Page 27 - CASA Bulletin of Anesthesiology Vol 9 (4) 2022 (3)

Vol. 9, No 4, 2022

and blood replacement therapy. CVP will increase when a patient is prone due to compression of
the inferior vena cava, decreased cardiac compliance, and a slight increase in intrathoracic
4, 5
pressure . The CVP in a patient with Fontan circulation might need to be in the high teens or
low 20s to provide adequate cardiac output in a prone position. It is critical to monitor the trends
of CVP, other than a specific number.

It should be noted that the CVP in a Fontan patient actually reflects mean pulmonary artery
pressure since the SVC and IVC are connected to the pulmonary arteries. Placement of CVP
monitor may cause pulmonary artery injury, paradoxical air embolism, thrombus in Fontan
pathway and central line associated bloodstream infection. The length of the central venous line
in the internal jugular vein must be carefully assessed so it is not placed too deep and in the
pulmonary artery. The decision on whether to use a CVP monitor perioperatively must balance
the risk of clot formation in the Fontan circuit against the benefit of obtaining adequate
information about volume status and therefore, cardiac output.

A noninvasive blood pressure cuff and intra-arterial catheters should not be placed on or in
an arm on the side of a previous BT shunt of the patient as this may lead to falsely low blood
pressure measurements in that arm.

7. Discuss the differential diagnoses and treatment for intraoperative hypoxemia.

Other than the common causes, such as endobronchial intubation, bronchial spasm, and
circuit disconnection, acute elevation of PVR causing right to left shunting across a fenestration
or a baffle leak should be considered in Fontan patients. Techniques to decrease PVR and
improve oxygenation include optimizing mechanical ventilation (increase FiO2, correct
hypercarbia, avoid excessive positive pressure), correcting hypothermia and acidosis, and
administering phosphodiesterase inhibitors such as milrinone and /or using inhaled nitric oxide.

8. Describe transfusion threshold in patients with Fontan physiology in PSF.

Children with Fontan physiology undergoing PSF may result in significantly higher
6, 7
intraoperative blood loss and may even be more than an entire blood volume mainly due to
increased CVP.
Techniques to minimize intraoperative blood loss and allogeneic transfusion include
autologous blood donation preoperatively or intraoperatively, appropriate prone positioning, an
appropriate operating table (free of pressure to intra-abdominal organs and IVC), intraoperative
blood salvage, controlled hypotension, and use of intravenous antifibrinolytic agents (epsilon-
aminocaproic acid or tranexamic acid). Due to the higher baseline CVP required to maintain the
Fontan circulation and diminished cardiac functional reserve, controlled hypotension is not
recommended in single ventricle patients. Transfusion threshold commonly used as keeping
HCT ≥ 30% and mean arterial pressure ≥ 60 - 65 mmHg.

9. Discuss the extubation plan for patients with Fontan physiology.

Extubation in the operating room at the end of the surgery is optimal for a patient with
Fontan physiology. Changing from mechanical to spontaneous ventilation should improve

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