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Low End-Tidal Carbon Dioxide at the Onset of Emergent Trauma Surgery Is Associated With Nonsurvival: A Case Series

Dudaryk, Roman MD*; Bodzin, Danielle K. MD*; Ray, Juliet J. MD, MSPH; Jabaley, Craig S. MD; McNeer, Richard R. MD, PhD*; Epstein, Richard H. MD*

doi: 10.1213/ANE.0000000000002283
Trauma: Original Clinical Research Report
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BACKGROUND: End-tidal carbon dioxide (Etco2) is a valuable marker of the return of adequate circulation after cardiac arrest due to medical causes. Previously, the prognostic value of capnography in trauma has been studied among limited populations in prehospital and emergency department settings. We aimed to investigate the relationship between early intraoperative Etco2 and nonsurvival of patients undergoing emergency surgery at a level 1 academic trauma center as a case series. If there is a threshold below which survival was extremely unlikely, it might be useful in guiding decision-making in the early termination of futile resuscitative efforts.

METHODS: After institutional review board approval, a data set was created to investigate the relationship between Etco2 values at the onset of emergent trauma surgery and nonsurvival. Patients who were admitted and transferred to the operating room (OR) directly from a resuscitation bay were identified using the Ryder Center trauma registry (October 1, 2013, to June 30, 2016). Electronic records from the hospital’s anesthesia information management system were queried to identify the matching anesthesia records. The maximum Etco2 values within 5 and 10 minutes of the onset of mechanical ventilation in the OR were determined for patients undergoing general anesthesia with mechanical ventilation. Patients were divided into 2 groups: those who were discharged from the hospital alive (survivors) and those who died in the hospital before discharge (nonsurvivors). The threshold Etco2 giving a positive predictive value of 100% for in-hospital mortality was determined from a graphical analysis of the data. Association of determined threshold and mortality was analyzed using the 2-tailed Fisher exact test.

RESULTS: There were 1135 patients who met the inclusion criteria. Within the first 5 minutes of the onset of mechanical ventilation in the OR, if the maximum Etco2 value was ≤20 mm Hg, hospital mortality was 100% (21/21, 95% binomial confidence interval, 83.2%–100%).

CONCLUSIONS: A maximum Etco2 ≤20 mm Hg within 5 minutes of the onset of mechanical ventilation in the OR may be useful in decision-making related to the termination of resuscitative efforts during emergent trauma surgery. However, a large-scale study is needed to establish the statistical reliability of this finding before potential adoption.

Published ahead of print July 10, 2017.

From the *Department of Anaesthesiology, Jackson Memorial Hospital, Miami, Florida; DeWitt Daughtry Family Department of Surgery, University of Miami Miller School of Medicine, Miami, Florida; and Department of Anesthesiology, Division of Critical Care Medicine, Emory University School of Medicine, Atlanta, Georgia.

Accepted for publication May 17, 2017.

Published ahead of print July 10, 2017.

Funding: None.

The authors declare no conflicts of interest.

Reprints will not be available from the authors.

Address correspondence to Roman Dudaryk, MD, Department of Anesthesiology, University of Miami, Ryder Trauma Center, 1800 NW 10th Ave (M 820) T-239, Miami, FL 33156. Address e-mail to rdudaryk@miami.edu.

Trauma is a leading cause of death in those younger than 44 years throughout the world.1 In the United States alone, the financial toll of injuries was estimated at $671 billion in 2013.2 Concerns regarding utilization of resources bear greatly on how to best treat trauma victims, particularly those with the gravest injuries who will succumb despite aggressive resuscitation. Therefore, early identification of patients with nonsurvivable injuries has appreciable clinical utility.3–5

Among trauma patients who are alive on hospital arrival, hemorrhagic shock accounts for 82% of all mortality within the first 24 hours after admission, despite ongoing resuscitation.6 Fatal hemorrhage invariably terminates with a profound decrease in cardiac output due to hypovolemic shock. Because exhaled end-tidal carbon dioxide (Etco2), measured via capnography, indirectly reflects pulmonary blood flow and cardiac output, Etco2 falls during shock states. Capnography has a well-recognized value during resuscitation after cardiac arrest due to medical causes as it helps gauge the adequacy of resuscitative efforts and can herald the return of spontaneous circulation.7 Recognizing its value in situations when adequate circulation is difficult to assess, quantitative capnography has been incorporated into American Heart Association Advanced Cardiac Support Guidelines (AHA ACLS Guidelines).

In the trauma patient population, the prognostic value of capnography has been examined in the prehospital and emergency department (ED) settings. In a group of young nonintubated patients with penetrating trauma, Etco2 sampled via nasal cannulas correlated with lactate levels and was prognostic of the need for operative intervention.8 An Etco2 level of <24 mm Hg in blunt trauma patients requiring prehospital intubation was predictive of mortality.9 An Etco2 to arterial Pco2 difference >10 mm Hg at the end of resuscitation, likewise, has been associated with mortality.10,11

We are unaware of any studies evaluating intraoperative Etco2 at the onset of surgery immediately after patient transport to a level 1 trauma center as a prognostic factor for survival. The purpose of this retrospective study was to test our clinical impression that early low Etco2 in mechanically ventilated patients undergoing emergency surgery for trauma is associated with nonsurvival. If a threshold Etco2 value was found below which survival is highly unlikely, it would help refine the decision-making process for early termination of futile resuscitative efforts.

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METHODS

The Institutional Review Boards of the University of Miami and Jackson Memorial Hospital approved this study with a waiver of informed consent.

The Ryder Trauma Center Registry was queried to identify patients who arrived in the ED resuscitation bays between October 1, 2013, and September 30, 2015, and went directly to the operating room (OR) without first being admitted to an inpatient bed. Data from the registry included patient name, medical record number, age, sex, race, ethnicity, Glasgow Coma Scale, Trauma Score, Injury Severity Score, total length of stay, in-hospital mortality, time from dispatch of emergency services to ED arrival, injury type (blunt or penetrating), and mode of transport (private or rescue vehicle). Electronic records from the hospital’s anesthesia information management system (PICIS Clinical Solutions, Wakefield, MA) were queried to identify the matching anesthesia records for the emergency surgery. Matching was complex and involved multiple parameters, including patient names (many misspelled or listed as “unknown”), medical record number (some incorrectly entered or missing), dates (some incorrectly listed), OR location, and manual inspection of anesthesia records and the hospital’s enterprise electronic health record (PowerChart 4.2.1; Cerner, Kansas City, MO). All patients in the trauma registry were ultimately identified, with several determined not to have gone to the OR emergently or only having a paper anesthesia record. Time-stamped Etco2 values, ventilation mode, tidal volume, and peak inspiratory pressures were retrieved. The maximum Etco2 values within 5 and 10 minutes of the onset of mechanical ventilation in the OR were determined for patients undergoing general anesthesia. Cases excluded from the analysis are listed in Figure 1. Patients were divided into 2 groups: those who were discharged from the hospital alive (survivors) and those who died during their hospitalization (nonsurvivors).

Figure 1.

Figure 1.

Data relating to intraoperative transfusion were collected for nonsurvivors who had a maximum Etco2 ≤20 mm Hg within 5 minutes of the onset of mechanical ventilation. The total amount of intraoperatively transfused packed red blood cells and fresh frozen plasma (FFP) were gathered.

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Statistical Methods

A power analysis was not performed as this was an exploratory retrospective case series intended to confirm our clinical impression and determine the sample size needed for a multicenter follow-up study. Patient demographics and transport times were compared using a χ2 test with Dunn-Šidák correction for multiple comparisons among these parameters. The primary outcome was in-hospital mortality. The 2-sided Student t test was used to compare the differences between survivors and nonsurvivors for the maximal Etco2 within 5 and 10 minutes of the onset of mechanical ventilation in the OR. The highest Etco2 for a positive predictive value of 100% for in-hospital mortality was determined from a graphical evaluation of the data. Association of determined threshold and mortality was analyzed using the 2-tailed Fisher exact test. Descriptive data are presented as the mean ± SD with the interquartile range (IQR) listed for ventilation parameters. Systat version 13 (Systat Software, San Jose, CA) was used for all statistical tests. A corrected P value <.05 was required to claim statistical significance.

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RESULTS

There were 1135 patients who met the inclusion criteria (Figure 1). Overall mortality was 13.1% (95% binomial confidence interval [CI], 11.2%–15.2%). Patients who died during their hospitalization were sicker as judged by their initial Glasgow Coma Scale, Trauma Score, or Injury Severity Score (Table 1). However, transport times from initial dispatch of the rescue team until the patient arrived in the trauma resuscitation bay did not differ between survivors and nonsurvivors (Table 1).

Table 1.

Table 1.

If the maximum Etco2 value was ≤20 mm Hg within the first 5 minutes of the onset of mechanical ventilation in the OR, in-hospital mortality was 100% (21/21; 95% binomial CI, 83.2%–100%; P < .001; Figure 2; Table 2). If the maximum Etco2 value was ≤20 mm Hg within the first 10 minutes of the onset of mechanical ventilation in OR, hospital mortality was also 100% (11/11; 95% binomial CI, 71.5%–100%; P < .001; Figure 3; Table 3).

Table 2.

Table 2.

Table 3.

Table 3.

Figure 2.

Figure 2.

Figure 3.

Figure 3.

Nonsurvivors with maximum Etco2 ≤ 20 mm Hg within 5 minutes of the onset of mechanical ventilation in the OR had a mean respiratory rate of 12.9 ± 3.7 breaths per minute (IQR, 10–15 breaths per minute), and a mean tidal volume of 476 ± 140 mL (IQR, 413–558 mL). There was no difference in minute ventilation between patients who expired in the OR (all with maximum Etco2 ≤20 mm Hg within 5 minutes of the onset of mechanical ventilation) and those who left the OR alive, 6.4 ± 2.0 vs 6.5 ± 1.7 L/min, respectively (P = .83). The difference between the means of the maximum Etco2 within 5 minutes of the onset of mechanical ventilation in the OR of nonsurvivors and survivors was −9.0 mm Hg (95% CI, −10.2 to −7.7 mm Hg; P < 10–6).

Of the patients with maximum Etco2 ≤20 mm Hg within 5 minutes of the onset of mechanical ventilation in the OR, the majority died in the OR, and none survived >3 days postoperatively (Table 4).

Table 4.

Table 4.

Among the 21 nonsurvivors with maximum Etco2 ≤20 mm Hg within 5 minutes of the onset of mechanical ventilation in the OR, 80% (N = 17) had damage control laparotomy and thoracotomy, 15% (N = 3) underwent thoracotomy only, and 5% (N = 1) underwent laparotomy only.

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Blood Product Use

Among the 21 patients who had a maximum Etco2 ≤20 mm Hg within 5 minutes of the onset of mechanical ventilation in the OR (all of whom were nonsurvivors), the average amounts of packed red blood cells and FFP transfused were 9.4 ± 9.8 and 5.3 ± 5.6 units, respectively. We were unable to determine how much of this blood product use might have been avoided had resuscitative efforts been terminated early, because transfusion documentation frequently is entered into the record after the fact, thus precise timing could not be validated.

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DISCUSSION

Our data indicate that an Etco2 ≤20 mm Hg within 5 minutes of the onset of intraoperative mechanical ventilation after transfer of the patient from the resuscitation bay to the OR was associated with nonsurvival. There was a loss of sensitivity but no improvement in specificity when using a 10-minute interval for Etco2 ≤20 mm Hg. A potential explanation for our findings is that a sustained significantly decreased level of Etco2 that persists despite aggressive resuscitation may reflect a profound degree of circulatory and physiologic derangement precluding successful resuscitation. Over the 12 months since the data in the study were analyzed, among 403 patients similarly presenting to the Ryder Trauma Center, none of the 345 survivors had an initial Etco2 ≤20 mm Hg. However, our data are underpowered to generalize the accuracy of a threshold of 20 mm Hg or the precise interval to be considered as part of the decision-making process to terminate resuscitative efforts and will require confirmation at other centers before potential adoption. To have a binomial 95% upper confidence limit (UCL) of <1% for the misidentification of a trauma survivor based on Etco2 ≤20 mm Hg within 5 minutes of the onset of mechanical ventilation in the OR, a sample size of 372 survivors would be needed at each hospital, assuming 0 survivors were misidentified in the sample (ie, with Etco2 ≤20 mm Hg). If one wished to have a 99% UCL of <1%, 530 survivors would be required. If 1 survivor were allowed to be misidentified, the corresponding 95% and 99% UCL for misidentified survivors <1% would be 560 and 750 patients, respectively. These sample sizes can be used, in conjunction with the number of patients at a trauma center who go directly to the OR, along with the local hospital survival rate, to estimate the number of years of data required to participate in such a multicenter study.

Notably, there was no difference in the transport time (approximately 30 minutes) from the scene of injury to the trauma center between survivors and nonsurvivors. Therefore, the low Etco2 primarily points to profound cardiopulmonary derangement and severity of the injury, as opposed to reflecting delayed retrieval or long transport times. For health care systems with a less rapid delivery of trauma victims to facilities with the capability for immediate resuscitation and surgical intervention, a different Etco2 threshold predictive of nonsurvival is possible, reflecting a longer interval during which the cardiac output was severely depressed.

The mean difference between the maximum Etco2 levels within 5 minutes of the onset of intraoperative mechanical ventilation in nonsurvivors and survivors of trauma was substantial (−9 mm Hg), indicating an overall relationship between low Etco2 and mortality (Figure 1). A recent study done on nonintubated trauma patients in an ED showed minimal difference in Etco2 among various degrees of injury severity, but was underpowered for primary outcome and the patients studied had a significantly lower injury severity than our patient population.12

A study of blunt trauma patients intubated in the prehospital settings demonstrated that Etco2 <25 mm Hg measured 20 minutes after intubation was associated with 95% in-hospital mortality.9 Similar studies demonstrated an association of low Etco2 values with mortality in various trauma groups, but none identified a threshold value below which resuscitative efforts may be futile.8,10,12 More importantly, the previous investigations were performed in a prehospital setting or ED, rather than in an OR, as in our study. These environments are unlikely to have the treatment modalities, expertise, and man power available in the OR of dedicated trauma hospital.13

While previous studies have reported a correlation between low values of Etco2 and the severity of injury,8–10 our data suggest that capnography might be useful to guide decision-making regarding termination of aggressive resuscitative efforts in the OR.

Resuscitation of severely injured patients requires extensive human and material resources. We could not estimate overall hospital costs attributed to resuscitation of patients with Etco2 <20 mm Hg who expired. In addition, we could not account for the opportunity cost of a trauma team working on these patients, wherein another patient could potentially could benefited from their care. Nonetheless, we were able to examine blood product utilization in nonsurvivors with low Etco2, which was substantial. Sustainable transfusion practices in trauma patients are essential to maintain adequate stocks of blood products. In the initial stages of massive transfusion protocol, prethawed or never-frozen universal donor AB plasma is frequently used to ensure early and adequate hemostatic resuscitation. AB FFP has a limited donor pool of <4% of the US population, thus imposing strain to maintain an adequate supply for massive transfusion protocols in many hospitals.14 Early and appropriately validated detection of nonsalvageable patients may reduce unnecessary use of resuscitative resources that are in limited supply.

Given our small sample size, it is premature to recommend clinical adoption of an Etco2 ≤20 mm Hg within 5 minutes of the onset of intraoperative mechanical ventilation for early termination of resuscitative efforts in trauma patients. A multicenter study confirming our findings would be required before this kind of recommendation could be made. Meanwhile, if such patients present to the OR with severe traumatic injuries accompanied by low Etco2, the potential for irreversible physiologic changes should be appreciated and current institutional practices followed.

There are several limitations to this study. First, it was performed at a single, freestanding urban academic trauma center with fellowship-trained trauma surgeons and a dedicated division of trauma anesthesiology. Advanced resuscitative techniques such as hemostatic resuscitation, massive transfusion protocols, resuscitative thoracotomy, damage control surgery, early central vascular access and monitoring, and viscoelastic coagulation testing are routinely used. Overall trauma mortality rate at our institution is approximately 7%, similar to other level 1 trauma centers accredited by American College of Surgeons.15,16 Thus, the severity of the injuries experienced by our patients is likely comparable to other, similar trauma hospitals. A second limitation is that our local emergency transport system has relatively short retrieval times (approximately 30 minutes), even comparing to advanced emergency medicine services servicing other trauma centers, where median transport times up to 1 hour have been reported.17 Thus, patients similar to the critically injured, moribund patients who arrive alive to our trauma resuscitation bay could die in transit elsewhere. This process of natural selection might result in higher overall survival in patients who survive the longer transport times. However, mortality might be increased in marginal patients who arrive alive but who had a prolonged course of hypovolemic shock, leading to irreversibility.17

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CONCLUSIONS

Etco2 level ≤20 mm Hg within 5 minutes of the onset of mechanical ventilation in the OR was associated with nonsurvival in trauma victims undergoing immediate surgery after resuscitation at a dedicated trauma hospital. Acceptance of this threshold for termination of resuscitation efforts should be deferred pending confirmation at other level 1 trauma centers in a sufficiently large sample to ensure statistical reliability.

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DISCLOSURES

Name: Roman Dudaryk, MD.

Contribution: This author helped design the study, conduct the study, analyze the data, and write the manuscript.

Name: Danielle K. Bodzin, MD.

Contribution: This author helped conduct the study, analyze the data, and write the manuscript.

Name: Juliet J. Ray, MD, MSPH.

Contribution: This author helped conduct the study, analyze the data, and write the manuscript.

Name: Craig S. Jabaley, MD.

Contribution: This author helped design the study, analyze the data, and write the manuscript.

Name: Richard R. McNeer, MD, PhD.

Contribution: This author helped design the study, conduct the study, analyze the data, perform the statistical analysis, and write the manuscript.

Name: Richard H. Epstein, MD.

Contribution: This author helped design the study, conduct the study, analyze the data, perform the statistical analysis, and write the manuscript.

This manuscript was handled by: Richard P. Dutton, MD.

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REFERENCES

1. Kauvar DS, Wade CE. The epidemiology and modern management of traumatic hemorrhage: US and international perspectives. Crit Care. 2005;9(suppl 5):S1–S9.
2. CDC. Key injury and violence data. Centers for Disease Control and Prevention. Available at: http://www.cdc.gov/injury/wisqars/overview/key_data.html. Accessed May 1, 2017.
3. Chapman MP, Moore EE, Moore HB. The “Death Diamond”: Rapid thrombelastography identifies lethal hyperfibrinolysis. J Trauma Acute Care Surg. 2015;79:925–929.
4. Peng J, Wheeler K, Shi J, Groner JI, Haley KJ, Xiang H. Trauma with injury severity score of 75: are these unsurvivable injuries? PLoS One. 2015;10:e0134821.
5. Cureton EL, Yeung LY, Kwan RO, et al. The heart of the matter: utility of ultrasound of cardiac activity during traumatic arrest. J Trauma Acute Care Surg. 2012;73:102–110.
6. Tisherman SA, Schmicker RH, Brasel KJ, et al. Detailed description of all deaths in both the shock and traumatic brain injury hypertonic saline trials of the Resuscitation Outcomes Consortium. Ann Surg. 2015;261:586–590.
7. Levine RL, Wayne MA, Miller CC. End-tidal carbon dioxide and outcome of out-of-hospital cardiac arrest. N Engl J Med. 1997;337:301–306.
8. Caputo ND, Fraser RM, Paliga A, et al. Nasal cannula end-tidal CO2 correlates with serum lactate levels and odds of operative intervention in penetrating trauma patients: a prospective cohort study. J Trauma Acute Care Surg. 2012;73:1202–1207.
9. Deakin CD, Sado DM, Coats TJ, Davies G. Prehospital end-tidal carbon dioxide concentration and outcome in major trauma. J Trauma. 2004;57:65–68.
10. Tyburski JG, Carlin AM, Harvey EH, Steffes C, Wilson RF. End-tidal CO2-arterial CO2 differences: a useful intraoperative mortality marker in trauma surgery. J Trauma. 2003;55:892–896.
11. Williams DJ, Guirgis FW, Morrissey TK, et al. End-tidal carbon dioxide and occult injury in trauma patients: ETCO2 does not rule out severe injury. Am J Emerg Med. 2016;34:2146–2149.
12. Stone ME, Kalata S, Liveris A, et al. End-tidal CO2 on admission is associated with hemorrhagic shock and predicts the need for massive transfusion as defined by the critical administration threshold: a pilot study. Injury. 2016;1383:30285–30286.
13. Cole E, Lecky F, West A, Smith N, Brohi K, Davenport R; ELoTS Study Collaborators. The impact of a pan-regional inclusive trauma system on quality of care. Ann Surg. 2016;264:188–194.
14. Dudaryk R, Hess AS, Varon AJ, Hess JR. What is new in the blood bank for trauma resuscitation. Curr Opin Anaesthesiol. 2015;28:206–209.
15. MacKenzie EJ, Rivara FP, Jurkovich GJ, et al. A national evaluation of the effect of trauma-center care on mortality. N Engl J Med. 2006;354:366–378.
16. Dutton RP, Stansbury LG, Leone S, Kramer E, Hess JR, Scalea TM. Trauma mortality in mature trauma systems: are we doing better? An analysis of trauma mortality patterns, 1997-2008. J Trauma. 2010;69:620–626.
17. Kidane B, Gupta V, El-Beheiry M. Association between prehospital time and mortality following blunt thoracic aortic injuries. Ann Vasc Surg. 2017;41:77–82.
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