CEREBROSPINAL-FLUID RETRIEVAL IN THE CONSCIOUS DOG - A METHODS DEVELOPMENT STUDY

A chronic cerebrospinal fluid access system is described for use in th e conscious sling-restrained dog. In a pilot study of ten dogs, a fene strated barium-impregnated silastic catheter was surgically implanted in the subarachnoid space of the second cervical vertebra through a do rsal laminectomy. This fenestrated catheter was coupled to a subcutane ous access port. Following surgery, cerebrospinal fluid was sampled we ekly and evaluated for protein content and cytology. The cerebrospinal fluid albumin to serum albumin ratio was calculated for each sample t o evaluate blood-brain barrier integrity. The instrumentation was succ essfully implanted in five of the first eight dogs using a midbody dor sal laminectomy. Cerebrospinal fluid access was maintained in these do gs for 21 +/- 10 days. Using a slight modification of the original tec hnique, the final two dogs were instrumented through a caudodorsal lam inectomy of the second cervical vertebra. The cerebrospinal fluid acce ss system remains parent after 444 days of study in these two dogs. Ne cropsy evaluation suggested that catheter failure in the immediate pos toperative period was due to gross malposition of the catheter. Chroni c catheter failure occurred secondary to obstruction by local fibrous tissue reaction. Using this instrumentation, a pharmacokinetic evaluat ion of the plasma and cerebrospinal fluid deposition of an intravenous bolus of acyclovir was successfully performed twice in a single dog w ithout complications. This instrumentation could provide chronic cereb rospinal fluid access for multiple pharmacokinetic studies in the cons cious dog.