Which of the following is monitored hourly to assess fluid status after CABG?

• A. Urine output
• B. Blood pressure
• C. Hematocrit
• D. Respiratory rate

Answer: (A)

Monitoring hourly urine output after CABG focuses on real-time fluid balance and renal perfusion. It’s the most direct indicator of how circulating volume is supporting kidney function; a consistent output above about 0.5 mL/kg per hour (roughly 30 mL/hour in an average adult) suggests adequate perfusion and fluid status. If urine output drops, it points to potential hypovolemia or reduced kidney blood flow, prompting fluid adjustments or further assessment. Blood pressure reflects overall perfusion but can be maintained with vasopressors even when kidney perfusion isn’t ideal. Hematocrit can be affected by blood loss and IV fluids and doesn’t provide timely, direct information about current fluid status. Respiratory rate can rise with fluid overload or lung congestion but is influenced by many factors and isn’t a direct measure of volume status.