Decreased incidence of low subcutaneous tissue oxygen tension in "well-resuscitated" trauma patients

Introduction: Low subcutaneous oxygen tension (PsqO2) increases the risk of impaired wound healing and infection in surgical patients.¹ A previous study in "well-resuscitated" trauma patients showed a high incidence (35-78%) of low PsqO2.². Hypovolemia, hypothermia and pain result in low PsqO2 due to autonomic vaso-constriction. We thus began a randomized interventional study to evaluate the effect of forced air warming, fluid administration, and pain control on increasing PsqO2 and improving wound outcome and overall outcome in trauma patients. Methods: With informed consent, 1 female and 7 male adults with ISS 16-45 meeting resuscitation criteria within 24 hrs of injury (SBP ≥ 90mm Hg, IV fluid rate ≤ 250 cc/hr, and base deficit <5) were randomized to treatment (Rx) and control (C) groups (3 C, 5 Rx). PsqO2 and subcutaneous tissue temperature (Tsq) were measured in the lateral upper arm every 12 hrs for 6 measurements. At each time point, FIO2 was doubled and PsqO2 was remeasured in 30 min. Adequate response to increased FIO2, and thus adequate tissue perfusion based on prior studies³, was defined as ≥20% rise in PsqO2. Rx consisted of forced air warming for Tcore <36.5°C or Tsq<32°C (tonometer arm protected) and IV analgesics before baseline measurement, and up to 1500 ml fluid bolus if inadequate response. PsqO2 was remeasured 30 min after fluid Rx. Results: No significant differences were found between groups for (median; Mann Whitney): age, lowest intraoperative core temperature (C 34.7°C. Rx 34.6°C). ending intraoperative core temperature (C 36.4°C, Rx 37°C), OR IV fluids (C 3.3 Liters. Rx 33.5L) and ICU MSO4 equianalgesic dose (C 214 mg, Rx 173mg). Only 1 Rx subject failed to respond (at 1/5 time point): thus, data for both groups were combined. Inadequate response to increased FIO2 occurred in 28.6% of subjects at 0 hr, 12.5% at 12 hrs, 14.3% at 24 hrs, 25% at 36 hrs, 14.3% at 48 hrs, and 25% at 60 hrs. Discussion: Contrary to the previous report, inadequate response of PsqO2 was uncommon in this sample. Potential reasons for this include: 1. routine use of intraoperative forced air warming resulting in less PO hypothermia, and 2. improved ICU pain management (pain Rx algorithm instituted during study period). This improvement in PsqO2 in these patients may translate to improved wound and other patient outcomes but the sample was too small to evaluate this effect.