Original Articles
Neuron-specific enolase increases in plasma during and immediately after extracorporeal circulation

https://doi.org/10.1016/S0003-4975(99)01393-4Get rights and content

Abstract

Background. Minor cerebral complications are common after cardiac surgery. Several biochemical markers for brain injury are under research; one of these is neuron-specific enolase (NSE). The purpose of this study was to investigate the release of this enzyme into the blood during and immediately after extracorporeal circulation and to evaluate the effect of hemolysis on this release.

Methods. Sixteen patients scheduled for elective heart surgery were included in the study. Blood samples for analysis of NSE and free hemoglobin in plasma were drawn before, during, and up to 48 hours after the end of extracorporeal circulation. The release of NSE from erythrocytes and its correlation to the release of free hemoglobin was studied by serial dilution and hemolysis in vitro.

Results. The peri- and postoperative course was uneventful in all patients. Extracorporeal circulation initiated a release of NSE that reached a maximum 6 hours after the end of perfusion. Thereafter, the levels declined with an estimated t1/2 of 30 hours. The concentration of free hemoglobin increased during the perfusion, with maximum levels at the end of perfusion, after which they fell rapidly to normal values. The in vitro study showed a strong linearity between the release of NSE and free hemoglobin after induced hemolysis.

Conclusions. The increased levels of enolase at the end of cardiopulmonary bypass can, to a major part, be explained by the release from hemolysed erythrocytes. The value of NSE as a marker for brain injury in these situations is therefore doubtful.

Section snippets

Material and methods

Sixteen consecutive patients scheduled for elective open heart surgery were studied. Patients with a history of cerebral disease were excluded from the study. Informed consent was obtained and the study protocol was approved by the Ethics committee of the University. Indications for surgery were coronary disease in 14 patients and valvular disease in 2 patients. The male/female ratio was 12:4, and the median age was 63 years (range 30 to 78 years). The anesthetic procedure was similar in all

Results

The peri- and postoperative course was uneventful in all patients included in the study. The median time of ECC was 86 minutes (range 35 to 144 minutes). The serum levels of NSE are shown in Figure 1. The mean time between administration of heparin, when the first blood sample was drawn, and the end of ECC (t = 0) was 120 minutes (range 78 to 134 minutes). The mean perfusion time was 86 minutes (range 36 to 144 minutes) (Table 1). NSE concentrations were within normal levels until the end of

Comment

The results of this study show that there is a release of NSE to plasma during ECC. To a part, this release can be attributed to hemolysis caused by the destruction of erythrocytes and platelets during ECC. Two earlier studies have reported attempts to correlate the release of NSE to the degree of hemolysis in the same sample. According to the first [6], even limited hemolysis can increase NSE levels by 5 to 10 μg/L, but no relationship between the degree of hemolysis and the release of NSE was

Acknowledgements

This study was in part supported by grants from Sangtec AB, Bromma, Sweden.

References (19)

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