Prophylactic lidocaine in the prehospital patient with chest pain of suspected cardiac origin

Prophylactic lidocaine use in acute myocardial infarction: incidence and outcomes from two international trials. The GUSTO-I and GUSTO-IIb Investigators

BACKGROUND

Early meta-analyses suggested that prophylactic lidocaine use reduces ventricular fibrillation but increases mortality rates after acute myocardial infarction. We determined the frequency and effect on clinical outcomes with its use in the thrombolytic era.

METHODS AND RESULTS

We studied 43,704 patients enrolled in GUSTO-I or GUSTO-IIb who had ST-segment elevation, underwent thrombolysis, and survived at least 1 hour after enrollment. Odds ratios (OR) and confidence intervals (CI) were calculated for the risk of asystole, atrioventricular block, ventricular fibrillation, and ventricular tachycardia during hospitalization; for 24-hour, in-hospital, and 30-day mortality rates; and for 24-hour and 30-day mortality rates after adjustment for baseline predictors of death. In GUSTO-I and GUSTO-IIb, 16% and 3.5% of patients, respectively, received prophylactic lidocaine. They had a lower risk of death at 24 hours (OR 0.81, 95% CI 0.67 to 0.97) and trends toward lower odds of in-hospital death (OR 0.90, 95% CI 0.81 to 1.01) and death at 30 days (OR 0.92, 95% CI 0.82 to 1. 02). After adjustment for baseline characteristics, however, the odds of death were similar with or without lidocaine (OR 0.90 and 0. 97, respectively). Outside the United States, lidocaine was associated with higher incidences of all serious arrhythmias, but in US patients it conferred a lower likelihood of ventricular fibrillation and no increase in asystole, atrioventricular block, or mortality rates.

CONCLUSIONS

Prophylactic lidocaine use has decreased with the advent of thrombolysis, although its use may not be associated with increased mortality rates.

Multicenter randomized trial and a systematic overview of lidocaine in acute myocardial infarction

BACKGROUND

More than 20 randomized trials and 4 meta-analyses have been conducted on the use of prophylactic lidocaine in acute myocardial infarction (MI). The results suggest that lidocaine reduces ventricular fibrillation (VF) but increases mortality rates in acute MI.

METHODS AND RESULTS

Patients with ST-elevation MI who were examined <6 hours after symptom onset (n = 903) were randomly assigned to either lidocaine or no lidocaine and to either streptokinase and heparin or heparin alone. Lidocaine was given as 4 boluses of 50 mg each every 2 minutes, then an infusion of 3 mg/min for 12 hours, then 2 mg/min for 36 hours. We compared the incidence of in-hospital death and ventricular arrhythmias. We then performed a meta-analysis of prophylactic lidocaine in acute MI that included these and prior trial results. The rates of VF and death with and without lidocaine were calculated for each trial, then odds ratios (OR) with confidence intervals (CI) were calculated for the risk of these events overall with and without lidocaine. Patients given lidocaine in the randomized study had significantly less VF (2.0% vs 5.7% without lidocaine, P =.004) and a trend toward increased mortality rates (9.7% vs 7.0%, P =.145). Meta-analysis revealed nonsignificant trends toward reduced VF (OR 0.71, 95% CI 0.47 to 1. 09) and increased mortality rates (OR 1.12, 95% CI 0.91 to 1.36) with lidocaine.

CONCLUSIONS

Lidocaine reduces VF but may adversely affect mortality rates. The routine use of prophylactic lidocaine in acute MI is not recommended.

Clinical safety of lidocaine in patients with cocaine-associated myocardial infarction

STUDY OBJECTIVE

To evaluate the safety of lidocaine in the setting of cocaine-induced myocardial infarction (MI).

DESIGN

A retrospective, multicenter study.

SETTING

Twenty-nine university, university-affiliated, or community hospitals during a 6-year period (total of 117 cumulative hospital-years).

PARTICIPANTS

Patients with cocaine-associated MI who received lidocaine in the emergency department.

RESULTS

Of 29 patients who received lidocaine in the setting of cocaine-associated MI, no patient died; exhibited bradydysrhythmias, ventricular tachycardia, or ventricular fibrillation; or experienced seizures after administration of lidocaine (95% confidence interval, 0% to 11%).

CONCLUSION

Despite theoretical concerns that lidocaine may enhance cocaine toxicity, the use of lidocaine in patients with cocaine-associated MI was not associated with significant cardiovascular or central nervous system toxicity.

Effects of prehospital care on outcome in patients with cardiac illness

STUDY OBJECTIVE

To compare outcomes of patients with acute cardiac illness transported by ambulance for whom prehospital care was provided by emergency medical technician-paramedics (EMT-Ps) or EMTs trained in defibrillation (EMT-Ds).

DESIGN

A prospective chart review carried out over 3.5 years.

SETTING

The Hamilton-Wentworth region of Ontario, Canada, which covers 1,136 km2 and includes five receiving hospitals.

PARTICIPANTS

We prospectively identified 8,720 potentially eligible patients from approximately 30,000 who presented to the ambulance service. We reviewed hospital charts to confirm eligibility. The group of 8,720 patients yielded 3,066 patients with acute cardiac illness who met all other eligibility requirements. We excluded patients in cardiac arrest.

RESULTS

Incidence of myocardial infarction (MI), length of hospital stay, and mortality were evaluated. Analysis was performed with chi 2 tests for association, linear regression, and logistic regression. Of the eligible patients who received prehospital EMS care, 783 sustained MIs. The proportions of people discharged alive with the diagnosis of MI did not differ between crew types (P = .16). Average hospital stay was 13 days in both groups for patients with the discharge diagnosis of MI; hospital stay ranged from 9 (EMT-D) to 11 days (EMT-P) for any patient with a discharge diagnosis other than MI. These values were statistically similar. The odds ratio of having had an MI after treatment by an EMT-D crew was 1.02 (95% confidence interval, .86 to 1.21) compared with that for treatment by an EMT-P crew.

CONCLUSIONS

In an urban setting with short (less than 10 minutes) average transport times, the availability of prehospital paramedic care does not affect occurrence of MI, length of hospital stay, or mortality of patients presenting to the EMS system with cardiac illness.

Declining incidence of ventricular fibrillation in myocardial infarction. Implications for the prophylactic use of lidocaine

BACKGROUND

The purposes of the present investigation were 1) to track the incidence of primary ventricular fibrillation (VF) in the control and lidocaine-treated groups in the randomized control trials (RCTs) of lidocaine prophylaxis against primary VF in acute myocardial infarction, with particular emphasis on the time frame of the randomized trial, and 2) to estimate the number of patients who must receive lidocaine currently to prevent one episode of VF.

METHODS AND RESULTS

The following variables from RCTs published between 1969 and 1988 were entered into logistic regression models to predict the percent of patients developing VF: year of publication of the RCT, method of data analysis used in the RCT, route and technique of lidocaine administration, duration of monitoring for VF, and exclusion criteria before randomization (congestive heart failure/cardiogenic shock, ventricular tachycardia/VF, or bradycardia/atrioventricular block). Year of publication was a significant predictor of VF in both the control and lidocaine groups (p less than or equal to 0.002) even after adjusting for other covariates. Based on a univariate logistic regression model with year as the predictor variable, it was estimated that the incidence of primary VF in the control group fell from 4.51% in 1970 to 0.35% in 1990 and from 4.32% down to 0.11% for the lidocaine group over the same time period. Thus, about 400 patients would currently need prophylaxis with lidocaine to prevent one episode of VF.

CONCLUSIONS

Present estimates of the risk:benefit ratio of lidocaine prophylaxis should consider the low risk of VF in control patients and the large number who need lidocaine prophylaxis to prevent one episode of VF. When added to the previously reported trend toward excess mortality in lidocaine-treated patients, these data argue against the routine prophylactic use of lidocaine in patients with acute myocardial infarction.

Prehospital prophylactic lidocaine does not favorably affect outcome in patients with chest pain

STUDY OBJECTIVES

The purpose of our study was to determine the morbidity and mortality in initially stable patients presenting to paramedics with chest pain; to examine possible beneficial effects of its use, including reduction of sudden death syndrome in the prehospital and emergency department setting; and to determine if prophylactic lidocaine is associated with adverse effects in this patient population.

DESIGN AND SETTING

This was a randomized, prospective study using prophylactic lidocaine in patients complaining of chest pain who presented to our paramedic system between January 1984 and January 1988.

TYPE OF PARTICIPANTS

All patients aged 18 years or older with chest pain of suspected cardiac origin who presented to paramedics during the study period were included. Excluded were patients presenting with warning arrhythmias, second- or third-degree heart block, bradycardias of less than 50, hypotension of less than 90 mm Hg systolic, or known allergy to lidocaine.

INTERVENTIONS

Patients were randomized into two groups, the lidocaine-treated group and the control group. An initial bolus of 1 mg/kg IV lidocaine was administered to the lidocaine-treated group. A simultaneous 2 mg/min IV drip was established. Ten minutes after the first dose of lidocaine, a second bolus of 0.5 mg/kg was administered.

MEASUREMENTS AND MAIN RESULTS

During the study period, 1,427 patients were entered; 704 received lidocaine, and 723 did not. Discharge diagnoses included acute myocardial infarction (31%), unstable angina (33%), other cardiac problems (7%), and noncardiac problems (29%); overall mortality rate was 7.4%. There was an equal distribution of deaths between the lidocaine-treated group (57) and the control group (48). Six patients had a cardiac arrest in the prehospital setting, and 15 had a cardiac arrest in the ED. Malignant ventricular arrhythmias as the precipitating arrest rhythm in patients with acute myocardial infarctions were similar for the lidocaine-treated and control groups. The incidence of adverse effects, including hypotension, bradycardias, second- or third-degree heart blocks, tinnitus, and altered mental status, was similar in both groups.

CONCLUSION

There are no benefits from the administration of prehospital prophylactic lidocaine in stable patients with chest pain; therefore, routine use in this setting appears unwarranted.

Pharmacologic intervention in prehospital care: a critical appraisal

In more than 15 years of paramedic operation, fewer than 15 prehospital studies have been undertaken on the pharmacologic intervention by paramedics. Many of these studies suffer from inadequate sample size or deficient study design. There is no evidence that any medication given by the prehospital care provider is beneficial or cannot safely be delayed until arrival at hospital. Multicenter trials must be designed and implemented if we are to provide the evidence necessary to evaluate our current practice.