Long-term Carotid Access in the Goat: Observations on Application of a Totally Implantable Catheter System

The investigation of metabolism of individual organs and tissues in vivo requires simultaneous measurements of arterio-venous concentration differences. Long-term metabolic studies require frequent and convenient access to veins and arteries of the relevant organs or tissues, and if blood samples are obtained by repeated veni — or arteriopuncture, difficulties may arise due to vessel thrombosis and an increasing apprehension of the goat during time. Arterial punctures are considered more painful than venipuncture, according to human patients. In the conscious goat, arteriopuncture may induce bleating, dilatation of the pupil, increased heart rate, blood glucose and free fatty acid levels, which may bias the results of a metabolic study (Linzell 1963). Furthermore, it is important to avoid situations which contribute negatively to the welfare of the goat. Establishment of permanent exteriorized carotid loops does not eliminate these problems and has a disadvantage of being vulnerable to injury. Jha et al. (1961) reported that 3 out of 10 goats died from haemorrhages, due to loop injury. The carotid artery may surgically be relocated to a subcutaneous position, which makes it less vulnerable, but also less accessible for percutaneous puncture (Tavenor 1969). Our experience with such subcutaneous relocated artery loops is that scar tissue formation is so strong after being catheterized 3-4 times, that further catheterization requires specialized assistance. The artery is eventually closed by fibrous tissue. An alternative to the repeated percutaneous puncture of subcutaneously relocated artery loops is the establishment of chronic indwelling arterial catheters, where the tip of the catheter is exteriorized to the skin. This method is well described (Huntington et al. 1989), but requires a dressing of the exteriorisation site, and restrain of the goat, in order to protect the tip from being pulled out. Therefore, we describe a modification of a totally implantable catheter system, developed for human intra-arterial long-term delivery of drugs, for permanent catheterization of the common carotid artery of goats. The entire access system of this catheter is under the skin.