“Permissive hypoventilation” in a swine model of hemorrhagic shock

Stop the Bleed-Wait for the Ambulance or Get in the Car and Drive? A Post Hoc Analysis of an EAST Multicenter Trial

Background: The Stop the Bleed campaign gives bystanders an active role in prehospital hemorrhage control. Whether extending bystanders' role to private vehicle transport (PVT) for urban penetrating trauma improves survival is unknown, but past research has found benefit to police and PVT. We hypothesized that for penetrating trauma in an urban environment, where prehospital procedures have been proven harmful, PVT improves outcomes compared to any EMS or advanced life support (ALS) transport.Methods: Post-hoc analysis of an EAST multicenter trial was performed on adult patients with penetrating torso/proximal extremity trauma at 25 urban trauma centers from 5/2019-5/2020. Patients were allocated to PVT and any EMS or ALS transport using nearest neighbor propensity score matching. Univariate analyses included Wilcoxon signed rank or McNemar's Test and logistic regression.Results: Of 1999 penetrating trauma patients in urban settings, 397 (19.9%) had PVT, 1433 (71.7%) ALS transport, and 169 (8.5%) basic life support (BLS) transport. Propensity matching yielded 778 patients, distributed equally into balanced groups. PVT patients were primarily male (90.5%), Black (71.2%), and sustained gunshot wounds (68.9%). ALS transport had significantly higher ED mortality (3.9% vs 1.9%, P = 0.03). There was no difference in in-hospital mortality rate, hospital LOS, or complications for all EMS or ALS only transport patients.Conclusion: Compared to PVT, ALS, which provides more prehospital procedures than BLS, provided no survival benefit for penetrating trauma patients in urban settings. Bystander education incorporating PVT for early arrival of penetrating trauma patients in urban settings to definitive care merits further investigation.

Prioritizing Circulation to Improve Outcomes for Patients with Exsanguinating Injury: A Literature Review and Techniques to Help Clinicians Achieve Bleeding Control

Prioritizing circulation in trauma care and delaying intubation in noncompressible cases improve outcomes. By prioritizing circulation, patient survival significantly improves, advocating evidence-based shifts in trauma care.

The Impact of Out-of-Hospital Time and Prehospital Intubation on Return of Spontaneous Circulation following Resuscitative Thoracotomy in Traumatic Cardiac Arrest

INTRODUCTION

Resuscitative thoracotomy (RT) is a critical procedure performed in certain trauma patients in extremis, with extremely low survival rates. Currently, there is a paucity of data pertaining to prehospital variables and their predictive role in survival outcomes in traumatic cardiac arrest (TCA) patients requiring RT. The aim of the study was to determine the impact of prehospital intubation and out-of-hospital time (OOHT) on return of spontaneous circulation (ROSC) and survival in TCA requiring RT.

METHODS

This was a retrospective cohort study of trauma patients presenting to two level-1 trauma centers, St. Michael's Hospital and Sunnybrook Health Sciences Center, in Toronto, Canada (January 1, 2005-December 31, 2020). Our exposures of interest were any prehospital intubation attempt and OOHT. Primary and secondary outcome measures were ROSC post-RT and survival to hospital discharge, respectively, and data analysis was performed using univariate logistic regression.

RESULTS

A total of 195 patients were included, of which 86% were male, and the mean age was 33 years. ROSC and survival to hospital discharge were achieved in 30% and 5% of patients, respectively. Of those who survived to discharge, 89% sustained penetrating trauma. There was no association between OOHT and ROSC (OR = 1.00, 95% CI 0.97-1.03) or survival (OR = 0.99, 95% CI 0.94-1.05). The odds of ROSC were lower in penetrating trauma in the presence of any prehospital intubation attempt (OR = 0.39, 95% CI 0.19-0.82, p = 0.01). ROSC was less likely among all patients with no prehospital signs of life (SOL) compared to those who had prehospital SOL (OR = 0.30, 95% CI 0.13-0.69, p < 0.01).

CONCLUSIONS

There was a significant association between prehospital intubation and lower likelihoods of ROSC in the penetrating TCA population requiring RT, as well as with the absence of prehospital SOL in all patients. OOHT did not appear to significantly impact ROSC or survival.

Permissive hypoventilation equally effective to maintain oxygenation as positive pressure ventilation after porcine class III hemorrhage and whole blood resuscitation

BACKGROUND

Prehospital anesthesia may lead to circulatory collapse after severe hemorrhage. It is possible that permissive hypoventilation, refraining from tracheal intubation and accepting spontaneous ventilation, decreases this risk, but it is not known if oxygen delivery can be maintained. We investigated the feasibility of permissive hypoventilation after class III hemorrhage and whole blood resuscitation in three prehospital phases: 15 min on-scene, 30 min whole blood resuscitation, and 45 min after.

STUDY DESIGN AND METHODS

19 crossbred swine, mean weight 58.5 kg, were anesthetized with ketamine/midazolam and hemorrhaged to a mean (SD) 1298 (220) mL (33%) and randomized to permissive hypoventilation (n = 9) or positive pressure ventilation with FiO2 21% (n = 10).

RESULTS

In permissive hypoventilation versus positive pressure ventilation, indexed oxygen delivery (DO2 I) decreased to mean (SD) 4.73 (1.06) versus 3.70 (1.13) mL min-1  kg-1 after hemorrhage and increased to 8.62 (2.09) versus 6.70 (1.56) mL min-1  kg-1 at completion of resuscitation. DO2 I, indexed oxygen consumption (VO2 I), and arterial saturation (SaO2 ) did not differ. Permissive hypoventilation increased the respiratory rate and increased pCO2 . Positive pressure ventilation did not deteriorate circulation. Cardiac index (CI), systolic arterial pressure (SAP), hemoglobin (Hb), and heart rate did not differ.

DISCUSSION

Permissive hypoventilation and positive pressure ventilation were equally effective to maintain oxygen delivery in all phases. A respiratory rate of 40 was feasible, showing no signs of respiratory fatigue for 90 min, indicating that whole blood resuscitation may be prioritized in select patients with severe hemorrhage and spontaneous breathing.

An analysis of police transport in an Eastern Association for the Surgery of Trauma multicenter trial examining prehospital procedures in penetrating trauma patients

BACKGROUND

Police transport (PT) of penetrating trauma patients in urban locations has become routine in certain metropolitan areas; however, whether it results in improved outcomes over prehospital Advanced life support (ALS) transport has not been determined in a multicenter study. We hypothesized that PT would not result in improved outcomes.

METHODS

This was a multicenter, prospective, observational study of adults (18+ years) with penetrating trauma to the torso and/or proximal extremity presenting at 25 urban trauma centers. Police transport and ALS patients were allocated via nearest neighbor, propensity matching. Transport mode also examined by Cox regression.

RESULTS

Of 1,618 total patients, 294 (18.2%) had PT and 1,324 (81.8%) were by ALS. After matching, 588 (294/cohort) remained. The patients were primarily Black (n = 497, 84.5%), males (n = 525, 89.3%, injured by gunshot wound (n = 494, 84.0%) with 34.5% (n = 203) having Injury Severity Score of 16 or higher. Overall mortality by propensity matching was not different between cohorts (15.6% ALS vs. 15.0% PT, p = 0.82). In severely injured patients (Injury Severity Score ≥16), mortality did not differ between PT and ALS transport (38.8% vs. 36.0%, respectively; p = 0.68). Cox regression analysis controlled for relevant factors revealed no association with a mortality benefit in patients transported by ALS.

CONCLUSION

Police transport of penetrating trauma patients in urban locations results in similar outcomes compared with ALS. Immediate transport to definitive trauma care should be emphasized in this patient population.

LEVEL OF EVIDENCE

Prognostic and Epidemiologic; Level III.

Dimethyl malonate slows succinate accumulation and preserves cardiac function in a swine model of hemorrhagic shock

BACKGROUND

Succinate (SI) is a citric acid cycle metabolite that accumulates in tissues during hemorrhagic shock (HS) due to electron transport chain uncoupling. Dimethyl malonate (DMM) is a competitive inhibitor of SI dehydrogenase, which has been shown to reduce SI accumulation and protect against reperfusion injury. Whether DMM can be therapeutic after severe HS is unknown. We hypothesized that DMM would prevent SI buildup during resuscitation (RES) in a swine model of HS, leading to better physiological recovery after RES.

METHODS

The carotid arteries of Yorkshire pigs were cannulated with a 5-Fr catheter. After placement of a Swan-Ganz catheter and femoral arterial line, the carotid catheters were opened and the animals were exsanguinated to a mean arterial pressure (MAP) of 45 mm. After 30 minutes in the shock state, the animals were resuscitated to a MAP of 60 mm using lactated ringers. A MAP above 60 mm was maintained throughout RES. One group received 10 mg/kg of DMM (n = 6), while the control received sham injections (n = 6). The primary end-point was SI levels. Secondary end-points included cardiac function and lactate.

RESULTS

Succinate levels increased from baseline to the 20-minute RES point in control, while the DMM cohort remained unchanged. The DMM group required less intravenous fluid to maintain a MAP above 60 (450.0 vs. 229.0 mL; p = 0.01). The DMM group had higher pulmonary capillary wedge pressure at the 20-minute and 40-minute RES points. The DMM group had better recovery of cardiac output and index during RES, while the control had no improvement. While lactate levels were similar, DMM may lead to increased ionized calcium levels.

DISCUSSION

Dimethyl malonate slows SI accumulation during HS and helps preserve cardiac filling pressures and function during RES. In addition, DMM may protect against depletion of ionized calcium. Dimethyl malonate may have therapeutic potential during HS.

Talk and Die: A Descriptive Analysis of Penetrating Trauma Patients

INTRODUCTION

"Talk and die" traditionally described occult presentations of fatal intracranial injuries, but we broaden its definition to victims of penetrating trauma.

METHODS

We conducted a descriptive analysis of patients with penetrating torso trauma who presented with a Glasgow Coma Scale verbal score ≥3 and died within 48 h of arrival from 2008 to 2018.

RESULTS

Sixty patients were identified. Eighteen (30.0%) required resuscitative thoracotomy with 7 (11.7%) dying in the trauma bay. Fifty-three (86.9%) patients went to the operating room, and 35 (66.0%) required multicavitary exploration. The most common injuries were hollow viscous (58.5%), intra-abdominal vascular (49.0%), liver (28.3%), pulmonary (26.4%), intrathoracic vascular (18.9%), and cardiac (15.75) injuries. Twenty-three (43.4%) patients survived their initial operation, but died in the first 48 h postoperatively.

CONCLUSIONS

Patients who "talk and die" most frequently have intra-abdominal vascular injures and require multicavitary exploration.

An Eastern Association for the Surgery of Trauma multicenter trial examining prehospital procedures in penetrating trauma patients

BACKGROUND

Prehospital procedures (PHP) by emergency medical services (EMS) are performed regularly in penetrating trauma patients despite previous studies demonstrating no benefit. We sought to examine the influence of PHPs on outcomes in penetrating trauma patients in urban locations where transport to trauma center is not prolonged. We hypothesized that patients without PHPs would have better outcomes than those undergoing PHP.

METHODS

This was an Eastern Association for the Surgery of Trauma-sponsored, multicenter, prospective, observational trial of adults (18+ years) with penetrating trauma to the torso and/or proximal extremity presenting at 25 urban trauma centers. The impact of PHPs and transport mechanism on in-hospital mortality were examined.

RESULTS

Of 2,284 patients included, 1,386 (60.7%) underwent PHP. The patients were primarily Black (n = 1,527, 66.9%) males (n = 1,986, 87.5%) injured by gunshot wound (n = 1,510, 66.0%) with 34.1% (n = 726) having New Injury Severity Score of ≥16. A total of 1,427 patients (62.5%) were transported by Advanced Life Support EMS, 17.2% (n = 392) by private vehicle, 13.7% (n = 312) by police, and 6.7% (n = 153) by Basic Life Support EMS. Of the PHP patients, 69.1% received PHP on scene, 59.9% received PHP in route, and 29.0% received PHP both on scene and in route. Initial scene vitals differed between groups, but initial emergency department vitals did not. Receipt of ≥1 PHP increased mortality odds (odds ratio [OR], 1.36; 95% confidence interval [CI], 1.01-1.83; p = 0.04). Logistic regression showed increased mortality with each PHP, whether on scene or during transport. Subset analysis of specific PHP revealed that intubation (OR, 10.76; 95% CI, 4.02-28.78; p < 0.001), C-spine immobilization (OR, 5.80; 95% CI, 1.85-18.26; p < 0.01), and pleural decompression (OR, 3.70; 95% CI, 1.33-10.28; p = 0.01) had the highest odds of mortality after adjusting for multiple variables.

CONCLUSION

Prehospital procedures in penetrating trauma patients impart no survival advantage and may be harmful in urban settings, even when performed during transport. Therefore, PHP should be forgone in lieu of immediate transport to improve patient outcomes.

LEVEL OF EVIDENCE

Prognostic, level III.

Acute overventilation does not cause lung damage in moderately hemorrhaged swine

Airway management is important in trauma and critically ill patients. Prolonged mechanical ventilation results in overventilation-induced lung barotrauma, but few studies have examined the consequence of acute (1 h or less) overventilation. We hypothesized that acute hyperventilation, as might inadvertently be performed in prehospital settings, would elevate systemic inflammation and cause lung damage. Female Yorkshire pigs (40-50 kg, n = 10/group) were anesthetized, instrumented for hemodynamic measurements and blood sampling, and underwent a 25% controlled hemorrhage followed by 1 h of 1) spontaneous breathing, 2) "normal" bag ventilation (4.8 L·min volume, ∼400 mL tidal volume, 12 breaths/minute), 3) bag hyperventilation (9 L·min volume, ∼750 mL tidal volume, 12 breaths/minute), 4) maximum hyperventilation (15 L·min volume, ∼750 mL tidal volume, 20 breaths/minute), or 5) mechanical ventilation. Pigs then regained consciousness and recovered for 24 h, followed by euthanasia and collection of blood and tissue samples. No level of manual ventilation had any significant impact on hemodynamic variables. Blood markers of tissue damage and plasma cytokines were not statistically different between groups with the exception of a transient increase in IL-1β; all values returned to baseline by 24 h. On pathological review, severity and distribution of lung edema or other gross pathologies were not significantly different between groups. These data indicate hyperventilation causes no adverse effects, to include inflammation and tissue damage, and that acute overventilation, as could be seen in the prehospital phase of trauma care, does not produce evidence of adverse effects on the lungs following moderate hemorrhage.NEW & NOTEWORTHY Appropriate airway management is essential in trauma and critically ill patients. Prolonged mechanical ventilation can result in overventilation-induced lung barotrauma, but few studies have examined the consequence of acute overventilation. We investigated the outcome of hemorrhage followed by 1 h of overventilation in swine. We found that acute overventilation, as could be seen in the prehospital phase of trauma care, does not produce evidence of adverse effects on otherwise healthy lungs following moderate hemorrhage.

Cardiovascular Effects of Shock and Trauma in Experimental Models. A Review

Experimental models of human pathology are useful guides to new approaches towards improving clinical and surgical treatments. A systematic search through PubMed using the syntax (shock) AND (trauma) AND (animal model) AND (cardiovascular) AND ("2010/01/01"[PDat]: "2015/12/31"[PDat]) found 88 articles, which were reduced by manual inspection to 43 entries. These were divided into themes and each theme is subsequently narrated and discussed conjointly. Taken together, these articles indicate that valuable information has been developed over the past 5 years concerning endothelial stability, mesenteric lymph, vascular reactivity, traumatic injuries, burn and sepsis. A surviving interest in hypertonic saline resuscitation still exists.

Field intubation in civilian patients with hemorrhagic shock is associated with higher mortality

BACKGROUND

Field intubation (FI) by emergency medical service personnel on severely injured trauma patients remains a contentious practice. Clinical studies suggest an association between FI and adverse outcomes in patients with traumatic brain injury. Military tactical emergency casualty care recommends deferring intubation and providing supplemental oxygenation until reaching a more equipped destination. In addition, animal models with penetrating hemorrhagic shock demonstrate increased acidosis with intubation before resuscitation. The purpose of this study was to evaluate the impact of FI on outcomes in trauma patients with hemorrhagic shock requiring massive transfusion.

METHODS

The Los Angeles County Trauma System Database was retrospectively queried for all trauma patients 16 years or older with hemorrhagic shock requiring massive transfusion (≥6 U packed red blood cells in the first 24 hours) between January 1, 2012, and June 30, 2014. Demographics, clinical and transfusion data, and outcomes were compared between patients who received FI and those who did not (NO-FI). Multivariate regression analysis was used to adjust for confounders.

RESULTS

Of 552 trauma patients meeting inclusion criteria, 63 (11%) received FI, and the remaining 489 (89%) were NO-FI. Age, sex, and incidence of blunt injury were similar between the FI and the NO-FI group. The FI cohort presented with a lower median Glasgow Coma Scale (GCS) score (3 vs. 14, p < 0.001), a lower median systolic blood pressure (86 mm Hg vs. 104 mm Hg, p < 0.001), and a higher median Injury Severity Score (ISS) (41 vs. 29, p < 0.001). Mortality was significantly higher in FI patients (83% vs. 43%, p < 0.001). Transfusion patterns and total field times were similar in both groups. After adjusting for confounders, FI patients had increased odds of mortality (adjusted odds ratio, 2.89; 95% confidence interval, 1.08-7.78; p = 0.035). In addition, FI was identified as an independent predictor of mortality (adjusted odds ratio, 3.41; 95% confidence interval, 1.35-8.59; p = 0.009).

CONCLUSION

FI may be associated with higher mortality in trauma patients with hemorrhagic shock requiring massive transfusion. Less invasive airway interventions and rapid transport might improve outcomes for these patients.

LEVEL OF EVIDENCE

Therapeutic study, level IV; epidemiologic study, level III.

Challenging the dogma of traumatic cardiac arrest management: a military perspective

Attempts to resuscitate patients in traumatic cardiac arrest (TCA) have, in the past, been viewed as futile. However, reported outcomes from TCA in the past five years, particularly from military series, are improving. The pathophysiology of TCA is different to medical causes of cardiac arrest, and therefore, treatment priorities may also need to be different. This article reviews recent literature describing the pathophysiology of TCA and describes how the military has challenged the assumption that outcome is universally poor in these patients.

Predictors of mortality and prehospital monitoring limitations in blunt trauma patients

This study aimed at determining predictors of in-hospital mortality and prehospital monitoring limitations in severely injured intubated blunt trauma patients. We retrospectively reviewed patients' charts. Prehospital vital signs, Injury Severity Score (ISS), initial Glasgow Coma Scale (GCS), Revised Trauma Score (RTS), arterial blood gases, and lactate were compared in two study groups: survivors (n = 40) and nonsurvivors (n = 30). There were no significant differences in prehospital vital signs between compared groups. Nonsurvivors were older (P = 0.006), with lower initial GCS (P < 0.001) and higher ISS (P < 0.001), along with higher lactate (P < 0.001) and larger base deficit (BD; P = 0.006), whereas RTS (P = 0.001) was lower in nonsurvivors. For predicting mortality, area under the curve (AUC) was calculated: for lactate 0.82 (P < 0.001), for ISS 0.82 (P < 0.001), and for BD 0.69 (P = 0.006). Lactate level of 3.4 mmol/L or more was 82% sensitive and 75% specific for predicting in-hospital death. In a multivariate logistic regression model, ISS (P = 0.037), GCS (P = 0.033), and age (P = 0.002) were found to be independent predictors of in-hospital mortality. The AUC for regression model was 0.93 (P < 0.001). Increased levels of lactate and BD on admission indicate more severe occult hypoperfusion in nonsurvivors whereas vital signs did not differ between the groups.