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Effects of intravenous anesthetics on bacterial elimination in human blood in vitro
A Heller1, S Heller, S Blecken
1Department of Anesthesiology and Operative Intensive Care Medicine, Faculty of Clinical Medicine Mannheim, University of Heidelberg, Germany.
Background:
Since anesthetics are widely used in critically ill patients, this study investigates anesthetic effects on neutrophil and monocyte function concerning bacterial elimination in human whole blood.
Methods:
The effects of thiopental (20 and 200 microg/ml), propofol (5 and 50 microg/ml), midazolam (0.15 and 1.5 microg/ml) and ketamine (3 and 30 microg/ml) on elimination of Escherichia (E.) coli from whole blood were investigated in vitro after incubation for 1 h in both clinical (1) (n=10) and 10-fold higher (h) (n=11) concentrations. These data were compared to neutrophil and monocyte phagocytosis (1; n=6) and burst activity (1; n=10, h; n=11), measured by flow cytometry. To enable quantification of the clearance process, a defined number of 10(5) colony forming units of E. coli were added to the blood assays and bacterial growth was determined.
Results:
All anesthetics delayed bacterial clearance from the blood in the 10-fold concentration (P<0.05). Thiopental (1+h) and propofol (h) suppressed neutrophil (59+/-3% and 38+/-6%) and monocytic (45+/-6% and 30+/-11%) oxidative burst (P<0.01). Phagocytosis was reduced even after propofol (1) in polymorphonuclear leukocytes (PMN) (34+/-9%; P<0.05) and monocytes (35+/-11%). Ketamine (h) prolonged bacterial elimination (P<0.01), which did correlate with inhibition of monocytic phagocytosis, by 26+/-14%. Midazolam application (h) resulted in an inhibition of PMN-respiratory burst by 19+/-6% (P<0.05) and impaired bacterial clearance (P<0.05).
Conclusion:
Thiopental, propofol, midazolam and ketamine affect E. coli clearance and neutrophil and monocyte oxidative burst and phagocytosis in vitro only in high concentrations, while thiopental inhibited monocytic burst and propofol impaired PMN phagocytosis even in clinically used concentrations. These data suggest that i.v. anesthetics in concentrations recommended for general anesthesia seem to have minor influence on the investigated host defense mechanisms.
Insights
Intravenous anesthetics like thiopental, propofol, midazolam, and ketamine can impair bacterial clearance and immune cell function in high concentrations. However, clinical doses of these anesthetics appear to have minimal impact on host defense mechanisms.
Area of Science:
- Immunology
- Pharmacology
- Critical Care Medicine
Background:
- Anesthetics are frequently administered to critically ill patients.
- Investigating anesthetic effects on immune cell function is crucial for patient outcomes.
- Neutrophil and monocyte functions are key in eliminating bacterial infections.
Purpose of the Study:
- To evaluate the in vitro effects of thiopental, propofol, midazolam, and ketamine on bacterial clearance.
- To assess the impact of these anesthetics on neutrophil and monocyte phagocytosis and oxidative burst.
- To compare anesthetic effects at clinical and 10-fold higher concentrations.
Main Methods:
- Human whole blood assays were used to determine the clearance of Escherichia coli.
- Anesthetics were incubated with blood at clinical and high concentrations.
- Neutrophil and monocyte phagocytosis and oxidative burst were measured using flow cytometry.
Main Results:
- All tested anesthetics delayed bacterial clearance at high concentrations.
- Thiopental and propofol significantly suppressed neutrophil and monocyte oxidative burst.
- Propofol reduced phagocytosis in both polymorphonuclear leukocytes and monocytes even at clinical concentrations.
Conclusions:
- Anesthetics affect bacterial clearance and immune cell function primarily at high concentrations.
- Thiopental and propofol demonstrated inhibitory effects on immune functions at clinically relevant doses.
- Intravenous anesthetics at general anesthesia concentrations show minimal influence on the studied host defense mechanisms.