Pierre-Yves Lequeux

Continuous mixed venous and central venous oxygen saturation in cardiac surgery with cardiopulmonary bypass.

Background and objective Replacing mixed venous oxygen saturation (SvO2) monitoring by central venous oxygen saturation (ScvO2) monitoring in order to avoid the use of a pulmonary artery catheter and its related complications is still controversial in the setting of cardiac surgery. The influence of surgery, cardiopulmonary bypass and anaesthesia drugs on the relationship between SvO2 and ScvO2 has never been studied. Methods Fifteen patients scheduled for cardiac surgery with cardiopulmonary bypass were included in the study. SvO2 (from the pulmonary artery) and ScvO2 (from the superior vena cava) were continuously measured with fibre-optic catheters from induction of anaesthesia to 24 h postoperatively. Results A total of 9267 pairs of measurements were recorded. Mean bias between SvO2 and ScvO2 was 4.4% with limits of agreement of −13.6 and +22.5%, respectively. Trends of SvO2 and ScvO2 values followed very different patterns for some patients. Surgery, cardiopulmonary bypass and anaesthesia drugs did not influence the relationship between the two methods. Conclusion Because of the large interindividual variability in the difference between SvO2 and ScvO2, the measure of ScvO2 should not replace the measure of SvO2 with a pulmonary artery catheter for the management of patients undergoing cardiac surgery with cardiopulmonary bypass.

Absence of explicit and implicit memory in unconscious patients using a TCI of propofol

Background:   Episodes of implicit memory have been described during propofol anaesthesia. It remains unclear whether implicit memory is caused by short periods of awareness or occurs in an unconscious subject.

Absence of implicit and explicit memory during propofol/remifentanil anaesthesia

Background and objective: High doses of opioid associated with low doses of hypnotic is a popular anaesthetic technique since the use of remifentanil has become widespread. This type of anaesthesia could result in a higher incidence of implicit memory. Methods: Ten patients were anaesthetised with a target‐controlled infusion of remifentanil (target concentration of 8 ng mL−1) combined with a target‐controlled infusion of propofol with progressive stepwise increases until loss of consciousness was reached. A tape containing 20 words was then played to the patients. Bispectral index (BIS, Aspect Medical Systems, Newton, MA, USA) was continuously monitored during the whole study period. Implicit and explicit memories were tested between 2 and 4 h after recovery. Results: Loss of consciousness was obtained with a mean calculated propofol plasma concentration of 1.3 ± 0.4 μg mL−1. At this low hypnotic concentration no implicit or explicit memory was found in the three postoperative memory tests. Median (range) BIS value during word presentation was 93 (80‐98). Conclusions: In our group of young American Society of Anesthesiologists (ASA) I/II patients, no explicit or implicit memory was found when the calculated concentration of propofol combined with a high concentration of remifentanil was maintained at the level associated with loss of consciousness with high BIS values.

Does anesthetic regimen influence implicit memory during general anesthesia

BACKGROUND:Implicit learning of intraoperative auditory stimuli during general anesthesia is very difficult to quantify but may require the presence of noxious stimulation. We hypothesized that an anesthetic regimen with a low dose of opioid would enhance implicit memory, while a regimen with a high dose of opioid would not. METHODS:One hundred-twenty patients were randomized into 3 groups. All patients were anesthetized with a target-controlled infusion of propofol and remifentanil, targeting a Bispectral Index (BIS) value of 50. The remifentanil effect-site concentration (in ng/mL) was always double that of propofol (in &mgr;g/mL) in the first group and half of that in the second group. Patients in these 2 groups were played a list of 20 words via headphones during surgery. The third group served as control for memory tests and was not played any word during anesthesia. BIS was recorded during word presentation. RESULTS:No statistical difference was found among the 3 groups regarding 3 different memory tests although 67.5% [50.7%; 80.9%] of the patients of the high-opioid group and 72.5% [55.9%; 84.9%] of the low-opioid group had at least 1 episode of BIS >60. CONCLUSIONS:We could not demonstrate the presence of implicit or explicit memorization under propofol-remifentanil anesthesia either with a low- or a high-dose opioid anesthetic regimen.

Effect of intraoperative depth of anesthesia on postoperative pain and analgesic requirement: A possible misidentified role of propofol

Use of an MAC 3 adult blade in young children in these situations is required to go beyond the swelling up to the base of the tongue into the vallecula and visualize the epiglottis and then the glottis. In close consultation with the surgical colleague, the feasibility of aspiration of the cystic lesions should be considered, if does not interfere with the plane of dissection. For safe airway management in selective cystic lesions, particularly in the absence of availability of difficult intubation aids, the cyst can be aspirated before tracheal intubation.

The influence of the dose on the time to peak effect of propofol: preliminary results: A-528

with a perfusion pump according to manual infusion scheme proposed by Roberts1. Patients had BIS and SBP recorded at all times (including baseline values). Four blood samples (in order to measure blood concentration, Cs) were collected from each subject, at predose, at the end point and at fixed intervals of 15 and 30 min. Reduction in SBP, [(SBP-80)/(SBPbaseline-80)]*100, was used as a measure of P effect and related to Cs using a semicompartmental model in order to obtain ke0. Ce (effect site concentration) was then estimated and a pharmacodynamic (PD) model was used to describe the data (WinNonLin Professional, Pharsight Corp.). Results: 21 (10 M and 11 W) out of the total 58 patients did not present drop in SBP during the 30 min of data record although BIS values were at most 60. These patients were excluded from analysis. The remaining (37 patients) showed a significant hysteresis (lag-time between Cs and SBP). The first order rate constant ke0, was 0.67 min 1 both in M and in W. Estimated Ce at induction was less in W although no statitical differences were found due to large variability (4.50 vs 6.12 mcg/mL W and M respectively). A sigmoid Emax model best described the data (Ce vs effect). PD parameters (ECe50 and ) did not show statistical gender dependence. Conclusions: No PD differences were found for P routine protocol anesthesia between M and W for the SBP endpoint. SBP is possibly an inadequate surrogate of anesthesic effect during the first 30 min of surgery. References: 1 Roberts FL. Anaesthesia. 1988; 43:14–7. 2 Kazama T. Anesthesiology. 1999; 90:1517–27. 3 Hoymork SC. Br J Anaesthesia. 2005; 95(5):627–33.