Peri-operative administration of rectal diclofenac sodium. The effect on renal function in patients undergoing minor orthopaedic surgery.

In a randomized, double-blind study, we administered placebo and diclofenac sodium 100 mg suppositories 1 h pre-operatively and on the first post-operative morning to 22 adult patients undergoing minor orthopaedic surgery. A standardized post-operative intravenous fluid regimen was instituted until oral fluids were tolerated. Renal function was assessed pre-operatively, and on the first and second post-operative days by the measurement of urine output, creatinine, urea, sodium, potassium and NAG (N-acetyl-b-D-glucosaminidase) levels and serum creatinine, urea, sodium and potassium concentrations. On the first post-operative day, the diclofenac group demonstrated a reduced urinary sodium excretion. On the second post-operative day, a reduced urinary NAG/creatinine ratio was observed in the diclofenac group when compared to placebo. We conclude that peri-operative administration of diclofenac causes changes in renal function consistent with prostaglandin inhibition on the first post-operative day but had no lasting adverse effects in this group of patients. Our results reinforce the need for caution when administering this drug in the context of pre-existing renal impairment.

The effect of premedication on oxygen saturation during the post-premedication period in 20 Chinese children undergoing elective surgery.

Peri-operative continuous pulse oximetric data were studied in healthy Chinese children randomly allocated to receive either pethidine 1 mg kg-1 and atropine 0.02 mg kg-1 intramuscularly 90 min prior to surgery (n = 10), or midazolam 0.5 mg kg-1 and atropine 0.02 mg kg-1 orally, 120 min before surgery (n = 10). Data were collected during the night before surgery, after premedication and for 8 h post-operatively. The pulse oximeter (Nellcor N-200E) output was retrospectively evaluated using Satmaster, a computer programme which permits storage, retrieval, signal evaluation and compilation of oximetric data. There was no significant difference in the frequency, duration, or magnitude ofdesaturation episodes recorded during the post-premedication period compared to the desaturation episodes which occurred in the same child during normal sleep, on the night before surgery. Furthermore, there was no significant difference in the desaturation data between the two premedicant regimens. No child recorded a genuine desaturation less than 80% for longer than 15 s at any time during the study. Neither regimen significantly depressed saturation in otherwise healthy children presenting for minor surgical procedures.

Effect of extradural diamorphine on analgesia after caesarean section under subarachnoid block.

We have examined the efficacy, duration of action and side effects of extradural diamorphine alone and in combination with 1:200,000 adrenaline in a randomized, double-blind controlled study of 45 patients who underwent Caesarean section under spinal anaesthesia. Saline 10 ml, diamorphine 2.5 mg in saline 10 ml or diamorphine 2.5 mg in 1:200,000 adrenaline 10 ml were administered via the extradural route at delivery of the baby. Both diamorphine and diamorphine with adrenaline provided significantly prolonged analgesia compared with control (mean time to next analgesia (95% confidence interval) 17.3 h (12.0, 22.1 h), 15.9 h (10.6, 21.1 h), 5.7 h (1.5, 9.9 h), respectively) (P < 0.01). The addition of adrenaline increased the quality of analgesia 8 h after operation, but had no effect on the total amount of i.m. morphine administered during the first 24 h. The incidence of side effects was similar in all groups.

The Finapres 2300e finger cuff. The influence of cuff application on the accuracy of blood pressure measurement.

Blood pressure measurements associated with malapplication of a finger cuff were compared with contemporaneous intra-arterial pressure data in seven volunteers to determine the influence of cuff application on the accuracy of the Finapres 2300e. Systolic readings in all cuff positions differed from arterial line data by more than the recommended standard and tight and loose cuff applications under and over-read respectively, in all subjects. The results show the Finapres to be sensitive to small degrees of finger cuff malapplication which contribute to the bias on direct arterial comparison and limit the reliability of the instrument in clinical practice.

Pharmacokinetics of flumazenil and midazolam.

We have studied simultaneously the pharmacokinetics of flumazenil and midazolam in 12 healthy Chinese children, aged 5-9 yr, undergoing circumcision. Two hours before operation each patient received midazolam 0.5 mg kg-1 orally for premedication and 0.5 mg kg-1 i.v. during induction. Six minutes after cessation of anaesthesia, a bolus of flumazenil 10 micrograms kg-1 was given i.v., followed by an infusion of flumazenil at 5 micrograms kg-1 min-1 which was maintained until the child could identify himself. Midazolam data were consistent with a three-compartment model with a mean (SD) elimination half-life of 107 (30) min, total body clearance of 15.4 (3.2) ml min-1 kg-1 and apparent volume of distribution at steady state of 1.9 (0.6) litre kg-1. Flumazenil data were best interpreted by a monoexponential function, with a mean terminal elimination half-life of 35.3 (13.8) min, a total plasma clearance of 20.6 (6.9) ml min-1 kg-1 and apparent volume of distribution at steady state of 1.0 (0.2) litre kg-1. No unchanged midazolam was detected in the 24-h urine sample, but 5.8-13.8% of the flumazenil dose was recovered unchanged. At the time of self identification, 4.5 (1.4) min after flumazenil administration, the mean plasma concentrations of midazolam and flumazenil were 163.1 (43.7) and 29.9 (16.1) ng ml-1, respectively.

Are they getting enough? Meeting the oxygen therapy needs of postoperative patients.

Many patients require oxygen therapy as part of their postoperative care. A study to assess whether patients were actually given the supplementary oxygen prescribed showed many received only intermittent therapy. Placing more emphasis on oxygen therapy in nurse education would do much to improve its use in practice.

An evaluation of prolonged oximetric data acquisition.

Data derived from pulse oximetry has inherent limitations, one of which is artifactual desaturation caused by patient movement. Perioperative patterns of oxygen desaturation were studied for a mean duration of 67 hours in eight young patients following corrective spinal surgery. Pulse oximetry data were relayed to a computer using Satmaster, a program which permits storage, retrieval, signal evaluation and statistical analysis of oximetry data. Desaturation episodes were mild, of short duration and their infrequent occurrence was not increased during intravenous morphine infusion. Retrospective identification of contemporaneous artifactual changes in signal amplitude permitted the removal of artifactual desaturations from our statistical data analysis. This decreased the average time desaturated from 5.4% (220 minutes) to 4.2% (162 minutes) of the monitored period representing a 25% reduction in absolute incidence and a 35% reduction in episodic incidence of desaturation. Acquired data should be validated and inferences drawn from non-validated data must be assessed with caution.

Video surveillance of oxygen administration by mask in postoperative patients.

Patients may not receive prescribed oxygen because the oxygen face mask becomes displaced. Using video, we have observed the position of the face mask in 20 postoperative patients and recorded the timing and the events associated with mask displacement. Correct placement of the mask was confirmed at the start of the 8-h study period from 22:00 on the first night after operation. The mask remained on continuously and positioned correctly in only one patient. In the other 19 patients, it was removed 64 times (range 1-10 times per patient). The mask was removed 45 times for nursing tasks such as mouth care and temperature measurement and these represented 70% of the total number of times that the mask was not in position. Other reasons for removal were vomiting, retching and removal by the patient. The mask remained off a median time of 6 min 55 s per episode (range 46 s to 7 h 46 min 57 s) and per patient a median of 1 h 6 min 48 s (range 1 min to 7 h 46 min 57 s). Mask removal resulted in an average decrease in oxygen saturation of 4%. Oxygen by mask at 4 litre min-1 maintained an average saturation > or = 95% in most, but not all, of the patients.

The upgraded Finapres 2300e. A clinical evaluation of a continuous noninvasive blood pressure monitor.

Measurements from the upgraded Finapres 2300e continuous noninvasive blood pressure monitor, the Finapres 2300 and Colin oscillometric noninvasive blood pressure monitor were compared with invasive arterial line blood pressure readings. Fifteen young Chinese patients undergoing elective spinal surgery of more than 2 h duration had contemporaneous blood pressure measurements digitally recorded every minute. Data were analysed using methods described by Bland and Altman to assess agreement of noninvasive devices with an arterial line. Results showed that although the Finapres 2300e was significantly more accurate than the Finapres 2300 and Colin noninvasive blood pressure monitors it could not be recommended as a substitute for continuous arterial line blood pressure monitoring. Both Finapres devices demonstrated reductions in accuracy related to time (drift) and over-read diastolic and mean pressures by 5-8 mmHg throughout the range of mean arterial line pressures (bias). The Colin was consistently less accurate than the Finapress monitors and performed worst at low mean arterial line pressures.

Intramuscular injections through indwelling cannulae.

A study was performed to establish the feasibility of an indwelling intramuscular cannula for the administration of post-operative analgesic and anti-emetic medication. One-hundred cannulae were inserted for periods up to 7 days (mean = 2.4). A mean of five and maximum of 15 injections were made through each cannula with a maximum volume in any patient of 29 ml. On 18 occasions cannulae were removed for minor complications; no serious complications were seen. This technique may be useful for administration of intramuscular analgesic and anti-emetic medications in the post-operative period.