Relevance of Postoperative Peak Transaminase After Elective Hepatectomy
In a recent issue of Annals of Surgery, Boleslawski et al1 published an article evaluating the peak serum transaminases after elective liver surgery. Despite many improvements in preoperative imaging, patient selection, surgical techniques, and perioperative care in recent years, hepatic resection is still associated with a high morbidity and mortality, ranging from 20% to 40% and of 4.4%, respectively.2–4 So far, reliable criteria to predict morbidity and mortality after liver resection remain poorly defined. In this regard, peak postoperative serum transaminase (PST) is thought to be strictly correlated with the ischemic hepatocellular damage and corresponding postoperative outcome. Therefore, measurement of aspartate-amino-transferase and alanine-amino-transferase are the most frequently used parameters in liver surgery related trials. As correctly mentioned by the authors, it should be noted that there is no clear evidence in the literature about PST and its prediction validity.
Therefore, the current study had been initiated to determine whether inflow occlusion during hepatectomy is correlated with PST and, moreover, whether PST is predictive of postoperative morbidity and mortality after liver resection and length of hospital stay. In summary, the authors demonstrate that PST did not correlate with ischemia time and that PST was not independently associated with either morbidity or severe morbidity. In contrast, PST was influenced by duration of surgery, number of red blood cells transfused, and concomitant in situ ablation therapy. We consider these findings of great importance. Consequently, PST levels after liver surgery have to be interpreted carefully, and furthermore, the clinical relevance of numerous studies using PST as a primary endpoint has to be reconsidered critically. But yet we would like to address a few important issues.
A great advantage of the current study is certainly its character of a multicenter, prospectively designed study with a formidable study population of 651 patients within less than a year. These patients have undergone liver resection of different extent (nonanatomical, bisegmentectomy, right/left hepatectomy, and right/left trisectionectomy). Regarding the extent of liver resection, it would have been interesting on the one hand to measure the resected and the remaining liver volume and on the other hand to analyze the correlation between the exact extent of liver resection and remaining liver volume with PST instead of simply categorizing all resections into major (≥3 segments) and minor (<3 hepatectomies). In our opinion, distinction between the removed liver segments is mandatory as a resection of segment VI/VII is associated with an increased risk of morbidity compared with a segment II/III resection, for example. Another possibility, proposed by Shubert et al,5 is to define partial and left hepatectomy as “minor hepatectomy” and right hepatectomy and trisectionectomy as “major hepatectomy.” Were there any crucial ischemic areas left in the remaining liver after resection, as it is known that particularly after nonanatomical resections this is a known risk? Moreover, additional information about the performed dissection technique, whether an ultrasonic dissector, WaterJet dissector or stapling devices were used, would have been valuable. Although the authors address inflow variations, outflow variations are of equal importance for the liver function6 but unfortunately an analysis of the influence of central venous pressure on PST for instance is lacking. Another parameter which is thought to influence liver function after resective procedures is the body temperature of the patient.7
Another issue is the concomitant in situ ablation therapy employed, which was performed in 52 patients and which was identified to influence PST. The authors do not provide information regarding the technique of ablation therapy, whether cryotherapy, radiofrequency ablation (RFA), microwave ablation, thermal ablation, laser ablation, or high-intensity focused ultrasound ablation were used.