The importance of blood sampling site for determination of hemoglobin and biochemistry values in major abdominal and orthopedic surgery

Study Objective: To determine whether sampling of blood from different sites influences laboratory results. Design: Prospective, double-blind study. Setting: University-affiliated hospital in Israel. Patients: 100 ASA physical status I, II, and III patients undergoing major orthopedic or colon surgery (total hip and revision of total hip replacement, colon resection, or radical cystectomy). Measurements: Blood was sampled simultaneously for hemoglobin, electrolytes, glucose, pH, blood gases, and lactate from three sampling sites (peripheral vein, central vein, and radial artery) at 5 time frames (after induction of anesthesia [baseline], one hr after induction of anesthesia, at the end of surgery, after one hr in the recovery room, and 4 hrs after surgery). At the same time points, recorded rectal temperature, mean arterial pressure, heart rate, and central venous pressure were recorded. Anesthesia, monitoring, and dwell volumes before sampling were standardized. Main Results: There were no significant differences between the results of hemoglobin, electrolytes, glucose, pH, and blood gases obtained from different sampling sites and at different time frames. Lactate level (mmol/L) was higher in peripheral venous blood than it was in either the central vein or radial artery (<0.05), and higher in central venous blood compared with arterial blood (P < 0.05; 2.04 ± 1.16, 1.74 ± 0.78, and 1.54 ± 0.68, respectively). Conclusion: Under stable hemodynamics and in the absence of hypothermia, serum lactate level was higher in peripheral venous blood than it was in the central vein or radial artery.