Anesthetic challenges of decompressive craniotomy for the right frontal lobe abscess in a patient with Ebstein's anomaly: A rare case report.

Ebstein's anomaly is a rare congenital heart disease characterized by downward displacement of the tricuspid valve, atrialization of right ventricle, enlarged right atrium with tricuspid regurgitation, or stenosis. It is often associated with atrial septal defect (ASD) or patent foramen ovale with right to left shunt. It has a varied clinical presentation and can manifest as cyanosis, ventricular, or supraventricular arrhythmias and recurrent episodes of congestive heart failure. We describe the anesthetic management of a female patient with Ebstein's anomaly who had right frontal lobe abscess due to paradoxical embolism for decompressive craniotomy.

INTRODUCTION

Ebstein's anomaly (EA) is a rare congenital heart disease characterized by downward displacement of tricuspid valve, atrialization of right ventricle, large right atrium, tricuspid regurgitation (TR), and associated atrial septal defect (ASD) or patent foramen ovale (PFO) in 80% of cases.[1] The resultant right to left shunt can cause paradoxical emboli. The natural history of the disease is variable. It can present as cyanosis and congestive heart failure (CHF) in neonates and infants. Those who survive to adulthood may remain asymptomatic but symptoms can be precipitated by pregnancy or onset of arrhythmias.[2] There are limited reports in the literature about patients with EA coming for noncardiac surgery.[3-5] This case report describes the successful anesthetic management of decompressive craniotomy for right frontal lobe abscess in a female patient with Ebstein's anomaly.

CASE REPORT

A female patient aged 47 years came to neurosurgical department with complaints of severe headache for 1 week. She was diagnosed to have right frontal lobe abscess based on CT and MRI scan findings. She is a known case of Ebstein's anomaly of heart diagnosed 12 years back. She was apparently normal before, she then developed chest pain, palpitations, dyspnoea, on exertion (NYHA grade III) and poor effort tolerance. She was on regular treatment for recurrent episodes of CHF with diuretics and digoxin. Her physical examination revealed peripheral cyanosis, grade III clubbing of all digits, irregular heart rate and peripheral oxygen saturation (SpO2) of 84%. On auscultation grade II pansystolic murmur was heard in tricuspid area. Electrocardiogram (ECG) showed irregular rhythm with intermittent atrial and ventricular ectopics, large P waves, and T wave inversion in inferior leads. Chest x-ray revealed cardiomegaly and right atrial enlargement. Two-dimensional echo showed right atrial enlargement, atrialization of right ventricle, moderate TR and pulmonary hypertension, intact atrial septum, and moderate left ventricular dysfunction with ejection fraction of 50%. Her laboratory investigations revealed polycythemia with haematocrit of 59.3%, hemoglobin 18.9 grams%, total white blood cell count of 14 600/mm3, and creatinine of 1.1 mg%, normal blood sugar, and serum electrolytes. Arterial blood gas analysis revealed severe hypoxemia with PaO2 of 52 mm Hg and SaO2 of 87%.

Preoperatively she was advised to stop tablet digoxin and diuretics one day prior to surgery. She was put on tablet amiodarone 150 mg twice daily for two days prior to surgery. Prophylaxis for infective endocarditis was given on the day of surgery. In the operating room her baseline vitals were recorded and standard ASA monitoring was established. A 16G intravenous cannula and right radial artery catheter to monitor invasive blood pressure (IBP) secured. Her baseline vitals were heart rate (HR) 84/min, IBP of 147/89 mm Hg and SpO2 of 84%.

A loading dose of intravenous dexmedetomidine 1 mcg/kg was given over 15 min followed by a continuous infusion of 0.5 mcg/kg/h. Induction of anesthesia was with intravenous midazolam 1 mg, fentanyl 50 mcg, and ketamine 50 mg given slowly and titrated to effect. Intubation was facilitated by intravenous vecuronium 0.1 mg/kg. Anesthesia was maintained with 50% nitrous oxide in oxygen and sevoflurane 0.5–2% intermittently in circle system with controlled ventilation. A 16G peripherally inserted central venous catheter was secured in left arm with the tip of catheter at superior venacaval – right atrial junction confirmed radiologically. Surgery was performed with the patient in supine position with 30° head up and turned to left.

Twenty minutes post intubation patient developed hypotension, so dexmedetomidine infusion was tapered to 0.25 mcg/kg/h and dobutamine infusion was started at 5mcg/kg/min. Oxygen saturation was maintained between 80–94% and 100% oxygen was given when saturation dropped below 80%. Stable hemodynamics was achieved intraoperatively with mean arterial pressure between 70–100 mm Hg and HR between 60–80/min. Raised ICP in the intraoperative period was managed by hyperventilation to maintain end tidal CO2 at 30–35 mm Hg, head up position and intravenous mannitol 200 mL. Ventricular ectopics were noticed after 2h of surgery. A loading dose of intravenous amiodarone 300 mg was given followed by continuous infusion of 1 mg/min for 6 h. Serum potassium levels were low at 3.0 meq/L and hence potassium supplementation was done at 10 meq/h for 6h. Surgery lasted for a period of 4 h. Dexmedetomidine 0.25 mcg/kg/h was continued till extubation. Extubation was smooth after surgery with patient hemodynamically stable with HR of 92/min, IBP of 116/77 mm of Hg and O2 saturation of 84%. Patient was shifted to neurosurgical ICU with maintenance infusion of amiodarone and dobutamine. Oxygen support was given for 48 h, tapered and withdrawn. Tablet amiodarone 150 mg was started on second postoperative day. Sinus rhythm was restored on second postoperative day. Her further course in the hospital was uneventful and she was discharged home on fourteenth postoperative day.

DISCUSSION

Anesthetic challenges in the management of Ebstein's anomaly are intracardiac shunting, pulmonary hypertension, cyanosis, cardiac dysrhythmias, conduction system disorders such as WPW syndrome and infective endocarditis. These can result in congestive cardiac failure, sudden cardiac collapse, pulmonary, and systemic embolization.[6] A possible aetiology for brain abscess in EA is a paradoxical septic embolus through ASD or PFO from unknown infective focus.[7]

Anaesthetic problems

Prolonged induction time because of pooling of blood in the large right atrial chamber.[8]

A 20% incidence of serious supraventricular tachycardia following induction of anesthesia.[9]

Central venous catheter insertion may be hazardous as it can provoke life threatening cardiac arrhythmias and can precipitate bacterial endocarditis.[8]

Elimination of air bubbles in peripheral venous line and preventing air entry to veins at subatmospheric pressure is crucial to prevent iatrogenic paradoxical air emboli.

Poorly tolerated tachycardia or bradycardia, need to maintain the stable heart rate.

Hypoxia causes pulmonary vasoconstriction and increases right to left shunt.

Hypotension also increases right to left shunt.

Mannitol given to reduce ICP can cause fluid and electrolyte imbalance which can lead to hypotension and cardiac dysrhythmias.

Ketamine was used as an intravenous induction agent in the dose of 1 mg/kg as it is the ideal induction agent in patients with congenital heart disease with good or moderately limited hemodynamic reserve including those with pulmonary hypertension or cyanosis. It has minimal effect on pulmonary vascular resistance and does not increase right to left shunt.[10] The induction dose of Ketamine was reduced by the concomitant administration of Dexmedetomidine.

Dexmedetomidine, a highly selective α2 agonist was used during induction of anesthesia as it is a sympatholytic, anxiolytic, hypnotic, analgesic, and significantly reduces the requirement of analgesics and inhalational anesthetics in the intraoperative period.[11] It prevented the development of supraventricular tachycardia and hypotension following induction of anesthesia that occurs frequently in these patients. It has a favorable effect on reducing cerebral blood flow, ICP, and cerebral metabolic rate of oxygen.[12] It also facilitated smooth emergence from anesthesia and early neurological assessment in this patient.

Peripherally inserted catheter was preferred over the central venous catheter as the studies showed increase likelihood of arrhythmias with central catheter and the need for prolonged intravenous antibiotics therapy in this patient.[8] Meticulous care was taken to prevent air bubble entering intravenous lines. Dobutamine helped in improving cardiac output by offloading the heart and improving cardiac contractility as the patient was taking treatment for congestive heart failure. Amiodarone that was started in the preoperative period was continued intraoperatively to protect against life threatening refractory arrhythmias. Mannitol caused severe diuresis in our patient which eventually led to hypokalemia requiring potassium supplementation.

To conclude, Ebstein's anomaly is a rare congenital heart disease with varied clinical presentation and hemodynamic derangement which the anesthesiologist must be familiar. Meticulous planning, multidisciplinary approach, preoperative optimization, avoiding even minor hemodynamic fluctuation, selection, and titration of drugs to effect go a long way in successful management of these patients coming for incidental surgery.