Lidocaine prophylaxis in coronary revascularization patients: a randomized, prospective trial

Prevention and management of perioperative arrhythmias in the thoracic surgical population

Although bradyarrhythmias or malignant ventricular tachyarrhythmias have been reported in less than 1% of patients following noncardiac surgery, rapid atrial arrhythmias more frequently affect the elderly who undergo thoracic operations. This article focuses on new issues leading to the improved understanding of the pathophysiology and mechanisms of postoperative atrial arrhythmias. It discusses new risk factors and a prediction rule for postthoracotomy atrial fibrillation (AF), reviews prophylaxis and acute therapeutic interventions for postthoracotomy AF, and highlights the most recent recommendations of the American Heart Association Task Force on the management of patients who have AF with emphasis on preventing thromboembolic events.

Strategies for perioperative arrhythmias

Rapid atrial arrhythmias affect close to one million elderly Americans who undergo cardiac or non-cardiac operations annually and have been associated with prolonged hospital stays. In contrast, bradyarrhythmias or ventricular arrhythmias severe enough to require treatment occur in less than 1% of patients who undergo all types of surgery, including cardiac. This article focuses on new issues leading to the improved understanding of the pathophysiology and mechanisms of post-operative atrial arrhythmias. New approaches directed at prophylaxis and acute therapy of atrial arrhythmias are discussed, as are recommendations to prevent thromboembolic events. Practice and research agenda are proposed.

The incidence and outcome of ventricular arrhythmias after noncardiac thoracic surgery

Atrial arrhythmias are common after thoracic surgery, but the incidence and significance of ventricular arrhythmias early after such surgery are not well established. Our goal was to determine the incidence and outcome of this complication from a continuing prospective database in 412 patients who had lobectomy (n = 243) or pneumonectomy (n = 169) and were continuously monitored with Holter recorders for 72-96 h postoperatively. The primary end point of the study was the occurrence of ventricular tachycardia (VT) defined as three or more consecutive wide complexes. Sixty-one of 412 patients (15%) developed 1 or more episode of VT. There were no episodes of sustained (>30 s) VT and no patient required treatment for hemodynamic compromise associated with any VT episode. Patients with VT had a more frequent incidence of a preoperative left bundle branch block (P = 0.01) but did not differ in other clinical characteristics, operative data, or core temperature on arrival to the postanesthesia care unit, when compared with those without VT. Patients who developed VT had significantly more atrial premature contractions (P < 0.001), ventricular premature contractions (P < 0.001), ventricular couplets (P < 0.001), and postoperative atrial fibrillation, 21 of 61 (34%) versus 58 of 351 (17%), P = 0.001, than those without VT, respectively. Multivariate logistic regression analysis revealed that only postoperative atrial fibrillation occurrence was independently associated with VT (relative risk 2.6, 95% confidence intervals 1.4 to 4.8, P = 0.002). We conclude that nonsustained VT after noncardiac thoracic surgery occurs frequently but is not associated with poor outcome. The strong association of atrial and ventricular arrhythmogenesis with VT suggests that vagal withdrawal and/or adrenergic hyperactivity may have a role in precipitating these events in the early postoperative period.

IMPLICATIONS

In 412 patients, we determined that the incidence of nonsustained ventricular tachycardia after major thoracic surgery is 15% and is not associated with poor outcome.

High-dose bolus lidocaine for chemical cardioversion of atrial fibrillation: a prospective, randomized, double-blind crossover trial

BACKGROUND

Most drugs used for chemical cardioversion of atrial fibrillation have significant proarrhythmia risk and require close monitoring after administration. Lidocaine has few of the proarrhythmic concerns of most antiarrhythmic drugs and, at high bolus doses, prolongs the atrial refractory period well enough to be effective in converting atrial fibrillation to sinus rhythm. This finding has been previously demonstrated in a dog model. We sought to confirm the animal findings in human beings with lidocaine doses of 1.5 to 2.5 mg/kg.

METHODS

Twenty patients with atrial fibrillation scheduled for elective cardioversion were enrolled in this study. In a randomized, double-blind, crossover study design, each patient received intravenous bolus lidocaine or saline. Patients were observed for 10 minutes after the initial bolus to assess efficacy. The second test drug was then delivered if the first was unsuccessful at cardioversion.

RESULTS

All 20 patients received both lidocaine and saline placebo therapy in a crossover manner. None of the 20 patients converted to sinus rhythm with either therapy. The 95% confidence interval for effectiveness of lidocaine in this population was 0% to 14%.

CONCLUSION

In this population of patients referred for elective cardioversion of atrial fibrillation, high-dose bolus lidocaine was ineffective in converting patients to sinus rhythm. Although this study was not sufficiently powered to rule out a low efficacy of lidocaine (<15%) or a higher efficacy in certain subgroups of atrial fibrillation, routine use of lidocaine for this indication is not warranted.

Potassium concentrations and ventricular ectopy: a prospective, observational study in post-cardiac surgery patients

OBJECTIVE

To determine whether a correlation exists between concentrations of intracellular and extracellular potassium and to determine the frequency of ventricular ectopy in patients after cardiac operations.

DESIGN

Prospective, observational clinical evaluation.

SETTING

Surgical-respiratory intensive care unit of a university-affiliated tertiary care center.

PATIENTS

Continuous 24-hr electrocardiographic monitoring was performed, and serum (extracellular) and erythrocyte (intracellular) potassium concentrations ([K+]e and [K+]i) were determined, before cardiopulmonary bypass, immediately postoperatively, and at 2, 4, 12, and 20 hrs after elective coronary bypass grafting in 31 patients.

INTERVENTIONS

None. Potassium replacement was left to the discretion of the attending physicians.

MEASUREMENTS AND MAIN RESULTS

Although the mean [K+]e varied significantly during the postoperative 24-hr period (p<.0001), the [K+]i did not (p = .953). No significant correlations were found between premature ventricular beats and [K+]i, [K+]e, or [K+]i/[K+]e (all p>.05). However, among the few patients who had one or more episodes of ventricular tachycardia (VT) within 30 mins of a study K+ sample, the mean [K+]e was significantly lower during the episode(s) of VT compared with the mean [K+]e in the absence of VT (p<.01).

CONCLUSIONS

Although it is clear that over the clinically acceptable range of [K+]e and [K+]i concentrations seen in this population, there is no correlation between potassium concentrations and the occurrence of premature ventricular beats, the infrequent association of more serious ventricular ectopy, VT, with lower [K+]e concentrations supports the practice of using serum potassium to guide potassium replacement in patients after cardiac operations.

Arrhythmias and conduction disturbances after coronary artery bypass graft surgery: epidemiology, management, and prognosis

CABG is associated with many perioperative complications, including supraventricular and ventricular arrhythmias and conduction disturbances. Atrial fibrillation occurs in < or = 40% of patients after CABG and is especially common in older patients. Although it is often benign and self-limited, it can lead to complications such as stroke. Treatment consists primarily of control of the ventricular response rate; in some cases, antiarrhythmic drugs or electrical cardioversion are needed. Anticoagulation should be considered in appropriate cases of persistent (48 to 72 hours) atrial fibrillation after initial treatment. Prophylaxis, especially with beta-blocking agents, seems to be effective and should be considered in appropriate cases. Simple ventricular arrhythmias are common after CABG and do not affect the patient's prognosis; however, sustained VT/VF occur infrequently (< 2% of patients) and carry a high mortality rate. Treatment is aimed at correcting precipitating factors (e.g., myocardial ischemia). Electrophysiologically guided drug therapy and implantation of an ICD should be considered in appropriate cases for patients who survive the initial events. Transient minor conduction disturbances are common after CABG; in some patients persistent AV block and sinus node dysfunction develop and may require treatment with permanent pacemaker.

Magnesium sulfate prophylaxis after cardiac operations

One hundred patients undergoing elective cardiac operations were randomized into placebo (n = 54) and magnesium (n = 46) groups. The magnesium group received six doses of 2.4 g (19.2 mEq) magnesium sulfate intravenously in the first 24 hours after the cardiac operation. The magnesium group had higher serum magnesium concentrations postoperatively (1.09 +/- 0.20 versus 0.75 +/- 0.13 mmol/L; p < 0.0001), postoperative day 1 (1.49 +/- 0.34 versus 0.70 +/- 0.12 mmol/L; p < 0.0001) and postoperative day 2 (0.96 +/- 0.19 versus 0.76 +/- 0.07 mmol/L; p < 0.0001). Patients in the magnesium group had a lower incidence of ventricular tachyarrythmias (VTs) (17.3% versus 51.9%; p = 0.0006), less need for treatment (6.5% versus 20.3%; p < 0.0001), fewer VT episodes/patient (0.3 +/- 0.8 versus 1.39 +/- 1.9; p < 0.0001), and a reduction in the severity of VTs as measured by the modified Lown grade (p = 0.0002). No differences were demonstrated with respect to supraventricular tachyarrythmias. The magnesium group had reduced absolute creatine kinase-MB levels (5.3 +/- 4.2 versus 28.4 +/- 28 IU/L; p = 0.001) as well as creatine kinase-MB fraction (0.01 +/- 0.02 versus 0.05 +/- 0.04; p = 0.001) on postoperative day 1. Serum magnesium concentrations were lower during VTs than during periods of sinus rhythm (0.75 +/- 0.75 versus 1.02 +/- 0.35 mmol/L; p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)