Survival with full neurologic recovery after prolonged cardiopulmonary resuscitation with a combination of vasopressin and epinephrine in pigs

Can a Therapeutic Strategy for Hypotension Improve Cerebral Perfusion and Oxygenation in an Experimental Model of Hemorrhagic Shock and Severe Traumatic Brain Injury?

BACKGROUND

Restoration of brain tissue perfusion is a determining factor in the neurological evolution of patients with traumatic brain injury (TBI) and hemorrhagic shock (HS). In a porcine model of HS without neurological damage, it was observed that the use of fluids or vasoactive drugs was effective in restoring brain perfusion; however, only terlipressin promoted restoration of cerebral oxygenation and lower expression of edema and apoptosis markers. It is unclear whether the use of vasopressor drugs is effective and beneficial during situations of TBI. The objective of this study is to compare the effects of resuscitation with saline solution and terlipressin on cerebral perfusion and oxygenation in a model of TBI and HS.

METHODS

Thirty-two pigs weighing 20-30 kg were randomly allocated into four groups: control (no treatment), saline (60 ml/kg of 0.9% NaCl), terlipressin (2 mg of terlipressin), and saline plus terlipressin (20 ml/kg of 0.9% NaCl + 2 mg of terlipressin). Brain injury was induced by lateral fluid percussion, and HS was induced through pressure-controlled bleeding, aiming at a mean arterial pressure (MAP) of 40 mmHg. After 30 min of circulatory shock, resuscitation strategies were initiated according to the group. The systemic and cerebral hemodynamic and oxygenation parameters, lactate levels, and hemoglobin levels were evaluated. The data were subjected to analysis of variance for repeated measures. The significance level established for statistical analysis was p < 0.05.

RESULTS

The terlipressin and saline plus terlipressin groups showed an increase in MAP that lasted until the end of the experiment (p < 0.05). There was a notable increase in intracranial pressure in all groups after starting treatment for shock. Cerebral perfusion pressure and cerebral oximetry showed no improvement after hemodynamic recovery in any group. The groups that received saline at resuscitation had the lowest hemoglobin concentrations after treatment.

CONCLUSIONS

The treatment of hypotension in HS with saline and/or terlipressin cannot restore cerebral perfusion or oxygenation in experimental models of HS and severe TBI. Elevated MAP raises intracranial pressure owing to brain autoregulation dysfunction caused by TBI.

Reassessment Campaign on Veterinary Resuscitation (RECOVER) Initiative small animal CPR registry report 2016-2021

OBJECTIVE

To introduce the Reassessment Campaign on Veterinary Resuscitation (RECOVER) CPR registry and report cardiopulmonary arrest (CPA) and CPR event data collected to date.

DESIGN

International, multi-institutional veterinary CPR registry data report.

SETTING

Veterinary private practice and university teaching hospitals.

ANIMALS

Data from 514 dogs and 195 cats undergoing CPR entered in the RECOVER CPR registry between February 2016 and November 2021.

INTERVENTIONS

The RECOVER CPR registry is an online medical database created for standardized collection of hospital, animal, arrest, and outcome information on dogs and cats undergoing CPR. Data were collected according to the veterinary Utstein-style guidelines for standardized reporting of in-hospital CPR in dogs and cats. Case records were downloaded, duplicate and incomplete cases were removed, and summary descriptive data were reported.

MEASUREMENTS AND MAIN RESULTS

Sixteen hospitals in the United States, Europe, and Australia contributed data on 709 CPR events to the registry. One hundred and forty-two (28%) dogs and 58 (30%) cats attained return of spontaneous circulation (ROSC), 62 (12%) dogs and 25 (13%) cats had ROSC >20 minutes, and 14 (3%) dogs and 4 (2%) cats survived to hospital discharge. The reason for CPR discontinuation was reported as owner choice in 321 cases (63%). The most common suspected causes for CPA were respiratory failure (n = 142, 20%), heart failure (n = 86, 12%), and hemorrhage (n = 76, 11%).

CONCLUSION

The RECOVER CPR registry contains the first multicenter data set on small animal CPR. It confirms poor outcomes associated with CPA, emphasizing the need for large-sized studies to gain adequate information on characteristics associated with favorable outcomes.

Terlipressin combined with conservative fluid management attenuates hemorrhagic shock-induced acute kidney injury in rats

Hemorrhagic shock (HS), a major cause of trauma-related mortality, is mainly treated by crystalloid fluid administration, typically with lactated Ringer's (LR). Despite beneficial hemodynamic effects, such as the restoration of mean arterial pressure (MAP), LR administration has major side effects, including organ damage due to edema. One strategy to avoid such effects is pre-hospitalization intravenous administration of the potent vasoconstrictor terlipressin, which can restore hemodynamic stability/homeostasis and has anti-inflammatory effects. Wistar rats were subjected to HS for 60 min, at a target MAP of 30-40 mmHg, thereafter being allocated to receive LR infusion at 3 times the volume of the blood withdrawn (liberal fluid management); at 2 times the volume (conservative fluid management), plus terlipressin (10 µg/100 g body weight); and at an equal volume (conservative fluid management), plus terlipressin (10 µg/100 g body weight). A control group comprised rats not subjected to HS and receiving no fluid resuscitation or treatment. At 15 min after fluid resuscitation/treatment, the blood previously withdrawn was reinfused. At 24 h after HS, MAP was higher among the terlipressin-treated animals. Terlipressin also improved post-HS survival and provided significant improvements in glomerular/tubular function (creatinine clearance), neutrophil gelatinase-associated lipocalin expression, fractional excretion of sodium, aquaporin 2 expression, tubular injury, macrophage infiltration, interleukin 6 levels, interleukin 18 levels, and nuclear factor kappa B expression. In terlipressin-treated animals, there was also significantly higher angiotensin II type 1 receptor expression and normalization of arginine vasopressin 1a receptor expression. Terlipressin associated with conservative fluid management could be a viable therapy for HS-induced acute kidney injury, likely attenuating such injury by modulating the inflammatory response via the arginine vasopressin 1a receptor.

The Heart as a Target of Vasopressin and Other Cardiovascular Peptides in Health and Cardiovascular Diseases

The automatism of cardiac pacemaker cells, which is tuned, is regulated by the autonomic nervous system (ANS) and multiple endocrine and paracrine factors, including cardiovascular peptides. The cardiovascular peptides (CPs) form a group of essential paracrine factors affecting the function of the heart and vessels. They may also be produced in other organs and penetrate to the heart via systemic circulation. The present review draws attention to the role of vasopressin (AVP) and some other cardiovascular peptides (angiotensins, oxytocin, cytokines) in the regulation of the cardiovascular system in health and cardiovascular diseases, especially in post-infarct heart failure, hypertension and cerebrovascular strokes. Vasopressin is synthesized mostly by the neuroendocrine cells of the hypothalamus. There is also evidence that it may be produced in the heart and lungs. The secretion of AVP and other CPs is markedly influenced by changes in blood volume and pressure, as well as by other disturbances, frequently occurring in cardiovascular diseases (hypoxia, pain, stress, inflammation). Myocardial infarction, hypertension and cardiovascular shock are associated with an increased secretion of AVP and altered responsiveness of the cardiovascular system to its action. The majority of experimental studies show that the administration of vasopressin during ventricular fibrillation and cardiac arrest improves resuscitation, however, the clinical studies do not present consisting results. Vasopressin cooperates with the autonomic nervous system (ANS), angiotensins, oxytocin and cytokines in the regulation of the cardiovascular system and its interaction with these regulators is altered during heart failure and hypertension. It is likely that the differences in interactions of AVP with ANS and other CPs have a significant impact on the responsiveness of the cardiovascular system to vasopressin in specific cardiovascular disorders.

Translation from animal studies of novel pharmacological therapies to clinical trials in cardiac arrest: A systematic review

BACKGROUND

There is a lack of new promising therapies to improve the dismal outcomes from cardiac arrest. The objectives of this study were: (1) To identify novel pharmacological therapies investigated in experimental animal studies and (2) to identify pharmacological therapies translated from experimental animal studies to clinical trials.

METHODS

PubMed was searched to first identify relevant experimental cardiac arrest animal models published within the last 20 years. Based on this, a list of interventions was created and a second search was performed to identify clinical trials testing one of these interventions. Data extraction was performed using standardised data extraction forms.

RESULTS

We identified 415 animal studies testing 190 different pharmacological interventions. The most commonly tested interventions were classified as vasopressors, anaesthetics/gases, or interventions aimed at molecular targets. We found 43 clinical trials testing 26 different interventions identified in the animal studies. Of these, 13 trials reported positive findings and 30 trials reported neutral findings with regards to the primary endpoint. No study showed harm of the intervention. Some interventions tested in human clinical trials, had previously been tested in animal studies without a positive effect on outcomes. A large number of animal studies was performed after publication of a clinical trial.

CONCLUSION

Numerous different pharmacological interventions have been tested in experimental animal models. Despite this only a limited number of these interventions have advanced to clinical trials, however several of the clinical trials tested interventions that were first tested in experimental animal models.

Use of a Porcine Model to Evaluate the Risks and Benefits of Vasopressors in Propranolol Poisoning

INTRODUCTION

Vasopressors are a commonly used treatment in beta-blocker poisoning despite evidence they may be ineffective or harmful. The primary objective of the present study is to use previously collected data from two prior studies (high-dose insulin (HDI) versus vasopressin + epinephrine and a placebo-controlled HDI study) to compare survival between vasopressin + epinephrine and placebo. Secondary outcomes included a comparison with HDI as well as comparisons with hemodynamic parameters, including mean arterial pressure (MAP), cardiac output (CO), heart rate (HR), and systemic vascular resistance (SVR).

METHODS

Cardiogenic shock was induced in healthy pigs with a bolus of 0.5 mg/kg of intravenous propranolol followed by an infusion of 0.25 mg/kg/minute until the point of toxicity, defined as (0.75 × initial HR × initial MAP), at which point the infusion was reduced to 0.125 mg/kg/minute for 240 (vasopressin + epinephrine or HDI) or 360 minutes (placebo) or until death.

RESULTS

Survival was significantly lower in pigs receiving vasopressin + epinephrine (0%, 0/5) than in pigs receiving placebo (50%, 2/4) (p < 0.01). Survival was significantly higher with HDI compared with both groups (100%, 5/5) (p < 0.01). All vasopressin + epinephrine pigs died within 100 minutes after reaching toxicity. Over the course of the resuscitation, we observed a statistically significant steady decrease in CO and HR in the vasopressin + epinephrine group compared with placebo (p < 0.01). In contrast, we observed a statistically significant change in MAP and SVR that followed a parabolic arc, with MAP and SVR rising significantly initially in the vasopressin + epinephrine group then rapidly falling until death (p < 0.01).

CONCLUSIONS

Mortality was higher with vasopressors compared with placebo in this porcine model of propranolol poisoning. Further studies are warranted to define the optimal timing and role of vasopressors in beta-blocker poisoning.

Role of vasopressin in current anesthetic practice

Arginine vasopressin (AVP), also known as antidiuretic hormone, is a peptide endogenously secreted by the posterior pituitary in response to hyperosmolar plasma or systemic hypoperfusion states. When administered intravenously, it causes an intense peripheral vasoconstriction through stimulation of V₁ receptors on the vascular smooth muscle. Patients in refractory shock associated with severe sepsis, cardiogenic or vasodilatory shock, or cardiopulmonary bypass have inappropriately low plasma levels of AVP (‘relative vasopressin deficiency’) and supersensitivity to exogenously-administered AVP. Low doses of AVP and its synthetic analog terlipressin can restore vasomotor tone in conditions that are resistant to catecholamines, with preservation of renal blood flow and urine output. They are also useful in the treatment of refractory arterial hypotension in patients chronically treated with renin-angiotensin system inhibitors, cardiac arrest, or bleeding esophageal varices. In the perioperative setting, they represent attractive adjunct vasopressors in advanced shock states that are unresponsive to conventional therapeutic strategies.

Effects of terlipressin as early treatment for protection of brain in a model of haemorrhagic shock

Introduction

We investigated whether treatment with terlipressin during recovery from hypotension due to haemorrhagic shock (HS) is effective in restoring cerebral perfusion pressure (CPP) and brain tissue markers of water balance, oxidative stress and apoptosis.

Methods

In this randomised controlled study, animals undergoing HS (target mean arterial pressure (MAP) 40 mmHg for 30 minutes) were randomised to receive lactated Ringer’s solution (LR group; n =14; volume equal to three times the volume bled), terlipressin (TERLI group; n =14; 2-mg bolus), no treatment (HAEMO group; n =12) or sham (n =6). CPP, systemic haemodynamics (thermodilution technique) and blood gas analyses were registered at baseline, shock and 5, 30, 60 (T60), 90 and 120 minutes after treatment (T120). After the animals were killed, brain tissue samples were obtained to measure markers of water balance (aquaporin-4 (AQP4)), Na⁺-K⁺-2Cl⁻ co-transporter (NKCC1)), oxidative stress (thiobarbituric acid reactive substances (TBARS) and manganese superoxide dismutase (MnSOD)) and apoptotic damage (Bcl-x and Bax).

Results

Despite the HS-induced decrease in cardiac output (CO) and hyperlactataemia, resuscitation with terlipressin recovered MAP and resulted in restoration of CPP and in cerebral protection expressed by normalisation of AQP4, NKCC1, TBARS and MnSOD expression and Bcl-x/Bax ratio at T60 and T120 compared with sham animals. In the LR group, CO and blood lactate levels were recovered, but the CPP and MAP were significantly decreased and TBARS levels and AQP4, NKCC1 and MnSOD expression and Bcl-x/Bax ratio were significantly increased at T60 and T120 compared with the sham group.

Conclusions

During recovery from HS-induced hypotension, terlipressin was effective in normalising CPP and cerebral markers of water balance, oxidative damage and apoptosis. The role of this pressor agent on brain perfusion in HS requires further investigation.

Vasopressin in hemorrhagic shock: a systematic review and meta-analysis of randomized animal trials

Objective. The latest European guidelines for the management of hemorrhagic shock suggest the use of vasopressors (norepinephrine) in order to restore an adequate mean arterial pressure when fluid resuscitation therapy fails to restore blood pressure. The administration of arginine vasopressin (AVP), or its analogue terlipressin, has been proposed as an alternative treatment in the early stages of hypovolemic shock. Design. A meta-analysis of randomized controlled animal trials. Participants. A total of 433 animals from 15 studies were included. Interventions. The ability of AVP and terlipressin to reduce mortality when compared with fluid resuscitation therapy, other vasopressors (norepinephrine or epinephrine), or placebo was investigated. Measurements and Main Results. Pooled estimates showed that AVP and terlipressin consistently and significantly improve survival in hemorrhagic shock (mortality: 26/174 (15%) in the AVP group versus 164/259 (63%) in the control arms; OR = 0.09; 95% CI 0.05 to 0.15; P for effect < 0.001; P for heterogeneity = 0.30; I₂ = 14%). Conclusions. Results suggest that AVP and terlipressin improve survival in the early phases of animal models of hemorrhagic shock. Vasopressin seems to be more effective than all other treatments, including other vasopressor drugs. These results need to be confirmed by human clinical trials.

The effects of nitroglycerin during cardiopulmonary resuscitation

The outcome for both in-hospital and out-of hospital cardiac arrest remains dismal. Vasopressors are used to increase coronary perfusion pressure and thus facilitate return of spontaneous circulation during cardiopulmonary resuscitation. However, they are associated with a number of potential adverse effects and may decrease endocardial and cerebral organ blood flow. Nitroglycerin has a favourable haemodynamic profile which promotes forward blood flow. Several studies suggest that combined use of nitroglycerin with vasopressors during resuscitation, is associated with increased rates of resuscitation and improved post-resuscitation outcome. This article reviews the effects of nitroglycerin during cardiopulmonary resuscitation and postresuscitation period, as well as the beneficial outcomes of a combination regimen consisting of a vasopressor and a vasodilator, such as nitroglycerin.

Vasopressin decreases neuronal apoptosis during cardiopulmonary resuscitation

The American Heart Association and the European Resuscitation Council recently recommended that vasopressin can be used for cardiopulmonary resuscitation, instead of epinephrine. However, the guidelines do not discuss the effects of vasopressin during cerebral resuscitation. In this study, we intraperitoneally injected epinephrine and/or vasopressin during cardiopulmonary resuscitation in a rat model of asphyxial cardiac arrest. The results demonstrated that, compared with epinephrine alone, the pathological damage to nerve cells was lessened, and the levels of c-Jun N-terminal kinase and p38 expression were significantly decreased in the hippocampus after treatment with vasopressin alone or the vasopressin and epinephrine combination. No significant difference in resuscitation effects was detected between vasopressin alone and the vasopressin and epinephrine combination. These results suggest that vasopressin alone or the vasopressin and epinephrine combination suppress the activation of mitogen-activated protein kinase and c-Jun N-terminal kinase signaling pathways and reduce neuronal apoptosis during cardiopulmonary resuscitation.

Comparison of Two Protocols for Pulseless Cardiopulmonary Arrest: Vasopressin Combined with Epinephrine Versus Epinephrine Alone

Introduction:

Survival from pulseless cardiac arrest typically is dismal. Some suggest that adding vasopressin to epinephrine as a cardiovascular stimulant can improve outcomes.

Problem:

This study compares survival outcomes using epinephrine verses vasopressin and epinephrine in persons with pulseless cardiac arrest.

Methods:

This is a retrospective, cohort evaluation of two resuscitative protocols (P1-epinephrine or P2-vasopressin with epinephrine) in a tiered response, community emergency medical service (EMS) with an approximately 100,000 catchment area. Cases are defined as 18 years or older determined to be in pulseless cardiac arrest. Outcomes were survival to emergency department arrival, to 24 hours, and to hospital discharge. Data were entered into Microsoft Office Excel® and processed using Analyze-it® for continuous and categorical data and Epi-Info® for odds ratios with confidence intervals.

Results:

There were 204 cases (60.3% males and 39.7% females) who met the inclusion criteria. Thirteen cases received electrical therapy only, and were dropped from analysis, leaving 191 (93.6%) who were included in the study; P1 to 85 (44.5%) and P2 to 106 (55.5%). Younger age was associated with improved survival to discharge home in both protocols, p = 0.003 (95% CI = 0.004–0.010). No difference in survival was noted at the levels of emergency department arrival OR 1.42 (95% CI = 0.73, 2.76) p = 0.26; 24 hour survival OR 0.54 (95% CI = 0.22–1.30) p = 0.133, or discharge home OR = 1.81 (95% CI = 0.49–6.88) p = 0.319.

Conclusions:

This study in a community EMS did not demonstrate improved survival with the addition of vasopressin to epinephrine for pulseless cardiac arrest.

Vasopressin rescue for in-pediatric intensive care unit cardiopulmonary arrest refractory to initial epinephrine dosing: a prospective feasibility pilot trial

OBJECTIVES

To assess the feasibility of a large, randomized controlled trial of combination epinephrine-arginine vasopressin for in-pediatric intensive care unit cardiopulmonary arrest refractory to initial epinephrine dosing.

DESIGN

Prospective, pilot, matched controlled clinical trial using exception from informed consent.

SETTING

Pediatric intensive care unit in a university-affiliated tertiary care children's hospital.

PATIENTS

All patients <18 yrs of age admitted to the pediatric intensive care unit with cardiopulmonary arrest requiring chest compressions and epinephrine (0.01 mg/kg) were eligible.

INTERVENTIONS

Patients who remained in cardiopulmonary arrest despite an initial dose of epinephrine received arginine vasopressin (0.8 U/kg) rescue as the second vasopressor, followed by additional epinephrine if needed.

MEASUREMENTS AND MAIN RESULTS

Outcome variables included return of spontaneous circulation (≥20 min), survival at 24 hrs, survival to hospital discharge, and neurologic status at discharge. Favorable neurologic status was defined as Pediatric Cerebral Performance Categories 1, 2, and 3, or no change from admission. Data were compared to a retrospective, matched cohort of patients who experienced cardiopulmonary arrest requiring ≥ two doses of vasopressor, and did not receive arginine vasopressin (n = 20). Of 2,654 patients admitted to the pediatric intensive care unit, 29 (1.1%) had refractory cardiopulmonary arrest: five patients were excluded, 14 missed for inclusion, and ten were enrolled. There was increased 24-hr survival (80% vs. 30%, odds ratio 9.33, 95% confidence interval 1.51-57.65) in arginine vasopressin patients. There was no significant difference in return of spontaneous circulation, survival to hospital discharge, or favorable neurologic status at discharge.

CONCLUSIONS

These pilot data provide support for a larger randomized controlled trial of arginine vasopressin therapy during cardiopulmonary resuscitation for in-hospital pediatric cardiac arrest.

Combination pharmacotherapy improves neurological outcome after asphyxial cardiac arrest

AIM

To study the effects of the combination of adrenaline (epinephrine) and vasopressin compared to adrenaline alone on initial resuscitation success, 24h survival, and neurological outcome in a swine model of asphyxial cardiac arrest (CA).

METHODS

This prospective randomized experimental study was conducted at a laboratory research department. Twenty female Landrace/Large-White pigs, 12-15 weeks of age, were investigated. Asphyxial CA was induced by clamping of the endotracheal tube. After 4min of untreated CA, resuscitation was initiated by unclamping the endotracheal tube, mechanical ventilation, chest compressions and adrenaline (Group A) or a combination of adrenaline with vasopressin (Group A+V) administered intravenously. In case of restoration of spontaneous circulation (ROSC), the animals were monitored for 30min and then observed for 24h.

RESULTS

Hemodynamic variables were measured at baseline during CPR and in the post-resuscitation period. Statistically significant difference was observed in groups A and A+V regarding coronary perfusion pressure (CPP) during the first minute of CPR. In both groups, ROSC and survival rates were comparable (p=NS). Neurological deficit score (NDS) was significantly higher in the combination group 24h following CA (p<0.001). Brain histological damage score (HDS) was also better in the combination group (p<0.001). Total HDS and NDS showed a statistical significant correlation (p<0.001).

CONCLUSIONS

In this porcine model of asphyxial CA, adrenaline alone as well as the combined administration of adrenaline and vasopressin resulted in similar ROSC and survival rates, but the combination of adrenaline and vasopressin resulted in improved neurological and cerebral histopathological outcomes.

Vasopressin for cardiac arrest: meta-analysis of randomized controlled trials

BACKGROUND

Prior meta-analyses-reported results of randomised controlled trials (RCTs) published between 1997 and 2004 failed to show any vasopressin-related benefit in cardiac arrest. Based on new RCT-data and a hypothesis of a potentially increased vasoconstricting efficacy of vasopressin, we sought to determine whether the cumulative, current evidence supports or refutes an overall and/or selective benefit for vasopressin regarding sustained restoration of spontaneous circulation (ROSC), long-term survival, and neurological outcome.

METHODS

Two reviewers independently searched PubMed, EMBASE, and Cochrane Database for RCTs assigning adults with cardiac arrest to treatment with a vasopressin-containing regimen (vasopressin-group) vs adrenaline (epinephrine) alone (control-group) and reporting on long-term outcomes. Data from 4475 patients in 6 high-methodological quality RCTs were analyzed. Subgroup analyses were conducted according to initial cardiac rhythm and time from collapse to drug administration (T(DRUG))<20 min.

RESULTS

Vasopressin vs. control did not improve overall rates of sustained ROSC, long-term survival, or favourable neurological outcome. However, in asystole, vasopressin vs. control was associated with higher long-term survival {odds ratio (OR)=1.80, 95% confidence interval (CI)=1.04-3.12, P=0.04}. In asystolic patients of RCTs with average T(DRUG)<20 min, vasopressin vs. control increased the rates of sustained ROSC (data available from 2 RCTs; OR=1.70, 95% CI=1.17-2.47, P=0.005) and long-term survival (data available from 3 RCTs; OR=2.84, 95% CI=1.19-6.79, P=0.02).

CONCLUSIONS

Vasopressin use in the resuscitation of cardiac arrest patients is not associated with any overall benefit or harm. However, vasopressin may improve the long-term survival of asystolic patients, especially when average T(DRUG) is <20 min.

Lipid emulsion combined with epinephrine and vasopressin does not improve survival in a swine model of bupivacaine-induced cardiac arrest

BACKGROUND

This study sought to evaluate the efficacy of lipid emulsion in reversing bupivacaine-induced cardiovascular collapse when added to a resuscitation protocol that included the use of epinephrine and vasopressin.

METHODS

After induction of general anesthesia and instrumentation, 19 mixed-breed domestic swine had cardiovascular collapse induced by an intravenous bolus of 10 mg/kg bupivacaine. After 5 min of resuscitation including chest compressions, epinephrine (100 microg/kg) and vasopressin (1.5 U/kg), animals were randomized to receive either a bolus of 20% lipid emulsion (4 ml/kg) followed by a continuous infusion (0.5 ml x kg(-1) x min(-1)) or an equal volume of saline. Investigators were blinded to the treatment assignment. The primary endpoint was return of spontaneous circulation (mean arterial pressure of at least 60 mmHg for at least 1 min).

RESULTS

Treatment groups were similar with respect to baseline measurements of weight, sex, and hemodynamic and metabolic variables. The rates of return of spontaneous circulation were similar between groups: (3 of 10) in the lipid group and 4 of 9 in the saline group (P = 0.65). Total serum bupivacaine concentrations were higher in the lipid group at the 10-min timepoint (mean +/- SEM: 23.13 +/- 5.37 ng/ml vs. 15.33 +/- 4.04 ng/ml, P = 0.004). More norepinephrine was required in the lipid group compared to the saline group to maintain a mean arterial pressure above 60 mmHg during the 60-min survival period (mean +/- SEM: 738.6 +/- 94.4 vs.. 487.3 +/- 171.0 microg).

CONCLUSIONS

In this swine model, lipid emulsion did not improve rates of return of spontaneous circulation after bupivacaine-induced cardiovascular collapse.

Comparison of Treatment Modalities for Hemorrhagic Shock

Allogeneic blood resuscitation is the treatment of choice for hemorrhagic shock. When blood is unavailable, plasma expanders, including crystalloids, colloids, and blood substitutes, may be used. Another treatment modality is vasopressin, a vasoconstrictor administered to redistribute blood flow, increase venous return, and maintain adequate cardiac output. While much information exists on systemic function and oxygenation characteristics following treatment with these resuscitants, data on their effects on the microcirculation and correlation of real-time microvascular changes with changes in systemic function and oxygenation in the same animal are lacking. In this study, real-time microvascular changes during hemorrhagic shock treatment were correlated with systemic function and oxygenation changes in a canine hemorrhagic shock model (50-55% total blood loss with a MAP of 45-50 mmHg as a clinical criterion). Following splenectomy and hemorrhage, the dogs were assigned to five resuscitation groups: autologous/shed blood, hemoglobin-based oxygen carrier/Oxyglobin, crystalloid/saline, colloid/Hespan (6% hetastarch), and vasopressin. Systemic function and oxygenation changes were continuously monitored and periodically measured (during various phases of the study) using standard operating room protocols. Computer-assisted intravital video-microscopy was used to objectively analyze and quantify real-time microvascular changes (diameter, red-cell velocity) in the conjunctival microcirculation. Measurements were made during pre-hemorrhagic (baseline), post-hemorrhagic (pre-resuscitation), and post-resuscitation phases of the study. Pre-hemorrhagic microvascular variables were similar in all dogs (venular diameter = 42+/-4 microm, red-cell velocity = 0.55+/-0.5 mm/sec). All dogs showed significant (P < 0.05) post-hemorrhagic microvascular changes: approximately 20% decrease in venular diameter and approximately 30% increase in red-cell velocity, indicative of sympathetic effects arising from substantial blood loss. Microvascular changes correlated with post-hemorrhagic systemic function and oxygenation changes. All resuscitation modalities except vasopressin restored microvascular and systemic function changes close to pre-hemorrhagic values. However, only autologous blood restored oxygenation changes to pre-hemorrhagic levels. Vasopressin treatment resulted in further decreases in venular diameter (approximately 50%) as well as red-cell velocity (approximately 70%) without improving cardiac output. Our results suggested that volume replenishment - not oxygen-carrying capability - played an important role in pre-hospital/en route treatment for hemorrhagic shock. Vasopressin treatment resulted in inadvertent detrimental outcome without the intended benefit.

Vasopressin treatment of verapamil toxicity in the porcine model

INTRODUCTION

Vasopressin is a novel vasopressor agent used for intractable hypotension. There is little published data available on its use in the poisoned patient. We performed a randomized, controlled, blinded trial in a porcine model to study the effects of vasopressin infusion on mean arterial pressure after verapamil poisoning.

METHODS

Eighteen anesthetized monitored swine received a verapamil infusion of 1 mg/kg/hr until the mean arterial pressure (MAP) had decreased to 70% of baseline. At this time, a continuous infusion of either vasopressin (0.01 U/kg/min) or an equal volume of normal saline was initiated. The swine were monitored for 60 minutes after initiation of the study infusion. The primary outcome was MAP.

RESULTS

There was no statistically significant difference between the two groups in MAP, cardiac output or systemic vascular resistance. One half (four of eight) of the animals in the vasopressin group died, compared with 20% (two of ten) of those in the saline group.

CONCLUSIONS

Vasopressin infusion decreased the survival of verapamil-poisoned swine when compared to those treated with saline alone in this experimental model.

Insulin versus vasopressin and epinephrine to treat β-blocker toxicity

OBJECTIVE

We compared insulin and glucose (IN/G) to vasopressin plus epinephrine (V/E) in a pig model of beta-blocker toxicity. Primary outcome was survival over four hours.

METHODS

Ten pigs received a 0.5 mg/kg bolus of propranolol IV followed by a continuous infusion. At the point of toxicity 20 ml/kg normal saline was rapidly infused and the propranolol drip continued at 0.125 mg/kg/min over four hours of resuscitation. Each pig was randomized to either IN/G or V/E. The V/E group began with epinephrine at 10 mcg/kg/min titrated up by 10 mcg/kg/min every 10 min to 50 mcg/kg/min or until baseline was obtained. Simultaneously, these pigs received vasopressin at 0.0028 units/kg/min, titrated upwards every 10 min to 0.014 units/kg/min or until baseline was obtained. The IN/G group began with a 2 units/kg/hr drip and increased by 2 units every 10 minutes to 10 units/kg/hr, or until baseline hemodynamics were obtained. CO, SVR, systolic blood pressure, HR, MAP, glucose, and potassium were monitored. Glucose was given for values <60 mg/dl.

RESULTS

The study was terminated early due to marked survival differences after five pigs were entered in each group. All IN/G group pigs survived four hours. All V/E group pigs died within 90 min. CO in the IN/G group increased throughout the four hours, rising above pre-propranolol levels, while MAP, SBP, and SVR all trended slightly downward. CO in the V/E group dropped until death, while MAP, SBP, and SVR rose precipitously until 30-60 minutes when these dropped abruptly until death. Glucose was required in the IN/G group.

CONCLUSION

In this swine model, IN/G is superior to V/E to treat beta-blocker toxicity. IN/G has marked inotropic properties while the vasopressor effects of V/E depress CO and contribute to death. Increasing SVR in this condition is detrimental to survival.

Increasing CPR duration prior to first defibrillation does not improve return of spontaneous circulation or survival in a swine model of prolonged ventricular fibrillation

INTRODUCTION

The optimum duration of cardiopulmonary resuscitation (CPR) prior to first rescue shock is unknown. Clinical trials have used 90 and 180 s. Neither of these durations may be optimal. We sought to determine the optimum duration of CPR prior to first defibrillation attempt and whether this varied depending on the duration of ventricular fibrillation (VF). In this porcine model of basic life support, our outcomes were rates of return of spontaneous circulation (ROSC), survival, and coronary perfusion pressure (CPP).

METHODS

We anesthetized and instrumented 45 swine and then induced VF. After 5 or 8 min of untreated VF, we randomized the swine to mechanical CPR for 90, 180, or 300 s. A single rescue shock (150 J biphasic) was then administered. If this shock failed, 2 min of mechanical CPR were completed prior to the next rescue shock. CPP was calculated for each 30s epoch. ROSC was defined as a blood pressure >80 mmHg sustained for 60s. Survival was defined as sustained ROSC for 20 min. Data were analyzed with descriptive statistics, Fisher's exact test, and ANOVA.

RESULTS

In the 5 min VF cohort, the rate of ROSC did not differ between the three groups (90 s: 25%; 180 s: 38%; 300 s: 38%, p>.05). Survival rates did not differ (90 s: 25%; 180 s: 25%; 300 s: 25%, p>0.05). In the 8 min VF cohort, no animals experienced ROSC or survival. CPP were calculated by 30s epoch and did not differ between the three groups (p>0.05). CPPs decline after 180 s of CPR.

CONCLUSIONS

ROSC and survival were equivalent regardless of VF duration and CPR duration. When CPR begins late, CPPs are low, stressing the importance of early CPR. We do not recommend 300 s of CPR unless a defibrillator is unavailable.

Vasopressin improves survival in a porcine model of abdominal vascular injury

Introduction

We sought to determine and compare the effects of vasopressin, fluid resuscitation and saline placebo on haemodynamic variables and short-term survival in an abdominal vascular injury model with uncontrolled haemorrhagic shock in pigs.

Methods

During general anaesthesia, a midline laparotomy was performed on 19 domestic pigs, followed by an incision (width about 5 cm and depth 0.5 cm) across the mesenterial shaft. When mean arterial blood pressure was below 20 mmHg, and heart rate had declined progressively, experimental therapy was initiated. At that point, animals were randomly assigned to receive vasopressin (0.4 U/kg; n = 7), fluid resuscitation (25 ml/kg lactated Ringer's and 25 ml/kg 3% gelatine solution; n = 7), or a single injection of saline placebo (n = 5). Vasopressin-treated animals were then given a continuous infusion of 0.08 U/kg per min vasopressin, whereas the remaining two groups received saline placebo at an equal rate of infusion. After 30 min of experimental therapy bleeding was controlled by surgical intervention, and further fluid resuscitation was performed. Thereafter, the animals were observed for an additional hour.

Results

After 68 ± 19 min (mean ± standard deviation) of uncontrolled bleeding, experimental therapy was initiated; at that time total blood loss and mean arterial blood pressure were similar between groups (not significant). Mean arterial blood pressure increased in both vasopressin-treated and fluid-resuscitated animals from about 15 mmHg to about 55 mmHg within 5 min, but afterward it decreased more rapidly in the fluid resuscitation group; mean arterial blood pressure in the placebo group never increased. Seven out of seven vasopressin-treated animals survived, whereas six out of seven fluid-resuscitated and five out of five placebo pigs died before surgical intervention was initiated (P < 0.0001).

Conclusion

Vasopressin, but not fluid resuscitation or saline placebo, ensured short-term survival in this vascular injury model with uncontrolled haemorrhagic shock in sedated pigs.

Vasopressin and epinephrine in the treatment of cardiac arrest: an experimental study

BACKGROUND

Epinephrine remains the drug of choice for cardiopulmonary resuscitation. The aim of the present study is to assess whether the combination of vasopressin and epinephrine, given their different mechanisms of action, provides better results than epinephrine alone in cardiopulmonary resuscitation.

METHODS

Ventricular fibrillation was induced in 22 Landrace/Large-White piglets, which were left untreated for 8 minutes before attempted resuscitation with precordial compression, mechanical ventilation and electrical defibrillation. Animals were randomized into 2 groups during cardiopulmonary resuscitation: 11 animals who received saline as placebo (20 ml dilution, bolus) + epinephrine (0.02 mg/kg) (Epi group); and 11 animals who received vasopressin (0.4 IU/kg/20 ml dilution, bolus) + epinephrine (0.02 mg/kg) (Vaso-Epi group). Electrical defibrillation was attempted after 10 minutes of ventricular fibrillation.

RESULTS

Ten of 11 animals in the Vaso-Epi group restored spontaneous circulation in comparison to only 4 of 11 in the Epi group (p = 0.02). Aortic diastolic pressure, as well as, coronary perfusion pressure were significantly increased (p < 0.05) during cardiopulmonary resuscitation in the Vaso-Epi group.

CONCLUSION

The administration of vasopressin in combination with epinephrine during cardiopulmonary resuscitation results in a drastic improvement in the hemodynamic parameters necessary for the return of spontaneous circulation.

Emergency preservation and resuscitation improve survival after 15 minutes of normovolemic cardiac arrest in pigs*

OBJECTIVE

Outcome after prolonged normovolemic cardiac arrest is poor, and new resuscitation strategies have to be found. We hypothesized that the induction of deep hypothermia for emergency preservation and resuscitation (EPR) during prolonged cardiac arrest, before the start of reperfusion, will mitigate the deleterious cascades leading to neuronal death and will thus improve outcome.

DESIGN

Prospective experimental study.

SETTING

University research laboratory.

SUBJECTS

Thirteen pigs, Large White breed (27-37 kg).

INTERVENTIONS

After 15 mins of ventricular fibrillation, pigs were subjected to 1) EPR (n = 6), 20 mins of hypothermic stasis induced with a cold saline aortic flush; or 2) 20 mins of conventional resuscitation (n = 7). Then cardiopulmonary bypass was initiated in both groups, followed by defibrillation. Controlled ventilation and mild hypothermia were continued for 20 hrs; survival was for 9 days. For neurologic evaluation, neurologic deficit score (100% = brain dead, 0-10% = normal), overall performance category (1 = normal, 5 = dead or brain dead), and brain histologic damage score were used.

MEASUREMENTS AND MAIN RESULTS

In the EPR group, brain temperature decreased from 38.5 degrees C +/- 0.2 degrees C to 16.7 degrees C +/- 2.5 degrees C within 235 +/- 27 secs. Five animals achieved restoration of spontaneous circulation and survived to 9 days: two pigs with overall performance category 2 and three pigs with overall performance category 3. Their neurologic deficit score was 45% (interquartile range 35, 50) and histologic damage score was 142 (interquartile range 109, 159). In the control group, four pigs achieved restoration of spontaneous circulation: one survived to 9 days with overall performance category 3, neurologic deficit score 45%, and histologic damage score 226 (restoration of spontaneous circulation, p = .6; survival, p = .03; overall performance category, p = .02).

CONCLUSIONS

EPR is feasible in an experimental pig model and improves survival after prolonged cardiac arrest in pigs. Further experimental studies are needed before this concept can be brought into clinical practice.

Revised resuscitation guidelines: Adrenaline versus adrenaline/vasopressin in a pig model of cardiopulmonary resuscitation—A randomised, controlled trial

BACKGROUND

Synergistic effects of adrenaline (epinephrine) and vasopressin may be beneficial during cardiopulmonary resuscitation. However, it is unknown whether either adrenaline alone or an alternating administration of adrenaline and vasopressin is better for restoring vital organ perfusion following basic life support (BLS) according to the revised algorithm with a compression-to-ventilation (c/v) ratio of 30:2.

MATERIAL AND METHODS

After 4min of ventricular fibrillation, and 6min of BLS with a c/v ratio of 30:2, 16 pigs were randomised to receive either 45microg/kg adrenaline, or alternating 45microg/kg adrenaline and 0.4U/kg vasopressin, respectively.

RESULTS

Coronary perfusion pressure (mean+/-S.D.) 20 and 25min after cardiac arrest was 7+/-4 and 5+/-3mm Hg after adrenaline, and 25+/-2 and 14+/-3mm Hg after adrenaline/vasopressin (p<0.001 and <0.01 versus adrenaline), respectively. Cerebral perfusion pressure was 23+/-7 and 19+/-9mm Hg after adrenaline, and 40+/-10 and 33+/-7mm Hg after adrenaline/vasopressin (p<0.001 and <0.01 versus adrenaline), and cerebral blood flow was 30+/-10 and 27+/-11% of baseline after adrenaline, and 65+/-40 and 50+/-31% of baseline after adrenaline/vasopressin (p<0.05 versus adrenaline), respectively. Return of spontaneous circulation (ROSC) did not differ significantly between the adrenaline group (0/8) and the adrenaline/vasopressin group (3/8).

CONCLUSION

Adrenaline/vasopressin resulted in higher coronary and cerebral perfusion pressures, and cerebral blood flow, while ROSC was comparable.

Drug administration in animal studies of cardiac arrest does not reflect human clinical experience

INTRODUCTION

To date, there is no evidence showing a benefit from any advanced cardiac life support (ACLS) medication in out-of-hospital cardiac arrest (OOHCA), despite animal data to the contrary. One explanation may be a difference in the time to first drug administration. Our previous work has shown the mean time to first drug administration in clinical trials is 19.4min. We hypothesized that the average time to drug administration in large animal experiments occurs earlier than in OOHCA clinical trials.

METHODS

We conducted a literature review between 1990 and 2006 in MEDLINE using the following MeSH headings: swine, dogs, resuscitation, heart arrest, EMS, EMT, ambulance, ventricular fibrillation, drug therapy, epinephrine, vasopressin, amiodarone, lidocaine, magnesium, and sodium bicarbonate. We reviewed the abstracts of 331 studies and 197 full manuscripts. Exclusion criteria included: non-peer reviewed, all without primary animal data, and traumatic models. From these, we identified 119 papers that contained unique information on time to medication administration. The data are reported as mean, ranges, and 95% confidence intervals. Mean time to first drug administration in animal laboratory studies and clinical trials was compared with a t-test. Regression analysis was performed to determine if time to drug predicted ROSC.

RESULTS

Mean time to first drug administration in 2378 animals was 9.5min (range 3.0-28.0; 95% CI around mean 2.78, 16.22). This is less than the time reported in clinical trials (19.4min, p<0.001). Time to drug predicted ROSC (odds ratio 0.844; 95% CI 0.738, 0.966).

CONCLUSION

Shorter drug delivery time in animal models of cardiac arrest may be one reason for the failure of animal studies to translate successfully into the clinical arena.

Haemodynamic effects of adrenaline (epinephrine) depend on chest compression quality during cardiopulmonary resuscitation in pigs

BACKGROUND

Adrenaline (epinephrine) is used during cardiopulmonary resuscitation (CPR) based on animal experiments without supportive clinical data. Clinically CPR was reported recently to have much poorer quality than expected from international guidelines and what is generally done in laboratory experiments. We have studied the haemodynamic effects of adrenaline during CPR with good laboratory quality and with quality simulating clinical findings and the feasibility of monitoring these effects through VF waveform analysis.

METHODS AND RESULTS

After 4 min of cardiac arrest, followed by 4 min of basic life support, 14 pigs were randomised to ClinicalCPR (intermittent manual chest compressions, compression-to-ventilation ratio 15:2, compression depth 30-38 mm) or LabCPR (continuous mechanical chest compressions, 12 ventilations/min, compression depth 45 mm). Adrenaline 0.02 mg/kg was administered 30 s thereafter. Plasma adrenaline concentration peaked earlier with LabCPR than with ClinicalCPR, median (range), 90 (30, 150) versus 150 (90, 270) s (p = 0.007), respectively. Coronary perfusion pressure (CPP) and cortical cerebral blood flow (CCBF) increased and femoral blood flow (FBF) decreased after adrenaline during LabCPR (mean differences (95% CI) CPP 17 (6, 29) mmHg (p = 0.01), FBF -5.0 (-8.8, -1.2) ml min(-1) (p = 0.02) and median difference CCBF 12% of baseline (p = 0.04)). There were no significant effects during ClinicalCPR (mean differences (95% CI) CPP 4.7 (-3.2, 13) mmHg (p = 0.2), FBF -0.2 (-4.6, 4.2) ml min(-1)(p = 0.9) and CCBF 3.6 (-1.8, 9.0)% of baseline (p = 0.15)). Slope VF waveform analysis reflected changes in CPP.

CONCLUSION

Adrenaline improved haemodynamics during laboratory quality CPR in pigs, but not with quality simulating clinically reported CPR performance.

Evolving role of vasopressin in the treatment of cardiac arrest

Sudden cardiac arrest is a major public heath problem, affecting more than 450,000 individuals annually. Response time and the initiation of cardiopulmonary resuscitation (CPR) remain the most important factors determining successful revival. During resuscitation, sympathomimetics are given to enhance cerebral and coronary perfusion pressures in an attempt to achieve restoration of spontaneous circulation. Epinephrine has been the preferred vasopressor since the inception of advanced cardiac life support, although the lack of definitive evidence regarding its effectiveness has created much controversy surrounding its use, including the optimum dosage. Vasopressin is an alternative vasopressor that, when given at high doses, causes vasoconstriction by directly stimulating smooth muscle V1 receptors. The 2000 American Heart Association (AHA) guidelines commented that vasopressin is a reasonable first-line vasopressor in patients with ventricular fibrillation or pulseless ventricular tachycardia. Since release of those guidelines, additional human studies support an expanded role for vasopressin, whereas other studies cast doubt regarding its efficacy compared with epinephrine. The AHA recently released revised guidelines for CPR and emergency cardiovascular care. The consensus was that vasopressors should remain a part of pulseless sudden cardiac arrest management, with epinephrine 1 mg every 3-5 minutes being the recommended adrenergic of choice. In these revised guidelines, the role of vasopressin expanded beyond previous recommendations, despite the recommendation being downgraded to class indeterminate. The guidelines comment that one dose of vasopressin 40 U may replace the first or second dose of epinephrine in all pulseless sudden cardiac arrest scenarios, including asystole and pulseless electrical activity. A consistent theme with all vasopressors in sudden cardiac arrest is that additional studies are necessary to clearly document greater efficacy compared with no treatment. Further evaluation is warranted to better assess the role of vasopressin in asystolic sudden cardiac arrest, as well as its use with epinephrine, and to determine its optimal timing of administration and potential synergistic effects.

Usefulness of vasopressin administered with epinephrine during out-of-hospital cardiac arrest

Vasopressin administration has been suggested during cardiopulmonary resuscitation, and a previous clinical trial has suggested that vasopressin is most effective when administered with epinephrine. Adult subjects (n = 325) who received > or =1 dose of intravenous epinephrine during cardiopulmonary resuscitation for nontraumatic, out-of-hospital cardiac arrest were randomly assigned to receive 40 IU of vasopressin (n = 167) or placebo (n = 158) as soon as possible after the first dose of epinephrine. The rate of return of pulses was similar between the vasopressin and placebo groups (31% vs 30%), as was the presence of pulses at the emergency department (19% vs 23%). No subgroup appeared to be differentially affected, and no effect of vasopressin was evident after adjustment for other clinical variables. Additional open-label vasopressin was administered by a physician after the study drug for 19 subjects in the placebo group and 27 subjects in the vasopressin group. Results were similar if these subjects were excluded or were assigned to an actual drug received. Survival duration for subjects admitted to the hospital did not differ between groups. In conclusion, vasopressin administered with epinephrine does not increase the rate of return of spontaneous circulation.

An observational study of vasopressin infusion during uncontrolled haemorrhagic shock in a porcine trauma model: Effects on bowel function

The effects of vasopressin on the gut in a porcine uncontrolled haemorrhagic shock model are described. In eight anaesthetised pigs, a liver laceration was performed; when haemorrhagic shock was decompensated, all animals received 0.4 IU/kg vasopressin, followed by 0.08 IU/kg min over 30 min, which maintained a mean arterial blood pressure >40 mmHg. Subsequent surgical intervention, infusion of whole blood and fluids resulted in a stable cardiocirculatory status. Three hours after stabilisation, all pigs developed non-bloody diarrhoea which converted into normal bowel movements within 24 h. All histological samples retained 7 days after the experiment revealed no histopathological changes. In conclusion, in this small observational study of uncontrolled porcine haemorrhagic shock, a resuscitation strategy that included high dose vasopressin was associated with transient diarrhoea and good long term survival.

Brain tissue oxygen pressure and cerebral metabolism in an animal model of cardiac arrest and cardiopulmonary resuscitation

OBJECTIVE

Direct measurement of brain tissue oxygenation (PbtO2) is established during spontaneous circulation, but values of PbtO2 during and after cardiopulmonary resuscitation (CPR) are unknown. The purpose of this study was to investigate: (1) the time-course of PbtO2 in an established model of CPR, and (2) the changes of cerebral venous lactate and S-100B.

METHODS

In 12 pigs (12-16 weeks, 35-45 kg), ventricular fibrillation (VF) was induced electrically during general anaesthesia. After 4 min of untreated VF, all animals were subjected to CPR (chest compression rate 100/min, FiO2 1.0) with vasopressor therapy after 7, 12, and 17 min (vasopressin 0.4, 0.4, and 0.8 U/kg, respectively). Defibrillation was performed after 22 min of cardiac arrest. After return of spontaneous circulation (ROSC), the pigs were observed for 1h.

RESULTS

After initiation of VF, PbtO2 decreased compared to baseline (mean +/- SEM; 22 +/- 6 versus 2 +/- 1 mmHg after 4 min of VF; P < 0.05). During CPR, PbtO2 increased, and reached maximum values 8 min after start of CPR (25 +/- 7 mmHg; P < 0.05 versus no-flow). No further changes were seen until ROSC. Lactate, and S-100B increased during CPR compared to baseline (16 +/- 2 versus 85 +/- 8 mg/dl, and 0.46 +/- 0.05 versus 2.12 +/- 0.40 microg/l after 13 min of CPR, respectively; P < 0.001); lactate remained elevated, while S-100B returned to baseline after ROSC.

CONCLUSIONS

Though PbtO2 returned to pre-arrest values during CPR, PbtO2 and cerebral lactate were lower than during post-arrest reperfusion with 100% oxygen, which reflected the cerebral low-flow state during CPR. The transient increase of S-100B may indicate a disturbance of the blood-brain-barrier.

Time to give the first medication during resuscitation in out-of-hospital cardiac arrest

OBJECTIVE

There is no evidence showing an impact from any advanced cardiac life support (ACLS) medications on patient survival following cardiac arrest. One potential reason for a lack of such benefit may be medication timing. We formed the hypothesis that medications are given late after rescuer arrival, limiting any benefit. We performed a meta-analysis to determine the time from emergency medical services (EMS) dispatch to first medication administration, regardless of route, during out-of-hospital cardiac arrest (OOHCA). Then, the mean time and ranges of reported study medication delivery in clinical trials where medication was the experimental intervention was determined.

METHODS

We conducted a comprehensive literature review between January 1990 and August 2005 in MEDLINE using the following MeSH headings: cardiopulmonary resuscitation, cardiac arrest, heart arrest, EMS, EMT, ambulance, and the names of all ACLS medications. We reviewed the abstracts of 632 studies and full manuscripts of 248 published papers. We eliminated the following articles from further analysis: non-peer reviewed; all without human primary data (includes review articles, guidelines or consensus manuscripts, editorials, or simulation studies); animal data; case reports. We used no language restriction. From this search, our independent reviewers found 17 papers that contained information on time to medication administration.

RESULTS

We analyzed reporting of drug delivery time to 7617 patients in 32 different emergency medical services systems. Time to first medication delivery by any route was a mean of 17.7 min (range 10.0-25.0; 95% CI around mean 10.6, 24.8). Time to intravenous experimental medication administration was a mean of 19.4 min (range 13.3-25.0; 95% CI around mean 12.8, 25.9).

CONCLUSIONS

Medications are given late during out-of-hospital cardiac arrest, even in cohorts where drug delivery is a key study intervention.

Effects of combined administration of vasopressin, epinephrine, and norepinephrine during cardiopulmonary resuscitation in pigs*

OBJECTIVE

Synergistic effects of epinephrine and vasopressin may be of benefit during cardiopulmonary resuscitation. However, cerebral perfusion was decreased when epinephrine was combined with vasopressin compared with vasopressin alone. Although a combined infusion of norepinephrine and vasopressin improves hemodynamic variables compared with norepinephrine alone during sepsis, it is unknown whether norepinephrine in addition to vasopressin and epinephrine changes vital organ perfusion during cardiopulmonary resuscitation.

DESIGN

Prospective, randomized animal study.

SETTING

: University hospital research laboratory.

SUBJECTS

Twenty-one domestic pigs.

INTERVENTIONS

After 4 mins of ventricular fibrillation and 3 mins of basic life support, the pigs were randomly assigned to receive either 200 microg/kg epinephrine, 0.4 units/kg vasopressin alone, or 45 microg/kg norepinephrine plus 45 microg/kg epinephrine plus 0.4 units/kg vasopressin before defibrillation.

MEASUREMENTS AND MAIN RESULTS

Organ perfusion was determined by radiolabeled microspheres. Myocardial blood flow (mean +/- sem) before and 90 secs and 5 mins after drug administration was 8 +/- 2, 25 +/- 6, and 7 +/- 1 mL/min/100 g after high-dose epinephrine, 12 +/- 1, 75 +/- 7, and 60 +/- 10 mL/min/100 g after vasopressin, and 9 +/- 2, 95 +/- 26, and 46 +/- 15 mL/min/100 g after vasopressin/epinephrine/norepinephrine, respectively (p < .05 at 90 secs and 5 mins vasopressin vs. epinephrine and vasopressin/epinephrine/norepinephrine vs. epinephrine). At the same time points, cerebral blood flow was 8 +/- 2, 23 +/- 3, and 17 +/- 3 mL/min/100 g after epinephrine, 11 +/- 3, 55 +/- 7, and 52 +/- 7 mL/min/100 g after vasopressin, and 11 +/- 4, 67 +/- 13, and 53 +/- 12 mL/min/100 g after vasopressin/epinephrine/norepinephrine, respectively (p < .05 at 90 secs and 5 mins vasopressin vs. epinephrine and vasopressin/epinephrine/norepinephrine vs. epinephrine). Two of seven animals in the epinephrine group, four of seven animals in the vasopressin/epinephrine/norepinephrine group, and seven of seven animals in the vasopressin group could be successfully resuscitated (p < .05 vasopressin vs. epinephrine).

CONCLUSIONS

Vasopressin with or without epinephrine and norepinephrine resulted in higher myocardial and cerebral perfusion than epinephrine alone, but there was no benefit in adding norepinephrine to vasopressin and epinephrine with regard to cardiac and cerebral blood flow during cardiopulmonary resuscitation.

Critical Care Providers’ Perceptions of the Use of Vasopressin in Cardiac Arrest

• Background Although published algorithms and guidelines list epinephrine and vasopressin as either/or choices for treatment of ventricular fibrillation and/or pulseless ventricular tachycardia, little is known about how critical care providers respond to this recommendation.

• Objectives To assess the use of vasopressin as a first-line drug of choice for ventricular fibrillation and/or pulseless ventricular tachycardia and describe factors that may influence decision making for using vasopressin.

• Methods A convenience sample from 4 academic medical centers in the United States was recruited to complete a 20-item survey on demographic factors such as year of last Advanced Cardiac Life Support (ACLS) provider course, specialty certification, predominant practice responsibility, and beliefs related to the use of vasopressin for cardiac arrest. Descriptive statistics, Pearson correlation analysis, and logistic regression were used to analyze the data.

• Results A total of 214 critical care providers (80% registered nurses) completed the survey. Year of last ACLS course (r = −0.188, P = .006) was a significant demographic factor, and behavioral beliefs (attitude about using vasopressin) had the strongest relationship (r = 0.687, P &lt; .001) and were the best predictor for intentions to use or recommend the use of vasopressin (beta=0.589, P&lt;.001).

• Conclusions Despite the recommendation for vasopressin as an agent equivalent to epinephrine for treatment of ventricular fibrillation and/or pulseless ventricular tachycardia, 63% of respondents used epinephrine as a first-line drug of choice. More research is needed to address the classification system for interpreting the quality of evidence that may influence practice.

Vasopressin in the ICU

PURPOSE OF THE REVIEW

Vasopressin is one of the most important endogenously released stress hormones during shock. In this review, studies published in the past year that add to our understanding of the use of vasopressin in the ICU are discussed.

RECENT FINDINGS

Endogenous vasopressin levels are inappropriately low in adults with severe sepsis but not in children with meningococcal septic shock. Vasopressin but not norepinephrine improved renal blood flow and oxygen delivery and prolonged survival in animal models of septic shock. In human vasodilatory shock, the combination of low-dose vasopressin and norepinephrine was found to be safe and effective. In humans, vasopressin can cause gastrointestinal hypoperfusion and ischemic skin lesions. In hypodynamic animal models of sepsis vasopressin compromised oxygen delivery and decreased systemic and gut blood flow.High-dose bolus vasopressin appeared promising in animal studies of hemorrhagic shock and cardiopulmonary arrest and in a large, randomized clinical trial of vasopressin versus epinephrine in human cardiopulmonary arrest with asystole. However, poor neurologic outcomes raised controversy in introducing vasopressin into CPR guidelines.

SUMMARY

There is growing evidence that vasopressin infusion in septic shock is safe and effective. Several studies published this year support the hypothesis that vasopressin should be used as a continuous low-dose infusion (between 0.01 and 0.04 U/min in adults) and not titrated as a single vasopressor agent. However, multiple studies highlight the clinical equipoise that exists regarding the use of vasopressin in vasodilatory shock. Guidelines on management of septic shock recommend "cautious use of vasopressin pending further studies."

Vasopressin administered with epinephrine is associated with a return of a pulse in out-of-hospital cardiac arrest

OBJECTIVE

Recent data suggest that using vasopressin in combination with epinephrine (adrenaline) may improve treatment of out-of-hospital cardiac arrest. This study examined local experience with the combination of epinephrine and vasopressin administration.

METHODS

Data were obtained from an urban, municipal emergency medical service that does not include vasopressin in its formulary. A physician is dispatched to the scene of all cardiac arrest patients treated by this system. Vasopressin could be administered in addition to epinephrine to subjects with out-of-hospital cardiac arrest by the on-scene physician. Demographic information, drug administration and return of pulses were abstracted from patient care records for a 1-year interval. Multivariate logistic regression was used to assess the relationship between vasopressin use and outcomes.

RESULTS

During the study period, data were available for 298 subjects receiving epinephrine-only (n=231, 78%), a combination of 40 IU vasopressin and epinephrine (n=37, 12%) or no vasopressor drugs (n=30, 10%). Among patients receiving vasopressor drugs, pulse was restored for 74 subjects (28%), and 56 subjects (21%) had a pulse on arrival at the hospital. Return of pulses was associated with witnessed collapse, bystander CPR, and an initial ECG rhythm of ventricular fibrillation or tachycardia. Subjects receiving vasopressin and epinephrine were more likely to have a return of pulses during the resuscitation (LR: 2.73; 95% CI: 1.24, 6.03) and at hospital arrival (3.85; 1.71, 8.65) than subjects treated with epinephrine alone.

CONCLUSIONS

There is an association between using vasopressin in combination with epinephrine and restoration of circulation after out-of-hospital cardiac arrest.