Neuromuscular blockade with rocuronium bromide for ophthalmic surgery in horses

Purpose The production of a central eye to ease surgical access for intraocular surgery is generally dependent on the depth of anesthesia. The aim of this study was to evaluate the eyeball position under muscle relaxation with rocuronium during general anesthesia. Material and methods Twenty horses, body weight 480 ± 62 kg; age 12.6 ± 6.2 years (mean ± SD) were anesthetised for various ophthalmic surgeries. Horses were premedicated with acepromazine, xylazine, and butorphanol intravenously and anesthesia induced with ketamine and diazepam. Anesthesia was maintained with isoflurane in 100% oxygen and 0.6 mL/kg/h of an infusion containing midazolam, ketamine, and xylazine diluted in 500 mL 0.9% NaCl. Horses were mechanically ventilated. Neuromuscular function was assessed with an acceleromyograph (TOF‐Guard^®) and the N. peroneus superficialis was stimulated every 15 s with a train‐of‐four stimulation pattern. A dose of 0.3 mg/kg rocuronium was administered intravenously. The changes in the eyeball position were recorded. Results The dose of 0.3 mg/kg rocuronium produced a 100% neuromuscular block in all horses. Onset time and clinical duration of block was 2.38 ± 2.02 min (range 0.5–8) and 32 ± 18.6 min (range 7.7–76.2), respectively. The globe rotated to central position within 31 ± 2.8 s. The whole iris was visible after 42 ± 7.7 s in all horses. No additional bolus of rocuronium was necessary for any surgery. Conclusion Neuromuscular blockade with rocuronium bromide can be used safely to facilitate ophthalmic surgery in equines.     

Anesthesia and surgery of laboratory animals

This article reviews anesthetics and anesthetic techniques applicable to small laboratory animals. Anesthetic and analgesic dosage tables are presented for each species to guide the practitioner. The actions of the various agents are reviewed in the text, and key references are presented. Surgical considerations are also reviewed.     

Significance of the oculocardiac reflex during ophthalmic surgery in the dog

Antimuscarinic drugs were intentionally excluded from the anaesthetic protocol used in 72 dogs undergoing a variety of ophthalmic surgical procedures. Following premedication with acepromazine and morphine, anaesthesia was induced with thiopentone and maintained with halothane vaporised in oxygen and nitrous oxide. Muscle relaxation was achieved in all dogs using either vecuronium or atracurium and ventilation was controlled to produce mild hypocapnia. Only one patient showed electrocardiographic and arterial blood pressure changes that could be attributed to the oculocardiac reflex. This indicates that the reflex is of minor clinical importance when anaesthesia results in good muscle relaxation, mild hypocapnia and adequate unconsciousness. When these conditions are present the routine use of atropine or glycopyrrolate is unwarranted during ocular surgery in the dog.     

Effects of two preanesthetic regimens for ophthalmic surgery on intraocular pressure and cardiovascular measurements in dogs

The effects of different preanesthetic medications (acepromazine plus either meperidine or butorphanol) given before the induction of anesthesia with midazolam and ketamine on intraocular pressure, heart rate, and arterial blood pressure were investigated in 20 dogs. Following administration of preanesthetics and induction of anesthesia, dogs were intubated and anesthesia was maintained with halothane for 10 minutes. Intraocular pressure was significantly higher (P <.05) at several evaluations for dogs premedicated with acepromazine/meperidine than for those premedicated with acepromazine/butorphanol. Mean heart rate and diastolic arterial blood pressure were significantly (P <.05) higher 5 minutes after administration of acepromazine/meperidine than after acepromazine/butorphanol. Results of this study suggest that acepromazine/butorphanol is a satisfactory preanesthetic combination to use before induction of anesthesia with midazolam and ketamine for ophthalmic surgery in dogs.     

Anesthesia in Caspian ponies

ObjectiveTo evaluate some of the clinical and laboratory parameters following diazepam–acepromazine, thiopental, and halothane anesthesia in Caspian ponies.Study designProspective experimental trial.AnimalsSix healthy Caspian ponies of both sexes, aged 11 ± 3 years and weighing 318 ± 71 kg.MethodsThe ponies were pre-medicated with diazepam (0.2 mg kg⁻¹) and acepromazine (0.05 mg kg⁻¹) IV. Sodium thiopental 5% was administered IV, 10 minutes later and anesthesia was maintained with halothane in oxygen for 1 hour. Heart and respiratory rates, mean arterial blood pressure, cardiac rhythm, and signs of anesthetic depth were monitored during anesthesia. Hematological and serum biochemical parameters were evaluated before anesthesia and at 1, 2, 3, 24, 48, 72, and 96 hours. Urine specific gravity and cytology were evaluated at the same intervals following anesthesia. Parametric data were analyzed using repeated measures anova.ResultsConsiderable sedation/tranquilization without excitement was achieved following pre-medication. Heart rate significantly increased and mild hypotension occurred during anesthesia. Sinus arrhythmia and second degree AV block occurred in five horses. Respiratory rate decreased during anesthesia, with an accompanying respiratory acidosis. Body temperature also decreased. Recovery was scored ‘good’ in four horses and ‘satisfactory’ in the other two. Blood urea nitrogen concentration was significantly increased at 1–3 hours post-anesthesia. Blood glucose was significantly increased at 48, 72, and 96 hours, and creatine kinase and aspartate aminotransferase were significantly increased at 24 and 48 hours post-anesthesia.Conclusion and clinical relevance This simple anesthetic protocol can be used in Caspian ponies and an acceptable anesthetic with a reasonable recovery can be expected.     

Anesthesia in the Llama

Anesthesia for llamas is similar to other domestic species, although adjustments in technique are required to allow for species variations. Xylazine (0.4-0.6 mg/kg) is well tolerated for sedation. The thiobarbiturates (8-10 mg/kg), ketamine (2.5-5.0 mg/kg), or combinations of guaifenesin and thiobarbiturates or guaifenesin and ketamine (to effect) can be used for induction of anesthesia. In juvenile or debilitated animals, anesthesia can be induced with halothane or isoflurane administered by mask. After tracheal intubation, anesthesia can be maintained with the inhalation agents, usually halothane or isoflurane. Supportive therapy and many anesthetic monitoring techniques used in domestic animals can be used in llamas. While under marginal planes of anesthesia, llamas can have more active physiologic responses to pain, including bradycardia and vasoconstriction, than domestic animals. Llamas are more prone to airway obstruction after tracheal extubation than domestic ruminants but otherwise recover as well from general anesthesia as domestic ruminants.     

Clinical Anesthesia in Reptiles

The clinical use of anesthetic agents in reptiles presents a number of unique challenges because of the diversity of the class Reptilia with respect to natural history, size, anatomy, and physiology. Reptiles are commonly maintained as companion animals, widely displayed in zoological institutions, and many species serve as subjects in laboratory facilities. Therefore, to become a skillful clinician, developing an understanding of anesthetic efficacy across reptile species is important. The objective of this review is to provide a current perspective on the practical application of anesthetic agents in commonly maintained pet reptile species.