Technical nuances of performing a neurosurgical procedure in a patient with cardiac pacemaker: Winter on fire!
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.253638
Source of Support: None, Conflict of Interest: None
The neurosurgical team of our institute was recently faced with the challenge of operating upon a cerebellopontine angle lesion in a patient with a cardiac pacemaker in place. The patient, a 40-year old male patient, had presented to us with the complaint of loss of hearing in the left ear since 5 years and headache since the past 2 years. On examination, he had sensorineural hearing loss in the left ear along with left-sided facial numbness in the V1–V3 distribution. The patient underwent a computed tomography (CT) scan of the head, which showed an ill-defined mass in the cerebellopontine angle. The mass was enhancing inhomogenously, and there was no clear plane of demarcation with the normal cerebellum [Figure 1]. Here on, the challenges surfaced.
MRI in this patient was not possible as placing a magnet over a permanent pacemaker temporarily reprograms the “pacer” in an asynchronous pacing mode. Potentially, any device that emits radiofrequency waves between 0 and 109 Hz can generate electromagnetic interference (EMI) and hence prevent proper functioning of the device. However, higher frequencies such as those of the X-ray or a CT scan are unlikely to cause any dysfunction unless the exposure is for a prolonged time, which may damage the insulation and lead to short-circuiting of the device., Hence, we had to proceed with only a CT in this case.
There are other sources, which may produce EMI during the surgery, and hence have to be cared about. Monopolar cautery is contraindicated; hence, the bleeding and time of exposure is more. Again, bipolar cautery cannot be used for prolonged intervals, ideally to be used for less than 15s, and hence presents a problem during hemostasis or intraoperative bleeding. Further, cautery dispersal plate needs to be placed as distal as possible with respect to the device, and more cutting rather than coagulation modes should be used. An equipment to achieve a rapid cardioversion with external defibrillators, whose paddles are placed as far away from the device as possible, should in place. Even evoked potential monitors and nerve stimulators may produce EMI; thus, anatomical landmarks for facial nerve are the only guides.
Positioning itself can damage the device or the leads or the site of lead implantation. This effectively rules out prone positioning, and either lateral or supine position with neck rotation remains the only option, with the latter being preferred in case of the need for defibrillation or resuscitation.
Along with this, preoperative considerations include having the device technician on standby in case of need for reprogramming, and ensuring a backup source of pacing or defibrillation, or both. Strict monitoring for hemodynamic stability, with rapid detection of EMI interference with the defibrillator, with either termination of the interference or reversal of asynchronous pacing using a backup pacer or defibrillator is mandatory.
There are further anesthetic considerations: Hyperventilation may lead to a sudden fall in plasma potassium and needs to be avoided; a significant volume loss or loading, a massive blood transfusion, or an inadvertent high volume of local anesthetics in the blood may alter lead impedance.
Postoperatively, an intense hemodynamic monitoring is needed with a review of the device and its activity before transferring the case from an intensive care unit (monitored) setting to the ward (non-monitored) setting.
Keeping all this concerns in mind, we went ahead with surgery in our patient. Fortunately, the tumor was soft and minimally vascular and made our job much easier. We could remove the tumor near-totally, except for the portion near the meatus where it was inseparable from the seventh nerve fibers. In the absence of an intraoperative monitoring, the seventh nerve could not be entirely preserved except for some of the fibers. The patient developed grade 4 facial palsy but had no other neurological deficits following surgery. After 24 h of surgery, his pacemaker was reprogrammed to the baseline level. Postoperative CT scan confirmed the extent of excision [Figure 1].
This case posed unique challenges during the surgical management of a rather common neurosurgical problem.
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