Respiratory depressant and skeletal muscle relaxant effects of low-dose pancuronium bromide in spontaneously breathing, isoflurane-anesthetized dogs.

OBJECTIVE: To assess and compare the respiratory depressant and skeletal muscle relaxant effects of two low doses of a nondepolarizing neuromuscular blocker, pancuronium bromide. To determine if a "low dose" of pancuronium bromide can produce selective skeletal muscle relaxation in extraocular muscles sufficient to perform intraocular surgery while sparing or minimizing depression of muscles of ventilation. STUDY DESIGN: Blinded, randomized crossover, placebo controlled study. ANIMALS: Six healthy, adult mongrel dogs weighing 20.8 +/- 1.9 kg. METHODS: Spontaneously breathing, isoflurane-anesthetized dogs received 0.02 mg/kg pancuronium bromide, intravenously (i.v.), (high dose [HD]), 0.01 mg/kg pancuronium bromide, i.v., (low dose [LD]), or saline placebo i.v. in a blinded, randomized crossover study. Indices of patient ventilation including tidal volume (Vt), respiratory rate (RR), and minute ventilation (VE) were recorded throughout the study period. Serial arterial blood gas analyses were performed at timed intervals. Neuromuscular blockade of skeletal muscle was assessed at timed intervals with train-of-four stimulus/response ratios. Eye position scores, based on the degree of ocular rotation from a neutral gaze axis, were assigned by an ophthalmologist who was blinded to the treatment given. RESULTS: VT and VE in HD dogs decreased by 82% from baseline after administration of pancuronium bromide. Similarly, Vt and VE in LD dogs decreased 40% and 55%, respectively. Decreased ventilation in HD dogs corresponded with significant (P< .05) neuromuscular blockade, as indicated by train-of-four ratio less than 75% between 0 and 60 minutes. Eye position scores in HD and LD dogs were suitable for intraocular surgery between 0 and 60 minutes. Eye position scores in five of six control dogs were unsuitable for intraocular surgery at any time period. CONCLUSIONS: LD dogs experienced only transient, mild to moderate respiratory depression compared with HD dogs, which experienced prolonged, moderate to severe respiratory depression. Both LD and HD dogs acquired and maintained eye position scores suitable for intraocular surgery between 0 to 60 minutes. A "low dose" of pancuronium bromide, which would provide adequate extraocular muscle relaxation while minimizing ventilatory depression, was not identified. CLINICAL RELEVANCE: All patients receiving any dose of neuromuscular blocking agents should be closely monitored and receive ventilatory assistance as needed.

Respiratory function and extraocular muscle paralysis following administration of pancuronium bromide in dogs.

Pancuronium bromide, a neuromuscular blocking agent, was evaluated in canine cataract surgical patients under general anesthesia to determine its effects on respiratory function and globe position. Two paralytic, anesthetic regimes were studied: one using a standard dosage of 0.066 mg kg-1 pancuronium bromide, given intravenously while providing the patient with ventilatory support, and one using a dosage of 0.022 mg kg-1 in which no ventilatory support was provided. Eye position and anterior vitreal position/displacement were recorded by a surgeon who was blinded as to treatment group. Physiological parameters indicative of respiratory function were monitored. Both dosages of pancuronium produced comparable, neutral globe position within 30 s following administration which lasted for 20-30 min. All patients in the standard dose group experienced uneventful anesthetic episodes with physiological parameters well within the normal ranges. Within 5 min after administration, all patients in the low-dose group developed a pronounced respiratory acidosis (mean arterial pH = 7.07 +/- 0.08; mean PaCO2 = 79.8 +/- 10.7 mmHg), which exceeded a set of predetermined safety limits, and subsequently these dogs received ventilatory support. We conclude that 0.022 mg kg-1 pancuronium rapidly produces an unacceptable level of respiratory acidosis and, as a result, patients receiving neuromuscular blocking agents should routinely receive ventilatory support.

Surgery for retinal detachment.

Retinal detachment surgery in human patients is currently 90% successful, with most detachments amenable to treatment by scleral buckling procedures. The main obstacle to achieving comparable results in veterinary patients is the active nature of our patients during the postoperative convalescent period. Adapting current techniques to include short-term chorioretinal adhesion by way of tacking, cyanoacrylate adhesives, or other methods has shown substantial promise and should be further investigated in veterinary species. The technology and methods are currently available to produce success rates comparable to those achieved in human patients, and the near future promises to bring further refinements in veterinary applications.

Photocoagulation of limbal melanoma in dogs and cats: 15 cases (1989-1993).

OBJECTIVE: To evaluate immediate clinical effects and long-term results of neodymium:yttrium-aluminum-garnet laser treatment of limbal melanoma in dogs and cats. DESIGN: Retrospective case series. ANIMALS: 13 dogs and 2 cats. RESULTS: At the time of treatment, 9 tumors were progressively enlarging and 4 were static. Recent growth characteristics of 2 tumors were not reported. Total energy applied ranged from 7.5 to 572 J. In all eyes, pigmented tissue shrank after treatment; however, 3 tumors recurred, 1 at 3 months and 2 at 1 year after treatment. CLINICAL IMPLICATIONS: Photocoagulation may be an effective means of treating limbal melanoma in dogs and cats.

A postretention study of patients presenting with a maxillary median diastema.

The purpose of this study was to assess postretention stability of maxillary midline diastema closure, to search for predictors of relapse, and to test for associations between relapse and other postretention changes. The sample consisted of 35 patients with pretreatment diastemas ranging from 0.9 mm to 3.0 mm (mean 1.4, SD = 0.5) following eruption of the maxillary canines. Data were gathered from treatment charts, study models, periapical radiographs, and cephalograms taken pretreatment, posttreatment, and 1 to 26 years postretention (mean 11.4, SD = 6.4). Measurable diastema relapse was observed in only 12 cases. The majority of the relapse was 0.6 mm or less, and maximum relapse was 3.0 mm. Abnormal frenums and/or intermaxillary osseous clefts did not appear to be risk factors for relapse, and no pretreatment predictors of relapse could be established. The only posttreatment change associated with diastema relapse was proclination of the maxillary incisors (p < 0.01).