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Effects of thermoregulatory vasoconstriction on pulse hemoglobin measurements using a co-oximeter in patients
Ken Yamaura1, Noriko Nanishi2, Midoriko Higashi1
1Operating Rooms, Kyushu University Hospital, Fukuoka 812-8582, Japan.
Study Objective:
To validate intraoperative pulse hemoglobin (SpHb) measurements in anesthetized patients with large forearm temperature - fingertip temperature gradients.
Design:
prospective and observational study.
Setting:
Operating room of a university hospital.
Patients:
28 patients undergoing surgery during general anesthesia, requiring arterial blood withdrawal.
Interventions:
Radial arterial blood pressure, forearm and fingertip skin surface temperatures, and SpHb were monitored.
Measurements:
Paired SpHb and arterial hemoglobin (Hb) measurements at different skin-surface temperature gradients.
Main Results:
A total of 175 paired SpHb and arterial Hb measurements were analyzed. The mean SpHb to arterial Hb differences in each group were 0.33 ± 1.41g/dL in the < 1°C group of the forearm temperature - fingertip temperature gradient, -0.31 ± 1.24g/dL in the 1 - 2°C group, - 0.59 ± 1.11g/dL in the 2 - 3°C group, and - 0.53 ± 0.87g/dL in the > 3°C group (P < 0.05). The percentage of nonmeasurable SpHb due to low perfusion state was 0% (0 of 115 paired measurements) in the < 1°C group, 6.7% (2 of 30 pairs) in the 1 - 2°C group, 16.7% (3 of 18 pairs) in the 2 - 3°C group, and 66.7% (8 of 12 pairs) in the > 3°C group.
Conclusion:
SpHb measured at fingertip was significantly affected by the perfusion state, with lower perfusion associated with lower SpHb. Thermoregulatory vasoconstriction affects measurement of SpHb.
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