Preparation and positioning
Once a decision has been made to proceed to surgery , the horse ' s mouth should be flushed to remove any food debris , which could be pushed into the trachea during endotracheal intubation and lead to pneumonia [ 1 ] . Patient positioning and skin preparation are critical steps in preparation for all surgeries , but in the case of colic surgery these steps require special attention due to the length of the surgery , risk of contamination and size of the incision [ 7 ] . The horse will be positioned in dorsal recumbency for a ventral midline surgical approach . It is important to position the horse straight and forward on the table , to allow the VS unrestricted ease of access to the midline during the surgery , with the incision extending cranially from the umbilicus [ 7 ] . In specific situations , such as for a caesarean section , the incision may be extended caudally from the umbilicus .
The horse should be well supported and padded on all large muscle masses to reduce the risk of myopathy [ 7 , 8 ] . Foam padding , air-filled cushions or water beds can be used as supportive padding [ 7 , 8 ] . The limbs should be tied down , loosely but securely , in case the horse should move during surgery [ 7 , 8 ] ( Figure 1 ). Rectal sleeves should be placed over the horse ' s hooves to act as a further hygiene barrier between the surgical drapes and the hooves [ 7 , 8 ] ( Figure 1 ). The authors recommend VNs have emergency colic surgical equipment routinely prepared overnight to save valuable time in these emergency situations .
Skin preparation
The prevalence of surgical-site infections following exploratory laparotomy is estimated to be 3 – 20 %, but as high as 57 % in cases of repeat laparotomy [ 3 ] . Horses with heavily soiled coats should be bathed or groomed prior to surgery , as attempting to remove dirt after surgery is likely to contaminate the wound [ 7 ] .
While awaiting confirmation for surgery , attempts can be made to clip the horse ' s ventral abdomen prior to induction of anaesthesia , if it is deemed safe , to help reduce the anaesthesia time [ 1 ] . The ventral abdomen should be clipped , using a size 40 blade , from caudal to the xiphoid process to caudal to the umbilicus , and laterally to the margins of the ribcage and flank folds [ 7 ] . When clipping inside the theatre , a vacuum cleaner can be used to remove the discarded hair [ 7 ] .
A urinary catheter can be placed in the patient to avoid bladder discomfort during recovery from anaesthesia . For male patients , the prepuce should be sutured closed to prevent the risk of urine contaminating the surgical field during surgery [ 1 ] . The catheter and urine collection bag should run between the hind legs and be positioned at the back of the horse to avoid interference with the surgical field [ 7 ] . The skin should be aseptically prepared using a ‘ target ’ pattern , starting on the midline and working outwards ( Figure 1 ).
It is advisable to carry out a gross scrub for 5 minutes , until visible dirt is removed , followed by a surgical scrub for a further 5 minutes of contact time [ 7 , 8 ] . Chlorhexidine gluconate is deemed superior to povidone-iodine as it has a wide antimicrobial range and has a longer residual action . Concentrations as low as 0.4 % can be used and it is minimally inhibited in the presence of organic materials [ 7 ] . Current guidelines recommend a minimum of two scrub cycles for surgical skin preparation using chlorhexidine gluconate [ 8 ] . Gauze swabs and disposable sponges are non-linting and do not leave residual debris , which could potentially be introduced into the abdomen [ 9 ] . Between scrub cycles , it is recommended that 70 % isopropyl alcohol is used , as it has a rapid bactericidal effect and does not inhibit the efficacy of chlorhexidine gluconate [ 9 ] . A chlorhexidine-isopropyl alcohol-based solution can be made in-house or purchased commercially for use as a final preparation solution [ 8 ] . It is recommended that the final preparation solution be applied in a sterile fashion , using sterile gloves and sterile gauze swabs [ 7 ] .
Draping
Figure 1 . A horse placed in dorsal recumbency , undergoing aseptic preparation of the ventral midline for emergency exploratory laparotomy . Note the rectal sleeves over the hooves , the limbs loosely tied down , and the colon tray between the hind limbs .
There are several sets of equine-specific disposable laparotomy drapes commercially available . The sets contain impervious table drapes , leg covers , an impervious laparotomy drape , an adhesive incise drape and extra waterproof drapes [ 7 ] . A sterile waterproof table drape is required for the instrument table [ 7 ] . The
26 Veterinary Nursing Journal