Effects of vasopressin and epinephrine on splanchnic blood flow and renal function during and after cardiopulmonary resuscitation in pigs

Intravenous vs. intraosseous vascular access during out-of-hospital cardiac arrest - protocol for a randomised clinical trial

Objective

During cardiac arrest, current guidelines recommend attempting intravenous access first and to consider intraosseous access if intravenous access is unsuccessful or impossible. However, these recommendations are only based on very low-certainty evidence. Therefore, the "Intravenous vs Intraosseous Vascular Access During Out-of-Hospital Cardiac Arrest" (IVIO) trial aims to determine whether there is a difference in patient outcomes depending on the type of vascular access attempted during out-of-hospital cardiac arrest. This current article describes the clinical IVIO trial.

Methods

The IVIO trial is an investigator-initiated, randomised trial of intravenous vs. intraosseous vascular access during adult non-traumatic out-of-hospital cardiac arrest in Denmark. The intervention will consist of minimum two attempts (if unsuccessful on the first attempt) to successfully establish intravenous or intraosseous vascular access during cardiac arrest. The intraosseous group will be further randomised to the humeral or tibial site. The primary outcome is sustained return of spontaneous circulation and key secondary outcomes include survival and survival with a favourable neurological outcome at 30 days. A total of 1,470 patients will be included.

Results

The trial started in March 2022 and the last patient is anticipated to be included in the spring of 2024. The primary results will be reported after 90-day follow-up and are anticipated in mid-2024.

Conclusion

The current article describes the design of the Danish IVIO trial. The findings of this trial will help inform future guidelines for selecting the optimal vascular access route during out-of-hospital cardiac arrest.

The association of early diarrhea after successful resuscitation following out-of-hospital cardiac arrest with neurological outcome: A retrospective observational study

Gastrointestinal ischemia with reperfusion tissue injury contributes to post-cardiac arrest syndrome. We hypothesized that diarrhea is a symptom of intestinal ischemia/reperfusion injury and investigated whether the occurrence of early diarrhea (≤12 hours) after successful cardiopulmonary resuscitation is associated with an unfavorable neurological outcome.We analyzed data from the Vienna Clinical Cardiac Arrest Registry. Inclusion criteria comprised ≥18 years of age, a witnessed, non-traumatic out-of-hospital cardiac arrest, return of spontaneous circulation (ROSC), initial shockable rhythm, and ST-segment elevation in electrocardiogram after ROSC with consecutive coronary angiography. Patients with diarrhea caused by other factors (e.g., infections, antibiotic treatment, or chronic diseases) were excluded. The primary endpoint was neurological function between patients with or without "early diarrhea" (≤12 hours after ROSC) according to cerebral performance categories.We included 156 patients between 2005 and 2012. The rate of unfavorable neurologic outcome was higher in patients with early diarrhea (67% vs 37%). In univariate analysis, the crude odds ratio for unfavorable neurologic outcome was 3.42 (95% confidence interval, 1.11-10.56, P = .03) for early diarrhea. After multivariate adjustment for traditional prognostication markers the odds ratio of early diarrhea was 5.90 (95% confidence interval, 1.28-27.06, P = .02).In conclusion, early diarrhea within 12 hours after successful cardiopulmonary resuscitation was associated with an unfavorable neurological outcome.

Effect of Low-Dose Vasopressin Infusion on Vital Organ Blood Flow in the Conscious Normal and Septic Sheep

The effect of low-dose vasopressin (AVP) on vital regional circulations may be clinically relevant but has not been fully described. We sought to determine the effect of low-dose AVP on systemic haemodynamics, coronary, mesenteric and renal circulations in the conscious normal and septic mammal.

We studied seven Merino sheep using a prospective randomized cross-over double-blind placebo-controlled animal design. We inserted flow probes around aorta, coronary, mesenteric and renal arteries and, three weeks later, we infused low-dose AVP (0.02 IU/min) or placebo in the normal and septic state induced by intravenous E.coli. In normal sheep, AVP (0.02 IU/min) induced a 17% decrease in mesenteric blood flow (393.0±134.9 vs 472.1± 163.8 ml/min, P<0.05) and a 14% decrease in mesenteric conductance (P<0.05). In septic sheep, AVP decreased heart rate and cardiac output by 28% and 22%, respectively (P<0.05). It also decreased mesenteric blood flow and mesenteric conductance by 23% (flow: 468.5±159.7 vs 611.3±136.3 ml/min, P<0.05; conductance: 6.3±2.7 vs 8.2±2.7 ml/min/mmHg; P<0.05). Renal blood flow was unchanged but urine output and creatinine clearance increased (P<0.05). We conclude that low-dose AVP infusion has similar effects in the normal and septic mammalian circulation: bradycardia, decreased cardiac output, decreased mesenteric blood flow and conductance and increased urine output and creatinine clearance. This information is important to clinicians considering its administration in humans.

Evaluation of capillary leakage after vasopressin resuscitation in a hemorrhagic shock model

Background

Hemorrhagic shock (HS) is a major threat to patients with trauma and spontaneous bleeding. The aim of the study was to investigate early effects of vasopressin on metabolic and hemodynamic parameters and endothelium permeability by measuring capillary leakage compared to those of other resuscitation strategies in a HS model.

Methods

Forty-five Sprague-Dawley rats were randomized into five groups: S group (n = 5), sham-operated rats without shock or resuscitation; HS group (n = 10), HS and no resuscitation; RL group (n = 10), HS and resuscitation with Ringer’s lactate (RL); RLB group (n = 10), HS and resuscitation with two-third shed blood plus RL; and vasopressin group (n = 10), HS and resuscitation with RL, followed by continuous infusion of 0.04 U/kg/min vasopressin. The effects of resuscitation on hemodynamic parameters [mean arterial pressure (MAP), superior mesenteric artery blood flow (MBF), and mesenteric vascular resistances (MVR)], arterial blood gases, bicarbonate, base deficit, and lactate levels as well as on capillary leakage in the lung, ileum, and kidney were investigated. Capillary leakage was evaluated with Evans blue dye extravasation.

Results

In the vasopressin group, the MAP was higher than in the RL and RLB groups (p < 0.001), while MBF was decreased (p < 0.001). MVR were increased only in the vasopressin group (p < 0.001). Capillary leakage was increased in the lungs of the animals in the vasopressin group compared to that in the lungs of animals in the RLB group (p < 0.05); this increase was associated with the lowest partial pressure of oxygen (p < 0.05). Conversely, decreased capillary leakage was observed with vasopressin in the ileum (p < 0.05). Increased capillary leakage was observed in the kidney in the RLB and vasopressin groups (p < 0.05). Lastly, vasopressin use was associated with higher base deficit and lactate levels when compared to the RL and RLB groups (p < 0.001).

Conclusion

Although vasopressin was proposed as a vasoactive drug for provisional hemodynamic optimization in the early phase of HS resuscitation, the overall findings of this experimental study focus on the possible critical side effects of vasopressin on metabolic parameters and endothelium permeability.

Non-occlusive mesenteric ischaemia in out of hospital cardiac arrest survivors

BACKGROUND AND AIM OF THE STUDY

Non-occlusive mesenteric ischaemia (NOMI) is characterised by hypoperfusion of the intestines without evidence of mechanical obstruction, potentially leading to extensive ischaemia and necrosis. Low cardiac output appears to be a major risk factor. Cardiopulmonary resuscitation aims at restoring blood flow after cardiac arrest. However, post restoration of spontaneous circulation, myocardial stunning limits immediate recovery of sufficient cardiac function. Since after successful cardiopulmonary resuscitation patients are often ventilated and sedated, NOMI might be underdiagnosed and potentially life-saving treatment delayed.

MATERIAL AND METHODS

A prospectively maintained multi-purpose cohort of out of hospital cardiac arrest survivors, who had successful restoration of spontaneous circulation, was used for this retrospective database analysis. Patients' charts were screened for clinical, radiological or pathological evidence of NOMI and clinical data were collected.

RESULTS

Between 2000 and 2014, 1780 patients who were successfully resuscitated after out of hospital cardiac arrest were screened for NOMI. Twelve patients (0.68 %) suffered from NOMI and six of those died (50 %). Patients suffering from NOMI tended to have a longer duration until restoration of spontaneous circulation (27 vs. 20 min, p=0.128) and had significantly higher lactate (14 mmol/l vs. 8 mmol/l, p=0.002) and base deficit levels at admission (-17 vs. -10, p=0.012). Median leukocyte counts in NOMI patients peaked at the day of diagnosis.

CONCLUSION

NOMI is a rare but life-threatening and potentially curable complication following successful cardiopulmonary resuscitation. Lactate and base deficit at admission could help to identify patients at risk for developing NOMI who might benefit from increased clinical attention.

Investigational vasopressin receptor modulators in the pipeline

The vasopressin system is complex and interacts with the central nervous, cardiovascular, renal, and hematological systems. Vasopressin plays an important role in the control of blood osmolarity and vascular tone, but is also involved in many other physiological events, which are mediated mainly via three types of vasopressin receptor: V1R, V2R, and V3R. V1R primarily mediate the vascular, and V2R the aquaretic, effects of vasopressin. Vasopressin may also interact with other receptors, like adrenergic and angiotensin-II receptors, or with distinct biological pathways, including those of nitric oxide and the K(ATP) channel. There are numerous clinical situations where vasopressin receptor modulators (agonists or antagonists) could be used. Currently, vasopressin and terlipressin are most commonly used to stimulate V1R in vasodilatory shock and cardiac arrest, while desmopressin, a synthetic analogue of vasopressin, acts on V2R; but new molecules are becoming available in the treatment of inappropriate antidiuretic hormone (ADH) secretion.

Role of arginine vasopressin in the setting of cardiopulmonary resuscitation

Arginine vasopressin (AVP) constitutes an integral part of the neuroendocrine stress response during cardiac arrest. A strong correlation between endogenous AVP secretion and outcome from cardiac arrest has led to a number of experimental studies indicating a survival benefit of AVP compared to epinephrine. In the clinical setting, however, things are less clear. Although current data suggest that both epinephrine and AVP are equally effective to restore spontaneous circulation in out-of-hospital cardiac arrest, benefits of AVP in specific patient groups, e.g. those with asystolic cardiac arrest, have been shown. The latest international guidelines recommend AVP as an alternative vasopressor drug which may replace the first or second dosage of epinephrine in the treatment of pulseless arrest If the combined use of AVP and epinephrine is superior to epinephrine alone in terms of improved hospital admission and discharge rates this needs to be re-confirmed by the results of an ongoing multicenter trial.

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.

Cerebral metabolism assessed with microdialysis in uncontrolled hemorrhagic shock after penetrating liver trauma

In a porcine model of uncontrolled hemorrhagic shock, we evaluated the effects of fluid resuscitation versus arginine vasopressin (AVP) combined with hypertonic-hyperoncotic hydroxyethyl starch solution (HHS) on cerebral perfusion pressure (CPP) and on cerebral metabolism using intracerebral microdialysis. Sixteen anesthetized pigs were subjected to uncontrolled liver bleeding until hemodynamic decompensation, followed by resuscitation using either fluid (n = 8) or AVP/HHS (n = 8). Thirty minutes after drug administration, bleeding was controlled by manual compression, and colloid and crystalloid solutions were administered in both groups. All surviving animals were observed for one hour. After hemodynamic decompensation, fluid resuscitation resulted in a smaller increase of CPP than did AVP/HHS (mean +/- sem; 24 +/- 5 vs 45 +/- 7 mm Hg; P < 0.01). Mean (+/- sem) cerebral venous partial pressure of oxygen was significantly decreased (P < 0.01) 5 min after fluid compared with 5 min after AVP/HHS administration (36 +/- 3 vs 64 +/- 4 torr). Cerebral metabolism was comparable in both groups. In conclusion, AVP/HHS proved to be superior to fluid in the initial phase of therapy with respect to CPP and cerebral oxygenation, but was comparable to fluid regarding cerebral metabolism and secondary cell damage in surviving animals.

Vasopressin during cardiopulmonary resuscitation and different shock states: a review of the literature

Vasopressin administration may be a promising therapy in the management of various shock states. In laboratory models of cardiac arrest, vasopressin improved vital organ blood flow, cerebral oxygen delivery, the rate of return of spontaneous circulation, and neurological recovery compared with epinephrine (adrenaline). In a study of 1219 adult patients with cardiac arrest, the effects of vasopressin were similar to those of epinephrine in the management of ventricular fibrillation and pulseless electrical activity; however, vasopressin was superior to epinephrine in patients with asystole. Furthermore, vasopressin followed by epinephrine resulted in significantly higher rates of survival to hospital admission and hospital discharge. The current cardiopulmonary resuscitation guidelines recommend intravenous vasopressin 40 IU or epinephrine 1mg in adult patients refractory to electrical countershock. Several investigations have demonstrated that vasopressin can successfully stabilize hemodynamic variables in advanced vasodilatory shock. Use of vasopressin in vasodilatory shock should be guided by strict hemodynamic indications, such as hypotension despite norepinephrine (noradrenaline) dosages >0.5 mug/kg/min. Vasopressin must never be used as the sole vasopressor agent. In our institutional routine, a fixed vasopressin dosage of 0.067 IU/min (i.e. 100 IU/50 mL at 2 mL/h) is administered and mean arterial pressure is regulated by adjusting norepinephrine infusion. When norepinephrine dosages decrease to 0.2 microg/kg/min, vasopressin is withdrawn in small steps according to the response in mean arterial pressure. Vasopressin also improved short- and long-term survival in various porcine models of uncontrolled hemorrhagic shock. In the clinical setting, we observed positive effects of vasopressin in some patients with life-threatening hemorrhagic shock, which had no longer responded to adrenergic catecholamines and fluid resuscitation. Clinical employment of vasopressin during hemorrhagic shock is experimental at this point in time.

Effects of vasopressin, norepinephrine, and l-arginine on intestinal microcirculation in endotoxemia*

OBJECTIVE

The effects of vasopressin, norepinephrine, and L-arginine alone or combined on intestinal microcirculation were evaluated in the septic mouse by intravital microscopy, with which we measured the erythrocyte flux and velocity in villus tip arterioles and the density of perfused villi.

DESIGN

Controlled animal study.

SETTING

University research laboratory.

SUBJECTS

Female BALB/c mice weighing between 18 and 21 g.

INTERVENTIONS

Anesthetized and ventilated mice received at t0 an intravenous injection of Escherichia coli endotoxin (2 mg/kg bolus intravenously), inducing after 1 hr (t60) a decrease in mean arterial blood pressure to 40-50 mm Hg associated with a significant decrease in erythrocyte flux and velocity in villus tip arterioles and in the density of perfused villi. The mice then received a randomly different treatment for endotoxin-induced shock. Treatments consisted in continuous intravenous infusion for 1 hr with either saline (control group), norepinephrine, vasopressin, L-arginine, vasopressin+L-arginine, or norepinephrine+L-arginine. The doses of vasopressors (used alone or combined with L-arginine) were titrated to restore mean arterial pressure to the baseline level.

MEASUREMENTS AND MAIN RESULTS

At the end of the treatment (t120), we observed in the control group further decreases in arteriolar flux and velocity and in the density of perfused villi. In the groups treated by a vasopressor alone, mean arterial pressure returned to baseline and there were no additional decreases in arteriolar flux and velocity or in the density of perfused villi. However, these latter three variables did not return to their preshock baseline values. Even though L-arginine did not restore mean arterial pressure, the infusion of L-arginine alone prevented the decrease in flux or erythrocyte velocity occurring between t60 and t120 and conserved to some extent the density of perfused villi compared with that in the control groups. In addition, we found that simultaneous administration of norepinephrine or vasopressin with L-arginine improved all microcirculation variables more efficiently than either vasopressor alone.

CONCLUSIONS

From these data, we conclude that a) restoring mean arterial pressure after 1 hr of endotoxemia was not sufficient to restore ad integrum intestinal mucosa microvascular perfusion; b) L-arginine could have a beneficial effect at the microcirculatory level, which was independent of mean arterial pressure; and c) administration of L-arginine combined with the maintenance of perfusion pressure by vasopressive drugs allowed a better preservation of intestinal microcirculation at an early stage of endotoxemia.

The International Liaison Committee on Resuscitation (ILCOR) consensus on science with treatment recommendations for pediatric and neonatal patients: pediatric basic and advanced life support

This publication contains the pediatric and neonatal sections of the 2005 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations (COSTR). The consensus process that produced this document was sponsored by the International Liaison Committee on Resuscitation (ILCOR). ILCOR was formed in 1993 and consists of representatives of resuscitation councils from all over the world. Its mission is to identify and review international science and knowledge relevant to cardiopulmonary resuscitation (CPR) and emergency cardiovascular care (ECC) and to generate consensus on treatment recommendations. ECC includes all responses necessary to treat life-threatening cardiovascular and respiratory events. The COSTR document presents international consensus statements on the science of resuscitation. ILCOR member organizations are each publishing resuscitation guidelines that are consistent with the science in this consensus document, but they also take into consideration geographic, economic, and system differences in practice and the regional availability of medical devices and drugs. The American Heart Association (AHA) pediatric and the American Academy of Pediatrics/AHA neonatal sections of the resuscitation guidelines are reprinted in this issue of Pediatrics (see pages e978-e988). The 2005 evidence evaluation process began shortly after publication of the 2000 International Guidelines for CPR and ECC. The process included topic identification, expert topic review, discussion and debate at 6 international meetings, further review, and debate within ILCOR member organizations and ultimate approval by the member organizations, an Editorial Board, and peer reviewers. The complete COSTR document was published simultaneously in Circulation (International Liaison Committee on Resuscitation. 2005 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations. Circulation. 2005;112(suppl):73-90) and Resuscitation (International Liaison Committee on Resuscitation. 2005 International Consensus Conference on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations. Resuscitation. 2005;67:271-291). Readers are encouraged to review the 2005 COSTR document in its entirety. It can be accessed through the CPR and ECC link at the AHA Web site: www.americanheart.org. The complete publication represents the largest evaluation of resuscitation literature ever published and contains electronic links to more detailed information about the international collaborative process. To organize the evidence evaluation, ILCOR representatives established 6 task forces: basic life support, advanced life support, acute coronary syndromes, pediatric life support, neonatal life support, and an interdisciplinary task force to consider overlapping topics such as educational issues. The AHA established additional task forces on stroke and, in collaboration with the American Red Cross, a task force on first aid. Each task force identified topics requiring evaluation and appointed international experts to review them. A detailed worksheet template was created to help the experts document their literature review, evaluate studies, determine levels of evidence, develop treatment recommendations, and disclose conflicts of interest. Two evidence evaluation experts reviewed all worksheets and assisted the worksheet reviewers to ensure that the worksheets met a consistently high standard. A total of 281 experts completed 403 worksheets on 275 topics, reviewing more than 22000 published studies. In December 2004 the evidence review and summary portions of the evidence evaluation worksheets, with worksheet author conflict of interest statements, were posted on the Internet at www.C2005.org, where readers can continue to access them. Journal advertisements and e-mails invited public comment. Two hundred forty-nine worksheet authors (141 from the United States and 108 from 17 other countries) and additional invited experts and reviewers attended the 2005 International Consensus Conference for presentation, discussion, and debate of the evidence. All 380 participants at the conference received electronic copies of the worksheets. Internet access was available to all conference participants during the conference to facilitate real-time verification of the literature. Expert reviewers presented topics in plenary, concurrent, and poster conference sessions with strict adherence to a novel and rigorous conflict of interest process. Presenters and participants then debated the evidence, conclusions, and draft summary statements. Wording of science statements and treatment recommendations was refined after further review by ILCOR member organizations and the international editorial board. This format ensured that the final document represented a truly international consensus process. The COSTR manuscript was ultimately approved by all ILCOR member organizations and by an international editorial board. The AHA Science Advisory and Coordinating Committee and the editor of Circulation obtained peer reviews of this document before it was accepted for publication. The most important changes in recommendations for pediatric resuscitation since the last ILCOR review in 2000 include: Increased emphasis on performing high quality CPR: "Push hard, push fast, minimize interruptions of chest compression; allow full chest recoil, and don't provide excessive ventilation" Recommended chest compression-ventilation ratio: For lone rescuers with victims of all ages: 30:2 For health care providers performing 2-rescuer CPR for infants and children: 15:2 (except 3:1 for neonates) Either a 2- or 1-hand technique is acceptable for chest compressions in children Use of 1 shock followed by immediate CPR is recommended for each defibrillation attempt, instead of 3 stacked shocks Biphasic shocks with an automated external defibrillator (AED) are acceptable for children 1 year of age. Attenuated shocks using child cables or activation of a key or switch are recommended in children <8 years old. Routine use of high-dose intravenous (IV) epinephrine is no longer recommended. Intravascular (IV and intraosseous) route of drug administration is preferred to the endotracheal route. Cuffed endotracheal tubes can be used in infants and children provided correct tube size and cuff inflation pressure are used. Exhaled CO2 detection is recommended for confirmation of endotracheal tube placement. Consider induced hypothermia for 12 to 24 hours in patients who remain comatose following resuscitation. Some of the most important changes in recommendations for neonatal resuscitation since the last ILCOR review in 2000 include less emphasis on using 100% oxygen when initiating resuscitation, de-emphasis of the need for routine intrapartum oropharyngeal and nasopharyngeal suctioning for infants born to mothers with meconium staining of amniotic fluid, proven value of occlusive wrapping of very low birth weight infants <28 weeks' gestation to reduce heat loss, preference for the IV versus the endotracheal route for epinephrine, and an increased emphasis on parental autonomy at the threshold of viability. The scientific evidence supporting these recommendations is summarized in the neonatal document (see pages e978-e988).

24-hour pretreatment with delta opioid enhances survival from hemorrhagic shock

OBJECTIVES

Delta opioids have been shown to confer ischemic preconditioning and pharmacologic ischemic preconditioning to the myocardium. However, their role in providing extended pharmacologic ischemic preconditioning in hemorrhagic shock has not been explored. The authors examined the effects of 24-hour preinfusions of a selective delta opioid receptor agonist, Deltorphin-Dvariant (Delt-Dvar), on hemodynamic stability and duration of survival in a rat model of severe hemorrhagic shock.

METHODS

Conscious Sprague-Dawley rats with indwelling catheters were hemorrhaged at a rate of 3.18 mL/l00 g over 20 minutes. Twenty-four hours before hemorrhage, the control group (n = 14) was infused with 1.0 mL lactated Ringer's solution, and the Delt-Dvar-treated group (n = 22) was infused with 5.0 mg/kg Delt-Dvar in 1.0 mL lactated Ringer's solution. Rats were continuously monitored for heart rate (HR), mean arterial pressure, and four-hour survival rates. Plasma lactate levels were determined at the beginning of hemorrhage and the end of hemorrhage.

RESULTS

At 240 minutes, only one of 14 controls (7.1%) survived, while 16 (72.7%) of the 22 experimental rats survived. No significant differences in heart rate between controls and Delt-Dvar-treated rats were noted. Increases in mean arterial pressure of Delt-Dvar-treated rats at the beginning of hemorrhage and at the end of hemorrhage were found to be significant (p < 0.05). At 240 minutes, heart rate and mean arterial pressure were not different between the single surviving control and the Delt-Dvar group. At the end of hemorrhage, lactate levels in the Delt-Dvar-treated group were 8.5 (+/- 0.5) mmol/L versus 10.8 (+/- 0.6) mmol/L (p < 0.05) in the control group.

CONCLUSIONS

Twenty-four-hour pretreatment with Delt-Dvar decreases plasma lactate levels and improves hemodynamic stability and survival during hemorrhagic shock. The use of delta-specific opioids may improve survival from hemorrhagic shock and have clinical utility in providing ischemic protection in scenarios of planned ischemia.

Influence of dobutamine on the variables of systemic haemodynamics, metabolism, and intestinal perfusion after cardiopulmonary resuscitation in the rat

BACKGROUND

Global left ventricular dysfunction after successful resuscitation from cardiac arrest may be treated successfully with dobutamine but the effects on intestinal perfusion are unknown.

METHODS

In 24 male Sprague-Dawley rats ventricular fibrillation was induced. After 4 min of untreated cardiac arrest, precordial chest compression was performed for 4 min; adrenaline (epinephrine) (90 microg kg(-1)) was injected, followed by defibrillation. Return of spontaneous circulation was achieved in 18 animals, which were allocated to receive saline 0.9% (control group, n = 6), dobutamine at 5 microg kg(-1) min(-1) (n = 6) or dobutamine at 10 microg kg(-1) min(-1) (n = 6). Measurements of haemodynamic variables and intestinal tonometer P(CO2) were made before induction of ventricular fibrillation and 15, 30, 60, and 120 min postresuscitation.

RESULTS

At 120 min postresuscitation, mean aortic pressure was 82 +/- 20, 104 +/- 19, and 113 +/- 15 mmHg for the control group, the dobutamine (5 microg kg(-1) min(-1)) group and the dobutamine (10 microg kg(-1) min(-1)) group (P < 0.05 for comparison of the dobutamine (10 microg kg(-1) min(-1)) group versus the control group). Respective abdominal aortic blood flow was 107 +/- 16, 133 +/- 49, and 145 +/- 18 ml min(-1) kg(-1) (P < 0.05 for comparison of the dobutamine (10 microg kg(-1) min(-1)) group versus the control group), and superior mesenteric artery blood flow was 25 +/- 9, 28 +/- 8, and 33 +/- 8 ml min(-1) kg(-1). Arterial lactate was significantly higher (P < 0.05) in the control group (2.3 +/- 0.6 mmol l(-1)) than in the dobutamine (5 microg kg(-1) min(-1)) group (1.6 +/- 0.3 mmol l(-1)) and dobutamine (10 microg kg(-1) min(-1)) group (1.5 +/- 0.3 mmol l(-1)). Tonometrically derived P(CO2) gap was highly elevated at 15 min of postresuscitation and returned to prearrest level at 120 min postresuscitation in all groups.

CONCLUSIONS

Dobutamine enhances the recovery of global haemodynamic and metabolic variables early after cardiac arrest.

Pneumatosis intestinalis and hepatic portal venous gas after CPR

Pneumatosis intestinalis and hepatic portal venous gas are usually associated with severe intra-abdominal pathologies. As diagnostic technologies advanced, a number of variant etiologies have been identified. We report 2 cases in which pneumatosis intestinalis and hepatic portal venous gas developed after prolonged cardiopulmonary resuscitation (CPR). The pathogenic mechanism was most probably bowel infarction caused by poor mesenteric perfusion during and after CPR. Limited cardiac output during prolonged resuscitation and severe vasoconstriction after large doses of epinephrine and vasopressors might both contribute to the compromised mesenteric perfusion. The risk seems especially high for old patients with severe atherosclerosis. Once it happens, the prognosis is extremely poor. In patients of cardiac arrests receiving prolonged CPR, catastrophic complications like this should be considered in the postresuscitation phase, especially those with multiple risk factors like old age, severe atherosclerosis, and use of large doses of vasoconstrictors.

Vasopressin during cardiopulmonary resuscitation: A progress report

OBJECTIVE

In patients undergoing cardiopulmonary resuscitation, circulating endogenous vasopressin concentrations were significantly higher in successfully resuscitated patients than in patients who died. These observations have prompted several investigations to assess the role of vasopressin to improve cardiopulmonary resuscitation management.

DESIGN

Literature review.

RESULTS

In the cardiopulmonary resuscitation laboratory, vasopressin improved vital organ blood flow, cerebral oxygen delivery, the probability of restoring spontaneous circulation, and neurologic recovery better than epinephrine. In pediatric preparations with asphyxia, epinephrine was superior to vasopressin, whereas in both pediatric pigs with ventricular fibrillation and adult porcine models with asphyxia, combinations of vasopressin and epinephrine proved to be highly effective. In addition, vasopressin enabled short- and long-term survival in a porcine model of uncontrolled hemorrhagic shock. In a recently published European, multiple-center trial, 1,219 adult patients with out-of-hospital cardiac arrest were randomized to receive two injections of either 40 IU of vasopressin or 1 mg of epinephrine followed by additional epinephrine if needed. The clinical study did not confirm laboratory data showing vasopressin to be more effective than epinephrine in ventricular fibrillation and pulseless electrical activity, but vasopressin was superior to epinephrine in patients with asystole. Vasopressin followed by epinephrine was more effective than epinephrine alone in the treatment of refractory cardiac arrest.

CONCLUSIONS

According to new data from the European vasopressin study, we suggest, first, the administration of 1 mg of epinephrine, followed alternately by 40 IU of vasopressin and 1 mg of epinephrine every 3 mins in adult cardiac arrest victims, regardless of the initial electrocardiographic rhythm.

Treatment of uncontrolled hemorrhagic shock after liver trauma: fatal effects of fluid resuscitation versus improved outcome after vasopressin

In a porcine model of uncontrolled hemorrhagic shock, we evaluated the effects of vasopressin versus an equal volume of saline placebo versus fluid resuscitation on hemodynamic variables and short-term survival. Twenty-one anesthetized pigs were subjected to severe liver injury. When mean arterial blood pressure was <20 mm Hg and heart rate decreased, pigs randomly received either vasopressin IV (0.4 U/kg; n = 7), an equal volume of saline placebo (n = 7), or fluid resuscitation (1000 mL each of lactated Ringer's solution and hetastarch; n = 7). Thirty minutes after intervention, surviving pigs were fluid resuscitated while bleeding was surgically controlled. Mean (+/- SEM) arterial blood pressure 5 min after the intervention was significantly (P < 0.05) higher after vasopressin than with saline placebo or fluid resuscitation (58 +/- 9 versus 7 +/- 3 versus 32 +/- 6 mm Hg, respectively). Vasopressin improved abdominal organ blood flow but did not cause further blood loss (vasopressin versus saline placebo versus fluid resuscitation 10 min after intervention, 1343 +/- 60 versus 1350 +/- 22 versus 2536 +/- 93 mL, respectively; P < 0.01). Seven of 7 vasopressin pigs survived until bleeding was controlled and 60 min thereafter, whereas 7 of 7 saline placebo and 7 of 7 fluid resuscitation pigs died (P < 0.01). We conclude that vasopressin, but not saline placebo or fluid resuscitation, significantly improves short-term survival during uncontrolled hemorrhagic shock.

IMPLICATIONS

Although IV fluid administration is the mainstay of nonsurgical management of trauma patients with uncontrolled hemorrhagic shock, the efficacy of this strategy has been discussed controversially. In this animal model of severe liver trauma with uncontrolled hemorrhagic shock, vasopressin, but not saline placebo or fluid resuscitation, improved short-term survival.

Vasoactive drugs and the kidney

Protection of renal function and prevention of acute renal failure (ARF) are important goals of resuscitation in critically ill patients. Beyond fluid resuscitation and avoidance of nephrotoxins, little is known about how such prevention can be achieved. Vasoactive drugs are often administered to improve either cardiac output or mean arterial pressure in the hope that renal blood flow will also be improved and, thereby, renal protection achieved. Some of these drugs (especially low-dose dopamine) have even been proposed to have a specific beneficial effect on renal blood flow. However, when all studies dealing with vasoactive drugs and their effects on the kidney are reviewed, it is clear that none have been demonstrated to achieve clinically important benefits in terms of renal protection. It is also clear that, with the exception of low-dose dopamine, there have been no randomized controlled trials of sufficient statistical power to detect differences in clinically meaningful outcomes. In the absence of such data, all that is available is based on limited physiological gains (changes in renal blood flow or urine output) with one or another drug in one or another subpopulation of patients. Furthermore, given our lack of understanding of the pathogenesis of ARF, it is unclear whether haemodynamic manipulation is an appropriate avenue to achieve renal protection. There is a great need for large randomized controlled trials to test the clinical, instead of physiological, effects of vasoactive drugs in critical illness.

High-dose vasopressin is not superior to norepinephrine in septic shock*

OBJECTIVE

We examined the effects of arginine vasopressin, when substituted for norepinephrine as a vasopressor in septic shock, on global and hepatosplanchnic hemodynamic and oxygen transport variables.

DESIGN

Experimental study.

SETTING

Intensive care unit.

SUBJECTS

Twelve septic shock patients.

INTERVENTIONS

Norepinephrine was replaced by vasopressin in a dose sufficient to keep mean arterial blood pressure constant. Blood flow, oxygen delivery, and oxygen consumption of the hepatosplanchnic region (calculated by a hepatic venous catheter technique using the Fick principle during continuous infusion of indocyanine green), global hemodynamics (by thermodilution), and gastric regional PCO2 gap (by air tonometry) were calculated during infusion of norepinephrine (mean, 0.56 microg.kg-1.min-1; range, 0.18-1.1 microg.kg-1.min-1) and again 2 hrs after replacement by vasopressin (mean, 0.47 IU/min; range, 0.06-1.8 IU/min).

MEASUREMENTS AND MAIN RESULTS

Cardiac index decreased significantly from 3.8 +/- 1.3 to 3.0 +/- 1.1 L.min-1.m-2, heart rate decreased from 96 +/- 14 to 80 +/- 16 min-1 (p <.01), and global oxygen uptake decreased from 248 +/- 67 to 218 +/- 75 mL/min (p <.05). Absolute splanchnic blood flow tended to increase, although not significantly, whereas fractional splanchnic blood flow increased from 10.8 +/- 7.6 to 25.9 +/- 16.6% of cardiac output (p <.05). Gastric regional PCO2 gap increased from 17.5 +/- 26.6 to 36.5 +/- 26.6 mm Hg (p <.01).

CONCLUSION

Vasopressin, in doses sufficient to replace the vasopressor norepinephrine, had mixed effects in septic shock patients. Hepatosplanchnic blood flow was preserved during substantial reduction in cardiac output. An increased gastric PCO2 gap suggests that the gut blood flow could have been redistributed to the disadvantage of the mucosa. Based on these limited data, it does not appear beneficial to directly replace norepinephrine with vasopressin in septic shock.

Is vasopressin superior to adrenaline or placebo in the management of cardiac arrest? A meta-analysis

Vasopressin is currently recommended in the management of patients with cardiac arrest, but its efficacy is still incompletely established. We systematically reviewed randomized trials comparing vasopressin to control treatment in the management of cardiac arrest in humans and animals. Two human and 33 animal studies were retrieved. At pooled analysis vasopressin appeared equivalent to adrenaline (epinephrine) in the management of human cardiac arrest (N=240), with, respectively 63 (78/124) vs 59% (68/116) ROSC (P=0.43), and 16 (20/124) vs 14% (16/116) survival to hospital discharge (P=0.52). In animal trials (N=669) vasopressin appeared instead significantly superior to both placebo (ROSC, respectively 93 [98/105] vs 19% [14/72], P<0.001) or adrenaline (ROSC, respectively 84 [225/268] vs 52% [117/224], P<0.001). In conclusion, vasopressin is superior to both placebo or adrenaline in animal models of cardiopulmonary resuscitation. Evidence in humans is still limited and confidence intervals estimates too wide to reliably confirm or disprove results obtained in experimental animal settings.

Pediatric cardiopulmonary-cerebral resuscitation: an overview and future directions

The evolving understanding of pathophysiologic events during and after pediatric cardiac arrest has not yet resulted in significantly improved outcome. Exciting breakthroughs in basic and applied science laboratories are, however, on the immediate horizon for study in specific subpopulations of cardiac arrest victims. Strategically focusing therapies to specific phases of cardiac arrest and resuscitation and evolving pathophysiologic events offers great promise that critical care interventions will lead the way to more successful cardiopulmonary and cerebral resuscitation in children.

Management of vasodilatory shock: defining the role of arginine vasopressin

The rationale for an arginine vasopressin (argipressin) infusion was put forward after it was discovered that patients in shock states might have an endogenous arginine vasopressin deficiency. Subsequently, several investigations impressively demonstrated that arginine vasopressin can successfully stabilise haemodynamics even in advanced vasodilatory shock. We report on physiological and pharmacological aspects of arginine vasopressin, and summarise current clinical knowledge on employing a continuous arginine vasopressin infusion in critically ill patients with catecholamine-resistant vasodilatory shock of different aetiologies. In view of presented experimental evidence and current clinical experience, a continuous arginine vasopressin infusion of approximately 2 to approximately 6 IU/h can be considered as a supplemental strategy to vasopressor catecholamines in order to preserve cardiocirculatory homeostasis in patients with advanced vasodilatory shock. Because data on adverse effects are still limited, arginine vasopressin should be reserved for patients in whom adequate haemodynamic stabilisation cannot be achieved with conventional vasopressor therapy or who have obvious adverse effects of catecholamines that result in further significant haemodynamic deterioration. For the same reasons, arginine vasopressin should not be used as a single, alternative vasopressor agent instead of catecholamine vasopressors. Future prospective studies will be necessary to define the exact role of arginine vasopressin in the therapy of vasodilatory shock.

Arginine vasopressin, but not epinephrine, improves survival in uncontrolled hemorrhagic shock after liver trauma in pigs

OBJECTIVE

Epinephrine is widely used for treatment of life-threatening hypotension, although new vasopressor drugs may merit evaluation. The purpose of this study was to determine the effects of vasopressin vs. epinephrine vs. saline placebo on hemodynamic variables, regional blood flow, and short-term survival in an animal model of uncontrolled hemorrhagic shock and delayed fluid resuscitation.

DESIGN

Prospective, randomized, laboratory investigation that used a porcine model for measurement of hemodynamic variables and regional abdominal organ blood flow.

SETTING

University hospital laboratory.

SUBJECTS

A total of 21 pigs weighing 32 +/- 3 kg.

INTERVENTIONS

The anesthetized pigs were subjected to a penetrating liver injury, which resulted in a mean +/- sem loss of 40% +/- 5% of estimated whole blood volume within 30 mins and mean arterial pressures of <20 mm Hg. When heart rate declined progressively, pigs randomly received a bolus dose and continuous infusion of either vasopressin (0.4 units/kg and 0.04 units.kg-1.min-1, n = 7), or epinephrine (45 microg/kg and 5 microg.kg(-1).min(-1), n = 7), or an equal volume of saline placebo (n = 7), respectively. At 30 mins after drug administration, all surviving animals were fluid resuscitated while bleeding was surgically controlled.

MEASUREMENTS AND MAIN RESULTS

Mean +/- sem arterial blood pressure at 2.5 and 10 mins was significantly (p <.001) higher after vasopressin vs. epinephrine vs. saline placebo (82 +/- 14 vs. 23 +/- 4 vs. 11 +/- 3 mm Hg, and 42 +/- 4 vs. 10 +/- 5 vs. 6 +/- 3 mm Hg, respectively). Although portal vein blood flow was temporarily impaired by vasopressin, it was subsequently restored and significantly (p <.01) higher when compared with epinephrine or saline placebo (9 +/- 5 vs. 121 +/- 3 vs. 54 +/- 22 mL/min and 150 +/- 20 vs. 31 +/- 17 vs. 0 +/- 0 mL/min, respectively). Hepatic and renal artery blood flow was significantly higher throughout the study in the vasopressin group; however, no further bleeding was observed. Despite a second bolus dose, all epinephrine- and saline placebo-treated animals died within 15 mins after drug administration. By contrast, seven of seven vasopressin-treated animals survived until fluid replacement, and 60 mins thereafter, without further vasopressor therapy (p <.01). Moreover, blood flow to liver, gut, and kidney returned to normal values in the postshock phase.

CONCLUSIONS

Vasopressin, but not epinephrine or saline placebo, improved short-term survival in a porcine model of uncontrolled hemorrhagic shock after liver injury when surgical intervention and fluid replacement was delayed.

Should vasopressin replace adrenaline for endotracheal drug administration?

OBJECTIVE

Arginine vasopressin was established recently as a drug of choice in the treatment of cardiac arrest and in retractable ventricular fibrillation; however, the hemodynamic effect of vasopressin following endotracheal drug administration has not been fully elucidated. We compared the effects of endotracheally administered vasopressin vs. adrenaline on hemodynamic variables in a canine model, and we investigated whether vasopressin produces the same deleterious immediate blood pressure decrease as did endotracheal adrenaline in the canine model.

DESIGN

Prospective controlled study.

SETTING

Animal laboratory in Tel-Aviv University, Israel.

SUBJECTS

Five adult mongrel dogs weighing 6.5-20 kg.

INTERVENTIONS

Dogs were anesthetized; each dog was intubated orally, and both femoral arteries were cannulated for the measurement of arterial pressure and for sampling blood gases. Each dog was studied four times, 1 wk apart, by using the same protocol for injection and anesthesia: endotracheal placebo (10 mL NaCl 0.9%,), endotracheal vasopressin (1 units/kg), endobronchial adrenaline (0.1 mg/kg), and endotracheal adrenaline (0.1 mg/kg). Following placebo, vasopressin, and adrenaline instillation, five forced manual ventilations were delivered with an Ambu bag. Each dog was its own control.

MEASUREMENTS AND MAIN RESULTS

Following placebo or drug administration, heart electrocardiography and arterial pressures were continuously monitored with a polygraph recorder for 1 hr. Endotracheal vasopressin produced an immediate increase of diastolic blood pressure (from 83 +/- 10 mm Hg [baseline] to 110 +/- 5 mm Hg at 1 min postinjection). This response lasted >1 hr. In contrast, both endotracheal and endobronchial administration of adrenaline produced an early and significant (p <.05) decrease in diastolic and mean blood pressures. The diastolic blood pressure increase from 85 +/- 10 mm Hg to 110 +/- 10 mm Hg took an ill-afforded 55 secs following endotracheal adrenaline. Diastolic blood pressure was significantly (p <.05) higher following vasopressin compared with adrenaline administration in both routes.

CONCLUSIONS

Vasopressin accomplishes its hemodynamic effect, particularly on diastolic blood pressure, more rapidly, vigorously, and protractedly and to a significant degree compared with both endotracheal and endobronchial adrenaline. Evaluation of the effects of endotracheal vasopressin in a closed chest cardiopulmonary resuscitation model is recommended.

Vasopressor response in a porcine model of hypothermic cardiac arrest is improved with active compression-decompression cardiopulmonary resuscitation using the inspiratory impedance threshold valve

During normothermic cardiac arrest, a combination of active compression-decompression (ACD) cardiopulmonary resuscitation (CPR) with the inspiratory threshold valve (ITV) significantly improves vital organ blood flow, but this technique has not been studied during hypothermic cardiac arrest. Accordingly, we evaluated the hemodynamic effects of ACD + ITV CPR before, and after, the administration of vasopressin in a porcine model of hypothermic cardiac arrest. Pigs were surface-cooled until their body core temperature was 26 degrees C. After 10 min of untreated ventricular fibrillation, 14 animals were randomly assigned to either ACD CPR with the ITV (n = 7) or to standard (STD) CPR (n = 7). After 8 min of CPR, all animals received 0.4 U/kg vasopressin IV, and CPR was maintained for an additional 10 min in each group; defibrillation was attempted after 28 min of cardiac arrest, including 18 min of CPR. Before the administration of vasopressin, mean +/- SEM common carotid blood flow was significantly higher in the ACD + ITV group compared with STD CPR (67 +/- 13 versus 26 +/- 5 mL/min, respectively; P < 0.025). After vasopressin was given at minute 8 during CPR, mean +/- SEM coronary perfusion pressure was significantly higher in the ACD + ITV group, but did not increase in the STD group (29 +/- 3 versus 15 +/- 2 mm Hg, and 25 +/- 1 versus 14 +/- 1 mm Hg at minute 12 and 18, respectively; P < 0.001); mean +/- SEM common carotid blood flow remained higher at respective time points (33 +/- 8 versus 10 +/- 3 mL/min, and 31 +/- 7 versus 7 +/- 3 mL/min, respectively; P < 0.01). Without active rewarming, spontaneous circulation was restored and maintained for 1 h in three of seven animals in the ACD + ITV group versus none of seven animals in the STD CPR group (not significant). During hypothermic cardiac arrest, ACD CPR with the ITV improved common carotid blood flow compared with STD CPR alone. Moreover, after the administration of vasopressin, coronary perfusion pressure was significantly higher during ACD + ITV CPR, but not during STD CPR.

IMPLICATIONS

New strategies are needed to improve the efficiency of cardiopulmonary resuscitation (CPR) in hypothermic cardiac arrest. Active compression-decompression CPR with the inspiratory threshold valve improved carotid blood flow (and coronary perfusion pressure with vasopressin) compared with standard CPR.

Vasopressin: new uses in critical care

The science of medicine has evolved dramatically over recent years, with better understanding of the mechanisms of disease leading to innovative new treatments. However, the critical care patient still suffers from a high mortality rate with few advances from the traditional modalities of therapy. Arginine vasopressin has been explored as a vasoconstrictor in the treatment of the hypotension associated with septic shock. This drug has also recently been added to the advanced cardiac life support protocol for the resuscitation of pulseless ventricular tachycardia and ventricular fibrillation. Studies of arginine vasopressin in these situations have been promising but still have yet to prove a survival benefit over traditional therapies. Newer and larger trials are necessary to determine whether any mortality benefit can be sustained from the use of arginine vasopressin in critical care patients with septic shock and cardiac arrest secondary to pulseless ventricular tachycardia and ventricular fibrillation.

Combination drug therapy with vasopressin, adrenaline (epinephrine) and nitroglycerin improves vital organ blood flow in a porcine model of ventricular fibrillation

There is increasing evidence that the combination of epinephrine (adrenaline) with vasopressin may be superior to either epinephrine or vasopressin alone for treatment of cardiac arrest. However, the optimal combination, and dosage of cardiovascular drugs to minimize side effects, and to improve outcome has yet to be found. We therefore evaluated whether the combination of vasopressin plus epinephrine plus nitroglycerin (EVN), would improve vital organ blood flow during cardiopulmonary resuscitation (CPR) when compared with epinephrine (EPI) alone. After 4 min of ventricular fibrillation (VF) and 4 min of standard CPR, pigs were randomized to the combination of epinephrine (45 microg/kg) plus vasopressin (0.4 U/kg) plus nitroglycerin (7.5 microg/kg; n=12), or epinephrine (40 microg/kg; n=12) alone. Cerebral and myocardial blood flow was measured with radiolabeled microspheres. Defibrillation was attempted after 19 min of VF including 15 min of CPR. Mean+/-SEM coronary perfusion pressures were significantly (P < 0.01) higher 5 min after EVN vs. EPI alone (34+/-3 vs. 24+/-3 mmHg, respectively). At the same time, mean+/-SEM left ventricular, and global cerebral blood flow was also significantly (P < 0.05) higher after EVN vs. EPI alone (0.78+/-0.11 vs. 0.48+/-0.08 ml/min/g; and 0.37+/-0.05 vs. 0.22+/-0.0 3 ml/min/g, respectively). Spontaneous circulation was restored in 11 of 12 animals in the EVN group vs. 6 of 12 swine after EPI alone (P = N.S.). In conclusion, the combination of EVN significantly improved vital organ blood flow during CPR compared with EPI alone. Addition of nitroglycerin to the combination of low dose epinephrine with vasopressin during cardiac arrest may be beneficial.

Advanced life support drugs: do they really work?

Basic life support and rapid defibrillation for ventricular fibrillation or pulseless ventricular tachycardia are the only two interventions that have been shown unequivocally to improve survival after cardiac arrest. Several drugs are advocated to treat cardiac arrest, but despite very encouraging animal data, no drug has been reliably proven to increase survival to hospital discharge after cardiac arrest. This review focuses on recent experimental and clinical data concerning the use of vasopressin, amiodarone, magnesium, and fibrinolytics during advanced life support (ALS). Animal data indicate that, in comparison with epinephrine (adrenaline), vasopressin produces better vital organ blood flow during cardiopulmonary resuscitation (CPR). These apparent advantages have yet to be converted into improved survival in large-scale trials of cardiac arrest in humans. Data from two prospective, randomized trials suggest that amiodarone may improve short-term survival after out-of-hospital ventricular fibrillation cardiac arrest. On the basis of anecdotal data, magnesium is recommended therapy for torsades de pointes and for shock-resistant ventricular fibrillation associated with hypomagnesemia. In the past, CPR has been a contraindication to giving fibrinolytics, but several studies have demonstrated the relative safety of fibrinolysis during and after CPR. Fibrinolytics are likely to be beneficial when cardiac arrest is associated with plaque rupture and fresh coronary thrombus or massive pulmonary embolism. Fibrinolysis may also improve cerebral microcirculatory perfusion once a spontaneous circulation has been restored. A planned, prospective, randomized trial may help to define the role of fibrinolysis during out-of-hospital CPR.

Resuscitation from cardiac arrest with adrenaline/epinephrine or vasopressin: effects on intestinal mucosal tonometer pCO(2) during the postresuscitation period in rats

BACKGROUND

The use of vasopressin instead of adrenaline/epinephrine during resuscitation improves vital organ perfusion, but the effects on mesenteric perfusion following successful resuscitation are not fully evaluated. The present study was designed to compare the effects of vasopressin and adrenaline/epinephrine, given to rats during resuscitation from ventricular fibrillation, on to mesenteric ischaemia, as determined by intestinal mucosal tonometer pCO(2) during the postresuscitation period.

METHODS AND RESULTS

Male Sprague-Dawley rats (n=28) were allocated randomly to receive vasopressin (0.8 U/kg) or adrenaline/epinephrine (90 microg/kg) after 5 min of ventricular fibrillation. Precordial chest compression was initiated 4 min after the start of ventricular fibrillation, continued for 4 min, and followed by defibrillation. Seven of 14 (vasopressin) and 12 of 14 (adrenaline/epinephrine) rats were successfully defibrillated (P=0.10, Fisher's exact test) and observed for 60 min. Intestinal mucosal tonometer pCO(2) measurements before cardiac arrest and 15, 30, and 60 min following return of spontaneous circulation were 47+/-3, 73+/-8, 63+/-7, and 56+/-6 mmHg in the vasopressin group and 48+/-5, 78+/-7, 67+/-6, and 62+/-6 mmHg in the adrenaline/epinephrine group (P<0.05 at 60 min between vasopressin and adrenaline/epinephrine). Right atrial hemoglobin oxygen saturations at these time points were 73+/-5, 51+/-12, 58+/-11, and 63+/-5% in the vasopressin group and 76+/-7, 44+/-10, 52+/-10 and 54+/-8% in the adrenaline/epinephrine group (P<0.05 at 60 min between vasopressin and adrenaline/epinephrine).

CONCLUSIONS

We conclude that in this rat model the administration of vasopressin instead of adrenaline/epinephrine for CPR tends to be associated with lower resuscitation success, but less mesenteric ischaemia during the postresuscitation period in successfully resuscitated rats.

Arginine vasopressin during cardiopulmonary resuscitation: laboratory evidence, clinical experience and recommendations, and a view to the future

When stimulating adult pigs with ventricular fibrillation or postcountershock pulseless electrical activity for cardiopulmonary resuscitation, vasopressin improved vital organ blood flow, cerebral oxygen delivery, ability to be resuscitated, and neurologic recovery better than epinephrine. In pediatric preparations with asphyxia, epinephrine was superior to vasopressin, whereas in both pediatric pigs with ventricular fibrillation and adult porcine models with asphyxia, combinations of vasopressin and epinephrine proved to be highly effective. This may suggest that a different efficiency of vasopressors in pediatric vs. adult preparations and different effects of dysrhythmic vs. asphyxial cardiac arrest on vasopressor efficiency may be of significant importance. Whether these theories can be extrapolated to humans is unknown at this time. In patients who experienced out-of-hospital ventricular fibrillation, a larger proportion of patients treated with vasopressin survived 24 hrs compared with patients treated with epinephrine; during in-hospital cardiopulmonary resuscitation, comparable short-term survival was found in groups treated with either vasopressin or epinephrine. Currently, a large trial comprising patients who experience out-of-hospital cardiac arrest and who are treated with vasopressin vs. epinephrine is ongoing in Germany, Austria, and Switzerland. The new cardiopulmonary resuscitation guidelines of both the American Heart Association and the European Resuscitation Council consider 40 units of vasopressin intravenously and 1 mg of epinephrine intravenously equally effective for the treatment of adult patients with ventricular fibrillation; however, because of a lack of clinical data, no recommendation for vasopressin has been made for adult patients with asystole and pulseless electrical activity or for pediatric patients.

Pressor drugs in the treatment of cardiac arrest

The importance of vital organ perfusion in patients suffering cardiac arrest makes arterial vasomotor tone, and the resultant perfusion pressure, critical in resuscitation from sudden death. Although there are multiple mechanisms that may affect arterial vascular tone, historically, the therapy most commonly used has been catecholamine-induced adrenergic receptor stimulation, with catecholamine epinephrine being the commonest drug used. Over the last decade, however, it has become widely known that the utility of epinephrine during cardiopulmonary resuscitation is undefined. This has led to research into alternative agents, in particular nonadrenergic vasoactive peptides. Other agents appear promising. This article addresses pressor drugs and adrenergic agonists, including a review of their history, basic science, mechanism of action, and efficacy. Epinephrine is reviewed.

Arginine vasopressin during cardiopulmonary resuscitation and vasodilatory shock: current experience and future perspectives

Epinephrine use during cardiopulmonary resuscitation (CPR) is controversial because of its receptor-mediated adverse effects such as increased myocardial oxygen consumption, ventricular arrhythmias, ventilation-perfusion defect, postresuscitation myocardial dysfunction, ventricular arrhythmias, and cardiac failure. In the CPR laboratory, vasopressin improved vital organ blood flow, cerebral oxygen delivery, resuscitability, and neurologic recovery more than did epinephrine. In patients with out-of-hospital ventricular fibrillation, a larger proportion of patients treated with vasopressin survived 24 hours than did patients treated with epinephrine. Currently, a large trial of out-of-hospital cardiac arrest patients being treated with vasopressin versus epinephrine is ongoing in Germany, Austria, and Switzerland. The new international CPR guidelines recommend 40 U vasopressin intravenously, and 1 mg epinephrine intravenously, as equally effective for the treatment of adult patients in ventricular fibrillation; however, no recommendation for vasopressin has been made to date for adult patients with asystole and pulseless electrical activity, or in children, because of lack of clinical data. When adrenergic vasopressors were unable to maintain arterial blood pressure in patients with vasodilatory shock, continuous infusions of vasopressin (0.04-0.10 U/min) stabilized cardiocirculatory parameters and even ensured weaning from catecholamines.

Innovative pharmacologic approaches to cardiopulmonary resuscitation

The survival rate of patients undergoing cardiopulmonary resuscitation is 5 to 15%. New cardiopulmonary resuscitation treatment approaches under investigation include the use of vasopressin as a vasopressor, amiodarone for the treatment of ventricular tachyarrhythmias, and adenosine antagonists (i.e., theophylline) for bradyasystolic rhythms. More innovative approaches include the use of thyroid hormone and endothelin.

Vasopressin and endothelin during cardiopulmonary resuscitation

Vital organ blood flow during cardiopulmonary resuscitation (CPR) and neurologic recovery after CPR were significantly better in pigs treated with vasopressin compared with epinephrine. Furthermore, two clinical studies evaluating both out-of-hospital and inhospital cardiac arrest patients found higher 24-hr survival rates in patients who were resuscitated with vasopressin compared with epinephrine. Scientists at the Leopold Franzens University in Innsbruck, Austria, are currently coordinating a multicenter, randomized clinical trial under the aegis of the European Resuscitation Council to study the effects of vasopressin vs. epinephrine in out-of-hospital cardiac arrest patients. Results of anticipated 1,500 enrolled patients may be available in 2001 and may help to determine the role of vasopressin during CPR. Another new, recently studied vasopressor for CPR is endothelin-1. To date, this vasopressor has only been studied as an intervention in animal CPR models, although plasma levels have been investigated in cardiac arrest patients. Initial reports found improved coronary perfusion pressure when combined with epinephrine. However, the CPR research group of the University of Arizona Sarver Heart Center found excessive vasoconstriction and worse survival than with epinephrine alone.

Excellent coronary perfusion pressure during cardiopulmonary resuscitation is not good enough to ensure long-term survival with good neurologic outcome: a porcine case report

PURPOSE

To report a case of cerebral ischemia confirmed by magnetic resonance imaging after successful cardiopulmonary resuscitation (CPR) complicated by acute respiratory injury.

MATERIALS AND METHODS

After 4 min of cardiac arrest, followed by 3 min of basic life support CPR, a female pig weighing 38 kg received every 5 min vasopressin (0.4, 0.4 and 0.8 U/kg). After 22 min of cardiac arrest, including 18 min of CPR, one defibrillation attempt employing 100 J resulted in return of spontaneous circulation. Neurological evaluation was performed 24 and 96 h after successful CPR. Magnetic resonance imaging was carried out 4 days after CPR using a clinical 1.5 T scanner. The magnetic resonance imaging protocol consisted of fast spinecho T2-weighted, as well as spinecho T1-weighted imaging of the brain.

RESULTS

CPR with vasopressin resulted in excellent coronary perfusion pressure ranging between 35 and 60 mm Hg throughout CPR. Eight minutes after initiation of chest compressions, bleeding out of the tracheal tube occurred. This was later confirmed as originating from bilateral bloody pulmonary infiltrations, resulting in acute respiratory injury in the post-resuscitation phase. Ninety-six hours after successful CPR, magnetic resonance imaging revealed bilateral diffuse cerebral vasogenic edema.

CONCLUSION

Although excellent coronary perfusion pressure renders a return of spontaneous circulation more likely, complications such as acute respiratory injury in the post-resuscitation phase have to be managed carefully in order to ensure good neurological recovery from cardiac arrest.

Vasopressin improves survival after cardiac arrest in hypovolemic shock

Survival after hypovolemic shock and cardiac arrest is dismal with current therapies. We evaluated the potential benefits of vasopressin versus large-dose epinephrine in hemorrhagic shock and cardiac arrest on vital organ perfusion, and the likelihood of resuscitation. In 18 pigs, 35% of the estimated blood volume was withdrawn over 15 min and ventricular fibrillation was induced 5 min later. After 4 min of cardiac arrest and 4 min of standard cardiopulmonary resuscitation, a bolus dose of either 200 microg/kg epinephrine (n = 7), 0.8 unit/kg vasopressin (n = 7), or saline placebo (n = 4) was administered in a blinded, randomized manner. Defibrillation was attempted 2.5 min after drug administration, and all animals were subsequently observed for 1 h without further intervention. Spontaneous circulation was restored in 7 of 7 vasopressin animals, in 6 of 7 epinephrine pigs, and in 0 of 4 placebo swine. At 5 and 30 min after return of spontaneous circulation, median (minimum and maximum) renal blood flow after epinephrine was 2 (0-31), and 2 (0-48) mL. 100 g(-1). min(-1), respectively; and after vasopressin 96 (12-161), and 44 (16-105) mL. 100 g(-1). min(-1), respectively (P: <.01 between groups). Epinephrine animals developed a profound metabolic acidosis by 15 min after return of spontaneous circulation (mean arterial pH, 7.11 +/- 0.01), and by 60 min all epinephrine-treated animals had died. The vasopressin pigs had (P: = 0.015) less acidosis (pH = 7.26+/-0. 04) at corresponding time points, and all survived > or =55 min (P: < 0. 01). In conclusion, treatment of hypovolemic cardiac arrest with vasopressin, but not with large-dose epinephrine or saline placebo, resulted in sustained vital organ perfusion, less metabolic acidosis, and prolonged survival. Based on these findings, clinical evaluation of vasopressin during hypovolemic cardiac arrest may be warranted.

IMPLICATIONS

The chances of surviving cardiac arrest in hemorrhagic shock are considered dismal without adequate fluid replacement. However, treatment of hypovolemic cardiac arrest with vasopressin, but not with large-dose epinephrine or saline placebo, resulted in sustained vital organ perfusion and prolonged survival in an animal model of suspended infusion therapy.