Post-anesthetic pulmonary edema in two horses.

CASE 1: A two-year old, 462 kg Standard bred horse was anesthetized for arthroscopy and castration. During anesthesia, hyperemia of the mucosal membranes and urticaria were noticed. During 5 hours of anesthesia subcutaneous edema of the eyelids and neck region developed. In the recovery box, the orotracheal (OT) tube was left in situ and secured in place with tape. Following initial attempts to stand, the horse became highly agitated and signs consistent with pulmonary edema developed subsequently. Arterial hypoxemia (PaO(2): 3.7 kPa [28 mmHg]) and hypocapnia (PaCO(2): 3.1 kPa [23 mmHg]) were confirmed. Oxygen and furosemide were administered. The horse was assisted to standing with a sling. Therapy continued with bilateral intra-nasal oxygen insufflation. Ancillary medical therapy included flunixin meglumine, penicillin, gentamycin and dimethylsulfoxide. Following 7 hours of treatment the arterial oxygen tensions began to increase towards normal values. CASE 2: An 11-year old, 528 kg Paint horse was anesthetized for surgery of a submandibular mass. The 4-hour anesthetic period was unremarkable. The OT tube was left in situ for the recovery. During recovery, the horse was slightly agitated and stood after three attempts. Clinical signs consistent with pulmonary edema and arterial hypoxemia (PaO(2): 5 kPa [37.5 mmHg]) subsequently developed following extubation. Respiratory signs resolved with medical therapy, including unilateral nasal oxygen insufflation, furosemide, flunixin meglumine and dimethylsulfoxide. The diagnosis of pulmonary edema in these horses was made by clinical signs and arterial blood-gas analysis. While pulmonary radiographs were not taken to confirm the diagnosis, the clinical signs following anesthesia support the diagnosis in both cases. The etiology of pulmonary edema was most likely multifactorial.

Hemodynamic effects of an intravenous infusion of medetomidine at six different dose regimens in isoflurane-anesthetized dogs.

This study investigated the dose dependency of the hemodynamic effects of IV medetomidine (MED) constant-rate infusion (CRI) during isoflurane anesthesia. Twenty-four healthy beagles randomly received one of six MED CRI regimens. A loading dose of MED was administered IV at 0.2, 0.5, 1.0, 1.7, 4.0, or 12.0 ug/kg-1 for 10 minutes, followed by a maintenance CRI providing identical dose amounts over 60 minutes. Heart rate and mean arterial blood pressure were recorded, blood gases were analyzed, and cardiac index (CI) was determined. Statistical analysis involved a repeated measures linear model. Baseline CI demonstrated a dose-dependent decrease as the MED dose increased, with decreases of 14.9% (SD, 12.7%), 21.7% (17.9%), 27.1% (13.2%), 44.2% (9.7%), 47.9% (8.1%), and 61.2% (14.1%) at doses of 0.2, 0.5, 1.0, 1.7, 4.0, and 12.0 ug/kg-1, respectively. The four lowest doses induced limited and transient changes in heart rate, mean arterial pressure, and CI. Further investigation into potential perioperative uses of MED CRI is warranted.

The use of lingual venous blood to determine the acid-base and blood-gas status of dogs under anesthesia.

OBJECTIVE: To assess the suitability of lingual venous blood (LBG) as an alternative to arterial blood (ABG) samples in determining acid-base balance and blood-gas status in dogs anesthetized for elective procedures and with medetomidine and isoflurane administration under experimental conditions. STUDY DESIGN: Prospective, randomized clinical and experimental study. ANIMALS: Clinical population of 18 ASA I/II dogs for elective surgery and five healthy Beagles (3 females and 2 males) for the experimental study. METHODS: Blood sampling was simultaneously performed at dorsal pedal arterial and lingual venous sites, generating paired data. Two paired samples were collected from each dog in the clinical part and four from each dog in the experimental part (two during isoflurane anesthesia and two during isoflurane plus medetomidine). A modified Bland and Altman method was used to examine data from the clinical part and the experimental data were subjected to a paired sign's test following transformation where appropriate. RESULTS: The pH of LBG overestimated ABG, with limits of agreement of (-0.01, 0.02). The partial pressure of carbon dioxide (PCO(2)) of LBG overestimated ABG by 0.6 mmHg [0.1 kPa], with limits of agreement of (-3.5, 4.6) mmHg [-0.5, 0.6 kPa]. The partial pressure of oxygen (PO(2)) of LBG underestimated ABG by 86.3 mmHg [-11.5 kPa], with limits of agreement of (-199.8, 27.3) mmHg [-26.6, 3.6 kPa]. During medetomidine administration values for PO(2) (p = 0.03) and lactate (p = 0.03) were lower for LBG when compared with ABG. The LBG value of PO(2) was lower (p = 0.03) during medetomidine and isoflurane administration versus isoflurane alone. CONCLUSIONS AND CLINICAL RELEVANCE: The pH and PCO(2) of LBG samples provide clinically acceptable substitutes of ABG samples in the dog population studied. The wider limits of agreement for PO(2) render it less reliable as a substitute for ABG. The difference in PO(2) identified between LBG and ABG during medetomidine administration may not preclude the use of LBG as substitutes for ABG samples.

Survey of utilization of medetomidine and atipamezole in private veterinary practice in Quebec in 2002.

This survey evaluates early perceptions about the use of medetomidine and atipamezole among veterinary practitioners in Quebec in 2002. Response rate was 23.5%; 71.1% of the practitioners did not use these products because of lack of information (69.3%), unavailability of the drugs in the practice (23.3%), or other reasons (7.3%), including concerns about the safety of alpha-2 agonists. Most veterinarians who used these products (70.4%) used them only rarely. Sedation by medetomidine was qualified as good (44.2%) or excellent (36%), and analgesia as good (46.5%) or average (32.7%). Waking up after atipamezole was qualified as good (47.5%) or excellent (40.9%). These perceptions indicate an opportunity for wider use of the products in veterinary practice. With more education and experience, practitioners could find medetomidine hydrochloride alone or in combination with an opioid useful for sedation, analgesia, and premedication for healthy animals. Reversal with atipamezole hydrochloride is considered effective, when residual sedation is undesirable.

Evaluation of epidural administration of morphine or morphine and bupivacaine for postoperative analgesia after premedication with an opioid analgesic and orthopedic surgery in dogs.

OBJECTIVE: To evaluate the analgesic efficacy of epidural administration of morphine or a morphine-bupivacaine combination administered before orthopedic surgery in dogs that received opioid premedication. DESIGN: Prospective, randomized, blinded, clinical study. ANIMALS: 36 healthy adult dogs that underwent elective orthopedic surgery on a pelvic limb. PROCEDURES: Each dog received 1 of 3 epidural treatments before surgery. Anesthetic and supportive care protocols were standardized. Dogs under going different surgical procedures were randomly allocated among the 3 treatment groups. Respiratory and cardiovascular variables, end-tidal isoflurane concentration, and requirements for rescue analgesia were monitored. Postsurgical analgesia was evaluated with a multiparametric pain scoring system and by determination of rescue analgesia requirements and cortisolemia. RESULTS: The morphine-bupivacaine combination was associated with lower values than morphine or a saline solution for intraoperative arterial blood pressure; minimum and maximum isoflurane requirements; and postoperative pain scores, rescue analgesia requirements, and plasma cortisol concentrations. Values obtained after administration of morphine alone were not significantly different from those obtained after administration of saline solution for most variables. CONCLUSIONS AND CLINICAL RELEVANCE: The preoperative epidurally administered morphine-bupivacaine combination induced better analgesia than morphine alone and should be considered for use in clinical patients. The degree of hemodynamic depression associated with the combination was considered acceptable for healthy patients undergoing elective surgery.

Sudden cardiac death associated with occult hypertrophic cardiomyopathy in a dog under anesthesia.

A 6-year-old, 3.0 kg, neutered female, Yorkshire terrier was referred for orthopedic surgery. Cardiac arrest followed unsuccessful treatment of bradycardia and systemic arterial hypotension under general anesthesia. Postmortem examination revealed hypertrophic cardiomyopathy. A possible relationship between treatment of bradycardia, systemic arterial hypotension, and sudden cardiac death is described.

Results of preemptive epidural administration of morphine with or without bupivacaine in dogs and cats undergoing surgery: 265 cases (1997-1999).

OBJECTIVE: To determine prevalence of adverse effects associated with epidural administration of morphine with or without bupivacaine in dogs and cats undergoing surgery and evaluate effects of epidural administration of morphine on postoperative pain severity. DESIGN: Retrospective study. ANIMALS: 242 dogs and 23 cats. PROCEDURE: Morphine with or without bupivacaine was administered prior to surgery with a Tuohy needle, spinal needle, or epidural catheter. In 18 dogs that underwent surgery twice, results of preemptive epidural administration of morphine with or without bupivacaine were compared with results of systemic administration of oxymorphone and ketoprofen. RESULTS: The delivered fraction of isoflurane was significantly lower in animals given morphine and bupivacaine than in animals given morphine alone. Analgesia was of significantly longer duration in dogs given morphine and bupivacaine than in dogs given morphine alone. During anesthesia, mild respiratory and cardiovascular depression was reported. Seven dogs and 2 cats had urine retention, and 2 dogs developed pruritus. Six dogs vomited when a second dose of morphine was given epidurally the day after surgery. Eight of 72 dogs had delayed hair growth. In 18 dogs that underwent surgery twice, the delivered fraction of isoflurane was significantly lower and the duration of analgesia was significantly longer when morphine with or without bupivacaine was given epidurally than when oxymorphone and ketoprofen were given. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that preemptive epidural administration of morphine with or without bupivacaine is a safe and effective method of inducing long-lasting analgesia in dogs and cats and is superior to standard management of postoperative pain with repeated injection of oxymorphone and ketoprofen.