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Biomedical subjects

P Van der Aa

Publications and source records attributed to P Van der Aa.

7 recordsLinked to original sources
PubMed1996

Carboxyhemoglobin concentrations during desflurane and isoflurane closed-circuit anesthesia.

Desflurane has been implicated in carbon monoxide (CO) intoxication during general anesthesia under certain circumstances. Carboxyhemoglobin (COHb) concentrations were determined in forty-one patients who were randomly allocated to receive closed-circuit anesthesia (CCA) with 1.3 MAC of desflurane (n = 21) or isoflurane (n = 20) in oxygen. Soda lime was used to bind the produced CO2 in previous anesthetic procedures with fresh gas flows of < 21/min. In the desflurane group, COHb concentrations (mean +/- SD) were 0.86 +/- 1.15% and 0.81 +/- 1.11% before and after 1 h of anesthesia, respectively. In the isoflurane group, COHb concentrations were 1.15 +/- 1.47% and 1.19 +/- 1.39% before and after 1 h of anesthesia, respectively. COHb concentrations did not increase after 2 h of CCA in seven patients. Our data suggest that closed-circuit anesthesia with desflurane or isoflurane does not produce clinically significant increases in COHb concentrations under conditions that allow the soda lime to remain sufficiently wet.

Adult↗
PubMed1988

Alfentanil pharmacokinetics and metabolism in humans.

The metabolism of alfentanil was studied in three healthy subjects after a 1-h infusion of 2.5 mg alfentanil-3H. One of the subjects was a poor hydroxylator of debrisoquine. Pharmacokinetic parameters were similar in the three subjects and were in the same range as those reported for volunteers. The majority of the administered radioactivity was excreted in the urine (90% of the dose), but unchanged alfentanil represented only 0.16-0.47% of the dose. Alfentanil and metabolites were characterized by HPLC co-chromatography with reference compounds and/or by mass spectrometry and quantified by GLC and radio-HPLC. The main metabolic pathway was N-dealkylation at the piperidine nitrogen, with formation of noralfentanil (30% of the dose). Other Phase I pathways were aromatic hydroxylation, N-dealkylation of the piperidine ring from the phenylpropanamide nitrogen, O-demethylation, and amide hydrolysis followed by N-acetylation. Glucuronic acid conjugation of aromatic or aliphatic hydroxyl functions was the main Phase II pathway. The second major metabolite was the glucuronide of N-(4-hydroxyphenyl) propanamide (14% of the dose). The metabolite pattern in these subjects was qualitatively very similar to that described previously in rats and dogs. Differences in the mass balance of urinary metabolites between the three subjects were very small, and there was no qualitative or quantitative evidence for a deficiency in the metabolism of alfentanil in the subject who was a poor metabolizer of debrisoquine.

Alfentanil↗
PubMed1987

Plasma concentrations of epidural bupivacaine in mother and newborn: 0.125% versus 0.375%.

Central venous plasma concentrations of bupivacaine were determined in two groups of 15 parturients each who were given epidural analgesia for labor and vaginal delivery. One group received 10 ml of 0.125% bupivacaine plus epinephrine 1:800,000, the other group received 7 ml of 0.375% bupivacaine plus epinephrine 1:800,000. Plasma concentrations of bupivacaine in the umbilical venous (UV) and the umbilical arterial (UA) blood of their babies were also determined. The mean UA, UV, and maternal central venous (MV) plasma concentrations of bupivacaine differed significantly between the two groups: in patients given 0.375% bupivacaine UA values were 63% higher (P less than 0.01), UV values were 57% higher (P less than 0.01), and the MV values were 34% higher (P less than 0.05) than in patients given 0.125% bupivacaine. The measured plasma concentrations speak in favor of the less concentrated solution of bupivacaine in epidural analgesia for obstetrics. Seven milliliters of bupivacaine 0.375% is suitable for epidural analgesia in obstetrics but a low concentration-low dose technique, using 10 ml of bupivacaine 0.125% plus epinephrine 1:800,000 is safer. It provides good analgesia with minimal or no motor block and is associated with low maternal and neonatal plasma concentrations of bupivacaine, well below toxic levels and, to our knowledge, lower than in any other study.

Anesthesia, Epidural↗
PubMed1986

Motor blockade during epidural anesthesia.

The effects of lumbar epidural anesthesia (LEA) on a previously described test of function of the rectus abdominalis muscle (the RAM-test) were compared with the effects of LEA on the Bromage test of muscle power in the hips and legs in 20 women having elective cesarean sections under LEA using 0.5% bupivacaine with epinephrine 1:200,000. The results showed no statistically significant correlation between the two tests. We conclude that zones of differential somatic motor blockade are present during LEA and that in obstetrics the RAM-test is the more appropriate test for evaluating the effects of LEA on somatic motor function. Use of the RAM-test is suggested in situations where one is interested in motor function of the abdominal wall muscles under LEA.

Abdominal Muscles↗
PubMed1980

[Frequency analysis of the various stimuli used in brain stem electric response].

It was our aim to analyse the frequency spectra of these different stimuli in order to select the most suitable stimulus as one wants to apply BER either as objective audiometry or as oto-neurological means of diagnosis. The kind of stimulus is important because its characteristics will condition the parameters of the electro-physiological response. As oto-neurological means of diagnosis, it will be preferable to use the shortest possible stimulus and by no means a filtered stimulus. As objective audiometry, a long stimulus will be used with a less rough onset, which thus presents a narrow frequency spectrum and still creates a clear P5/FFP7 complex. For both applications the Logon offers the best compromise.

Audiometry↗