Adverse effects of calcium administration. Report of two cases

"Feeling the Blues": A Case of Calcium Channel Blocker Overdose Managed With Methylene Blue

Amlodipine is a dihydropyridine calcium channel blocker (CCB) commonly used to treat hypertension. In the United States, approximately 9,500 cases of CCB intoxication due to deliberate or inadvertent overdose were reported to poison centers in 2002. We present a case of a patient who presented with CCB overdose complicated by acute respiratory distress syndrome (ARDS) and recalcitrant shock all of which resolved with methylene blue therapy. We present a case of a 56-year-old African American woman who presented to the emergency department (ED) after intentional ingestion of large amounts of multiple pills likely consisting of cyclobenzaprine, amlodipine, losartan, and ibuprofen following an argument with her boyfriend. Treatment included insulin drip, 10% dextrose, and norepinephrine drip which was titrated up. First insulin drip and 10% dextrose were titrated up; however, vasopressor-resistant hypotension persisted, and the decision was made to administer methylene blue. Over 9,500 cases of CCB toxicity were reported to poison centers in the US in 2002. Although no definitive treatment is outlined, first-line therapy consists of IV calcium, high-dose insulin, and vasopressor support with either norepinephrine or epinephrine. Traditionally, methylene blue is used for methemoglobinemia and in cardiothoracic ICUs for post coronary artery bypass vasoplegia. It acts by selectively inhibiting nitric oxide-activated cyclic guanylate cyclase leading to decreased vasodilation of arteriolar smooth muscles improving vascular tone and systemic vascular resistance. In severe amlodipine overdose, experimental models demonstrate methylene blue improves HR and mean arterial pressure (MAP), improving survival rate. With few adverse side effects (green-tinged discoloration of urine, saliva, tears, and bodily fluids), methylene blue should be explored and implemented in the treatment of CCB overdose with refractory hypotension and ARDS.

Safety of calcitonin stimulation tests with calcium

INTRODUCTION

Medullary thyroid carcinoma (MTC) is an aggressive form of thyroid cancer. Early detection is essential because only complete resection of the thyroid tumor and any local metastases can cure MTC. Calcitonin (CT) is a marker used for diagnosis of MTC. In controversial cases of slightly elevated CT levels, stimulation tests have shown their utility, but their safety should also be taken into account.

OBJECTIVE

Our aim is to present our own experience regarding the safety of CT stimulating tests.

MATERIALS AND METHODS

We applied a specific protocol of calcium stimulation test in 176 patients after informed consent (115 women with a median age of 46 years, range 21-79; 61 men with a median age of 54 years, range 22-78). We recorded the side effects and a further analysis was performed.

RESULTS

The most frequent side effects noted were hot flashes in 159 out of 176 patients (90.34%), followed by dysgeusia (32/176) and bradycardia (10/176). Severe bradycardia was reported in only one patient (0.568%), which was rapidly reversible. There was no correlation between patients' age, weight, height, body mass index, basal CT or peak stimulated CT, and grade of severity, but men were more likely to develop cardiovascular side effects than women, namely, bradycardia, tachycardia, ventricular or atrial extrasystoles, hypertension, hypotension, or angina (p = 0.024), with an odds ratio of 2.94 (CI: 1.11-7.76). We recommend thyroid surgery in all women with sCT above 285 pg/ml.

CONCLUSION

The calcium stimulation test is well tolerated, with few adverse reactions. The test should be performed with appropriate precautions (i.e., ECG monitoring during and after the test) to minimize the possibility of a serious event.

Prophylactic administration of oral calcium carbonate during plateletpheresis: A bicentric prospective study

BACKGROUND:

Administration of anticoagulant citrate and dextrose (ACD-A) chelates ionized calcium in blood and causes hypocalcemia in plateletpheresis donors. The aim of the study was to observe the effects of oral calcium (Ca) supplementation during plateletpheresis on various parameters related to calcium metabolism.

MATERIALS AND METHODS:

This study was performed between January 2014 and December 2014 on 200 plateletpheresis donors. They were divided into two groups. In group A donors (n=100), no prophylactic oral calcium supplementation was given. In group B (n=100) donors, 2000 mg of calcium was given one hour before the start of the procedure, 500 mg was given at the start of the procedure and 500 mg calcium was given just before the end of procedure. Biochemical parameters like serum total calcium (T Ca), serum total magnesium (T Mg) and ionized calcium level (iCa) were measured before and after the procedure. Relative risk of citrate toxicity was measured between the two groups.

RESULTS:

There was a significant fall in total calcium (pre 9.02 mg/dl, post 8.23 mg/dl,), ionized calcium level (pre 1.14 mmol/L, post 0.91 mmol/L) and total magnesium (pre 1.92 mg/dl, post 1.79 mg/dl) amongst the donors who did not receive prophylactic calcium supplementation. Despite calcium intake, in prophylactic calcium intake group, we did observe a significant drop in total magnesium (pre 2.04 mg/dl, post 1.94 mg/dl) and ionized calcium level (pre 1.25 mmol/L, post 1.12 mmol/L, p<0.01). We did observe a drop in total calcium level, however, this observation was not statistically significant. The risk (RR=5.44) of citrate toxicity was higher among group A donors.

CONCLUSION:

Prophylactic oral calcium carbonate supplementation would help in to reduce the risk of citrate toxicity. Therefore, we suggest for prophylactic oral administration of 3000 mg elemental calcium carbonate in three divided doses to make PP procedures uneventful.

Anticoagulation techniques in apheresis: from heparin to citrate and beyond

Anticoagulation is essential for maintaining the fluidity of extravascular blood on the apheresis circuit. Although both citrate and heparin are used as an anticoagulant during apheresis, citrate is preferred for the majority of exchange procedures because of its safety and effectiveness. Complications of citrate are primarily due to physiologic effects of hypocalcemia. Symptoms of hypocalcemia and other citrate-induced metabolic abnormalities affect neuromuscular and cardiac function and range in severity from mild dysesthesias (most common) to tetany, seizures, and cardiac arrhythmias. Oral or intravenous calcium supplementation is advised for decreased ionized calcium levels and/or symptomatic management of hypocalcemia. Heparin-based anticoagulation is limited to certain apheresis procedures (membrane-based plasma exchange, LDL apheresis, or photopheresis) or is used in combination with citrate to reduce citrate load. While effective, heparin anticoagulation is associated with an increased frequency of bleeding complications and heparin-induced thrombocytopenia. J. Clin. Apheresis 2012. © 2012 Wiley Periodicals, Inc.

Ionized calcium concentration and outcome in critical illness

OBJECTIVE

To assess the association of abnormalities of ionized calcium levels with mortality in a heterogeneous cohort of critically ill patients.

DESIGN

Retrospective, combined clinical and biochemical study.

SETTING

Four combined medical/surgical intensive care units.

PATIENTS

Cohort of 7,024 adult critically ill patients.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We studied 177,578 ionized calcium measurements, from 7024 patients, with a mean value of 1.11 mmol/L (ionized calcium measured every 4.5 hrs on average). The unadjusted lowest and highest ionized calcium reported during intensive care unit stay were significantly different between intensive care unit survivors and nonsurvivors (p < .001). If hypocalcemia occurred at least once during the intensive care unit stay, the probability of intensive care unit mortality increased by 46%, 108%, and 150% for ionized calcium levels <1.15, 0.90, and 0.80 mmol/L, respectively. If hypercalcemia occurred at least once during the intensive care unit stay, the probability of intensive care unit mortality increased by 100%, 162%, and 190% for ionized calcium levels >1.25, 1.35, and 1.45 mmol/L, respectively. Similar trends were seen for hospital mortality. However, from multivariate logistic regression analysis, only an ionized calcium <0.8 mmol/L or an ionized calcium >1.4 mmol/L were independently associated with intensive care unit and hospital mortality.

CONCLUSIONS

Within a broad range of values, ionized calcium concentration has no independent association with hospital or intensive care unit mortality. Only extreme abnormalities of ionized calcium concentrations are independent predictors of mortality.

Ocular and systemic safety evaluation of calcium formate as a dietary supplement

PURPOSE

The objective of this study was to perform a preliminary evaluation of the ocular and systemic safety of calcium formate, a dietary calcium supplement for prevention and management of osteoporosis. Although formate is an endogenous product of metabolism, high concentrations are associated with toxicity during methanol overdose.

METHODS

In this prospective clinical trial, 12 healthy women ingested calcium formate (1,300 mg) three times a day for 14 days. Study evaluations included physical and ocular examination, extensive laboratory testing, serum calcium and formate levels, Early Treatment Diabetic Retinopathy Study (ETDRS) visual acuity, color vision, visual fields, visual evoked potential (VEP), and full-field, pattern, and multifocal electroretinograms (MERG).

RESULTS

The mean baseline serum level of formate was 0.572 +/- 0.06 mM. Peak serum levels and final serum formate did not differ significantly from baseline. The final concentration was 0.582 +/- 0.091 mM. Accumulation of serum formate did not occur. There was also no evidence of toxicity with calcium formate ingestion. All examinations and tests remained normal, including optic nerve and retinal function. Three subjects had mild transient symptoms attributable to any calcium formulation.

CONCLUSIONS

Calcium formate is highly bioavailable and well-tolerated. Serum formate remained at basal levels and did not accumulate with repeated dosing. Systemic and ocular safety was demonstrated by objective testing. Given its high oral bioavailability, calcium formate may be a good choice for calcium supplementation in the prevention and management of osteoporosis. Further study will be needed to evaluate its long-term safety in a larger group of subjects representing more varied age, health, dietary, and nutritional status.

Management of beta-adrenergic blocker and calcium channel antagonist toxicity

State-of-the-art therapy for beta-adrenergic receptor blocker and calcium channel antagonist toxicity is reviewed in the light of new insights into drug-induced shock. A brief discussion of pathophysiology, including cardiac, hemodynamic, and metabolic effects of cardiac drug toxicity, provides a foundation for understanding the basis of therapy. The major focus of this review is a critical evaluation of antidotal use of calcium, glucagon, catecholamines, insulin-euglycemia, and other novel therapies based on investigational studies and cumulative clinical experience.

Treatment of moderate to severe acute hypocalcemia in critically ill trauma patients

BACKGROUND

Our recent data indicate that 21% of critically ill, adult, multiple-trauma patients receiving specialized nutrition support experience hypocalcemia. However, evidence-based methods for the treatment of moderate to severe acute hypocalcemia (ionized calcium concentration [iCa] <1 mmol/L) are lacking.

METHODS

The efficacy of an infusion of 4 g of calcium gluconate was evaluated in 20 critically ill, adult, multiple-trauma patients with moderate to severe hypocalcemia (iCa <1 mmol/L). The calcium gluconate was infused at a rate of 1 g/h in a small volume admixture. A serum iCa determination was obtained on the following day.

RESULTS

Calcium gluconate infusion significantly increased serum iCa from 0.90 +/- 0.08 mmol/L to 1.16 +/- 0.11 mmol/L (p < .001) on the following day. This dosage regimen was successful for achieving a serum iCa >1 mmol/L for 19 of 20 (95%) hypocalcemic patients and achieved a concentration >1.12 mmol/L in 14 (70%) of the patients. Two patients developed mild hypercalcemia (iCa of 1.34 mmol/L and 1.38 mmol/L) postinfusion.

CONCLUSIONS

A short-term infusion of 4 g of intravenous (IV) calcium gluconate for the treatment of moderate to severe hypocalcemia appears to be a promising regimen for critically ill, adult, multiple-trauma patients.

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.

Controlled study of citrate effects and response to i.v. calcium administration during allogeneic peripheral blood progenitor cell donation

BACKGROUND

Leukapheresis procedures are generally performed at citrate anticoagulation rates extrapolated from shorter plateletpheresis procedures. However, neither the metabolic effects nor the management of associated symptoms have been critically evaluated during leukapheresis in healthy donors.

STUDY DESIGN AND METHODS

Symptom assessments (n = 315) and laboratory analyses (n = 49) were performed during 244 procedures performed with and 71 without prophylactic calcium (Ca) chloride or Ca gluconate given at a dose linked to the citrate infusion rate (1.0-2.2 mg/kg/min).

RESULTS

During leukapheresis of 12 to 25 L processed, ionized Ca and ionized magnesium (Mg) decreased as much as 35 and 56 percent, respectively, each exhibiting a tight negative correlation with marked increases in serum citrate levels. Significant increases in urinary Ca and Mg excretion accompanied the renal excretion of a large citrate load. Serum divalent cation levels remained depressed 24 hours after leukapheresis. Symptoms were more frequent in donors who were women, had low initial total Mg levels, and underwent procedures in which larger volumes were processed at higher citrate infusion rates. Ca infusions reduced clinically significant paresthesias by 96 percent and also attenuated decreases in serum potassium. Ca chloride maintained higher Ca levels than Ca gluconate.

CONCLUSIONS

Prophylactic Ca infusions safely attenuate the marked metabolic effects of citrate administration and promote faster, more comfortable, leukapheresis procedures.

Hypocalcemia: a pervasive metabolic abnormality in the critically ill

Hypocalcemia has been reported in critically ill patients, most commonly in association with sepsis syndrome. However, the severity and incidence of hypocalcemia in nonseptic but critically ill patients has not been well defined. Therefore, the goal of this study was to identify and compare the frequency and degree of hypocalcemia in critically ill patients with differing underlying illnesses (those admitted to medical, surgical, trauma, neurosurgical, burn, respiratory, and coronary intensive care units [ICUs]; group A; n = 99). Results were compared with the frequency and degree of hypocalcemia in non-critically ill ICU patients (initially admitted to an ICU but discharged within 48 hours; group B; n = 50) or hospitalized non-ICU patients (group C; n = 50). Incidences of hypocalcemia (ionized calcium [Ca] < 1.16 mmol/L [less than normal]) were 88%, 66%, and 26% for groups A, B, and C, respectively (P: < 0.001). In group A, the frequency of hypocalcemia did not depend on the ICU setting or presence of sepsis. However, the occurrence of hypocalcemia correlated with both Acute Physiology and Chronic Health Evaluation II score (r = -0.39; P: < 0.001) and patient mortality (eg, hazard ratio for death, 1.65 for Ca decrements of 0.1 mmol/L; P: < 0.002). Hypomagnesemia, number of blood transfusions, and presence of acute renal failure were each associated with depressed Ca levels. A weak association (r = -0.12; P: = 0.09) was noted between serum Ca level and QT interval. Clinical concern stemming from hypocalcemia was underscored by the substantial use of intravenous (IV) Ca therapy ( approximately 2 to 3 g IV). We conclude that hypocalcemia is extremely common in hospitalized patients (up to 88%) and correlates with severity of illness, but not with a specific illness per se. Whether it directly impacts patient survival remains unknown. Resolution of this issue appears to be critical because of the frequency with which it leads to high-dose IV Ca therapy.

Calcium administration for cardiovascular support in critically ill patients: when is it indicated?

Calcium has a fundamental role in the maintenance of myocardial function and vascular tone. The ionized form of calcium is the most important physiologically, and this form needs to be measured to assess physiologically active calcium levels. Ionized hypocalcemia can occur as a result of various pathophysiological disturbances, and it is seen frequently in critically ill patients. Several investigators have observed a poorer prognosis in those patients with ionized hypocalcemia. It is unclear whether calcium supplementation is beneficial in these patients. It may improve cardiovascular performance, but, in contrast, it may contribute to cellular damage (especially during hypoxia following cardiopulmonary resuscitation). In sepsis, there may be an increased cellular influx of calcium, which may be deleterious to cellular function; indeed, calcium entry blockers in this situation may be protective. We review the role of calcium as an inotropic agent, its interaction with other inotropic agents, and its use during blood transfusion and during cardiopulmonary resuscitation.

New whole blood analyzers and their impact on cardiac and critical care

Miniaturized whole blood biosensors, patient-focused hospitals, and rising expectations of patients and physicians are shifting laboratory diagnostics to the point of care. Expanding transplantation and intensive care are increasing the need for rapid test results. Whole blood analysis improves accuracy, eliminates centrifugation, reduces response time, and conserves blood volume. Several hand-held, and over 20 portable or transportable whole blood instruments are now available. Criteria for instrument evaluation include test menus, point-of-care features, analysis time, on-site performance, and information integration. Whole blood analyzers measure several vital indicators (pO2, pCO2, pH, hematocrit, K+, Ca2+, Na+, Cl-, glucose, and lactate) simultaneously in less than 2 min with less than 200 microliters of whole blood. Other in vitro tests are available (Mg2+, osmolality, CO2 content, urea nitrogen, beta-hydroxybutyrate, hemoglobin, coagulation) or under development (HCO3- phosphorus). Some can be monitored in vivo (O2 saturation, pO2, pCO2, pH, glucose) or ex vivo. The clinical impact is demonstrated by ionized calcium, now established in importance for cardiac and neurologic problems, and ionized magnesium, a promising new measurement. The hybrid laboratory (a composite of conventional clinical laboratory and patient-focused testing), performance maps, and quality paths facilitate implementation of new whole blood analyzers for optimal support of cardiac and critical care, and improved patient outcomes (prospects).

Ionized calcium: pediatric perspective

Ionized calcium is a physiologically critical calcium pool. It is easily determined, although accuracy depends on sample handling. As a clinical parameter, directly measured ionized calcium has particular import in the care of neonates, patients with sepsis or other cardiovascular instability, massively transfused patients, and those undergoing cardiopulmonary bypass or liver transplantation. Disturbances of calcium occur in many other settings, however, and accurate diagnosis and research conclusions may depend on using the best measurement available. Clinical and investigational use of ionized calcium determinations represent appropriate applications of current proven technology. In the future, clinical calcium manipulation may include modifying specific transmembrane transport processes and intracellular calcium pools and movements. At the current time we are largely restricted to studies of extracellular calcium concentration and its interactions. Much is known, but Mother Nature still has too many secrets. The interested reader is referred to discussions of ionized calcium and hemodynamics, reviews of the endocrine disturbances of calcium and phosphorus, textbook discussions pertinent to general calcium disturbances, and critical care issues.

Practical aspects of advanced paediatric cardiopulmonary resuscitation

Successful cardiopulmonary resuscitation in the paediatric age group necessitates the acquisition of technical skills for rapid tracheal intubation, external cardiac compression and access to the circulation. Skills and equipment must be adapted to each age group. For optimal mechanical ventilation and the avoidance of complications, correct selection of endotracheal tube diameter and length is necessary. New techniques in resuscitation incorporate an understanding of the mechanism of blood flow during cardiac compression, the use of the intratracheal route for drug administration, and a revision of the use of catecholamines, sodium bicarbonate and calcium solutions in the treatment of asystole-bradycardia, electromechanical dissociation, ventricular fibrillation and tachycardia. Early intubation, adequate ventilation with oxygen, well performed external cardiac compression, prompt defibrillation and administration of adrenaline remain the cornerstones of advanced cardiopulmonary resuscitation.

Verapamil reverses calcium cardiotoxicity

High circulating concentrations of calcium are toxic to the heart and may cause cardiac arrhythmias and arrest. To investigate the therapeutic use of calcium antagonists in hypercalcemia, we evaluated the efficacy of verapamil hydrochloride and magnesium chloride in the treatment of experimental calcium-induced cardiac arrest in laboratory rats. Verapamil rapidly reversed the experimental calcium-induced arrest and improved survival (83% survival versus 0% in controls). Magnesium failed to reverse this toxic event. We conclude from these experimental studies that verapamil may be useful in the treatment of hypercalcemic cardiac toxicity.

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.

Plasma ionized calcium during open-heart surgery

Plasma ionized calcium has been measured in eighteen patients undergoing open heart surgery. No change in ionized calcium concentration was found during the period of cardiopulmonary bypass. In the early postbypass period, a wide range of ionized calcium concentrations was found, but this did not obviously affect myocardial performance. Factors influencing the ionized calcium concentration under these circumstances are discussed.

Calcium Antagonism in Cardiopulmonary Resuscitation

Drugs for CPR need reinvestigation; at the present time their use is as much an art as a science (14). American Heart Associations standards and guidelines and other recommendations for CPR call for the administration of 500 mg CaC12 i.v. routinely, in attempts to resuscitate patients with asystole or electromechanical dissociation (1). However, calcium's popularity for use in restarting the arrested heart has fallen (3,6,14).

There is a lack of evidence in the literature for calcium's supposed beneficial role in cardiac resuscitation. Calcium in combination with epinephrine — the traditional drug of choice in CPR — was not experimentally investigated before. On the other hand, the effects of calcium antagonists were never examined in CPR, but several theoretical considerations seemed to favor their use. However, a proposed use of calcium antagonists during CPR would lead to the withdrawal of current recommendations for the use of calcium.

Calcium and its role in cardiac arrest: understanding the controversy

Calcium ions play a critical role in excitation-contraction coupling in the myocardial cell, leading to enhanced automaticity and contractility. For these reasons the American Heart Association and the National Academy of Science-National Research Council has advocated its use in cardiac arrest due to asystole and electromechanical dissociation (EMD). However, increasing evidence suggests that calcium has been of little benefit in cardiac arrest not only because of the poor salvage rates (0%-8%) of victims in asystole or EMD and the dangerously high serum calcium levels following standard calcium administration, but also because of the cellular accumulation of calcium within the myocardium that occurs during cardiac arrest. In fact, some authors advocate the use of calcium channel blockers in protecting myocardial tissue during anoxia. Therefore the usefulness of calcium in asystole and EMD is highly suspect and must be reevaluated.

Verapamil in the treatment of asystolic and pulseless idioventricular rhythm cardiopulmonary arrests: a preliminary report

A randomized, double-blinded study was conducted to evaluate the effectiveness of the calcium antagonist verapamil in patients in cardiopulmonary arrest with asystole or pulseless idioventricular rhythm (PIVR). Twenty-one such patients presenting to the emergency department received either verapamil (10 mg) or normal saline placebo in an intravenous bolus as initial therapy. They were then treated according to standard American Heart Association guidelines with the exception that calcium was not used. If these rhythms persisted after ten minutes, a second bolus of verapamil or saline was given. Resuscitation was successful in two of ten patients (20%) receiving verapamil and in one of 11 patients (9%) receiving placebo. This similar outcome (P = .462) in this small series suggests that verapamil may not add to successful resuscitation in these patients. Additional studies are needed to define the role of calcium and its antagonists in the treatment of asystole and PIVR.