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Biomedical subjects

H Owen

Publications and source records attributed to H Owen.

At least 19 recordsLinked to original sources
PubMed1992

Oxyhaemoglobin saturation following elective abdominal surgery in patients receiving continuous intravenous infusion or intramuscular morphine analgesia.

Oxygen saturation was continuously measured using computerised pulse oximetry for 8 h overnight pre-operatively and for the first 24 h postoperatively in 40 patients receiving intermittent intramuscular morphine or continuous infusion of morphine following elective upper abdominal surgery. The proportion of time with an oxygen saturation less than 94% was used as an index of desaturation. Patients receiving continuous infusion analgesia received a larger morphine dose and achieved better analgesia than the intramuscular group. Postoperatively, the duration of desaturation increased 10-fold over pre-operative values, 'intramuscular' patients spending 39.0% (SD, 37.0%) and 'continuous infusion' patients 40.0% (SD, 37.5%) of the time below 94% saturation. Although newer therapies (e.g. epidural analgesia and patient-controlled analgesia) are currently receiving greater attention, the sequelae of these more traditional analgesic techniques warrant further study.

Abdomen↗
PubMed1992

An automated system for testing the accuracy of patient-controlled analgesia devices.

A system was developed to test the accuracy of patient-controlled analgesia devices in situations simulating clinical use. Bolus requests are made automatically at predetermined intervals, and the infusate delivered is measured and recorded without the need for operator presence. To ensure clinical relevance, the bolus request times used in this study corresponded to a pattern typical of those requested by patients on the ward. Graseby, Abbott Provider 5500 and IVAC patient-controlled analgesia devices were tested and found to deliver reasonably accurately over a 24 h period. However, when an infusion was started in an unprimed system or after a period of no bolus requests in a bolus-only mode the Graseby and IVAC machines under-delivered. This system provides a means of testing patient-controlled analgesia devices operating in any delivery mode.

Analgesia, Patient-Controlled↗
PubMed1991

Assessment of antinociceptive drug effects in the presence of impaired motor performance.

The hot-plate (HP) and tail-flick (TF) tests are widely used to assess analgesic activity of drugs. These tests do not directly measure the intensity of the noxious stimulus perceived by the animal, but only the animal's response to it, and so may be affected by non-analgesic drugs. Sedatives and muscle relaxants, for example, may impair the ability to respond and hence be wrongly considered to have analgesic activity. We examined response of rats in the HP (55 degrees C, cutoff time 25 sec) and TF (cutoff time 5 sec) tests following administration of pentobarbitone, diazepam or pancuronium. These drugs all impaired motor performance as assessed by reduction in mean rotarod performance times to 6-32% of predrug values. However, HP and TF latencies were not appreciably prolonged. We also found that pancuronium did not alter effects of morphine on HP or TF latencies, despite reduction in rotarod performance to 38% of predrug values. Our results support the validity of HP and TF tests as analgesic assays even in the presence of substantial impairment of motor performance.

Analgesics↗
PubMed1991

Premedication: an audit.

A prospective study of routine premedication management was carried out at a large teaching hospital. Many patients received their premedication at times inappropriate for it to be effective. Several patients receiving regular medication had this suddenly stopped pre-operatively. Prolonged fasting occurred in both elective and emergency groups of patients. Benzodiazepines and opioids were prescribed most frequently and drying agents were used widely. Antacids, H2-blockers and agents to promote gastric emptying were used very little despite the potential of aspiration in many groups of patients. This audit of activity has revealed several areas of practice that can either be improved immediately or warrant detailed investigation.

Adolescent↗
PubMed1991

Peri-operative drug prescribing pattern and manufacturers' guidelines. An audit.

Many patients admitted for surgery are receiving regular drug therapy. Adverse effects may occur, either as a result of these drugs being stopped suddenly or because staff are unaware of significant interactions between certain drugs and anaesthetic agents or techniques. This study aimed to find out how regular drug medication is actually given in the peri-operative period. In addition, pharmaceutical companies were contacted and asked for information about the effects of sudden withdrawal of their products and potential interactions with anaesthetic agents. We found that many drugs were omitted peri-operatively with potentially significant effects. Pharmaceutical companies do not seem to appreciate the importance of this problem and not all of them give clear recommendations relevant to practising anaesthetists.

Anesthesia↗
PubMed1991

Assessment of a new infusion pump for epidural PCA.

The use of epidural fentanyl by patient-controlled analgesia (PCA) may be a useful method of providing high-quality postoperative analgesia on the general surgical ward. The successful use of this technique requires an infusion pump with specific characteristics. Three Provider 5500, newly-developed, battery-powered PCA pumps, were tested to determine their accuracy, threshold of occlusion alarm limits and stored volume characteristics. These measurements were repeated following the in-line addition of an 18 gauge epidural catheter and two 0.2 micron filters. Pumps delivered on average within 3% of stated infusion rates and within 3% of bolus dose size. Occlusion pressures generated were between 1200 and 1360 mmHg, while the mean stored volume was 0.12 ml. Accuracy of delivery was maintained at lower voltage inputs. Addition of the catheter failed to alter the accuracy of the pumps tested. Siphoning of fluid was possible on disconnection of cartridge from pump. This problem did not occur with the addition of an epidural catheter and filter. This device has features which make it suitable for the safe delivery of epidural PCA. Care, however, needs to be taken on changing cartridges to prevent accidental administration of a drug bolus to the patient.

Analgesia, Patient-Controlled↗
PubMed1991

The influence of rectal cisapride on morphine-induced gastric stasis.

The effect of a new formulation of the gastric prokinetic agent cispride on opioid-induced gastric stasis was investigated. Forty patients were randomly allocated to one of four therapies administered as premedication; group A, placebo suppositories only; group B, placebo suppositories and intramuscular morphine 10 mg; group C, rectal cisapride 30 mg and intramuscular morphine 10 mg and group D, rectal cisapride 60 mg and intramuscular morphine 10 mg. Gastric emptying was assessed from the small bowel absorption of paracetamol following oral absorption. The kinetics of the suppository formulation were determined from venous blood samples. Rectal cisapride in the two doses used did not prevent opioid-induced gastric stasis. This may reflect an inability of this formulation to produce adequate plasma concentrations.

Acetaminophen↗
PubMed1991

Patient-controlled analgesia: can it be made safer?

Patient-controlled analgesia (PCA) has been shown to provide superior pain relief when compared with standard therapy options for postoperative analgesia. If PCA is to be implemented widely in teaching, private and country hospitals, its effectiveness needs balanced with a high safety profile. This can be achieved by consideration of patient selection, comprehensive education of patients, medical and nursing staff and equipment familiarisation. Continuous clinical audit allows identification of problem areas along with monitoring analgesic efficacy.

Analgesia, Patient-Controlled↗
PubMed1991

Variation in the blood concentration/analgesic response relationship during patient-controlled analgesia with alfentanil.

The effect of supplementing postoperative patient-controlled analgesia (PCA) with a mandatory fixed-rate infusion was studied using alfentanil. Patients were assigned by lottery to receive alfentanil PCA with a bolus of 200 or 300 mcg or alfentanil PCA with a bolus of 100 or 200 mcg plus an infusion of 900 mcg/hr, such that ten patients received each treatment. Seven patients receiving PCA only, compared to two in the groups receiving infusion, were withdrawn due to inadequate pain relief (0.1 greater than P greater than 0.05). One patient receiving PCA only was withdrawn because of a low respiratory rate, whereas three patients receiving PCA plus infusion developed respiratory depression. Patients prescribed PCA plus infusion received significantly more alfentanil but did not describe less pain than patients prescribed PCA only. The blood alfentanil concentration immediately prior to demands was significantly higher in the PCA plus infusion groups. These results suggest that during PCA therapy the drug prescription influences the blood concentration associated with satisfactory analgesia.

Abdomen↗
PubMed1990

Differing effects of pethidine and morphine on human sphincter of Oddi motility.

The aim of this study was to evaluate the effects of morphine and pethidine on human sphincter of Oddi motility. The action of these opioids on the sphincter of Oddi was evaluated by means of intraoperative manometry in 36 patients undergoing elective cholecystectomy. Both opioids were given in intravenous cumulative equipotent doses up to a maximum of 10 micrograms/kg morphine or 100 micrograms/kg pethidine. At these doses, morphine increased the mean(s.d.) frequency of contractions from 2.4(1.0) to 7.9(1.6) (P less than 0.001); this effect was reduced by naloxone (0.04 mg bolus, P less than 0.05). Pethidine inhibited the frequency of contractions from 1.5(0.8) to 0.8(0.5) (P less than 0.05); this response was blocked by atropine (0.6 mg bolus, P less than 0.01). Pretreatment with atropine or naloxone reduced the frequency of contractions significantly (P less than 0.05). The results illustrate different responses to pethidine and morphine of the sphincter of Oddi, and provide a pharmacological explanation for the suitability of pethidine over morphine as the analgesic of choice in patients experiencing biliary pain.

Adult↗
PubMed1990

PCA or PAA?

Explore the source record for details and available documents.

Analgesics↗
PubMed1990

Variables of patient-controlled analgesia. 3: Test of an infusion-demand system using alfentanil.

Patient-controlled infusion-demand analgesia was studied using alfentanil. We were unable to identify an optimal dose and administration rate; doses required range from 100 to 900 micrograms alfentanil. The mean concentration of alfentanil in blood associated with return of pain (i.e. immediately before demand) was 58 ng/ml on day 1 and 37 ng/ml on day 2. This difference was despite similar drug consumption on both days.

Adolescent↗
PubMed1990

Variables of patient-controlled analgesia 4: the relevance of bolus dose size to supplement a background infusion.

A range of self-administered demand doses of morphine (0.4, 0.7 and 1.0 mg) were prescribed to supplement a fixed-rate infusion (1.5 mg/hour) for pain control after gynaecological surgery. The number of demand doses administered during the first 25 hours after surgery was not significantly influenced by size of demand dose. There was a significant linear trend to increasing amount of demanded morphine with increasing bolus size. These results cast doubt on the usefulness of the concept of a minimum effective analgesic concentration of morphine.

Adult↗
PubMed1990

Antireflux valves in patient-controlled analgesia.

Antireflux valves are widely used in conjunction with patient-controlled analgesia devices. It is important to appreciate the limitations and dangers of these systems. They can achieve a potential 'stored volume' if occluded and they may, as part of the administration set, retard fluid administration. Seven antireflux systems currently available were tested in conjunction with three patient-controlled analgesia pumps. The systems' volume, time to occlusion alarm and flow rates were measured. Results showed that the sets with low stored volumes were less efficient as administration sets. A potentially dangerous bolus could result after release of occlusion if sets with large stored volumes were used in conjunction with pumps that utilised concentrated solutions of opioid. This study has identified the ideal antireflux valve system.

Analgesia, Patient-Controlled↗
PubMed1990

Patients' expectations of patient-controlled analgesia.

Patient-controlled analgesia is an increasingly popular method of postoperative pain relief. However, patients often worry about new therapies. Eighty ASA 1 and 2 patients aged 18-65 years were asked to list the advantages and disadvantages of using patient-controlled analgesia. The most important advantage as perceived by patients was the reduced time spent by nurses in giving medication, but there was concern that direct personal contact would also be lessened. Preservation of self control, autonomy, rapid onset of analgesia, ability to titrate analgesia and lack of injections were seen as an advantage. Addiction and machine faults were seen as minimal problems. Preservation of patient-nurse contact is of great importance to ensure success of postoperative analgesia.

Adolescent↗
PubMed1990

Rate-controlled analgesia: a laboratory evaluation of a new infusion device.

We report an evaluation of the Bard Harvard Mini Infuser, one of a new generation of agent-specific intraoperative infusion pumps which are designed for use by the anaesthetist. This pump permits potent intravenous anaesthetic agents to be used in pharmacokinetically designed dosage regimens. The controls are calibrated directly in kg body weight and micrograms per minute rather than the usual settings of ml of solution per hour. The performance was assessed by measuring the volume delivered over given time intervals and all safety functions were tested at least three times. This device was found to be acceptably safe and accurate. Two points to note are that it must be purged every time before it is connected to the intravenous infusion and if an occlusion is suddenly relieved, the patient can receive an 'accidental bolus' of up to 1.18 ml of drug. The main advantage of this pump is that it uses undiluted drug direct from the ampoule and does not require any calculations or dilutions prior to use. However, this restricts its use to drugs with a concentration of 500 mcg/ml and in effect means that it is suitable mainly for infusion of alfentanil.

Anesthesia, Intravenous↗