Preanesthesia Evaluation and Pacemaker Reprogramming

Preoperative management of the patient with a pacemaker includes evaluation and optimization of coexisting diseases. ACC guidelines suggest that cardiac testing (stress tests, echocardiograms) should be dictated by the patient's underlying diseases, medications, symptomatology, interval from the last testing, and planned intervention.^[3]

No special laboratory tests or radiographs are needed for the patient with a conventional pacemaker. Chest films rarely depict lead problems, not all devices have radiographic markings, and a standard chest x-ray can exclude the generator or its markings. However, a patient with a BiV pacer (or defibrillator) might need a chest film to document the position of the coronary sinus (CS) lead, especially if central line placement is planned. Currently, there are no data or guidelines regarding the placement of a central line in the setting of a coronary sinus lead, and, since these leads have no fixation, they might be more easily dislodged than a standard pacemaker (or defibrillator) lead. In fact, in early studies, spontaneous CS lead dislodgement was found in more than 11% of patients.^{[27] [28]}

Important features of the preanesthetic device evaluation are shown in Appendix 1 . Current NASPE and Medicare guidelines include telephonic evaluation every 4–12 weeks (depending upon device type and age) and at least one direct evaluation (i.e., a device interrogation with a programmer) at least once per year.^[29] In a recent abstract, Rozner et al reported significant noncompliance

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For current pacemakers, interrogation with a programmer remains the most reliable method for evaluating battery voltage, battery impedance, lead performance, and adequacy of current settings. Special attention should be paid to patients from countries where pacemakers might be reused,^{[31] [32]} since battery life (typically 5–7 years, perhaps longer in some new devices) might not be related to length of implantation in the current patient. For any device with a battery voltage less than 2.6 volts or battery impedance (where available) greater than 3000 ohms, the device manufacturer should be consulted about the possible need for elective replacement of the device prior to the delivery of an anesthetic or surgery.

Appropriate reprogramming ( Table 35-5 ) is the safest way to avoid intraoperative problems, especially if monopolar "Bovie" electrosurgery will be used. The pacemaker manufacturers stand ready to assist with this task (see Appendix 2 for company telephone numbers), however, any industry-employed allied professional must be supervised by an appropriately trained physician.^[33] Hospital guidelines and policy should reflect the need for a physician with privileges to implant pacing devices to review and validate any pacing changes that are made to a pacemaker by a company representative.

Reprogramming a pacemaker to asynchronous pacing at a rate greater than the patient's underlying rate usually ensures that no over- or undersensing during EMI will take place, protecting the patient. However, there is one case report involving a Telectronics device which would open its output circuitry (i.e., no pacing stimuli would be delivered) in the presence of high voltage EMI.^[34] At our institution, we have observed a Medtronic Kappa 400 dual chamber device in the DOO mode drop its rate during use of ESU, presumably due to high battery current drain.

Reprogramming a device will not protect the device from internal damage or reset caused by electromagnetic interference. Additionally, setting a device to asynchronous mode causes the pacemaker to ignore premature atrial or ventricular systoles, which could have the potential to create a malignant rhythm in the patient with significant structural compromise of the myocardium.^[35]

In general, rate responsiveness and other "enhancements" (dynamic atrial overdrive, hysteresis, sleep rate, AV search, etc.) should be disabled by programming.^{[3] [36] [37]} Note that for many Guidant and/or CPI devices, Guidant Medical recommends increasing the pacing voltage to "5 volts or higher" in any case where the monopolar electrosurgical unit will be used. Few cardiologists follow this recommendation, but there are reports of threshold changes during both intrathoracic^[38] and non-chest surgery.^[39] Recently, Levine and colleagues reported that significant noncardiac disease states could increase pacing threshold.^[40]

Special attention must be given to any device with a minute ventilation (bioimpedance) sensor ( Table 35-6 ), because inappropriate tachycardia has been observed secondary to mechanical ventilation, ^{[41] [42]} monopolar "Bovie" electrosurgery,^{[41] [43] [44]} and connection to an electrocardiographic monitor with respiratory rate monitoring.^{[45] [46] [47] [48] [49] [50]} Sometimes, this pacemaker driven tachycardia has led to inappropriate, unsuccessful pharmacologic treatment of the tachycardia. ^[42]