Does naloxone alone increase resuscitation rate during cardiopulmonary resuscitation in a rat asphyxia model?

NAloxone CARdiac Arrest Decision Instruments (NACARDI) for targeted antidotal therapy in occult opioid overdose precipitated cardiac arrest

BACKGROUND

We have recently demonstrated that a significant proportion of fatal out-of-hospital cardiac arrests (OHCAs) are precipitated by occult overdose, which could benefit from antidote therapy administered adjunctively with other cardiac resuscitation measures. We sought to develop simple decision instruments that EMS providers and other first responders can use to rapidly identify occult opioid overdose-associated OHCAs.

METHODS

We examined data from February 2011 through December 2017 in the Postmortem Systematic Investigation of Sudden Cardiac Death study, in which San Francisco (California) County EMS-attended OHCA deaths received autopsy and expert panel adjudication of cause of death. Using classification tree analyses, we derived highly sensitive and specific decision instruments that predicted our primary outcome of occult opioid OD-associated OHCA. We then calculated screening performance characteristics of these instruments.

RESULTS

Of 767 OHCA deaths, 80 (10.4%) were associated with occult opioid overdose. Of the eight models with 100% sensitivity for opioid overdose-associated cardiac arrest, the highest specificity model (23.4%, 95% confidence interval [CI] 20.3-26.7%) was age < 60 years OR race = black or non-Latinx white OR arrest in public place. The highest specificity instrument (96.3%, 95% CI 94.6-97.5%) consisting of age < 60 years AND race = black or non-Latinx white AND unwitnessed arrest AND female sex had 25% (95% CI 16-35.9%) sensitivity.

CONCLUSIONS

We have derived simple decision instruments that can identify patients whose OHCA precipitant was occult opioid overdose. These instruments may be used to guide selective administration of the antidote naloxone in OHCA resuscitations.

Effects of terlipressin and naloxone compared with epinephrine in a rat model of asphyxia-induced cardiac arrest

OBJECTIVE

To evaluate the hemodynamic and metabolic effects of terlipressin and naloxone in cardiac arrest.

METHODS

Cardiac arrest in rats was induced by asphyxia and maintained for 3.5 minutes. Animals were then resuscitated and randomized into one of six groups: placebo (n = 7), epinephrine (0.02 mg/kg; n = 7), naloxone (1 mg/kg; n = 7) or terlipressin, of which three different doses were tested: 50 µg/kg (TP50; n = 7), 100 µg/kg (TP100; n = 7) and 150 µg/kg (TP150; n = 7). Hemodynamic variables were measured at baseline and at 10 (T10), 20 (T20), 30 (T30), 45 (T45) and 60 (T60) minutes after cardiac arrest. Arterial blood samples were collected at T10, T30 and T60.

RESULTS

The mean arterial pressure values in the TP50 group were higher than those in the epinephrine group at T10 (165 vs. 112 mmHg), T20 (160 vs. 82 mmHg), T30 (143 vs. 66 mmHg), T45 (119 vs. 67 mmHg) and T60 (96 vs. 66.8 mmHg). The blood lactate level was lower in the naloxone group than in the epinephrine group at T10 (5.15 vs. 10.5 mmol/L), T30 (2.57 vs. 5.24 mmol/L) and T60 (2.1 vs. 4.1 mmol/L).

CONCLUSIONS

In this rat model of asphyxia-induced cardiac arrest, terlipressin and naloxone were effective vasopressors in cardiopulmonary resuscitation and presented better metabolic profiles than epinephrine. Terlipressin provided better hemodynamic stability than epinephrine.

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.

Naloxone combined with epinephrine decreases cerebral injury in cardiopulmonary resuscitation

BACKGROUND

Cardiopulmonary arrest is a serious disease that claims many lives every day; 30% of the patients suffer irreversible central nervous system injury after restoration of systemic circulation (ROSC).

OBJECTIVES

Naloxone combined with epinephrine was tested in a cardiac arrest rat model in which asphyxia was induced to determine if this drug combination could increase the resuscitation rate (survival) and decrease the cerebral damage.

METHODS

Twenty-four male Wistar rats were randomly assigned to one of three groups: the group treated with 1 mL saline (SA group; n = 8), the group treated with only epinephrine 5 microg/100 g (EP group; n = 8), or the group treated with epinephrine 5 microg/100 g combined with naloxone 1 mg/kg (NA group; n = 8). Eight minutes after arrest, cardiopulmonary resuscitation was initiated and the different drugs were administered to the rats in their respective groups at the same time. Mean arterial pressure (MAP), heart rate (HR), and neurodeficit score (NDS) were measured.

RESULTS

The HR in the NA group (414 +/- 45 beats/min) was faster than in the EP group (343 +/- 29 beats/min) at the 5-min time point (P < 0.01). The HR in the NA group was 392 +/- 44 beats/min and 416 +/- 19 beats/min at the 60-min and 180-min time points, respectively. There were no statistically significant differences in MAP before or after ROSC. The rates of ROSC were 2 of 8, 6 of 8, and 7 of 8 animals in the SA group, EP group, and NA group, respectively. Three days later, the rates decreased to 1, 3, and 5 in the SA group, EP group, and NA group, respectively. The average resuscitation time in the NA group was significantly shorter than in the other two groups. The NDS in the NA group was 57 +/- 13, higher than in the EP group (45 +/- 13) and SA group (38).

CONCLUSION

Naloxone combined with epinephrine significantly increased the resuscitation rate in a rat model. Furthermore, the combination of naloxone and epinephrine increased the NDS after cardiopulmonary resuscitation.

Endogenous opiates and behavior: 2006

This paper is the 29th consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning 30 years of research. It summarizes papers published during 2006 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurological disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).

A simpler cardiac arrest model in the mouse

OBJECTIVE

Delivering alternating currency (AC) to right ventricular endocardium to induce ventricular fibrillation (VF) in mice is complicated. We tried to validate whether transoesophageal AC stimulation could induce VF and how long AC stimulation had to be sustained to prevent the spontaneous cardioversion of VF in mice.

METHODS

A pacing electrode was inserted orally into the oesophagus and AC was delivered to esophagus through the pacing electrode to stimulate the heart and induce VF in 15 mice. The incidence of VF and time of AC stimulation were recorded 4min after onset of VF cardiopulmonary resuscitation (CPR) was started.

RESULTS

VF was induced by short AC stimulation in all 15 mice. With the prolongation of AC stimulation, the incidences of spontaneous cardioversion of VF decreased whereas the incidence of pulseless electrical activity (PEA) increased accordingly. Following the termination of prolonged AC stimulation, VF occurred only in 1 of 15 mice, but PEA in 14 of 15 mice. Before CPR 1 of 15 and 12 of 15 animals remained in VF and in PEA, respectively, while 2 of 15 animals developed into asystole. After CPR, 11 of 15 animals were successfully resuscitated.

CONCLUSION

VF can be induced by a short period of transoesophageal AC stimulation in mice. However, prolonged AC stimulation is prone to induce PEA other than VF. Nonetheless, the development of a mouse CA model in this manner is simpler and easier, which may have practical significance for facilitating experimental investigation on CA and CPR.

Ventricular fibrillation induced by transoesophageal cardiac pacing: A new model of cardiac arrest in rats

OBJECTIVE

To investigate whether transoesophageal cardiac pacing can induce ventricular fibrillation (VF) and how long the cardiac pacing has to be sustained to prevent the reversion of the VF induced.

METHODS

A pacing electrode was inserted orally into the oesophagus and high-frequency ventricular pacing was performed so as to elicit VF in 25 Sprague-Dawley rats. Incidences of VF and time of cardiac pacing were observed and recorded. Four minutes after onset of VF cardiopulmonary resuscitation (CPR) was initiated.

RESULTS

A short interval of high-frequency ventricular pacing caused an immediate drop of blood pressure, loss of pulse and increase of right atrial pressure in the same time frame. When the cardiac pacing was terminated, VF was elicited at least once or more than once in all of the 25 rats. However, the VF elicited by the burst stimulation could be defibrillated spontaneously. With the prolongation (120-180 s) of cardiac pacing, the incidence of defibrillation of VF decreased from 100 to 0%. VF persisted in 19 of 25 animals, developed into asystole in 5 of 25 animals and converted into pulseless electrical activity in 1 of 25 animals prior to CPR. Following CPR 22 of 25 animals were resuscitated.

CONCLUSIONS

Transoesophageal cardiac pacing can induce VF in rats. However, the cardiac pacing is required for at least 120-180 s to ensure that VF does not spontaneously convert. We can use the technique to establish a new and simpler rat cardiac arrest (CA) model, which may facilitate experimental investigation on CPR.

A simpler cardiac arrest model in rats

Two disadvantages of electrical induction of cardiac arrest used currently are that it is a technically complicated procedure and the consequent thermal injury, which prompts us to search for a simpler method with less adverse effect to induce ventricular fibrillation (VF) in rats. Different potential (18, 24, 30, and 36 V) of alternating current (AC) were administered to elicit VF in 15 rats via pacing electrode placed in esophagus. Four minutes after onset of VF, conventional cardiopulmonary resuscitation (CPR) was initiated. Restoration of spontaneous circulation was defined as the return of supraventricular rhythm with a mean aortic pressure of 20 mm Hg or greater for a minimum of 5 minute. Ventricular fibrillation was achieved by short interval of AC stimulation in all of the rats. After the termination of prolonged AC stimulation, electrocardiogram indicated VF occurred in 6 of 15 rats, asystole in 3 of 15 rats and pulseless electrical activity in 6 of 15 rats. Before CPR, however, electrocardiogram indicated that only 2 of 15 and 4 of 15 animals remained in VF and pulseless electrical activity, respectively, whereas 9 of 15 animals presented as asystole. After CPR, 11 of 15 animals were resuscitated. Necropsy showed that there was no gross evidence of thermal injury on the surface layer of the heart. Therefore, development of a rat cardiac arrest model by transesophageal AC stimulation is simpler and less adverse effect, which may have practical significance for facilitating experimental investigation on cardiac arrest and 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.

Toxicologic issues during cardiopulmonary resuscitation

PURPOSE OF REVIEW

The following review intends to outline the unique aspects of providing cardiopulmonary resuscitation for the poisoned patient and highlights both current practice and new therapies that apply to toxicologic cases.

RECENT FINDINGS

Although there are few prospective randomized studies to further evidence-based care of the poisoned patient, there have been several reports of novel uses of both established medications and new medications in toxicologic patients. These case reports highlight treatment possibilities and potential avenues for further research.

SUMMARY

It is important for providers to recognize the limitations of standard advanced cardiac life support algorithms when caring for poisoned patients. Toxicologic causes of cardiopulmonary compromise should be considered along with administration of appropriate antidotes and adjunctive therapies.