Abstract
The liver is an extremely vascular organ and it is unique in that it has a dual vascular supply, receiving 1500 mL of blood per minute. It is therefore not surprising that bleeding is considered to be a natural accompaniment to liver surgery. Liver transplantation in particular is a very demanding procedure and can in some circumstances result in heavy blood loss. These patients often have two or three system organ failure, not just end-stage liver disease (ESLD) but also associated hepato-renal and hepato-pulmonary syndromes on a background of significant coagulation abnormalities. Severe haemorrhage during the perioperative period is deleterious not only for recovery from surgery but also having an impact on the outcome from primary illness, most notably for early hepatocellular carcinoma (HCC) and colorectal liver metastases. With advances in anaesthetic and surgical techniques it should be possible to perform major liver resections with minimal transfusion requirements.
Good access is a key component to safe bloodless liver surgery. There are important anaesthetic considerations and other surgical manoeuvres that facilitate major liver resections to be performed with minimal transfusion requirements. The major contributors to this are low central venous pressure (CVP) anaesthesia, inflow occlusion of the hepatoduodenal ligament (Pringle's manoeuvre) or total vascular occlusion (IVC control) and intraoperative ultrasound to identify major vessels.
Haemorrhage during liver resection is mainly derived from the hepatic venous system. Hepatic sinusoidal pressure is directly related to CVP. By lowering blood pressure in the IVC, the hepatic venous pressure and hepatic sinusoidal pressure is reduced. Anaesthetic management should aim to keep CVP low without subjecting patients' to the risk of air embolism and systemic tissue hypoperfusion.
Hepatic pedicle clamping is the oldest and commonest method of decreasing bleeding from the liver. It is very effective at reducing bleeding but also causes hepatic ischaemia and portal hypertension when carried out continuously for prolonged periods of time (a maximum of 60–90 minutes is most frequently cited). Intermittent periods of total inflow occlusion (15–20 minutes) followed by a short period (5 minutes) of reperfusion seem to be best. With this technique the total period of warm ischaemia can be nearly doubled to around 120 minutes in both normal and cirrhotic livers. Indeed a prospective study revealed a lower transaminase rise with intermittent occlusion especially in patients with fatty change, as compared to continuous occlusion, with no difference in blood loss. 1
Total hepatic vascular exclusion (TVE) is a technique where the liver is completely isolated from both the systemic and portal circulations. Following complete mobilization, inflow occlusion is achieved with a Pringle's manoeuvre, the infra-hepatic cava is controlled and occluded above the right renal vein. The supra-hepatic cava is clamped proximal to the confluence of the major hepatic veins. This technique is extremely effective in decreasing blood loss and reducing the risk of air embolism. A safe limit seems to be 60 minutes of clamping but reports in the literature vary from 30–120 minutes. 2 It is useful during complex central resections and excision of tumours involving the IVC especially when an interposition graft is necessary for reconstruction. This is a very demanding surgical and anaesthetic exercise and patients should be carefully selected prior to its use.
In situ hypothermic perfusion (HTP) was originally described by Fortner et al. in 1974. 3 The technique has been slightly modified since then. The standard technique requires veno venous bypass with total vascular occlusion and insertion of a small portal cannula proximal to the portal bypass cannula. Usually chilled University of Wisconsin solution is infused to bring the situ liver temperature down to 13oC. An alternative approach to in situ HTP is ex situ, where the liver is removed and cooled on the back table. Similar to preparation of a donor liver on the back table after donor hepatectomy. Pichlmayr was the first to described this technique in 1990. 4 The Hannover group have the largest experience reporting 54 patients having either ex situ cooling and ex vivo resections in 52 patients with an overall mortality of 30%. 5 Some patients even required salvage liver transplantation thereafter. Median survival was 21 months in the group of patients who had CRLM. Ex situ cooling with ex vivo resection is a major undertaking with the potential for considerable morbidity and mortality. Very few patients are suitable for this procedure as most can be dealt with by in situ HTP or TVE. Various other groups have performed ex vivo resections and have reported their results 6,7 but mortality rates seem to be higher compared to those when the liver remains in situ. For those tumours that are very posterior on the IVC and/or involving the hepatic veins, the ante situm technique described by Hannoun can be applied. 8 The liver is disconnected at the supra hepatic IVC and mobilized onto the anterior abdominal wall. This allows tumours to be excised under direct vision rather than continually rotating the liver from right to left or adopting the ‘hanging manoeuvre’.
To obviate the need for the ante situm method Belghiti developed the ‘hanging manoeuvre’. 9 It is most often combined with the anterior approach for large right-sided tumours that involve the diaphragm which makes rotating the liver very difficult. The hanging manoeuvre has undergone several modifications but involves blind dissection for about 4–6 cm between the IVC and liver parenchyma in an avascular plane. However cadaveric studies have confirmed the presence of up to three small veins in this area with the potential for tearing and major haemorrhage if it is not done carefully. Ultrasound control can be useful to identify these veins so they are avoided. 10 A tape or sling is then passed from the hilum to the suprahepatic IVC and then the liver is ‘hung’ facilitating posterior dissection on the IVC and around the hepatic vein confluence.