Post Operative Management of Portosystemic Shunts

Gradual shunt occlusion systems are attractive for two main reasons. Firstly, the largely unproven theory that gradual occlusion would lead to more successful development of the intrahepatic portal vasculature and secondly, to minimize the risk of post operative complications. Occasionally, however, gradual occlusion techniques can result in acute and chronic portal hypertension through uncontrolled shunt thrombus formation or malposition of the occlusion device. Although most would agree that the number of post operative complications that require an intervention, is less with gradual occlusion systems, they can occasionally occur. It is essential, therefore, that the surgeon performing surgery on any animal with a portosystemic shunt is aware of what complications are possible, how to recognize and treat them.

Immediate Post-operative management
Regardless of technique used, these patients require careful monitoring for the first 24 hours, at least. Balanced electrolyte fluids are administered at a maintenance rate of 2-4 ml/kg/hr initially.

Patient monitoring
Body temperature, pulse and respiratory rate, mucous membrane colour and capillary refill time should be monitored every two to four hours.
Packed cell volume, serum total solids and blood glucose should be checked at similar time intervals.
Serum electrolytes, urine output, abdominal circum- ference and intra-abdominal pressure can all yield useful information and should ideally be measured intermittently.
Serial evaluation of the animals mental status is also desirable. These patients will commonly benefit from plasma, blood products, synthetic colloid, potassium, and glucose to help normalize intravascular volume, colloid osmotic pressure and electrolyte disturbances.

Complications
Portal hypertension
Suture ligation techniques rely on the deliberate creation of an acute increase in portal pressure, to encourage blood flow towards the liver. Gradual attenuation techniques intend to produce a similar effect over a protracted period of time. With any of these techniques, kinking of the shunt vessel by the attenuation/occlusion device, and acute thrombus formation can result in uncontrol- led shunt occlusion and potentially life-threatening portal hypertension. Abdominal distention is common following PSS ligation or attenuation. The distention is presumed to be ascitic fluid which has developed secondary to increased portal pressure. If abdominal distention is not associated with any other clinical deterioration, it can be left untreated. If, however, the abdominal distention is associated with pain, circulatory collapse or hemorrhagic diarrhoea, and, if the patient fails to stabilize with intravenous circulatory support, a repeat laparotomy is indicated. In the latter situation the ligature or device around the PSS must be removed. [...]