Lesson of the week. Unrecognised accidental overdose with diltiazem

Calcium Channel Blocker Ingestion: An Evidence-Based Consensus Guideline for Out-of-Hospital Management

In 2003, U.S. poison control centers were consulted after 9650 ingestions of calcium channel blockers (CCBs), including 57 deaths. This represents more than one-third of the deaths reported to the American Association of Poison Control Centers' Toxic Exposure Surveillance System database that were associated with cardiovascular drugs and emphasizes the importance of developing a guideline for the out-of-hospital management of calcium channel blocker poisoning. The objective of this guideline is to assist poison center personnel in the appropriate out-of-hospital triage and initial management of patients with suspected ingestions of calcium channel blockers. An evidence-based expert consensus process was used to create this guideline. This guideline applies to ingestion of calcium channel blockers alone and is based on an assessment of current scientific and clinical information. The expert consensus panel recognizes that specific patient care decisions may be at variance with this guideline and are the prerogative of the patient and the health professionals providing care, considering all of the circumstances involved. The panel's recommendations follow. The grade of recommendation is in parentheses. 1) All patients with stated or suspected self-harm or the recipient of a potentially malicious administration of a CCB should be referred to an emergency department immediately regardless of the amount ingested (Grade D). 2) Asymptomatic patients are unlikely to develop symptoms if the interval between the ingestion and the call is greater than 6 hours for immediate-release products, 18 hours for modified-release products other than verapamil, and 24 hours for modified-release verapamil. These patients do not need referral or prolonged observation (Grade D). 3) Patients without evidence of self-harm should have further evaluation, including determination of the precise dose ingested, history of other medical conditions, and the presence of co-ingestants. Ingestion of either an amount that exceeds the usual maximum single therapeutic dose or an amount equal to or greater than the lowest reported toxic dose, whichever is lower (see Table 5), would warrant consideration of referral to an emergency department (Grade D). 4) Do not induce emesis (Grade D). 5) Consider the administration of activated charcoal orally if available and no contraindications are present. However, do not delay transportation in order to administer charcoal (Grade D). 6) For patients who merit evaluation in an emergency department, ambulance transportation is recommended because of the potential for life-threatening complications. Provide usual supportive care en route to the hospital, including intravenous fluids for hypotension. Consider use of intravenous calcium, glucagon, and epinephrine for severe hypotension during transport, if available (Grade D). 7) Depending on the specific circumstances, follow-up calls should be made to determine outcome at appropriate intervals based on the clinical judgment of the poison center staff (Grade D).

Determining Triage Guidelines for Unintentional Overdoses with Calcium Channel Antagonists

BACKGROUND

Calcium channel antagonists (CCAs) are known to cause significant toxicity in overdose. Determining triage guidelines for CCAs is an important but difficult task. This study was designed to determine if an unintentional overdose of a patient's CCA could result in clinically significant cardiovascular (CV) symptoms (hypotension, bradycardia, conduction disturbances).

METHODS

Poison center records over a 3-year period were reviewed for adults ingesting at least double their prescribed dose of CCAs and who were evaluated in an emergency department (ED). Cases were reviewed for: patient age and gender, co-ingestants, CCA involved, dosage form, dose taken, usual dose, symptoms, available vital signs, and medical outcomes.

RESULTS

225 cases were identified; 161 cases met study criteria. There were 51 cases involving co-ingestants and 13 in which the usual dose was unknown. These were excluded. One hundred twenty-two patients (76%) were female and the mean age of all patients was 64 years. One hundred and four (65%) cases involved ingestions equal to double the usual dose (DD), 57 (35%) involved more than a DD. For DD cases, nine (9%) developed clinically significant CV signs or symptoms; while in cases with more than DD, eight (14%) did.

CONCLUSIONS

This retrospective review demonstrated that the toxicity of CCAs following a therapeutic overdose can be highly variable and that the dose producing a toxic effect on the cardiovascular system may be within the maximum range of therapeutic doses. This may be the result of a number of factors, including the broad range of therapeutic doses as well as the pre-existing conditions in patients taking these medications. This variability makes home management of these cases difficult and therefore, poison centers should be conservative in their evaluation of these cases.

Calcium channel blocker toxicity

Calcium channel blockers continue to be used for the management of a wide variety of adult and pediatric conditions including hypertension, angina pectoris, atrial arrhythmias, Raynaud phenomenon, and migraine headaches. With increased use comes increased potential for misuse and abuse. This article serves as a review of calcium channel blocker physiology with emphasis on presentation and management of the pediatric patient with calcium channel blocker toxicity.

Unusual ECG findings mimicking complete heart block in an unrecognised calcium antagonist overdose

We present a case of severe cardiovascular instability which required intensive care management after a myocardial infarction had been diagnosed incorrectly. Unusual ECG findings were diagnostic of calcium antagonist toxicity as the cause of the cardiovascular collapse. A discussion of the potential pitfalls in the management of patients intoxicated with these agents is undertaken. Of particular interest is the prolonged period of supportive therapy required prior to the return of an unsupported circulation. The physiological variables encountered with this type of poisoning were confirmed by the use of a PiCCO device.

Calcium Channel Blocker Toxicology

Calcium channel blockers are commonly prescribed antihypertensive medications in the United States and as such are a common presenting ingestion. The pharmacology and mechanism of action of this class of drugs will be discussed. The clinical presentation and therapeutic options will be reviewed.

Pharmacology, Pathophysiology and Management of Calcium Channel Blocker and ??-Blocker Toxicity

Calcium channel blockers (CCB) and beta-blockers (BB) account for approximately 40% of cardiovascular drug exposures reported to the American Association of Poison Centers. However, these drugs represent >65% of deaths from cardiovascular medications. Yet, caring for patients poisoned with these medications can be extremely difficult. Severely poisoned patients may have profound bradycardia and hypotension that is refractory to standard medications used for circulatory support.Calcium plays a pivotal role in cardiovascular function. The flow of calcium across cell membranes is necessary for cardiac automaticity, conduction and contraction, as well as maintenance of vascular tone. Through differing mechanisms, CCB and BB interfere with calcium fluxes across cell membranes. CCB directly block calcium flow through L-type calcium channels found in the heart, vasculature and pancreas, whereas BB decrease calcium flow by modifying the channels via second messenger systems. Interruption of calcium fluxes leads to decreased intracellular calcium producing cardiovascular dysfunction that, in the most severe situations, results in cardiovascular collapse.Although, CCB and BB have different mechanisms of action, their physiological and toxic effects are similar. However, differences exist between these drug classes and between drugs in each class. Diltiazem and especially verapamil tend to produce the most hypotension, bradycardia, conduction disturbances and deaths of the CCB. Nifedipine and other dihydropyridines are generally less lethal and tend to produce sinus tachycardia instead of bradycardia with fewer conduction disturbances.BB have a wider array of properties influencing their toxicity compared with CCB. BB possessing membrane stabilising activity are associated with the largest proportion of fatalities from BB overdose. Sotalol overdoses, in addition to bradycardia and hypotension, can cause torsade de pointes. Although BB and CCB poisoning can present in a similar fashion with hypotension and bradycardia, CCB toxicity is often associated with significant hyperglycaemia and acidosis because of complex metabolic derangements related to these medications. Despite differences, treatment of poisoning is nearly identical for BB and CCB, with some additional considerations given to specific BB. Initial management of critically ill patients consists of supporting airway, breathing and circulation. However, maintenance of adequate circulation in poisoned patients often requires a multitude of simultaneous therapies including intravenous fluids, vasopressors, calcium, glucagon, phosphodiesterase inhibitors, high-dose insulin, a relatively new therapy, and mechanical devices. This article provides a detailed review of the pharmacology, pathophysiology, clinical presentation and treatment strategies for CCB and BB overdoses.

Treatment of calcium channel blocker intoxication with insulin infusion: case report and literature review

We present a case report of successful treatment of shock induced by the calcium channel blocker (CCB) diltiazem. A 75-year-old woman took a combination of tablets, including diltiazem. Soon after arrival, she developed haemodynamic shock which persisted despite treatment with fluids, dopamine, dobutamine, norepinephrine (noradrenaline), calcium gluconate and glucagon. Haemodynamic stability was not achieved until an insulin infusion and glucose administration was started. We review the literature and the updated guidelines for the treatment of CCB intoxication, with particular emphasis on situations where insulin and glucose infusions can be live saving.