Cardiopulmonary bypass and forearm blood flow.
OBJECTIVE
To assess the effect of cardiopulmonary bypass (CPB) on muscle blood flow (MBF) when measured in the forearm by venous occlusion plethysmography.


METHODS
This was a prospective study.


METHODS
Operating room area of a tertiary care university medical center.


METHODS
Twenty-seven patients (25 men and 2 women), aged 62 +/- 1.5 years, undergoing elective coronary bypass grafting.


METHODS
Measurements were made during the surgical procedure: before, during cold and warm, and after discontinuation of CPB.


RESULTS
Changes in forearm blood flow (FBF), derived forearm vascular resistance (FVR), mean arterial pressure (MAP), and cardiac output (CO) were evaluated by repeated measures analysis of variance. The control FBF (measured before CPB) was found to be approximately 50 percent lower than that previously reported for awake volunteers and patients. The FVR was similarly higher. From these low values, the FBF increased significantly (p < 0.001) during normothermic bypass and after CPB. Forearm vascular resistance decreased significantly (p < 0.001) throughout the cold, warm, and postbypass periods. Only during the warm and the postbypass periods did FBF and FVR reach normal values. Mean arterial pressure decreased significantly (p < 0.01) throughout. There was no statistically significant association between any of the variables and FBF or FVR. After correcting for patient and surgical phase variability, only MAP had a statistically significant effect (p = 0.042) on FVR; blood temperature, skin temperature, hematocrit level, PaCO2, serum potassium, and systemic vascular resistance (SVR) had no effect on either FBF or FVR when tested singly or in combination. When correction for multiple comparisons was applied, the lowest probability value became greater than 0.25. There was no correlation between combinations of covariates and FBF or FVR after adjustments for the surgical phase of the study either.


CONCLUSIONS
These findings indicate that the increase in MBF seen during warm and the post-CPB periods is only a recovery toward normal blood flow. The role of this change in the low SVR that usually accompanies CPB is equivocal.
Department of Anesthesia, Bowman Gray School of Medicine, Winston-Salem, NC 27157-1009.
A L
AL
Pauca
S L
SL
Wallenhaupt
N D
ND
Kon
W Y
WY
Tucker
D001794:Blood Pressure; D002302:Cardiac Output; D002315:Cardiopulmonary Bypass / Q000379:methods; D001026:Coronary Artery Bypass; D017558:Elective Surgical Procedures; D005260:Female; D005542:Forearm / Q000098:blood supply*; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D011446:Prospective Studies; D017534:Radial Artery / Q000502:physiology; D012039:Regional Blood Flow; D014655:Vascular Resistance