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Biomedical subjects

P Hutton

Publications and source records attributed to P Hutton.

At least 37 records · Page 2Linked to original sources
PubMed1991

Whole blood electrolyte assay using ChemPro 500. A comparison of assay performance with standard laboratory instruments.

The ChemPro 500 'near-the-patient' analyser, with ChemPro 'Ion Profile' sensor cards, was evaluated for the assay of pH, Ca2+, K+ and Na+ in whole blood samples from patients in the intensive care unit or during surgery for heart or major blood vessel disease, or for liver transplantation. Imprecisions estimated from replicate whole blood measurements were much greater for all four ions than even the least stringent of the generally accepted analytical goals, and much greater than those estimated using quality assurance materials. Comparisons of assayed values with those obtained using standard laboratory instruments showed significant constant and proportional biases. The performance of the ChemPro 500 with the Ion Profile cards gave us no confidence in recommending their use to anaesthetists and intensivists.

Biosensing Techniques↗
PubMed1991

Rate-dependent induction phenomena with propofol: implications for the relative potency of intravenous anesthetics.

To establish anesthesia with minimal respiratory and cardiovascular depression using propofol, the effects of varying the rate of delivery on anesthetic induction dose requirements and hemodynamic changes were studied in four groups of 20 patients each undergoing body surface surgery. All patients were premedicated with temazepam and received 1.5 micrograms/kg fentanyl 5 min before induction. Propofol was delivered at 50, 100, or 200 mg/min by the Ohmeda 9000 infusion pump (groups 1, 2, and 3, respectively) or by bolus of 2 mg/kg (group 4) until loss of verbal contact. Anesthesia was maintained thereafter with propofol infused at 6 mg.kg-1.h-1. Using slower infusion rates, induction took significantly longer (124, 92, 62, and 32 s in groups 1, 2, 3, and 4, respectively) and was achieved with significantly smaller doses of propofol (1.40, 1.96, 2.61, and 2.15 mg/kg in groups 1, 2, 3, and 4, respectively). Slow infusion (groups 1 and 2) caused less depression of systolic and diastolic blood pressure than rapid infusion (groups 3 and 4), but the differences were not statistically significant. Patients in groups 3 and 4 had significantly greater decreases in pulse rate and a greater incidence of apnea than did patients in group 1. There was no correlation between the size of the induction dose and subsequent maintenance requirements of propofol. The finding that the sleep dose of propofol is reduced at slower infusion rates has important practical and theoretical implications when considering the relative potencies of intravenous anesthetics.

Adult↗
PubMed1990

Factors modifying the use of anaesthetic drugs in the elderly.

The elderly are forming an ever greater proportion of our hospital population. The process of ageing produces a gradual erosion of all the body's margins of safety coupled with a decreasing ability to adapt. This has significant effects on the physiological responses to the surgical and pharmacological trespass encountered during anaesthesia. In addition elderly people often suffer from multiple pathology and polypharmacy, both of which play important roles in the selection of the optimal anaesthetic regimen.

Aged↗
PubMed1990

The Ohmeda 9000 syringe pump. The first of a new generation of syringe drivers.

The Ohmeda 9000 syringe pump was developed in response to the need for an infusion apparatus to administer intravenous anaesthetic agents. It incorporates a bolus facility for the rapid, controlled delivery of loading infusions, or incremental dosing over a background maintenance infusion, and may be interfaced with a controller for computer-driven infusions. The Ohmeda 9000 pump has undergone bench testing and detailed evaluation in clinical practice using a variety of syringe sizes and makes. It is capable of accurate delivery over a range of infusion rates provided the recommended manufacturers' syringes are used with the appropriate pump setting. The pump was easy to use and reliable in clinical research and routine clinical practice. It should find its niche as the first genuinely 'anaesthetist-friendly' infusion pump.

Anesthesia, Intravenous↗
PubMed1989

Tension pneumoperitoneum.

A 26-year-old woman developed the adult respiratory distress syndrome after a post-partum haemorrhage. After mechanical ventilation was started the signs of a tense and distended acute abdomen developed. The aspiration and subsequent analysis of copious intra-peritoneal gas confirmed the diagnosis of a tension pneumoperitoneum secondary to pulmonary barotrauma.

Abdomen, Acute↗
PubMed1989

Effect of diluting propofol on the incidence of pain on injection and venous sequelae.

The effect of diluting propofol in 5% dextrose on the incidence of i.v. injection pain was studied in 100 adult patients. Severe injection pain occurred in 32% (16 patients) who received undiluted propofol, compared with 10% (five patients) who received dilute propofol. We concluded that the dilution of propofol significantly reduced the incidence of severe pain during injection without increasing postoperative venous sequelae.

Adult↗
PubMed1989

Automatic arterial pressure regulation using isoflurane: comparison with manual control.

A self-tuning, closed-loop controller, based on the algorithm of Clarke and Gawthrop, was used to regulate the inspired concentration of isoflurane to reduce arterial pressure electively in 33 patients undergoing ENT surgery. The patients were allocated randomly to one of four groups and received differing doses of fentanyl and labetalol to vary the range of sensitivities to the hypotensive action of isoflurane. The performance of the controller was evaluated at two target arterial pressures (AP), by its response to simulated changes in AP and by a comparison with a further group of eight patients with manual control of AP. The controller's undershoot of AP (range 2.8 +/- 0.5-4.5 +/- 1.3 mm Hg) and % time spent within +/- 5 mm Hg of the target AP (range 83 +/- 3.4-89 +/- 2.2%) were acceptable and equalled the manual performance figures (range 3.3 +/- 0.8 mm Hg; 90 +/- 5%). The regulation of induced hypotension in all four groups was rapid, accurate, stable and reproducible.

Adolescent↗
PubMed1989

Cardiovascular responses to flumazenil-induced arousal after arterial surgery.

Patients who underwent peripheral arterial surgery had anaesthesia maintained with an infusion of midazolam. They were allowed either to recover spontaneously or to have the effects of midazolam reversed by flumazenil at the end of surgery. This study demonstrated that the cardiovascular responses to arousal using flumazenil are no different from those seen when the patient is allowed to recover in the normal way. This result has obvious advantages for clinical practice but the dangers of resedation must not be forgotten.

Anesthesia Recovery Period↗
PubMed1989

Gelling of urea-linked gelatin with fresh frozen plasma.

Urea-linked gelatin and succinylated gelatin were mixed with fresh frozen plasma and human albumin solutions in vitro, in varying concentrations and at different temperatures. Gelling was only seen in those mixtures that contained fresh frozen plasma and urea-linked gelatin. It occurred at both room temperature and 37 degrees C when the mixture contained more than 40% by volume of urea-linked gelatin. Further tests confirmed that this was the result of calcium ions in the urea-linked gelatin allowing coagulation to occur in the fresh frozen plasma.

Calcium Chloride↗
PubMed1989

A computer-controlled anaesthetic gas mixer.

The theory and construction of a prototype computer-controlled gas mixer and flow regulator are described. The device is capable of controlling and mixing flows of oxygen, nitrous oxide and air. The accuracy and repeatability of the device is very high under given conditions, and its performance is quantified. The flow rate and oxygen concentration are selected from a microcomputer and the control program is written in BASIC. Possible improvements to the system are discussed as are uses in both clinical and research work.

Air↗
PubMed1989

Comparison of potassium ISFETs with the Radiometer KNA1 and the Corning 902 ion selective electrode analysers for whole blood potassium ion estimation.

Evaluation of the performance of potassium ion sensitive field effect transistors (K+ ISFETs), developed by Thorn EMI in a form suitable for mass production and for incorporation in 'near the patient' analysers, showed only very small constant and proportional biases against the Radiometer KNA1 and the Corning 902 for whole blood potassium ion estimation. Between batch imprecision tests with whole blood showed the K+ ISFET was comparable in performance to the Corning 902 but inferior to the Radiometer KNA1. The evaluation demonstrated that ISFET manufacturing technology has now reached a stage of development at which ISFETs should be considered seriously for use in clinical chemical analysers.

Calibration↗
PubMed1988

Comparison of recovery after neuromuscular blockade by atracurium or pancuronium.

Thirty patients were randomly allocated to receive either atracurium or pancuronium for neuromuscular blockade during surgery. At the end of the operation residual paralysis was antagonized with neostigmine. Voluntary strength was assessed at intervals after the antagonism, by observing grip strength, maximum inspiratory and expiratory force, 5-s head lift and the presence or absence of double vision. Grip strength and maximum expiratory force recovered significantly more quickly in the atracurium group over the 2-h measurement period. Double vision was significantly more frequent at up to 1 h when pancuronium had been used. At no time was there any significant difference between the two groups in respect of the 5-s head lift or, after 30 min, in the measurement of inspiratory force.

Adolescent↗
PubMed1988

The Ohmeda Excel anaesthetic machine.

The Ohmeda Excel 410 anaesthetic machine is described. A report of its use on 100 patients and impressions of its innovations are given.

Anesthesia, Inhalation↗