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Biomedical subjects

G N Kenny

Publications and source records attributed to G N Kenny.

At least 19 recordsLinked to original sources
PubMed1992

Postoperative analgesia using a computerised infusion of alfentanil following aortic bifurcation graft surgery.

A Psion microcomputer controlled infusion system for alfentanil was assessed for the provision of post-operative analgesia in 14 patients who had undergone aortic bifurcation graft surgery. The system employed a pharmacokinetic model working in real time to deliver any selected target plasma concentration of alfentanil. The alfentanil infusion system was used for a mean time of 39 hours and for 96% of this time, patients were scored as having no pain or only mild pain. Severe pain was recorded for only 0.05% of the study time. The use of a pharmacokinetic delivery system may offer a convenient and simple method of providing postoperative analgesia with alfentanil.

Adult↗
PubMed1992

A portable target controlled propofol infusion system.

A portable target controlled infusion system for propofol has been developed based on a Psion hand-held microcomputer and the Ohmeda 9000 syringe pump. The system uses a pharmacokinetic model which describes the distribution and elimination of propofol to achieve and maintain any selected target blood concentration. Target blood concentrations of 1 micrograms/ml, 3 micrograms/ml and 5 micrograms/ml were selected in laboratory trials and the cumulative volumes delivered by the Psion system each minute were compared with the theoretical output calculated by the pharmacokinetic model. The results obtained showed that the computer system delivered volumes which were always within 2% of the theoretical values. This system offers a convenient and simple method of maintaining anaesthesia using propofol.

Anesthesia, Intravenous↗
PubMed1992

Sedation after cardiac bypass surgery: comparison of propofol and midazolam in the presence of a computerized closed loop arterial pressure controller.

Forty patients who had undergone coronary artery graft surgery and who required vasodilator therapy for postoperative hypertension were given infusions of either propofol (2,6,di-isopropylphenol) or midazolam, together with an infusion of morphine for analgesia while ventilation was controlled artificially. Sodium nitroprusside was administered to patients in both groups using a computer-controlled closed loop system. Both agents produced good quality of sedation. Overall times to spontaneous ventilation and tracheal extubation were shorter in the propofol group, but this was not statistically significant. Ease of control of arterial pressure was satisfactory clinically with both agents, although propofol appeared to be associated with a statistically greater incidence of hypotension.

Adult↗
PubMed1992

Efficacy of orally administered ondansetron in the prevention of postoperative nausea and vomiting: a dose ranging study.

In a placebo-controlled, double-blind study, we have compared the efficacy of ondansetron 16 mg, 8 mg and 1 mg administered 8-hourly for prevention of postoperative nausea and vomiting. We studied 995 patients undergoing major gynaecological surgery; 982 were included in the analysis. Study medication was administered 1 h before induction of anaesthesia and second and third doses were given 8 and 16 h after the first. The treatment groups were similar for patient characteristics, surgical procedures, anaesthetics administered and opioids given. The frequency of nausea was 75%, 70%, 56% and 55% after placebo and ondansetron 1 mg, 8 mg and 16 mg, respectively; the corresponding frequencies of vomiting were 60%, 55%, 37% and 37%. Ondansetron 8 mg was as effective as 16 mg and both resulted in significant reductions in nausea and vomiting compared with placebo and ondansetron 1 mg (P less than 0.001).

Administration, Oral↗
PubMed1992

Effects of ketorolac trometamol on renal function.

We have compared the renal effects of ketorolac trometamol 10 mg administered 4-hourly by intermittent i.m. injection or by continuous i.m. infusion with placebo in a double-blind study in 67 patients who had undergone upper abdominal surgery. Ketorolac was supplemented during the 48-h postoperative study period with bolus doses of morphine delivered by a patient controlled analgesia system. The only significant effect of ketorolac on renal function compared with patients who received placebo was reduced excretion of potassium. The overall changes caused by surgery alone were of much greater magnitude. Bleeding time was increased with ketorolac, but there were no adverse events related to this.

Adult↗
PubMed1992

Ketorolac trometamol for postoperative analgesia after orthopaedic surgery.

We have compared the postoperative morphine requirements and analgesic efficacy of four doses of i.m. ketorolac 30 mg administered 6-hourly with placebo in a double-blind study of patients undergoing major or minor orthopaedic surgery. During the 24-h postoperative study period which began at the end of surgery, patients were prescribed i.m. morphine 10 mg as required 2-hourly and assessments were made of pain at 4 and 24 h. After major surgery, the median morphine consumption over 24 h was 10 mg in patients who received ketorolac, compared with 30 mg in those who received placebo (P = 0.008). Visual analogue pain scores and verbal pain assessments were better than placebo at 4 h (P = 0.028 and P = 0.008, respectively), but were not statistically different between the groups at 24 h. Overall assessment of pain was similar in both groups who had undergone major surgery. In the minor surgery groups, median morphine consumption was 0 mg in patients who received ketorolac, compared with 10 mg in those given placebo (ns). Visual analogue pain scores at 24 h after surgery were significantly less in patients who had received ketorolac compared with placebo (P = 0.046) and the overall assessment of pain relief was better in the ketorolac group (P = 0.0007). Mandatory administration of ketorolac appeared to be of benefit in both major and minor orthopaedic surgery, although the principal effects were reduction in requirement for supplementary morphine for major surgery and better overall analgesia for minor surgery.

Adolescent↗
PubMed1992

Pharmacodynamic stability of a mixture of propofol and alfentanil.

We studied 40 patients undergoing body surface surgery in a double-blind manner to compare the pharmacodynamic stability of either mixed or separate infusions of propofol and alfentanil. No differences were found between the two groups in respiratory or cardiovascular variables during operation, or in requirements for analgesia after operation. The power of the study to determine a difference of 10 mm Hg in mean arterial pressure with a probability of 0.05 was 0.82 and for a difference of 1 kPa in end-tidal carbon dioxide partial pressure 0.89. We conclude that propofol and alfentanil may be administered by infusion from a single syringe without diminished or delayed effect of the opioid during anaesthesia and the first 4 h after operation.

Adult↗
PubMed1992

Evaluation of closed loop control of arterial pressure during hypotensive anaesthesia for local resection of intraocular melanoma.

We have studied 20 patients undergoing local resection of intraocular melanoma during hypotensive anaesthesia, allocated randomly to receive either manual control by an experienced anaesthetist or closed-loop computer control of an infusion of a 5:1 mixture of trimetaphan camsylate (TMP) and sodium nitroprusside (SNP). There were no significant differences in the smallest systolic and diastolic arterial pressures obtained, heart rate or infusion requirements between the two groups, but the duration of both the infusion and the operation were significantly longer in the computer-controlled group (P < 0.05). The quality of control of arterial pressure was assessed by the percentage of time spent at pressures greater and less than the prescribed target values, and was satisfactory in both groups during the critical period of profound hypotension. We conclude that the computer-controlled infusion performed satisfactorily during profound hypotension compared with an experienced anaesthetist.

Adult↗
PubMed1992

Induction of anaesthesia with propofol using a target-controlled infusion system.

Sixty patients premedicated with temazepam were allocated randomly to receive an infusion of propofol designed to achieve and maintain a target blood concentration of 3, 4 or 5 micrograms.ml-1. Induction time was measured from the start of infusion to loss of verbal contact. The success rate of inducing anaesthesia within 3 min of achieving the target concentration was 40% when the predicted target concentration was 3 micrograms.ml-1, 75% when the predicted target was 4 micrograms.ml-1 and 90% when the target was 5 micrograms.ml-1. There were no significant differences between the three groups for time to loss of verbal contact in patients who were induced successfully within 3 min. There were significant reductions in arterial pressure 3 min after achieving the target concentrations within the groups but not between them. The frequency of apnoea and pain on injection was small in all groups. Selecting a target concentration of 5 microgram.ml-1 would successfully induce anaesthesia in the majority of patients premedicated with temazepam without major haemodynamic or respiratory side effects.

Adolescent↗
PubMed1992

A comparison of laryngeal mask airway with tracheal tube for intra-ocular ophthalmic surgery.

The use of the laryngeal mask was compared with tracheal intubation in 30 patients who underwent intra-ocular ophthalmic surgery and who received intravenous anaesthesia with propofol. Changes in intra-ocular pressure, heart rate and mean arterial pressure after the insertion of the laryngeal mask airway or the tracheal tube were not significantly different. However, at the end of the procedure, a significantly higher percentage of patients with a tracheal tube coughed, reacted to head movement and suffered breath-holding. In addition, significantly more patients in this group complained of a sore throat (p less than 0.05). During intravenous propofol anaesthesia, the laryngeal mask airway does not offer any advantage over tracheal intubation in the control of intra-ocular pressure for intra-ocular ophthalmic surgery. However, there were fewer complications immediately following surgery in the laryngeal mask group.

Anesthesia, Intravenous↗
PubMed1992

Potential renal, haematological and allergic adverse effects associated with nonsteroidal anti-inflammatory drugs.

The major benefits of the perioperative administration of nonsteroidal anti-inflammatory drugs (NSAIDs) are related to the ability of these agents to provide analgesia without cardiovascular or respiratory depression. However, there are several possible adverse effects of NSAIDs. All NSAIDs reduce the synthesis of prostaglandins by the kidneys, but their administration in the perioperative period appears to have little potential for renal toxicity when adequate hydration is maintained and renal function is not dependent on renal prostaglandins. However, NSAIDs may cause impairment of renal function in patients with conditions such as hypovolaemia, congestive cardiac failure, or hepatic cirrhosis, since renal function in these patients may be dependent on the vascular effects of prostaglandins. Platelet aggregation is inhibited by the administration of NSAIDs, and most studies of their haematological effects report that NSAIDs are associated with an increase in bleeding times. In patients with normal haemostatic function before NSAID administration, almost all indices of coagulation remain within the normal range after NSAID treatment. Most studies of perioperative blood loss have reported no significant difference between the effects of NSAIDs and placebo in this regard. The incidence of major allergic reactions in the general population appears to be small with NSAIDs. Overall, NSAIDs appear to be safe and well tolerated drugs with a valuable role to play in the treatment of postoperative pain.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1991

Comparison of the Finapres and direct arterial pressure monitoring during profound hypotensive anaesthesia.

The Finapres was compared with direct intraarterial pressure monitoring in 10 patients undergoing local resection of choroidal melanoma, an operation that requires a period of profound hypotension. Good agreement was recorded for systolic arterial pressure and heart rate over a range of pressures. However, agreement of mean and diastolic pressures was poor, with the Finapres tending to overestimate these values. In cases requiring profound hypotension, direct arterial pressure monitoring remains the method of choice.

Anesthesia, General↗
PubMed1991

Pharmacokinetic model driven infusion of propofol in children.

A computer controlled infusion device for propofol was used to induce and maintain general anaesthesia in 20 children undergoing minor surgical procedures. The device was programmed with an adult pharmacokinetic model for propofol. During and after anaesthesia, blood samples were taken for measurement of propofol concentrations and it was found that the values obtained were systematically overpredicted by the delivery system algorithm. New pharmacokinetic microconstants were derived from our data which reflected more accurately the elimination and distribution of propofol in a prospective study involving another 10 children.

Adult↗
PubMed1991

Double-blind comparison of the morphine sparing effect of continuous and intermittent i.m. administration of ketorolac.

The morphine sparing effect of ketorolac 10 mg administered 4-hourly by intermittent i.m. injection was compared with a continuous i.m. infusion in a double-blind, placebo-controlled trial in patients undergoing upper abdominal surgery. During the 48-h postoperative period, each patient was provided with a patient-controlled analgesia (PCA) system which delivered bolus doses of morphine and administered the intermittent i.m. doses automatically via a computer controlled pump. In the first 24 h after surgery, there was a significant reduction in morphine demanded by both groups receiving ketorolac compared with placebo. Patients who received a continuous infusion of ketorolac after abdominal surgery required a median dose of morphine by PCA which was 49% less than controls. In the second 24 h and over the entire 48 h of the study, patients in the continuous group required significantly less morphine than those in the placebo group. The intermittent group used less than the placebo group, but this was not significant.

Abdomen↗
PubMed1991

Examination of cardiorespiratory changes during upper gastrointestinal endoscopy. Comparison of monitoring of arterial oxygen saturation, arterial pressure and the electrocardiogram.

Critical events including hypoxaemia, arrhythmias and myocardial ischaemia may occur more frequently during endoscopic procedures than during anaesthesia. A study was undertaken to assess the cardiovascular changes and to evaluate suitable monitoring techniques to detect critical events during sedation and endoscopy. Twenty patients scheduled to undergo a prolonged endoscopic procedure which required deep sedation were studied. Continuous recordings of electrocardiogram, heart rate and arterial oxygen saturation were made and arterial pressure was recorded at one-minute intervals. The study commenced immediately before administration of sedatives, continued for the duration of the examination and for one hour following the examination. Oxygen saturation decreased in all patients during the examination to a mean of 82.9% (SD 11.9), and remained below baseline for the duration of the examination and into the recovery period. Statistically significant increases and reductions of systolic arterial pressure and rate-pressure product were found during the procedures compared with baseline values recorded before administration of sedatives. Sixteen of the 20 patients developed tachycardia during the examination. Ten patients developed ectopic foci which were supraventricular, ventricular or both in origin. Electrocardiogram changes resolved during the recovery period. Myocardial ischaemia was assessed by S-T segment depression and a significant correlation was found between S-T segment depression and hypoxaemia, although the magnitude of the S-T depression was small and may not have been detected clinically. No correlation was found between S-T segment depression and arterial pressure, heart rate or rate-pressure product.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗