Abstract
OBJECTIVESTo document cerebral saturation in response to alterations in mechanical ventilation in infants with bidirectional superior cavopulmonary connection.DESIGNProspective study.SETTINGPediatric cardiovascular intensive care unit.PATIENTSChildren with functional single ventricle who have undergone bidirectional superior cavopulmonary connection.INTERVENTIONSWe measured cerebral oxygenation using near-infrared spectroscopy in response to three ventilator interventions (change 50% from baseline): a) hyperventilation with increased tidal volume; b) hyperventilation with increased respiratory rate; and c) hypoventilation by decreased respiratory rate. Physiologic variables documented were cerebral oxygenation index (rSO2i), arterial pH, and PCO2.MEASUREMENTS AND MAIN RESULTSTen patients (eight males and two females) underwent placement of bidirectional superior cavopulmonary connection. There were no mortalities. The mean age was months 8.6 (+/-2.1) months. Hyperventilation (tidal volume increase) caused an increase in pH from 7.35 to 7.42 (p = .001), a decreased PCO2 from a baseline 45.9 to 33.9 mm Hg. (p = .002), a decrease in rSO2i from 64.4 to 52.0 (p < .001), and a decreased Po2 from 52.8 to 46.9 mm Hg (p = .008). Hyperventilation (respiratory rate increase) caused increased pH from 7.35 to 7.39 (p = .002), decreased PCO2 from a baseline 41 to 37 mm Hg. (p = .021), decreased rSO2i from 65.9 to 56.7 (p = .007), and decreased PO2 from 54.9 to 48.9 mm Hg (p = .006). Hypoventilation (respiratory rate decrease) did not change pH did not change from baseline 7.35. The PCO2 increased from 40.8 to 42, and the rSO2i increased from 64.0 to 68.6 (p = .004).CONCLUSIONSHyperventilation can potentially cause a decrease in cerebral oxygenation and should be avoided in children with bidirectional superior cavopulmonary connection. Normoventilation and mild respiratory acidosis, however, preserve cerebral oxygenation in these patients.