EQUINE VETERINARY EDUCATION Equine vet. Educ. (2020) 32 (11) 567 doi: 10.1111/eve.13103_1
Case Report
Intra-splenic administration of phenylephrine in a horse to induce splenic contraction ina case of nephrosplenic entrapment of the large colon non-responsive to intravenous phenylephrineadministration
K. Loomes* and J. Anderson
Rainbow Equine Hospital, Malton, North Yorkshire, UK *Corresponding author email:
kate@rainbowequinehospital.co.uk Keywords: horse; nephrosplenic entrapment; phenylephrine; left dorsal displacement; spleen
Summary
This case report describes the successful use of intra- operative intra-splenic phenylephrine (PE) administration to reduce splenic dimensions after the apparent failure of intraoperative intravenous (i.v.) administration to induce splenic contraction in a horse undergoing surgical correction of nephrosplenic entrapment under general anaesthesia. A 550 kg 6-year-old Warmblood gelding presented with a 6-
h duration of colic signs unresponsive to analgesia. Abdominal ultrasonography confirmed the presence of gas filled colon along the body wall displacing the spleen axially. No left renal silhouette was visible. Rectal palpation findings were consistent with nephrosplenic entrapment of the left dorsal colon. Intravenous PE (3 lg/kg/min) wasadministered over 15 min and the horse was lunged for 15 min. Nephrosplenic entrapment of the left dorsal colon persisted despite further lungeing and repeat administration of i.v. PE (3 lg/kg/min) 4 hours later. Considering the persistence of the colon displacement and the increasing level of abdominal discomfort, surgical intervention wasperformedunder generalanaesthesia. Flunixin (1.1 mg/kg bwt i.v.), polymixin B (6000 IU/kg bwt),
procaine penicillin (20 mg/kg i.m.) and gentamicin (8.8 mg/kg bwt i.v.) were administered. Pre-anaesthetic medication consisted of romifidine (50 lg/kg bwt i.v.) and morphine (0.2 mg/kg bwt i.v.) before the induction of general anaesthesia using ketamine (2.2 mg/kg bwt i.v.) and diazepam (0.05 mg/kg bwt i.v.). Endotracheal (ET) intubation was performed and the horse was positioned in dorsal recumbency on the operating table and a circle anaesthetic breathing system was connected to the ET
tube.General anaesthesia was maintained using isoflurane delivered in 100% oxygen via a large animal circle breathing system. An i.v. lidocaine infusion was administered (loading dose (1.3 mg/kg i.v.) followed by an infusion rate of 50 lg/kg/min i.v.). Following clipping and sterile preparation of the skin and
draping, a 30-cm midline incision was made from the umbilicus cranially. Following entry through the linea alba into the abdomen, the large colon was found to be draped over the left nephrosplenic ligament. The spleen was enlarged and engorged and it was not possible to dis-entrap the large colon manually. Intravenous administration of 24 mg of PE over 15 min (3 lg/kg/min) was carried out which resulted in no observable alteration in splenic dimension despite an elevation in systemic arterial blood pressure. Continued efforts were made to free the large colon from the nephrosplenic space which were unsuccessful. Within 60 s of i.v. PE administration, mean arterial pressure (MAP) increased from
72 to 92 mmHg as a result of peripheral vasoconstriction but there was no observable change in splenic dimension. Arterial blood pressure values remained elevated for 15 min during the infusion duration and once the PE infusion was ceased, MAP returned to 75 mmHg after a further 10 min. Resolution of the entrapped portion of the colon was not possible without reduction in splenic size. The large colon was exteriorized and a pelvic flexure enterotomy was then performed prior to replacing the colon in the abdomen. Intra- splenic administration of PE (10 mg) was performed. A 21 gauge 1.5 inch needle was used to penetrate the splenic capsule on its visceral surface and 10mg PE was injected over 60 s. This resulted in an immediate increase in MAP to 85 mmHg and then to 105 mmHg. Seven minutes after intra- splenic PE administration, MAP returned to 72 mmHg. A significant reduction in splenic size allowed the colon to be dis-entrapped from the nephrosplenic space. The colon was then re-exteriorised and placed into normal position. The abdomen was lavaged and closed in three layers. The horse recovered uneventfully from general anaesthesia
and resolution of the colon displacement was confirmed via rectal palpation. Although the lack of adverse effects in one patient
provides insufficient evidence for future use, our report may demonstrate an effective alternative means to administer PE intra-operatively and reduce the size of the spleen, thereby correcting the otherwise uncorrectable displacement after attempts to correct the entrapment have been unsuccessful and intravenous PE has failed.
Key points
• Colic due to nephrosplenic entrapment of the large colon has a reported incidence of 3–9% in equine referral centres.
• Conservative options include withholding feed, oral or i.v. rehydration, spasmolytic agents, i.v. PE, lungeing/ trotting exercise and/or rolling under general anaesthesia. Surgical exploratory laparotomy may be required if conservative treatment is unsuccessful or prompt intervention is warranted.
• Administration of i.v. PE is not without risk. Reported adverse effects include spontaneous abdominal and/ or thoracic haemorrhage. In anaesthetised horses, PE causes systemic vasoconstriction, reduced cardiac output, tissue oxygen delivery and intestinal perfusion.
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