Recently, Gleason et al .1have demonstrated that propofol at concentrations of 2 × 10−5to 2 × 10−4M relaxes guinea pig tracheal rings in organ baths in response to noradrenergic noncholinergic-mediated electrical field stimulation; these researchers have adopted the concentrations of propofol within this clinical range. The plasma concentration of propofol during the induction of anesthesia in humans has been reported as up to 3 × 10−5M, and burst suppression doses of propofol for cerebral protection are up to 6 × 10−5M.2–4Effective concentrations of propofol (2 × 10−5to 2 × 10−4M) in the study by Gleason et al . are probably much higher than those with clinical relevance if considering plasma-free concentrations calculated from both above clinical plasma concentrations of propofol and the substantial binding of this compound to plasma proteins (97–98%).1,3Therefore, it seems still unknown whether propofol actually protects against irritant-induced bronchoconstriction in those with the clinical condition. It would be helpful for clinicians to interpret their results if any future study is capable of showing the higher tissue uptake of propofol by the lung in their experimental condition.

Hiroyuki Kinoshita, M.D., Ph.D.,*Naoyuki Matsuda, M.D., Ph.D.

*Wakayama Medical University, Wakayama, Japan.;

Gleason NR, Gallos G, Zhang Y, Emala CW: Propofol preferentially relaxes neurokinin receptor-2-induced airway smooth muscle contraction in guinea pig trachea. Anesthesiology 2010; 112:1335–44
Kirkpatrick T, Cockshott ID, Douglas EJ, Nimmo WS: Pharmacokinetics of propofol (Diprivan) in elderly patients. Br J Anaesth 1988; 60:146–50
Servin F, Desmonts JM, Haberer JP, Cockshott ID, Plummer GF, Farinotti R: Pharmacokinetics and protein binding of propofol in patients with cirrhosis. Anesthesiology 1988; 69:887–91
Newman MF, Murkin JM, Roach G, Croughwell ND, White WD, Clements FM, Reves JG; CNS Subgroup of McSPI: Cerebral physiologic effects of burst suppression doses of propofol during nonpulsatile cardiopulmonary bypass. Anesth Analg 1995; 81:452–7
CNS Subgroup of McSPI