Neurosurgery in a Child with Cyanotic Congenital Heart Disease (CCHD): Is Cardiac Grid Formulation the Panacea?

Cyanotic congenital heart disease (CCHD) is often associated with more than one cardiac anomaly with unique hemodynamic pattern, hence presenting a plethora of challenges to non-cardiac anesthesiologists. Understanding the pathophysiology of the cardiac lesion and constructing a cardiac grid can help in determining intraoperative hemodynamic goals and facilitate smooth perioperative management of such patients. This case report describes the anesthetic management of an infant with dextro-transposition of great arteries (dTGA) with a large atrial septal defect, ventricular septal defect, severe pulmonary stenosis, and patent ductus arteriosus posted for excision and repair of occipital meningocele and highlights the role of cardiac grid in clarifying anesthetic goals and ensuring better outcomes. Copyright:

INTRODUCTION

Perioperative management of a child with cyanotic congenital heart disease (CCHD) undergoing non-cardiac surgery presents a plethora of challenges for anesthesiologists. Each congenital cardiac lesion has unique hemodynamic goals.[1] The presence of more than one type of anomaly will further complicate the picture. A non-cardiac anesthetist can be baffled with the complicated physiology and finds it difficult to balance the intricate hemodynamic requirements of lesions with complex physiology. The unique hemodynamic requirements due to a particular cardiac lesion can be analyzed and depicted in a cardiac grid. Thus, formulating a cardiac grid will clarify the anesthetic goals, making the intraoperative drug choices easier. Managing according to the cardiac grid will render stable hemodynamics and optimal oxygenation, thereby obtaining better perioperative outcomes.[23] In this case report, we intend to report the anesthetic management of a case of CCHD posted for excision and repair of occipital meningocele and discuss the utility of cardiac grid in the intraoperative decision-making. Cardiac grid is described in standard cardiac anesthesia textbooks, but it is not common knowledge to a non-cardiac anesthesiologist. The purpose of this case report is to highlight the importance of a cardiac grid and its role in the perioperative management for the perusal of a neuroanesthesiologist.

CASE HISTORY

A 2-month-old female child was brought to the hospital with the complaint of swelling in the back of neck since birth and 1-day history of cerebrospinal fluid leak from the swelling. There was no associated fever, vomiting, seizures, or feeding difficulties. Local examination revealed 15*15 cm sized translucent swelling in the occipital region, which increased in size with cry and cough. Skin over the swelling was excoriated. Contrast enhanced magnetic resonance imaging showed occipital bone defect and a large meningocele with neural elements herniating through the defect. Echocardiography revealed situs ambiguous, dextro-transposition of great arteries (dTGA, i.e., aorta from the right ventricle (RV) and pulmonary artery from the left ventricle), common atrium, large ventricular septal defect (VSD), large patent ductus arteriosus (PDA), severe pulmonary stenosis (PS) (peak gradient of 79 mmHg), and a hypoplastic mitral valve. In view of risk of meningitis, the patient was posted for emergency surgery.

Pre-operative hemoglobin was 10.3 g/dL. The patient had one spike of fever after admission, and WBC counts were elevated (13,300/dL). Rest of the hematological and biochemical investigations were unremarkable. Baseline heart rate was 118/min and oxygen saturation on room air was 66%. The patient’s birth weight was 4 kg. But, pre-operative weight was 3 kg (indicating failure to thrive).

Operating room (OR) was prepared with pre-warming to 29°C, with code cart containing emergency drugs, defibrillator, and appropriately diluted vasoactive and anesthetic agents. On the OR table, patient’s head was positioned securely on an appropriately sized doughnut covered by sterile drapes. Intravenous cannula was already in place when the child was received in the OR. After pre-oxygenation, midazolam (0.25 mg) and glycopyrrolate (20 mcg) were given intravenously (i.v.). Anesthesia was induced with ketamine (6 mg) i.v. Rocuronium (3 mg) was given i.v. to facilitate endotracheal intubation (with 3.0 sized uncuffed endotracheal tube fixed at 8.5 cm at lip), and the child was placed on pressure-controlled ventilation. Anesthesia was maintained with ketamine infusion (50–70 mcg/kg/min) along with air and oxygen (fraction of inspired oxygen being 50%). Invasive arterial and venous access were secured, and arterial blood gas (ABG) was obtained to ascertain baseline values. End tidal carbon dioxide values and core temperature were monitored continuously. Surgery proceeded in prone position, and the course was uneventful. In view of low pre-operative hemoglobin, ongoing blood loss during the surgery was replaced by matched, leucocyte-depleted, packed red blood cells (RBCs) that were less than 1-week-old. Heart rate was maintained above 110 beats/min all through the procedure. Hemoglobin as measured by arterial blood sampling at the end of surgery was 11.9 g%. Acid–base status and electrolytes were within normal limits. The total duration of surgery was 1 h 15 min. The total duration of anesthesia was 3 h and 30 min. Total fluid intake was 45 mL of balanced crystalloid and 50 mL of packed RBC (to replace blood loss). After adequate reversal of neuromuscular blockade with neostigmine (0.15 mg) and atropine (0.03 mg), the child was extubated and shifted to the intensive care unit for post-operative care. Paracetamol suppository (80 mg) was applied in the intraoperative period. Post-operatively, the child received intravenous paracetamol (15 mg/kg) as sole analgesic.

The child was hemodynamically and neurologically stable for 24 h after surgery. However, further post-operative course was complicated by recurrent seizures and development of ventriculomegaly, resulting in neurological deterioration and reintubation. The child was eventually tracheostomized, weaned off from ventilator, and discharged from the hospital 4 weeks after the surgery.

Permission to publish the details of child’s perioperative course as a case report was requested from the parents and duly obtained.

DISCUSSION

The incidence of CCHD is 4 in 1000 live births[4] and is associated with significant perioperative morbidity and mortality. Hemodynamic management of a patient with complex CCHD poses unique challenges. Key aspects of tackling these lesions include an understanding of the direction of shunt flow and the factors affecting both cardiac output and oxygenation.[5] Understanding hemodynamic goals became easier by formulating a comprehensive cardiac grid for the specific lesion. The appropriate choice of the anesthetic and vasoactive agents depends on the cardiac grid.

“Cardiac grid” was first described by Moore[2] in 1981, along with depictions of grid for common lesions. Cardiac grid indicates the desired direction of change in each of the five hemodynamic variables (namely, heart rate, contractility, pre-load, and systemic and pulmonary vascular resistance), which can be achieved by appropriate use of various drugs from the anesthesiologist’s armamentarium.[36] In other words, it indicates the requirements of a particular patient to achieve stable hemodynamics and optimal oxygenation, thereby influencing outcome. How much ever complex the lesion might be, formulating a comprehensive cardiac grid for the specific anatomic defects demystifies the hemodynamic goals and guides an anesthesiologist to choose appropriate anesthetic and vasoactive agents.

Our patient had dTGA with common atrium, large VSD with PDA, and severe PS. The two important features of this lesion were that the RV is the systemic ventricle and adequate oxygenation is dependent on maintaining adequate pulmonary blood flow. Hemodynamics in our patient is depicted in Figure 1.[7] Cardiac grid and the subsequent anesthetic plan are depicted in Table 1.

Figure 1

Pathophysiology of the lesion and direction of shunting. Note the aorta (Ao) arising from the RV. PS at the origin of pulmonary artery decreases the blood flow to pulmonary circulation (Qp). L→R shunting of blood through VSD increases Qs. A fraction of Qs is shunted from Ao→PA through PDA, thereby maintaining Qp and oxygenation. Hence, the lesion is dependent on PDA to maintain oxygenation. Note the bidirectional shunting of blood between the two atria, in effect, behaving as a common atrium. LA: left atrium, RA: right atrium, VSD: ventricular septal defect, PDA: patent ductus arteriosus

Table 1

Cardiac grid showing hemodynamic goals (titrated to this lesion), their rationale, and ways to achieve each goal

Cardiac grid
	Goal	Rationale	Choice of agents
Heart rate	Avoid bradycardia	CO is heart-rate-dependent (130–150/min)	Atropine should be ready. Caution with drugs decreasing heart rate (opioids/phenylephrine)
Contractility	Maintain contractility	RV is systemic ventricle and responsible for CO	No cardiac depressants (propofol/ thiopentone/inhalational agents)
Systemic vascular resistance (SVR)	Avoid fall in SVR or acute rise	Decrease --> less blood is shunted to pulmonary circulation through PDA, hence less oxygenation Very high SVR: pressure load on RV leading to failure	No systemic vasodilators (inhalational agents >0.5 MAC) Vasoconstrictors like noradrenaline or ephedrine to be used judiciously, in titrated doses
Pulmonary vascular resistance (PVR)	Decrease PVR	This is important in maintaining oxygenation	Avoid hypoxia, hypercarbia, acidosis, high peak airway pressures Use higher FIO2 wherever possible. Maintain adequate depth of anesthesia and analgesia
Pre-load	Maintain pre-load	Decrease-->decrease CO (maintain central venous pressure of 10–12 mmHg)	Adequate hydration Avoid volume overload

We chose ketamine as an induction agent because of its ability to maintain systemic vascular resistance and heart rate. Good analgesia is an additional advantage. Other alternative was etomidate, but its use in young children is controversial.[8] Inhalational agents and propofol were avoided in view of their cardiac depressant action. Opioid induction can cause bradycardia and delay in post-operative recovery. Histamine release and hypotension with atracurium are rare and probably theoretical. Nevertheless, it was avoided.

Anesthesia was maintained with ketamine (50–70 mcg/kg/min). Use of inhalational agents (sevoflurane/desflurane) ≤ 0.5 minimum alveolar concentration (MAC) along with fentanyl (1 mcg/kg/h) was the alternative regimen. In our patient, even 0.1 MAC of inhalational agent resulted in bradycardia, hypotension, and decrease in oxygen saturation. Atropine (60 mcg i.v.) was given for bradycardia, and blood pressure improved with increase in heart rate. Supplemental analgesia was administered as paracetamol suppository.

In patients with CCHD, hematocrit is usually high in order to maintain oxygen delivery.[9] Baseline hemoglobin of 10.2 g% in our patient suggests a relative anemic state. Any further decrease in hemoglobin would have been detrimental to our patient as it leads to inadequate oxygen delivery. Hence, the blood lost during surgery was promptly replaced by transfusion of packed RBCs.

Blood supply to the RV occurs during both systole and diastole.[10] Hence, maintaining systolic blood pressure is as important as diastolic blood pressure to avoid intraoperative RV ischemia and shock (RV being systemic ventricle).

Cardiac output is heart-rate-dependent in infants. Bradycardia is almost always accompanied by hypotension. In our patient, heart rate was maintained above 110/min. There was no inotropic/vasopressor requirement. Dopamine would be the inotrope of choice in this patient (maintains heart rate and contractility without significant increase in pulmonary vascular resistance). If the patient had presented with septic shock, noradrenaline would be the agent of choice.

Appropriate measures were taken to avoid hypoxia, hypercarbia, and acidosis[79] (as ensured by regular ABGs). Pressure-controlled ventilation was used to avoid significant changes in intrathoracic pressure. Antisialagogue was used during induction to minimize secretions, thereby avoiding increased airway pressures and inadequate ventilation.

As aorta directly arises from the RV, the chances of paradoxical air embolism are very high. Care was taken to avoid any air bubbles in tubing or syringes.

CONCLUSION

It is prudent to have clear understanding of the pathophysiology of CCHD, and thereby formulating cardiac grid will make it easier for the anesthesiologist to individualize the perioperative management in such patients. Meticulous attention to the detail is essential for successful outcome.

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Conflicts of interest

There are no conflicts of interest.