Uncorrected Tetralogy of Fallot's: Anesthetic Challenges.

Tetrology of Fallot's (TOF) is the most common cause of cyanotic congenital heart disease, and accounts for 10% of all congenital heart diseases. Right to left shunting and hyperviscosity of blood predisposes these patients to brain abscess. Perioperative management of these patients with uncorrected TOF for noncardiac surgery is a challenge for the anesthesiologists owing to the long-term effects of hypoxia and decreased pulmonary blood flow, resulting in considerable modification of the physiology and neurological complications. We are hereby reporting the anaesthetic management of an 8 year old child with uncorrected TOF presenting with multiple brain abscesses who underwent craniotomy with uneventful recovery. Copyright:

INTRODUCTION

Tetralogy of Fallot (TOF) is a leading cause of cyanotic congenital heart (CHD) disease (about 10% of total CHD) and constitutes 13%–70% of all brain abscess.[1] It consists of four components: presence of ventricular septal defect (VSD), overriding of aorta, right ventricular outflow tract obstruction (RVOT), and right ventricular hypertrophy (RVH).[2] Most of the literature published regarding brain abscess management in patients with uncorrected TOF covers either conservative or surgical management and very few reports have been found regarding anesthetic planning and management.[34] Pediatric population itself pose anesthetist to a challenging situation and this manifolds when associated with CHD disease (uncorrected) with neurosurgical intervention. Chronic hypoxemia and right-to-left shunting cause significant alterations in pathophysiology which makes these patients more vulnerable to perioperative complications such as hemodynamic instability, congestive heart failure, arrhythmias, cyanotic spells, acid–base imbalance, coagulation defects, along with abscess-induced seizures, meningitis, and raised intracranial pressure.[4] We are reporting here the anesthetic management of child with uncorrected TOF presenting with multiple brain abscesses who successfully underwent craniotomy with uneventful recovery.

CASE REPORT

An 8-year-old male weighing 19 kg, admitted in our hospital with complaints of severe headache, fever, and vomiting for 1 month and two episodes of seizures 2 days back. The patient was giving a history of easy fatigability, delayed developmental milestones as compared to his siblings, poor weight gain, and bluish discoloration of lips and tongue which become more pronounced during crying. Although his birth history and family history was normal. On general examination, the patient was having central cyanosis with grade 4 clubbing, tachycardia, and pan systolic murmur with palpable thrill all over precordium. His hemoglobin was 16 g.dL−1 with hematocrit 49.7% and normal coagulation profile. ECG showing right axis deviation with RVH and echocardiography suggestive of TOF with subaortic VSD, RVH, aortic override, and ejection fraction 67%. His computed tomography (CT) finding was three hypodense cystic lesions in the cerebral hemisphere in right and left frontoparietal lobe and right frontal lobe likely to be brain abscess with little mass effect, Grade II surrounding edema, and no midline shift [Figures 1-3]. In the view of severity of illness and the presence of multiple abscess, urgent surgery was planned. The patient was accepted as ASA physical status Class V, and informed consent was obtained.

Figure 1

NCCT head: Right frontal lobe abscess

Figure 3

NCCT head: Left frontoperital lobe abscess

NCCT head: Right frontoperital lobe abscess

In the operating room intravenous (i.v.) lines secured with 20 G i.v. canula and standard monitors attached. Antibiotic coverage given for infective endocarditis prophylaxis and 50 mg phenytoin and 20 g mannitol given to decrease cerebral edema. Preoperative ABG findings were pH 7.42, Pao262, Paco230, SpO275% at room air and preoperative pulse rate was 134/min and blood pressure 82/40 mmHg. After preoxygenation his SpO2 raised to 82%, and the patient was premedicated with 0.5 mg midazolam, 30 μg fentanyl, and 5 mg esmolol. Ketamine 50 mg, i.v., given for induction and tracheal intubation was facilitated with 2.5 mg of Vecuronium. Postintubation pulse rate was 140/min and blood pressure 96/50 mmHg. N2O: O2 was given in 50:50 ratio along with vecuronium and isoflurane (0.4%–0.6%) to maintain anesthesia and SpO2 reached up to 96%. Slight hyperventilation was done to decrease intracranial pressure and to prevent hypercarbia and acidosis which may increase pulmonary vascular resistance (PVR). Double-lumen CVP catheter inserted into the right internal jugular vein and left radial artery cannulation with 22G catheter was done. Dexmedetomidine infusion started at the rate of 0.1 μg.kg−1.h−1. Burr hole created in the right and left frontoparietal region and right frontal region by the neurosurgeon to drained out abscess. Surgery lasted for 110 min and 300 mL of blood lost which was replaced with packed cell. Fentanyl bolus was repeated after 45 min. After the completion of surgery when the patient become awake and started responding to verbal command, 0.2 mg glycopyrrolate and 1 mg neostigmine given and trachea extubated. Paracetamol infusion was given for postoperative analgesia. His postoperative ABG was pH 7.44, Pao266, Paco228, and SpO292% at 100% O2. The patient shifted to ICU and was observed for the next 24 h. His postoperative course was uneventful and was transferred to ward with SpO278% at room air.

DISCUSSION

Anesthetic management of a patient with uncorrected TOF for noncardiac surgery is a challenge to anesthesiologists and requires a thorough understanding of pathophysiology, events and effects of medications which can alter the magnitude of right to left shunting. Goal of anesthesia should be aimed at maintaining normovolemia, preventing hypoxemia, and avoiding decreases in systemic vascular resistance (SVR) and increases in PVR. Chronic hypoxemia in these patients lead to cyanosis, secondary polycythemia, hyperviscosity, and coagulation defects. Hyperviscosity causes sluggish blood flow in cerebral circulation that results in micro-thrombi formation. Right-to-left shunting bypasses the filtering of pulmonary capillaries and escapes the bacterial phagocytosis which results in seeding of infectious organisms in these areas of brain predisposing them to brain abscess. The management of brain abscess is usually done with 4–6 weeks of antibiotic treatment, but in cases of no regression of symptoms, significant mass effect with neurological deficits, multiple lesions, multiloculated lesions, or lesions larger than 2.5 cm, surgical management is indicated.[15] Another problem in these patients is cyanotic spells usually triggered by two mechanisms either decrease in SVR or spasm of cardiac muscle in the region of RVOT due to sympathetic stimulation (infundibular spasm). Any decrease in SVR is treated with α-adrenergic agonists such as phenylephrine or norepinephrine and i.v. fluids, whereas infundibular spasm is corrected with beta blockers such as propranolol or esmolol.

Ketamine is the preferred induction agent in TOF due to its property of increasing SVR which decreases right to left shunting.[6] We used the combination of fentanyl and ketamine for induction which improved oxygenation and saturation raised up to 96%. Esmolol was used during induction and maintenance to prevent tachycardia and infundibular spasm due to sympathetic stimulation. Dexmedetomidine, an α2agonist, was used for the maintenance of anesthesia because of its sedative, analgesic, and central sympatholytic property. The sympatho-inhibitory effects of dexmedetomidine balances with the cardio stimulatory effects of ketamine, thereby maintains a stable hemodynamic profile within normal physiological range, in cases with R-L shunting.[7] We used lower concentration to avoids the hypotension and bradycardia which occurs with higher doses of dexmeditomiditine.[89] At lower concentrations, administration of volatile anesthetics improves arterial oxygenation by causing relaxation of the muscle spasm in RVOT and decreases the total body oxygen consumption.[10] Hypovolemia and hypothermia may increase viscosity as well as increase in right-to-left shunting, so we kept the operating room temperature at slightly higher side and adequate hydration was maintained with warm i.v. fluids with CVP monitoring. Care was taken to make i.v. line free of air bubble because even small amount of air can lead to paradoxical embolism due to right-to-left shunting which may be life-threatening. All factors such as hypoxia, hypercarbia, acidosis, hypothermia, and increase in sympathetic tone were avoided to maintain PVR at the lower side. ABG was done before induction and after extubation as pulse oximetry is not a reliable indicator of oxygenation due to severe cyanosis. Management of pain is an important concern in these patients because increase sympathetic activity due to pain may trigger cyanotic spell in the perioperative period. We have given fentanyl bolus intraoperatively and paracetamol infusion postoperatively for pain control.

Noncardiac surgery in a patient with uncorrected TOF is reported to be associated with significantly higher mortality due to perioperative complications especially cyanotic spell.[11] Although dexmedetomidine has not been approved by FDA for pediatric patients, fewer cases have been reported in the pediatric population with CHD disease[7] and have shown that it can be effectively used for sedation in pediatric patients.[8]

CONCLUSION

Carefully administered anesthesia with meticulous planning, judicious use of drugs, combined with strict monitoring, and vigilance can make a safe outcome even in difficult cases.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.