A prospective, randomized trial of intravenous hydroxocobalamin versus whole blood transfusion compared to no treatment for Class III hemorrhagic shock resuscitation in a prehospital swine model

Comparison of hydroxocobalamin with other resuscitative fluids in volume-controlled and uncontrolled hemorrhage models in swine ( Sus-scrofa )

BACKGROUND

Traumatic hemorrhage is the leading cause of preventable death in military environments. Treatment with resuscitative fluids and blood components is based on availability, thus, frequently unavailable in the prehospital setting, due to lack of resources and costs. Hydroxocobalamin (HOC), increases blood pressure via nitric oxide scavenging. We evaluated HOC as a resuscitation fluid, in two swine hemorrhage models. Our objectives were to (1) evaluate whether HOC treatment following hemorrhagic shock improves hemodynamic parameters and (2) determine whether those effects are comparable to whole blood (WB) and lactated ringers (LR).

METHODS

Yorkshire swine (S us scrofa ) (n = 72) were used in models of controlled hemorrhage (CH) (n = 36) and uncontrolled hemorrhage (UH) (n = 36). Randomized animals received treatment with 500 mL of either WB, LR, HOC (150 mg/kg), followed by a six-hour observation (n = 6 each group). Survival, hemodynamics, blood gases (ABGs) and chemistries were collected. Data reported as mean ± standard error of the mean and statistical analysis by ANOVA ( p < 0.05).

RESULTS

Blood loss for CH was 41% ± 0.02 versus 33% ± 0.07 for UH. For CH, HOC treatment maintained higher systolic blood pressure (sBP, mm Hg) compared with WB and LR (72 ± 1.1; 60 ± 0.8; 58 ± 1.6; respectively). Heart rate (HR), cardiac output (CO), Sp o2 and vascular resistance were comparable with WB and LR. The ABG values were comparable between HOC and WB. For UH, HOC treatment maintained sBP levels comparable to WB and higher than LR (70 ± 0.9; 73 ± 0.5; 56 ± 1.2). HR, CO, Sp o2 , and systemic vascular resistance were comparable between HOC and WB. Survival, hemodynamics, blood gases were comparable between HOC and WB. No survival differences were found between cohorts.

CONCLUSION

Hydroxocobalamin treatment improved hemodynamic parameters and Ca 2+ levels compared with LR and equivalent to WB, in both models. Hydroxocobalamin may be a viable alternative when WB is not available.

Looking back to inform the future: a review of published paramedicine research

OBJECTIVE

Paramedicine has evolved in ways that may outpace the science informing these changes. Examining the scholarly pursuits of paramedicine may provide insights into the historical academic focus, which may inform future endeavors and evolution of paramedicine. The objective of this study was to explore the existing discourse in paramedicine research to reflect on the academic pursuits of this community.

METHODS

We searched Medline, Embase, CINAHL, Google Scholar and Web of Science from January, 2006 to April, 2019. We further refined the yield using a ranking formula that prioritized journals most relevant to paramedicine, then sampled randomly in two-year clusters for full text review. We extracted literature type, study topic and context, then used elements of qualitative content, thematic, and discourse analysis to further describe the sample.

RESULTS

The initial search yielded 99,124 citations, leaving 54,638 after removing duplicates and 7084 relevant articles from nine journals after ranking. Subsequently, 2058 articles were included for topic categorization, and 241 papers were included for full text analysis after random sampling. Overall, this literature reveals: 1) a relatively narrow topic focus, given the majority of research has concentrated on general operational activities and specific clinical conditions and interventions (e.g., resuscitation, airway management, etc.); 2) a limited methodological (and possibly philosophical) focus, given that most were observational studies (e.g., cohort, case control, and case series) or editorial/commentary; 3) a variety of observed trajectories of academic attention, indicating where the evolution of paramedicine is evident, areas where scope of practice is uncertain, and areas that aim to improve skills historically considered core to paramedic clinical practice.

CONCLUSIONS

Included articles suggest a relatively narrow topic focus, a limited methodological focus, and observed trajectories of academic attention indicating where research pursuits and priorities are shifting. We have highlighted that the academic focus may require an alignment with aspirational and direction setting documents aimed at developing paramedicine. This review may be a snapshot of scholarly activity that reflects a young medically directed profession and systems focusing on a few high acuity conditions, with aspirations of professional autonomy contributing to the health and social well-being of communities.

The Effect of Chest Compression Location and Aortic Perfusion in a Traumatic Arrest Model

BACKGROUND

Recent evidence demonstrates that closed chest compressions directly over the left ventricle (LV) in a traumatic cardiac arrest (TCA) model improve hemodynamics and return of spontaneous circulation (ROSC) when compared to traditional compressions. Selective aortic arch perfusion (SAAP) also improves hemodynamics and controls hemorrhage in TCA. We hypothesized that chest compressions located over the LV would result in improved hemodynamics and ROSC in a swine model of TCA using SAAP.

MATERIALS AND METHODS

Transthoracic echo was used to mark the location of the aortic root (Traditional location) and the center of the LV on animals (n = 24), which were randomized to receive chest compressions in one of the two locations. After hemorrhage, ventricular fibrillation (VF) was induced to simulate TCA. After a period of 10 min of VF, basic life support (BLS) with mechanical CPR was initiated and performed for 10 min, followed by advanced life support (ALS) for an additional 10 min. SAAP balloons were inflated at min 6 of BLS. Hemodynamic variables were averaged over the final 2 min of the BLS and ALS periods. Survival was compared between this SAAP cohort and a control group without SAAP (No-SAAP) (n = 26).

RESULTS

There was no significant difference in ROSC between the two SAAP groups (P = 0.67). There was no ROSC difference between SAAP and No-SAAP (P = 0.74).

CONCLUSIONS

There was no difference in ROSC between LV and Traditional compressions when SAAP was used in this swine model of TCA. SAAP did not confer a survival benefit compared to historical controls.

The Effect of Chest Compression Location and Occlusion of the Aorta in a Traumatic Arrest Model

BACKGROUND

Recent evidence demonstrates that closed chest compressions directly over the left ventricle (LV) in a traumatic cardiac arrest (TCA) model improve hemodynamics and return of spontaneous circulation (ROSC) when compared with traditional compressions. Resuscitative endovascular balloon occlusion of the aorta (REBOA) also improves hemodynamics and controls hemorrhage in TCA. We hypothesized that chest compressions located over the LV would result in improved hemodynamics and ROSC in a swine model of TCA using REBOA.

MATERIALS AND METHODS

Transthoracic echo was used to mark the location of the aortic root (traditional location) and the center of the LV on animals (n = 26), which were randomized to receive chest compressions in one of the two locations. After hemorrhage, ventricular fibrillation was induced to simulate TCA. After a period of 10 min of ventricular fibrillation, basic life support (BLS) with mechanical cardiopulmonary resuscitation was initiated and performed for 10 min followed by advanced life support for an additional 10 min. REBOA balloons were inflated at 6 min into BLS. Hemodynamic variables were averaged during the final 2 min of the BLS and advanced life support periods. Survival was compared between this REBOA cohort and a control group without REBOA (no-REBOA cohort) (n = 26).

RESULTS

There was no significant difference in ROSC between the two REBOA groups (P = 0.24). Survival was higher with REBOA group versus no-REBOA group (P = 0.02).

CONCLUSIONS

There was no difference in ROSC between LV and traditional compressions when REBOA was used in this swine model of TCA. REBOA conferred a survival benefit regardless of compression location.

Efficacy of Intravenous Hydroxocobalamin for Treatment of Sodium Methanethiolate Exposure in a Swine Model (Sus scrofa) of Severe Methanethiol Toxicity

INTRODUCTION

Methanethiol is a highly toxic chemical present in crude oil and natural gas. At high concentrations, methanethiol causes metabolic acidosis, seizures, myocardial infarction, coma, and death. Occupational Health and Safety Administration lists methanethiol as a potential terrorist weapon. Methanethiol blocks the electron transport chain, resulting in lactic acidosis and acidemia. There is no specific treatment for methanethiol. Our objective was to measure the efficacy of intravenous (IV) hydroxocobalamin (HOC) versus no treatment (control) in methanethiol-induced apnea in a swine model.

METHODS

Sixteen anesthetized swine received IV sodium methanethiolate to apnea and were randomized to receive either IV HOC or no treatment. Physiologic and laboratory parameters were monitored throughout the study. Power analysis indicated that 8 animals per group would be sufficient to find a moderate effect (f = 0.24) with 2 groups, α = 0.05, and 80% power.

RESULTS

Both groups were similar in baseline characteristics. Following treatment, the HOC group had significantly higher heart rate and blood pressure at 5-10 minutes post-apnea, higher systemic vascular resistance at 5 minutes post-apnea, higher tidal volume, higher end-tidal carbon dioxide, and lower end-tidal oxygen 10-15 minutes post-apnea compared with controls. None of the animals survived to the end of the study (60 minutes). The Kaplan-Meier survival curves were significantly different between cohorts (log-rank p = 0.0321), with the HOC group surviving longer than controls (32.4 ± 7.3 vs. 25.8 ± 1.0 minutes).

CONCLUSIONS

In our model of intravenous methanethiolate poisoning, IV HOC administration resulted in a transient improvement in vital signs and prolonged time to death; however, it did not improve survival.

Heparin Attenuates Visceral Apoptosis in a Swine Model of Hemorrhagic Shock and Reperfusion Injury

BACKGROUND

The use of unfractionated heparin in hypovolemic shock, aortic clamping, and visceral reperfusion is still not established, despite evidence of inhibition of early cell damage. This study investigated the potential protective effect of unfractionated heparin on hepatic and renal apoptosis in a porcine ischemia and reperfusion model.

METHODS

Twenty-one male swine (Sus scrofa) were divided into 3 groups: sham (n = 5), heparin (n = 8), and nonheparin (n = 8). The heparin and nonheparin groups underwent hypovolemic shock for 30 min, supraceliac aortic clamping for 1 h and reperfusion for 3 h. Unfractionated heparin 200 mg/kg was administered to the heparin group during aortic clamping. Hemodynamic and laboratory parameters were monitored, including aminotransferase and serum urea. Histological lesion scores were applied to hematoxylin and eosin-stained liver and kidney sections. Apoptosis quantification was performed by caspase-3 immunohistochemistry.

RESULTS

The proposed model caused a severe cardiocirculatory disturbance in the heparin and nonheparin groups, observed by the carotid-femoral pressure gradient and lactic acidosis. There was no significant difference in hemodynamic and laboratory parameters between these two groups. The mean values of liver and renal histological lesion scores did not present any significant differences. Caspase-3 immunoexpression was lower in the heparin than the nonheparin group for both liver and kidney.

CONCLUSIONS

Attenuation of liver and kidney cell apoptosis in pigs undergoing systemic heparinization suggests a potential use for heparin in modulating cell death under critical hemodynamic conditions.

Intravenous Hydroxocobalamin Versus Hextend Versus Control for Class III Hemorrhage Resuscitation in a Prehospital Swine Model

Background

Hydroxyethyl starch (Hextend) has been used for hemorrhagic shock resuscitation, however, hydroxyethyl starch may be associated with adverse outcomes.

Objective

To compare systolic blood pressure (sBP) in animals that had 30% of their blood volume removed and treated with intravenous hydroxocobalamin, hydroxyethyl starch, or no fluid.

Methods

Twenty-eight swine (45-55 kg) were anesthetized and instrumented with continuous femoral and pulmonary artery pressure monitoring. Animals were hemorrhaged 20 mL/kg over 20 minutes and then administered 150 mg/kg IV hydroxocobalamin in 180 mL saline, 500 mL hydroxyethyl starch, or no fluid and monitored for 60 minutes. Data were modeled using repeated measures multivariate analysis of variance.

Results

There were no significant differences before treatment. At 20 minutes after hemorrhage, there was no significant difference in mean sBP between treated groups, however, control animals displayed significantly lower mean sBP (p < 0.001). Mean arterial pressure and heart rate improved in the treated groups but not in the control group (p < 0.02). Prothrombin time was longer and platelet counts were lower in the Hextend group (p < 0.05). Moreover, thromboelastography analysis showed longer clotting (K) times (p < 0.05) for the hydroxyethyl starch-treated group.

Conclusion

Hydroxocobalamin restored blood pressure more effectively than no treatment and as effectively as hydroxyethyl starch but did not adversely affect coagulation.

Left ventricular compressions improve return of spontaneous circulation and hemodynamics in a swine model of traumatic cardiopulmonary arrest

BACKGROUND

Prehospital cardiopulmonary resuscitation, including closed chest compressions, has commonly been considered ineffective in traumatic cardiopulmonary arrest (TCPA) because traditional chest compressions do not produce substantial cardiac output. However, recent evidence suggests that chest compressions located over the left ventricle (LV) produce greater hemodynamics when compared to traditional compressions. We hypothesized that chest compressions located directly over the LV would improve return of spontaneous circulation (ROSC) and hemodynamics when compared with traditional chest compressions, in a swine model of TCPA.

METHODS

Transthoracic echocardiography was used to mark the location of the aortic root (traditional compressions), and the center of the LV on animals (n = 26) which were randomized to receive chest compressions in one of the two locations. After hemorrhage, ventricular fibrillation was induced. After 10 minutes of ventricular fibrillation, basic life support (BLS) with mechanical cardiopulmonary resuscitation was initiated and performed for 10 minutes followed by advanced life support (ALS) for an additional 10 minutes. During BLS, the area of maximal compression was verified using transesophageal echocardiography. Hemodynamic variables were averaged over the final 2 minutes of the BLS and ALS periods.

RESULTS

Five (38%) of the LV group achieved ROSC compared with zero of the aortic root group (p = 0.04). Additionally, there was an increase in aortic systolic blood pressure (SBP), aortic diastolic blood pressure (DBP) and coronary perfusion pressure (CPP) at the end of both the BLS (95% confidence interval, SBP, -49 to -21; DBP, -14 to -5.6; and CPP, -15 to -7.4) and ALS (95% confidence interval: SBP, -66 to -21; DBP, -49 to -6.8; and CPP, -51 to -7.5) resuscitation periods among the LV group.

CONCLUSION

In our swine model of TCPA, chest compressions performed directly over the LV improved ROSC and hemodynamics when compared with traditional chest compressions.