A simplified technique for chronic cerebrospinal fluid collection in the awake dog

CEREBROSPINAL FLUID SAMPLING IN A BOTTLENOSE DOLPHIN (TURSIOPS TRUNCATUS) UNDER GENERAL ANESTHESIA

Brucella ceti, associated with neurobrucellosis, has been isolated from cerebrospinal fluid (CSF) of postmortem cetaceans. A 106-kg, stranded female bottlenose dolphin (Tursiops truncatus) presented with serum antibodies to Brucella spp. via competitive enzyme-linked immunosorbent assay and fluorescence polarization assay. Polymerase chain reaction (PCR) and culture of whole blood, bronchoalveolar fluid, and rectal, nasal, and genital swabs for Brucella spp. were consistently negative. Serial computed tomography revealed mild focal dilatation of brain ventricles. CSF sampling was warranted to exclude neurobrucellosis. Sedation was achieved with 30 mg diazepam (0.28 mg/kg) orally 2.5 hours prior to arrival in hospital, followed by 5.3 mg midazolam (0.05 mg/kg) intramuscularly, and anesthetic induction with 2.5 mg midazolam (0.02 mg/kg) and 200 mg propofol (2 mg/kg) administered slowly intravenously, followed by intubation and maintenance on sevoflurane using controlled mechanical and apneustic anesthesia ventilation. The atlanto-occipital joint was opened by flexing the upper cervical region with the animal in left lateral recumbency. A 20-ga × 6-inch spinal needle was advanced into the cisterna magna using radiographic guidance. CSF was collected successfully with no neurological deficits appreciable on recovery. Brucella spp. was not identified via PCR or culture. This represents the first report of an antemortem CSF tap in a cetacean.

Method for long-term cerebrospinal fluid collection in the conscious dog

In medical research there is often a need for cerebrospinal fluid (CSF) collection from conscious animals. A number of models have been published, but long-term use is often limited by factors such as damage to implant or loss of patency. When part of an implant is exteriorized, group housing is often not possible; even when singly housed, the instrumented animals might have to be fitted with protective devices such as collars, vests, or helmets. Over the last 10 years we have, through the use of this technique, managed to perform repeated CSF collections in 12 beagles. Time of implant duration has ranged from 2.3 to 6.8 years. The method uses two permanent stainless steel guide cannulas screwed into the parietal bone, positioned above but not penetrating the lateral ventricles of the brain. At the time of collection, one of the subcutaneous stainless steel cannulas is used to serve as a guide for a 20-gauge collection needle. The collection is performed under local analgesia and with minimal discomfort to the dog. With its long-term use, we feel that this model is very useful and of high ethical and welfare standards due to the virtual lack of postoperative complications, maintenance requirements, and housing restrictions.

Pharmacokinetics of epidural butorphanol in isoflurane-anaesthetized dogs

Sixteen healthy male dogs were used at random in this protocol. The dogs were anaesthetized with isoflurane in oxygen. Eight of the dogs received 0.25 mg/kg of butorphanol (group B) and the others an equal volume of isotonic saline (group S) administered by a catheter inserted in the lumbosacral epidural space. Butorphanol concentrations in plasma and cerebrospinal fluid (CSF) were measured using high-performance liquid chromatography with electrochemical detection. Maximum concentration of butorphanol and time to obtain this concentration were 42.28 ng/mL at 13.88 min in blood, and 18.03 ng/mL at 30 min in CSF. Volume of distribution, clearance, mean distribution and elimination half-lives were respectively 4.39 L/kg, 2.02 L/h.kg, 16.5 min and 189.1 min. Mean isoflurane minimal alveolar concentration values for group B obtained following hind- or forelimb stimulation decreased by 31% after epidural butorphanol. Cutaneous analgesia (to pin-prick test) persisted for 3 h after the end of isoflurane anaesthesia in group B and was in correlation with the plasmatic analgesic dose of butorphanol (9 ng/mL). These results suggested that analgesia was predominantly obtained by action of butorphanol on the supraspinal structures following its vascular systemic absorption.

Cerebrospinal fluid retrieval in the conscious dog: a methods development study

A chronic cerebrospinal fluid access system is described for use in the conscious sling-restrained dog. In a pilot study of ten dogs, a fenestrated barium-impregnated silastic catheter was surgically implanted in the subarachnoid space of the second cervical vertebra through a dorsal laminectomy. This fenestrated catheter was coupled to a subcutaneous access port. Following surgery, cerebrospinal fluid was sampled weekly and evaluated for protein content and cytology. The cerebrospinal fluid albumin to serum albumin ratio was calculated for each sample to evaluate blood-brain barrier integrity. The instrumentation was successfully implanted in five of the first eight dogs using a midbody dorsal laminectomy. Cerebrospinal fluid access was maintained in these dogs for 21 +/- 10 days. Using a slight modification of the original technique, the final two dogs were instrumented through a caudodorsal laminectomy of the second cervical vertebra. The cerebrospinal fluid access system remains patent after 444 days of study in these two dogs. Necropsy evaluation suggested that catheter failure in the immediate postoperative period was due to gross malposition of the catheter. Chronic catheter failure occurred secondary to obstruction by local fibrous tissue reaction. Using this instrumentation, a pharmacokinetic evaluation of the plasma and cerebrospinal fluid deposition of an intravenous bolus of acyclovir was successfully performed twice in a single dog without complications. This instrumentation could provide chronic cerebrospinal fluid access for multiple pharmacokinetic studies in the conscious dog.