Anesthetic considerations in a child with unrepaired D-transposition of great arteries undergoing noncardiac surgery.

D-transposition of great arteries (D-TGA) is the most common cyanotic congenital heart disease diagnosed at birth. There is ventriculoarterial discordance leading to parallel circulation. The postnatal survival depends on intercirculatory mixing of oxygenated and deoxygenated blood at various levels through atrial septal defect, ventricular septal defect or patent ductus arteriosus. The anesthesiologist must have an understanding of concepts of shunting and other long-term consequences of transposition of great arteries (TGA) in order to tailor the anesthetic technique to optimize the hemodynamic variables and oxygenation in the perioperative period. The preoperative evaluation includes echocardiography to delineate the type of TGA, associated lesions and extent and direction of shunts. Oxygen saturation is influenced by the ratio of pulmonary vascular resistance (PVR) to systemic vascular resistance. Thus, care should be taken to avoid an increase in PVR which can lead to decreased pulmonary blood flow leading to hypoxia. We report a case of an 8-year-old child with unrepaired D-TGA, who presented to us for craniotomy for drainage of brain abscess.

INTRODUCTION

Transposition of great arteries (TGA) is the most common cause of cyanotic congenital heart disease (CHD) at birth, with an incidence of 1 in 2300–1 in 5100 live births.[1] There is ventriculoarterial discordance leading to parallel circulation and postnatal survival depends on intercirculatory mixing of oxygenated and deoxygenated blood at various levels through atrial septal defect (ASD), ventricular septal defect (VSD) or patent ductus arteriosus. The presence of CHD increases the risk of perioperative mortality in children undergoing noncardiac surgery owing to ventricular dysfunction, chronic hypoxia, polycythemia, and infective endocarditis.[2] However, very limited data are available regarding the potential anesthetic risks for patients with unrepaired complex heart defects. We report a patient with unrepaired D-transposition of great arteries (D-TGA) who underwent craniotomy for drainage of brain abscess.

CASE REPORT

An 8-year-old (21 kg) boy presented to us with the deterioration of consciousness, seizures, and vomiting for 8 days. On clinical examination, the child was drowsy with Glassgow Coma Score of 12, had central cyanosis, grade II clubbing, fever, and bradycardia. Cardiovascular system examination revealed single loud second heart sound. Child's history was remarkable for diagnosis of cyanotic CHD at birth and episodes of cyanotic spells on crying and exercise. His hemoglobin was 146 g/L, hematocrit 56%, and total leukocyte count 16.0 × 109/L. Other hematological and biochemical investigations including platelet count and coagulation profile were within normal limits. Chest radiograph showed "egg-shaped" cardiac shadow and increased pulmonary vascular markings [Figure 1]. Right axis deviation and right ventricular hypertrophy were seen in electrocardiography. His computerized tomography scan showed brain abscess (44 mm × 32 mm) in right thalamic-ganglion region with 6.6 mm midline shift. Due to worsening of symptoms 3 months back cardiology consultation was done and his echocardiography revealed D-TGA with discordant ventricular – great artery relation, fossa ovalis ASD with bidirectional shunt, inlet VSD with bidirectional shunting, and infundibular pulmonary stenosis (PS) with gradient of 64 mmHg. No surgical correction was done, and the patient was not taking any medications at the time of presentation.

Figure 1

Chest radiograph showing posterior-anterior view showing “egg-shaped” cardiac shadow and increased pulmonary vascular markings

Emergency craniotomy and drainage of brain abscess were planned under general anesthesia. The preoperative temperature was 37.8°C, heart rate 55/min, blood pressure 96/70 mmHg, and oxygen saturation (SpO2) 82% on room air. Intramuscular paracetamol 15 mg/kg (2 ml) was given preoperatively as the patient had a fever. After preoxygenation SpO2 increased to 93%. Injection normal saline was started through 21 gauge intravenous (i.v.) cannula after meticulously flushing to remove any air bubbles. Ceftriaxone 50 mg/kg i.v. was given 30 min before skin incision. Patient was premedicated with i.v. glycopyrrolate 0.2 mg, midazolam 1 mg, and fentanyl 2 µg/kg. Induction and intubation were done using thiopentone sodium titrated to effect and rocuronium 0.9 mg/kg, respectively. Patient was intubated with cuffed endotracheal tube size 6.0 mm without much hemodynamic variation or hypoxia. Anesthesia was maintained using sevoflurane in 100% oxygen to maintain a minimum alveolar concentration (MAC) of 1.2. Volume control ventilation without positive end-expiratory pressure (PEEP) was used and end-tidal carbondioxide was maintained between 30 and 35 mmHg. Injection mannitol 0.5 gm/kg i.v. was given after adequate hydration. Hemodynamic parameters and SpO2 remained stable during the entire course of surgery, which lasted for 40 min. All anesthetic agents were stopped; neuromuscular blockade was reversed using neostigmine, and glycopyrrolate and the child was extubated after the return of adequate muscle power. After ensuring the patient was hemodynamically stable and maintaining SpO2 above 90% with oxygen by venturi mask he was transferred to the intensive care unit. The postoperative course was uneventful, and the child was discharged on the seventh postoperative day with advice to consult a pediatric cardiologist.

DISCUSSION

First of the major anomalies present in this patient was TGA, major findings associated with this defect include an aorta emanating from the right ventricle and a pulmonary artery arising from the left ventricle. This condition is incompatible with survival unless there are additional lesions, which allow adequate mixing of oxygenated and deoxygenated blood. In our patient, TGA was associated with VSD, which facilitated this mixing. The third anomaly was left ventricular outflow tract obstruction (LVOTO). Due to the combination of these three lesions the child had cyanosis at birth and hypercyanotic spells during crying and exercise due to dynamic subpulmonary stenosis. It is interesting to note that the presence of LVOTO prevented the development of congestive heart failure (CHF) in spite of the presence of large VSD.[1] Factors associated with increased perioperative risk in children with unrepaired CHD undergoing noncardiac surgery include the presence of complex CHD, CHF, pulmonary hypertension, cyanosis, and type of surgery. A review of several case reports of patients with unrepaired CHD undergoing anesthesia for noncardiac surgery highlighted similar interventions: Maintenance of intravascular volume, avoidance of precursors to acidosis such as hypothermia, hypercarbia, and hypotension, and minimization of intracardiac shunting.[34] Our case was challenging as the patient had a complex CHD along with raised intracranial pressure (ICP).

Thorough preoperative evaluation includes birth history, history of cyanotic spells, medical, and surgical treatment received and cardiovascular and respiratory system examination. Complete blood count is done preoperatively to know the extent of secondary erythrocytosis and coagulation profile is done to rule out coagulation abnormalities that may be associated with cyanotic CHD. Preoperative SpO2, chest radiography, electrocardiography, and echocardiography are a must before anesthesia.[5]

Avoiding prolonged preoperative fasting and maintaining adequate hydration are important to prevent hyperviscosity. Large bore i.v. cannula should be secured, and all lines flushed to avoid air bubbles as these patients are at high-risk of paradoxical embolism due to the presence of bidirectional shunts. Appropriate endocarditis prophylaxis should be administered 30 min prior to skin incision. SpO2 is influenced by the ratio of pulmonary vascular resistance (PVR) to systemic vascular resistance (SVR). When PVR decreases, increased pulmonary blood flow results in higher arterial SpO2. Whereas when PVR increases CHF improves at the cost of increasing cyanosis. Thus, challenge for anesthesiologist is to modulate PVR and SVR by pharmacological and ventilatory means in order to achieve a balance between CHF and hypoxia. The pulmonary hypertensive crisis was prevented by hyperventilation with 1.0 fractional inspired oxygen concentration, avoidance of sympathetic nervous system stimulation with adequate analgesia and anesthetic depth, maintenance of normothermi, a and minimization of intrathoracic pressure by avoiding PEEP.[6] Bradycardia in this patient was owing to raised ICP, thus glycopyrrolate was given in premedication. Fentanyl was chosen as it causes least hemodynamic variation and blunts pulmonary vasculature reactivity. IV induction was preferred as inhalational induction may be prolonged in the presence of PS and right to left shunting. Ketamine was avoided because of the presence of raised ICP, and thiopentone sodium was used for induction as it has no effect on PVR and is cerebroprotective. Patient was intubated using rocuronium to avoid an increase in ICP. Anesthesia was maintained with sevoflurane keeping in mind that systemic to pulmonary blood flow ratio is not altered and left ventricular systolic function is maintained at 1–1.5 MAC of sevoflurane in 100% oxygen when used in CHD patients.[7] Nitrous oxide was not used as it is shown to increase PVR and my also lead to expansion of air bubbles, which may be inadvertently infused or entrained via the surgical site. The intraoperative decrease in SVR due to anesthetic agents can be minimized with titration of dose to the effect of anesthetic agents, maintenance of intravascular volume, and use of direct acting alpha agonists like phenylephrine. Thus, the present case shows that with thorough understanding of pathophysiology and meticulous planning to prevent possible complications, patients with complex CHD may be successfully anesthetized for noncardiac surgery without incident.

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