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Reactive hyperemia in skin after cardiopulmonary bypass
E M Gruber1, B Schwarz, R Germann
1Department of Anesthesiology and Intensive Care Medicine, University of Innsbruck, Austria.
Objective:
To study reactive hyperemia (RH) using a transcutaneous PO2/PCO2 combination electrode heated to 37 degrees C and tissue reflectance spectrophotometry in patients before and after cardiopulmonary bypass (CPB) to determine whether microcirculatory function of skin is altered.
Design:
Prospective study.
Setting:
Anesthesiology and critical care unit of a university hospital.
Participants:
Eight patients undergoing elective CPB under mild hypothermia.
Interventions:
To produce RH, blood flow to the forearm was prevented by inflation of a cuff to 300 mmHg for an interval of 5 minutes.
Measurements And Main Results:
Measurements were obtained on the day prior to surgery (DPS), on the day of surgery (DOS) rewarmed to 37 degrees C in the intensive care unit (ICU), and on the first (POD 1) and the third postoperative days (POD 3). The following parameters were recorded: preocclusive baseline cutaneous PO2, and PCO2 (B-PtcO2, B-PtcCO2), and microvascular hemoglobin saturation (B-HbO2); postischemic peak of PtcO2, PtcCO2, and HbO2; and 10 minutes after release of the cuff occlusion posthyperemic PtcO2, PtcCO2, and HbO2. B-PtcO2 was 3.5 +/- 1.2 mmHg on DPS, 2.6 +/- 0.7 mmHg on DOS, 1.5 +/- 0.3 mmHg on POD 1, and 3.5 +/- 3.5 mmHg on POD 3. B-PtcCO2 increased significantly from 40.1 +/- 2.5 mmHg to 52.2 +/- 2.0 mmHg on DOS (p = 0.01) and to 48.9 +/- 3.6 mmHg on POD 1 (p = 0.02). On POD 3, B-PtcCO2 was 40.6 +/- 2.6 mmHg. B-HbO2 declined from a preoperative value of 42.4% +/- 8.6% to 37.1% +/- 14.7% on DOS and further to 21.7% +/- 4.8% on POD 1, which was significantly different (p = 0.03). On POD 3, B-HbO2 still remained lower (30.7% +/- 6.2%) compared with the preoperative value. RH (deltaPtcO2, deltaHBO2) was quantified as the differences between peak PtcO2, HBO2 and B-PtcO2, B-HBO2. DeltaPtcO2 was 13.0 +/- 2.3 on DPS, 11.3 +/- 2.9 on DOS, 12.6 +/- 2.6 on POD 1, and 11.5 +/- 3.5 on POD 3. DeltaHBO2 was 42.0 +/- 5.6 on DPS, 40.0 +/- 7.1 on DOS, 49.9 +/- 2.5 on POD 1, and 52.9 +/- 6.4 on POD 3. The elimination rate of carbon dioxide from skin (ECO2) was calculated as difference between peak PtcCO2 and PtcCO2 after 3 minutes of reperfusion divided by the difference between peak PtcCO2 and B-PtcCO2. ECO2 was 1.0 +/- 0.2 kPa/min on DPS, 0.7 +/- 0.1 kPa/min on DOS, and 0.8 +/- 0.1 kPa/min on POD 1 and POD 3.
Conclusion:
Cutaneous microcirculation assessed by RH is well preserved during the immediate postoperative period in patients undergoing uncomplicated coronary artery surgery with CPB.