Diagnostic blood loss in mechanically ventilated patients

Concern for the volume of blood loss resulting from diagnostic phlebotomy has been expressed in the literature for decades. Blood conservation strategies have been found to reduce the volume withdrawn for laboratory tests, but some patient populations may remain at risk.

This study examines the frequency of phlebotomy and volume of diagnostic blood loss for critically ill mechanically ventilated patients in a small community hospital.

The subjects were 43 critically ill adults who received mechanical ventilation for at least 24 hours during the first quarter of 2005. Data were collected from computerized medical records and included the frequency and types of laboratory tests performed over the course of hospitalization.

The mean total number of blood samples withdrawn was 69 (standard deviation = 59). The mean amount withdrawn per day was 16 mL (standard deviation = 7) with mean total volumes ranging from 57 to 1120 mL per patient. Four patients had more than 500 mL withdrawn. Chemistry analyses accounted for both the highest frequency of phlebotomy and the highest volume.

The daily volume of diagnostic blood loss for this population was less than the amounts previously reported in the literature, so there is some evidence of effectiveness of blood conservation strategies. However, some patients were still experiencing blood loss as the result of phlebotomy that may have been clinically significant. Additional strategies for reducing phlebotomy volumes are recommended.