Calcium gluconate and hypertonic sodium chloride in a case of massive verapamil poisoning

Treatment for calcium channel blocker poisoning: a systematic review

CONTEXT

Calcium channel blocker poisoning is a common and sometimes life-threatening ingestion.

OBJECTIVE

To evaluate the reported effects of treatments for calcium channel blocker poisoning. The primary outcomes of interest were mortality and hemodynamic parameters. The secondary outcomes included length of stay in hospital, length of stay in intensive care unit, duration of vasopressor use, functional outcomes, and serum calcium channel blocker concentrations.

METHODS

Medline/Ovid, PubMed, EMBASE, Cochrane Library, TOXLINE, International pharmaceutical abstracts, Google Scholar, and the gray literature up to December 31, 2013 were searched without time restriction to identify all types of studies that examined effects of various treatments for calcium channel blocker poisoning for the outcomes of interest. The search strategy included the following Keywords: [calcium channel blockers OR calcium channel antagonist OR calcium channel blocking agent OR (amlodipine or bencyclane or bepridil or cinnarizine or felodipine or fendiline or flunarizine or gallopamil or isradipine or lidoflazine or mibefradil or nicardipine or nifedipine or nimodipine or nisoldipine or nitrendipine or prenylamine or verapamil or diltiazem)] AND [overdose OR medication errors OR poisoning OR intoxication OR toxicity OR adverse effect]. Two reviewers independently selected studies and a group of reviewers abstracted all relevant data using a pilot-tested form. A second group analyzed the risk of bias and overall quality using the STROBE (STrengthening the Reporting of OBservational studies in Epidemiology) checklist and the Thomas tool for observational studies, the Institute of Health Economics tool for Quality of Case Series, the ARRIVE (Animal Research: Reporting In Vivo Experiments) guidelines, and the modified NRCNA (National Research Council for the National Academies) list for animal studies. Qualitative synthesis was used to summarize the evidence. Of 15,577 citations identified in the initial search, 216 were selected for analysis, including 117 case reports. The kappa on the quality analysis tools was greater than 0.80 for all study types.

RESULTS

The only observational study in humans examined high-dose insulin and extracorporeal life support. The risk of bias across studies was high for all interventions and moderate to high for extracorporeal life support. High-dose insulin. High-dose insulin (bolus of 1 unit/kg followed by an infusion of 0.5-2.0 units/kg/h) was associated with improved hemodynamic parameters and lower mortality, at the risks of hypoglycemia and hypokalemia (low quality of evidence). Extracorporeal life support. Extracorporeal life support was associated with improved survival in patients with severe shock or cardiac arrest at the cost of limb ischemia, thrombosis, and bleeding (low quality of evidence). Calcium, dopamine, and norepinephrine. These agents improved hemodynamic parameters and survival without documented severe side effects (very low quality of evidence). 4-Aminopyridine. Use of 4-aminopyridine was associated with improved hemodynamic parameters and survival in animal studies, at the risk of seizures. Lipid emulsion therapy. Lipid emulsion was associated with improved hemodynamic parameters and survival in animal models of intravenous verapamil poisoning, but not in models of oral verapamil poisoning. Other studies. Studies on decontamination, atropine, glucagon, pacemakers, levosimendan, and plasma exchange reported variable results, and the methodologies used limit their interpretation. No trial was documented in humans poisoned with calcium channel blockers for Bay K8644, CGP 28932, digoxin, cyclodextrin, liposomes, bicarbonate, carnitine, fructose 1,6-diphosphate, PK 11195, or triiodothyronine. Case reports were only found for charcoal hemoperfusion, dialysis, intra-aortic balloon pump, Impella device and methylene blue.

CONCLUSIONS

The treatment for calcium channel blocker poisoning is supported by low-quality evidence drawn from a heterogeneous and heavily biased literature. High-dose insulin and extracorporeal life support were the interventions supported by the strongest evidence, although the evidence is of low quality.

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).

Hypertonic sodium bicarbonate is effective in the acute management of verapamil toxicity in a swine model

STUDY OBJECTIVE

This study was conducted to determine whether hypertonic sodium bicarbonate would improve the hypotension associated with severe verapamil toxicity compared with volume expansion.

METHODS

The study design used a nonblinded acute animal preparation. Twenty-four anesthetized and instrumented swine were poisoned with verapamil delivered at a rate of 1 mg/kg per hour for 10 minutes followed by incremental increases of 1 mg/kg per hour every 10 minutes until the endpoint of a mean arterial blood pressure of 45% of baseline was achieved. Animals alternately received either 4 mEq/kg of hypertonic sodium bicarbonate intravenously over 4 minutes or similar volumes of 0.6% sodium chloride in 10% mannitol (control). The main outcome parameter followed was mean arterial pressure. In addition, physiologic parameters including cardiac output, heart rate, pH, PCO (2), PO (2), plasma ionized calcium, sodium, and potassium were monitored.

RESULTS

Verapamil toxicity, as defined by a mean arterial pressure of 45% of baseline, was produced in all animals following an average verapamil infusion dose of 0.6+/-0.12 mg/kg. This dose produced an average plasma verapamil concentration of 728.1+/-155.4 microgram/L, with no significant difference between groups. Swine treated with hypertonic sodium bicarbonate experienced a significant increase in mean arterial pressure (>50%) and cardiac output (>30%) over the first 20 minutes that slowly equilibrated with the control group over the remainder of the experiment. As expected, plasma sodium concentrations were elevated significantly in the sodium bicarbonate group while plasma potassium concentrations were decreased significantly. Finally, there was a significant decrease in plasma ionized calcium concentration in the sodium bicarbonate-treated group compared with controls.

CONCLUSION

Hypertonic sodium bicarbonate reversed the hypotension and cardiac output depression of severe verapamil toxicity in a swine model.

The use of calcium salts in the prevention and management of verapamil-induced hypotension

OBJECTIVE

To review the available literature on the use of intravenous calcium salts for the prevention of hypotension associated with intravenous verapamil.

METHODS

A MEDLINE search (1966-June 1999) identified pertinent articles; references from these articles were identified to serve as additional resources.

DISCUSSION

Verapamil is effective in inhibiting atrioventricular nodal conduction, thereby controlling ventricular rate in patients with atrial fibrillation/flutter and terminating paroxysmal supraventricular tachycardia. However, hypotension may be caused by the negative inotropic and vasodilating effects of verapamil. In vitro and animal data suggest that calcium pretreatment may minimize the effects of verapamil on cardiac output and blood pressure. Case reports suggest that intravenous calcium may be useful for both prevention and reversal of the hemodynamic effects of verapamil. A number of small clinical trials have been performed, suggesting that calcium administered prior to intravenous verapamil results in a decreased incidence of hypotension. The most common adverse effect of intravenous calcium is flushing.

CONCLUSIONS

Calcium pretreatment prior to intravenous calcium-channel blocker administration should be considered in patients in whom further reductions in blood pressure may precipitate hypoperfusion or worsen underlying cardiovascular status. A dose of calcium gluconate 1 g (ionized calcium 90 mg) administered over three minutes is recommended for preventing or lessening the hypotensive effect of verapamil without affecting the antiarrhythmic effects of verapamil.

Delayed hypotension after overdose of sustained release verapamil

We present the case of a 25-year-old woman who, although normotensive on presentation, had a severe hypotensive episode more than 12 h after initial ingestion of sustained release verapamil. Management of asymptomatic patients who have overdosed on a sustained release preparation of a calcium channel blocker is discussed.

Noncardiogenic pulmonary edema complicating massive verapamil overdose

Noncardiogenic pulmonary edema has not been (to our knowledge) previously reported associated with a verapamil overdose. We describe a 27-year-old woman who developed this complication after an overdose of 15, 120-mg verapamil tablets (total of 1,800 mg). This report illustrates the possibility of serious pulmonary embarrassment in the course of a verapamil overdose and the need to avoid excessive crystalloid administration during the hypotensive period.

Verapamil intoxication: a literature review of overdoses and discussion of therapeutic options

Calcium channel antagonists can be quite toxic. In the management of poisoning, early recognition is critical. Calcium channel antagonists are frequently prescribed, and the potential for serious morbidity and mortality with overdosage is significant. Ingestion of these agents should be suspected in any patient who presents in an overdose situation with unexplained hypotension and conduction abnormalities. The potential for toxicity should be noted in patients with underlying hepatic or renal dysfunction who are receiving therapeutic doses. Because there is no specific antidote, decontamination of the gastrointestinal tract is crucial. Intravenous calcium should be administered to symptomatic patients because it is relatively innocuous and may be beneficial. Volume expansion should be the initial approach to hypotension unrelated to bradycardia. Patients who have had a verapamil overdose should be observed in intensive care units where Swan-Ganz catheterization and ventricular pacing are routinely available. The choice of sympathomimetic agents for treatment remains controversial. According to the published literature, isoproterenol, epinephrine, and norepinephrine may be more effective in improving bradycardia and the resultant hypotension than dopamine. However, none of these agents is universally effective. A more logical approach may be to improve cardiac output with agents like amrinone. Bay K 8644 and 4-aminopyridine show promise as potential antidotes but at present are still experimental.

Case report: sustained-release verapamil overdose causing stroke: an unusual complication

A 47-year-old woman ingested 7.2 gm of sustained-release verapamil. She developed hypotension, idioventricular rhythm, mild acidosis, mild hyperglycemia, and aspiration pneumonia that required antibiotics and mechanical ventilatory support. In addition, she had a stroke, which resulted from left cerebral hemispheric damage, an unusual complication. Stroke is reported only once in the literature. Special problems related to slow release medication and the need to be aware of them are discussed.

Verapamil overdose: case report and review of the literature

OBJECTIVE

To report the presentation and controversies regarding therapy of an 18-year-old man following a life-threatening ingestion of verapamil.

CASE SUMMARY

An 18-year-old man ingested large quantities of dipyridamole, trimethoprim/sulfamethoxazole, amoxicillin, and verapamil. He presented to an outlying hospital and was initially conscious. Soon thereafter, the patient had a seizure; he required intubation, developed cardiac conduction abnormalities, and became hypotensive. The patient required pharmacologic pressors and a pacemaker for transfer to our institution. At our institution, vigorous fluid resuscitation, cardiac pacing, and careful attention to acid/base and electrolyte management provided the basis of therapy. The patient recovered without deficit and was discharged from the intensive care unit five days later.

DISCUSSION

Current controversies regarding the management of verapamil overdose are reviewed. Removal of the drug by gastric lavage is a mainstay of therapy. Administration of syrup of ipecac is contraindicated. Although specific recommendations for calcium dosing in the overdose situation have not been rigorously studied, maintenance of a normal serum ionized calcium concentration is suggested. An exogenous catecholamine, rather than dopamine, may be the drug of choice for treating hypotension. Cardiopulmonary bypass provides a method for drug removal in cases of severe toxicity; however, this invasive method requires further study. Management of fluid/electrolyte, acid/base, and ventilation abnormalities is required to treat large ingestions of verapamil. Treatment guidelines for critical care clinicians are provided.

Refractory cardiogenic shock and complete heart block after unsuspected verapamil-SR and atenolol overdose

A 57-year-old female presented with complete heart block and then developed refractory hypotension despite temporary pacing. Moderate left ventricular dysfunction with focal wall motion abnormalities, as well as severe hypoxemia, were demonstrated. However, neither significant coronary disease nor evidence for pulmonary embolus or other lung disease could be determined. Hemodynamic stabilization was achieved with the use of an intra-aortic balloon pump and multiple high-dose pressor agents. A retrospective diagnosis of toxic verapamil-SR and atenolol ingestion was confirmed, and the patient gradually recovered. The relevant literature is reviewed and various treatment approaches are discussed.

Effects of calcium channel blocker overdose-induced toxicity in the conscious dog

STUDY OBJECTIVE

To evaluate the effects of nifedipine, diltiazem, and verapamil overdose on systemic hemodynamics and blood flows to the coronary, superior mesenteric, renal, and iliac arteries in the unanesthetized dog.

DESIGN

Nonblinded, controlled animal study.

SETTING

Research laboratory of a large pharmaceutical company.

TYPE OF PARTICIPANTS

Nineteen healthy mongrel dogs obtained from a commercial supplier.

INTERVENTIONS

Under general anesthesia, flow probes were placed about the ascending aorta, circumflex coronary, superior mesenteric, renal, and iliac arteries; a micromanometer was implanted into the tip of the left ventricle; and a catheter was inserted into the descending aorta. Experiments were performed after a recovery period of at least two weeks.

MEASUREMENTS AND MAIN RESULTS

Arterial blood pressure, heart rate, cardiac output, left ventricular pressure, and regional blood flows were measured prior to drug administration, and after 0.03, 0.1, 0.3, 1.0, and 3.0 mg/kg IV administration of the study drugs. Dogs receiving diltiazem or verapamil also received a dose of 10.0 mg/kg. When the blood pressure had been reduced from baseline by 30%, 1.43 mg/kg nifedipine IV (six dogs) decreased total peripheral resistance by 51%, increased cardiac output by 35%, and increased heart rate by 132%. Coronary blood flow and iliac blood flow increased 93% and 45%, respectively, but mesenteric blood flow and renal blood flow were not significantly altered. Diltiazem (eight) and verapamil (seven) at equivasodepressor doses (1.43 to 4.43 mg/kg) caused less peripheral vasodilation and reflex tachycardia. At severely toxic levels when arterial blood pressure fell by 50%, all three drugs decreased cardiac output. Nifedipine still increased heart rate. Diltiazem and verapamil caused high-grade atrioventricular block, resulting in bradycardia. All three drugs caused a redistribution of cardiac output favoring the coronary bed over the other beds.

CONCLUSIONS

In the conscious dog, calcium channel blocker-induced hypotension at the moderate level is associated with disparate effects on systemic hemodynamics, probably resulting from differential reflex sympathetic activation. However, at a more severe level, their toxic effects are similar and manifested predominantly by their actions on the slow calcium channel.

Diltiazem overdose: case report and review

We present a case of diltiazem overdose in which the patient ingested 4.2 grams in an apparent suicide attempt. He arrived in the emergency department two hours postingestion with a blood pressure of 60/40 torr and a heart rate of 62 beats/min in a junctional rhythm. Intervention included activated charcoal, gastric lavage, intravenous fluids, calcium (both chloride and gluconate), dopamine, and atropine with improvement in vital signs. Diltiazem levels were obtained and half-life calculated. This ingestion is one of the largest reported in the literature and is remarkable in that the patient recovered without pacing or other extraordinary measures. All eight previously published cases of diltiazem overdose, including all unpublished reports to the manufacturer, are reviewed and their management strategies examined. Successful treatment in which recovery has occurred in less than 48 hours, includes pressors, calcium, glucagon, pacing, and charcoal hemoperfusion. A strategy for emergency physicians to use when approaching this problem is suggested from the review.

Management of massive verapamil overdose

A 53-year-old man presented to hospital after an overdose (4.8 g) of verapamil. He developed profound bradycardia and hypotension, requiring treatment with calcium salts, dobutamine, isoprenaline and cardiac pacing. As calcium channel blockers are more widely used, self-poisoning will become more common. The effects, although serious, are self-limiting and recovery within 48 hours is the rule provided adequate support is given.

Antagonistic effects of epinephrine, glucagon and methylatropine but not calcium chloride against atrio-ventricular conduction disturbances produced by high doses of diltiazem, in conscious dogs

Conscious dogs (n = 6) with chronically implanted electrocardiogram electrodes and arterial and venous catheters were infused with a large dose of diltiazem (1 mg/dog per min i.v. over 60 min) to evoke hypotension and atrioventricular disturbances (AVII and AVIII blocks) which lasted for several hours. These effects are also observed in humans after accidentally or intentionally taking overdoses of diltiazem and particularly verapamil. In the intoxicated dog, administration of methylatropine (50 micrograms/kg per min i.v. over 10 min), epinephrine (0.2 and 0.4 microgram/kg per min i.v. over 60 min) and glucagon (2 micrograms/kg/min i.v. over 15 min) but not CaCl2 (3 mg/kg/min i.v. over 15 min) abolished almost entirely the AVII and AVIII blocks produced by diltiazem and re-established a normal sinus rhythm. However, these treatments failed to normalize AV conduction, and did not modify the moderate hypotensive effects of diltiazem. These findings support available clinical observations that beta-adrenoceptors agonists, glucagon and atropine rather than calcium salts are beneficial for the successful treatment of cardiovascular toxicity associated with the intake of supratherapeutic doses of diltiazem or verapamil.

Calcium channel blocker toxicity

A retrospective review was conducted of all patients who were reported to a regional poison control center after "overdose" of a calcium channel blocker during a two-year period (1987 and 1988). An analysis of 91 patient cases is presented after excluding allergic reactions, cases involving coingestants, and patients lost to follow-up. Patients who developed any symptoms after ingestion were defined as manifesting toxicity. There were 38 cases of verapamil ingestion with toxicity developing in 18 patients. The mean nontoxic dose was 320 mg, whereas the mean toxic ingestion was 3.2 g. Nine patients became hypotensive, 13 developed conduction system abnormalities (sinus node suppression, atrioventricular nodal block, or bundle branch block), and 11 manifested arrhythmias. Ten developed neurological symptoms. There were 31 cases of nifedipine ingestion with toxicity developing in seven patients. The mean nontoxic dose was 19 mg, while the mean toxic ingestion was 340 mg. Four patients were hypotensive, only one developed cardiac conduction abnormalities, and four developed arrhythmias. Three had neurological symptoms. There were 24 cases of diltiazem ingestion with only minor toxicity developing in four patients. There was no statistically significant difference in the frequency of hypotension, arrhythmias, or neurological symptoms in patients who overdosed with verapamil as compared with nifedipine (by Fisher's exact test). However, conduction system abnormalities were more common with verapamil ingestion (P less than .05). Toxic manifestations after diltiazem over-dose were uncommon in our study. Eighteen of the 29 patients who developed toxicity required treatment in excess of gastrointestinal decontamination. Calcium was administered to 14 patients and was helpful in five.

Massive verapamil ingestion: a report of two cases and a review of the literature

This report describes two patients who were victims of massive verapamil ingestion and then reviews the available literature. Because verapamil blocks the slow calcium channels of the heart and blood vessels, the use of calcium as a treatment would be logical. In the two cases reported here, calcium was only transiently effective in maintaining cardiac output and blood pressure. Several other agents were then used and most were ineffective. This is similar to experience reported in the literature that suggests that no single agent is capable of reversing verapamil's negative inotropic, dromotropic, chronotropic, and vascular smooth muscle effects.

Extracorporeal bypass for the treatment of verapamil poisoning

A 25-month-old boy ingested six sustained-release verapamil tablets, each containing 240 mg of drug. Charcoal and cathartic were given but were never passed per rectum. Third-degree heart block, hypotension, and hypocalcemia were only transiently responsive to calcium infusions, inotropic agents, and epicardial pacing. Cardiopulmonary arrest with electromechanical dissociation ensued. Standard cardiopulmonary bypass was used to allow sufficient time for liver detoxication. Serum levels of verapamil fell during the bypass procedure, and the patient's cardiac status improved. However, continued absorption of drug after bypass resulted in a level of 4 mg/L, unresponsive circulatory failure, and death. Early, aggressive gut decontamination and the potential value of cardiopulmonary bypass procedures in poisoning that lead to cardiac depression are emphasized.

Cerebral infarction associated with oral verapamil overdose

Verapamil is a widely used calcium channel blocker. Side effects with oral use are usually mild, however, major hemodynamic complications and death can occur if the drug is given in overdose. We describe a case of cerebral infarction associated with attempted suicide with verapamil overdose, the first reported to our knowledge.

Management of acute severe verapamil intoxication

A 41-year-old man ingested 6.8 g of verapamil in a suicide attempt. The patient was severely hypotensive, oliguric, and developed a variety of dysrhythmias. He was also hyperglycemic. The patient was successfully resuscitated with intravenous normal saline, calcium chloride, dopamine, and norepinephrine. A review of the manifestations of verapamil intoxication and suggestions for management are outlined.

[Sinusal dysfunction secondary to the ingestion of diltiazem, cured by the administration of intravenous calcium]

An elderly patient, receiving long-term oral diltiazem at the usual dosage, presented a sudden attack of junctional bradycardia at 35 b X min-1; this was badly tolerated by the patient. The diltiazem blood level was normal. After recovery, nodal investigations were also normal. The treatment of this accident due to a calcium-blocker is stressed: the intravenous injection of a calcium salt only was sufficient, with a return to near-normal sinus function, so avoiding the necessity of pacing.

Massive diltiazem overdose

A 74-year-old man presented with bradycardia, diaphoresis, mental confusion, and slurred speech. He developed asystole and was managed successfully with temporary emergency transvenous pacing and support of ventilation and blood pressure. He later was found to have ingested approximately 1,500 mg diltiazem, apparently as the result of an error created by his blindness and chronic confusion.

Nifedipine overdose

A 59-year-old man ingested 900 mg of nifedipine. Profound hypotension, sinus and atrioventricular node dysfunction, and hyperglycemia resulted. The patient's condition responded favorably to aggressive treatment with intravenous fluids, calcium, and dopamine. Similar effects and response to therapy have been reported in 17 cases of verapamil overdose and are briefly summarized. The effects of nifedipine overdose are discussed, and preliminary recommendations about its management are offered. With increasing use of nifedipine and other calcium channel blockers, more incidents of overdose can be expected.

Should calcium be used in cardiac arrest?

Calcium salts have been recommended for and used in the treatment of various forms of cardiac arrest for many years. Although calcium plays a major role in excitation-contraction coupling, it can have a deleterious effect in some processes of cellular injury. Clinical trials suggest that calcium salts are not effective in ventricular fibrillation and asystole, but that some patients with electromechanical dissociation may have a favorable hemodynamic response. Because of the potential risks of calcium salts, their use should be limited to specific subsets of patients with cardiac arrest.

Treatment of verapamil toxicity in intact dogs

The treatment of verapamil toxicity was examined in lightly sedated dogs. Verapamil, administered as a bolus (0.72 mg/kg) followed by a continuous infusion (0.11 mg/kg per min), decreased cardiac output (CO) from 3.1 +/- 0.1 to 1.7 +/- 0.1 liter/min (P less than 0.001), heart rate (HR) from 85 +/- 4 to 57 +/- 3 beats/min (P less than 0.001), left ventricular derivative of pressure with respect to time (LV dP/dt) from 2,085 +/- 828 to 783 +/- 78 mm Hg/s (P less than 0.001), mean aortic pressure (AO) from 77 +/- 4 to 38 +/- 2 mm Hg (P less than 0.001) and stroke volume from 39 +/- 3 to 28 +/- 2 ml/beat (P less than 0.01). In verapamil-toxic animals isoproterenol increased HR, CO, LV dP/dt, and AO; calcium chloride increased LV dP/dt and AO; norepinephrine, epinephrine, and dopamine increased CO, AO, and LV dP/dt, atropine increased HR, CO, and AO. Phenylephrine (13-55 micrograms/kg per min) produced no changes except a small increase in AO while very high dose phenylephrine (300 micrograms/kg per min) increased AO, CO, and LV dP/dt. 4-Aminopyridine (4-AP) increased HR, CO, LV dP/dt, and AO. When administered prior to verapamil, 4-AP prevented the development of verapamil toxicity as shown by the significantly higher AO (P less than 0.001), CO (P less than 0.01), and LV dP/dt (P less than 0.01) when 4-AP followed by verapamil was compared to verapamil alone. In conclusion, there does not appear to be a single specific therapy for verapamil toxicity, however it can be partially corrected by presently available pharmacologic therapy and 4-AP.

Ionized calcium during CPR in the canine model

The purpose of our study was to determine ionized calcium levels during cardiopulmonary resuscitation (CPR). Following placement of ascending aortic catheters in 15 adult mongrel dogs, ventricular fibrillation was induced electrically. After five minutes without therapy, mechanical external CPR was instituted. Animals received either standard CPR (S-CPR, n = 8) or simultaneous compression and ventilation CPR (SCV-CPR, n = 7) for 30 minutes. Ionized calcium levels were obtained prior to fibrillation and every five minutes during CPR. Mean ionized calcium levels during CPR (1.27 +/- 0.06 mmol/L) did not differ significantly from prearrest levels (1.27 +/- 0.07 mmol/L) at any point during CPR. This was true when the dogs were analyzed together (P = 0.1293) and when the animals receiving S-CPR (P = 0.4465) and SCV-CPR (P = 0.5470) were analyzed by groups. Defibrillation was attempted in all animals and resulted in electromechanical dissociation in three. None of these dogs was hypocalcemic either prior to arrest or during CPR, and none developed an effective rhythm with the administration of calcium. Furthermore, three of the four animals receiving calcium developed markedly elevated ionized calcium levels. Hypocalcemia apparently does not occur during CPR. The beneficial effect of calcium in reported cases cannot be explained routinely by correction of hypocalcemia. Further studies are needed to define the role of calcium administration, if any, in CPR.

Cardiogenic shock associated with calcium-channel and beta blockers: reversal with intravenous calcium chloride

Two cases in which oral ingestion of beta blocker and slow calcium-channel blocker was associated with profound hypotension and bradycardia are reported, including one case in which serum levels of both drugs were documented in the normal range at a time of severe clinical toxicity. Though unresponsive to usual therapeutic interventions, both patients showed an immediate and dramatic response to intravenous calcium chloride. It is recommended that intravenous calcium chloride be considered in any patient using routine doses of these two agents who presents with hypotension and/or bradycardia.

Hypotension and sinus arrest with nifedipine in pulmonary hypertension

An adverse reaction to the acute administration of sublingual nifedipine is reported. Subsequent reversal was by intravenous administration of calcium chloride.

Calcium channel blockers in emergency medicine

Diltiazem, nifedipine, and verapamil inhibit calcium entry into cells via different mechanisms with different pharmacologies. They display different relative effects on different cardiovascular functions, a complex interplay of direct actions and adrenergic reflexes. Peripheral arterial vasorelaxation causes adrenergic reflex activity which opposes their direct negative chronotropic, dromotropic, inotropic, and hypotensive actions. Verapamil's most potent activity is electrophysiologic, and nifedipine's effects are hemodynamic; diltiazem acts like a less-potent combination of verapamil and nifedipine. All three drugs are efficacious in angina. These three drugs may not be interchangeable in all patients, but individualization of therapy is possible. Future indications for calcium channel blocker therapy may include hypertrophic cardiomyopathy, cerebral vasospasm, migraine headaches, pulmonary hypertension, asthma, esophageal spasm, intestinal ischemia, Raynaud's phenomenon, dysmenorrhea, and premature labor.

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.

Use of calcium in electromechanical dissociation

Calcium is recommended by American Heart Association standards for the resuscitation of patients with electromechanical dissociation (EMD). Until recently, only anecdotal case reports were offered to support this recommendation. Recent studies examining the question of whether calcium is useful in resuscitating hearts in EMD are reviewed.

Management of cardiac drug overdose

Although overdoses from cardiac drugs are uncommon, these are compounds with narrow therapeutic indices and they may give rise to serious acute toxicity from accidental, deliberate or even iatrogenic overdosage. Through the National Poisons Information Service for England and the Poisons Unit laboratory, we monitor reports of serious toxicity from this group of drugs and use the information gained to assess our recommendations for treatment. This article reviews the toxicity and the management of overdosage with digoxin and representative drugs from each class of anti-arrhythmic drugs. From these observations, a general plan of management applicable to all cardiac drugs is proposed and its is suggested that this form of monitoring should be continued.

Clinical features and management of nifedipine overdosage in a patient with renal insufficiency

Overdosage with 280 mg nifedipine, verified by plasma nifedipine levels, led in a 23-year-old female patient with advanced renal insufficiency to features of marked vasodilation. Despite profound hypotension and preexisting anemia, tissue perfusion was adequately maintained. Neither cardiac conductance disturbances nor myocardial depression occurred. There was no evidence for major organ or organ system toxicity. The patient was successfully treated with intravenous calcium. Hemoperfusion did not significantly influence the clinical course. The recovery was uneventful. No late sequelae were observed.

Profound hyperglycemia and metabolic acidosis after verapamil overdose

Verapamil, a potent calcium antagonist, possesses varied systemic effects, including smooth muscle relaxation leading to both peripheral and coronary artery vasodilation, slowed atrioventricular nodal conduction and decreased insulin release from the pancreatic B cells. Reports concerning the effects of acute intoxication with verapamil are scarce. A case is presented of a 22 year old woman who developed profound hyperglycemia and metabolic acidosis after the inadvertent overdose of thirty 80 mg tablets (2,400 mg) of verapamil. This case illustrates the need for physicians to be aware of verapamil's inhibitory effects on insulin release and to exercise special care when prescribing verapamil in patients with preexisting diabetes mellitus.

The use of calcium in cardiac resuscitation

All records of cardiac arrest patients presenting to the Tampa EMS system for the 24-month period of January, 1980, through December, 1982, were reviewed. Paramedics were given direct orders or standing orders to administer calcium intravenously or intracardiac in patients in ventricular fibrillation, asystole, or electromechanical dissociation. Of the 480 patients receiving calcium for the above conditions, only patients with electromechanical dissociation responded to calcium. Twenty-seven EMD patients responded positively with the immediate return of blood pressure and pulse. Fourteen of these patients arrived at the emergency department with stable vital signs; there were three long-term survivors. Adverse rhythm or rate changes were not noted following calcium use, and arrhythmias associated with digitalis excess were not seen in a small group of patients taking digoxin. Although long-term survivors are limited in this group of patients, positive hemodynamic responses were seen following calcium chloride administration in 10% of EMD patients and not at all in patients with asystole or ventricular fibrillation.

Acute verapamil poisoning: successful treatment with epinephrine

Acute intoxication with verapamil (2400 mg) induced A-V dissociation and circulatory failure in a 38-year-old woman with no previous cardiac disease. Resumption of A-V conduction was observed after administration of orciprenalin, calcium gluconate, and dopamine, with no effect on blood pressure. Epinephrine infusion finally restored satisfactory blood pressure level and allowed a favorable outcome.