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Bradycardia occurs during 9%-13% of spinal anesthetics and may lead to cardiac arrest. Several risk factors for the development of bradycardia have been identified, but the risk conferred by presence of abnormalities detected on preoperative electrocardiogram (ECG) has not been examined. The authors undertook the study to correlate abnormal ECG findings with the incidence of bradycardia.The data-base was previously collected from 952 patients undergoing spinal anesthesia. Patient records were reviewed and 537 had ECGs performed within 6 months of surgery. Intraoperative bradycardia was defined as a heart rate50 bpm (plus10% decrease from baseline). Abnormalities recorded from the ECG were prolonged PR interval (PR0.2 sec), atrial-ventricular conduction abnormalities, evidence of chamber hypertrophy, ischemia, and infarction. The findings were compared with incidence of bradycardia using contingency tables. Significant correlations were then evaluated with logistic regression. Significance was defined as P.05.The incidence of bradycardia in this population was 12%. Patients with a prolonged PR interval had an increased incidence of bradycardia (25%, P = .01). Other ECG abnormalities did not correlate with increased incidence of bradycardia. Duration of PR interval did correlate significantly (P = .001) but poorly (r2 = 0.014) with baseline heart rate. However, logistic regression demonstrated that prolonged PR interval was a significant and independent predictor for bradycardia (odds ratio = 3.2, P = .01).Risk factors previously identified for the development of bradycardia during spinal anesthesia include: baseline heart rate60 bpm, ASA physical status 1 versus 3 or 4, use of beta-blocking drugs, sensory block heightor = T5, and age50. The results demonstrate that prolonged PR interval on the preoperative ECG is another significant and independent predictor for bradycardia.

NMS is an uncommon disorder characterized by hyperthermia, muscle rigidity, autonomic imbalance, altered levels of consciousness and significant mortality. Successful treatment of NMS requires a high degree of suspicion, rapid recognition of clinical signs and symptoms and institution of therapy with dantrolene and possibly dopaminergic agonists. This condition is precipitated by neuroleptic drugs, which are commonly used in many medical specialties. All medical practitioners responsible for primary care, psychiatrists and anesthesiologists should be familiar with the manifestations of the hypermetabolic syndromes of Neuroleptic Malignant Syndrome, Malignant Hyperthermia, and Neuroleptic Malignant-like Syndrome and should be prepared to initiate appropriate therapy.