Cerebral inflammatory response during and after cardiac surgery

BACKGROUND AND OBJECTIVE

Neurological dysfunction is a common problem after cardiac surgery with cardiopulmonary bypass (CPB). Cerebral ischaemia associated with the use of CPB may result in a release of neuronal-ischaemic markers and a subsequent cerebral inflammatory response which may additionally release inflammatory cytokines. In order to locate the origin and to quantify the release of neuronal-ischaemic markers and cytokines we investigated arterial-cerebral venous concentration gradients during and after CPB in a clinical setting.

METHODS

In twenty-five patients scheduled for coronary artery bypass grafting surgery we measured the plasma concentration of neuron-specific enolase, S-100beta protein as well as interleukins (IL) IL-6, IL-8 and IL-10 from arterial and cerebral venous blood samples prior to surgery (baseline), during hypothermic CPB at 32 degrees C, after termination of bypass, as well as 2, 4 and 6 h after admission to the intensive care unit.

RESULTS

Arterial-cerebral venous concentration gradients of neuron-specific enolase, S-100beta, IL-6, IL-8 and IL-10 were neither detectable during nor after CPB. Compared to the baseline period, S-100beta and neuron-specific enolase significantly increased during hypothermic CPB. After termination of CPB, neuronal-ischaemic markers as well as cytokines were increased and remained elevated during the investigated time course without reaching baseline values.

CONCLUSIONS

Although we found an overall increase in plasma concentrations of neuronal-ischaemic markers, IL-6, IL-8 and IL-10 during and after CPB, arterial-cerebral venous gradients were not detectable for any of these parameters. Our results suggest that the increase of investigated parameters associated with the use of CPB are not primarily caused by a cerebral inflammatory response but rather reflect a release from other sources in the systemic circulation.

Changes of jugular venous blood temperature associated with measurements of cerebral blood flow using the transcerebral double-indicator dilution technique

BACKGROUND AND OBJECTIVE

The transcerebral double-indicator dilution technique is a recently developed method to measure global cerebral blood flow at bedside. It is based on bolus injection of ice-cold indocyanine green dye and simultaneous recording of resulting thermo- and dye-dilution curves in the aorta and the jugular bulb. However, with this method 40 mL of ice-cold solution is administered as a bolus. Therefore, this prospective clinical study was performed to elucidate the effects of repeated administration of indicator on absolute blood temperature and on cerebral blood flow and metabolism.

METHODS

The investigation was performed in nine male patients scheduled for elective coronary artery bypass grafting. Absolute blood temperature was measured in the jugular bulb and in the aorta before and after repeated measurements using the transcerebral double-indicator dilution technique.

RESULTS

During the investigated time course, the blood temperature in the jugular bulb, compared to the aorta, was significantly higher with a mean difference of 0.21 degrees C. The administration of an ice-cold bolus reduced the mean blood temperature by 0.06 degrees C in the jugular bulb as well as in the aorta. After the transcerebral double-indicator dilution measurements a temperature recovery to baseline conditions was not observed during the investigated time period. Cerebral blood flow and cerebral metabolism did not change during the investigated time period.

CONCLUSIONS

Repeated measurements with the transcerebral double-indicator dilution technique do not affect absolute jugular bulb blood temperatures negatively. Global cerebral blood flow and metabolism measurements remain unaltered. However, accuracy and resolution of this technique is not high enough to detect the effect of minor changes of physiological variables.