The effects of dopamine on central hemodynamics and myocardial metabolism in experimental propoxyphene-induced shock

Adverse cardiac manifestations following dextropropoxyphene overdose: can naloxone be helpful?

Dextropropoxyphene overdose may be complicated by serious cardiovascular manifestations, including conduction abnormalities and collapse. We report two patients in whom cardiac toxicity developed. Cardiovascular depression seemed to be improved after naloxone infusion in these two cases. Possible mechanisms are briefly discussed.

Dopamine and dobutamine reduce myocardial d-propoxyphene content in experimentally intoxicated rats

The effect of sympathomimetic intervention with dopamine or dobutamine on the myocardial uptake of d-propoxyphene was investigated experimentally in rats. The d-propoxyphene (19 mg kg-1 h-1) was continuously infused, intravenously, over 45 min. After 20 min of infusion the rats were given either dopamine (12.5 micrograms kg-1 min-1 or 25 micrograms kg-1 min-1), dobutamine (25 micrograms kg-1 min-1 or 45 micrograms kg-1 min-1) or normal saline (control). Each group consisted of eight rats. The myocardial d-propoxyphene content was significantly lower in the two groups given dopamine and in the group given dobutamine 45 micrograms kg-1 min-1 than in the control group (P less than 0.05). This finding indicates the benefit of early sympathomimetic intervention with either dopamine or dobutamine in d-propoxyphene intoxication.

Marked QRS complex abnormalities and sodium channel blockade by propoxyphene reversed with lidocaine

The opiate analgesic propoxyphene produces cardiac toxicity when taken in overdose. We recently observed a patient with propoxyphene overdose in whom marked QRS widening was reversed by lidocaine. The reversal is apparently paradoxical as both agents block the inward sodium current (INa). We examined possible mechanisms of the reversal by measuring INa in rabbit atrial myocytes during exposure to propoxyphene and the combination of propoxyphene and lidocaine (60 and 80 microM, respectively). Propoxyphene caused use-dependent block of INa during pulse train stimulation. Block recovered slowly with time constants of 20.8 +/- 3.9 s. Block during lidocaine exposure recovered with time constants of 2-3 s. During exposure to the mixture, block recovered as a double exponential. The half time for recovery during exposure to the mixture was 1.6 +/- .9 s compared with a half-time of 14.3 +/- 2.9 s during exposure to propoxyphene alone. During pulse train stimulation, less steady-state block was observed during exposure to the mixture than during exposure to propoxyphene alone when the interval between pulses was greater than 0.95 s. Both drugs compete for a common receptor during the polarizing phase. The more rapid dissociation of lidocaine during the recovery period leads to less block during the mixture than during exposure to propoxyphene alone. The experiments suggest a mechanism for reversal of the cardiac toxicity of drugs which have slow unbinding kinetics.

Pulmonary gas exchange effects by nitroglycerin, dopamine and dobutamine during one-lung ventilation in man

The effects of nitroglycerin, dopamine and dobutamine on pulmonary gas exchange were determined in 21 adult patients during two-lung and one-lung ventilation. Nitroglycerin, in 1 microgram.kg-1.min-1, decreased cardiac index (CI) and PaO2 during both two- and one-lung ventilation, and increased in Qs/Qt during one-lung ventilation. There were no significant changes in the measured variables during infusion of dopamine, 5 microgram.kg-1.min-1. Dobutamine, 5 microgram.kg-1.min-1, increased CI and PaO2 did not change during two-lung ventilation. During one-lung ventilation, PaO2 increased from (mean value +/- SD) 168 +/- 46 to 201 +/- 52 mmHg (P less than 0.01) with dobutamine infusion. Qs/Qt decreased from 29.2 +/- 7.0 to 26.0 +/- 6.2 per cent (P less than 0.05) without any change in pulmonary vascular resistance index during one-lung ventilation. We conclude that dobutamine has advantages over dopamine and nitroglycerin during one-lung ventilation.

Cardiovascular effects of pentobarbital in pigs, and the lack of response to naloxone in pentobarbital induced circulatory failure

The hemodynamic effects of pentobarbital were tested in an experimental model used for cardiovascular research. Anesthesia was induced with an i.v. bolus and maintained with a continuous infusion of pentobarbital. The cardiovascular performance was then evaluated at various pentobarbital plasma concentrations ranging from 25 to 100 mg X l-1. Optimal experimental conditions were found at plasma pentobarbital concentrations within the range 40-60 mg X l-1, as the animals were well anesthetized with intact hemodynamics or ECG. The method of continuous pentobarbital administration seems advantageous for experimental research. Circulatory impairment following pentobarbital overdose was not affected by naloxone.

Severe acute propoxyphene overdose: plasma concentrations of propoxyphene and norpropoxyphene and the effect of dopamine on circulatory failure

Twelve patients with cardiovascular failure because of propoxyphene self-poisoning were treated with dopamine. The patients responded favourably to dopamine infusion (2-17 micrograms/kg/min) with a dose-dependent rise in systolic arterial blood pressure and a fall in central venous pressure and copious urinary output. Side effects during infusion were few, and in periods where dopamine infusion exceeded 10 micrograms/kg/min no tachyarrhythmias were seen. Eleven of the patients were treated on a respirator. Two patients were discharged from the ICU with signs of hypoxic brain damage, one of whom recovered completely after 2 weeks. Serum propoxyphene and norpropoxyphene were measured in nine patients. All but one patient had either propoxyphene or norpropoxyphene concentrations above 3 mumol/l.

Self-poisoning treated in an ICU: drug pattern, acute mortality and short-term survival

A total of 1558 admissions to an ICU over 5 years because of severe self-poisoning with drugs provides the basis for this study. Three drugs accounted for 60% of the admissions: overdose with barbiturates in 28%, with tricyclic antidepressants in 19% and with propoxyphene in 14%. The annual incidence of poisonings with barbiturates and tricyclic antidepressants was the same during the period, whereas the incidence of propoxyphene intoxication increased by 80%. Intensive supportive care was the main principle of treatment. All patients were artificially ventilated. The mortality rate was 6.1%, salicylate, propoxyphene and strong analgesics having the highest mortalities (11%, 9% and 9%, respectively). A mortality rate of 3% was found following overdose with tricyclic antidepressants. By 36 months after the overdose, 235 patients (18%) had died. The expected number of deaths was 39 (3%). The suicide rate in the follow-up period was 10%, in the majority (75%) of whom death was caused by a new episode of self-poisoning.

The effects of cardiac pacing on central hemodynamics in experimental propoxyphene-induced cardiac failure

Coronary sinus pacing was evaluated in 10 pigs during propoxyphene-induced cardiac failure. From baseline, propoxyphene chloride 15 mg . min-1 was infused until circulatory shock developed. Cardiac pacing was evaluated at different dose levels expressed as % of the shock dose of propoxyphene: at intoxication levels below 50% of the shock dose, cardiac pacing improved cardiac performance. At dose levels above 50% of the shock dose cardiac performance deteriorated further during pacing. The results are consistent with a severe negative inotropic effect of propoxyphene in overdose.