Systemic inflammation leads to resistance to atracurium without increasing membrane expression of acetylcholine receptors.
BACKGROUND
Systemic inflammation may be associated with resistance to nondepolarizing neuromuscular blocking drugs, the mechanisms of which are, however, uncharacterized. The authors therefore investigated the pharmacodynamics of atracurium and its relation to the expression of nicotinic acetylcholine receptors and alpha1 -acid glycoprotein in a rat model of systemic inflammation.


METHODS
To induce a systemic inflammation, male CD rats received 56 mg/kg corynebacterium parvum intravenously. On days 2, 4, 6, 8, 10, 12, 14, or 16 after infection, neuromuscular transmission was measured. The individual effective dose of atracurium was determined, followed by an atracurium infusion at a rate to establish a steady state neuromuscular block of 50%. Total and unbound plasma concentrations of atracurium for 50% paralysis were measured using high-performance liquid chromatography. Acetylcholine receptors were quantitated using 125I-alpha-bungarotoxin. alpha1 -Acid glycoprotein concentrations in the serum were measured using a competitive chemiluminescence immunoassay.


RESULTS
The effective dose of atracurium was increased on days 4, 6, and 8. Total atracurium plasma concentrations at 50% neuromuscular paralysis were increased on days 4, 6, 8, and 10, with a peak at day 8 (8.0 +/- 1.3 micro g/ml) compared with control rats (4.23 +/- 0.82 micro g/ml). The alpha1 -acid glycoprotein concentrations were increased between days 2 and 10, with a peak on day 4 (6.52 +/- 1.45 mg/ml), and recovered to control values (0.61 +/- 0.33 mg/ml) on day 12. Unbound plasma concentrations of atracurium to achieve 50% depression, as well as the expression of acetylcholine receptors, did not differ between groups.


CONCLUSIONS
Resistance to atracurium during corynebacterium parvum-induced systemic inflammation is due to increased drug binding to alpha1 -acid glycoprotein and is unrelated to changes in acetylcholine receptor expression.
Fink
Heidrun
H
Research Fellow, Klinik für Anaesthesiologie der Technischen Universität München, Klinikum rechts der Isar, Germany.
Luppa
Peter
P
Mayer
Barbara
B
Rosenbrock
Hilkea
H
Metzger
Jochen
J
Martyn
J A Jeevendra
JA
Blobner
Manfred
M
D000758:Anesthesia; D000818:Animals; D001279:Atracurium / Q000097:blood / Q000494:pharmacology*; D004351:Drug Resistance; D007249:Inflammation / Q000473:pathology*; D007668:Kidney / Q000187:drug effects / Q000378:metabolism; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008566:Membranes / Q000187:drug effects / Q000378:metabolism; D008954:Models, Biological; D009213:Myography; D003473:Neuromuscular Nondepolarizing Agents / Q000097:blood / Q000494:pharmacology*; D009569:Nitric Oxide / Q000097:blood; D009961:Orosomucoid / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D011950:Receptors, Cholinergic / Q000096:biosynthesis*
D003473:Neuromuscular Nondepolarizing Agents; D009961:Orosomucoid; D011950:Receptors, Cholinergic; D001279:Atracurium; D009569:Nitric Oxide