Risk factors for intraoperative bradycardia during ear, nose, throat and maxillofacial surgery.

Intraoperative bradycardia (IOB) is one of the most common cardiac arrhythmias observed in clinical anaesthetic practice. Controlled hypotension, as a strategy of lowering patient's blood pressure during anesthesia has been practiced for decades in head and neck surgery. The aim of our study was to determine the incidence and the risk factors for intraoperative bradycardia in maxillofacial, ear, nose and throat surgery, as well as to determine whether controlled hypotension affects the occurrence of IOB. The retrospective study included 2304 patients who underwent maxillofacial, ear, nose or throat surgery. We studied the influence of: sex, age, comorbidity, type of surgery, duration of anesthesia and controlled hypotension on the occurrence of IOB. IOB was registered in 473 patients (20.5%). Patients with controlled hypotension had IOB significantly more often than patients without controlled hypotension (33.9 vs 15.1%) (p = 0.000). The significant predictors of IOB were: age (OR = 1.158; 95% CI = 1.068-1.256; p = 0.000), sex (OR = 0.786; 95% CI = 0.623-0.993; p = 0.043), ischemic heart disease (OR = 2.016; 95% CI = 1.182-3.441; p = 0.010); ear surgery (OR = 1.593; 95% CI = 1.232-2.060; p = 0.000), anesthesia duration, (OR = 1.006; 95% CI = 1.004-1.007; p = 0.000) and controlled hypotension (OR = 2.204; 95% CI = 1.761-2.758; p = 0.000). IOB is common in maxillofacial, ear, nose and throat surgery, particularly in male, older age and patients with ishemic heart disease. The ear surgery, longer anesthesia duration and controlled hypotension raise the risk for occurrence of IOB.

Efficacy and safety of oral propranolol premedication to reduce reflex tachycardia during hypotensive anesthesia with sodium nitroprusside in orthognathic surgery: a double-blind randomized clinical trial.

PURPOSE: The present study sought to determine whether premedication with oral propranolol 10 mg before hypotensive anesthesia with sodium nitroprusside could reduce reflex tachycardia, the amount of sodium nitroprusside used, and blood loss during hypotensive anesthesia for orthognathic surgery. PATIENTS AND METHODS: A total of 60 patients undergoing bimaxillary surgery were studied in a prospective, randomized, and double-blind study of oral propranolol 10 mg or placebo as premedication before hypotensive anesthesia with sodium nitroprusside. Hemodynamic variables, the amount of sodium nitroprusside used, and blood loss were statistically analyzed. RESULTS: The heart rate and amount of sodium nitroprusside used were highly significantly less (P < .01) in the propranolol group, but no significant difference was found in blood loss between the 2 groups. No clinically significant complications were observed in either group. CONCLUSION: Premedication with oral propranolol 10 mg before hypotensive anesthesia with sodium nitroprusside is safe and effective to reduce reflex tachycardia and the amount of sodium nitroprusside used.

Effects of induced hypotension on breathing pattern in halothane-anaesthetized man.

The effects of hypotension induced by trimetaphan on ventilatory control were assessed in sixteen normal subjects under halothane anaesthesia. The breathing pattern, mouth occlusion pressures, lung mechanics, acid-base balance, and arterial blood gases were analysed before and during trimetaphan infusion. During induced hypotension, the only significant change in the ventilatory variables was an increase in the ratio of inspiratory duration to total cycle duration from 0.39 +/- 0.05 (SD) to 0.42 +/- 0.03; P less than 0.01. The average minute ventilation remained unchanged. No modification in lung mechanics was observed, but all subjects developed a slight but significant hypocapnic alkalosis: PaCO2 was reduced from 5.5 +/- 0.4 to 5.2 +/- 0.4 kPa (P less than 0.001) and pH increased from 7.34 to 7.36 (P less than 0.05), without change in standard bicarbonate concentration. Our data indicate that the reduction in sympathetic nervous system activity induced by trimetaphan infusion in spontaneously breathing man causes only a minor alveolar hyperventilation. The weak respiratory response to hypotension suggests that changing peripheral afferent activity has little influence on the typically rapid breathing pattern induced by halothane.

Induced hypotension for orthognathic surgery.

Achieving satisfactory hemostasis during orthognathic surgery may be difficult because of the extensive vascularity of facial structures. Hypotensive anesthetic techniques provide clear operative fields by altering regional tissue perfusion through the use of systemic vasodilators, ganglionic blocking agents, and positioning of the patient. Thorough monitoring during surgery, careful selection of patients, and close communication between the surgeon and anesthesiologist permit safe anesthesia, can decrease operating time, and usually obviate the need for transfusions.