Page 26 - CASA Bulletin of Anesthesiology Vol 9 (4) 2022 (3)

CASA Bulletin of Anesthesiology

2. What are the major determinants in Fontan circulation?

One of the key features of Fontan circulation is a higher central venous pressure (CVP,
usually 10-14 mmHg) required to maintain pulmonary circulation and cardiac output. The
transpulmonary pressure gradient cross Fontan pathway (e.g., the pressure difference between
CVP and the common atrial pressure) is the driving force to maintain blood flow through the
pulmonary vasculature resulting in adequate oxygenation and cardiac output. Determinants of
the Fontan circulation include systemic ventricular function, atrioventricular valve competency,
cardiac rhythm, systemic venous pressure and volume, pulmonary vascular pressure, and
resistance.

3. Describe the general anesthetic principals to manage a patient with Fontan physiology for non-
cardiac surgery.

The general principles include maximizing preload, minimizing myocardial depression
caused by medications and/or inhalational agents, maintaining sinus rhythm, and avoiding
increases in pulmonary vascular resistance (PVR) such as hypoxia, hypercarbia, acidosis, high
positive pressure mechanical ventilation, and poorly controlled pain or surgical stimulation.

4. What are the options for induction of anesthesia?

Either intravenous or inhalational techniques can be safely used for induction in a well-
compensated Fontan patient. Medications with minimal cardiac depressive effects, including
etomidate, ketamine, midazolam and opioids, can be safely used for intravenous induction.
propofol may be used, however, it may cause myocardial depression, afterload reduction and
venous dilation, which may not be well tolerated by these patients. If used, it is imperative to
carefully titrate to effect with monitoring during induction. When intravenous access is not
obtained preoperatively, careful titration of sevoflurane is commonly used. A bolus of 5-10cc/kg
crystalloid before or during induction may be given to improve hemodynamic stability.

5. Is spontaneous ventilation better than mechanical ventilation in patients with a Fontan
circulation?

Spontaneous ventilation is preferentially used during most uncomplicated surgeries, when
possible, in patients with Fontan physiology, because it generates negative intrathoracic pressure,
which enhances venous return and hemodynamic performance in these patients. Mechanical
ventilation can lead to less favorable hemodynamics due to increased intrathoracic pressure and
decreased central venous return. However, in certain types of surgeries, adequate spontaneous
ventilation is not possible, such as posterior spinal fusion (PSF) or laparoscopic intra-abdominal
procedures, and hypoventilation with associated hypercarbia, hypoxia and atelectasis, all of
which can lead to an increased PVR, decreased cardiac output. Mechanical ventilation with low
mean airway pressures should be considered and normocarbia should be the goal.

6. Is there a need to place a CVP monitor in invasive procedures?

A CVP line is rarely placed in Fontan patients for non-cardiac surgeries, however, in some
very extensive surgeries, such as PSF, following CVP trends can be useful for guiding volume

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