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Introduction

Atrioventricular (AV) conduction is assessed by the relationship between the P and QRS complex. Delay in conduction between the atria and ventricles results in Atrioventricular (AV) conduction blocks [1,2]. Depending on the electrocardiogram, conduction blocks are classified into first degree, second degree and third degree AV blocks. Second degree AV blocks are further classified into type 1 ( Mobitz 1 or Wenckebach) and type 2 ( Mobitz 2 or two-toone block). Type 1 block is usually associated with narrow QRS complex reflecting AV nodal block. Type 2 AV block is usually infranodal and if its associated with a wide QRS complex then its 80% bundle branch and 20% AV node related [3]. Major perioperative concern in AV conduction abnormality is progression to complete AV block intraoperatively. Administration of atropine may subside type 1 block but worsens the scenario in type 2 block especially if its associated with bundle branch. In higher degree cardiac conduction abnormalities like type 2 AV block, there is a higher perioperative risk for bradyarrhythmias and the risk is still exponential in laparoscopic assisted surgeries [4]. Indication of permanent pacing is tricky and controversial unless the patient is symptomatic. There is no published case report of anaesthetic management of a patient undergoing laparoscopic assisted surgery with Type 2 AV block associated with bundle branch abnormalities without prior pacemaker insertion. A 75 year old male patient with carcinoma rectum presented to our surgical opd with per rectal bleeding since 3 months. His Computed Tomography (CT) findings were a 6 cm × 6 cm malignant mass with multiple enlarged mesorectal nodes and henceforth the patient received 28 fractions of 6 mv X-rays along with capecitabine chemoradiation. On post chemoradiation the malignant mass measured around 3.6 cm × 3 cm from anal verge involving lateral wall of rectum which was surgically resectable. On preanesthetic evaluation, patient is non smoker, non alcoholic, with nil comorbidities and MET>8 with nil cardiac symptoms of dizziness, syncope, chest pain. Routine 12 lead electrocardiogram revealed type 2 AV block with left bundle branch block. For further evaluation on cardiologist reference, 2D echocardiogram and angiogram was performed which had no significant findings. Preoperatively we counselled the patient about potential risks associated and higher risk of progression to complete AV block and additional laparoscopic assisted risk without prior temporary pacemaker insertion. On patient approval we proceeded with surgery without any preoperative insertion of a temporary pacemaker.

Case Presentation

On the day of surgery, after shifting patient to the operation room, all standard monitors were connected, patients ECG pattern showed second degree AV block with left bundle branch block similar to that of preoperative ECG findings.In addition to the above standard monitors, radial artery cannulation was done under local anaesthesia for beat to beat blood pressure monitoring. In view of emergency, an external transcutaneous pacemaker was kept ready. On table vital parameters showed a heart rate of 65 bpm, blood pressure was 112/72 mmHg, SpO₂ was 98% at room air and Perfusion Index (PI) of 0.82. The patient had 20-gauge cannula fixed from the surgical ward in addition we secured 18 gauge cannula in operation theatre before induction. No pre medications were administered preoperatively, after preoxygenation of patient for 3 minutes, general anaesthesia was induced with 100 mg propofol, 100 mg fentanyl and 6 mg vecuronium intravenously and just 90 seconds prior to endotracheal intubation 50 mg of 2% xylocard was administered intravenously. Then, patient was intubated with size 8 endotracheal tube and then connected to mechanical ventilator using volume control mode with 400 ml tidal volume, respiratory rate of 14 per minute and a positive end- expiratory pressure of 5 mm of Hg. Peak Inspiratory Pressure (PIP) maintained at 21 mm of Hg, and End Tidal Carbon Dioxide (ETCO₂) of around 40 mm of Hg. Intraoperatively, anaesthesia was maintained with 50% oxygen and air mixture with inhalational agent as Sevoflurane(1%-2%) and titrated bolus doses of fentanyl and vecuronium. Immediately after induction, patient had a heart rate of 38 bpm-40 bpm , atropine of 0.6 mg was administered immediately and heart rate improved to 90 bpm-100 bpm and patient remained hemodynamically stable and henceforth no requirement of pacing or pharmacological interventions. After discussion with surgeons, In view consideration of complications which may occur during insufflation of CO₂ during laparoscopic surgeries, surgeons were instructed to maintain a flow rate of 6 l/min-8 l/min, and not to exceed 12 mm of Hg intraabdominal pressure. Perioperatively, the patient was hemodynamically stable without any significant events and the patient emerged smoothly and extubated in the operating room. On the 2^nd postoperative day, in the intensive care unit patient developed one episode of supraventricular tachycardia with palpable pulse with blood pressure of around 140/90 mmHg, SpO₂ was 99% and immediately 60 mg xylocard intravenously was administered and rhythm reverted back to sinus rhythm. During that time, blood electrolytes and cardiac biomarkers including troponin, 12 lead ECG and 2D Echo were performed and were within normal limits. For further two days the patient was kept in the intensive care unit and the patient was quite stable and was discharged on the 7^th postoperative day [5-8].

Discussion

Development of complete AV block remains a potential risk in patients with cardiac conduction abnormalities. Laparoscopic surgeries using CO₂ to make a pneumoperitoneum, tend to have a higher risk of bradycardia, arrhythmia and cardiac arrest which may require cardiopulmonary resuscitation. So, our patient had both the potential preoperative risk factors for progression to complete heart block. But the choice of implantation of temporary pacemaker prior to surgery was not opted by us due to patient refusal as well patient being asymptomatic, henceforth we proceeded to surgery with external transcutaneous pacemaker as standby. Prognosis of a patient with AV node (nodal block) is usually benign and block distal to AV node (infranodal block) has a potential high risk of progression to complete heart block. Electrocardiographically, wide QRS associated AV block is usually infranodal and may require prior pacemaker insertion because of chances of progression to complete heart block are comparatively higher. Electrophysiological studies are definitely needed to anatomically locate the site of AV block. Since it is invasive and the patient being asymptomatic as well as not willing for the EPS we proceeded with the surgery. Preoperative administration of anticholinergic medications to prevent bradycardia haven't showed any significant benefit in terms of mortality and morbidity. So, we didn't consider preoperative administration of anticholinergics. Peripoeratively, our patient developed bradycardia post induction, one such potential reason could be hypoxia, hypercarbia and the anaesthetic medications used for induction. Hypoxia and hypercarbia events are less likely to occur because the patient was adequately preoxygenated and well ventilated, and next possibility could have been our choice of muscle relaxant. Vecuronium and rocuronium have potential vagolytic activity, so our choice should have been cisatracurium, due to nonavailability of cisatracurium at our institute we had vecuronium as the only choice of muscle relaxant. The usage of propofol and fentanyl could have also been the Few clinical studies have shown, anaesthetic agents when administered in relevant doses had fewer chances of causing negative dromotropic effect on AV conduction [9,10].

Laparoscopic surgeries have shown to be a potential risk factor for having negative dromotropic effect on AV conduction. Peritoneal stretch and CO₂ insufflation on high flow rate of CO₂ insufflation leads to strong and fast vagal response, and can have direct effects on the cardiovascular system. Studies have shown limiting peritoneal pressure to 15 mmHg and maintaining flow rate of 8l/min could be a precautionary and protective measure to avoid negative dromotropic effect on cardiovascular events. So, after discussion with the surgeon we limited the flow rate of around 8 l/min and abdominal pressure not to exceed 12 mm Hg. so, in our patient, after CO₂ insufflation we didn't have any significant cardiovascular events requiring intervention. Intraoperatively during the surgery patient remained hemodynamically stable and patient was successfully extubated and shifted to intensive care unit. On the second postoperative day patient developed sudden Supraventricular Tachycardia (SVT) , with heart rate of around 180 bpm, palpable peripheral pulses, blood pressure of 130/80 mmHg, and peripheral saturation of 98%. Vagal manoeuvres and pharmacological management with adenosine or calcium channel blockers are the suggested treatment for SVT. Vagal manoeuvres weren't performed in our patient due to history of AV block, on administration of adenosine 6 mg intravenously SVT settled. Additionally, to know the cause we assessed cardiac and metabolic status, and were found to be normal. Following the event , the patient remained asymptomatic and after 4 days patient was discharged and referred to a higher cardiac centre for further evaluation and management as per cardiologist advice.

Conclusion

Patients with higher degree AV block (Mobitz type 2 AV block, 3rd degree) tend to have severe damage to the conduction system and when posted for laparoscopic surgeries risk tends to increase exponentially and chances of progression to asystole, ventricular tachycardia and sudden cardiac death are higher. By this case we emphasise that prior prophylactic pacemaker in type 2 AV block could be a precautionary and when it is not feasible, general anaesthesia could still be safely performed in patient posted for laparoscopic surgeries with early recognition, effective communication and timely intervention.cause of bradycardia but only anaesthetic agents couldn't be claimed as the sole agent in patient with prior AV block.

References

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