Terrell G. Heaton-Jones

OBJECTIVE: Sedative, cardiorespiratory, and analgesic effects of intramuscular administration of medetomidine (40 micrograms/kg of body weight)-glycopyrrolate (0.01 mg/kg) and medetomidine (10 micrograms/kg)-butorphanol (0.2 mg/kg)-glycopyrrolate (0.01 mg/kg) combinations were compared. Additional evaluations were done on reversal of medetomidine, using atipamezole (200 micrograms/kg. IV), after 90 minutes of medetomidine-induced sedation. DESIGN: Crossover study, with each dog receiving each drug combination at 1-week intervals. ANIMALS: Six 2-year-old English hound-type dogs. PROCEDURE: Arterial blood pressure, ECG, respiratory rate, tidal volume, minute volume, arterial blood gas tensions, and serum biochemical variables were measured before, during, and after sedation. Analgesia was evaluated by needle prick on the skin and tail clamp. RESULTS: Heart rate decreased significantly from 100 beats/min to < 40 beats/min within 3 minutes of injection of medetomidine and medetomidine and butorphanol (MB). Mean arterial blood pressure in both groups were maintained above 100 mm of Hg throughout the recording period. There was no significant difference between medetomidine and MB in respiratory rate, tidal volume, and minute ventilation. Hypoxemia (PaO2 < 60 mm of Hg) was observed at 10 and 20 minutes in 2 dogs given MB. Atipamezole administration in the dogs given medetomidine significantly increased PaO2, and returned the values to baseline. Needle prick analgesia duration was longer in the medetomidine (80 +/- 7.7 minutes) than MB (56.0 +/- 19.2 minutes) group. Tail pinch analgesia was variable in both groups. Duration of lateral recumbency was longer after medetomidine (90 +/- 0 minutes) than MB (73.5 +/- 19.0 minutes). CONCLUSION: Medetomidine and MB were effective combination for mildly invasive procedures. CLINICAL RELEVANCE: MB induced a shorter period of analgesia and recumbency than did medetomidine.

Thirty American alligators (Alligator mississippiensis), including 24 wild-caught and six control captive farm-raised alligators, were analyzed for whole body mercury contamination. Wild-caught animals were collected from Water Conservation Area 3 in the Everglades ecosystem (n = 12) and from Alachua, Brevard, and Collier counties outside the Everglades (n = 12). Using cold-vapor atomic absorption spectrophotometry, samples of brain, cervical spinal cord, liver, paired kidneys, paired testes, paired ovaries, paired oviducts, heart, lungs, spleen, bile, tail and leg muscle, and tail and leg scales were analyzed on a wet weight basis to determine mercury concentration. Mercury was consistently detected in all specimens except for bile. Farm-raised alligators, fed a commercially prepared diet, contained very low mercury concentrations in all tissues analyzed. In comparison with alligators from outside the Everglades, Everglades alligators had significantly elevated concentrations of mercury in all tissues analyzed except ovaries, oviduct, bile, tail scales, and leg scales (paired two-sample Student's tau-test, P < 0.05). Muscle concentrations exceeded state (0.50-1.50 ppm) and federal (1.00 ppm) allowances for safe human consumption in alligators collected in the Everglades. No clinical signs of neurologic, hepatic, or renal toxicosis were detected. Because of the alligator's ability to bioaccumulate mercury, this species might be useful as a bio-monitor for environmental mercury contamination.

OBJECTIVE: To evaluate renal effects of carprofen in healthy dogs following general anesthesia. DESIGN: Randomized clinical trial. ANIMALS: 10 English hound dogs (6 females and 4 males). PROCEDURE: Dogs were randomly assigned to control (n = 5) or carprofen (5) groups. Anesthesia was induced with propofol (6 to 8 mg/kg [2.7 to 3.6 mg/lb] of body weight, i.v.) and maintained with isoflurane (end-tidal concentration, 2.0%). Each dog underwent two 60-minute anesthetic episodes with 1 week between episodes, and mean arterial blood pressure was maintained between 60 and 90 mm Hg during each episode. Dogs in the carprofen group received carprofen (2.2 mg/kg [1 mg/lb], p.o.) at 9:00 AM and 6:00 PM the day before and at 7:00 AM the day of the second anesthetic episode. Glomerular filtration rates (GFR) were determined during each anesthetic episode by use of renal scintigraphy. Serum creatinine and BUN concentrations and the urine gamma-glutamyltransferase-to-creatinine concentration (urine GGT:creatinine) ratio were determined daily for 2 days before and 5 days after general anesthesia. RESULTS: Significant differences were not detected in BUN and serum creatinine concentrations, urine GGT:creatinine ratio, and GFR either between or within treatment groups over time. CONCLUSIONS AND CLINICAL RELEVANCE: Carprofen did not significantly alter renal function in healthy dogs anesthetized with propofol and isoflurane. These results suggest that carprofen may be safe to use for preemptive perioperative analgesia, provided that normal cardiorespiratory function is maintained.

Sixteen captive and wild-caught American alligators (Alligator mississippiensis), seven juveniles (< or = 1 m total length [TL]; 6.75 +/- 1.02 kg), and nine adults (> or = 2 m TL; 36.65 +/- 38.85 kg), were successfully anesthetized multiple times (n = 33) with an intramuscular (i.m.) medetomidine-ketamine (MK) combination administered in either the triceps or masseter muscle. The juvenile animals required significantly larger doses of medetomidine (x = 220.1 +/- 76.9 microg/kg i.m.) and atipamezole (x = 1,188.5 -/+ 328.1 microg/kg i.m.) compared with the adults (medetomidine, x = 131.1 +/- 19.5 microg/kg i.m.; atipamezole, x = 694.0 +/- 101.0 microg/kg i.m.). Juvenile alligators also required higher (statistically insignificant) doses of ketamine (x = 10.0 +/- 4.9 mg/kg i.m.) compared with the adult animals (x = 7.5 +/- 4.2 mg/kg i.m.). The differences in anesthesia induction times (juveniles, x = 19.6 +/- 8.5 min; adults, x = 26.6 +/- 17.4 min) and recovery times (juveniles, x = 35.4 +/- 22.1 min; adults, x = 37.9 +/- 20.2 min) were also not statistically significant. Anesthesia depth was judged by the loss of the righting, biting, corneal and blink, and front or rear toe-pinch withdrawal reflexes. Recovery in the animals was measured by the return of reflexes, open-mouthed hissing, and attempts to high-walk to the opposite end of the pen. Baseline heart rates (HRs) were significantly higher in the juvenile animals (x = 37 +/- 4 beats/min) compared with the adults (x = 24 +/- 5 bpm). However, RRs (juveniles, x = 8 +/- 2 breaths/min; adults, x = 8 +/- 2 breaths/min) and body temperatures (juveniles, x = 24.1 +/- 1.1 degrees C; adults, x = 25.2 +/- 1.2 degrees C) did not differ between the age groups. In both groups, significant HR decreases were recorded within 30-60 min after MK administration. Cardiac arrhythmias (second degree atrio-ventricular block and premature ventricular contractions) were seen in two animals but were not considered life-threatening. Total anesthesia times ranged from 61-250 min after i.m. injection. Although dosages were significantly different between the age groups, MK and atipamezole provided safe, effective, completely reversible anesthesia in alligators. Drug-dosage differences appear to be related to metabolic differences between the two size-classes, requiring more research into metabolic scaling as a method of calculating anesthetic dosages.

From December, 1997, through November, 2000, 306 deaths were documented among adult and subadult American alligators (Alligator mississippiensis) of Lake Griffin, Florida (USA). Some live alligators were lethargic and unresponsive to approach. To determine the cause, we examined ten alligators captured from Lake Griffin between December 1997 and June 1999. Initially, four alligators, three of which were clinically unresponsive, were sacrificed for routine diagnostic necropsy. The other six Lake Griffin alligators, and five control alligators captured from Lake Woodruff National Wildlife Refuge, Florida, where mortality was negligible, were studied extensively by clinical neurologic examination, electromyography, hematology, serum chemical analyses, and blood culture, then sacrificed and necropsied. Samples of brain, spinal cord, peripheral nerves, skeletal muscle, and major internal organs were examined by light microscopy for abnormalities. Samples of nervous tissue also were examined by electron microscopy, and samples of various tissues were collected for toxicologic analyses. Clinical signs included swimming in circles, inability to submerge, lethargy, weakness, unresponsiveness, slow reflexes, dragging the dorsal surfaces of the hind feet, head tilt, and anisocoria. Lake Griffin alligators had significantly lower distal sciatic nerve conduction velocities than Lake Woodruff alligators, and the most severely affected alligators had the lowest velocities; but morphologic abnormalities in peripheral nerves were not evident in most cases. Three severely affected alligators had acute focal necrosis of the torus semicircularis in the midbrain, two had skeletal myofiber atrophy, another had diffuse nonsuppurative encephalomyelitis, and one mildly affected alligator had skeletal myodegeneration. The cause or causes have not yet been identified.