THE MECHANISM OF SHOCK FOLLOWING SUICIDAL DOSES OF BARBITURATES, NARCOTICS AND TRANQUILIZER DRUGS, WITH OBSERVATIONS ON THE EFFECTS OF TREATMENT

Complications associated with barbiturate therapy

Fifty-six patients with elevated intracranial pressure caused by cerebrovascular accident, head injury, etc., were the subjects of this study. They were divided into three groups: low dose barbiturate therapy (15 patients), high dose barbiturate therapy (24 patients), and control group (17 patients). Barbiturate therapy was instituted using thiamylal, and the complications caused by barbiturate therapy were recorded. In the control group, complications occurred in the liver of two patients, but there were no renal or pulmonary complications. Pulmonary, renal, and hepatic complications were common in the barbiturate groups. Complications in the high dose therapy group were significantly more common than in the control group. Opportunistic infections occurred in ten patients, with seven patients having pneumonia. Only one patient, with pneumonia, was seen in the control group. The deaths of three patients were influenced by complications associated with barbiturate therapy, while the single death in the control group was not associated with the complication of barbiturate therapy.

Barbiturate and nonbarbiturate sedative hypnotic intoxication in children

This article reviews the pharmacology, toxicology, and treatment of both barbiturate and nonbarbiturate sedative hypnotic overdose. Although poisoning with these agents has declined over recent years, intoxication with them can still result in a life-threatening situation requiring immediate assessment and treatment.

Antidotal treatment of the acute cardiovascular toxicity of verapamil

Rats anaesthetized with pentobarbital and ventilated artificially were infused with 0.15 mg/kg/min. verapamil; without antidotal treatment, they died after 51.1+/-7.1 min. The survival time more than trebled upon an additional infusion with calcium chloride, epinephrine, isoprenaline, orciprenaline or prenalterol and nearly doubled upon administration of a plasma expander. It was not increased, however, by treatment with angiotensin or atropine. The infusion of verapamil declined the arterial blood pressure by 75%, and heart rate, cardiac output and peripheral resistance by about 50%; in the ECG, sinus bradycardia followed by AV-dissociation with nodal rhythm occurred. All antidotes that raised the lethal dose of verapamil increased the cardiac output. Calcium and the sympathomimetics with alpha-adrenergic activity also counteracted the verapamil-induced hypotension. Calcium did not influence the ECG alterations produced by verapamil, while the sympathomimetics restored the sinus rhythm or accelerated the nodal pacemaker. Calcium, epinephrine and isoprenaline also antagonized the strong decrease of left-ventricular dp/dt max. induced by verapamil. In conclusion, calcium as well as sympathomimetic amines are potent antidotes against the cardiovascular toxicity of verapamil, the latter being superior to calcium in their ability to improve pacemaker activity and AV-conduction.

The immediate management of overdose

Success in reviving victims of overdose may be achieved by careful attention to cardiovascular and respiratory support and a high urinary output. In addition to these general principles, special measures may be indicated in cases of specific drug overdose. Such measures are outlined for various drugs, including acetaminophen, aspirin, phencyclidine, barbiturates, and organophosphates.

Oxygen transport, consumption and utilization during barbiturate intoxication

Factors related to oxygen availability and requirements were measured on 51 occasions in 14 patients intoxicated with short-acting barbiturates. Patients had no clinical signs of circulatory shock. The cardiac index was normal (3.4 +/- 1.1 1/min/m2) but there was a slight decrease of the mean arterial oxygen content (17.2 +/- 3.0 ml/100 ml). Oxygen transport was normal (571 +/- 199 ml/min/m2). However, the arteriovenous oxygen differences were decreased (3.4 +/- 1.0 ml/100 ml). Oxygen consumption was reduced (110 +/- 42 ml/min/m2) and the oxygen extraction ratio (oxygen consumption/oxygen transport) was decreased (0.20 +/- 0.05), thus confirming a decreased oxygen utilization. Arterial concentration of lactate was normal. Accordingly the observed decrease in oxygen consumption was related to a reduction in oxygen requirements during barbiturate intoxication rather than due to an imbalance between availability and metabolic requirements for oxygen.

Significance of hyperlactatemia in acute hypnotic drug poisoning

Lactate concentration, fibrinogen and fibrin(ogen) -- degradation-products in central venous blood were analysed in 35 unconscious patient with acute hypnotic drug poisoning (HDP) and compared with the results in 13 healthy control persons undergoing the same degree of forced diuresis via central venous catheters. Blood samples were taken on admission and at 12 h intervals up to 36 h after admission. Patients with HDP were attributed to the categories of moderate intoxications (n = 17) and severe intoxications (n = 18) according to their clinical condition. On admission, blood lactate was significantly higher in severe intoxication (3.90 +/- 2.94 mmol/l) as compared to the control group (1.25 +/- 0.17 mmol/l). Blood lactate was less elevated in moderate poisoning (2.74 +/- 1.22 mmol/l). Thirty-six hours after admission blood lactate was completely normalised in patients with moderate intoxication (1.19 +/- 0.69 mmol/l) but still significantly elevated in severely poisoned patients (2.26 +/- 1.48 mmol/l). Lactate concentration was above normal in 15 out of 17 patients with moderate and in 17 out of 18 patients with severe poisoning. A statistically significant linear correlation existed between the duration of unconsciousness and the maximal lactate concentration within 12 hrs after admission. For fibrinogen concentrations statistically significant differences were observed neither between groups nor across time. Titers of FDP were elevated in 9 out of 11 patients with moderate and to a higher degree in all patients with severe poisoning, indicating low rate DIC. Hyperlactatemia is a frequent finding in acute hypnotic drug poisoning. Blood lactate estimations may improve the evaluation of the severity of poisoning and the efficacy of therapeutic interventions.

Pharmacokinetics of drug overdose

Pharmacokinetics of drugs taken in overdose may differ from those observed following therapeutic doses. Differences are due both to dose-dependent changes and to effects of drugs or pathophysiological consequences of the overdose on kinetics. Dose-dependent changes in rate and extent of absorption, bioavailability (saturation of first-pass metabolism), distribution (saturation of protein binding sites) and metabolism are discussed. Gastrointestinal motility is affected both by specific drug actions, such as delayed gastric emptying by anticholinergic drugs, and by general nervous system depression caused by many drugs. Drug-induced circulatory insufficiency may retard tissue distribution and reduce clearance. Disturbances in blood and urine pH may alter distribution and clearance of weak acids and bases. Drug-induced renal or hepatic failure can significantly decrease clearance. Hypothermia is a common complication of drug overdose and might retard distribution and also reduce clearance. The data concerning pharmacokinetics during overdose are usually incomplete and difficult to interpret. Doses and times of ingestion are uncertain, duration of blood and urine sampling is often inadequate to distinguish absorption from distribution and elimination phases, active metabolites are not measured, protein binding is not determined and clinical features of patients not adequately described. We have, however, reviewed available data for salicylate, paracetamol (acetaminophen), barbiturates, ethchlorvynol, glutethimide, chloral hydrate, tricyclic antidepressants, lithium, phenytoin, ethanol, theophylline, digoxin, amphetamine and phencyclidine.

Alteration of pharmacokinetic parameters for pentobarbital by ischemic stroke and reversion to normal by dexamethasone treatment

The values of the pharmacokinetic parameters for pentobarbital were determined in 18 cats, 12 of which were subjected to acute ischemic stroke by ligation of the left middle cerebral artery (LMCA). All 18 ats received 50 mg/kg sodium pentobarbital during operation. The following three experimental groups were formed: control (sham-operated); ischemic stroke plus administration of 4 mg/kg dexamethasone; and ischemic stroke without dexamethasone administration. Ischemic stroke significantly prolonged the plasma half-life of pentobarbital, but concurrent administration of dexamethasone prevented this effect. Ischemic stroke significantly reduced the plasma clearance of pentobarbital, but dexamethasone prevented this reduction. Ischemic stroke significantly increased the area under the plasma pentobarbital concentration-time curve, but dexamethasone prevented this increase. Ischemic stroke significantly reduced the volume of distribution, but dexamethasone did not prevent this reduction. The alterations of the value of these pharmacokinetic parameters for pentobarbital by ischemic stroke and reversion to normal by dexamethasone treatment are discussed in the light of certain known circulatory changes which occur secondary to ischemic stroke and dexamethasone treatment.

Severe barbiturate and paracetamol overdose: the simultaneous removal of both poisons by haemoperfusion

Charcoal haemoperfusion was successful in the treatment of severe butobarbitone poisoning complicated by resistant hypotension. At the same time the rapid removal of paracetamol may have lessened the severity of the subsequent hepatic injury. The mechanism and management of shock associated with barbiturate poisoning, and the possible application of haemoperfusion in paracetamol poisoning are discussed.

[Acute respiratory insufficiency associated with the ingestion of central nervous system depressants]

The study of twenty patients with poisoning by central nervous system depressant drugs is reported. The authors emphasized clinical aspects, complications and mainly the lung function impairment. Barbiturates were the most common drugs, at least in 60% of the cases, used alone or in combination with sedatives and tranquilizers. In 55% of patients the amount of the drug ingested could not be measured. In 60% of the cases we didn't know the period of time between drug ingestion by the patients and their admission to the hospital. On admisson all patients were in coma. The coma was of varying degrees and the deeper the coma the worse was lung function and complications were more frequent. Whenever a cardiovascular collapse was present there was also a high mortality rate. The authors emphasized the importance of a follow-up of these patients in intensive care units, mainly with cardiovascular and ventilatory support.

Afterload reduction with phentolamine in patients with acute pulmonary edema

Phentolamine in amounts of 10 to 40 microgram/kg/min was infused intravenously for the emergency treatment of acute pulmonary edema due to left ventricular failure. Fourteen patients with arteriosclerotic heart disease, ranging in age from 52 to 87 years, had clinical and roentgenographic signs of pulmonary edema. The pulmonary artery wedge pressure was increased to an average of 24 mm Hg and the cardiac index was decreased to 1.9 liters/min/m2 or less prior to the administration of phentolamine. A reduction in the pulmonary artery wedge pressure to 14 mm Hg and an increase in the cardiac index to 2.5 liters/min/m2 was observed in response to this alpha adrenergic blocking agent. Reduction in peripheral resistance with phentolamine was associated with reversal of pulmonary edema.

Severe drug overdose: results of treatment

The incidence and management of severe drug overdose patients over a five-year period is presented, together with results and complications. Emphasis is placed on the importance of conservative measures with minimal need for more aggressive methods of treatment.

Barbiturate protection from cerebral infarction in primates

Baboons were anesthetized with halothane or pentobarbital prior to middle cerebral artery (MCA) occlusion to test the protective effect of barbiturates against stroke in primates. Significantly less infarction was found in animals that received 90 mg per kilogram pentobarbital or more than occurred in control animals. Because of cardiovascular and ventilatory complications at high doses of barbiturate, however, therapeutic trials to suppress stroke in the human must await further identification of an effective regimen which includes a safe barbiturate dose.

A simple plan for the management of drug overdosage

Using a purely supportive regime of management a survival rate of 99·6 per cent has been obtained in 1,166 patients admitted to hospital as a result of drug overdosage. Based on this experience, the principles of treatment are discussed.