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Biomedical subjects

M Wood

Publications and source records attributed to M Wood.

At least 271 records · Page 15Linked to original sources
PubMed1986

The effect of cimetidine on anesthetic metabolism and toxicity.

Because the H2-receptor antagonist cimetidine has been shown to inhibit drug metabolism, the effects of cimetidine on anesthetic metabolism and toxicity were investigated in a rat model. Cimetidine decreased inorganic plasma fluoride production after methoxyflurane administration both in 21% oxygen (P less than 0.001) and in 100% oxygen (P less than 0.001). Phenobarbital produces an increased fluoride formation after methoxyflurane anesthesia, and this fluoride formation is also reduced by cimetidine (P less than 0.005). There was no significant difference between the plasma fluoride levels in rats anesthetized with halothane or enflurane. Although cimetidine inhibited the in vivo defluorination of methoxyflurane, fluoride levels were still within the nephrotoxic range, and cimetidine is not likely to play a role as part of a preanesthetic regimen that would permit the increased clinical use of methoxyflurane. Cimetidine also inhibited the oxidative metabolism of halothane; cimetidine decreased (P less than 0.05) trifluoroacetic acid concentrations after halothane anesthesia in 21% oxygen and in 100% oxygen and decreased (P less than 0.05) bromide concentrations after halothane anesthesia in 100% oxygen. Trifluoroacetic acid levels were less (P less than 0.02) after halothane anesthesia in 14% oxygen as compared with 100% oxygen, indicating a reduction in oxidative metabolism under hypoxic conditions. However, bromide concentrations were maximal after halothane anesthesia in 21% oxygen, and significantly (P less than 0.001) less after halothane anesthesia in 14% and 100% oxygen. Bromide production, therefore, seems to be inhibited by both hypoxia and hyperoxia.(ABSTRACT TRUNCATED AT 250 WORDS)

Alanine Transaminase↗
PubMed1985

Results of the international field trial with the Reason for Encounter Classification.

The Reason for Encounter Classification (RFEC) was designed by a WHO Working Party to classify the reasons why patients seek care at the primary care level. It is designed along two axes: Chapters and Components. Each chapter carries an alpha-code which is the first character of the basic 3-character alphanumeric code. Each chapter is subdivided into seven "components" carrying 2-digit numeric codes. The field trial was undertaken by family physicians and nurses in: Australia, Barbados, Brazil, Hungary, Malaysia, the Netherlands, Norway and the US. 90497 RFE's were analysed. Their distribution over the chapters and components characterize the content of international primary care. Listings with the most common RFE's in the participating countries reflect the cultural differences. It is concluded that the RFEC is not only feasible to classify reasons why patients seek care but also to classify the diagnosis and the process of primary care. As a result of this, the International Classification of Primary Care (ICPC) succeeds the RFEC.

Diagnosis↗
PubMed1985

Skin testing in the investigation of reactions to intravenous anaesthetic drugs. A prospective trial of atracurium and tubocurarine.

Intradermal skin testing is widely used to determine the causative drugs of presumed anaphylactic anaesthetic reactions. This paper sets out to evaluate the usefulness of skin tests, both intradermal and prick testing, in the prediction of anaesthetic reactions. The muscle relaxant drugs tubocurarine and atracurium were chosen for study since they are known to produce a high incidence of minor histaminoid reactions. A trial was conducted in 22 female patients about to undergo elective gynaecological surgery for non-malignant conditions. In intradermal tests, positive wheal and flare reactions to one or other relaxant (diluted 1 in 1,000) occurred in 17 patients and reactions to both drugs in 11 patients. Despite this high incidence of positive reactions, none of the patients had received either drug previously, a view confirmed by the negative results of prick testing. Likewise, when anaesthetized for surgery using atracurium or tubocurarine allocated randomly, the minor histaminoid manifestations observed showed no correlation whatsoever with the intradermal tests results. The results of the trial, combined with external reports to this centre, indicate that intradermal testing of anaesthetic drugs, particularly muscle relaxants, produces a high incidence of false positive results. This probably reflects their pharmacological activity rather than antigenicity. It is recommended, therefore, that skin testing should be reserved for situations in which there are strong indications from laboratory tests, backed by case history, of immune sensitization.

Adult↗
PubMed1985

Ultra-short-acting beta-blockade: a comparison with conventional beta-blockade.

Esmolol is a beta 1-selective adrenoceptor blocker that is rapidly metabolized by blood and liver esterases. The beta-receptor and hemodynamic effects of esmolol were determined in a group of 12 healthy men and were compared with those induced by both oral and intravenous propranolol. Esmolol was rapidly effective in inducing at least 90% of steady-state beta-blockade within 5 minutes of either initiating or changing the esmolol infusion rate. More importantly, when esmolol infusion was discontinued the beta-blockade had totally disappeared by 18 minutes after esmolol, 300 micrograms/kg/min, and had been reduced by 50% after 750 micrograms/kg/min. In contrast, 30 minutes after discontinuation of a propranolol infusion, there was no change in the level of beta-blockade. Propranolol was much more potent at blocking isoproterenol-induced tachycardia (dose ratio 33.5 +/- 2.5) than was even the highest dose (750 micrograms/kg/min) of esmolol (dose ratio 13.1 +/- 1.0). The same dose of intravenous propranolol was approximately equipotent to oral propranolol, 40 mg every 8 hours (dose ratio 33.5 +/- 2.5 and 34.5 +/- 3.6, respectively). In contrast, propranolol, 40 mg every 8 hours, and esmolol, 300 micrograms/kg/min, were equipotent in antagonizing exercise-induced tachycardia (40.1% +/- 2.3% and 42.7% +/- 3.2%, respectively). Esmolol had striking hypotensive effects. Systolic blood pressure fell by 20 mm Hg during esmolol infusions of 750 micrograms/kg/min. Esmolol appears to be a potent beta 1-selective adrenoceptor antagonist with a particularly strong hypotensive effect. It is likely to be very useful in the treatment of hemodynamically unstable patients and may be useful in the emergency treatment of hypertension.

Adrenergic beta-Antagonists↗
PubMed1985

The effect of halothane on drug disposition: contribution of changes in intrinsic drug metabolizing capacity and hepatic blood flow.

Several studies have shown that halothane may influence drug disposition in animals and humans, but the mechanism remains unclear. The relative contributions of changes in metabolizing capacity and hepatic blood flow to altered drug disposition were investigated during halothane anesthesia, using propranolol as a model compound. The studies were performed on six dogs on three separate days; first, the day before anesthesia, second, during halothane (2.0 MAC) anesthesia, and third, 24 h after anesthesia. Each dog simultaneously received 40 mg unlabeled propranolol directly into the portal vein and 200 mCi of 3H-propranolol intravenously via chronically implanted catheters. Blood samples were taken every 5 min for the first hour and then every 15 min for a further 3 h for the measurement of unlabeled and 3H-propranolol concentrations. During halothane anesthesia, intraportal-intrinsic clearance was decreased by 62% (P less than 0.05) from 2,110 +/- 298 to 799 +/- 233 ml/min, while systemic clearance was decreased (P less than 0.05) from 470 +/- 33 ml/min preanesthesia to 280 +/- 38 ml/min during halothane anesthesia. The intravenous elimination half-life was increased (P less than 0.05) from 87 +/- 12 to 155 +/- 23 min during anesthesia. Although halothane anesthesia tended to lower liver plasma flow from 642 +/- 80 to 473 +/- 47 ml/min, this change was not significant. The large change in portal or intrinsic clearance indicates that halothane anesthesia markedly inhibits drug-metabolizing ability. The authors therefore conclude that the alterations in drug disposition observed during halothane anesthesia are mainly due to inhibition of drug-metabolizing capacity in the liver.

Animals↗
PubMed1985

Variability of fentanyl pharmacokinetics in man. Computer predicted plasma concentrations for three intravenous dosage regimens.

The derived pharmacokinetic data for the intravenous administration of fentanyl obtained from seven previous studies were compared using computer simulation of predicted plasma concentrations following three intravenous dosage regimens. There was wide discrepancy between the reported calculated pharmacokinetic constants from the various studies, such that the volume of distribution ranged from 4.4 to 59.7 litres, estimates of terminal elimination half-life ranged from 141 to 853 minutes while total body clearance values ranged from 160 to 1530 ml/minute. The differences in predicted plasma concentrations were marked. The peak concentration following a bolus of 500 micrograms ranged from 8.4-113.6 ng/ml and took from 2.9 to 18.9 hours to fall to 0.5 ng/ml. The steady state plasma concentration reached with an infusion of 0.3 microgram/kg/minute varied from 12.2-119.9 ng/ml and the plateau level attained with a two-rate infusion (2.7 micrograms/kg/minute for 20 minutes then 0.3 micrograms/kg/minute) ranged from 10.6-50.8 ng/ml. The aim of descriptive pharmacokinetics is to allow the clinician to predict the plasma concentration achieved by a given dose and to facilitate dosage choice and adjustment. Recent interest has centred on the use of pharmacokinetics to calculate continuous intravenous infusion dosage regimens. The clinical application of current pharmacokinetic data for fentanyl is questionable.

Adult↗
PubMed1985

Etched castings. An alternative approach to treatment.

Resin-bonded restorations are a conservative alternative with excellent patient acceptance. Improvements in retainer design and electrolytic etching of cast metal allow these restorations to be utilized in a variety of clinical situations. The article reviews the development, indications and contraindications, design, and mouth preparation as well as variations of basic techniques, esthetics, and removal of retainers.

Acid Etching, Dental↗
PubMed1984

Fusion of oocytes and development of oocyte fusion products in the mouse.

Utilizing fusion techniques we demonstrated that 57-72% of meiotic mouse oocytes could be fused with polyethylene glycol. Activated oocyte fusion products (OFP) completed second meiosis and supported early embryonic development to the blastocyst stage (12%). Furthermore, when oocytes from MF1 strain that demonstrate a developmental block at the 2-cell stage when cultured from the zygote stage, were fused with oocytes of an F1 hybrid not demonstrating this block, the OFP overcame the 2-cell block and developed to blastocysts. Of the 20 blastocysts from OFPs that were transferred to pseudopregnant recipients 11 implanted and 1 F1 OFP developed to the 14-somite stage.

Animals↗
PubMed1984

Perioperative beta blockade with propranolol: reduction in myocardial oxygen demands and incidence of atrial and ventricular arrhythmias.

To determine the effect of beta blockade with propranolol on myocardial oxygen demands and postoperative arrhythmias in patients having coronary bypass operations, 50 patients with chronic stable angina undergoing operation were randomized in a double-blind fashion to receive either propranolol (60 mg every 6 hours) or a placebo. Drug administration began 24 to 48 hours prior to operation and continued through the operative period and for one month after operation. There were no deaths. Two perioperative myocardial infarctions occurred, both in patients receiving a placebo. Myocardial oxygen demand as measured by the rate-pressure product (heart rate X mean arterial pressure) was significantly reduced during induction of anesthesia (7,658 +/- 451 versus 5,786 +/- 340; p less than 0.002) and during sternotomy (8,400 +/- 550 versus 6,756 +/- 384; p less than 0.02) in propranolol-treated patients. In the first two postoperative days, nitroprusside was required for control of hypertension of 10 patients in the placebo group but in only 3 patients given propranolol (p less than 0.05). Postoperatively, 15 of the 26 patients who received a placebo had 45 episodes of arrhythmia. Seven of the 24 propranolol-treated patients had 17 episodes (p less than 0.04). We conclude that propranolol given perioperatively in doses large enough to induce beta blockade significantly reduces myocardial oxygen demands in the vulnerable period during induction of anesthesia and sternotomy, reduces the need for antihypertensive therapy in the immediate postoperative period, and causes a marked reduction in the incidence and frequency of both supraventricular and ventricular arrhythmias in the postoperative period.

Angina Pectoris↗
PubMed1984

Contrasting effects of halothane, isoflurane, and enflurane on in vivo drug metabolism in the rat.

Inhalational anesthetics might affect perioperative drug elimination by alterations in distribution, hepatic blood flow, or metabolism. The purpose of our study was to investigate the effects of inhalational anesthetics on drug metabolism in vivo during the pre- and postanesthetic periods. The aminopyrine breath test was used as a sensitive non-invasive index of drug metabolism, when the rate of elimination of 14CO2 in the exhaled breath of rats was measured after the intravenous administration of (N-dimethyl-14C) aminopyrine. The rate of aminopyrine metabolism was determined on three occasions in each rat; on the day prior to anesthesia and again 2 and 24 hr after anesthesia. The rats were anesthetized for 2 hr with halothane (0.125%, 0.25%, or 1.0%), enflurane (1.8%), or isoflurane (1.3%) in air. Halothane (P less than 0.05) prolonged aminopyrine half-life both 2 and 24 hr after anesthesia. This was a dose-dependent effect with higher concentrations of halothane causing greater impairment of aminopyrine metabolism 24 hr after anesthesia. Halothane (1.0%) increased the aminopyrine half-life from 41.3 +/- 0.9 min to 54.6 +/- 3.5 min 2 hr after anesthesia and to 54.0 +/- 3.5 min 24 hr after anesthesia. Although isoflurane (1.3%) caused a slight prolongation (P less than 0.05) of aminopyrine half-life 2 hr after anesthesia, this effect had disappeared by 24 hr. Enflurane (1.8%) did not affect aminopyrine elimination. Our results imply that volatile anesthetics may reduce the elimination of drugs given in the perioperative period and that differences may exist among anesthetic agents.

Aminopyrine↗
PubMed1984

Side effects of antimotion sickness drugs.

The possible influence on operational proficiency of the side effects of the anti-motion sickness drugs was investigated using a computerized pursuit meter as the test device. The medications and doses tested were scopolamine (Hyoscine) 0.25 mg and 0.50 mg oral doses, promethazine (Phenergan) 25 mg oral and 25 mg I.M. doses. Combinations of promethazine 25 mg with 10 mg d-amphetamine (Dexadrine) oral were also used, as was a combination of promethazine 25 mg oral with promethazine 25 mg I.M. and 10 mg of oral d-amphetamine. The proficiency on the pursuit meter task was not significantly altered by 0.25 mg or 0.50 mg doses of scopolamine. The combination of promethazine 25 mg oral with 10 mg d-amphetamine did not produce a significant decrement of performance. When promethazine 25 mg was given as an oral or I.M. dose without amphetamine the decrement of performance was significant and was approximately equivalent to an alcohol blood level of 25-50 mg% (one-two drinks). When a combination of promethazine 25 mg oral plus promethazine 25 mg I.M. with 10 mg d-amphetamine was tested, the error scores were significantly lower than with the oral or I.M. dose of promethazine. This combination also produced an error score significantly higher than placebo level. Promethazine by the I.M. route was slowly absorbed and 6 of the 10 subjects reported drowsiness at 6 h post injection.

Adolescent↗
PubMed1984

The Ambulatory Sentinel Practice Network: purpose, methods, and policies.

The Ambulatory Sentinel Practice Network (ASPN) is a network of primary health care practices across the United States and Canada offering (1) a laboratory for the study of populations under the care of primary care providers, and (2) surveillance of primary care problems and services. This paper reports the methods and policies developed and used by ASPN to conduct studies and describes the initial sentinel practices.

Adolescent↗