, Karlsson ES, Campbell W, Dowdey AB, Blomqvist CG. Cardiovascular deconditioning produced by 20 hours of bedrest with headdown tilt ( 5 degrees) in middle-aged healthy men. Am J Cardiol 1985;56:634–8. [11] Norsk P, Stadeager C, Johansen LB, et al. Volume-homeostatic mechanisms in humans during a 12-h posture change. J Appl Physiol 1985;75:349–56. 1993. [12] Heart rate variability. Standards of measurement, physiological interpretation, and clinical use. Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology. Eur Heart J 1996;17:354–81. [13] Bump RC, Mattiasson A, Bo K, et al. The standardization of terminology of female pelvic organ prolapse and pelvic floor dysfunction. Am J Obstet Gynecol 1996;175:10–7. [14] Butler GC, Xing HC, Hughson RL. Cardiovascular response to 4 hours of 6 degrees head-down tilt or of 30 degrees head-up tilt bed rest. Aviat Space Environ Med 1990;61:240–6. [15] Gharib C, Gauquelin G, Pequignot JM, Geelen G, Bizollon CA, Guell A. Early hormonal effects of head-down tilt ( 10 degrees) in humans. Aviat Space Environ Med 1988;59:624–9. [16] Bickel A, Yahalom M, Roguin N, et al. Power spectral analysis of heart rate variability during positive pressure pneumoperitoneum: the significance of increased cardiac sympathetic expression. Surg Endosc 2002;16:1341–4. [17] Goldberger AL, Mietus JE, Rigney DR, Wood ML, Fortney SM. Effects of headdown bed rest on complex heart rate variability: response to LBNP testing. J Appl Physiol (1985) 1994;77:2863–9. [18] Christensen NJ, Heer M, Ivanova K, Norsk P. Sympathetic nervous activity decreases during head-down bed rest but not during microgravity. J Appl Physiol (1985) 2005;99:1552–7. [19] Levy MN. Autonomic interactions in cardiac control. Ann N Y Acad Sci 1990;601:209–21. [20] Choi DK, Lee IG, Hwang JH. Arterial to end-tidal carbon dioxide pressure gradient increases with age in the steep Trendelenburg position with pneumoperitoneum. Korean J Anesthesiol 2012;63:209–15.
None.
Please cite this article in press as: Lowenstein L, et al. Steep Trendelenburg position during robotic sacrocolpopexy and heart rate variability. Eur J Obstet Gynecol (2014), http://dx.doi.org/10.1016/j.ejogrb.2014.03.046
EURO-8507; No. of Pages 4 European Journal of Obstetrics & Gynecology and Reproductive Biology xxx (2014) xxx–xxx
Contents lists available at ScienceDirect
European Journal of Obstetrics & Gynecology and Reproductive Biology journal homepage: www.elsevier.com/locate/ejogrb
Steep Trendelenburg position during robotic sacrocolpopexy and heart rate variability Lior Lowenstein a,1,*, Mona Mustafa a,1, Yechiel Z. Burke a, Susana Mustafa a, Dror Segal b, Amir Weissman a a Department of Obstetrics and Gynecology, Rambam Medical Center, Ruth and Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel b Department of Anesthesiology, Rambam Medical Center, Ruth and Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
A R T I C L E I N F O
A B S T R A C T
Article history: Received 9 December 2013 Received in revised form 20 January 2014 Accepted 31 March 2014
Objectives: The objective of this study was to evaluate heart rate variability and hemodynamic parameters following steep Trendelenburg positioning during robotic sacrocolpopexy. Study design: For 19 women, median age 57 (range: 45–72), blood pressure and ECG were recorded during surgery. From the ECG signals interbeat intervals were used to assess heart rate variability, analyzed in time and frequency domains using the Fast Fourier transform. The low frequency and high frequency spectral bands were used to assess sympathetic and parasympathetic pathways respectively. Results: All women underwent robotic supracervical hysterectomy and sacrocolpopexy. A statistically significant decrease in the mean values of the low-frequency and high-frequency spectral bands, representing sympathetic and parasympathetic activity, respectively were demonstrated 5 min following Trendelenburg positioning of the patients (from 3.6 1.4 to 2.9 0.8 ms2/Hz, and from 3.5 1.4 to 2.9 1 ms2/Hz, P < 0.05). These changes correlated with a mean 20% decrease in heart rate, which lasted for 30 min, and with a second drop in sympathetic and parasympathetic activity and heart rate, commencing 2 h from the start of surgery, and lasting until the end of the operation. Conclusions: Steep Tredelenburg positioning during robotic urogynecology surgery results in significant changes in the autonomic nervous system modulation of heart rate variability and in other hemodynamic parameters. ß 2014 Elsevier Ireland Ltd. All rights reserved.
Keywords: Robotic surgery Urogynecology Autonomic nervous system Trendelenburg Heart rate variability
1. Introduction Sacrocolpopexy can be performed through different routes – abdominal, laparoscopic or robotic. Over the past decade the robotic approach has become more common. Robotic assisted surgery was approved by the Food and Drug Administration for gynecologic procedures in 2005 based on preliminary evidence of safety and efficacy [1]. The main advantages of robotic surgery are: the tremor reduction system, high definition 3D vision, the option to use three surgical arms under the surgeon’s control and 7 degrees of freedom for wrist movement. The latter enables less experienced laparoscopic surgeons to perform more complex
* Corresponding author. Tel.: +972 4 8542382. E-mail addresses: [email protected], [email protected] (L. Lowenstein). 1 These authors contributed equally to this work.
procedures. These advantages may explain the rapid increase in adoption of da Vinci1 surgery for gynecology [2]. Among the disadvantages of robotic surgery is the difficulty in changing patient’s position during operation. Since the procedures performed by robotic surgery are usually more complex than those performed through other routes, the effect of long lasting Trendelenburg positioning on the cardiovascular and autonomic system needs investigation. Two issues regarding cardiovascular function during robotic surgery are important to patient safety: the steep Trendelenburg position and the induction of pneumoperitoneum during the operation. Both conditions can alter cardiovascular function and may be hazardous in some patients, particularly those with preexisting cardiac or pulmonary disease. Heart rate variability (HRV) is a common tool for the noninvasive investigation of heart rate modulation by the autonomic nervous system (ANS). HRV is modulated by different central and peripheral inputs, and provides a quantitative marker of autonomic activity. Analysis of HRV by power spectral density is an
http://dx.doi.org/10.1016/j.ejogrb.2014.03.046 0301-2115/ß 2014 Elsevier Ireland Ltd. All rights reserved.
Please cite this article in press as: Lowenstein L, et al. Steep Trendelenburg position during robotic sacrocolpopexy and heart rate variability. Eur J Obstet Gynecol (2014), http://dx.doi.org/10.1016/j.ejogrb.2014.03.046
G Model
EURO-8507; No. of Pages 4 2
L. Lowenstein et al. / European Journal of Obstetrics & Gynecology and Reproductive Biology xxx (2014) xxx–xxx
effective means of studying effects of the autonomic nervous system on heart rate, both in healthy and diseased individuals [3,4]. The existence of adequate HRV is considered a factor of cardiovascular health and integrity, while decreased HRV may be associated with illness, aging and increased mortality rates from cardiovascular disease [5] HRV results from the dynamic interplay between the sympathetic and parasympathetic nervous systems. The interbeat intervals (computed from successive R–R intervals) that compose HRV represent instantaneous interactions of the beat-to-beat control mechanisms mediated by the ANS. The vagal activity is thought to be a major component of the high-frequency (HF) spectral band, whereas the origin of the low-frequency (LF) spectral band is more controversial. Some consider it to represent sympathetic modulation, whereas others consider it to include both sympathetic and vagal influences. However, in most reports, LF is used mainly as a representation of the effect of the sympathetic nervous system [6,7] Previous studies evaluating the effect of Trendelenburg positioning during laparoscopic operations on the autonomic system showed inconsistent or even conflicting findings [8]. One study reported marked activation of the autonomic cardiac response [8]; yet another study reported an absence of significant differences in the spectral components of heart rate between the supine and Trendelenburg positions [9]. Moreover, most studies have examined the effects of moderate levels of head-down tilt (usually less than 20 degrees), and the majority focused on the effects of recovery from prolonged periods of head-down bed rest, but not the acute effects of head-down tilt, as encountered in robotic operations [10,11]. The inconsistency of the findings and the increasing use of robotic operations with patients positioned in a steep Trendelenburg prompted us to research this topic. The aim of the current study was therefore to evaluate the modulation of the autonomic nervous system on heart rate variability following Trendelenburg positioning during robotic sacrocolpopexy. 2. Materials and methods The local Research Ethics Institutional Review Committee of Rambam Health Care Campus approved the study protocol. Women who underwent robotic sacrocolpopexy at our tertiarycare referral center were invited to participate in the study. Informed consent was obtained from all participants. Exclusion criteria were: (1) medical disorders that can interfere with the autonomic nervous system (e.g. coronary heart disease, a history of heart failure or other cardiac disease, hypertension, neurological diseases, diabetes or thyroid disease; (2) the use of medications that can interfere with the autonomic nervous system, including beta-receptor agonists or antagonists, anti-arrhythmic agents or antihypertensive drugs, anticholinergic agents or adrenergic alpha-antagonists, tricyclic or serotoninergic antidepressants. 2.1. Surgical procedure Robotic sacrocolpopexy was performed using the da Vinci Surgical System. Following abdominal insufflation with 14 mm of mercury with CO2, we introduced five ports in a shallow ‘‘W’’ formation: one supra umbilical 12-mm port for the laparoscope; one 10-mm port placed sub-coastally lateral to the rectus muscle on the right side, and three 8-mm robotic ports in bilateral lower quadrants, two on the left and one on the right. Prior to docking of the robotic side cart, patients were positioned in steep Trendelenburg (30 degrees). In women with uterovaginal prolapse, we performed a supracervical hysterectomy, with or without bilateral salpingoopherectomy. The decision for salpingoopherectomy was
based on clinical history and patients’ preference. In addition to the sacrocolpopexy, concomitant procedures were performed as indicated: posterior colpoperineorrhaphy, anterior colporrhaphy and midurethral slings for stress urinary incontinence. 2.2. Signal acquisition and processing Three standard surface chest electrodes were fitted to each participant and were used to record the electrocardiogram (ECG) continuously following patient intubation. We entered into the computer all patient-related events, including changes in position. The ECG was recorded through a 12-bit analog/digital data acquisition card (National Instruments, Austin TX) with a sampling frequency of 200 Hz, and stored in a computer for offline studies. The digitized ECG signals were recorded at baseline in the supine position, immediately following the change to the Trendelenburg position, and every 30 min thereafter, until return to the supine position. The data were then processed and analyzed via dedicated robust software to detect the R wave peaks. The R point of each QRS complex was defined and the interval between two consecutive R points (the R–R interval) was computed. All R–R intervals were visually inspected and manually edited, if necessary, to exclude background noise and artifacts. A ‘‘clean’’ 5-min segment (preferably unedited) was used for the analyses. Time and frequency domain analyses were performed as previously described [12]. Briefly, heart rate variability was evaluated in accordance with the guidelines of the Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology [12]. The power spectral bands were quantified by measuring the area under the following frequency bands: lowfrequency (LF) (0.04–0.15 Hz), known to represent a mixture of sympathetic and vagal activity but mainly the sympathetic activity, and high-frequency (HF) (0.15–0.4 Hz), representing parasympathetic activity. Three distinct frequency bands can be distinguished in the power spectrum of the interbeat interval. The HF band corresponds to the effect of respiratory sinus arrhythmia and is controlled by vagal activity, therefore reflecting parasympathetic influences. The LF component of the power spectrum is generally thought to reflect primarily sympathetic, and to a lesser extent, parasympathetic activity. The very low frequency band (VLF) is a less specific indicator of heart rate variability and is thought to be under the control of thermo-regulation, the renin– angiotensin system, and other mediators of low frequency oscillations in heart rate. The instantaneous heart rate represents the net interactions between vagal and sympathetic regulation, the former decreasing heart rate and the latter increasing heart rate. The higher the numbers in the low-frequency spectral band, the higher the sympathetic tone and vice versa. On the contrary, the higher the numbers in the high-frequency spectral band, the higher the parasympathetic tone. Thus, a rise in heart rate can be the consequence of an increase in sympathetic activity, but it may also result from a decrease in vagal regulation or from simultaneous changes in both regulatory systems. Sociodemographic data, preoperative standardized prolapse assessment according to the Pelvic Organ Prolapse Quantification (POP-Q) system [13], medical history including parity, previous pelvic surgery or hysterectomy, concomitant surgical procedures and estimated blood loss and complications during surgery were retrieved from patients’ electronic charts. 2.3. Statistical analysis We used Statgraphics statistical package (StatPoint technologies, Warrenton, VA) for data management and statistical analysis. Descriptive statistics are reported as mean (SD) for continuous
Please cite this article in press as: Lowenstein L, et al. Steep Trendelenburg position during robotic sacrocolpopexy and heart rate variability. Eur J Obstet Gynecol (2014), http://dx.doi.org/10.1016/j.ejogrb.2014.03.046
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variables, median and interquartile range for ordinal variables and number (percentage) for categorical variables. The normality of HRV data was examined using the Kolmogorov–Smirnov statistic. When the normality assumption was violated, data were transformed using logarithmic transformation prior to further statistical analysis. To evaluate the effect of patient position changes on parameters of heart rate variability, ANOVA Models for repeated measures were used. Spearman’s analysis was used to evaluate the correlation between heart rate and autonomic system activity. Group size was calculated by an a priori power analysis aimed at 80% power to allow a difference of 20% at a two-sided significance level of 5% in each of the variables examined. This indicated that a sample size of 17 participants would be adequate. All tests were considered significant at the 0.05 level. 3. Results Nineteen women participated in the study. Their median age was 57 years (range: 45–72) and median BMI 27 kg/m2 (range: 23– 33). In 4 patients (21%), the American Society of Anesthesiologists (ASA) score was 1, and in 15 (79%), the ASA score was 2. All patients underwent subtotal hysterectomy and sacrocervicopexy. A total of 12 underwent additional procedures at the time of the robotic surgery; 6 TVT-O (Gynecare, Johnson & Johnson), 1 anterior colporrhaphy and 7 salpingo-oophorectomy. The median duration of operation was 174 min (range 110–263). None of the procedures required conversion from robotic to laparoscopic or open surgery. Median blood loss during surgery was 38 ml (range: less than 10– 200 ml). Significant decreases in the mean values of both HF and LF spectral densities were documented 5 min following the change to the Trendelenburg position (from 3.6 1.41 to 2.9 0.8 ms2/Hz, and from 3.5 1.4 to 2.9 1 ms2/Hz, respectively, P < 0.05, Table 1). Thereafter, a gradual recovery of both frequency bands was observed. However, a second decrease was recorded at about 2 h from the beginning of the operation, followed by a slow and gradual recovery that persisted until the conclusion of the operation. Concomitant with the initial decrease in the spectral bands, mean heart rate decreased significantly, and then immediately showed a progressive recovery. A second decrease in mean heart rate occurred 2 h after the beginning of surgery (in 15 of the patients [79%]) and continued until the end of the operation (from 82 16 to 66 10 bpm, P < 0.05, Table 1). Immediately following Trendelenburg positioning, abrupt but transient decreases in mean systolic and diastolic blood pressure were observed (from 132 25 to 108 13 mmHg and from 77 12 to 62 11 mmHg, respectively, P < 0.05, Table 1). A gradual process of recovery followed the decrease. 4. Comments Robotic-assisted laparoscopic operations require the application of steep Trendelenburg positioning and the induction of pneumoperitoneum for a relatively prolonged period. Changing a patient’s positioning during an operation requires undocking the robot from the patient, which entails complex manipulations.
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Therefore, in most cases, the patient is left in the initial position for the entire duration of the operation. Our findings show a statistically significant decrease in the activity of both sympathetic and parasympathetic systems following steep Trendelenburg positioning of patients who underwent robotic operations for the repair of pelvic organ prolapse. These changes occurred immediately following steep Trendelenburg positioning. A trend toward returning to baseline activity could be seen 30 min after the beginning of the operation, while a second phase of decrease in the mean power spectral density was demonstrated following a more prolonged Trendelendburg positioning (two hours from surgery). The changes in sympathetic activity correlated with a mean 20% decrease in patients’ heart rate from an average of 82 to 66 beats per minutes, and with a decrease in both systolic and diastolic blood pressure measurements. The initial response to head down tilt is an instantaneous shift in fluids to the thoracic cavity with an increase in central venous pressure [10,11]. This is followed by a rapid increase in stroke volume and cardiac output [14]. The activity of the renin–angiotensin system is reduced [11], while the concentration of atrial natriuretic peptide may be increased [15]. Further to the placement of the patient in a steep head-down tilt, the induction of pneumoperitoneum can cause other significant circulatory perturbations, including decreased venous return, increased systemic vascular resistance and increased mean arterial pressure. These effects may have deleterious effects in patients with preexisting cardiac disease, or in the aged [16]. Autonomic nervous system activity is intimately associated to body position and the level of gravitational strain imposed on the cardiovascular system [14,16]. The baroreflex feedback loop adjusts sympathetic activity to maintain stable blood pressure, despite variations in venous return to the heart. Therefore, sympathetic activity is increased when venous return is low, as when assuming the upright position; whereas it is suppressed when venous return is increased, such as in the head-down tilt. Most studies that have investigated the effects of head-down tilt, examined cardiovascular and autonomic functions in a relatively moderate level of inclination (usually 6–20 degrees), or during prolonged time periods that assumed the head-down tilt, as in space missions of astronauts [17,18]. However, data regarding the acute effects of the autonomic nervous system in steep Trendelenburg (30 degrees), as applied in robotic operations, is very limited. Healthy cardiac function is characterized by irregular time intervals between successive heart beats. This heart rate variability (HRV) results from rhythmic oscillations of the regulatory mechanisms of cardiac activity that maintain heart rate within a constant range and coordinate responses to the continuously changing conditions. HRV primarily emerges through the activity of the two arms of the autonomic nervous system and the additional influences of humoral, neural, thermoregulatory, and other control and feedback mechanisms [19]. HRV has thus emerged as a simple, noninvasive measure that has been explored in a variety of clinical situations. It is now well accepted that the autonomic nervous system and its modulation of HRV plays an important role in physiological, as well as various pathological
Table 1 Changes in heart rate, blood pressure and autonomic variables during robotic sacrocolpopexy.
Low frequency (LF) High frequency (HF) Heart rate (HR) Systolic blood pressure Diastolic blood pressure
Baseline
5 min
30 min
60 min
90 min
120 min
150 min
180 min
Return to baseline
(n = 19)
Mean (n = 19)
Mean (n = 19)
Mean (n = 19)
Mean (n = 19)
Mean (n = 17)
Mean (n = 17)
Mean (n = 8)
(n = 19)
3.6 1.4 3.5 1.4 82 16 132 25 77 12
2.9 0.8* 2.9 1* 66 10* 108 13* 62 11*
3 0.8 3 1.1 72 11 117 15* 72 14
3.1 0.7 3 0.9 75 22 116 20* 68 10*
3.2 0.9 3.1 0.9 76 20 120 12* 71 10
2.3 1* 2.2 1.1* 68 18* 121 11 72 8
2.4 1.2* 2.3 1.2* 67 11* 119 11* 72 8
2.5 0.8* 2.6 0.9* 68 16* 119 12* 67 8*
3.0 0.9 2.9 1.0 75 17* 119 12* 67 7*
ANOVA test of repeated measures, *P < 0.05.
Please cite this article in press as: Lowenstein L, et al. Steep Trendelenburg position during robotic sacrocolpopexy and heart rate variability. Eur J Obstet Gynecol (2014), http://dx.doi.org/10.1016/j.ejogrb.2014.03.046
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settings. As such, HRV can be considered as a sign of well-being and health, while decreased HRV is associated with disease and risk for mortality [5]. The present study showed statistically significant decreases in the activity of both arms of the autonomic nervous system following Trendelenburg positioning. The changes observed in the autonomic nervous system were parallel in the two arms of the ANS, indicating that the autonomic tone was not changed. The cause of the second phase decrease in the ANS and heart rate is not completely understood. We speculate that the activation of the second phase, which is much slower than that of the first phase, may involve the renin–angiotensin system; this is yet to be determined in future studies. The changes in heart rate following the steep Trendelenburg concur with a previous study, conducted by Choi et al., that reported a statistically significant decrease in heart rate 10 min following pneumoperitoneum and steep Trendelenburg positioning [20]. The researchers in that study recorded heart rate and other hemodynamic parameters for only 120 min, and therefore did not document the second phase decrease. A possible limitation of the current study is the investigation of a homogenous population consisting of only healthy women who underwent one type of surgical procedure. Nevertheless, the study highlights the importance of considering the consequences of prolonged Trendelenburg positioning in the selection of robotic surgery for each patient. Specifically, the findings suggest that precautions should be taken in women with cardiovascular disease, particularly those with arrhythmia or peripheral vascular disease who may not tolerate the acute hemodynamic changes during steep Trendelenburg. In conclusion, the steep Trendelenburg positioning during robotic sacrocolpopexy results in significant changes in the modulation by the autonomic nervous system of heart rate variability, heart rate and blood pressure. These changes are abrupt and occur immediately after steep Trendelenburg positioning. Although these effects are transitory, a second phase of instability in heart rate and autonomic imbalance can be expected in operations that extend beyond 2 h. Close inspection of the patient is therefore imperative. Further studies in different population groups are needed to assess the clinical relevance of these findings and their generalizability, particularly to patients with cardiovascular disease. Funding None. Conflict of interest
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Please cite this article in press as: Lowenstein L, et al. Steep Trendelenburg position during robotic sacrocolpopexy and heart rate variability. Eur J Obstet Gynecol (2014), http://dx.doi.org/10.1016/j.ejogrb.2014.03.046
