Role of Urinary PO2 Analysis During Conventional Versus Conventional and modified Ultrafiltration Techniques in Adult Cardiac Surgery

Background

Medullary hypoxia is the initial critical event for kidney injury during cardiopulmonary bypass, and therefore urinary PO₂ with its potential of detecting medullary oxygenation for its management. Therefore, we tested the role of urinary PO₂ in predicting kidney injury in those undergoing conventional versus combined (conventional and modified) ultrafiltration during cardiac surgery in adults.

Methodology

We prospectively evaluated 32 adults between 18 and 65 years of age undergoing elective on-pump cardiac surgery with ejection fraction >35% by conventional (group C) versus combined ultrafiltration (group CM). Urine samples were analyzed for PO₂ after induction, 30 min, 3 h, and 6 h post filtration along with blood urea and serum creatinine after induction, at 6 h, 24 h, and 48 h post filtration. Demographic variables, cardiopulmonary bypass duration, flow rates, inotropic score, ventilation duration, diuretic use, and intensive care unit (ICU) stay were assessed between two groups.

Results

Both the groups (16 in each group) had comparable urinary PO₂ after induction (P = 0.387) with significant decrease in group C at 30 min, 3 h, and 6 h post filtration (P < 0.05). There was a statistically significant increase in serum creatinine (mg/dL) at 48 h in group C compared with group CM (1.57 vs. 1.25, respectively; P ≤ 0.05). There was an increased diuretic usage and length of ICU stay in group C.

Conclusion

Combined ultrafiltration technique had renoprotective effect in cardiac surgery analyzed by urinary PO₂ levels.