Erik Ståhl

Cerebral complications after cardiac surgery assessed by S-100 and NSE levels in blood

OBJECTIVEnAssessment of the value of blood analysis of the astroglia protein, S-100, and neuron-specific enolase for the detection of nervous system dysfunction after cardiac surgery.nnnDESIGNnProspective study. Neurologists blinded from laboratory results.nnnSETTINGnUniversity hospital.nnnPARTICIPANTSn38 patients undergoing cardiac surgery.nnnINTERVENTIONSn21 patients were operated for coronary artery disease; seven patients with replacement of the aortic valve of whom 2 also had coronary bypass. Four patients had mitral valve replacement of whom 2 also had coronary bypass. One patient had both aortic and mitral valve replacement and coronary bypass. Two patients were operated on because of aortic arch aneurysm.nnnMEASUREMENTS AND MAIN RESULTSnNeurologic examinations were performed before and after surgery. General behavior of the patients was repeatedly assessed. Blood samples for analysis were collected before operation and on the second day after surgery. In 8/38 patients (21%), a neurologic complication, one of which was lethal, occurred. In 27 patients (71%), the neurologic outcome was uncomplicated, and in 3 (8%), it could not be classified. Elevated S-100 and neuron-specific enolase levels were found in 7/8 patients who endured a neurologic complication and in 4/27 free of complication. (Fishers exact test p < 0.001). Positive and negative predictive values were 64% and 96%, respectively. S-100 (range 0.5 to 1.3 micrograms/L) and neuron-specific enolase levels (range 8.6 to 16.7 micrograms/L) were lower for the 7 patients with nonlethal complications than for the patient who died (9.5 micrograms/L and 31.3 micrograms/L, respectively).nnnCONCLUSIONSnS-100 and neuron-specific enolase levels after cardiac surgery are associated with neurologic complications. The results have implications on patient-related treatment and prognosis as well as for the development of safer perfusion techniques.

The Appearance of S-100 Protein in Serum During and Immediately After Cardiopulmonary Bypass Surgery: A Possible Marker for Cerebral Injury

OBJECTIVEnTo investigate the appearance and elimination of brain-specific S-100 protein in serum during and immediately after cardiopulmonary bypass.nnnDESIGNnProspective study.nnnPARTICIPANTSnTwenty-nine patients undergoing elective cardiac surgery.nnnINTERVENTIONSnTwenty-seven patients were operated on for coronary artery disease; two patients had valve replacement. Serial measurements of S-100 in arterial blood during and up to 48 hours after cardiopulmonary bypass were made.nnnMEASUREMENTS AND MAIN RESULTSnThe perioperative and postoperative course was uneventful in 25 patients, with no clinical signs of neurologic complications. S-100 was not detected before extracorporeal circulation was started. Detectable concentrations (detection limit, 0.2 microgram/L) appeared in serum after 10 minutes of perfusion and reached maximum levels, 2.43 +/- 0.3 micrograms/L, at the end of bypass. The levels then declined with elimination t1/2 of 2.2 hours. Only two patients had detectable concentrations of S-100 48 hours after the end of bypass. In four patients who developed clinical signs of cerebral injury, levels of S-100 were significantly higher at the end of bypass and 24 hours after the end of bypass.nnnCONCLUSIONSnCardiopulmonary bypass initiates a release of brain-specific S-100 to the systemic circulation. The release and elimination of S-100 seem to follow a reproducible pattern in patients with no signs of cerebral injury. In patients who developed cerebral injury, the concentrations of S-100 in blood were increased, thus suggesting that S-100 may be a usable marker for cerebral injury after extracorporeal circulation.

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

BACKGROUNDnMinor 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.nnnMETHODSnSixteen 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.nnnRESULTSnThe 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.nnnCONCLUSIONSnThe 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.

Cardiopulmonary perfusion and cerebral blood flow in bilateral carotid artery disease

The fear of cerebral complications after cardiopulmonary bypass in patients with heart disease and severe carotid artery disease has led many authors to suggest combined approaches in these patients. The pathogenetic mechanism for stroke is based partly on the stenotic narrowing of the carotid artery. A diameter reduction of 75% is frequently considered hemodynamically significant and indicative of an increased risk for neurological morbidity. We studied the cerebral blood flow in 7 patients undergoing coronary artery bypass grafting who also had severe bilateral carotid disease. The results were compared with the results in 17 patients without carotid disease who had bypass grafting. The cerebral blood flow was measured by xenon 133 washout technique before, during, and after cardiopulmonary bypass with moderate hypothermia. Acid-base regulation was according to the alpha-stat theory, and blood pressure was kept greater than 50 mm Hg. The cerebral blood flow levels (mL.100g-1.min-1) before, during, and after cardiopulmonary bypass in the study group (30 +/- 11, 31 +/- 8, 47 +/- 20) (mean +/- standard deviation) were almost identical to those in the control group (30 +/- 11, 28 +/- 8, 47 +/- 12). The cerebral blood flow levels for the left and right hemispheres in the group with carotid disease were comparable and within normal ranges. In 2 patients, slight differences were noted between hemispheres, and this finding may indicate an increased risk for ischemia. These patients, however, did not show any signs of postoperative deficit. The flow limitations of critical carotid stenoses do not seem to imply a risk for cerebral hypoperfusion if cardiopulmonary perfusion is performed in a controlled manner.(ABSTRACT TRUNCATED AT 250 WORDS)

Cerebral vasoreactivity to carbon dioxide during cardiopulmonary perfusion at normothermia and hypothermia

With the pH-stat acid-base regulation strategy during hypothermic cardiopulmonary bypass (CPB), carbon dioxide (CO2) is generally administered to maintain the partial pressure of arterial CO2 at a higher level than with the alpha-stat method. With preserved CO2 vasoreactivity during CPB, this induction of respiratory acidosis can lead to a much higher cerebral blood flow level than is motivated metabolically. To evaluate CO2 vasoreactivity, cerebral blood flow was measured using a xenon 133 washout technique before, during, and after CPB at different CO2 levels in patients who were undergoing coronary artery bypass grafting with perfusion at either hypothermia or normothermia. The overall CO2 reactivity was 1.2 mL/100 g/min/mm Hg. There was no difference between the groups. The CO2 reactivity was not affected by temperature or CPB. The induced hemodilution resulted in higher cerebral blood flow levels during CPB, although this was counteracted by the temperature-dependent decrease in the hypothermia group. After CPB, a transient increase in cerebral blood flow was noted in the hypothermia group, the reason for which remains unclear. The study shows that manipulation of the CO2 level at different temperatures results in similar changes in cerebral blood flow irrespective of the estimated metabolic demand. This finding further elucidates the question of whether alpha-stat or pH-stat is the most physiological way to regulate the acid-base balance during hypothermic CPB.

Hemoconcentration by ultrafiltration during open-heart surgery.

Ultrafiltration was used during extracorporeal circulation (ECC) with heart-lung machine in 17 critically ill cardiac patients. In ultrafiltration (hemofiltration), water and small molecules (e.g. urea, creatinine and electrolytes), are separated from the blood by hydrostatic pressure generated on the blood side of a semipermeable membrane. The patients had severe water overload for three reasons, viz. congestive heart failure (10), renal failure (6) or iatrogenic extreme hemodilution (1). On average 2090 (800-5700) ml water was filtered off, increasing the hematocrit from 25 to 33%. Three indications for ultrafiltration during ECC and two modes of such treatment are exemplified in three case reports. No negative effect of the treatment was observed. Ultrafiltration during ECC thus may help to improve the postoperative course in patients with severe water overload due to congestive heart failure, renal failure or iatrogenic extreme hemodilution.

Cerebral blood flow and autoregulation during hypothermic cardiopulmonary bypass

Mean hemispheric cerebral blood flow (CBF) was studied following intravenous or intraarterial administration of xenon-133, in 10 men admitted for coronary artery bypass grafting. Repeated CBF measurements were performed to evaluate autoregulation before, during, and after cardiopulmonary bypass (CPB). During CPB mean CBF remained unchanged compared with the pre-CPB level, without evidence of cerebral hyperemia or impairment of autoregulation. A marked increase in CBF occurred after CPB and was followed by a time-dependent reduction toward the pre-CPB level. The data support the alpha-stat regulation theory but cannot explain the cerebral vasodilation observed after CPB.

Late cardiac tamponade following open-heart surgery: Diagnosis and Treatment

Late cardiac tamponade is a rare but serious complication following open-heart surgery. It occurred in 9 (0.8%) of 1 094 consecutive patients 6 to 13 (median 8) days after operation. Six patients had undergone valve replacement and three coronary bypass surgery. All were on anticoagulant medication postoperatively (median TT index 7%). Early symptoms of cardiac tamponade were nausea and general malaise (present in all 9 cases), whereas classical signs of tamponade such as arterial hypotension and distended neck veins appeared late. The cardiac silhouette was radiographically enlarged in all cases, but this finding was seldom diagnostic. Computed tomography gave the surest diagnosis and permitted quantitative assessment of the fluid in the pericardium. Pericardial needle puncture was effective in temporarily relieving the tamponade, but insertion of a tube by the subxiphoid approach gave definitive drainage.

Acute immobilization of the disc in the Björk-Shiley aortic tilting disc valve prosthesis. A report of 3 cases.

Acute non-thrombotic immobilization of the disc in the Björk-Shiley aortic valve prosthesis occurred as a result of extrinsic factors in three patients. Unravelled suture or long suture ends were the cause in two cases. Tissue detached from the aortic intima migrated into the valve and locked the disc in closed position in one case. The mechanisms of extrinsic disc immobilization and its prevention and treatment are discussed.

Multicentre Investigation of Myocardial Protection with Cold Cardioplegia: A Computerized Study of 144 Patients Undergoing Isolated Aortic Valve Replacement

In order to analyze factors of importance for the efficiency of myocardial protection during open-heart surgery, a study was made of 144 patients undergoing isolated aortic valve replacement with various cardioplegic techniques. The cardioplegia was of Bretschneider type in 54 cases, St Thomas in 31 and Ringer-potassium type in 11 cases. Single or multi-dose blood cardioplegia was used in 11 cases and continuous blood cardioplegia in 30 cases. Local cardiac hypothermia was additionally employed in all patients. The efficiency of myocardial protection was assessed mainly from the incidence of postoperative conduction disturbances, myocardial enzyme release and need for inotropic support. All patients survived the operation. In 20% surgery was followed by transient or persistent disturbance of conduction, in 9% by abnormally increased CK-MB release and in 5% by requirement for inotropic support. Preoperative risk factors such as high age or severe left ventricular (LV) hypertrophy or dysfunction had little influence on the results. Patients in whom aortic stenosis (AS) was dominant in the complex with aortic insufficiency (AS + AI) showed 20-hour postoperative CK-MB enzyme activity twice as high as those with pure aortic insufficiency. The most important factors in myocardial protection were the duration of aortic occlusion and the myocardial temperature during cardioplegia. When the aortic occlusion lasted more than 80 min there was a 32% incidence of conduction disturbances and 20-hour CK-MB activity thrice as high as after shorter occlusion. Patients with mean myocardial temperature below 18 degrees C during cardioplegia invariably had low enzyme activities, which indicated good myocardial protection. The best overall results were obtained in patients operated on during hypothermia at 25-27 degrees C, with single or multi-dose blood cardioplegia and with efficient local cooling of the heart.