Assessment of the cough reflex after propofol anaesthesia for colonoscopy.
BACKGROUND
Dysfunction of the cough reflex as a result of the lingering effects of anaesthetics may lead to aspiration pneumonia or retained secretions after general anaesthesia. It is unknown whether low concentrations of propofol alter the cough reflex in the early period after anaesthesia. The objective of this study was to investigate the effect of low concentrations of propofol on the cough reflex sensitivity as assessed by the cough reflex threshold to an inhaled irritant.


METHODS
Fifteen, ASA I-II, non-smoking patients undergoing elective colonoscopy were studied. Anaesthesia was induced and maintained with a blood target-controlled propofol infusion. Cough reflex threshold was measured with citric acid. Increasing concentrations of nebulized citric acid (2.5, 5, 10, 20, 40, 80, 160, 320, and 640 mg ml(-1)) were delivered during inspiration until a cough was evoked. The citric acid concentration eliciting one cough (C1) was defined as the cough reflex threshold. C1 was log transformed for statistical analysis (Log C1). Log C1 was measured before anaesthesia and during the recovery period with estimated decreasing propofol concentrations of 1.2, 0.9, 0.6, and 0.3 microg ml(-1).


RESULTS
Log C1 (median; interquartile range) measured with propofol concentrations of 1.2, 0.9, 0.6, 0.3, and 0 microg ml(-1) were 1.9 (0.6), 1.9 (1.0), 1.9 (1.1), 1.9 (0.6), and 1.9 (0.7) mg ml(-1) (NS), respectively. However, light sedation was observed with propofol concentrations of 1.2 and 0.9 microg ml(-1).


CONCLUSIONS
This study indicates that residual sedation after propofol anaesthesia for colonoscopy does not adversely affect the cough reflex.
Guglielminotti
J
J
Service d'Anesthésiologie et de Réanimation Chirurgicale, Hôpital Bichat, Assistance Publique, Hôpitaux de Paris, 46 rue Henri Huchard, F-75018 Paris, France. jean.guglielminotti@bch.ap-hop-paris.fr
Rackelboom
T
T
Tesniere
A
A
Panhard
X
X
Mentre
F
F
Bonay
M
M
Mantz
J
J
Desmonts
J M
JM
D000328:Adult; D000762:Anesthesia Recovery Period; D018686:Anesthetics, Intravenous / Q000097:blood / Q000494:pharmacology*; D019343:Citric Acid; D003113:Colonoscopy; D003371:Cough / Q000139:chemically induced* / Q000503:physiopathology / Q000517:prevention & control; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011015:Pneumonia, Aspiration / Q000517:prevention & control; D015742:Propofol / Q000097:blood / Q000494:pharmacology*; D012018:Reflex / Q000187:drug effects*
D018686:Anesthetics, Intravenous; D019343:Citric Acid; D015742:Propofol