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Comparison of the effects of four i.v. anaesthetic agents on polymorphonuclear leucocyte function
J A Davidson1, S J Boom, F J Pearsall
1University Department of Anaesthesia, Royal Infirmary, Glasgow.
Abstract:
Initial resistance of bacterial infection is mediated primarily by polymorphonuclear leucocytes (PMN). Anaesthetic agents have been reported to impair various aspects of PMN function. It is possible that the use of these agents to sedate critically ill patients may further compromise an already depressed host defence mechanism. A flow cytometric technique with fresh whole blood from 10 healthy volunteers was used. Phagocytic and respiratory burst activity of PMN incubated for 1 h with either propofol, thiopentone, midazolam or ketamine at both clinical plasma concentrations and 100 times this concentration were determined. Thiopentone at the higher concentration reduced both respiratory burst activity (mean peak channel 50.7 compared with control value of 77.6 (P < 0.0001)) and phagocytosis (mean peak channel 47.5 compared with 79.9 (P < 0.0001)). Ketamine at 100 times the clinical plasma concentration also reduced respiratory burst and phagocytosis, but this failed to reach statistical significance (P = 0.10 and P = 0.053, respectively). No significant depression occurred in the other groups. The results suggest that these i.v. anaesthetic agents, at clinically relevant concentrations, have minimal effects on PMN phagocytosis and oxygen free radical production. At higher concentrations thiopentone and ketamine may affect phagocytic function and thiopentone may impair intracellular cytolysis.
Insights
Intravenous anesthetic agents generally have minimal impact on polymorphonuclear leucocytes (PMN) function at clinical doses. However, high concentrations of thiopentone and ketamine may impair PMN phagocytic activity and intracellular cytolysis, potentially affecting host defense.
Area of Science:
- Immunology
- Anesthesiology
- Critical Care Medicine
Background:
- Bacterial infection resistance relies on polymorphonuclear leucocytes (PMN).
- Anesthetic agents may compromise PMN function.
- Sedating critically ill patients with anesthetics could further weaken host defenses.
Purpose of the Study:
- To investigate the effects of common intravenous anesthetic agents on PMN function.
- To determine if clinical concentrations of propofol, thiopentone, midazolam, and ketamine impact PMN phagocytosis and respiratory burst activity.
Main Methods:
- A flow cytometry technique was employed using fresh whole blood from 10 healthy volunteers.
- PMN were incubated with anesthetic agents (propofol, thiopentone, midazolam, ketamine) at clinical and 100x clinical concentrations.
- Phagocytic and respiratory burst activities of PMN were quantified.
Main Results:
- Thiopentone at high concentrations significantly reduced PMN respiratory burst and phagocytosis (P < 0.0001).
- Ketamine at 100x clinical concentration showed a trend towards reduced respiratory burst and phagocytosis, but not statistically significant (P = 0.10 and P = 0.053).
- Propofol and midazolam showed no significant effects on PMN function at tested concentrations.
Conclusions:
- Intravenous anesthetics at clinically relevant concentrations exhibit minimal effects on PMN phagocytosis and oxygen free radical production.
- High concentrations of thiopentone and ketamine may negatively impact PMN phagocytic function and intracellular cytolysis.
- Further research is needed to fully understand the clinical implications for critically ill patients.