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Biomedical subjects

M C Dubois

Publications and source records attributed to M C Dubois.

17 recordsLinked to original sources
PubMed1999

Changes in electroencephalogram and autonomic cardiovascular activity during induction of anesthesia with sevoflurane compared with halothane in children.

BACKGROUND: This study was design to assess clinical agitation, electroencephalogram (EEG) and autonomic cardiovascular activity changes in children during induction of anesthesia with sevoflurane compared with halothane using noninvasive recording of EEG, heart rate, and finger blood pressure. METHODS: Children aged 2-12 yr premedicated with midazolam were randomly assigned to one of three induction techniques: 7% sevoflurane in 100% O2 (group SevoRAPID); 2%, 4%, 6%, and 7% sevoflurane in 100% O2 (group SevoINCR); or 1%, 2%, 3%, and 3.5% halothane in 50% N2O-50% O2 (group HaloN2O). An additional group of children who received 7% sevoflurane in 50% N2O-50% O2 (group SevoN2O) was enrolled after completion of the study. Induction was videotaped. EEG, heart rate, and finger blood pressure were continuously recorded during induction until 5 min after tracheal intubation and analyzed in frequency domain using spectral analysis. RESULTS: Agitation was more frequent when anesthesia was induced with 100% O2 compared to the mixture of oxygen and nitrous oxide. No seizures were recorded in any group. In the four groups, induction of anesthesia was associated with an increase in EEG total spectral power and a shift toward the low-frequency bands. Sharp slow waves were present on EEG tracings of the three sevoflurane groups, whereas slow waves and fast rhythms (spindles) were observed in the halothane group. Sevoflurane induced a greater withdrawal of parasympathetic activity than halothane and a transient relative increase in sympathetic vascular tone at loss of eyelash reflex. CONCLUSIONS: Agitation observed during sevoflurane induction was not associated with seizures. Sevoflurane induction induced a marked inhibition of parasympathetic control of heart rate.

Anesthesia, Inhalation↗
PubMed1999

Comparison of three techniques for induction of anaesthesia with sevoflurane in children.

This study was designed to evaluate the clinical characteristics of three induction techniques using sevoflurane in children scheduled for tonsillectomy: incremental induction with sevoflurane(2,4,6,7%) in 100% O2 (group IC-O2; n=23); induction with high concentration of sevoflurane in 100% O2 (group HC-O2; n=22); and induction with high concentration of sevoflurane in a mixture of O2:N2O(50:50) (group HC-N2O; n=20). Induction was well accepted and well tolerated in most children. The addition of nitrous oxide resulted in faster loss of consciousness (P< 0.001) compared to the other induction techniques and in a tendency for reduced excitement compared with the same rapid technique without nitrous oxide (P=0.053). Time to tracheal intubation was identical in the three groups and intubation conditions were scored as good in most children. During the early induction phase, an increase in SAP and HR was observed in the three groups. Changes were maximal at two min after the beginning of induction in the three groups. SAP and HR values were back to baseline values at the time of tracheal intubation. In conclusion, the addition of nitrous oxide to a high sevoflurane concentration decreases the time to loss of eyelash reflex, tends to reduce the incidence of excitement and is not associated with an increased incidence of respiratory complications even in patients with obstructive airway.

Analysis of Variance↗
PubMed1996

Pharmacokinetics of tiaprofenic acid in infants after a single oral dose.

Ten healthy infants (15.2 +/- 10.6 months old, range 6-35) anesthetized for minor surgery were given a single oral dose (3 mg x kg-1) of tiaprofenic acid (TA). Seven venous blood samples and 0-12 h urine were collected. TA concentrations in plasma and urine were measured by HPLC. Within the whole group the mean +/- SD kinetic parameters were: Cmax: 10.55 +/- 3.31 mg x l-1, Tmax: 1.73 +/- 0.87 h, AUC0-1 32.53 +/- 4.42 mg x l-1 x h, AUC0-infinity 35.33 +/- 4.73 mg x l-1 x h, t1/2 1.82 +/- 0.48 h, Cl/F: 0.09 +/- 0.01 l x h-1 x kg-1, VZ/F: 0.23 +/- 0.08 l x kg-1. Renal clearance was 0.030 +/- 0.009 l x h-1 x kg-1. 32% of the TA dose was recovered in urine, 60% of which was conjugated. AUC0-8h increased significantly with age. The TA kinetic parameters were close to those in 3 to 11-year-old children. The present study suggests slight differences in the TA kinetics between infants and adults. However, the lack of an evidenced direct relationship between plasma TA concentration and either efficacy or tolerance suggests that the TA dose regimen in infants may not have to be different from that in adults.

Administration, Oral↗
PubMed1995

[Sevoflurane].

Sevoflurane, a methylethylether halogenated solely with fluorine, is characterized by a low blood/gas solubility (blood/gas partition coefficient = 0.65). This feature allows in a more rapid uptake and elimination than with more soluble agents. MAC is about 2 vol% in young adults and 2.5 vol% in children of more than 6 months of age. It undergoes degradation by soda lime in various components. Among them, compound A (an olefin) produces renal toxicity in rats. Total sevoflurane metabolism represents about 5% of inhaled dose and produces inorganic fluorides. However no renal toxic effects has been reported up to now in animals and in patients. The effects on central nervous and cardiovascular systems are close to those of isoflurane. It decreases cerebral vascular resistances and cerebral oxygen consumption, but does not cause convulsive activity. It decreases myocardial contractility, systolic arterial pressure and systemic vascular resistances, but heart rate remains basically unchanged up to 1 MAC. It does not sensitize the myocardium to catecholamines. It depresses ventilation in a dose-dependent fashion, this effect being more pronounced than that of halothane but less than that of both isoflurane and enflurane. It is not irritant for the airways and has some bronchodilatory effect. In adults, recovery is more rapid than with isoflurane. In children, sevoflurane seems a promising agent owing to its good acceptance for mask induction, as well as its favourable haemodynamic profile. However due to its rapid elimination, analgesic drugs should be administered early enough to decrease the incidence of postoperative pain.

Adolescent↗
PubMed1995

Pharmacokinetics of cetirizine in 2- to 6-year-old children.

Eight children (3.84 +/- 1.17 years old) received a single oral 5 mg cetirizine dose (0.32 +/- 0.07 mg.kg-1) as a 10 mg.ml-1 solution, 1.73 (+/- 0.64) hours before a minor surgical intervention (mean duration +/- SD = 0.90 +/- 0.25 h). Seven venous blood samples were collected before administration (t0) and 0.5 h, 1.5 h, 4 h, 8 h, 12 h and 24 h after dosing, and urine samples were collected up to 24 hours after the dose. The mean +/- SD kinetic parameters were: peak plasma level (Cmax) 607 +/- 231 micrograms.l-1 reached in 1.93 +/- 1.39 h (tmax), elimination half-life (t1/2) 5.55 +/- 0.98 h, area under the plasma concentration time curve (AUC0-infinity) 4,772.1 +/- 1,318.4 micrograms.l-1.h, mean residence time (MRT) 8.13 +/- 1.31 h, apparent plasma clearance (Cl/f) 1.27 +/- 0.80 ml.min-1.kg-1, apparent volume of distribution (Vz/f) 0.60 +/- 0.38 l.kg-1. Urinary recovery was 38.4 +/- 9.9% (n = 4) of the dose. Renal clearance was 0.42 +/- 0.10 ml.min-1.kg-1 (n = 6). No influence of age on the cetirizine parameters was evidenced among this group, except for MRT (p < 0.05) which decreases with age. When compared with results in adults, elimination half-life (t1/2) was twice as short and apparent clearance twice as great. These results suggest that a higher dosage b.i.d. may be required in children.

Administration, Oral↗
PubMed1994

Stereoselective disposition of ibuprofen enantiomers in infants.

The pharmacokinetics of the enantiomers of ibuprofen were investigated after oral administration of a single 7.6 +/- 0.3 mg kg-1 dose of the racemate in 11 infants. Mean (+/- s.d.) half-lives were 1.6 +/- 0.5 h for S(+) and 1.5 +/- 0.5 h for R(-) and mean (+/- s.d.) AUC values were 31.5 +/- 14.3 mg l-1 h for S(+) and 36.6 +/- 13.8 mg l-1 h for R(-). Since plasma concentrations of the active S(+)-isomer were lower than those reported in adults, a higher dosage might be required in infants.

Administration, Oral↗
PubMed1994

Correlation between fusogenicity of synthetic modified peptides corresponding to the NH2-terminal extremity of simian immunodeficiency virus gp32 and their mode of insertion into the lipid bilayer: an infrared spectroscopy study.

The amino-terminal extremity of the simian immunodeficiency virus (SIV) transmembrane protein (gp32) has been shown to play a pivotal role in cell-virus fusion and syncytium formation. We provide here evidence of a correlation between the structure and orientation of the modified SIV fusion peptide after insertion into the lipid membrane and its fusogenic activity. The sequence of the wild-type SIV peptide has been modified in such a way that the calculated angles of insertion correspond to an oblique, parallel, or normal orientation with respect to the lipid-water interface. Fourier transform infrared spectroscopy was used to gain experimental informations about the structures and orientations, of the membrane-inserted peptides with respect to the lipid acyl chains. The peptides adopt mainly a beta-sheet conformation in the absence of lipids. After interaction with large unilamellar liposomes, this beta sheet is partly converted into alpha helix. The ability of the modified peptides to promote lipid mixing was assessed by a fluorescence energy transfer assay. The data provide evidence that alpha-helix formation is not sufficient to induce lipid mixing and that the fusogenic activity of the peptide depends on its orientation in the lipid bilayer.

Amino Acid Sequence↗
PubMed1994

Induction and recovery characteristics and hemodynamic responses to sevoflurane and halothane in children.

The present study was designed to compare induction and recovery characteristics of sevoflurane and halothane anesthesia in children, and to assess the hemodynamic profile of both anesthetics during induction and maintenance of anesthesia. Thirty-four children (aged 9 mo-9 yr) scheduled for ambulatory surgery were allocated randomly to groups to receive either halothane (HALO, n = 17) or sevoflurane (SEVO, n = 17) in a mixture of O2 and N2O (40:60) for mask induction and maintenance of anesthesia. The inspired concentrations used for inhalation via a mask were increased every five breaths and were successively 1%, 2%, 3%, and 3.5% for HALO and 2%, 4%, 6%, and 7% for SEVO. After tracheal intubation, expired concentration was maintained at 1 minimum alveolar anesthetic concentration (MAC) corrected for age until skin closure. Analgesia was provided by epidural anesthesia using a mixture of plain 1% lidocaine and 0.25% bupivacaine. Induction and recovery characteristics as well as hemodynamic data were recorded. The two groups were identical in age, weight, and duration of anesthesia and surgery. Time to intubation was the same between groups. In the SEVO group, five children exhibited mild excitement, while in the HALO group, one mild laryngospasm and one transient cardiovascular deterioration were observed. In the SEVO group, a significant increase in heart rate (HR) was observed before tracheal intubation, but during maintenance of anesthesia HR and systolic arterial pressure (SAP) did not change compared to control values. In the HALO group, HR did not change throughout the study, whereas SAP remained significantly below control values throughout both induction and maintenance of anesthesia.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia↗
PubMed1993

Lysophosphatidylcholine mediates the mode of insertion of the NH2-terminal SIV fusion peptide into the lipid bilayer.

We report here on the interaction of a synthetic 12 residue peptide corresponding to the N-terminal sequence of gp32 from SIV with phospholipid bilayers. This peptide has been shown to induce lipid mixing of PC/PE/SM/Chol LUV (large unilamellar vesicles) at pH 7.4 and 37 degrees C [(1992) in: Advances in Membrane Fluidity, vol. 6, pp. 365-376, Wiley-Liss]. In the present study, this fusion process was inhibited by the addition of lysophosphatidylcholine (lysoPC) to the lipid bilayer of PC/PE/SM/Chol LUV. Fourier transform infrared spectroscopy (FTIR) reveals that the orientation of the SIV fusion peptide with respect to the lipid acyl chains depends on the presence of lysoPC in the lipid bilayer but that the peptide secondary structure and the amount of lipid-associated peptides do not depend on the lipid composition. The peptide is obliquely inserted into the lipid bilayer of vesicles without lysoPC, whereas it is oriented parallel to the lipid-water interface in the vesicles containing lysoPC. The data provide evidence that the orientation of the SIV fusion peptide depends on the lipid composition, and that this mediates its fusogenic activity.

Kinetics↗
PubMed1993

[Anesthesia in the management of pyloric stenosis. Evaluation of the combination of propofol-halogenated anesthetics].

This study was aimed at evaluating haemodynamic changes during an anaesthetic sequence for full stomach, using propofol as induction agent and volatile anaesthetics for maintenance of anaesthesia in infants scheduled for surgical cure of hypertrophic pyloric stenosis. After correction of preoperative blood electrolyte and metabolic disturbances with appropriate i.v. hydrating solutions, anaesthesia was induced with propofol and suxamethonium. Infants were divided in two groups according to the volatile anaesthetic agent used for maintenance of anaesthesia after tracheal intubation: halothane (n = 16) or isoflurane (n = 15). The two groups were identical regarding weight (4.28 +/- 0.6 vs 4.14 +/- 0.76 kg), age (1.6 +/- 0.9 vs 1.5 +/- 0.6 months), preinduction heart rate (155 +/- 22 vs 151 +/- 22 b.min-1) and systolic-diastolic arterial pressure (96 +/- 18/58 +/- 12 vs 105 +/- 16/67 +/- 15 mmHg). Propofol and suxamethonium doses were identical, 3.9 +/- 1 mg.kg-1 and 1.3 +/- 0.6 mg.kg-1 respectively in halothane group, vs 4.3 +/- 0.8 mg.kg-1 and 1.3 +/- 0.4 mg.kg-1 in isoflurane group. Heart rate did not change after induction of anaesthesia, while arterial blood pressure decreased significantly (p < 0.001). However, blood pressure remained within the normal range for age throughout the procedure. Mean duration of surgery was shorter in halothane group (64 +/- 16 vs 79 +/- 17 min, p < 0.05), however time-interval from the end of surgery to tracheal extubation (12 +/- 6 vs 15 +/- 8 min) was short and identical in the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, General↗
PubMed1993

[Perioperative perfusion in children: evaluation of a new perfusion solution].

A new intravenous solution (B66) containing 0.9% dextrose in water for infusion therapy in infants and children was assessed. Forty-one children, aged between 6 months and 11 years, scheduled for elective non haemorrhagic surgery, were randomly assigned to two groups: children in group I (n = 22) were given 1% dextrose in lactated Ringer's solution (RLG1), and those in group II (n = 19) the commercially available solution B66 (0.9% dextrose in lactated Ringer's solution). The fluids were administered throughout the study with volumetric infusion pumps (IVAC 541). The infusion rate was adapted to children's weight and age. Blood samples for blood glucose, sodium and protein concentration assessments were obtained at induction (T0), on arrival in the recovery room (T1), than 30 and 60 min later (T2 and T3). Preoperative blood glucose concentrations were within the normal range for all children except for two, who had asymptomatic hypoglycaemia (2.2 and 2.3 mmol.l-1). Postoperative blood glucose concentrations were higher in both groups. This increase was significantly greater in the RLG1 group than in the B66 group. The highest mean figures at T1 were 6.8 +/- 1.5 mmol.l-1 and 5.2 +/- 1.0 mmol.l-1 in the RLG1 and B66 groups respectively. Total protein levels decreased postoperatively significantly in both groups. Preoperative age-related differences in total protein concentrations were also observed postoperatively. Sodium concentrations remained unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Glucose↗
PubMed1993

Comparison of two anesthesia techniques on perioperative insulin response to i.v. glucose infusion in children.

Perioperative blood glucose and insulin levels were measured in children (1-9 years of age) randomly assigned to two groups according to anesthesia technique, general anesthesia (group GA) or general anesthesia combined with regional anesthesia (group RA). Children in the GA group (n = 10) received halothane and opioids, while children of the RA group received epidural anesthesia with bupivacaine (0.25%) and adrenaline combined with halothane anesthesia (n = 10). Children in both groups received 2.5% dextrose in 0.4 N saline administered by volumetric infusion pumps throughout the study period, the infusion rate being adapted to the child's age. Blood samples for glucose and insulin determinations were obtained: at induction, at the end of surgery, and 30, 60 and 120 min after surgery. In response to an identical glucose load, blood glucose levels increased significantly in both groups (P < 0.001), while no differences between groups were observed. Insulin levels did not change significantly postoperatively in the GA group (P = 0.058), while a significant increase was observed in the RA group (P < 0.001). Insulin/blood glucose ratio increased significantly only in the RA group (P < 0.05). The higher insulin secretion in response to glucose infusion in the RA group compared to the GA group may indicate an increased peripheral insulin resistance after regional anesthesia or, more likely, this secretion may be beneficial in contributing to improve postoperative nitrogen balance.

Anesthesia, Conduction↗
PubMed1992

Apolipoprotein A-1 interacts with the N-terminal fusogenic domains of SIV (simian immunodeficiency virus) GP32 and HIV (human immunodeficiency virus) GP41: implications in viral entry.

Previous studies showed that apoA1, the major protein component of HDL (High Density Lipoprotein), inhibited HIV infectivity and virus-induced syncytia formation. The mechanism of inhibition is unknown. We bring here evidence that the amphipathic helices of apoA1 interact with the N-terminal peptides of SIV gp32 and HIV gp41. These peptides have been shown to be associated with the initial steps of the fusion between the host cell and the virus. Binding of apoA1 to these peptides prevents the insertion of the fusogenic domains into the cell membrane and inhibits the fusion and the entry of the virus into the host cell.

Amino Acid Sequence↗
PubMed1991

[Patient-controlled analgesia in children].

This study describes the author's initial experience with "patient controlled analgesia" (PCA) in thirty school-age children for postoperative pain relief after major orthopedic surgery. The only narcotic used was morphine administered at both continuous and PCA modes. After the first eight patients, dosage regimens were changed and satisfactory postoperative analgesia was obtained in the last 20 patients with few side-effects. Recommended dosages range between 0.1 and 0.2 mg.kg-1 for loading dose, 0.01-0.02 mg.kg-1.h-1 for continuous infusion and 0.01-0.02 mg.kg-1 for PCA dose. Interest and limits of this method in children are discussed.

Adolescent↗
PubMed1983

Hepatitis B vaccine: clinical trials in high-risk settings in France. (September 1975-September 1982).

An alum bivalent hepatitis B vaccine containing 5 micrograms/dose of formalin-inactivated and purified HBsAg has been prepared from plasma of HBeAg negative donors. Safety of the product has been controlled by compulsory testing of each batch in susceptible chimpanzees. This vaccine (HB vaccine) was used for the prophylaxis of Hepatitis B in hospital staff working in high-risk settings and patients undergoing periodic dialysis since the Autumn of 1975. Tolerance to the HB vaccine was excellent both in staff and patients as assessed by a nation-side survey on a thousand vaccinees. More than 96% of the staff developed protective levels of anti-HBs after three injections of vaccine given at one month intervals and became fully immune from HBV infection. A booster injection given at one year stimulated an anamnestic rise of anti-HBs sufficient to ensure protective levels of antibody for at least five years post-booster. The response of renal patients varied according to the age of recipients: young patients responded equally as well as the healthy staff, while patients over the sixth decade had a lower and delayed response. Because of that, a fourth injection of HB vaccine was advocated in elderly patients. Dialysis patients who developed anti-HBs either after three or four injections were fully protected against chronic HBV infections. Anti-HBs positive donors who had received a single booster injection of HB vaccine and vaccinees who had received their 12 months booster were both found to be an adequate source of high-titre anti-HBs plasma for preparing hyperimmune anti-HBs globulin. The HB vaccine which is manufactured by Institut Pasteur Production under the name HEVAC B degrees is now used world-wide for the prophylaxis of hospital acquired infection in developed countries and for the prevention of maternal-infant transmission in the endemic countries of Asia and Africa.

Adult↗