Vasopressin and epinephrine are equally effective for CPR in a rat asphyxia model

A modified rat model of 8 minutes asphyxial cardiac arrest and cardiopulmonary resuscitation

The animal model of cardiac arrest (CA) and cardiopulmonary resuscitation (CPR) serves as a crucial tool for investigating the pathophysiology and treatment strategies associated with cardiac arrest, however, standardized procedures for such models remain insufficiently established. We aimed to modify and specify the existing rat model of asphyxial CA and CPR while providing an analysis of long-term outcomes.A total of 46 rats were allocated into two groups,sham and CA group.In CA group, cardiac arrest was induced through 8 minutes of hypoxia prior to the administration of CPR. In sham group, only tracheal intubation and vascular catheterization were conducted under isoflurane anesthesia. Key parameters along with arterial blood gas results during modeling were meticulously recorded. After a 2-week postoperative observation period, the survival rate of rats and neurobehavioral changes on days 1, 3, 7, and 14 following resuscitation were assessed. Two weeks later, a pathological examination of brain tissue was conducted to evaluate neuronal damage. Results indicated that the average duration of cardiac arrest in CA group was 292.9 ± 12.5 seconds, with a return of spontaneous circulation rate of 78.95% and a survival rate at day 14 reaching 32%. After a duration of 2 weeks, the neurobehavioral scores of the surviving rats returned to their initial baseline levels; however, pathological examination revealed evidence of neuronal damage. In conclusion, we present a refined protocol for establishing a stable rat model of asphyxial CA and CPR, which may assist researchers in this field in enhancing the success rate of modeling.

Effect of vasopressin on hippocampal injury in a rodent model of asphyxial cardiopulmonary arrest

The effect of vasopressin on the neuronal injury following the restoration of spontaneous circulation (ROSC) in cardiac arrest (CA) is not yet fully understood. The present study was conducted in order to investigate the effect of vasopressin alone, or in combination with epinephrine, on the ROSC and hippocampal injury in a rat model of asphyxial CA. Asphyxial CA was induced in 144 rats by clamping the tracheal tube, and animals were allocated equally into the following three groups: Treatment with vasopressin (0.8 U/kg); epinephrine (0.2 mg/kg); or vasopressin (0.8 U/kg) plus epinephrine (0.2 mg/kg). An additional 48 rats underwent a sham surgical procedure without asphyxial CA and cardiopulmonary resuscitation. Hippocampal tissue was harvested at 1, 3, 6 and 12 h post-ROSC, and the levels of p38 mitogen-activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) p65 were determined using immunohistochemistry. In comparison with rats treated with epinephrine alone, higher ROSC success rates were observed in rats treated with vasopressin, or vasopressin plus epinephrine. In addition, treatment with vasopressin attenuated hippocampal injury and reduced hippocampal p38 MAPK and NF-κB expression more efficiently compared with epinephrine alone. In conclusion, treatment with vasopressin exhibits a protective effect in patients experiencing CA, and this may be attributed to the inhibition of p38 MAPK and NF-κB expression.

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.

What is the optimal dose of epinephrine during cardiopulmonary resuscitation in a rat model?

OBJECTIVE

Because different species may require different doses of drug to produce the same physiologic response, we were provoked to evaluate the dose-response of epinephrine during cardiopulmonary resuscitation (CPR) and identify what is the optimal dose of epinephrine in a rat cardiac arrest model.

METHODS

Rat cardiac arrest was induced via asphyxia, and then the effects of different doses of epinephrine (0.04, 0.2, and 0.4 mg/kg IV, respectively) and saline on the outcome of CPR were compared (n = 10/each group). The primary outcome measure was restoration of spontaneous circulation (ROSC), and the secondary was the change of spontaneous respiration and hemodynamics after ROSC.

RESULTS

Rates of ROSC were 9 of 10, 8 of 10, 7 of 10, and 1 of 10 in the low-dose, medium-dose, and high-dose epinephrine groups and saline group, respectively. The rates of withdrawal from the ventilator within 60 minutes in the low-dose (7 of 9) and medium-dose epinephrine groups (7 of 8) were higher than in the high-dose epinephrine group (1 of 7, P < .05). Mean arterial pressures were comparable, but the heart rate in the high-dose epinephrine group was the lowest among epinephrine groups after ROSC. These differences in part of time points reached statistical significance (P < .05).

CONCLUSION

Different doses of epinephrine produced the similar rate of ROSC, but high-dose epinephrine inhibited the recovery of spontaneous ventilation and caused relative bradycardia after CPR in an asphyxial rat model. Therefore, low and medium doses of epinephrine were more optimal for CPR in a rat asphyxial cardiac arrest model.

Dose-response of vasopressin in a rat model of asphyxial cardiac arrest

The advantage of vasopressin over epinephrine in the treatment of cardiac arrest (CA) is still being debated, and it is not clear whether a high dose of vasopressin is beneficial or detrimental during or after cardiopulmonary resuscitation (CPR) in a rat model of CA. In this study, asphyxial CA was induced in 40 male Sprague-Dawley rats. After 10 minutes of asphyxia, CPR was initiated; and the effects of different doses of vasopressin (low dose, 0.4 U/kg; medium dose, 0.8 U/kg; and high dose, 2.4 U/kg; intravenous; n = 10 in each group) and a saline control (isotonic sodium chloride solution, 1 mL, intravenous) were compared. Outcome measures included the rate of restoration of spontaneous circulation (ROSC) and changes of hemodynamic and respiratory variables after ROSC. The rates of ROSC were 1 of 10 in the saline group and 8 of 10 in each of the 3 vasopressin groups. There were no differences in mean aortic pressure or changes of respiratory function after CPR among the vasopressin groups. However, the heart rate was lower in the high-dose vasopressin group than in the low- and medium-dose groups. These findings indicate that different doses of vasopressin result in a similar outcome of CPR, with no additional benefits afforded by a high dose of vasopressin during or after CPR, in a rat model of asphyxial CA. The mechanism and physiologic significance of the relative bradycardia that occurred in the high-dose vasopressin group are currently unknown and require further investigation.

The use of mice and rats as animal models for cardiopulmonary resuscitation research

Cardiopulmonary resuscitation (CPR) after the induction of cardiac arrest (CA) has been studied in mice and rats. The anatomical and physiological parameters of the cardiopulmonary system of these two species have been defined during experimental studies and are comparable with those of humans. Moreover, these animal models are more ethical to establish and are easier to manipulate, when compared with larger experimental animals. Accordingly, the effects of successful CPR on the function of vital organs, such as the brain, have been investigated because damage to these vital organs is of concern in CA survivors. Furthermore, the efficacy of several drugs, such as adrenaline (epinephrine), vasopressin and nitroglycerin, has been evaluated for use in CA in these small animal models. The purpose of these studies is not only to increase the rate of survival of CA victims, but also to improve their quality of life by reducing damage to their vital organs after CA and during CPR.

Epinephrine, but not vasopressin, improves survival rates in an adult rabbit model of asphyxia cardiac arrest

Although vasopressin has been reported to be more effective than epinephrine for cardiopulmonary resuscitation in ventricular fibrillation animal models, its efficacy in asphyxia model remains controversy. The purpose of this study was to investigate the effectiveness of vasopressin vs epinephrine on restoration of spontaneous circulation (ROSC) in a rabbit model of asphyxia cardiac arrest. Cardiac arrest was induced by clamping endotracheal tube. After 5 minutes of basic life-support cardiopulmonary resuscitation, animals who had no ROSC were randomly assigned to receive either epinephrine alone (epinephrine group; 200 microg/kg) or vasopressin alone (vasopressin group; 0.8 U/kg). The coronary perfusion pressure (CPP) was calculated as the difference between the minimal diastolic aortic and simultaneously recorded right atrial pressure. Restoration of spontaneous circulation was defined as an unassisted pulse with a systolic arterial pressure of 60 mm Hg or higher for 5 minutes or longer. We induced arrest in 62 rabbits, 15 of whom had ROSC before drug administration and were excluded from analysis. The remaining 47 rabbits were randomized to epinephrine group (n = 24) and vasopressin group (n = 23). Before and after drug administration, CPP in epinephrine group increased significantly (from -4 +/- 4 to 36 +/- 9 mm Hg at peak value, P = .000), whereas CPP in vasopressin group increased only slightly (from 9 +/- 5 to 18 +/- 6 mm Hg at peak value, P = .20). After drug administration, 13 of 24 epinephrine rabbit had ROSC, and only 2 of 23 vasopressin rabbit had ROSC (P < .01). Consequently, we conclude that epinephrine, but not vasopressin, increases survival rates in this adult rabbit asphyxia model.

Vasopressor agents: old and new components

PURPOSE OF REVIEW

In settings of cardiac arrest, reestablishing vital organ perfusion plays an important role in initial CPR. As a pharmacologic intervention, vasopressor agents aim to improve aortic diastolic pressure and, consequently, coronary and cerebral perfusion pressures.

RECENT FINDINGS

Historically, adrenergic agonists such as epinephrine have been suggested for routine use in CPR. However, epinephrine's efficacy is controversial because of its unfavorable inotropic and chronotropic action. This has prompted research into the use of alternative pressor agents with more promising hemodynamic features; these include selective alpha 2-adrenergic agonists and other nonadrenergic vasoconstrictors such as vasopressin.

SUMMARY

In this article, the main traditional and novel adrenergic and nonadrenergic vasopressor drugs are reviewed.

Vasopressin with delayed combination of nitroglycerin increases survival rate in asphyxia rat model

Recently, vasopressin has been reported as a more effective drug than epinephrine (adrenaline) for cardiopulmonary resuscitation (CPR). However, vasopressin decreases myocardial blood flow (MBF) because of its strong vasoconstriction, to maintain better coronary perfusion pressure (CPP) compared with epinephrine. Nitroglycerin is well known to be able to maintain MBF and increase survival rate. In a VF model, vasopressin combined with nitroglycerin maintained CPP; however, low survival rates were observed compared with vasopressin alone. We investigated the effectiveness of the delayed use of nitroglycerin combined with vasopressin in a severe asphyxia model. Fourteen Sprague-Dawley male rats were divided into two groups: vasopressin 0.8 U/kg alone (V-Gr.), and nitroglycerin 0.3 microg/kg 45 s after the administration of 0.8 U/kg vasopressin (VN-Gr.). Six min after asphyxia induced by obstructing the tracheal tube, CPR was performed in two ways. Three animals resuscitated in the V-Gr. (42%) and six/seven (84%) in the VN-Gr. (P<0.05). In the 6 min of asphyxia rat model, vasopressin combined with delayed nitroglycerin is more effective than vasopressin alone.