Biomedical subjects

A G Burm

Publications and source records attributed to A G Burm.

At least 91 records · Page 5Linked to original sources

PubMed1988

Age has no effect on the pharmacodynamics of alfentanil.

Effects of age on the pharmacodynamics of alfentanil, as a supplement to nitrous oxide anesthesia, were studied in younger (31-52 years; n = 14) and older (56-86 years; n = 14) women undergoing curative surgery for primary breast cancer. Plasma alfentanil concentration-effect curves for perioperative stimuli and for the probability of needing naloxone at the end of the operation were fitted by logistic regression. Effects of age on the plasma concentration-effect relation of alfentanil could not be demonstrated. However, the dose requirement in the older patient group was significantly lower than in the younger patient group.

Adult↗

PubMed1988

Alfentanil infusion in the elderly. Prolonged computer-assisted infusion of alfentanil in the elderly surgical patient.

The use of a computer-assisted infusion of alfentanil, combined with 66% nitrous oxide in oxygen, for induction and maintenance of anaesthesia was evaluated in 18 elderly patients. The target alfentanil concentration for induction was varied between 300 and 475 ng/ml, to be achieved in 2 minutes. During maintenance, the alfentanil concentration was increased or decreased according to each patient's responses. Arterial blood samples were taken for measurement of alfentanil concentration. There were high incidences of muscle rigidity, bradycardia and hypotension during induction. Hypotension was dose- and concentration-dependent. Signs of light anaesthesia during maintenance were controlled rapidly by increasing the target plasma concentration. Nine patients required naloxone at the end of surgery. Ventilatory depression recurred in three of these. The use of published alfentanil pharmacokinetic data from elderly patients to predict plasma concentrations during prolonged infusion resulted in significant prediction errors, notably in the higher concentration range.

Aged↗

PubMed1987

Pharmacokinetics of lignocaine and bupivacaine in surgical patients following epidural administration. Simultaneous investigation of absorption and disposition kinetics using stable isotopes.

The pharmacokinetics of lignocaine (lidocaine) and bupivacaine following epidural administration were studied in 12 surgical patients using a stable isotope method. Shortly after epidural administration of the agent to be evaluated, a deuterium-labelled analogue was administered intravenously. Plasma concentrations of the unlabelled and the deuterium-labelled local anaesthetics were determined using gas chromatography and mass fragmentography. The pharmacokinetic behaviour of both agents was consistent with a 2-compartment open model and two parallel first-order absorption processes. The mean distribution and elimination half-lives were 12 minutes and 100 minutes for lignocaine, and 22 minutes and 143 minutes for bupivacaine. The mean volumes of the central compartment and the mean steady-state volumes of distribution were: lignocaine, 43L and 99L; bupivacaine, 33L and 68L. Total plasma clearances averaged 0.95 L/min (57 L/h) for lignocaine and 0.52 L/min (31.2 L/h) for bupivacaine. The half-lives, characterising the fast and slow absorption processes, were 9.3 and 82 minutes for lignocaine, and 7.0 minutes and 362 minutes for bupivacaine; the fractions of the doses absorbed in the fast and slow processes were lignocaine 0.38 and 0.58, bupivacaine 0.28 and 0.66, respectively. The results indicate that the local anaesthetics are completely absorbed from the epidural space into the general circulation. The initial absorption rates of both local anaesthetics appear to be similar, but, later, the absorption of bupivacaine proceeds much more slowly than the absorption of lignocaine.

Absorption↗

PubMed1987

Epidural anesthesia with bupivacaine: effects of age on neural blockade and pharmacokinetics.

Effects of aging after epidural administration of 0.5% bupivacaine without epinephrine were studied in two groups of patients, between 20 and 55 yr old and older than 55 yr, respectively. All patients received 95 mg bupivacaine HCl. The onset of analgesia in caudad segments decreased with age and the upper level of analgesia increased with age. Effects of age on duration of anesthesia could not be demonstrated. The total plasma clearance of bupivacaine decreased and the terminal half-life increased with age. Age had no effect on the peak plasma concentrations and time to peak concentrations.

Adult↗

PubMed1987

Spinal anesthesia with glucose-free bupivacaine: effects of age on neural blockade and pharmacokinetics.

Effects of age on spinal anesthesia using glucose-free 0.5% bupivacaine without epinephrine were studied in two groups of patients, one between 20 and 55 yr old, the other older than 55 yr. All patients received 15 mg bupivacaine. The time to onset of analgesia in caudad segments and the time to maximal motor blockade decreased with age. The upper level of analgesia did not change significantly with increasing age. The times to recovery from analgesia at T12 and for the total disappearance of analgesia were longer in the older patient group. Effects of age on duration of motor blockade could not be demonstrated. Peak plasma concentrations of bupivacaine were significantly greater and the total plasma clearance significantly decreased in older patients. Age had no effect on time to peak concentration or the terminal half-life.

Adult↗

PubMed1987

Spinal anesthesia with hyperbaric lidocaine and bupivacaine: effects of epinephrine on the plasma concentration profiles.

The effects of epinephrine on the plasma concentration profiles and some derived pharmacokinetic parameters were studied after subarachnoid injection of hyperbaric lidocaine and bupivacaine solutions. Addition of epinephrine to the local anesthetic solution reduced the mean peak plasma concentration of lidocaine from 526 to 376 ng/ml, but did not significantly reduce the mean peak plasma concentration of bupivacaine (70 vs 56 ng/ml). Epinephrine did not affect the times at which the peak concentrations were reached, the terminal half-lives, or the total plasma clearances. The observed effects of epinephrine on the peak plasma concentrations are consistent with the vascular activity of lidocaine and bupivacaine, respectively.

Adult↗

PubMed1986

Plasma concentrations of alfentanil required to supplement nitrous oxide anesthesia for general surgery.

To design an efficient infusion regimen from pharmacokinetic data, it is necessary to know the alfentanil plasma concentrations required for satisfactory anesthesia. In 37 patients about to undergo lower abdominal gynecologic, upper abdominal, or breast surgery, anesthesia was induced with alfentanil 150 micrograms/kg iv and 66% N2O in oxygen. Thereafter, N2O anesthesia was supplemented with a continuous infusion of alfentanil that was varied between 25 and 150 micrograms X kg-1 X h-1, as indicated by the patient's responses to surgical stimulation. Small bolus doses of alfentanil 7 or 14 micrograms/kg were administered and the infusion rate increased to suppress precisely defined somatic, autonomic, and hemodynamic responses. Arterial plasma concentrations of alfentanil were measured during the operation when the patient did and did not respond to noxious stimulation. Logistic regression was used to determine plasma concentration-effect curves for different stimuli. Plasma alfentanil concentrations required along with 66% N2O to obtain responses to single episodes of stimulation in 50% of the 37 patients (Cp50 +/- SE) were: 475 +/- 28 ng/ml for tracheal intubation, 279 +/- 20 ng/ml for skin incision, and 150 +/- 23 ng/ml for skin closure. Between skin incision and closure, multiple determinations of response/no response were made for each patient and an individual Cp50 was estimated. The Cp50 (mean +/- SD) for the three surgical procedures were: breast, 270 +/- 63 ng/ml (n = 12); lower abdominal, 309 +/- 44 ng/ml (n = 14); and upper abdominal, 412 +/- 135 ng/ml (n = 11). The Cp50 for satisfactory spontaneous ventilation after the discontinuation of N2O was 223 +/- 13 ng/ml. These data demonstrate that different perioperative stimuli require different alfentanil concentrations to suppress undesirable responses. Thus, the alfentanil infusion rate should be varied according to the patient's responsiveness to stimulation in order to maintain satisfactory anesthetic and operative conditions and to provide rapid recovery of consciousness and spontaneous ventilation.

Adult↗

PubMed1986

Epidural anesthesia with lidocaine and bupivacaine: effects of epinephrine on the plasma concentration profiles.

The effects of epinephrine on the plasma concentrations and derived pharmacokinetic parameters were studied after epidural administration of lidocaine and bupivacaine. Addition of epinephrine to the local anesthetic solutions reduced the mean peak plasma concentrations of lidocaine and bupivacaine from 2.2 to 1.7 micrograms/ml (23%) and from 0.73 to 0.53 microgram/ml (28%), respectively, but did not alter the times at which the peak concentrations were reached. Epinephrine also did not alter the terminal half-lives or the total plasma clearances. The results suggest that addition of epinephrine to minimize plasma concentrations is as relevant with bupivacaine as it is with lidocaine.

Adult↗

PubMed1983

Plasma concentrations of lidocaine and bupivacaine after subarachnoid administration.

Plasma concentrations were measured after subarachnoid administration of 75 mg lidocaine in a hyperbaric solution and 15 mg bupivacaine in either a hyperbaric or an isobaric solution. Peak concentration times (tmax), peak concentrations (Cmax), apparent elimination half-lives (t1/2el), and areas under the curves (AUC) were determined. The values of tmax, Cmax, t1/2el and AUC were 66 +/- 32 min, 444 +/- 203 ng/ml, 2.0 +/- 0.3 h, and 87.0 +/- 9.8 mg . 1(-1) . min, respectively, for lidocaine. Those obtained after administration of a hyperbaric bupivacaine solution were 54 +/- 11 min, 63 +/- 22 ng/ml, 3.6 +/- 1.4 h, and 19.1 +/- 5.4 mg . 1(-1) . min. Results, obtained with isobaric bupivacaine solutions, were: 86 +/- 24 min, 63 +/- 15 ng/ml, 3.2 +/- 0.4 h, and 18.1 +/- 5.4 mg . 1(-1) . min. The results indicate roughly similar absorption rates from the subarachnoid space into the general circulation after administration of hyperbaric solutions of lidocaine and bupivacaine. Bupivacaine tended to be absorbed slower when it is administered in an isobaric solution.

Adolescent↗

PubMed1982

Gas chromatographic determination of bupivacaine in plasma using a support coated open tubular column and a nitrogen-selective detector.

A capillary gas chromatographic method for the quantitative determination of bupivacaine in plasma is described. Bupivacaine and an added internal standard were extracted from plasma with n-pentane. The extracted products were introduced into the gas chromatograph via a solid injection system. The combination of a support coated open tubular column and a nitrogen-selective detector insure a good selectivity and a high sensitivity. The coëfficient of variation at concentrations exceeding 3 ng bupivacaine/ml plasma is less than 6%. The detection limit is about 1 ng/ml.

Bupivacaine↗

PubMed1982

The influence of pressure swings on the output of plenum vaporizers.

The influence of pressure swings on the output of Dräger Vapor, Dräger Vapor 19, Cyprane Fluotec Mark 2, Cyprane Fluotec Mark 3 and Ohio halothane vaporizers was investigated. It is shown that significant deviations from the dial setting occur with all vaporizers if the swings are large enough. The sensitivity for pressure swings is largest at low dial settings and low carrier flow rates. The results indicate that swings, occurring during assisted or controlled intermittent positive pressure ventilation, can induce significant deviations at low carrier flow rates. The frequency and in-/expiration time ratio are relatively of minor importance.

Anesthesia, Inhalation↗

PubMed1982

A central low vacuum pipeline system for the disposal of waste anaesthetic gases.

An independent low vacuum pipeline system for scavenging waste anaesthetic gases is described. The pipeline system has terminal points in several operating and induction rooms. At each terminal point a connection box is installed, eigher in the wall or in a ceiling pendant. Excess gases from the anaesthetic apparatus or the patient ventilator are collected in a reservoir and subsequently sucked through the pipeline system, together with a surplus of air, extracted from the room via openings in the terminal box. The total suction rate is 100 1/min at each terminal box. Once connected, the system needs no looking after by the anaesthetist. Sub-atmospheric and positive pressures, measured at the point of connection to the anaesthetic apparatus are always between -11 Pa and +60 Pa, complying with the current standards.

Anesthesiology↗

PubMed1981

The Leiden scavenging system: A simple and versatile apparatus to control air pollution in operating rooms.

A scavenging system which can be attached to a variety of anaesthetic machines and ventilators is described. Gas venting can occur via a central vacuum system, a suitable injector, fan or pump, through the exhaust duct of an air-conditioning system, or by a passive system. The resistance and back pressures applied to the anaesthetic apparatus are negligible. Leakage tests showed that the collected gases and vapours were substantially removed by the scavenging device.

Air Pollution↗

PubMed1981

Effect of epidural administration of bupivacaine (Marcaine) on monosynaptic reflex-depression.

The L5 and S1-segments of the spinal cord and relatively resistant to blockade. The extent and depth of the block are usually tested by pinprick. H-reflex depression (Hoffmann 1922, Magladery and McDougal 1950) was used to quantify differences between the 0.5%-solution and the 0.75%-solution of bupivacaine used for epidural anaesthesia. The H-reflex is a monosynaptic reflex representing the excitability of the motorneuron pool of the L5-S1 region of the spinal cord. Our results show a difference between the two concentrations favouring the 0.75% solution. The H-reflex is also a component in the complexity of control and servocircuits that play a role in the well-functioning of the spinal cord. Consequently we used its full recovery to rule out lasting toxic or irritating effects on the spinal cord. Bupivacaine 0.75% is not available in Europe whereas in the USA there is already wide experience in using this concentration. A comparison between 0.75% and 0.5% solutions reveals two important advantages in favour of the 0.75% solution: A higher intensity of motorblock [4, 15]. A lower incidence of incomplete blockade of the most resistant segments (L5-S1) [7, 8].

Action Potentials↗

PubMed1980

The Leiden scavenging system: a simple and effective anti-pollution device.

The Leiden scavenging system, a device to reduce air pollution by anesthetic gases and vapours in operating rooms, is described. The system can be used in combination with different suction sources (vacuum pipeline, injector, fan or pump, air conditioning system). A special disposal network, to be used in combination with the scavenging system, is also shown.

Air Conditioning↗

PubMed1979

A method for sampling halothane and enflurane present in trace amounts in ambient air.

A method for the sampling of small amounts of halothane and enflurane in ambient air is described. Sampling is performed by drawing air through a sampling tube packed with Porapak Q, which absorbs the anesthetic agent. The amount absorbed is determined by gas chromatography after thermal desorption. This method can be used for "spot" or personal sampling or for determining mean whole-room concentrations over relatively long periods (several hours).

Air Pollution↗

PubMed1979

Mutagenicity studies with halothane in Drosophila melanogaster.

Halothane was investigated for its mutagenic effects in Drosophila melanogaster. The induction of sex-linked recessive lethals was used as an indicator of genetic damage. Adult male flies were exposed to halothane either for 14 days at 1,000 or 1,600 ppm (v/v) or for one or two days in 2,100 or 20,000 ppm. In several experiments slight increases of the mutation frequency were observed. For the pooled data of the 14 day-exposure experiments, the increase amounted to a doubling of the spontaneous rate, just reaching the level of 5 per cent significance. The authors consider this a borderline result, indicating, with a fair degree of probability, that halothane has weak mutagenic activity, under the conditions studied.

Animals↗

PubMed1978

Failure to replicate negative effects of trace anaesthetics on mental performance.

Twenty-four male subjects individually undertook a selection of cognitive tasks during each of two different 2-h sessions in a climatic chamber. Twelve subjects breathed a mixture of air, nitrous oxide 1600 p.p.m. (v/v) and halothane 16 p.p.m. (v/v) during the first session, and air alone during the second session 1 week later. For the other 12 subjects the order was reversed. The tests comprised learning a list of word-number pairs, solving a set of anagram problems, recognizing words and numbers, recalling word-number pairs and performing a four-choice audiovisual reaction time task. Testing was commenced after 45 min of exposure to the atmospheric conditions. A strong learning effect both within and between sessions was observed on the audiovisual task. None of the tasks, however, reflected any adverse effect of the trace anaesthetics.

Anesthetics↗