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Effect of enflurane, isoflurane, and nitrous oxide on the microbicidal activity of human polymorphonuclear leukocytes
Abstract:
The effect of enflurane and isoflurane with and without nitrous oxide (N2O) on human polymorphonuclear leukocyte (PMNL) microbicidal function was studied. Bacterial killing was determined using a standard pour-plate technique and by oxidative activity as measured by chemiluminescence (CL). No killing of Escherichia coli, Klebsiella pneumoniae, or Staphylococcus aureus was seen at bacteria:PMNL ratios of 1 or 10:1 with either enflurane or isoflurane at concentrations greater than normally used (3%). However, at a clinically relevant concentration of 2%, a significant inhibition of bacterial killing was observed with enflurane but not isoflurane at a bacteria:PMNL ratio of 100:1. The CL response also was decreased significantly (28% inhibition) by 2% enflurane. N2O 70% plus O2 30% had no effect on bactericidal activity or chemiluminescence alone or in combination with enflurane or isoflurane. The inhibition of bacterial killing and CL following enflurane exposure could be reversed by exposing the enflurane treated PMNL to air for 30 min. These results suggest that enflurane is able to inhibit PMNL microbicidal activity only when the PMNL are stressed with a large bacterial challenge or stimulus. This inhibition is temporal and only occurs during enflurane exposure.
Insights
Enflurane, but not isoflurane, temporarily inhibits human polymorphonuclear leukocyte (PMNL) microbicidal function at clinically relevant concentrations when challenged with high bacterial loads. This effect is reversible upon air exposure.
Area of Science:
- Anesthesiology
- Immunology
- Microbiology
Background:
- Inhaled anesthetics can modulate immune cell function.
- Polymorphonuclear leukocytes (PMNLs) are critical for innate immunity and bacterial killing.
- Understanding anesthetic effects on PMNLs is crucial for patient outcomes.
Purpose of the Study:
- To investigate the impact of enflurane and isoflurane on human PMNL microbicidal activity.
- To assess the influence of nitrous oxide (N2O) on these effects.
- To determine the concentration-dependent and reversible nature of anesthetic-induced PMNL dysfunction.
Main Methods:
- Human PMNLs were exposed to varying concentrations of enflurane and isoflurane.
- Bacterial killing assays (pour-plate technique) were performed against E. coli, K. pneumoniae, and S. aureus.
- Oxidative activity was measured using chemiluminescence (CL).
- Effects of N2O and air exposure were evaluated.
Main Results:
- Enflurane (2%) significantly inhibited bacterial killing and CL at a high bacteria:PMNL ratio (100:1), while isoflurane did not.
- Higher anesthetic concentrations (>3%) showed no effect at lower ratios (1:1, 10:1).
- Nitrous oxide had no independent or combined effect on PMNL function.
- Enflurane-induced inhibition was reversible upon exposure to air.
Conclusions:
- Enflurane can temporarily impair PMNL microbicidal function under significant bacterial challenge.
- Isoflurane does not exhibit this inhibitory effect at clinically relevant concentrations.
- The observed inhibition is transient and dependent on anesthetic exposure and bacterial load.