cc1037 CCJ Meeting abstract <p>In vitro variability in propofol absorption by different membrane oxygenators</p> Hickey S Quasim I Gaylor JD

Department of Anaesthesia, Glasgow Royal Infirmary, Glasgow

Department of Bioengineering, University of Strathclyde, Glasgow, UK

 Critical Care <p>18th Spring Meeting of the Association of Cardiothoracic Anaesthetists</p> Supported by an unrestricted educational grant from Bayer plc Meeting abstracts <p>18th Spring Meeting of the Association of Cardiothoracic Anaesthetists</p> Cambridge, UK 22 June 2001 1364-8535 2001 5 Suppl C 8 10.1186/cc1037 3 7 2001 2001 BioMed Central Ltd cc-5-4-236-08

Introduction

The sequestration of drugs, such as fentanyl [1,2], thiopental, nitroglycerine and propofol [3] in the extracorporeal circuit in vitro has been well described. This phenomenon can change the pharmacokinetic behaviour of drugs during cardiopulmonary bypass, thus potentially leading to problems in achieving adequate dosing regimens.

Objective

The aim of this in vitro laboratory study was to compare the binding of propofol to different oxygenator membranes, and to examine the effects of the type of prime solution and temperature on the rate of binding.

Methods

Samples of three types of membrane oxygenators were used: the SM-35 (polydimethylsiloxane in sheet form), the CML (polypropylene in sheet form) and the SAFE II (polypropylene in hollow fibre form). 14C-propofol in either crystalloid solution or diluted bovine blood was incubated with samples of membranes at 28°C or 37°C. Membrane samples were removed at 30, 60, 90 and 120 min and rinsed. The mass of propofol bound to the various membranes was then measured using liquid scintillation counting. This experiment was carried out for both types of prime solution at 28°C and 37°C.

Results

See Table 1. The SM-35 membrane bound significantly more propofol than the membranes from the CML and the SAFE II. Binding of propofol in diluted blood was significantly less than in crystalloid solution. Temperature had little effect on propofol binding in either prime solution type.

<p>Table 1</p>

Crystalloid solution mass (mg/membrane*)

Diluted blood mass (mg/membrane*)

Membrane (surface area)

Time (min)

28°C

37°C

28°C

37°C

SM-35 (3.5 m2)

120

113.4 ± 2.80

121.1 ± 5.60

21.35 ± 1.82

29.40 ± 3.04

CML (3.0 m2)

120

6.30 ± 1.80

25.5 ± 1.20

1.20 ± 0.09

0.90 ± 0.03

SAFE II (2.0 m2)

120

23.60 ± 1.00

22.80 ± 1.00

2.60 ± 0.12

2.80 ± 0.06

*Mean ± SD mass of propofol which could be bound by membrane of intact oxygenator, n = 5 (based on mass of propofol bound per cm2 of membrane)

 <p>Sequestration of fentanyl by the cardiopulmonary bypass (CPBP).</p> Koren G Crean P Klein J Goresky G Villamater J MacLeod SM Eur J Clin Pharmacol 1984 27 51 10.1007/BF00553154 6489427 <p>Extracorporeal circuit sequestration of fentanyl and alfentanil.</p> Skacel M Knott C Reynolds F Aps C Br J Anaesth 1986 58 947 949 3092850 <p>Sequestration of propofol in an extracorporeal circuit.</p> Tarr TJ Kent AP J Cardiothorac Anesth 1989 3(suppl 1) 75 10.1016/0888-6296(89)90818-1