Suppression of interleukin-8 and myeloperoxidase production in the cerebrovascular bed during repeated deep hypothermic circulatory arrest

Introduction

It has been suggested that mild hypothermia during cardiopulmonary bypass (CPB) may attenuate, but not completely suppress, the production of interleukin-8 (IL-8) in the brain [1]. This study examined the effect of repeated deep hypothermic circulatory arrest (DHCA) on production of IL-8 and myeloperoxidase (MPO) in the cerebrovascular bed in patients undergoing pulmonary thromboendarterectomy (PTE).

Methods

After LREC approval and written informed consent, we studied eight patients undergoing PTE. Anaesthetic and surgical technique were strictly standardized [2] and all patients had a jugular bulb catheter inserted after induction. After initiation of CPB, all patients were cooled to below 20°C and underwent at least two periods of DHCA for 20 min. Each DHCA period was separated by a 10-min reperfusion interval. The levels of IL-8 and MPO were measured in paired arterial and jugular samples drawn simultaneously at specific time points, using enzyme-linked immunoassay kits. Juguloarterial (j-a) gradients were then calculated. All data are expressed as median (interquartile range) and were compared with the baseline values using the Wilcoxon signed rank sum test. J-a gradients were compared with zero using one-sample t-test.

Results

The baseline arterial values before CPB [T1] for IL-8 and MPO were 12.9 (11.5-21.4)pg/ml and 4.5 (3.1-6.6)ng/ml, respectively (Fig. 1). For both IL-8 and MPO, arterial levels significantly increased before the first DHCA [T3] to 28.3 (21.6-43.1)pg/ml and 31.2 (26.1-11.7)ng/ml, respectively, and remained elevated until 8 min following the second DHCA [T7]. However, no significant j-a differences for IL-8 and MPO were found throughout this period.

Figure 1

IL-8 and MPO concentration during DHCA. T1, postinduction; T2, CPB started; T3, 2 min preDHCA1; T4, 1 min postDHCA1; T5, 8 min postDHCA1; T6, 1 min postDHCA2; T7, 8 min postDHCA2. ^* P < 0.05 versus baseline.

Conclusions

These data imply that the cerebral activation of inflammatory processes represented as specific IL-8 and MPO production in the cerebrovascular bed are suppressed during repeated DHCA in the present study.