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Hypoventilation improves oxygenation after bidirectional superior cavopulmonary connection.
Scott M Bradley1, Janet M Simsic, Denise M Mulvihill
1Division of Cardiothoracic Surgery, Medical University of South Carolina, 96 Jonathan Lucas St., Charleston, SC 29425, USA. bradlesm@musc.edu
The Journal of Thoracic and Cardiovascular Surgery
|October 21, 2003
Summary
Hypoventilation improves oxygenation in patients after bidirectional superior cavopulmonary connection. This strategy increases cerebral blood flow and may be useful post-surgery.
Area of Science:
- Cardiovascular Surgery
- Pediatric Cardiology
- Critical Care Medicine
Background:
- Systemic hypoxemia can complicate bidirectional superior cavopulmonary connection.
- Previous research indicates hyperventilation worsens oxygenation post-surgery.
- Hyperventilation-induced hypocarbia reduces cerebral, superior vena caval, and pulmonary blood flow.
Purpose of the Study:
- To investigate if hypoventilation improves oxygenation after bidirectional superior cavopulmonary connection.
- To explore the physiological mechanisms behind hypoventilation's effects on oxygenation.
Main Methods:
- Prospective study of 15 pediatric patients (median age 8.0 months) post-bidirectional superior cavopulmonary connection.
- Patients were studied in the ICU within 8 hours of surgery under sedation and mechanical ventilation.
- Cerebral blood flow velocity measured by transcranial Doppler; pH-buffered hypoventilation induced with sodium bicarbonate.
Main Results:
- pH-buffered hypoventilation led to hypercarbia (mean Pco(2) 58 mm Hg).
- Mean arterial Po(2) increased from 50 to 61 mm Hg (P <.05) and oxygen saturation from 86% to 90% (P <.05).
- Cerebral blood flow velocity increased (37 to 55 cm/s; P <.05), with decreased arteriovenous oxygen difference, indicating increased cerebral blood flow.
Conclusions:
- Hypoventilation significantly improves systemic oxygenation in early post-operative patients.
- Increased cerebral blood flow due to hypoventilation-induced hypercarbia is the likely mechanism.
- Hypoventilation is a potential clinical strategy for managing post-operative hypoxemia.