Anneliese Moerman

Clinical usefulness of the bispectral index for titrating propofol target effect-site concentration

The bispectral index, a new processed electroencephalographic parameter which may give information on depth of anaesthesia, was used in 58 patients undergoing outpatient gynaecological surgery in order to study if the addition of bispectral index monitoring to standard clinical monitoring could improve the titration of target propofol concentration when using effect‐site target‐controlled propofol infusion for sedation. In Group 1 (n = 30), the bispectral index was recorded but the anaesthetist was unaware of the readings and therefore only classical signs of depth of anaesthesia were used to guide the anaesthetist in controlling the effect‐site concentration. In Group 2 (n = 28), bispectral index readings were available to the anaesthetist and effect‐site concentration was adjusted to ensure that bispectral index was maintained between 40 and 60. Similar propofol induction and maintenance doses, blood and effect‐site concentrations and mean bispectral index were found in the two groups. A greater percentage of bispectral index readings lying outside the target range (i.e. < 40 or > 60) and more movement at incision and during maintenance were found in Group 1. There was a trend towards more implicit awareness in patients in Group 1. Bispectral index was found to be useful for measuring depth of sedation when using propofol target‐controlled infusion. Propofol dosage could not be decreased but a more consistent level of sedation could be maintained due to a more satisfactory titration of target effect‐site concentration.

Relevance of epidurography and epidural adhesiolysis in chronic failed back surgery patients

ObjectivePain treatment in the chronic failed back surgery patient remains problematic. Defining the pathogenesis of the pain could be helpful in treatment. The assumption that epidural fibrosis and adhesions might play an important role in the origin of the pain is verified. DesignWe investigated 34 patients in whom peridural fibrosis was suspected. An epidural catheter was inserted via the sacral hiatus. Injections of contrast dye, local anesthetic, corticosteroid, and hypertonic NaCl 10% were carried out daily for 3 days. Spread of the contrast dye in the epidural space was evaluated after 10 and 20 ml injection volume. SettingSubjects were patients in a pain clinic of a university hospital in Belgium. PatientsChronic pain patients with failed back surgery syndrome were examined. Nerve pathology was demonstrated and epidural fibrosis suspected or proved with magnetic resonance imaging (MRI) examination. Outcome MeasuresImprovement in the contrast filling defects of the epidural space were noticed during treatment and correlated with pain improvement. ResultsFilling defects were noted in 30 of the 34 patients investigated. After the third day an objective improvement of contrast spread was documented in 14 patients. In seven patients improvement in pain occurred for only a very limited period (1 month). Statistical analysis (chi square analysis) could not demonstrate that improvement of contrast spread was correlated with better pain behavior. In 16 patients no improvement in contrast spread could be visualized. Pain improvement occurred in only four patients and for a limited period of 1 month. Long-term results are even worse. ConclusionEpidurography might confirm epidural filling defects for contrast dye in the patients with epidural fibrosis. A better contrast dye spread, assuming scar lysis, does not guarantee a sustained pain relief. A more direct visualization of the resulting functional changes after adhesiolysis as with epiduroscopy might be useful.

Comparative study of limited intentional normovolaemic haemodilution in patients with left main coronary artery stenosis

Intentional normovolaemic haemodilution is a blood saving technique which can be performed when major blood loss is expected. Severe coronary artery disease and particularly left main stenosis are considered a contraindication for intentional normovolaemic haemodilution. The effects and complications of limited intentional normovolaemic haemodilution in patients with left main coronary artery stenosis scheduled for coronary artery bypass grafting were evaluated. Patients were randomly allocated to two groups: group A (n = 15) underwent limited intentional normovolaemic haemodilution to a haematocrit of 34%; group B(n = 15), no intentional normovolaemic haemodilution was performed. In both groups succinyl‐linked gelatin was used to maintain normovolaemia. Haemodynamic parameters were kept as constant as possible. In group A, a mean (SD) volume of 785 (250) ml of blood was withdrawn [range 500–1200 ml]. ST segment changes occurred on the ECG in three patients in each group. There were no statistically significant differences for frequency, maximum deflection and duration of ST‐segment changes. Limited intentional normovolaemic haemodilution can be performed safely in patients with left main coronary artery stenosis. In this study it was not associated with increased frequency, severity or duration of ST‐segment changes, or with arrhythmias or haemodynamic instability.

Limited intentional normovolemic hemodilution: ST-segment changes and use of homologous blood products in patients with left main coronary artery stenosis

OBJECTIVE To assess and compare the effects of limited intentional normovolemic hemodilution (LINH) on ST-segment changes and to evaluate the need for homologous blood products. DESIGN Prospective, randomized study. SETTING University hospital. PARTICIPANTS Seventy-one patients with left main stenosis scheduled for semi-urgent coronary artery bypass grafting. INTERVENTIONS Patients in group A (n = 39) underwent LINH during the prebypass period until a hematocrit of 34% was obtained. Simultaneously, succinyl-linked gelatin was infused. In group B (n = 32), no hemodilution was performed. Mean arterial pressure and central venous pressure were kept as constant as possible. During the postbypass period, autologous blood was retransfused. The need for homologous blood products was noted intraoperatively and postoperatively. MEASUREMENTS AND MAIN RESULTS ST-segment analysis of lead II and chest lead was continuously performed in all patients. An ST-segment change was defined as a decrease from baseline of 1.0 mm (-0.1 mV). The appearance and degree of ST-segment depression were comparable in both groups (group A: 7 patients -0.1 mV, 1 patient -0.2 mV; group B: 5 patients -0.1 mV; 3 patients -0.2 mV). In group A, ST-segment depression occurred during and after the blood exchange. However, the mean duration of the ST-segment depression (group A: 33 +/- 18 minutes; group B: 20 +/- 10 minutes) was comparable between groups. In group A, a mean of 750 mL +/- 245 mL of blood was obtained. Total blood loss was significantly higher in group B (p < 0.052); 25 patients in group A (64%) and 12 patients in group B (38%) did not require homologous blood products (p < 0.03). Intraoperatively, only the need for packed red cells was greater in group B (p < 0.04). Postoperatively, the use of homologous blood products is higher than intraoperatively (p < 0.02). CONCLUSIONS LINH performed in patients with left main stenosis, scheduled for semi-urgent coronary bypass, is not associated with increases in frequency, degree, or duration of ST-segment changes. This procedure allowed a reduction in the number of patients who received homologous blood products.

Relation between mixed venous oxygen saturation and cerebral oxygen saturation measured by absolute and relative near-infrared spectroscopy during off-pump coronary artery bypass grafting

BACKGROUND We hypothesized that previously reported contradictory results regarding the equivalence of mixed venous (Smv(O(2))) and cerebral (rS(c)O(2)) oxygen saturation might be related to time delay issues and to measurement technology. In order to explore these two factors, we designed a prospective clinical study comparing with relative (INVOS(®)) and absolute (Foresight(®)) rS(c)O(2) measurements. METHODS Forty-two consenting patients undergoing elective off-pump coronary artery bypass grafting were included. Two INVOS and two Foresight sensors continuously registered rS(c)O(2). Smv(O(2)) was measured continuously via a pulmonary artery catheter. Data were assessed by within- and between-group comparisons and correlation analysis. RESULTS A similar time delay of 19 (4) and 18 (4) s was found for compared with rS(c)O(2) measurements by Foresight and INVOS, respectively, during haemodynamic changes. After adjusting for this time delay, the correlation between Smv(O(2)) and rS(c)O(2) increased from r=0.25 to 0.75 (P<0.001) for Foresight, and from r=0.28 to 0.73 (P<0.001) for INVOS. Comparison of Foresight and INVOS revealed significant differences in absolute rS(c)O(2) values (range 58-89% for Foresight and 28-95% for INVOS). Changes in rS(c)O(2) in response to acute haemodynamic alterations were significantly more pronounced with INVOS compared with Foresight (P<0.001). CONCLUSIONS Considering the important time delay with Smv(O(2)), rS(c)O(2) seems to reflect more appropriately acute haemodynamic alterations. This might suggest its use as a valid alternative to invasive monitoring of tissue oxygen saturation. Relative and absolute rS(c)O(2) measurements demonstrated significant differences in measured rS(c)O(2) values and in the magnitude of rS(c)O(2) changes during haemodynamic alterations.

Remifentanil infusion for cardiac catheterization in children with congenital heart disease

Background:  Cardiac catheterization of children with congenital heart disease is increasingly being performed under general anesthesia. Haemodynamic stability during anesthesia and fast and adequate recovery after the procedure is crucial in these patients. We performed a pilot study to evaluate hemodynamic stability when using remifentanil for anesthesia during cardiac catheterization. We also evaluated extubation times and recovery characteristics.

Influence of anaesthesia on defibrillation threshold.

Internal cardioverter–defibrillator implantation can be performed under local or general anaesthesia. Whether the technique of general anaesthesia influences the defibrillation threshold remains a matter of debate. We therefore compared, in a prospective, randomised clinical study, the effect of intravenous anaesthesia using propofol with inhalational anaesthesia using isoflurane on the defibrillation threshold in 68 patients scheduled for transvenous single‐lead internal cardioverter–defibrillator implantation. Defibrillation threshold was measured at implantation and at device testing 1 week and 1 month after implantation. Patients acted as their own controls. Neither the anaesthetic technique nor the duration of anaesthesia was associated with significant changes in the defibrillation threshold. We conclude that in this group of high‐risk patients, both types of anaesthesia are acceptable techniques for internal cardioverter–defibrillator implantation and testing.

Ambulatory electrical external cardioversion with propofol or etomidate

STUDY OBJECTIVE To compare, in pairwise fashion, the effects of propofol and etomidate during ambulatory cardioversion and early recovery. DESIGN Clinical, prospective, randomized, blinded, monocenter, pairwise, comparative study SETTING OR and recovery area of the electrophysiological department, University Hospital Ghent, Belgium. PATIENTS 34 patients with atrial arrhythmia who were scheduled for repetitive electrical cardioversion, of whom 25 patients completed the study. INTERVENTIONS Nonpremedicated patients received during the first cardioversion either propofol (1 mg/kg) or etomidate (0.2 mg/kg) until loss of consciousness, followed by electrical external cardioversion. If after restoration of sinus rhythm for at least 1 day, atrial arrhythmia reoccurred, a second session was performed a week later, using the other induction drug. MEASUREMENTS Systolic and diastolic blood pressure values taken before drug administration, at loss of consciousness, 60 seconds after cardioversion, and awake; the number of shocks, the total amount of energy, the number of patients in which we failed to restore sinus rhythm, the time before opening eyes, answering simple questions and be able to sit, were all noted. Aldrete scores and the Steward postanesthetic recovery scores were noted every minute until 10 minutes after the external cardioversion. Recovery tests were performed and evaluated 5, 10, 15, and 20 minutes after energy delivery. MAIN RESULTS Number of shocks, amount of energy, and blood pressure values were comparable in both groups. Recovery times and Aldrete and Steward postanesthetic recovery scores showed a faster awakening in patients who were induced with propofol. Overall performance of the psychomotor test was better in the propofol group, and most pronounced at 10 and 15 minutes. CONCLUSIONS Etomidate and propofol are both useful during ambulatory external electrical cardioversion. The described doses maintain stable hemodynamic conditions in nonpremedicated patients. Recovery scores and psychomotor test indicate a faster recovery in the propofol group. However, no intergroup differences were noted at 20 minutes after the cardioversion. A safe discharge of all patients from the critical care unit or postanesthesia care unit to the ward can be considered after 30 minutes.

Myocardial injury and protection related to cardiopulmonary bypass

During cardiac surgery with cardiopulmonary bypass, the heart is isolated from the circulation. This inevitably induces myocardial ischemia. In addition to this ischemic insult, an additional hit will occur upon reperfusion, which may worsen the extent of tissue damage and organ dysfunction. Over the years, several strategies have been developed that aim to attenuate and/or modulate the extent of this ischemia-reperfusion injury related to the episode of cardiopulmonary bypass. This article reviews the pathophysiology of myocardial injury related to cardiopulmonary bypass and summarizes potential therapeutic strategies that may modulate the extent of this myocardial injury.

Cerebral oximetry: the standard monitor of the future?

Purpose of review There is an increasing interest in the application of near-infrared spectroscopy (NIRS) as a monitoring tool in noncardiac surgery. This review summarizes the latest developments and current evidence for the use of NIRS in the noncardiac intraoperative setting. Recent findings Unanticipated intraoperative physiological disturbances and a substantial interpatient variability in the limits of cerebral autoregulation, pose our patients at risk for adverse cerebral outcome, if the brain is not monitored specifically. In addition to a means to monitor the brain, NIRS has been shown to allow an estimate of overall organ oxygenation. Preliminary data suggest a relationship between cerebral desaturation and both neurologic and major organ morbidity. Summary NIRS offers noninvasive monitoring of cerebral and overall organ oxygenation in a wide range of clinical scenarios. There is an increasing evidence that the optimized cerebral oxygenation is associated with improved outcomes in both neurologic and major organ morbidity in a variety of surgical settings.