AN INVESTIGATION INTO THE EFFECTS OF MIDAZOLAM AND PROPOFOL ON HUMAN RESPIRATORY CILIA BEAT FREQUENCY IN-VITRO

Objective: Patients in intensive care are known to be prone to both up per and lower respiratory tract infection. Respiratory mucus forms a b arrier to infection. Mucus transport rate (MTR) depends upon both the physical properties of mucus and the action of respiratory cilia. Pati ents undergoing anaesthesia are known to have a reduced M-TR that may be related to a depressant effect on cilia beat frequency (CBF) by ana esthetic drugs, The aim of this study was to investigate the effects o f two commonly used intensive care sedative agents, midazolam and prop ofol, on CBF using human nasal turbinate explants in vitro. Design: We exposed ciliated tissue from human nasal turbinate explants to midazo lam and propofol in supra-clinical concentrations (20 mu M midazolam a nd 70 mu M propofol) in a controlled and blinded manner for 90 min and measured CBF by the transmitted light technique. Results: After 90 mi n, mean (SEM) CBF in the group exposed to midazolam and its control gr oup were 13.0 (0.2) Hz and 12.9 (0.3) Hz, respectively. Mean (SEM) CBF in the group exposed to propofol was 13.6 (0.4) Hz and in the control group the value was 12.0 (0.6) Hz. There was no significant change in CBF (midazolam: p = 0.21, propofol: p = 0.31, MANOVA for repeated mea sures). Conclusions: We have found no effect of midazolam or propofol in supra-clinical concentrations upon CBF in human turbinate explants after a 90-min exposure. This contrasts with previous work that has sh own a depressant effect of inhalational anaesthetic agents on CBF.