A new airway device for small laboratory animals.

There is a need for a device for improved management of the airway of small laboratory animals during general anaesthesia. This report introduces such a device, referred to here as the airway device (AD). The AD has some similarity to the laryngeal mask airway (LMA) developed for human patients, but the mask portion of the device is specifically designed for small laboratory animals. In addition, the device has an oesophageal extension and unlike the LMA does not have a cuff associated with the mask. This report also shares experience of tests of one prototype AD with six New Zealand white rabbits. The AD was used for administering isoflurane and its effectiveness was evaluated during conditions of spontaneous and controlled intermittent positive pressure ventilation. The results provide encouragement for further development of the AD for airway management of small laboratory animals.

Interrelations of organism prevalence, specimen collection method, and host age, sex, and breed among 8,354 canine urinary tract infections (1969-1995).

Selected information was compiled from canine urinalyses and urine cultures conducted between January 1969 and December 1995. Eight thousand three hundred fifty-four microbial isolates (bacteria and fungi) included 4,873 isolates from females and 3,481 from males. Ten bacterial genera accounted for 96.3% of the urinary isolates, including Escherichia coli (44.1%), Staphylococcus spp. (11.6%), Proteus spp. (9.3%), Klebsiella spp. (9.1%), Enterococcus spp. (8.0%), and Streptococcus spp. (5.4%) as the 6 most common isolates in both genders of dogs. Among these 6 genera, female dogs were generally predisposed over males, although males had more urinary tract infections (UTIs) caused by Klebsiella spp. Distributions of ages at UTI diagnosis tended to be similar between genders. Infection with a single microbial species was responsible for >72% of UTIs in both genders. Among females, 40 breeds and a mixed-breed group represented 90.2% of all positive urine cultures, 88.4% of the individual dogs with UTIs. and 88.2% of the microbial isolations. Among males, these same 41 breed groups represented 87.9% of all positive urine cultures, 87.6% of the individual dogs, and 88.2% of the microbial isolations.

A practical dog bed for environmental enrichment for geriatric beagles, with applications for puppies and other small dogs.

A group of 30 older beagle dogs was acquired for aging studies. The dogs were initially housed in kennel runs equipped with elevated benches, but it became apparent that some of the oldest animals had difficulties jumping down from them. To improve animal safety and comfort, practical dog beds were made out of the ends of clean high-density polyethylene barrels. Synthetic fleece bed liners were used for dogs that did not chew them or remove them from the beds. Nine of the beagles regularly were observed to use the beds. We also have found that this easily fashioned dog bed is a useful kennel resting place option for puppies and other small dogs.

Design and use of a protective jacket to prevent self-inflicted injury following cervical laminoplasty in the goat (Capra hircus).

A group of dairy goats underwent cervical laminoplasty procedures as part of a biomechanics project. Although most animals had minimal incisional complications, several developed excoriations exacerbated by scratching at the incision site 6 to 8 weeks after the surgery. Local and systemic treatment was instituted as indicated. Bandages were inadequate to protect the neck from self-trauma, and the potential existed for serious injury to or infection of the old surgical site. We designed and made custom padded jackets for these animals. Treatment continued. While allowing the animals to exercise their scratching behavior, the jackets protected the traumatized area until healing was complete and the pruritus resolved. This jacket or modifications of it may be useful in other goat, sheep, or calf projects in which protection of the neck, shoulders, and thorax is needed.

Newborn tissue concentrations of bupivacaine following maternal epidural administration during labor in guinea pigs.

Newborn plasma concentrations of maternally administered bupivacaine are often measured, but it is unclear how well they reflect tissue concentrations. Bupivacaine (0.25%) was administered epidurally (0. 12 ml/kg) 10 min prior to labor induction in 6 term-pregnant guinea pigs. Plasma, brain, heart and liver samples were obtained for bupivacaine analysis from newborns (n = 22) after spontaneous delivery. Liver bupivacaine concentrations were 2-3 times greater than those in the plasma, brain, and heart. A similar pattern of tissue concentrations was seen in a smaller number of newborns delivered by cesarean section. Liver bupivacaine concentration decreased with drug-delivery interval in littermates, while heart and brain concentrations showed no relationship with drug-delivery interval. Blood gases of newborns reflected acidosis, which may have influenced tissue drug concentrations. Under conditions of the study, bupivacaine concentrations in heart and brain, potential sites of bupivacaine action, were lower than those observed in a peripheral blood sample.

Evaluation for malignant hyperthermia susceptibility in black-tailed deer.

To investigate a possible link of malignant hyperthermia to capture myopathy, between June 1990 and July 1993 we anesthetized four black-tailed deer (Odocoileus hemionus columbianus) and challenged them with halothane and succinylcholine. Halothane had no significant effect on oxygen consumption. Succinylcholine significantly (P < 0.05) increased cardiac output (mean +/- SD), from 2.94 +/- 1.05 l/min to 5.26 +/- 1.79 l/min, and oxygen consumption, from 5.5 +/- 2.1 ml/kg/min to 10.1 +/- 2.9 ml/kg/min. Muscle biopsy specimens tested for malignant hyperthermia susceptibility responded normally to halothane and caffeine. We conclude that these deer did not experience malignant hyperthermia; suggesting no link to capture myopathy.

Epidural catheter placement for testing of obstetrical analgesics in female guinea pigs.

The pregnant guinea pig may be a useful model for the study of drug effects in the newborn. A reliable technique for epidural catheterization in the guinea pig was developed to allow use of this model to evaluate the effects of epidural labor analgesics on neonates. Catheters were implanted in two open pilot animals and 19 time-dated pregnant animals on days 59 to 62 of gestation. After establishing a surgical plane of isoflurane-induced anesthesia, an incision was made over the dorsal lumbar part of the spine. The L3-4 intervertebral space was exposed to allow introduction of a caudally directed 27-gauge catheter into the epidural space. The catheter was capped and implanted subcutaneously, then the animal was allowed to recover from anesthesia. Catheter placement was evaluated, using a bupivacaine test dose in 17 animals and postmortem histologic examination in 20 animals. One animal died immediately after surgery. Epidural placement was confirmed histologically in 15 of 20 animals. Failed catheters were either subdural, with one catheter found to be penetrating the spinal cord (intraspinal), or intramuscular. Response to epidurally administered bupivacaine was variable but was typically characterized by normal alertness and ability to use the forelimbs; depression of the panniculus reflex in the dorsal lumbar region; and hind limb motor impairment, with ataxia, loss of the placing reflex, and a tendency to drag the hind limbs. Subdural placement was associated with CNS depression, recumbency, shallow breathing, and sensory block ascending to the level of the ears.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthetic potency and cardiopulmonary effects of enflurane, halothane, and isoflurane in goats.

Anesthetic requirements, as defined by the minimum alveolar anesthetic concentration (MAC) that prevents gross, purposeful movement in 50% of animals, have not been determined in goats. Therefore, we determined anesthetic potency of enflurane (N = 6), halothane (N = 8), and isoflurane (N = 7) in goats by using the tail clamp and dew-claw clamp as the noxious stimuli and then measured the cardiovascular and respiratory effects of these agents. The MAC was 2.0 +/- 0.4%, 1.3 +/- 0.1%, and 1.5 +/- 0.3% (mean +/- SD) for enflurane, halothane, and isoflurane, respectively. At 1 MAC, when ventilation was changed from controlled to spontaneous, blood pressure decreased in goats anesthetized with isoflurane (98 +/- 17 to 78 +/- 13 mm Hg) and halothane (95 +/- 10 to 83 +/- 14 mm Hg) but did not significantly change in goats anesthetized with enflurane; heart rate increased in goats anesthetized with halothane (117 +/- 12 to 127 +/- 10 beats/min) but was not significantly different in goats anesthetized with enflurane or isoflurane; and cardiac output increased in goats anesthetized with enflurane (5.70 +/- 1.23 to 7.05 +/- 2.02 liters/min) and halothane (6.14 +/- 0.94 to 7.91 +/- 2.45 liters/min) but not with isoflurane. During spontaneous breathing, respiratory depression was manifested by apnea in two animals and an elevated PaCO2: 57 +/- 15 mm Hg, 55 +/- 13 mm Hg, and 59 +/- 14 mm Hg, respectively, for enflurane, halothane, and isoflurane. Minute ventilation during spontaneous breathing was approximately 50% of controlled ventilation for each anesthetic agent.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of greyhound susceptibility to malignant hyperthermia using halothane-succinylcholine anesthesia and caffeine-halothane muscle contractures.

We investigated Greyhounds because of prior reports of malignant hyperthermia (MH) episodes and because Greyhounds may express high genetic relatedness due to inbreeding for generations. Seven Greyhound and six mongrel dogs were given halothane and succinylcholine anesthesia as a challenge to trigger MH. They also underwent semitendinosus muscle biopsy for contracture study with halothane and caffeine. Measurements in vivo of mixed venous and arterial blood gases, cardiac output by thermodilution, temperature, blood pressure, and pulse rate provided sequential data regarding whole body O2 consumption (product of cardiac output and arterial-mixed venous O2 content difference), acid-base status, and arterial CO2 tension. Greyhounds and mongrels had uniformly similar in vivo and in vitro responses, without evidence for MH. Contracture thresholds were higher than those reported for normal swine and humans (8 mM vs. 4 mM). Information on MH susceptibility in this breed is important for laboratory investigation in Greyhounds as well as to veterinary medicine in general. Neither mongrels nor this group of Greyhounds were obviously susceptible to MH. If all Greyhounds are genetically homologous, then Greyhounds may not be specifically MH susceptible. These findings overall may provide a protocol and baseline normal comparative data for determining MH susceptibility in dogs and other species.

Skeletal lesions and anemia associated with ascorbic acid deficiency in juvenile rhesus macaques.

Young rhesus macaques housed in outdoor corn cribs and fed a commercially prepared primate diet became weak, depressed, were reluctant to move, and expressed locomotor abnormalities. Thirteen severely affected animals were hospitalized for evaluation. Physical examination disclosed swellings and instabilities involving the ends of long bones. Radiography confirmed physeal fractures in 11 of 13 animals. Affected bones included the distal femur, proximal humerus, distal tibia/fibula, and distal radius/ulna. Other, less obvious changes were noted on radiographs. Anemia was a consistent finding. Ascorbic acid deficiency was suspected and therapy was initiated that consisted of vitamin supplements, diet change, cage rest, and support bandages. Feed samples were submitted to a laboratory for analysis and were confirmed deficient in vitamin C. Follow-up radiographs showed large calcifying subperiosteal hematomas in epiphyseometaphyseal regions, consistent with a diagnosis of scurvy. Twelve of 13 animals recovered clinically. Subsequent radiographs documented improvement of initially severe angular deformities associated with displaced fractures.

Partial colectomy for treating acquired megacolon in long-tailed macaques.

A syndrome presenting as gross abdominal distension and diagnosed as acquired megacolon was observed in five adult female long-tailed macaques. Gastrointestinal signs included diarrhea, mucus in the stool, anorexia, and failure to pass stool, with repeated episodes of extreme abdominal distension and accumulation of gas and feces in greatly enlarged colons. Medical management was unsuccessful. A partial colectomy with a standard end-to-end colonic anastomosis was performed to remove the section of distended colon in each animal. Histologically, affected colons had degeneration and fibrosis, primarily in the longitudinal layer of the lamina muscularis. Hemograms, serum chemistries, and histopathologic features were not diagnostic of a specific etiology for megacolon. Four of five animals had undergone at least one obstetrical surgery. Two of these had the first episode of colonic distension within 3 days postoperatively. Intra-abdominal adhesions were noted during exploratory surgery in all animals. Three of five had colonic volvulus observed during colectomy. Recovery post-colectomy was uneventful and animals remained free of clinical signs of megacolon.

The anterior cricoid split explored via the canine model, preliminary studies.

Since Cotton and Seid introduced a new surgical procedure, the anterior cricoid split in 1980, the treatment of the difficult-to-extubate infant or child has changed dramatically. The mechanics of how the procedure works are poorly understood. This study was undertaken to investigate the effects of the anterior cricoid split on the cricoid cartilage. The technique was modified so as to allow placement and maintenance of an endotracheal tube but still allow normal activity in the canine subjects. Australian Shepherd puppies were divided into 3 groups. Group 1 underwent the anterior cricoid split procedure with placement of an endotracheal tube stent, Group 2 underwent the anterior cricoid split procedure without the use of a stent, and Group 3 served as controls. All animals were sacrificed at 12 weeks of age. The results show that there was an actual gap in the cricoid cartilage in all animals that underwent the anterior cricoid split procedure. Stenting with an endotracheal tube significantly increased this gap. These results suggest that in the canine model the anterior cricoid split may be used to actually increase the size of the subglottic space.

Anesthetic, preoperative and postoperative considerations for liver transplantation in swine.

Perioperative care and anesthetic management of donor and recipient animals are crucial factors in studies involving experimental liver transplantation in the pig. Prevention of unacceptably high morbidity and mortality in the transplant recipients requires meticulous attention to anesthesia, preoperative and postoperative care. Liver transplant surgeries were performed using 15 pairs of pigs. Six of the transplant recipients were anesthetized with halothane plus 50% nitrous oxide (N2O) and oxygen (O2), and nine with isoflurane plus 50% N2O in O2. Arterial blood pressure, total anesthetic time, time of interruption of vena cava blood flow, and fluids administered, as well as length of survival were among the parameters measured and compared for the two groups. No deaths were attributed to either anesthetic technique. However, the isoflurane group had slightly higher blood pressure intraoperatively, better long range survival, and relatively rapid recoveries when compared to the halothane group. Because of these findings and the reported low rate of isoflurane metabolism and low resultant potential for formation of toxic metabolites when compared to halothane metabolism, we have elected to use the isoflurane-50% N2O regimen for this procedure.

Potency of isoflurane and nitrous oxide in conventional swine.

The minimum alveolar concentration (MAC) of isoflurane in oxygen (O2) was determined to be 1.55 +/- 0.08 (SEM) volumes % in twelve pigs (Sus scrofa). Values for isoflurane MAC in the presence of 50% (I-50%N2O) and 66% (I-66%N2O) nitrous oxide were determined in nine and six of these same animals, respectively, and equalled 1.03 +/- 0.05 vol % for I-50%N2O and 0.95 +/- 0.07 vol % for I-66%N2O. Animals respired spontaneously and arterial blood pressure (AP), heart rate (HR), rectal body temperature, and arterial blood gases (PO2, PCO2, and pH) were recorded throughout the study period. These parameters were within normal limits near MAC for all three gas combinations. The MAC for isoflurane in swine was similar to that for other animals and, man and the use of this agent was associated with rapid and uneventful anesthetic induction and recovery. The addition of 50% and 66% nitrous oxide (N2O) reduced the isoflurane MAC by 30% and 42%, respectively.