Fasting horses perioperatively decreases manure production and increases time to manure output postoperatively: a controlled randomized trial.

OBJECTIVE: To compare 3 perioperative feeding regimens and their effect on anesthetic complications, manure output, and colic proportion in healthy horses. METHODS: 45 horses presenting for elective orthopedic procedures were randomly assigned to 1 of 3 groups: not fasted (NF; continuous access to hay perioperatively), fasted muzzled (FM; 10-hour preoperative fast with slow refeeding postoperatively and muzzle placement), or fasted not muzzled (FNM; same as FM without muzzle placement). Anesthetic protocol was standardized. Outcomes compared between groups included anesthesia time, arterial oxygenation, duration of hypotension, perioperative manure output, time to first passage of manure postoperatively, pain scores, and colic proportion. Comparisons were made with a mixed model and Fisher exact test with statistical significance considered at P ≤ .05. RESULTS: No differences were seen in pain scores, oxygenation, hypotension, or colic between groups. Groups FM and FNM had a significantly greater mean reduction in postoperative manure weight (-81% and -70%; P = .003) and number of manure piles (-63% and -55%; P = .005) compared to group NF (-39% and -22%; P < .001; weight and piles, respectively). Mean ± SD minutes to passage of manure postoperatively was significantly shorter in group NF (238 ± 13 minutes) than groups FM (502 ± 174 minutes; P < .001) and FNM (444 ± 171 minutes; P = .003). CLINICAL RELEVANCE: Horses with continuous access to hay prior to and following recovery from anesthesia passed more manure and passed manure sooner after surgery than their fasted counterparts without detrimental effect on anesthetic parameters and postoperative complications. Continuous access to hay perioperatively supports manure production in healthy horses without increase in anesthetic complications.

Successful surgical removal of a pheochromocytoma in a mare via trans-costal approach.

BACKGROUND: Pheochromocytomas have been previously reported in horses, but successful antemortem diagnosis and surgical removal without recurrence of clinical signs have not been described. OBJECTIVE: To report the clinical presentation, diagnostic evaluation, surgical technique, anaesthetic management and post-operative care of a mare diagnosed with pheochromocytoma. STUDY DESIGN: Clinical case report. METHODS: An 18-year-old Quarter Horse mare presented for recurrent episodes of colic, profuse sweating, muscle fasciculations and agitation over a 2-month period. Clinical, clinicopathologic and ultrasonographic (transcutaneous, transrectal) abnormalities were consistent with a unilateral left-sided adrenal mass. Surgical removal of the mass was performed via a trans-costal approach with removal of the 18th rib and retraction of the left kidney to improve exposure. Associated vasculature was ligated, and the adrenal mass was removed and submitted for histopathology and immunohistochemistry. RESULTS: A trans-costal surgical approach provided excellent visualisation of the adrenal mass and allowed for identification and ligation of associated vessels. Total surgical and anaesthesia time were 86 and 114 min, respectively. Several intraoperative (hypertension, tachycardia) and post-operative (colic with tachycardia, tachypnea, large colon pelvic flexure impaction and nasogastric reflux) complications were encountered and managed successfully. Immunohistochemistry demonstrated positive labelling for synaptophysin and chromogranin A, confirming diagnosis of pheochromocytoma. The mare had recovered well at 6-week recheck post-operatively and returned to training at 6 months post-operatively. No further clinical signs consistent with pheochromocytoma have been observed following removal. CONCLUSIONS: The trans-costal approach allowed for surgical removal of a pheochromocytoma in a mare. Surgical removal of adrenal masses in horses may be associated with complications yet was successfully performed without subsequent recurrence of clinical signs associated with tumour presence and return to athletic use in this mare.

Cardiopulmonary function and intestinal blood flow in anaesthetised, experimentally endotoxaemic horses given a constant rate infusion of dexmedetomidine.

BACKGROUND: Endotoxaemia causes untoward inflammatory-mediated effects that might be attenuated by dexmedetomidine. OBJECTIVES: To evaluate the effects of a dexmedetomidine intravenous (IV) infusion on systemic and intestinal haemodynamics and arterial blood gas values in sevoflurane-anaesthetised horses administered Escherichia coli O55:B5 lipopolysaccharides (LPS). STUDY DESIGN: Randomised controlled in vivo experiment. METHODS: A total of 13 horses weighing 456 ± 86 kg (mean ± standard deviation) and aged 13.9 ± 9.0 years donated for euthanasia underwent ventral midline celiotomy using sevoflurane anaesthesia. Baseline physiological variables were recorded after a 90-minute equilibration period. All horses were given 0.1 mcg/kg bwt LPS IV. Horses were randomly assigned to no further treatment (group LPS; seven horses) or IV administration of dexmedetomidine (loading dose 1.75 mcg/kg bwt followed by 1.75 mcg/kg bwt/h; group LPS-Dex; six horses) with concurrent target sevoflurane dose reduction of 50%. Cardiac index (CI; thermodilution), intestinal blood flow, arterial blood parameters and plasma dexmedetomidine concentration measurements were recorded every 30 minutes until euthanasia at 390 minutes. Data were compared between and within groups to baseline using a mixed model analysis (significance P < .05). RESULTS: In LPS-Dex horses, intestinal blood flow and CI were transiently decreased after the dexmedetomidine loading dose, but no significant differences were found compared with baseline during the infusion. Sevoflurane dose was reliably reduced by approximately 40%. Significant differences were identified in creatinine (115  umol/L LPS-Dex; 195 umol/L LPS), bicarbonate (29.7 mmol/L LPS-Dex; 23 mmol/L LPS) and base excess (2.0 mmol/L LPS-Dex; -5.3 mmol/L LPS). Dexmedetomidine plasma concentrations were highest after the loading dose and stable during infusion dosing. MAIN LIMITATIONS: Experimental conditions are not reflective of clinical colic management. CONCLUSIONS: A dexmedetomidine infusion with sevoflurane dose reduction attenuated some deleterious changes in anaesthetised horses administered LPS without sustained negative cardiovascular effects and may be beneficial during colic surgery.