HAEMODIALYSIS IN SEVERE BARBITURATE POISONING

Physiological Changes in Subjects Exposed to Accidental Hypothermia: An Update

Background

Accidental hypothermia (AH) is an unintended decrease in body core temperature (BCT) to below 35°C. We present an update on physiological/pathophysiological changes associated with AH and rewarming from hypothermic cardiac arrest (HCA).

Temperature Regulation and Metabolism

Triggered by falling skin temperature, Thyrotropin-Releasing Hormone (TRH) from hypothalamus induces release of Thyroid-Stimulating Hormone (TSH) and Prolactin from pituitary gland anterior lobe that stimulate thyroid generation of triiodothyronine and thyroxine (T4). The latter act together with noradrenaline to induce heat production by binding to adrenergic β3-receptors in fat cells. Exposed to cold, noradrenaline prompts degradation of triglycerides from brown adipose tissue (BAT) into free fatty acids that uncouple metabolism to heat production, rather than generating adenosine triphosphate. If BAT is lacking, AH occurs more readily.

Cardiac Output

Assuming a 7% drop in metabolism per °C, a BCT decrease of 10°C can reduce metabolism by 70% paralleled by a corresponding decline in CO. Consequently, it is possible to maintain adequate oxygen delivery provided correctly performed cardiopulmonary resuscitation (CPR), which might result in approximately 30% of CO generated at normal BCT.

Liver and Coagulation

AH promotes coagulation disturbances following trauma and acidosis by reducing coagulation and platelet functions. Mean prothrombin and partial thromboplastin times might increase by 40-60% in moderate hypothermia. Rewarming might release tissue factor from damaged tissues, that triggers disseminated intravascular coagulation. Hypothermia might inhibit platelet aggregation and coagulation.

Kidneys

Renal blood flow decreases due to vasoconstriction of afferent arterioles, electrolyte and fluid disturbances and increasing blood viscosity. Severely deranged renal function occurs particularly in the presence of rhabdomyolysis induced by severe AH combined with trauma.

Conclusion

Metabolism drops 7% per °C fall in BCT, reducing CO correspondingly. Therefore, it is possible to maintain adequate oxygen delivery after 10°C drop in BCT provided correctly performed CPR. Hypothermia may facilitate rhabdomyolysis in traumatized patients. Victims suspected of HCA should be rewarmed before being pronounced dead. Rewarming avalanche victims of HCA with serum potassium > 12 mmol/L and a burial time >30 min with no air pocket, most probably be futile.

The Efficacy of Renal Replacement Therapy for Rewarming of Patients in Severe Accidental Hypothermia-Systematic Review of the Literature

Background: Renal replacement therapy (RRT) can be used to rewarm patients in deep hypothermia. However, there is still no clear evidence for the effectiveness of RRT in this group of patients. This systematic review aims to summarize the rewarming rates during RRT in patients in severe hypothermia, below or equal to 32 °C. Methods: This systematic review was registered in the PROSPERO International Prospective Register of Systematic Reviews (identifier CRD42021232821). We searched Embase, Medline, and Cochrane databases using the keywords hypothermia, renal replacement therapy, hemodialysis, hemofiltration, hemodiafiltration, and their abbreviations. The search included only articles in English with no time limit, up until 30 June 2021. Results: From the 795 revised articles, 18 studies including 21 patients, were selected for the final assessment and data extraction. The mean rate of rewarming calculated for all studies combined was 1.9 °C/h (95% CI 1.5–2.3) and did not differ between continuous (2.0 °C/h; 95% CI 0.9–3.0) and intermittent (1.9 °C/h; 95% CI 1.5–2.3) methods (p > 0.9). Conclusions: Based on the reviewed literature, it is currently not possible to provide high-quality recommendations for RRT use in specific groups of patients in accidental hypothermia. While RRT appears to be a viable rewarming strategy, the choice of rewarming method should always be determined by the specific clinical circumstances, the available resources, and the current resuscitation guidelines.

The efficiency of continuous renal replacement therapy for rewarming of patients in accidental hypothermia--An experimental study

Severe accidental hypothermia carries high mortality and morbidity and is often treated with invasive extracorporeal methods. Continuous veno-venous hemodiafiltration (CVVHDF) is widely available in intensive care units. We sought to provide theoretical basis for CVVHDF use in rewarming of hypothermic patients. CVVHDF system was used in the laboratory setting. Heat balance and transferred heat units were evaluated for the system without using blood. We used 5L of crystalloid solution at the temperature of approximately 25°C, placed in a thermally insulated tank (representing the "central compartment" of a hypothermic patient). Time of warming the central compartment from 24.9 to 30.0°C was assessed with different flow combinations: "blood" (central compartment fluid) 50 or 100 or 150 mL/min, dialysate solution 100 or 1500 mL/h, and substitution fluid 0 or 500 mL/h. The total circulation time was 1535 minutes. There were no differences between heat gain values on the filter depending on blood flow (P = .53) or dialysate flow (P = .2). The mean heating time for "blood" flow rates 50, 100, and 150 mL/min was 113.7 minutes (95% CI, 104.9-122.6 minutes), 83.3 minutes (95% CI, 76.2-90.3 minutes), and 74.7 minutes (95% CI, 62.6-86.9 minutes), respectively (P < .01). The respective median rewarming rate for different "blood" flows was 3.6°C/h (IQR, 3.0-4.2°C/h), 4.8 (IQR, 4.2-5.4°C/h), and 5.4 (IQR, 4.8-6.0°C/h), respectively (P < .01). The dialysate flow did not affect the warming rate. Based on our experimental model, CVVHDF may be used for extracorporeal rewarming, with the rewarming rates increasing achieved with higher blood flow rates.

Recurrent Admissions for Hypothermia From Concomitant Topiramate and Phenobarbital: A Case Report

Introduction:

This article presents an additional case of concomitant topiramate and phenobarbital administration that resulted in 8 hospital admissions for hypothermia that resolved after discontinuation of phenobarbital.

Case:

A 56-year-old white female with cerebral palsy and quadriplegia, epilepsy, and hypothyroidism was admitted to a community teaching hospital multiple times with documented hypothermia. These admissions followed a subsequent dose increase of topiramate in December 2014. In February 2015, the patient was admitted with 35°C rectal temperature. Her 2 admissions in April were for hypothermia with temperatures of 34.6°C and 33.6°C, respectively. The patient had 5 other admissions with hypothermia through December 2015. All other causes of hypothermia were ruled out. The hypothermia resolved when phenobarbital was discontinued.

Discussion:

A recent case series noted an association between phenobarbital and topiramate causing hypothermia. The patient’s hypothermia developed while on concomitant phenobarbital and topiramate but only after an increase in topiramate. No other causes for hypothermia were found based upon physical examination or lab work. The Naranjo nomogram noted a probable causation.

Conclusion:

This case report points to an association of hypothermia with concomitant topiramate and phenobarbital with resolution after phenobarbital discontinuation. Improvement after discontinuation of phenobarbital seems to support a drug-effect relationship.

Rewarming by hemodialysis for hypothermia: failure of heparin to prevent DIC

Disseminated intravascular coagulation (DIC) is an infrequent but known complication of hypothermic injury. Previous work with a dog model had indicated that DIC could be prevented if the animals were treated with heparin prior to rewarming. We report here the case of a young man treated with core rewarming by hemodialysis who developed DIC despite the use of heparin during dialysis.

Multicenter hypothermia survey

A multicenter survey evaluated the clinical presentation, treatment, and outcome of accidental hypothermia. Data were collected from 13 emergency departments, with 401 of the 428 cases presenting during a two-year study period. Core temperatures ranged from 35 C to 15.6 C (mean, 30.57 C +/- 3.53) with 272 cases (63.6%) less than or equal to 32.2 C. There were no significant differences by age in presenting temperature, rewarming strategies, or mortality. The first hour rewarming rate was significantly (P less than .05) faster in the population less than or equal to 59 years (1.08 +/- 1.39 C/hr) than in those greater than or equal to 60 years (0.75 +/- 1.16 C/hr). Male core temperatures averaged 30.27 +/- 3.44 C versus female temperatures of 31.1 +/- 3.61 C. There were no clinically significant differences in male (N = 296) versus female (N = 132) profiles. High ethanol levels (315 to 800 mg%) did not affect outcome. Nine of 27 (33%) patients who received CPR initiated in the field survived, versus six of 14 (43%) with CPR begun in the ED. The profile of the CPR versus non-CPR population differed significantly (P less than .05) in location (outdoors), initial temperature (24.8 +/- 3.77 C vs 30.94 +/- 3.12 C), third-hour rewarming rate (2.28 +/- 1.53 C vs 1.17 +/- 1.18 C/hr), and numerous laboratory parameters. Tracheal intubation was performed without incident in 117 cases, of which 97 were less than or equal to 32.2 C. There were 73 fatalities (17.1%). Of these, 84.9% (N = 62) were less than or equal to 32.2 C. Predisposing conditions in this group included "serious" illness (30), systemic infection (28), trauma (15), immersion (ten), frostbite (seven), and overdose (two). The initial pulse, hemoglobin, and first-hour rewarming rate was lower in the deceased population, while the potassium, urea nitrogen, creatinine, and phosphorus were elevated. Excluding treatment combinations, outcome with exclusive use of a single rewarming strategy was passive external rewarming, 14 deaths below 32.2 C, 13 above; active external rewarming, six deaths below 32.2 C, two above; active core rewarming, 38 deaths below 32.2 C, none above. Refinements of the American Heart Association's CPR standards in hypothermia and a Hypothermia Survival Index are proposed.

Rewarming in accidental hypothermia: radio wave versus inhalation therapy

Anesthetized random-source dogs were cooled by refrigeration (3 C) to a stable core temperature of 25 C, and subsequently were rewarmed with warm, humidified inhalation (43 C, 450 mL of minute ventilation per kilogram) or radio frequency induction hyperthermia (4 to 6 watts/kg). The mean time required for core rewarming to 30 C was 231 +/- 3 minutes for warm, humidified ventilation and 106 +/- 32 minutes for radio wave therapy (P less than .01). These data suggest that radio wave heating is a more rapid noninvasive therapy for core rewarming of accidental hypothermia.

Rewarming in immersion hypothermia: radio-wave and inhalation therapy

Anesthetized random source dogs were cooled by ice water immersion (1 degree C) to a stable core temperature of 25 degrees C, and subsequently rewarmed with warm humidified inhalation (43 degrees C, 450 cc of min ventilation/kg), radio wave induction hyperthermia (4-6 W/kg) or both therapies simultaneously. The mean time required for core rewarming to 30 degrees C was 262 +/- 29 min for humidified ventilation, 68.5 +/- 6 min for radio wave therapy (P less than 0.01), and 74.8 +/- 12 for both therapies combined (P less than 0.3 vs. radio wave). There was no tissue damage with these protocols. These data suggest radio wave heating alone is the most rapid non-invasive method for core rewarming in immersion hypothermia.

Accidental hypothermia. Review of the literature

The pathophysiology and treatment of accidental hypothermia are discussed. Special attention is paid to the pathophysiologic problems of rewarming. For severely hypothermic patients we would recommend peritoneal dialysis as the method of choice for rewarming in a hospital situation. In a "field situation" passive or slow active rewarming is recommended.

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.

Ventricular fibrillation during orotracheal intubation of hypothermic dogs

Physical manipulation of the hypothermic patient is well known to cause ventricular fibrillation. Careful review of the literature fails to demonstrate a true temporal relationship between orotracheal intubation and ventricular fibrillation (VF) when acceptable temperature-corrected arterial blood gases have been obtained. Eleven mongrel dogs were anesthetized and cooled, with orotracheal intubation and extubation performed every two degrees centrigrade, starting at 27 C. Ventilator setting were adjusted to maintain normal pH according to arterial blood gases drawn every two degrees and corrected for temperature. There was only one episode of VF during 42 intubations performed at temperatures less than 28 C (2.38%). There were eight separate episodes of spontaneous VF unrelated to intubation in five dogs. Four of these five with spontaneous VF were resuscitated with countershock only, further cooled, and reintubated an additional 11 times without a single episode of VF during intubation. Our data suggest that the incidence of VF during intubation in the hypothermic patient is much less than previously described, provided that normal pH is maintained and hypoxemia is corrected.

Gastric emptying. Risk versus benefit in the treatment of acute poisoning

This review examines the various clinical options used to elicit gastric emptying, viz. drug-induced emesis, mechanical pharyngeal stimulation, gastric lavage, and catharsis. Apomorphine and syrup of ipecac are the 2 drugs most frequently used for induction of emesis. Both agents act centrally and, in addition, syrup of ipecac has a peripheral action. Toxins ingested or foods previously eaten may inhibit or enhance emetic action by interfering with mediating and conducting mechanisms. Studies indicate that both syrup of ipecac and apomorphine are similarly effective in inducing emesis; however, apomorphine has a shorter reaction time compared with syrup of ipecac. There are more risks involved with the use of apomorphine, since it causes central nervous system and respiratory depression. Syrup of ipecac has been shown to be relatively safe when used in its recommended dosage for emesis. However, several toxicities have been reported with the use of the fluid extract of ipecac. Emesis is contraindicated in patients who are obtunded or comatose, and in patients who have ingested stimulants, some hydrocarbons, or corrosives. Mechanical pharyngeal stimulation is a simple method of inducing emesis; however, it is often unsuccessful and rarely recovers a significant portion of the gastric contents. Gastric lavage is a procedure which has been relied upon for over a century. Its effectiveness is dependent on the nature, form, and dosage of the poison, latency between time of ingestion and lavage, and technique. In clinical experiments studying gastric lavage, it has been noted that the procedure is most beneficial 1 to 2 hours postingestion for the majority of poison ingestions. Lavage also provides an excellent route for activated charcoal and selected antidotes. Gastric lavage may pose several risks to the patient, including obstruction and contamination of the airways and oesophageal damage. Contraindications for gastric lavage are similar to those for emesis except that it may be safer to use in obtunded, comatose, or uncooperative patients. Cathartics used during initial poisoning therapy are usually the saline cathartics. They elicit an osmotic reaction in the small intestine which results in increased intraluminal fluid bulk, hyperperistalsis, and subsequent propulsion of contents. Cathartics have also been shown to stimulate the secretion of cholecystokinin, which is thought to have similar effects on the intestine. Cathartics have not been shown to significantly enhance drug elimination from the gastrointestinal tract.(ABSTRACT TRUNCATED AT 400 WORDS)

Controlled comparison of humidified inhalation and peritoneal lavage in rewarming of immersion hypothermia

Random source dogs were anesthetized and cooled by immersion in ice water to a stable core temperature of 25 degrees C and subsequently rewarmed with either normal saline peritoneal lavage (43 degrees C, 175 ml/kg/h) or warmed humidified inhalation (43 degrees C, 450 ml/kg/min ventilation). The time required for core rewarming to 30 degrees C was 192 +/- 61 minutes for lavage and 331 +/- 96 minutes for inhalation therapy (P less than 0.03). These data suggest that peritoneal lavage is superior to inhalation therapy for core rewarming of rapidly induced immersion hypothermia.

Neardrowning and cold water immersion

Though usually preventable, drowning remains a major cause of accidental death in our society. The lethal common denominator in drowning and neardrowning deaths is hypoxia. Aggressive treatment both at the scene and in the hospital is recommended even in those who initially appear lifeless. Hypothermia and the diving reflex probably explain the incredible survival stories in neardrowning. Remember the maxim in cold water immersion: "One is not dead until warm and dead!"

Accidental hypothermia

Knowledge of the effects of hypothermia has increased greatly over the past 25 yr. Thousands of patients have been cooled intentionally in the operating room, and hundreds of thousands of living hearts have been temporarily stopped by cold cardioplegia and restarted without difficulty or apparent ill-effect. Yet in spite of the acquisition of this vast body of clinical experience an aura of mystery stills surrounds the patient who becomes hypothermic accidentally. The best treatment in any particular case is not always clear, and published accounts do not always give the impression that the hypothermic patient is treated with the same rational approach with which other sick and comatose patients are treated. In summarizing, therefore, conclusions that might be reached from reviewing past experience several important points emerge. The severely hypothermic patient should be treated in an intensive care unit where appropriate monitoring of temperature, cardiovascular function and respiratory function are available, and where full respiratory support including assisted ventilation can be given. The final outcome depends upon the etiology. The young healthy victim of exposure has a good chance of surviving. The patient poisoned by alcohol or barbiturates has a good chance of surviving provided the level of intoxication is not itself lethal. The elderly without severe underlying disease have a good chance of surviving. The patient with severe underlying disease of the endocrine, cardiovascular or neurologic system probably has, at best, a 50% chance of surviving and, at worst, a chance of only 10-20%, depending upon the associated disease. There is no statistical evidence that any one method of rewarming is significantly better than any other. But there is anecdotal evidence that in the absence of full monitoring and support systems slow rewarming is safer than over-energetic external rewarming. Internal rewarming, peritoneal dialysis, hemodialysis, inhalation of warmed oxygen and extracorporeal circulation are effective in severe cases and can be used with safety. The causes of, and triggering mechanism for, ventricular fibrillation are still largely unknown but the onset of ventricular fibrillation in a very cold patient may often be an irreversible complication. The place of modern anti-arrhythmic drugs in the prevention and management of this complication has yet to be elucidated. Cardiopulmonary resuscitation is difficult in profoundly hypothermic patients but should be maintained until a body temperature of 30 degrees C has been achieved.(ABSTRACT TRUNCATED AT 400 WORDS)

Hypothermia: the Bellevue Experience

All adult patients (102 cases) presenting to Bellevue Hospital Medical Center over a calendar year (1978) with core temperatures less than 35 C were studied. Statistically significant correlations between hypothermia and mortality were identified according to mental status, hypoxia, hypotension, hyperamylasemia, duration and severity of hypothermia, and history of exposure and alcohol ingestion. Mortality could not be predicted on the basis of season, age (if greater than 40 years old), sex, presence of infection, or presenting temperature (if greater than 26 C). Thyroid and adrenal function were not significantly altered. Of only nine diabetic patients, four died in ketoacidosis or hyperosmolar states. There were no cases of meningitis, and the incidence of "occult" bacteremia was less than 1%. Prolonged hypothermia was uniformly associated with profound underlying medical disease. In patients presenting with temperatures less than 26 C, 50% of deaths resulted from temperature-induced ventricular arrhythmias. Alcoholics hypothermic from exposure had excellent prognoses; however, temperatures less than 26 C were associated with a marked and statistically significant incidence of death.

Accidental hypothermia: a review of 62 cases

A retrospective review of all patients seen in an urban city-county emergency department over a 32-month period with a primary or associated diagnosis of hypothermia was performed using the emergency department encounter form and the inpatient chart of 62 cases (59 patients) with core temperatures of 35 C (95 F) or below. With this relatively large population, a general conclusion was reached about the presentation and natural history of this interesting entity. This permitted a defensible treatment regimen which is currently employed a this institution and which is offered for institutions in similar settings. The variance in clinical signs, laboratory values, electrocardiographic findings and complications encountered in this study are detailed against the background of a review of the findings of the current literature.

Accidental hypothermia: core rewarming with partial bypass

Three patients with profound hypothermia were treated by rewarming on partial bypass. Two surivived and have normal mental and metabolic functions. The resuscitation of the hypothermic patient should be approached with enthusiasm since the outcome is often much better than expected from initial vital signs and neurologic examination. To avoid ventricular fibrillation the patient should be handled gently and an effort should be made to keep the patient well oxygenated and the pH normal. Blood gases should be measured often and corrected for temperature. The potassium concentration and hydration status of the patient should also be monitored closely. The rewarming of profoundly hypothermic patients can readily be accomplished with a pump oxygenator and heat exchanger. The indications for this method are not established from our small experience and the few cases reported in the literature. Certainly ventricular fibrillation is a compelling indication. Patients with frozen extremities might also benefit from this method since theoretically tissue salvage would be increased. Finally, those patients who do not respond rapidly to external rewarming may be at less risk of ventricular fibrillation if rewarmed on bypass.

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.

Treatment of the poisoned child

Syrup of ipecac has measurable advantages over gastric lavage in evacuating the stomach of children with accidental poisoning, in terms of safety, effectiveness, and rapidity of action. The average period for action with ipecac is likely to be about 17 minutes, or 82 minutes, depending on whether the child is treated at home or in hospital. In contrast, the mean delay to completion of gastric lavage is estimated at 126 minutes, and this procedure has little place in the treatment of the child with poisoning.

A system of screening for the presence of a number of common drugs

A method is described to provide a rapid screening technique for the presence of barbiturates, glutethimide, carbromal, meprobamate, salicylate, phenothiazine derivatives, bromide, carbon monoxide, and alcohol. Phenothiazines are detected by a spot urine test. The first four drugs are identified, within 60 minutes of blood collection, on thin-layer chromatoplates of microscope slide dimensions. The estimations of bromide, salicylate, carbon monoxide, and of alcohol levels are started in that period so the overall time for the screening is less than two hours, and the amount of blood required is only 10 ml.