Temporal changes in the oxidation state in in vitro blood.

Area of Science:

• Biochemistry
• Hematology
• Physiology

Background:

• The in vivo formation rates of paramagnetic deoxyhemoglobin (Hb) and methemoglobin (MHb) in hemorrhage areas are not well understood.
• Establishing baseline concentrations and rates of change for Hb and MHb is crucial for understanding blood degradation in hematomas.

Purpose of the Study:

• To determine baseline concentrations and rates of change for Hb and MHb in human blood under controlled in vitro conditions.
• To investigate the stability of Hb and MHb in heparinized and clotted blood at physiological temperatures.
• To assess the capacity of red blood cell systems to reduce MHb back to Hb.

Main Methods:

• Human blood (heparinized and clotted) was incubated anaerobically at 37°C for 30 hours.
• Red blood cell systems' ability to convert MHb to Hb was tested.
• MHb concentrations were monitored in blood samples stored at 4°C and 25°C for up to 28 days.

Main Results:

• Moderate increase in Hb (15.5% average, 0.50%/hour) and slight increase in MHb (1.4% average, 0.044%/hour) in heparinized blood over 30 hours.
• MHb conversion to Hb occurred at a rate of 5.6%/hour.
• MHb levels remained within the normal range for at least 11 days in blood stored at lower temperatures.

Conclusions:

• Under basal in vitro conditions, Hb and MHb levels remain relatively low.
• Significant accumulation of Hb and/or MHb in acute in vivo hematomas suggests a role for intrinsic tissue factors.
• Further research is needed to elucidate the mechanisms driving Hb and MHb formation in vivo.