Table 14.2. Laboratory tests during liver transplantation

Arterial blood gas analysis and acid-base state Electrolyte levels (Na+, K+, Ca++, Cl-) Blood glucose level Thromboelastography (TEG)

Platelet count, prothromin time (PT), partial thromboplastin time (PTT), fibrinogen of the inferior vena cava; and yet others use it in virtually all patients. Another technique is side-clamping of the inferior vena cava to allow end-to-side anastomosis of donor cava to recipient cava (piggy-back technique). Although this technique was designed to maintain flow in the inferior vena cava, the side-clamping usually results in a significant reduction in blood flow. Venovenous bypass is infrequently used in pediatric liver transplantation.

Hemodynamic Management

Most anesthesiologists feel that the circulation has to be maintained hyperdy-namic perioperatively in order to maintain tissue perfusion. However, this may not be possible during the anhepatic stage, because venous return is significantly reduced when the inferior vena cava is clamped, even if venovenous bypass is used. During the preanhepatic stage, hypotension is most commonly due to hypovolemia related to bleeding and insensible fluid losses, and is treated by fluid administration. Ionized calcium concentrations should be normalized by the administration of calcium chloride. Determination of RVEDV and transesophageal echocardiography (TEE) may help when the interpretation of more routine hemodynamic monitoring is difficult. Small amounts of vasoconstrictors/inotropic agents (dopamine, epinephrine) are rarely necessary to maintain an adequate perfusion pressure.

During the anhepatic stage, when cardiac output is lower, there is a compensatory increase in systemic vascular resistance, usually resulting in preserved blood pressure. There are several different surgical techniques of handling the inferior vena cava during this stage: simple cross-clamping, side-clamping of the inferior vena cava (piggy-back), and the use of venovenous bypass. The latter techniques result in a smaller decrease in the heart's preload. On graft reperfusion, there is more of an increase in venous return with the simple cross-clamping technique, and therefore fluid management before unclamping of the vessels and graft reperfusion has to take this into account to prevent hypervolemia after graft reperfusion.

The neohepatic stage starts with unclamping of the portal vein and inferior vena cava. Graft reperfusion is usually associated with a severe reduction in systemic vascular resistance and an increase in venous return, leading to arterial hypotension in about 30% of the patients. This post-reperfusion syndrome is probably the result of the sudden release of cold, acid, and hyperkalemic solution from the graft, but probably other released substances play a role as well. Usually myocardial contractility seems to be preserved, but some patients may develop

0 0

Post a comment