Ketamine and propofol do not affect intestinal microcirculation in the rat endotoxemia: experiments in a new model for intravital microscopy

Background

Intravital microscopy (IVM) imposes the particular problem of the combined control of the body temperature of the animal and control of the local temperature of the observed organ or tissues. We constructed and tested a new tissue support platform that employed a 'hanging drop' mechanism. Since analgesic agents are often used in sepsis and could potentially influence microcirculation, the effects of ketamine (10 mg/kg intravenously [i.v.]) and propofol (10 mg/kg bolus + 10 mg/kg/hour, i.v.) on intestinal microcirculation using fluorescent intravital microscopy in an endotoxemic rat model (lipopolysaccharide Escherichia coli [LPS] injection) were examined.

Protocol

The animals (n = 49) were separated into six groups: control group (just microscopy), animals received LPS, only ketamine, ketamine + LPS, only propofol, and propofol + LPS. Two hours after LPS (15 mg/kg i.v.) and/or drug injection the terminal ileum was examined.

Results

LPS injection did not affect the functional capillary density in the longitudinal and circular muscular and the mucosal layers but increased the number of firmly adhering leukocytes (stickers) in V3 venules (LPS vs controls; 491.2 ± 100.5 vs 187.3 ± 123.0 n/mm²; mean ± standard deviation, P < 0.05) and in V1 venules (LPS vs controls: 256.7 ± 49.7 vs 97.9 ± 27.5 n/mm²; P < 0.05). The number of rolling leucocytes in V3 venules was also reduced in LPS rats as compared with the control group (3.73 ± 2.7 vs 33.3 ± 28.2 n/min; P < 0.05). The levels of IL-1β, IL-6, IL-10 and tumour necrosis factor alpha were significantly higher in the LPS animals. The LPS induced changes were not affected by ketamine or propofol administration.

Conclusion

The 'hanging drop' technique prevented tissue quenching, assured undisturbed microcirculation, provided stable temperature and humidity, and assured a clear visual field. It was found that LPS produced important microcirculatory changes. However, neither ketamine nor propofol affected microcirculation in endotoxemia in the rat and had no effect on the leukocyte adherence, and therefore could be used for microcirculatory studies.

Figure 1

Schematic representation of the cross-section of the tissue platform disclosing the optical way.

Figure 2

Deep vessels (V3 venule) with sticking leucocytes (rhodamine stained) taken in the animal pretreated with endotoxine.