Disposition and pharmacodynamics of propofol during isovolaemic haemorrhage followed by crystalloid resuscitation in humans.
OBJECTIVE
The purpose of this study was to estimate the changes in unbound propofol concentration and pharmacodynamics of propofol during isovolaemic haemorrhage followed by crystalloid resuscitation.


METHODS
Ten patients undergoing measure elective surgery were enrolled in this study. Anaesthesia was maintained by 60% nitrous oxide in oxygen, fentanyl 10-20 microg kg-1 and an infusion of propofol at 8 mg kg-1 h-1 until the end of the operation. Radial arterial samples were collected for measurement of propofol concentration just before the start of the operation, and at the point when blood loss was >10 ml kg-1, 20 ml kg-1 and 30 ml kg-1. Cardiac output (CO), haemoglobin values and plasma concentrations of albumin were also determined. Patients were resuscitated with lactated Ringer's solution to maintain a mean arterial blood pressure (+/-20% of prehaemorrhage). Bispectral index (BIS) was measured continuously.


RESULTS
Mean blood pressure, heart rate and CO were well maintained during the operation in all patients. Haemoglobin values and plasma albumin concentrations decreased significantly during surgery. There were no significant differences in total propofol concentrations across the time points. The unbound propofol concentration was increased from 0.10+/-0.040 microg ml-1 to 0.17+/-0.041 microg ml-1 after the haemorrhage of 30 ml kg-1 (P<0.05). BIS was significantly decreased from 47+/-5.9 to 39+/-3.7 (P<0.05) after the haemorrhage of 30 ml kg-1.


CONCLUSIONS
The hypnotic potency of propofol is increased during isovolaemic haemorrhage in crystalloid resuscitated patients even if CO is maintained.
Department of Anaesthesiology, Gunma University, Graduate School of Medicine, 3-39-22 Showa-machi, Maebashi 371-8511, Japan.
Eri
E
Takizawa
Daisuke
D
Takizawa
Haruhiko
H
Hiraoka
Shigeru
S
Saito
Fumio
F
Goto
D000368:Aged; D018686:Anesthetics, Intravenous / Q000008:administration & dosage / Q000097:blood*; D016063:Blood Loss, Surgical / Q000503:physiopathology*; D001794:Blood Pressure / Q000502:physiology; D002302:Cardiac Output / Q000502:physiology; D004912:Erythrocytes / Q000378:metabolism; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D007262:Infusions, Intravenous; D008297:Male; D008875:Middle Aged; D015742:Propofol / Q000008:administration & dosage / Q000097:blood*; D012151:Resuscitation; D012709:Serum Albumin / Q000032:analysis
D018686:Anesthetics, Intravenous; D006454:Hemoglobins; D012709:Serum Albumin; D015742:Propofol