Perioperative cardiac pacing using an atrioventricular pacing pulmonary artery catheter.

An atrioventricular pacing thermodilution pulmonary artery catheter was evaluated in 40 patients undergoing cardiac surgery. The catheter was inserted in all study patients in a timely fashion without difficulty and functioned well during the perioperative period. Before the start of cardiopulmonary bypass, atrial capture was achieved in 98% of the patients (threshold mean 4.9 mA), ventricular capture in 100% (threshold mean 3.0 mA) and atrioventricular sequential (AVS) pacing in 98%. After cardiopulmonary bypass, atrial capture was achieved in 95% of the patients (threshold mean 5.2 mA), ventricular pacing in 100% (threshold mean 3.1 mA), and sequential pacing in 95%. In 27 patients in whom cardiac outputs were recorded, cardiac index increased an average of 45% (range 8% to 95%) with atrial or AVS pacing over ventricular pacing alone. In 11 patients, extended atrial pacing was used postoperatively, the longest for 93 hours. No major complications could be attributed to the study catheter. Minor complications included diaphragmatic stimulation in one patient and supraventricular tachycardia, possibly related to atrial pacing postoperatively, in one patient. These data suggest that this catheter/pacing system is effective and reliable for hemodynamic monitoring and temporary atrial or AVS pacing. In addition, the atrial pacing probe can be used perioperatively to record atrial electrograms to facilitate the diagnosis of supraventricular tachyarrhythmias.

Effects of volatile anesthetics on atrial and AV nodal electrophysiological properties in guinea pig isolated perfused heart.

BACKGROUND: Knowledge of the anesthetic effects on atrial and atrioventricular (AV) nodal electrophysiologic properties is fundamental to understand the modulatory role of anesthetics on the pathogenesis of supraventricular tachycardias, and to individualize the perioperative management of patients with supraventricular tachycardias or AV nodal conduction disturbances. Therefore the authors studied the effects of three commonly used volatile anesthetics on the electrophysiologic properties of the atrium and AV node. METHODS: The concentration-dependent electrophysiologic effects of halothane, isoflurane, and desflurane (0-2 minimum alveolar concentration [MAC]) were studied in guinea pig Langendorff-perfused hearts fit with instruments to simultaneously measure atrial and AV nodal conduction times and atrial monophasic action potential duration. Atrial and AV nodal effective refractory periods were measured simultaneously using a computer-assisted premature stimulation protocol. The concentrations of anesthetics in the gas phase were monitored by an infrared gas analyzer. RESULTS: Volatile anesthetics caused markedly different concentration-dependent effects on atrial conduction, repolarization, and refractoriness, and on AV nodal function. At equianesthetic concentrations, halothane depressed atrial conduction the most, whereas desflurane caused the greatest shortening of atrial monophasic action potential duration. Halothane had no significant effect on atrial refractoriness, whereas at 2 MAC desflurane significantly shortened and isoflurane significantly prolonged atrial effective refractory periods by 18.1+/-13.5% and 13.2+/-14.7%, respectively. On an equi-MAC basis, the rank order of potency for the anesthetics to prolong AV nodal conduction time and AV nodal ERP was halothane > desflurane > isoflurane. CONCLUSION: The different electrophysiologic effects of volatile anesthetics in the atrium and AV node suggest that these agents may modulate atrial dysrhythmogenesis in distinctly different ways.

Somatosensory-evoked potentials during aortic coarctation repair.

OBJECTIVE: To determine the incidence of somatosensory-evoked potential (SSEP) changes and the interventions based on these changes during aortic coarctation repair. DESIGN: Retrospective review. SETTING: Single-institution, university hospital. PARTICIPANTS: Eighty-four children who had undergone surgical repair of aortic coarctation from January 1984 to May 1996. INTERVENTIONS: SSEPs were monitored in all patients throughout the procedure. A persistent decrease in amplitude greater than 50% from baseline was considered significant. Duration of SSEP changes in relation to the time course of surgical repair and whether a surgical or anesthetic intervention resulted from a change in SSEPs were documented. MEASUREMENTS AND MAIN RESULTS: Eighty-four patients underwent 87 surgical procedures. SSEP changes occurred in 40% of the procedures: 38.5% with repair and 15% with test clamp, with 9% occurring during both test clamp and repair. Interventions, which included repositioning the aortic cross-clamp, elevating blood pressure, and aborting surgery, occurred in 26.4% of all procedures based on SSEP changes. No patient sustained a neurologic deficit. CONCLUSION: This is the largest series to date describing the use of SSEPs in aortic coarctation repair. These SSEP changes were often immediately amenable to changes in surgical and anesthetic management. SSEP changes and interventions based on these changes occurred with a considerable frequency.