Intravenous anesthesia inhibits leukocyte-endothelial interactions and expression of CD11b after hemorrhage.
Hemorrhage increases adhesion of leukocytes to the venular endothelium, mediated by increased expression of the Mac-1 integrin complex (CD18/CD11b) present on leukocytes. Anesthetic agents may possess anti-inflammatory properties. Hence, this study determined the effects of i.v. anesthesia on leukocyte adhesion after hemorrhage in relation to expression of CD11b.


METHODS
Male Wistar rats were (n = 57) anesthetized i.v. with propofol (Diprivan) and fentanyl, ketamine, or thiopental. During anesthesia, 10% of total blood volume was removed and intravital microscopy used to observe the rat mesentery and measure leukocyte (neutrophils) rolling and adhesion in postcapillary venules (15 - 25 microm). Flow cytometry was also used to determine CD11b expression on neutrophils from blood removed at the end of these experiments (n = 25) or blood incubated with anesthetic agents and activated with platelet activating factor ex vivo (0.1 micromol/L) (n = 24).


RESULTS
Hemorrhage increased leukocyte adhesion (stationary count per 150 microm) in rats anesthetized with thiopental (baseline, 3.4 +/- 1.2; hemorrhage, 6.7 +/- 2.0; P < 0.05) but not in those receiving either ketamine (baseline, 3.6 +/- 1.3; hemorrhage, 3.3 +/- 1.3) or propofol/fentanyl (baseline, 6.2 +/- 2.0; hemorrhage, 5.8 +/- 0.8). Neutrophils collected from thiopental-treated rats had elevated CD11b expression with thiopental (mean fluorescence baseline, 67.5 +/- 1.3; hemorrhage, 83.6 +/- 5.3; P < 0.05) but not with propofol/fentanyl (mean fluorescence baseline, 69.1 +/- 1.3; hemorrhage, 65.9 +/- 1.6), and ketamine-treated rats (mean fluorescence baseline, 74.3 +/- 2.1; hemorrhage, 74.8 +/- 1.1). Ketamine also inhibited upregulation of CD11b with platelet activating factor ex vivo.


CONCLUSIONS
After hemorrhage, leukocyte adhesion and CD11b expression increased during thiopental anesthesia, but propofol/fentanyl and ketamine protected against hemorrhage-induced leukocyte adhesion. The anti-inflammatory effect of ketamine was mediated by direct inhibition of CD11b expression on leukocytes.
Brookes
Zoë L S
ZL
University of Sheffield, Academic Anesthesia Unit & Microcirculation Research Group, K Floor, Royal Hallamshire Hospital, Sheffield S10 2JF, United Kingdom. zoe.brookes@shef.ac.uk
Reilly
Charles S
CS
Lawton
Bethan K
BK
Brown
Nicola J
NJ