Original article 23
Elevated lactate level and shock index in nontraumatic hypotensive patients presenting to the emergency department Arif A. Cevik, Hakan Dolgun, Setenay Oner, Baran Tokar, Nurdan Acar, Engin Ozakin and Filiz Kaya Background The aim of our study was to evaluate the effect of lactate level (LL) and shock index (SI) on the outcome in nontraumatic hypotensive patients in the emergency department, and also to show the significance of the combined usage of these two parameters.
(NPV): 100.0%]. Vasoactive drug use was higher in lactate–SI group 1 (32.8%, P < 0.0001, sensitivity: 100.0%, NPV: 100.0%). Lactate–SI group 1 showed a higher hospitalization rate (67.8%, P > 0.05). In-hospital mortality in lactate–SI group 1 was higher (54.1%, P < 0.0001, sensitivity: 100.0%, NPV: 100.0%).
Methods This is a prospective, observational study. Elevated and normal LL (ELL and NLL), elevated and normal SI (ESI and NSI), and a combination of these two parameters (lactate–SI group 1: ELL and ESI, lactate–SI group 2: ELL or ESI, and lactate–SI group 3: NLL and NSI) were evaluated for primary (mortality) and secondary outcome measures.
Conclusion The combination of both parameters is effective in predicting these outcome measures with higher sensitivities and NPVs. Further studies on the subject are required. European Journal of Emergency c 2015 Wolters Kluwer Medicine 22:23–28 Copyright Health, Inc. All rights reserved.
Results A total of 131 patients who fulfilled the inclusion criteria were analysed. Of the patients with ELL, 34.78% were mechanically ventilated (P < 0.001), 31.88% received vasoactive drugs (P < 0.001), and 68.1% were hospitalized (P < 0.01). The mortality rate among patients with ELL was 50.72% (P < 0.001). Of the patients with ESI, 39.42% died (P < 0.01). Use of mechanical ventilation in the emergency department was higher in lactate–SI group 1 [36.1%, P < 0.0001, sensitivity: 100.0%, negative predictive value
Introduction In critically ill patients, elevated lactate level (ELL, >2 mmol/l) was shown to be an independent factor associated with mortality in medical and surgical patients [1,2]. It has been studied in critically ill patients with sepsis, trauma patients, and in those with organ failure in the emergency department (ED) [3]. LL is also a marker used in follow-up of resuscitation success [4]. Shock index (SI) is defined as the heart rate divided by the systolic blood pressure. SI can be a helpful tool, especially when it is abnormal, even when heart rate and blood pressure are in normal ranges [5,6]. SI values ranging from 0.5 to 0.7 are described as normal. It is a suggested marker for predicting the severity of patients, especially when it is over 0.9 [5]. SI has also been used as a marker in emergency patients with sepsis, trauma patients and in those with some other serious condition. However, the majority of the studies were on trauma patients. There are insufficient data in the literature indicating whether SI can be used in all emergency patients regardless of diagnosis, particularly in nontraumatic patients [7]. c 2015 Wolters Kluwer Health, Inc. All rights reserved. 0969-9546 Copyright
European Journal of Emergency Medicine 2015, 22:23–28 Keywords: emergency, hypotension, lactate level, shock index Department of Emergency Medicine, Eskisehir Osmangazi University, Meselik, Eskisehir, Turkey Correspondence to Arif A. Cevik, MD, Department of Emergency Medicine, Eskisehir Osmangazi University, Meselik, 26440 Eskisehir, Turkey Tel: + 90 222 2392979; fax: + 90 222 2393774; e-mail: [email protected] Received 6 May 2013 Accepted 10 December 2013
To predict the outcome in emergency patients, several markers can be used in the ED. LL and SI were suggested to be valuable parameters in predicting the severity of patients. However, the majority of research has been conducted on patients with specific diagnoses such as sepsis, trauma and severe infection. There is a need for studies designed to investigate the value of these parameters in ED patients regardless of diagnosis. The data obtained from these studies may help establish the criteria that can be used to predict the outcome in the beginning of the evaluation process in the ED. These parameters have been studied separately, and according to our knowledge combinations of these two parameters in nontraumatic patients have not been studied yet. A prospective study evaluating these two parameters together may yield some significant findings. In this study, the aim was to evaluate the effect of LL and SI on the outcome in nontraumatic hypotensive patients in the ED. We also aimed to show the significance of the combination of these two parameters. DOI: 10.1097/MEJ.0000000000000110
Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
24 European Journal of Emergency Medicine 2015, Vol 22 No 1
Methods Hospital
This prospective observational study was conducted in the ED of a university hospital in central Anatolia, Turkey. The hospital is a 1200-bed, urban, academic, tertiary care hospital and has medical, surgical, coronary, neurological and paediatric ICUs with 120 beds.
Patients
The ED had 653 nontraumatic hypotensive patients in the year 2012. We applied 5% error and 95% confidence level, and expected 90% correct results in calculating the minimum number of patients in the study (n = 115). After reviewing data from the hospital, we assumed that a 4-month period would give us enough number of cases. The patients who presented to the ED with hypotension (systolic blood pressure of 90 mmHg or less) during the 4-month period were included in the study. Patients over 18 years of age were selected.
Inclusion and exclusion criteria
Nontraumatic patients who were diagnosed as hypotensive were eligible for the study. Trauma patients and those with known hepatic or renal failure, haematologic cancers, and out-of-hospital cardiac arrest were excluded. Patients who were sent to the operating theatre directly from the ED before taking the blood samples and those who refused to participate in the study were also excluded.
Measurement of lactate level and calculation of shock index
LLs of initial venous blood samples were measured [8] using a Radiometer ABL800 FLEX analyser (Radiometer Medical, Bronshoj, Denmark). The measuring range of the analyser for lactate is 0.0–30.0 mmol/l. LLs that were reported as out of measurement range of the analyser were excluded from the analysis. SI was calculated as the heart rate divided by the systolic blood pressure. The patients were admitted to the monitored bed unit of the ED. In the first 5 min of medical evaluation, LL was evaluated in the first sample of venous blood and SI was calculated from the first blood pressure measurement during this period. Blood samples for the evaluation of LL and measurement of SI were obtained before all invasive procedures (intubation, mechanical ventilation, etc.) or treatments (vasoactive drug, etc.). Lactate level and shock index subgroups
LLs and SI were categorized on the basis of the cutoff levels in the literature. LLs of the patients were categorized as 2 mmol/l or less [normal lactate level (NLL)] and greater than 2 mmol/l (ELL). SI of the patients was categorized as 0.9 or less [normal SI group (NSI)] and over 0.9 [elevated SI group (ESI)]. The patients with both ELL and ESI belonged to lactate–SI group 1. The patients with only one elevated parameter belonged to lactate–SI group 2. Patients with both NLL and NSI belonged to lactate–SI group 3. Outcome measures
Data acquisition
Descriptive data of patients including age, sex, vital signs, level of consciousness (Glasgow Coma Scale), haematological and biochemical test results such as LL, SI, intubation and mechanical ventilation and/or vasopressor agent use in the ED, hospitalization and mortality were recorded. Data were acquired by the ED team (attending physician, emergency medicine residents and nurses) who were trained on the data parameters of the research. Complete history was taken and full physical examination was performed by the attending physician and/or the senior emergency medicine residents in the ED. Additional laboratory or radiological tests were conducted as necessary.
Written consent procedure
Written consent was received from the patients or their family members depending on the level of consciousness and co-operation of the patients. Blood samples for estimation of LL and calculation of SI were obtained from all eligible patients in the first 5 min of the medical evaluation. Data used in this study are from patients who provided consent.
In-hospital mortality was the main outcome measure of the study. Need for mechanical ventilation in the ED, vasoactive drug use in the ED and hospitalization were defined as secondary outcome measures. The clinicians responsible for patient care did not use LLs and/or SI in decision-making. In-hospital mortality was described as mortality in the ED and in-hospital ward or ICU during a month. Statistical analyses
The Kolmogorov–Smirnov test was used to show the normality distribution of the data. The Mann–Whitney U-test in binary groups was used as the data did not show a normal distribution, and the results of variables were presented as median values with interquartile ranges (IQRs). Independent samples t-test was used for normally distributed data. The w2-test and Fisher’s exact test were used for frequency distribution analyses. Mean values were described in terms of standard error (SE) of means as appropriate. SPSS, version 18 (SPSS Inc., Chicago, Illinois, USA) was used for statistical analyses. Sensitivity, specificity, positive predictive value (PPV) and negative predictive values (NPV) in groups for outcome measures were defined. Odds ratios (ORs) with 95% confidence intervals (CI) were reported as appropriate.
Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
Elevated lactate level and shock index Cevik et al. 25
Ethics and governance
The study was commenced after obtaining approval from the Research Ethics and Review Board of the University Medical Centre.
Results There were 177 hypotensive patients during study period; 46 patients were excluded because of the following reasons: hepatic failure (five patients), renal failure (12 patients), haematologic cancer (12 patients), out-of-hospital cardiac arrest (four patients) and trauma (13 patients). No patient refused consent. LL was not reported by the analyser as it was out of the measurement range. A total of 131 patients who fulfilled the inclusion criteria were included for statistical analysis. Descriptive data with lactate levels and shock index
The mean age of the patients was 62.35±1.63 years (18–100 years, median: 68 years). The number of men was 77 (58.8%). There were 69 patients with ELL and 62 patients with NLL. The mean LL was found to be 2.66± 0.35 mmol/l among the women and 3.44±0.42 mmol/l among the men (P > 0.05). Of the patients, 104 had ESI and 27 had NSI. The mean SI was higher among female patients (1.48±0.09 vs. 1.31±0.06; P > 0.05). Outcome measures according to lactate levels
Outcome measures according to LLs are shown in Table 1. Details of the data are described as follows.
rate was 3.22% (two patients) among patients with NLL (P < 0.001). The risk of vasoactive drug use in the patients with ELL (OR: 14.043, 95% CI 3.143–62.748) was higher than that among NLL patients (sensitivity: 91.67%, 95% CI 72.96–98.73%; specificity: 56.07%, 95% CI 46.15–65.66%; PPV: 31.88%, 95% CI 21.18–44.21%; NPV: 96.77%, 95% CI 88.80–99.51%). Hospitalization
Of the patients, 75 were hospitalized in the study: 47 (68.1%) with ELL and 28 (45.2%) with NLL (P < 0.01). Patients with ELL showed a higher risk for hospitalization (OR: 2.594, 95% CI 1.273–5.285) compared with patients with NLL (sensitivity: 62.67%, 95% CI 50.73–73.57%; specificity: 60.71%, 95% CI 46.75–73.50%; PPV: 68.12%, 95% CI 55.79–78.82%; NPV: 54.84%, 95% CI 41.68–67.52%). Mortality
There were 43 in-hospital deaths. The mortality rate among patients with ELL was 50.72% (35 patients), whereas it was 12.90% (eight patients) in the NLL group (P < 0.001). Patients with ELL showed a higher risk (OR: 6.949, 95% CI 2.883–16.749) than patients with NLL for in-hospital mortality (sensitivity: 81.40%, 95% CI 66.59–91.58%; specificity: 61.36%, 95% CI 50.38–71.56%; PPV: 50.72%, 95% CI 38.41–62.98%; NPV: 87.10%, 95% CI 76.14–94.24%). Outcome measures according to shock index
Mechanical ventilation use in the emergency department
A total of 26 patients needed intubation and mechanical ventilation in the ED. Of the patients with ELL, 24 (34.78%) were mechanically ventilated (P < 0.001). The risk of mechanical ventilation in the ED was higher among patients with ELL (OR: 16.0, 95% CI 3.594–71.234) than among those with NLL (sensitivity: 92.31%, 95% CI 74.83–98.83%; specificity: 57.14%, 95% CI 47.11–66.76%; PPV: 34.78%, 95% CI 23.71–47.21%; NPV: 96.77%, 95% CI 88.80–99.51%).
Outcome measures according to SI are shown in Table 2. Details of the data are described as follows. Mechanical ventilation use in the emergency department
Of the patients, 26 were mechanically ventilated in the ED: 22 (92.30%) belonged to the ESI group. However, only 24 of 104 patients with ESI (23.07%) were intubated and mechanically ventilated, whereas intubation rate was 7.40% (two patients) in the NSI group (P > 0.05).
Vasoactive drug use in the emergency department
Vasoactive drug use in the emergency department
Vasoactive drugs were used in 24 patients (18.32%) in the ED: 22 of those patients (91.66%) had ELL and ESI. The percentage of patients with ELL who received vasoactive drugs in the ED was 31.88% (22 patients), whereas this
Of the patients, 24 received vasoactive drugs: 22 of 104 patients with ESI (21.15%) received vasoactive drugs in the ED, whereas this rate was 7.40% (two patients) in the NSI group (P > 0.05).
Table 1
Lactate levels and outcome measures Lactate > 2 mmol/l [N (% in group)]
Mechanical ventilation Vasoactive drug use Hospitalization In-hospital death
24 22 47 35
(34.8) (31.9) (68.1) (50.72)
Lactate r 2 mmol/l [N (% in group)] 2 2 28 8
(3.2) (3.2) (45.2) (12.9)
Sensitivity (%)
Specificity (%)
PPV (%)
NPV (%)
OR
P-value
92.31 91.67 62.67 81.40
57.14 56.07 60.71 61.36
34.78 31.88 68.12 50.72
96.77 96.77 54.84 87.10
16.0 14.043 2.594 6.949
< 0.001 < 0.001 < 0.01 < 0.001
NPV, negative predictive value; OR, odds ratio; PPV, positive predictive value.
Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
26 European Journal of Emergency Medicine 2015, Vol 22 No 1
Table 2
Shock index and outcome measures SI r 0.9 [N (% in group)]
SI > 0.9 [N (% in group)] Mechanical ventilation Vasoactive drug use Hospitalization In-hospital death
24 22 58 41
(23.1) (21.2) (55.8) (39.42)
2 2 17 2
Sensitivity (%)
Specificity (%)
PPV (%)
NPV (%)
OR
P-value
92.31 91.67 77.33 95.35
23.81 23.36 17.86 28.41
23.03 21.15 55.77 39.42
92.59 92.59 37.04 92.59
3.750 3.354 0.742 8.135
> 0.05 > 0.05 > 0.05 < 0.01
(7.4) (7.4) (63.0) (7.4)
NPV, negative predictive value; OR, odds ratio; PPV, positive predictive value; SI, shock index.
Table 3
Lactate–shock index groups and outcome measures Lactate–SI group 1 [N (% in group)]a
Mechanical ventilation Vasoactive drug use Hospitalization In-hospital death
22 20 40 33
(36.1) (32.8) (67.8) (54.1)
Lactate–SI group 2 [N (% in group)]a 4 4 25 10
(7.8) (7.8) (49.0) (19.6)
Lactate–SI group 3 [N (% in group)]a 0 0 10 0
(0.0) (0.0) (52.6) (0.0)
Sensitivity (%)
Specificity (%)
PPV (%)
NPV (%)
OR
P-value
100.00 100.00 80.00 100.00
32.76 31.67 32.14 40.43
36.07 32.79 67.80 54.10
100.00 100.00 47.37 100.00
1.56 1.48 1.895 2.179
< 0.0001 < 0.0001 > 0.05 < 0.0001
a
Lactate–SI group 1, patients with high LL ( > 2 mmol/l) and high SI ( > 0.9); lactate–SI group 2, patients with high LL ( > 2 mmol/l) or high SI ( > 0.9); lactate–SI group 3, patients with normal LL (r 2 mmol/l) and normal SI (r 0.9). LL, lactate level; NPV, negative predictive value; OR, odds ratio; PPV, positive predictive value; SI, shock index.
Hospitalization
Hospitalization rate was 55.8% (58 patients) among patients with ESI, whereas the rate was 63.0% (17 patients) among patients with NSI (P > 0.05). Mortality
Of 104 patients with ESI, 41 (39.42%) died in the hospital, whereas the in-hospital mortality rate was 7.40% (two patients) among patients with NSI (P < 0.01). The risk for in-hospital mortality was higher among patients with ESI (OR: 8.135, 95% CI 1.828–36.204) than among those with NSI (sensitivity: 95.35%, 95% CI 84.16–99.30; specificity: 28.41%, 95% CI 19.30–39.02%; PPV: 39.42%, 95% CI 29.98–49.49%; NPV: 92.59%, 95% CI 75.67–98.88%). Outcome measures with group analysis
Outcome measures according to the study groups (lactate–SI groups 1, 2 and 3) are shown in Table 3. Details of the data are described as follows. We designed three study groups: in lactate–SI group 1 the patients had both ELL and ESI; in lactate–SI group 2 the patients had ELL or ESI; in lactate–SI group 3 the patients had both NLL and NSI. There were 61 patients in lactate–SI group 1, 51 patients in lactate–SI group 2, and 19 patients in lactate–SI group 3. Glasgow Coma Scale scores were lower in lactate–SI group 1 (median: 14, IQR: 6) compared with lactate–SI group 2 (median: 15, IQR: 0) and lactate–SI group 3 (median: 15, IQR: 0; P < 0.001).
PPV: 36.07%, 95% CI 24.16–49.37%; NPV: 100.0%, 95% CI 82.20–100.0%; and OR: 1.56, 95% CI 1.29–1.89. Vasoactive drug use in the emergency department
Vasoactive drug use was significantly higher in lactate–SI group 1 (20 patients, 32.8%, P < 0.0001) than in lactate– SI group 2 (four patients, 7.8%) and lactate–SI group 3 (0.0%). Comparison of lactate–SI groups 1 and 3 yielded the following results: sensitivity: 100.0%, 95% CI 83.01–100.0%; specificity: 31.67%, 95% CI 20.26–44.96%; PPV: 32.79%, 95% CI 21.31–46.00%; NPV: 100.0%, 95% CI 82.20–100.0%; and OR: 1.48, 95% CI 1.25–1.77. Hospitalization
Lactate–SI group 1 showed a higher hospitalization rate than lactate–SI group 2 and lactate–SI group 3 [40 patients (67.8%) vs. 25 patients (49.0%) and 10 patients (52.6%); P > 0.05]. Mortality
In-hospital mortality in lactate–SI group 1 was significantly higher than in lactate–SI group 2 and lactate–SI group 3 [33 patients (54.1%) vs. 10 patients (19.6%) and 0.0%; P < 0.0001]. Comparison of lactate–SI groups 1 and 3 yielded the following results: sensitivity: 100.00%, 95% CI 89.32–100.00%; specificity: 40.43%, 95% CI 26.38–55.73%; PPV: 54.10%, 95% CI 40.85–66.93%; NPV: 100.00%, 95% CI 82.20–100.00%; and OR: 2.18, 95% CI 1.67–2.86.
Mechanical ventilation use in the emergency department
Data of discharged patients
Mechanical ventilation use was significantly higher in lactate–SI group 1 (22 patients, 36.1%, P < 0.0001) than in lactate–SI group 2 (four patients, 7.8%) and lactate–SI group 3 (0.0%). Comparison of lactate–SI groups 1 and 3 yielded the following results: sensitivity: 100.0%, 95% CI 84.43–100.0%; specificity: 32.76%, 95% CI 21.01–46.34%;
A total of 56 patients were discharged from the ED. Nine of these patients revisited the ED within a 1-month period. Seven of nine patients were discharged from the ED. One patient was admitted and discharged from the ward, and one patient was admitted to the nephrology clinic and died because of renal failure complications.
Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
Elevated lactate level and shock index Cevik et al. 27
Patients who were admitted and discharged and the patient who died in the clinic had NLL and NSI during their first visit to the ED.
Discussion Lactate is always present in circulation at a low level (B1 mmol/l). The multiple hypoxic organs produce more lactate than that produced on metabolism during a shock state, and LLs increased. A current trend in emergency medicine and intensive care is to use LL in the initial assessment of the acutely ill or injured patients [9]. Initial and/or serial LLs have been used to predict mortality in general ED patients, as well as a shock of any cause [10–13]. The SI is calculated by dividing the heart rate by the systolic blood pressure. An SI ranging from 0.5 to 0.7 is normal. SI is a marker that could be used to predict the severity of the patients, especially when it is over 0.9 [5]. Although the majority of the studies on SI include traumatic patients, it has been used in emergency patients presenting with sepsis and some other serious condition. An ESI helps identify the severity of the patient’s condition before hemodynamic deterioration [14]. Therefore, SI could be considered as an appropriate triage tool for ED patients. The majority of the studies on LL and SI evaluate their relationship with mortality, especially in trauma and sepsis. The correlation of LL and SI with the need for mechanical ventilation, vasoactive drug use, and hospitalization were shown in a limited number of reports. The combination of LL and SI for emergency patients was not studied in the literature. The values of these parameters in ED patients, regardless of diagnosis, may help determine the severity of the condition in the early phase of emergency medical care. It is easy and fast to obtain LLs and to determine SI; hence these parameters can be used in risk stratification during the initial evaluation of the patients in the ED. The golden standard in determining LL is to measure the level in an arterial blood sample. However, arterial puncture can be a time-consuming and painful procedure. Therefore, we prefer to use peripheral venous LL on the basis of the findings of Lavery et al. [15], who showed no significant difference between arterial and venous LLs and reported a high correlation rate (r = 0.988). However, there are some studies showing overestimation of venous LL (bias 0.18 mmol/l, 95% CI 0.012–0.372) [16]. Although there are some discrepancies with regard to the appropriate reference interval and whether to perform single or serial lactate measurements [8], we used 2 mmol/l as a cutoff level and obtained a single LL to predict the outcome. Our approach is correlated with the literature findings [1,2]. The results of our study showed that nontraumatic hypotensive ED patients with an initial ELL (> 2 mmol/l) needed significantly more mechanical ventilation, higher vasoactive drug administration, and longer hospitalization, and the mortality rate
was higher among these patients. The mortality rate was 50.72% in the patients with ELL, and the OR was 6.94 in our study. Khosravani et al. [1] reported that an LL higher than 2 mmol/l was a significant independent predictor of mortality, and in this report, OR was up to 10.89 depending on the level of lactate. In addition to inhospital mortality as the primary outcome measure, secondary outcome measures such as mechanical ventilation, vasoactive drug use and hospitalization were also related with ELL. However, we could not find a study in the literature to compare our results with in terms of secondary outcomes. Some studies demonstrated that ELL has a significant effect on length of stay in the hospital and need for blood transfusion as secondary outcome measures [17,18]. According to the current literature, when the value of SI is over 0.9 it is considered to be elevated [5]. Our results showed that nontraumatic hypotensive ED patients with an initial ESI (> 0.9) have a significantly higher mortality rate than the NSI group. Although sensitivity and NPV were higher than lactate levels, we could not demonstrate a significant relationship between SI and mechanical ventilation, vasoactive drug use and hospitalization as we found in lactate. Correlation of these secondary outcome measures with SI has not been well described in the literature. In contrast, ESI in the early period of emergency care indicated a higher likelihood of disposition to ICU admission, surgery, or death [19]. Mortality rate was 39.42% in patients with ESI, and the OR was 8.13 in our study. Bilkova et al. [14] reported that ESI was an independent risk factor for mortality, and they found the OR to be as high as 81.26 (95% CI 9.76–676.51; P < 0.001). They found 20.3% mortality in the ESI group, compared with 4% in the low SI group. The mortality rate in the NSI group in our study was 7.4%. Another study that evaluated SI in patients with community-acquired pneumonia found that the OR of the elevated SI for 30 days mortality was 2.48 (1.04–5.92; P = 0.04) [20]. We used two parameters to designate the groups as lactate–SI group 1, lactate–SI group 2 and lactate–SI group 3. The patients with both ELL and ESI (lactate– SI group 1) had a significantly higher rate of mechanical ventilation, vasoactive drug use and mortality than patients who had normal parameters (lactate–SI group 3). Our study showed that the combination of the two parameters increased sensitivity and NPVs on all outcome measures. In addition, the patients who had normal levels of these two parameters (19 patients) did not receive mechanical ventilation and vasoactive drugs, and inhospital mortality was not determined for these patients.
Limitations
This is a single-centre prospective study. Hospitalization decisions taken on the basis of institutional or departmental guidelines have played a role in hospital admission.
Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
28 European Journal of Emergency Medicine 2015, Vol 22 No 1
Multicentre prospective studies may decrease this effect and increase the sample size. In addition, we faced difficulty in finding articles to compare our secondary survey results with, especially for mechanical ventilation and vasoactive drug use. There was no report in the literature on using a combination of both parameters, as we did in our study. The study was limited to nontrauma patients, and 13 trauma patients were excluded. Further, 33 nontrauma patients were excluded because of the possible effects of accompanying diseases on LLs. Heart rate is controlled by many medications. The elderly are expected to be on rate-limiting medication, such as calcium channel antagonists, b-blockers and other medications that would change the SI. Hypotension and shock in the ED occur because of cardiogenic, hypovolemic, distributive and obstructive problems. Using a limited set of physiological data, the use of LL and SI as predictors may still be questionable. However, we believe that SI and LL needed to be evaluated to predict outcome regardless of diagnosis of the ED patients.
Conclusion
Our findings suggest that initial LL and SI are straightforward and appropriate tools to predict the risk of mechanical ventilation, vasoactive drug use, hospitalization, and in-hospital mortality among emergency patients. LL and SI have approximately similar roles in identifying the risk of mechanical ventilation, vasoactive drug use, and in-hospital mortality. The risk of hospitalization was better determined by LL. The combination of both parameters was also effective in predicting the outcome measures with a higher sensitivity and NPV. It is easy and fast to obtain LLs and to determine SI during the initial evaluation period in the emergency care settings. This advantage has a role in predicting the outcome of the patients as early as possible. Both tests, especially a combination of the two parameters, should be further evaluated in other studies.
References 1
2
3
4
5
6
7 8
9 10
11
12
13
14
15
16 17
18
19
Acknowledgements Conflicts of interest
There are no conflicts of interest.
20
Khosravani H, Shahpori R, Stelfox HT, Kirkpatrick AW, Laupland KB. Occurrence and adverse effect on outcome of hyperlactatemia in the critically ill. Crit Care 2009; 13:R90. Cerovic´ O, Golubovic´ V, Spec-Marn A, Kremzar B, Vidmar G. Relationship between injury severity and lactate levels in severely injured patients. Intensive Care Med 2003; 29:1300–1305. Manikis P, Jankowski S, Zhang H, Kahn RJ, Vincent JL. Correlation of serial blood lactate levels to organ failure and mortality after trauma. Am J Emerg Med 1995; 13:619–622. Noritomi DT, Soriano FG, Kellum JA, Cappi SB, Biselli PJ, Libo´rio AB, Park M. Metabolic acidosis in patients with severe sepsis and septic shock: a longitudinal quantitative study. Crit Care Med 2009; 37:2733–2739. Rady MY, Smithline HA, Blake H, Nowak R, Rivers E. Comparison of the shock index and conventional vital signs to identify acute, critical illness in the emergency department. Ann Emerg Med 1994; 24:685–690. Talmor D, Jones AE, Rubinson L, Howell MD, Shapiro NI. Simple triage scoring system predicting death and the need for critical care resources f or use during epidemics. Crit Care Med 2007; 35:1251–1256. Liu Y, Liu J, Fang ZA, Shan G, Xu J, Qi Z, et al. Modified shock index and mortality rate of emergency patients. World J Emerg Med 2012; 3:114–117. Kruse O, Grunnet N, Barfod C. Blood lactate as a predictor for in-hospital mortality in patients admitted acutely to hospital: a systematic review. Scand J Trauma Resusc Emerg Med 2011; 19:1–12. Bolton JD. Clinical use of lactate testing in shock states. Semin Anesth Perio M 2007; 26:35–39. Shapiro NI, Howell MD, Talmor D, Nathanson LA, Lisbon A, Wolfe RE, Weiss JW. Serum lactate as a predictor of mortality in emergency department patients with infection. Ann Emerg Med 2005; 45:524–528. Nguyen HB, Rivers EP, Knoblich BP, Jacobsen G, Muzzin A, Ressler JA, Tomlanovich MC. Early lactate clearance is associated with improved outcome in severe sepsis and septic shock. Crit Care Med 2004; 32:1637–1642. Cowan BN, Burns HJ, Boyle P, Ledingham IM. The relative prognostic value of lactate and haemodynamic measurements in early shock. Anaesthesia 1984; 39:750–755. Marecaux G, Pinsky MR, Dupont E, Kahn RJ, Vincent JL. Blood lactate levels are better prognostic indicators than TNF and IL-6 levels in patients with septic shock. Intensive Care Med 1996; 22:404–408. Bilkova D, Motovska Z, Widimsky P, Dvorak J, Lisa L, Budesinsky T. Shock index: a simple clinical parameter for quick mortality risk assessment in acute myocardial infarction. Can J Cardiol 2011; 27:739–742. Lavery RF, Livingston DH, Tortella BJ, Sambol JT, Slomovitz BM, Siegel JH. The utility of venous lactate to triage injured patients in the trauma center. J Am Coll Surg 2000; 190:656–664. Younger JG, Falk JL, Rothrock SG. Relationship between arterial and peripheral venous lactate levels. Acad Emerg Med 1996; 3:730–734. van Beest PA, Mulder PJ, Oetomo SB, van den Broek B, Kuiper MA, Spronk PE. Measurement of lactate in a prehospital setting is related to outcome. Eur J Emerg Med 2009; 16:318–322. Vandromme MJ, Griffin RL, Weinberg JA, Rue LW, Kerby JD. Lactate is a better predictor than systolic blood pressure for determining blood requirement and mortality: could prehospital measures improve traumatriage? J Am Coll Surg 2010; 210:861–869. McNab A, Burns B, Bhullar I, Chesire D, Kerwin A. A prehospital shock index for trauma correlates with measures of hospital resource use and mortality. Surgery 2012; 152:473–476. Sankaran P, Kamath AV, Tariq SM, Ruffell H, Smith AC, Prentice P, Subramanian DN, et al. Are shock index and adjusted shock index useful in predicting mortality and length of stay in community-acquired pneumonia? Eur J Intern Med 2011; 22:282–285.
Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
Elevated lactate level and shock index in nontraumatic hypotensive patients presenting to the emergency department Arif A. Cevik, Hakan Dolgun, Setenay Oner, Baran Tokar, Nurdan Acar, Engin Ozakin and Filiz Kaya Background The aim of our study was to evaluate the effect of lactate level (LL) and shock index (SI) on the outcome in nontraumatic hypotensive patients in the emergency department, and also to show the significance of the combined usage of these two parameters.
(NPV): 100.0%]. Vasoactive drug use was higher in lactate–SI group 1 (32.8%, P < 0.0001, sensitivity: 100.0%, NPV: 100.0%). Lactate–SI group 1 showed a higher hospitalization rate (67.8%, P > 0.05). In-hospital mortality in lactate–SI group 1 was higher (54.1%, P < 0.0001, sensitivity: 100.0%, NPV: 100.0%).
Methods This is a prospective, observational study. Elevated and normal LL (ELL and NLL), elevated and normal SI (ESI and NSI), and a combination of these two parameters (lactate–SI group 1: ELL and ESI, lactate–SI group 2: ELL or ESI, and lactate–SI group 3: NLL and NSI) were evaluated for primary (mortality) and secondary outcome measures.
Conclusion The combination of both parameters is effective in predicting these outcome measures with higher sensitivities and NPVs. Further studies on the subject are required. European Journal of Emergency c 2015 Wolters Kluwer Medicine 22:23–28 Copyright Health, Inc. All rights reserved.
Results A total of 131 patients who fulfilled the inclusion criteria were analysed. Of the patients with ELL, 34.78% were mechanically ventilated (P < 0.001), 31.88% received vasoactive drugs (P < 0.001), and 68.1% were hospitalized (P < 0.01). The mortality rate among patients with ELL was 50.72% (P < 0.001). Of the patients with ESI, 39.42% died (P < 0.01). Use of mechanical ventilation in the emergency department was higher in lactate–SI group 1 [36.1%, P < 0.0001, sensitivity: 100.0%, negative predictive value
Introduction In critically ill patients, elevated lactate level (ELL, >2 mmol/l) was shown to be an independent factor associated with mortality in medical and surgical patients [1,2]. It has been studied in critically ill patients with sepsis, trauma patients, and in those with organ failure in the emergency department (ED) [3]. LL is also a marker used in follow-up of resuscitation success [4]. Shock index (SI) is defined as the heart rate divided by the systolic blood pressure. SI can be a helpful tool, especially when it is abnormal, even when heart rate and blood pressure are in normal ranges [5,6]. SI values ranging from 0.5 to 0.7 are described as normal. It is a suggested marker for predicting the severity of patients, especially when it is over 0.9 [5]. SI has also been used as a marker in emergency patients with sepsis, trauma patients and in those with some other serious condition. However, the majority of the studies were on trauma patients. There are insufficient data in the literature indicating whether SI can be used in all emergency patients regardless of diagnosis, particularly in nontraumatic patients [7]. c 2015 Wolters Kluwer Health, Inc. All rights reserved. 0969-9546 Copyright
European Journal of Emergency Medicine 2015, 22:23–28 Keywords: emergency, hypotension, lactate level, shock index Department of Emergency Medicine, Eskisehir Osmangazi University, Meselik, Eskisehir, Turkey Correspondence to Arif A. Cevik, MD, Department of Emergency Medicine, Eskisehir Osmangazi University, Meselik, 26440 Eskisehir, Turkey Tel: + 90 222 2392979; fax: + 90 222 2393774; e-mail: [email protected] Received 6 May 2013 Accepted 10 December 2013
To predict the outcome in emergency patients, several markers can be used in the ED. LL and SI were suggested to be valuable parameters in predicting the severity of patients. However, the majority of research has been conducted on patients with specific diagnoses such as sepsis, trauma and severe infection. There is a need for studies designed to investigate the value of these parameters in ED patients regardless of diagnosis. The data obtained from these studies may help establish the criteria that can be used to predict the outcome in the beginning of the evaluation process in the ED. These parameters have been studied separately, and according to our knowledge combinations of these two parameters in nontraumatic patients have not been studied yet. A prospective study evaluating these two parameters together may yield some significant findings. In this study, the aim was to evaluate the effect of LL and SI on the outcome in nontraumatic hypotensive patients in the ED. We also aimed to show the significance of the combination of these two parameters. DOI: 10.1097/MEJ.0000000000000110
Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
24 European Journal of Emergency Medicine 2015, Vol 22 No 1
Methods Hospital
This prospective observational study was conducted in the ED of a university hospital in central Anatolia, Turkey. The hospital is a 1200-bed, urban, academic, tertiary care hospital and has medical, surgical, coronary, neurological and paediatric ICUs with 120 beds.
Patients
The ED had 653 nontraumatic hypotensive patients in the year 2012. We applied 5% error and 95% confidence level, and expected 90% correct results in calculating the minimum number of patients in the study (n = 115). After reviewing data from the hospital, we assumed that a 4-month period would give us enough number of cases. The patients who presented to the ED with hypotension (systolic blood pressure of 90 mmHg or less) during the 4-month period were included in the study. Patients over 18 years of age were selected.
Inclusion and exclusion criteria
Nontraumatic patients who were diagnosed as hypotensive were eligible for the study. Trauma patients and those with known hepatic or renal failure, haematologic cancers, and out-of-hospital cardiac arrest were excluded. Patients who were sent to the operating theatre directly from the ED before taking the blood samples and those who refused to participate in the study were also excluded.
Measurement of lactate level and calculation of shock index
LLs of initial venous blood samples were measured [8] using a Radiometer ABL800 FLEX analyser (Radiometer Medical, Bronshoj, Denmark). The measuring range of the analyser for lactate is 0.0–30.0 mmol/l. LLs that were reported as out of measurement range of the analyser were excluded from the analysis. SI was calculated as the heart rate divided by the systolic blood pressure. The patients were admitted to the monitored bed unit of the ED. In the first 5 min of medical evaluation, LL was evaluated in the first sample of venous blood and SI was calculated from the first blood pressure measurement during this period. Blood samples for the evaluation of LL and measurement of SI were obtained before all invasive procedures (intubation, mechanical ventilation, etc.) or treatments (vasoactive drug, etc.). Lactate level and shock index subgroups
LLs and SI were categorized on the basis of the cutoff levels in the literature. LLs of the patients were categorized as 2 mmol/l or less [normal lactate level (NLL)] and greater than 2 mmol/l (ELL). SI of the patients was categorized as 0.9 or less [normal SI group (NSI)] and over 0.9 [elevated SI group (ESI)]. The patients with both ELL and ESI belonged to lactate–SI group 1. The patients with only one elevated parameter belonged to lactate–SI group 2. Patients with both NLL and NSI belonged to lactate–SI group 3. Outcome measures
Data acquisition
Descriptive data of patients including age, sex, vital signs, level of consciousness (Glasgow Coma Scale), haematological and biochemical test results such as LL, SI, intubation and mechanical ventilation and/or vasopressor agent use in the ED, hospitalization and mortality were recorded. Data were acquired by the ED team (attending physician, emergency medicine residents and nurses) who were trained on the data parameters of the research. Complete history was taken and full physical examination was performed by the attending physician and/or the senior emergency medicine residents in the ED. Additional laboratory or radiological tests were conducted as necessary.
Written consent procedure
Written consent was received from the patients or their family members depending on the level of consciousness and co-operation of the patients. Blood samples for estimation of LL and calculation of SI were obtained from all eligible patients in the first 5 min of the medical evaluation. Data used in this study are from patients who provided consent.
In-hospital mortality was the main outcome measure of the study. Need for mechanical ventilation in the ED, vasoactive drug use in the ED and hospitalization were defined as secondary outcome measures. The clinicians responsible for patient care did not use LLs and/or SI in decision-making. In-hospital mortality was described as mortality in the ED and in-hospital ward or ICU during a month. Statistical analyses
The Kolmogorov–Smirnov test was used to show the normality distribution of the data. The Mann–Whitney U-test in binary groups was used as the data did not show a normal distribution, and the results of variables were presented as median values with interquartile ranges (IQRs). Independent samples t-test was used for normally distributed data. The w2-test and Fisher’s exact test were used for frequency distribution analyses. Mean values were described in terms of standard error (SE) of means as appropriate. SPSS, version 18 (SPSS Inc., Chicago, Illinois, USA) was used for statistical analyses. Sensitivity, specificity, positive predictive value (PPV) and negative predictive values (NPV) in groups for outcome measures were defined. Odds ratios (ORs) with 95% confidence intervals (CI) were reported as appropriate.
Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
Elevated lactate level and shock index Cevik et al. 25
Ethics and governance
The study was commenced after obtaining approval from the Research Ethics and Review Board of the University Medical Centre.
Results There were 177 hypotensive patients during study period; 46 patients were excluded because of the following reasons: hepatic failure (five patients), renal failure (12 patients), haematologic cancer (12 patients), out-of-hospital cardiac arrest (four patients) and trauma (13 patients). No patient refused consent. LL was not reported by the analyser as it was out of the measurement range. A total of 131 patients who fulfilled the inclusion criteria were included for statistical analysis. Descriptive data with lactate levels and shock index
The mean age of the patients was 62.35±1.63 years (18–100 years, median: 68 years). The number of men was 77 (58.8%). There were 69 patients with ELL and 62 patients with NLL. The mean LL was found to be 2.66± 0.35 mmol/l among the women and 3.44±0.42 mmol/l among the men (P > 0.05). Of the patients, 104 had ESI and 27 had NSI. The mean SI was higher among female patients (1.48±0.09 vs. 1.31±0.06; P > 0.05). Outcome measures according to lactate levels
Outcome measures according to LLs are shown in Table 1. Details of the data are described as follows.
rate was 3.22% (two patients) among patients with NLL (P < 0.001). The risk of vasoactive drug use in the patients with ELL (OR: 14.043, 95% CI 3.143–62.748) was higher than that among NLL patients (sensitivity: 91.67%, 95% CI 72.96–98.73%; specificity: 56.07%, 95% CI 46.15–65.66%; PPV: 31.88%, 95% CI 21.18–44.21%; NPV: 96.77%, 95% CI 88.80–99.51%). Hospitalization
Of the patients, 75 were hospitalized in the study: 47 (68.1%) with ELL and 28 (45.2%) with NLL (P < 0.01). Patients with ELL showed a higher risk for hospitalization (OR: 2.594, 95% CI 1.273–5.285) compared with patients with NLL (sensitivity: 62.67%, 95% CI 50.73–73.57%; specificity: 60.71%, 95% CI 46.75–73.50%; PPV: 68.12%, 95% CI 55.79–78.82%; NPV: 54.84%, 95% CI 41.68–67.52%). Mortality
There were 43 in-hospital deaths. The mortality rate among patients with ELL was 50.72% (35 patients), whereas it was 12.90% (eight patients) in the NLL group (P < 0.001). Patients with ELL showed a higher risk (OR: 6.949, 95% CI 2.883–16.749) than patients with NLL for in-hospital mortality (sensitivity: 81.40%, 95% CI 66.59–91.58%; specificity: 61.36%, 95% CI 50.38–71.56%; PPV: 50.72%, 95% CI 38.41–62.98%; NPV: 87.10%, 95% CI 76.14–94.24%). Outcome measures according to shock index
Mechanical ventilation use in the emergency department
A total of 26 patients needed intubation and mechanical ventilation in the ED. Of the patients with ELL, 24 (34.78%) were mechanically ventilated (P < 0.001). The risk of mechanical ventilation in the ED was higher among patients with ELL (OR: 16.0, 95% CI 3.594–71.234) than among those with NLL (sensitivity: 92.31%, 95% CI 74.83–98.83%; specificity: 57.14%, 95% CI 47.11–66.76%; PPV: 34.78%, 95% CI 23.71–47.21%; NPV: 96.77%, 95% CI 88.80–99.51%).
Outcome measures according to SI are shown in Table 2. Details of the data are described as follows. Mechanical ventilation use in the emergency department
Of the patients, 26 were mechanically ventilated in the ED: 22 (92.30%) belonged to the ESI group. However, only 24 of 104 patients with ESI (23.07%) were intubated and mechanically ventilated, whereas intubation rate was 7.40% (two patients) in the NSI group (P > 0.05).
Vasoactive drug use in the emergency department
Vasoactive drug use in the emergency department
Vasoactive drugs were used in 24 patients (18.32%) in the ED: 22 of those patients (91.66%) had ELL and ESI. The percentage of patients with ELL who received vasoactive drugs in the ED was 31.88% (22 patients), whereas this
Of the patients, 24 received vasoactive drugs: 22 of 104 patients with ESI (21.15%) received vasoactive drugs in the ED, whereas this rate was 7.40% (two patients) in the NSI group (P > 0.05).
Table 1
Lactate levels and outcome measures Lactate > 2 mmol/l [N (% in group)]
Mechanical ventilation Vasoactive drug use Hospitalization In-hospital death
24 22 47 35
(34.8) (31.9) (68.1) (50.72)
Lactate r 2 mmol/l [N (% in group)] 2 2 28 8
(3.2) (3.2) (45.2) (12.9)
Sensitivity (%)
Specificity (%)
PPV (%)
NPV (%)
OR
P-value
92.31 91.67 62.67 81.40
57.14 56.07 60.71 61.36
34.78 31.88 68.12 50.72
96.77 96.77 54.84 87.10
16.0 14.043 2.594 6.949
< 0.001 < 0.001 < 0.01 < 0.001
NPV, negative predictive value; OR, odds ratio; PPV, positive predictive value.
Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
26 European Journal of Emergency Medicine 2015, Vol 22 No 1
Table 2
Shock index and outcome measures SI r 0.9 [N (% in group)]
SI > 0.9 [N (% in group)] Mechanical ventilation Vasoactive drug use Hospitalization In-hospital death
24 22 58 41
(23.1) (21.2) (55.8) (39.42)
2 2 17 2
Sensitivity (%)
Specificity (%)
PPV (%)
NPV (%)
OR
P-value
92.31 91.67 77.33 95.35
23.81 23.36 17.86 28.41
23.03 21.15 55.77 39.42
92.59 92.59 37.04 92.59
3.750 3.354 0.742 8.135
> 0.05 > 0.05 > 0.05 < 0.01
(7.4) (7.4) (63.0) (7.4)
NPV, negative predictive value; OR, odds ratio; PPV, positive predictive value; SI, shock index.
Table 3
Lactate–shock index groups and outcome measures Lactate–SI group 1 [N (% in group)]a
Mechanical ventilation Vasoactive drug use Hospitalization In-hospital death
22 20 40 33
(36.1) (32.8) (67.8) (54.1)
Lactate–SI group 2 [N (% in group)]a 4 4 25 10
(7.8) (7.8) (49.0) (19.6)
Lactate–SI group 3 [N (% in group)]a 0 0 10 0
(0.0) (0.0) (52.6) (0.0)
Sensitivity (%)
Specificity (%)
PPV (%)
NPV (%)
OR
P-value
100.00 100.00 80.00 100.00
32.76 31.67 32.14 40.43
36.07 32.79 67.80 54.10
100.00 100.00 47.37 100.00
1.56 1.48 1.895 2.179
< 0.0001 < 0.0001 > 0.05 < 0.0001
a
Lactate–SI group 1, patients with high LL ( > 2 mmol/l) and high SI ( > 0.9); lactate–SI group 2, patients with high LL ( > 2 mmol/l) or high SI ( > 0.9); lactate–SI group 3, patients with normal LL (r 2 mmol/l) and normal SI (r 0.9). LL, lactate level; NPV, negative predictive value; OR, odds ratio; PPV, positive predictive value; SI, shock index.
Hospitalization
Hospitalization rate was 55.8% (58 patients) among patients with ESI, whereas the rate was 63.0% (17 patients) among patients with NSI (P > 0.05). Mortality
Of 104 patients with ESI, 41 (39.42%) died in the hospital, whereas the in-hospital mortality rate was 7.40% (two patients) among patients with NSI (P < 0.01). The risk for in-hospital mortality was higher among patients with ESI (OR: 8.135, 95% CI 1.828–36.204) than among those with NSI (sensitivity: 95.35%, 95% CI 84.16–99.30; specificity: 28.41%, 95% CI 19.30–39.02%; PPV: 39.42%, 95% CI 29.98–49.49%; NPV: 92.59%, 95% CI 75.67–98.88%). Outcome measures with group analysis
Outcome measures according to the study groups (lactate–SI groups 1, 2 and 3) are shown in Table 3. Details of the data are described as follows. We designed three study groups: in lactate–SI group 1 the patients had both ELL and ESI; in lactate–SI group 2 the patients had ELL or ESI; in lactate–SI group 3 the patients had both NLL and NSI. There were 61 patients in lactate–SI group 1, 51 patients in lactate–SI group 2, and 19 patients in lactate–SI group 3. Glasgow Coma Scale scores were lower in lactate–SI group 1 (median: 14, IQR: 6) compared with lactate–SI group 2 (median: 15, IQR: 0) and lactate–SI group 3 (median: 15, IQR: 0; P < 0.001).
PPV: 36.07%, 95% CI 24.16–49.37%; NPV: 100.0%, 95% CI 82.20–100.0%; and OR: 1.56, 95% CI 1.29–1.89. Vasoactive drug use in the emergency department
Vasoactive drug use was significantly higher in lactate–SI group 1 (20 patients, 32.8%, P < 0.0001) than in lactate– SI group 2 (four patients, 7.8%) and lactate–SI group 3 (0.0%). Comparison of lactate–SI groups 1 and 3 yielded the following results: sensitivity: 100.0%, 95% CI 83.01–100.0%; specificity: 31.67%, 95% CI 20.26–44.96%; PPV: 32.79%, 95% CI 21.31–46.00%; NPV: 100.0%, 95% CI 82.20–100.0%; and OR: 1.48, 95% CI 1.25–1.77. Hospitalization
Lactate–SI group 1 showed a higher hospitalization rate than lactate–SI group 2 and lactate–SI group 3 [40 patients (67.8%) vs. 25 patients (49.0%) and 10 patients (52.6%); P > 0.05]. Mortality
In-hospital mortality in lactate–SI group 1 was significantly higher than in lactate–SI group 2 and lactate–SI group 3 [33 patients (54.1%) vs. 10 patients (19.6%) and 0.0%; P < 0.0001]. Comparison of lactate–SI groups 1 and 3 yielded the following results: sensitivity: 100.00%, 95% CI 89.32–100.00%; specificity: 40.43%, 95% CI 26.38–55.73%; PPV: 54.10%, 95% CI 40.85–66.93%; NPV: 100.00%, 95% CI 82.20–100.00%; and OR: 2.18, 95% CI 1.67–2.86.
Mechanical ventilation use in the emergency department
Data of discharged patients
Mechanical ventilation use was significantly higher in lactate–SI group 1 (22 patients, 36.1%, P < 0.0001) than in lactate–SI group 2 (four patients, 7.8%) and lactate–SI group 3 (0.0%). Comparison of lactate–SI groups 1 and 3 yielded the following results: sensitivity: 100.0%, 95% CI 84.43–100.0%; specificity: 32.76%, 95% CI 21.01–46.34%;
A total of 56 patients were discharged from the ED. Nine of these patients revisited the ED within a 1-month period. Seven of nine patients were discharged from the ED. One patient was admitted and discharged from the ward, and one patient was admitted to the nephrology clinic and died because of renal failure complications.
Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
Elevated lactate level and shock index Cevik et al. 27
Patients who were admitted and discharged and the patient who died in the clinic had NLL and NSI during their first visit to the ED.
Discussion Lactate is always present in circulation at a low level (B1 mmol/l). The multiple hypoxic organs produce more lactate than that produced on metabolism during a shock state, and LLs increased. A current trend in emergency medicine and intensive care is to use LL in the initial assessment of the acutely ill or injured patients [9]. Initial and/or serial LLs have been used to predict mortality in general ED patients, as well as a shock of any cause [10–13]. The SI is calculated by dividing the heart rate by the systolic blood pressure. An SI ranging from 0.5 to 0.7 is normal. SI is a marker that could be used to predict the severity of the patients, especially when it is over 0.9 [5]. Although the majority of the studies on SI include traumatic patients, it has been used in emergency patients presenting with sepsis and some other serious condition. An ESI helps identify the severity of the patient’s condition before hemodynamic deterioration [14]. Therefore, SI could be considered as an appropriate triage tool for ED patients. The majority of the studies on LL and SI evaluate their relationship with mortality, especially in trauma and sepsis. The correlation of LL and SI with the need for mechanical ventilation, vasoactive drug use, and hospitalization were shown in a limited number of reports. The combination of LL and SI for emergency patients was not studied in the literature. The values of these parameters in ED patients, regardless of diagnosis, may help determine the severity of the condition in the early phase of emergency medical care. It is easy and fast to obtain LLs and to determine SI; hence these parameters can be used in risk stratification during the initial evaluation of the patients in the ED. The golden standard in determining LL is to measure the level in an arterial blood sample. However, arterial puncture can be a time-consuming and painful procedure. Therefore, we prefer to use peripheral venous LL on the basis of the findings of Lavery et al. [15], who showed no significant difference between arterial and venous LLs and reported a high correlation rate (r = 0.988). However, there are some studies showing overestimation of venous LL (bias 0.18 mmol/l, 95% CI 0.012–0.372) [16]. Although there are some discrepancies with regard to the appropriate reference interval and whether to perform single or serial lactate measurements [8], we used 2 mmol/l as a cutoff level and obtained a single LL to predict the outcome. Our approach is correlated with the literature findings [1,2]. The results of our study showed that nontraumatic hypotensive ED patients with an initial ELL (> 2 mmol/l) needed significantly more mechanical ventilation, higher vasoactive drug administration, and longer hospitalization, and the mortality rate
was higher among these patients. The mortality rate was 50.72% in the patients with ELL, and the OR was 6.94 in our study. Khosravani et al. [1] reported that an LL higher than 2 mmol/l was a significant independent predictor of mortality, and in this report, OR was up to 10.89 depending on the level of lactate. In addition to inhospital mortality as the primary outcome measure, secondary outcome measures such as mechanical ventilation, vasoactive drug use and hospitalization were also related with ELL. However, we could not find a study in the literature to compare our results with in terms of secondary outcomes. Some studies demonstrated that ELL has a significant effect on length of stay in the hospital and need for blood transfusion as secondary outcome measures [17,18]. According to the current literature, when the value of SI is over 0.9 it is considered to be elevated [5]. Our results showed that nontraumatic hypotensive ED patients with an initial ESI (> 0.9) have a significantly higher mortality rate than the NSI group. Although sensitivity and NPV were higher than lactate levels, we could not demonstrate a significant relationship between SI and mechanical ventilation, vasoactive drug use and hospitalization as we found in lactate. Correlation of these secondary outcome measures with SI has not been well described in the literature. In contrast, ESI in the early period of emergency care indicated a higher likelihood of disposition to ICU admission, surgery, or death [19]. Mortality rate was 39.42% in patients with ESI, and the OR was 8.13 in our study. Bilkova et al. [14] reported that ESI was an independent risk factor for mortality, and they found the OR to be as high as 81.26 (95% CI 9.76–676.51; P < 0.001). They found 20.3% mortality in the ESI group, compared with 4% in the low SI group. The mortality rate in the NSI group in our study was 7.4%. Another study that evaluated SI in patients with community-acquired pneumonia found that the OR of the elevated SI for 30 days mortality was 2.48 (1.04–5.92; P = 0.04) [20]. We used two parameters to designate the groups as lactate–SI group 1, lactate–SI group 2 and lactate–SI group 3. The patients with both ELL and ESI (lactate– SI group 1) had a significantly higher rate of mechanical ventilation, vasoactive drug use and mortality than patients who had normal parameters (lactate–SI group 3). Our study showed that the combination of the two parameters increased sensitivity and NPVs on all outcome measures. In addition, the patients who had normal levels of these two parameters (19 patients) did not receive mechanical ventilation and vasoactive drugs, and inhospital mortality was not determined for these patients.
Limitations
This is a single-centre prospective study. Hospitalization decisions taken on the basis of institutional or departmental guidelines have played a role in hospital admission.
Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
28 European Journal of Emergency Medicine 2015, Vol 22 No 1
Multicentre prospective studies may decrease this effect and increase the sample size. In addition, we faced difficulty in finding articles to compare our secondary survey results with, especially for mechanical ventilation and vasoactive drug use. There was no report in the literature on using a combination of both parameters, as we did in our study. The study was limited to nontrauma patients, and 13 trauma patients were excluded. Further, 33 nontrauma patients were excluded because of the possible effects of accompanying diseases on LLs. Heart rate is controlled by many medications. The elderly are expected to be on rate-limiting medication, such as calcium channel antagonists, b-blockers and other medications that would change the SI. Hypotension and shock in the ED occur because of cardiogenic, hypovolemic, distributive and obstructive problems. Using a limited set of physiological data, the use of LL and SI as predictors may still be questionable. However, we believe that SI and LL needed to be evaluated to predict outcome regardless of diagnosis of the ED patients.
Conclusion
Our findings suggest that initial LL and SI are straightforward and appropriate tools to predict the risk of mechanical ventilation, vasoactive drug use, hospitalization, and in-hospital mortality among emergency patients. LL and SI have approximately similar roles in identifying the risk of mechanical ventilation, vasoactive drug use, and in-hospital mortality. The risk of hospitalization was better determined by LL. The combination of both parameters was also effective in predicting the outcome measures with a higher sensitivity and NPV. It is easy and fast to obtain LLs and to determine SI during the initial evaluation period in the emergency care settings. This advantage has a role in predicting the outcome of the patients as early as possible. Both tests, especially a combination of the two parameters, should be further evaluated in other studies.
References 1
2
3
4
5
6
7 8
9 10
11
12
13
14
15
16 17
18
19
Acknowledgements Conflicts of interest
There are no conflicts of interest.
20
Khosravani H, Shahpori R, Stelfox HT, Kirkpatrick AW, Laupland KB. Occurrence and adverse effect on outcome of hyperlactatemia in the critically ill. Crit Care 2009; 13:R90. Cerovic´ O, Golubovic´ V, Spec-Marn A, Kremzar B, Vidmar G. Relationship between injury severity and lactate levels in severely injured patients. Intensive Care Med 2003; 29:1300–1305. Manikis P, Jankowski S, Zhang H, Kahn RJ, Vincent JL. Correlation of serial blood lactate levels to organ failure and mortality after trauma. Am J Emerg Med 1995; 13:619–622. Noritomi DT, Soriano FG, Kellum JA, Cappi SB, Biselli PJ, Libo´rio AB, Park M. Metabolic acidosis in patients with severe sepsis and septic shock: a longitudinal quantitative study. Crit Care Med 2009; 37:2733–2739. Rady MY, Smithline HA, Blake H, Nowak R, Rivers E. Comparison of the shock index and conventional vital signs to identify acute, critical illness in the emergency department. Ann Emerg Med 1994; 24:685–690. Talmor D, Jones AE, Rubinson L, Howell MD, Shapiro NI. Simple triage scoring system predicting death and the need for critical care resources f or use during epidemics. Crit Care Med 2007; 35:1251–1256. Liu Y, Liu J, Fang ZA, Shan G, Xu J, Qi Z, et al. Modified shock index and mortality rate of emergency patients. World J Emerg Med 2012; 3:114–117. Kruse O, Grunnet N, Barfod C. Blood lactate as a predictor for in-hospital mortality in patients admitted acutely to hospital: a systematic review. Scand J Trauma Resusc Emerg Med 2011; 19:1–12. Bolton JD. Clinical use of lactate testing in shock states. Semin Anesth Perio M 2007; 26:35–39. Shapiro NI, Howell MD, Talmor D, Nathanson LA, Lisbon A, Wolfe RE, Weiss JW. Serum lactate as a predictor of mortality in emergency department patients with infection. Ann Emerg Med 2005; 45:524–528. Nguyen HB, Rivers EP, Knoblich BP, Jacobsen G, Muzzin A, Ressler JA, Tomlanovich MC. Early lactate clearance is associated with improved outcome in severe sepsis and septic shock. Crit Care Med 2004; 32:1637–1642. Cowan BN, Burns HJ, Boyle P, Ledingham IM. The relative prognostic value of lactate and haemodynamic measurements in early shock. Anaesthesia 1984; 39:750–755. Marecaux G, Pinsky MR, Dupont E, Kahn RJ, Vincent JL. Blood lactate levels are better prognostic indicators than TNF and IL-6 levels in patients with septic shock. Intensive Care Med 1996; 22:404–408. Bilkova D, Motovska Z, Widimsky P, Dvorak J, Lisa L, Budesinsky T. Shock index: a simple clinical parameter for quick mortality risk assessment in acute myocardial infarction. Can J Cardiol 2011; 27:739–742. Lavery RF, Livingston DH, Tortella BJ, Sambol JT, Slomovitz BM, Siegel JH. The utility of venous lactate to triage injured patients in the trauma center. J Am Coll Surg 2000; 190:656–664. Younger JG, Falk JL, Rothrock SG. Relationship between arterial and peripheral venous lactate levels. Acad Emerg Med 1996; 3:730–734. van Beest PA, Mulder PJ, Oetomo SB, van den Broek B, Kuiper MA, Spronk PE. Measurement of lactate in a prehospital setting is related to outcome. Eur J Emerg Med 2009; 16:318–322. Vandromme MJ, Griffin RL, Weinberg JA, Rue LW, Kerby JD. Lactate is a better predictor than systolic blood pressure for determining blood requirement and mortality: could prehospital measures improve traumatriage? J Am Coll Surg 2010; 210:861–869. McNab A, Burns B, Bhullar I, Chesire D, Kerwin A. A prehospital shock index for trauma correlates with measures of hospital resource use and mortality. Surgery 2012; 152:473–476. Sankaran P, Kamath AV, Tariq SM, Ruffell H, Smith AC, Prentice P, Subramanian DN, et al. Are shock index and adjusted shock index useful in predicting mortality and length of stay in community-acquired pneumonia? Eur J Intern Med 2011; 22:282–285.
Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
