EQUINE VETERINARY EDUCATION / AE / SEPTEMBER 2017


481


Case Report


Anastomosis of the medial digital artery in a mare following traumatic laceration


C. M. Isgren* and P. I. Milner† Philip Leverhulme Equine Hospital, School of Veterinary Science, University of Liverpool, Neston, UK; and †Department of Musculoskeletal Biology, Institute of Ageing and Chronic Disease, University of Liverpool, Neston, UK.


*Corresponding author email: cisgren@liv.ac.uk Keywords: horse; wound; trauma; distal limb; laceration; arterial anastomosis


Summary A 7-year-old Warmblood mare presented with blood loss from a laceration of the medial digital artery sustained in the field. The mare was initially managed conservatively by pressure bandaging but the bleeding did not stop. After a blood transfusion the mare underwent arterial repair under general anaesthesia and was initially managed in a cast post operatively. Doppler ultrasonography 4 days post operatively confirmed effective blood flow distal to the arterial anastomosis and the mare was discharged from the hospital. At 6 months follow-up the owner reported that the mare was sound at the trot with an excellent cosmetic outcome of the surgical site.


Case history


A 7-year-old Warmblood showjumping mare (536 kg) was presented to the Philip Leverhulme Equine Hospital, University of Liverpool for assessment of acute blood loss associated with a full thickness laceration of the medial aspect of the left hind metatarsophalangeal region. The mare had been found collapsed in a field with marked blood loss evident. Prior to referral the mare had received resuscitation fluids including hypertonic saline 7.2% and crystalloid fluids and a pressure bandage placed over the site of the laceration.


Clinical findings


Physical examination revealed the mare to be quiet but alert with a heart rate of 60 beats/min, packed cell volume 24% and total protein 32 g/l. Evaluation of the wound following removal of the dressing revealed a continuous flow of arterial blood through the laceration. Procaine penicillin (Depocillin 300 mg/ml suspension for


injection)1 14 mg/kg bwt i.m. and gentamicin sulphate (Genta Equine 100 mg/ml solution)2 6.6 mg/kg bwt i.v. was administered and a dressing, consisting of a nonadhesive, absorbent primary layer (Allevyn 10 9 10 cm)3 and 3 conforming layers (cotton wool roll,4 Knitfix10 9 4m5) was applied over the distal limb. At this point, the blood loss was controlled and the mare was admitted for overnight monitoring. The mare remained comfortable overnight with no significant further blood loss. However, on removal of the dressing, blood loss through the wound returned and surgical stabilisation of the damaged vessel was recommended. Anaesthesia was induced using ketamine hydrochloride (Narketan 10, 100 mg/ ml solution for injection)6 2.2 mg/kg bwt i.v. and diazepam (Diazepam injection 5 mg/ml)7 0.06 mg/kg bwt i.v. following premedication using romifidine (Sedivet 10 mg/ml solution for


injection for horses)8 0.06 mg/kg bwt i.v. and morphine (Morphine Sulphate 30 mg/ml injection)9 0.2 mg/kg bwt i.v. Epidural analgesia was performed using methadone (Physeptone 10 mg/ml)10 0.1 mg/kg bwt and morphine (Morphine Sulphate 30 mg/ml injection)9 0.1 mg/kg bwt prior to induction. The mare was intubated with an endotracheal tube (size 30 mm) and a suitable plane of anaesthesia maintained using isoflurane. A total of 2 l whole blood was administered during anaesthesia. An Esmarch bandage was placed in tourniquet fashion in the proximal metatarsal region of the left hindlimb. Following aseptic preparation of the distal limb, the 3 cm horizontal laceration over the medial aspect of the medial proximal sesamoid bone was converted into a Z-shaped incision to identify the proximal and distal margins of the lacerated medial digital artery. The free ends were dissected free from the surrounding loose connective tissue and the proximal portion of the artery tourniqueted using a Penrose drain. Stay sutures were placed at the dorsal and plantar margins of the proximal and distal portions of the lacerated vessels using 0.7 M (6-0 USP) polyglactin 910 and a 14 gauge catheter (Intraflon 2, 36 mm)11 placed into the distal portion to maintain patency (Fig 1a) after removal of any visual thrombi. Following withdrawal of the catheter in the distal portion, sutures were placed through the wall of the tunica media and intima in a simple continuous pattern, interrupted at 180°, starting with the axial (far) part of the vessel and continuing to close the abaxial (near) half (Fig 1b). Patency of the anastomosis was verified through intra-arterial injection of 0.9% saline. The outermost layer, the tunica adventitia, was closed separately in a continuous pattern using 0.7 M polyglactin 910, similarly interrupted at 180°. Subcutaneous tissues were debrided and closed using 3 M polyglactin 910 in a simple continuous pattern followed by an intradermal layer using 3.5 M polyglycolic acid and skin using 4 M polypropylene. The mare was recovered from anaesthesia in a distal limb cast which was removed 48 h post operatively and replaced with a distal limb bandage. After a further 48 h, Doppler ultrasound examination of the medial digital artery was performed which confirmed effective flow through the vessel distal to the repair (Fig 2). The horse remained on systemic antimicrobials until discharge from the clinic, 5 days after initial admission. Once discharged from the hospital the horse was managed with regular dressing changes until suture removal. There was mild discharge from the surgical site at the time of suture removal. At 6 months follow-up after surgery the mare has remained sound and the owner reports an excellent cosmetic result of the surgical site. Further ultrasonographic evaluation to


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