[Interaction of frequency-adaptive pacemakers and anesthetic management. Discussion of current literature and two case reports].

UNLABELLED: We describe unexpected episodes of paced tachycardia in two patients with rate-responsive pacemakers during anaesthesia. Five months after a heart transplant and implantation of a pacemaker a 43-year-old patient suffered cardiac tamponade as a result of chronic pericarditis. The second case involved embolic occlusion of the femoral artery in a 33-year-old female patient previously operated on for tricuspid valve replacement and implantation of a pacemaker. In both cases induction of anaesthesia was performed with fentanyl, etomidate and vecuronium. Following intubation and mechanical ventilation, the heart rates (HR) of the two patients increased to 140 and 130 min-1 respectively. This was interpreted as a sign of inadequate anaesthesia, and therefore additional doses of fentanyl and etomidate were given, with no effect on the tachycardia. After exclusion of other possible reasons for this complication such as hypokalaemia, hypercapnia, hypoxaemia or allergic reactions, unexpected functioning of the rate-responsive pacemakers due to thoracic impedance changes was assumed. Minute ventilation was reduced, lowering paced HR in 3-5 min.

CONCLUSIONS: These case reports suggest that anaesthetic management affects the action of rate-responsive pacemakers, causing haemodynamic complications, and inadequate interventions by the anaesthesiologist. Thus, it is necessary for anaesthesiologists to make a preoperative evaluation of the underlying medical disease and the type of pacemaker in order to adjust anaesthetic management accordingly and to understand the haemodynamic responses that may occur during the perioperative period. Preoperative programming to exclude the rate-responsive function is advised.