BACKGROUND: Respiratory dysfunction due to uneven distribution of ventilation to perfusion1 and increased shunting of venous blood through the lungs2 is a major cause of morbidity following cardiopulmonary bypass (CPB). This study compares changes in shunting (Qs/Qt) and deadspace ventilation (Vd/Vt) between mitral valve replacements (MVR) vs CABG. METHODS: A prospective cohort study was approved by the IRB and to date data was collected on seven patients (4 CABG. 3 MVR). Patient selection criteria included EF > 45% and absence of significant pulmonary disease. CABG patients had minimal mitral régurgitation and MVR patients had moderate to severe MVR. Confounding effects of cardiopulmonary bypass duration and variation in hemodynamics were controlled for. All data were collected after induction of general anesthesia and trachéal intubation (with mechanical ventilation) and prior to opening the chest cavity. Hemodynamic profiles and deadspace/shunt values were recorded before and 1, 2, and 4 hours after CPB. Vd/Vt was measured using the CCXSMO-plus monitor (Novametrix Inc., Walltngford, CT), while Qs/Ql was calculated using the shunt equation: Qs/Q = [P(A-a)O, x (0.0031)] [P(A-a)O, x (0.0031)] - C(a-v)O: RESULTS: MVR patients had higher Qs/Qt than CABG patients at all times, whereas Vd/Vt values differed minimally between procedures and after vs before CPB. Despite a progressive decrease post-CPB. Qs/Qt remained markedly elevated for up to 4 hours. CONCLUSIONS: Higher Qs/Qt values predominate in patients with MR before and after repair as compared to patients who undergo revascularization procedures. Measures to optimize cardiac function and minimize pulmonary shunting may expedite patient recovery in the postoperative period.
|Original language||English (US)|
|Journal||Critical care medicine|
|Issue number||1 SUPPL.|
|State||Published - Dec 1 1998|
ASJC Scopus subject areas
- Critical Care and Intensive Care Medicine