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J Thorac Cardiovasc Surg 1995;110:284-286
© 1995 Mosby, Inc.

LETTERS TO THE EDITOR

Liver function after cardiopulmonary bypass in children

Department of Cardiac Surgery
Leeds General Infirmary
Leeds, United Kingdom

To the Editor:

I read with interest the recently published article by Wang and colleagues ¹ concerning hyperbilirubinemia after cardiac surgical procedures, as I have performed a similar but more extensive study in a pediatric population. ²

With the approval of the local hospital Ethics Committee and with informed parental consent, I investigated 36 children, 30 of whom underwent cardiac operations involving the use of cardiopulmonary bypass and six of whom underwent cardiac operations not involving the use of cardiopulmonary bypass; ages were in the range 0.01 to 10.58 years (mean 3.14 years) and 2.75 to 12.95 years (mean 6.21 years), respectively. In the bypass group, 13 patients had atrial septal defects, four had tetralogy of Fallot, four had ventricular septal defects, three had transposition (and underwent arterial switch operations), two had baffle leaks after previous atrial repair of transposition, two had aortic stenosis, one had an atrioventricular septal defect, and one had a cortriatrium. In the nonbypass group, three patients had a coarctation of the aorta, one had a pectus excurvatum, one had a right main pulmonary artery stenosis (repaired with a patch), and one had a double outlet right ventricle combined with transposition (and underwent placement of a Blalock-Taussig shunt).

Measurements of aspartate transaminase (AST), alanine transaminase (ALT), alkaline phosphatase, gamma glutamyl transferase, bilirubin, albumin, cholesterol, and triglycerides were made before the operation and 6, 24, and 48 hours after operation. Phenylalanine clearance and measurement of the galactose elimination capacity, both established and active tests of hepatic function, ^3,4 were carried out 6 hours after operation. Phenylalanine clearance was measured in 23 children, 18 of whom underwent operation involving the use of cardiopulmonary bypass. Galactose clearance was measured in 21 children, 17 of whom underwent operation involving the use of cardiopulmonary bypass.

Results showed a raised AST concentration in five of six patients who did not undergo bypass, with a raised preoperative level in one patient. The bilirubin concentration was also raised in one patient, although it had been abnormal before the operation. Albumin concentrations were reduced in three patients, triglycerides concentrations in two, and cholesterol concentrations in three; the triglycerides and cholesterol concentrations were elevated before the operation in one patient.

In the 30 children undergoing cardiopulmonary bypass, AST level was elevated in 26 patients after and six patients before the operation, bilirubin level was elevated in six patients after and two patients before the operation, and ALT level was elevated in one patient both before and after the operation. Triglyceride concentrations were raised before and after the operation in two patients. Albumin concentrations were low in 29 patients after and in 12 patients before the operation; cholesterol concentrations were low in 21 patients after and 10 patients before the operation.

With the exception of patients in whom individual parameters were abnormal before the operation, abnormalities became apparent within 6 to 24 hours and remained abnormal for 24 to 48 hours.

Five children (28%) undergoing cardiopulmonary bypass had a significantly lower rate of phenylalanine clearance compared with the nonbypass group (mean 1232 ± 3.30 [standard deviation] versus 21.08 ± 3.08 L/hr/m² ; p < 0.002, Mann-Whitney U test) and the remaining bypass patients (mean 21.39 ± 5.82 L/hr/m² ; p < 0.002, Mann-Whitney U test). The galactose elimination half-life was significantly longer in all patients undergoing cardiopulmonary bypass compared with the control group (mean 10.62 ± 3.43 versus 6.03 ± 1.30 minutes; p < 0.005, Mann-Whitney U test).

In this study, the postbypass serum bilirubin concentration was raised in 20% of children, and the AST concentration was raised in 87%. The ALT concentration, however, was rarely raised, suggesting that the increase in AST might not be the result of hepatic injury but could be due to other factors such as concurrent myocardial damage or the stress response because high concentrations were also common in the control group. Increased bilirubin concentrations could be due to hemolysis as suggested by Wang et al., ¹ and, although these early changes (24 to 48 hours) could also be due to hypothermia or anesthetic agents, for example, rather than cardiopulmonary bypass itself, the greater the time interval between the operation and the onset of hepatic impairment, the greater the possibility that abnormalities relate to postoperative rather than intraoperative events.

Changes in bromosulphalein clearance ⁵ after general surgical procedures, together with histologic evidence of acute inflammation from liver biopsy specimens taken at the end of abdominal operations, ⁶ both suggest that cardiopulmonary bypass alone is unlikely to be the only explanation for hepatocellular injury during cardiac operations.

In conclusion, the results presented here show that, although frank liver failure is rarely a feature of corrective congenital heart disease, mild injury is common. Furthermore, the reduction in liver function did not appear to be related to the complexity of the cardiac defect and, by implication, factors which have been suggested to influence the incidence of liver injury in adults, such as preexisting heart failure, longer bypass times, greater degrees of intraoperative hypothermia, and a greater risk of requiring blood transfusion. Children undergoing apparently "straightforward" cardiac operations may therefore have just as much of a risk of hepatic impairment as do children undergoing more complex procedures.

References

1. Wang MJ, Chao A, Huang CH, et al. Hyperbilirubinemia after cardiac operation: incidence, risk factors, and clinical significance. J THORAC CARDIOVASC SURG 1994;108:429-36.[Abstract/Free Full Text]
   
2. Mitchell IM. The nutritional status of children with congenital heart disease and the consequences of cardiac surgery [Thesis]. University of Leeds, 1994.
   
3. Jagenburg R, Olsson R, Regardh C-G, Rodjer S. Kinetics of intravenously administered L-phenylalanine in patients with cirrhosis of the liver. Clin Chim Acta 1977;78:453-63.[Medline]
   
4. Lindskov J. The quantitative liver function as measured by the galactose elimination capacity. I. Diagnostic value and relations to clinical, biochemical and histological findings in patients with steatosis and patients with cirrhosis. Acta Med Scand 1982;212:295-302.[Medline]
   
5. Geller W, Tagnon HJ. Liver dysfunction following abdominal operations: the significance of postoperative hyperbilirubinemia. Arch Int Med 1950;86:908-16.
   
6. Zamcheck N, Chalmers TC, Davidson CS. Pathologic and functional changes in the liver following upper abdominal operations. Am J Med 1949;7:409.
   

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This Article Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Ian M. Mitchell Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Mitchell, I. M. Search for Related Content PubMed PubMed Citation Articles by Mitchell, I. M.