Search PubMed⌕ Search

Biomedical subjects

A B Baker

Publications and source records attributed to A B Baker.

At least 37 records · Page 2Linked to original sources
PubMed1998

Droperidol elimination after cardiopulmonary bypass surgery.

A high-dose (0.75 to 2.8 mg/kg) pharmacokinetic study of droperidol was undertaken in patients during the recovery phase after cardiac surgery involving hypothermic cardiopulmonary bypass (CPB). The elimination half-life of droperidol in these patients, determined from concentration-time data obtained after CPB, was significantly prolonged relative to previously reported mean values in younger surgical patients not undergoing CPB and receiving lower doses of the drug (0.05-0.20 mg/kg). On stratification of the patients by droperidol dose, there was an inverse correlation between the size of the dose and the elimination half-life of droperidol: mean half-life decreased as mean dose increased. This difference in elimination half-life was not related to the duration of the CPB procedure, or the total anesthetic time, both of which were not significantly different between the patient groups receiving the three different doses of droperidol. The magnitude or duration of hypothermia after CPB did not differ between the three patient groups. The differences in half-lives are more likely due to the clinical condition of the patients, such that the patients who received the higher doses of droperidol were also judged clinically to be less ill and thus eliminated droperidol more efficiently. This hypothesis, however, could not be supported due to the small number of patients studied. The results obtained in this study indicate that droperidol elimination is significantly prolonged after high-dose administration to elderly patients undergoing hypothermic CPB procedures during cardiac surgery.

Adjuvants, Anesthesia↗
PubMed1997

Intentional asystole during endoluminal thoracic aortic surgery without cardiopulmonary bypass.

We describe in three patients the use of adenosine to arrest the heart without cardiopulmonary bypass during endoluminal repair of thoracic aortic aneurysms. The pharmacology of adenosine, a purine nucleoside present in all cells, is reviewed briefly, with special reference to its use in causing transient asystole, which is required for successful surgical expansion of the graft stent in the thoracic aorta.

Adenosine↗
PubMed1997

Effects of budesonide and fluticasone on 24-hour plasma cortisol. A dose-response study.

Comparison of the risk-benefit profiles of different inhaled glucocorticoids has been limited by inadequate information about the dose-response relationships for efficacy relative to side effects. Fluticasone propionate (FP) is twice as effective as budesonide (BUD), but the potency ratio of FP:BUD with respect to suppression of cortisol production is unknown. The effects of 5 d of treatment with BUD (800, 1,600, and 3,200 micrograms/d via pMDI) and FP (750, 1,500, and 2,000 micrograms/d via pMDI) on integrated area under the curve of 24-h plasma cortisol profiles (AUC24 h) were compared in a randomized, placebo-controlled, seven-period crossover study in normal male volunteers (n = 28). Plasma cortisol concentrations were measured during the last 24 h of each treatment period. Each treatment (except BUD 800 micrograms) produced significant dose-dependent reductions in AUC24 h compared with placebo; e.g., percent reductions in AUC24 h were 23, 41, and 69% for the three doses of BUD, and, correspondingly, 46, 85, and 93% for the three doses of FP. Model-derived measurements of dose potency ratios showed that FP was 2.9 times more potent than BUD in reducing AUC24 h (95% CI, 2.5 to 3.5) and 3.1 times more potent in reducing 8:00 A.M. plasma cortisol (95% CI, 2.4 to 4.0). Thus, on a microgram-for-microgram notional dose basis, the systemic effects of a given dose of FP on AUC24 h cortisol were equivalent to the effects of three times the dose of BUD.

Administration, Topical↗
PubMed1997

Anaesthesia workforce in Australia and New Zealand.

A survey of anaesthetic workforce was undertaken in departments in Australia and New Zealand approved for specialist training by the Australian and New Zealand College of Anaesthetists. When compared to a previous survey 17 years before, the results showed that the number of anaesthetics administered rose, the number of operating theatres (OTs) remained the same, but the surgical beds were reduced. There was a small increase (20%) in full-time specialists with a number of vacancies in establishment. There was, however, a large increase (80%) in Visiting Medical Officer (VMO) sessions and a 40% increase in Registrar positions. At the same time there were very large increases in Recovery Romm nurses (125%) and Anaesthetic Assistants (100%). From this survey and other recent government workforce reports it is possible to derive certain workforce postulates--a specialist anaesthetist will on average anaesthetize approximately 1000 patients per annum, one in every nine people in the population will have an anaesthetic each year, and the working lifespan of a specialist anaesthetist is 30 years with 5% working half-time or less. All of this suggests that the correct Anaesthetists to Population Ratio (APR) should be reset to 1:8,500 for both Australia and New Zealand. The number of trainees required to supply a steady state replacement for this specialist workforce is also derived and the current number of training positions is shown to be in excess of these requirements. When the current shortfall in specialist anaesthetists is corrected there will need to be a gradual reduction (by approximately 40%) in the number of training positions to prevent an oversupply of anaesthetists. The factors which may potentially alter this forecast are addressed and include: change in the general population; ageing of the population; change in the average number of anaesthetics administered per anaesthetist per year; alteration in anaesthetists' working lifespan; change in the age distribution of anaesthetists; increased economic usage of operating theatres and changes in the number of College approved training positions.

Adult↗
PubMed1997

Retrospective review of 100 cases of endoluminal aortic stent-graft surgery from an anaesthetic perspective.

One hundred cases of endoluminal aortic stent surgery were retrospectively reviewed and analysed with respect to outcome. The overall mortality rate was consistent with standard rates for open surgical repair. One hundred per cent of patients who developed multiorgan failure died (7), as did 78% of those who developed acute renal failure (9), and 55% of those who had a serum creatinine rise greater than 100 mumol/l (9). Patients given mannitol had an increased incidence of a serum creatinine rise of greater than 100 mumol/l, at 16% versus 4% for those not given mannitol. Patients with documented intra- or postoperative anaemia (Hb < or = 80 g/l) had a mortality rate of 22% compared to 5% for non-anaemic patients. The mortality rate increased from 3% to 15% if the procedure took more than four hours. The anaesthetic requirements for this new type of surgery are outlined and discussed with respect to these results. The surgical technique is summarized.

Anesthesia, Epidural↗
PubMed1997

Assumptions and practice in clinical medical ethics.

An orderly scheme of action is proposed to allow for the practical solution of clinical ethical problems. This scheme depends on understanding and discussion, between patient and doctor, of the ethical assumptions involved in any dilemma. Instead of the more usual ethical principles, arguments are presented for six basic ethical assumptions (and their associated corollaries) in favour of Life, Autonomy, Beneficence, Equity, Truth, and Law. Because these assumptions are dependent on the different personal viewpoints of the people involved and not immutable principles, such ethical assumptions are able to be set in different hierachical orders on different occasions permitting in most cases a particular solution specific for that dilemma.

Altruism↗
PubMed1996

A sensitive assay for the simultaneous measurement of alfentanil and fentanyl in plasma.

A reversed-phase high-performance liquid chromatography method for the simultaneous determination of plasma concentrations of the narcotic analgesics alfentanil and fentanyl using papaverine hydrochloride as the internal standard is presented. Chromatographic separations were achieved with an Econosphere CN, 5 microns, 25 cm x 4.6 mm i.d. column and the effluent was monitored at 195 nm. The assay was linear over the clinically relevant plasma range of 2-2000 ng ml-1 for alfentanil and 2-100 ng ml-1 for fentanyl and has the sensitivity and specificity necessary to determine plasma concentrations of these compounds. Inter- and intra-day precision (RSD) for both compounds did not exceed 10% in these ranges. The assay procedure was utilized for pharmacokinetic studies of plasma concentrations in subjects receiving alfentanil and fentanyl during and after cardiac surgery. This will allow better elucidation of pharmacokinetic variables in this populace.

Alfentanil↗
PubMed1996

Determination of droperidol in plasma by liquid chromatography.

A reversed-phase high performance liquid chromatographic method is described for the determination of droperidol concentrations in plasma. Following extraction, separation of droperidol and the internal standard flurazepam was achieved with a Spherisorb Nitrile, 5 microns, S5CN 250 mm x 4.6 mm column at 200 nm. The mobile phase was phosphate buffer (0.05 M, pH 2.4), acetonitrile and ethanol (65:20:15, v/v/v). The assay was rapid, sensitive and linear over the range 2-4000 ng ml-1. Precision of the assay expressed as the intra- and inter-day relative standard deviations (%RSD) did not exceed 10%. Flunitrazepam, midazolam and nitrazepam were also resolved with this technique and did not interfere with droperidol or flurazepam. Resolution of all five compounds was complete in less than 6 min. The assay was used to study the pharmacokinetics of high dose droperidol infusions during and after cardiac surgery.

Adjuvants, Anesthesia↗
PubMed1996

Nitrous oxide and the rate of gas uptake from an unventilated lung in dogs.

We have studied the effect of FIO2 of a nitrous oxide-oxygen mixture on the rate of gas uptake from an unventilated lung. Nine anaesthetized dogs were studied, each breathing four nitrous oxide-oxygen mixtures (FIO2 0.3, 0.5, 0.75 and 1.0) in random order. A double-lumen endobronchial tube separated lung ventilation. Both lungs were given the nitrous oxide-oxygen mixture for an equilibration period. Then the right lung was connected to a spirometer containing the same gas, and gas uptake measured. In every dog, gas uptake was faster with an FIO2 of 0.5 or 0.75 than with an FIO2 of 1.0. When breathing a nitrous oxide-oxygen mixture with FIO2 > 0.3, the rate of gas uptake from the unventilated lung was faster than with 100% oxygen.

Anesthetics, Inhalation↗
PubMed1996

Effectiveness of preoperative analgesics on postoperative dental pain: a study.

Patients undergoing extractions of third molar teeth under general anesthesia were given a placebo, diclofenac (a nonsteroidal anti-inflammatory drug) 100 mg, or methadone (an opiate) 10 mg 60 to 90 min prior to surgery, and their pain scores and postoperative medication requirements were measured for 3 days. All patients received local anesthetic blocks and analgesic drugs during the perioperative period. There were no significant differences between the three groups in the pain scores and medication requirements during the period of study. It was concluded that preoperative use of nonsteroidal anti-inflammatory drugs and opiates may not offer a preemptive analgesic effect in patients who have had adequate analgesia during the surgery. Continued use of analgesic drugs during the postoperative period is perhaps more useful for this purpose. There appears to be a higher incidence of vomiting following opiates (methadone), precluding its clinical use in day-care patients.

Adult↗
PubMed1995

Effects of inspired gas composition during anaesthesia for abdominal hysterectomy on postoperative lung volumes.

We have studied 51 patients who were allocated randomly and prospectively to receive either 100% oxygen (n = 16), 70% nitrous oxide in oxygen (n = 18) or 30% oxygen in nitrogen (n = 17) as the inspired gas during anaesthesia for abdominal hysterectomy. Lung volumes were measured before and after surgery. TLC, VC, FVC and FEV1 but not RV or FRC were reduced after surgery. There were no significant differences between the three treatment groups in any of the lung volumes measured. We conclude that absorption atelectasis during anaesthesia is not the main cause of perioperative changes in lung volume after abdominal hysterectomy. Any effect of the inspired gas is likely to be of limited clinical significance.

Adult↗
PubMed1995

Influence of inspired nitrogen concentration during anaesthesia for coronary artery bypass grafting on postoperative atelectasis.

Pulmonary collapse is a common problem after coronary artery bypass graft surgery (CABG). If absorption atelectasis during anaesthesia is an important mechanism in the genesis of pulmonary collapse after CABG, the addition of nitrogen to the inspired gas during anaesthesia should reduce the amount of postoperative collapse. We studied 30 patients who were allocated randomly and prospectively to receive either 100% oxygen or an oxygen-air mixture as the inspired gas during anaesthesia for CABG. Lung volumes, PaO2, and an x-ray atelectasis score were measured before and after surgery to assess the degree of atelectasis. There were no significant differences between the two treatment groups in any of these measurements.

Adult↗
PubMed1995

What is the role of absorption atelectasis in the genesis of perioperative pulmonary collapse?

During anaesthesia the combination of breathing at low lung volume, the administration of nitrous oxide and high inspired oxygen concentrations produces conditions that favour absorption atelectasis. Measures such as adding nitrogen to the inspired mixture and avoiding high inspired oxygen concentrations would reduce the amount of perioperative atelectasis if gas absorption was important in the genesis of perioperative pulmonary collapse. Experimental results demonstrate that these measures do not protect against atelectasis. This indicates that absorption atelectasis does not play a significant role in the genesis of perioperative pulmonary collapse. Compression atelectasis may be the underlying mechanism.

Absorption↗