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M R Nel

Publications and source records attributed to M R Nel.

12 recordsLinked to original sources
PubMed2004

Left lateral vs. supine, wedged position for development of block after combined spinal-epidural anaesthesia for Caesarean section.

This prospective, randomised controlled trial compared a spinal block developing in the left lateral position (LL), after sitting a combined spinal-epidural for Caesarean section with the woman sitting -- using intrathecal hyperbaric bupivacaine and fentanyl -- with a block developing in the supine, wedged position (SW). The median (IQR) block onset times for loss of cold sensation to T4 bilaterally for LL and SW women were 15 (13-19) and 12 (10.8-14) min, respectively (p = 0.004). Unilateral blocks did not occur in the left lateral group. There were no other significant differences between groups, except the median [range] 1-min Apgar scores, which were 9 [8-10] and 9 [6-9] in the LL and SW groups, respectively (p = 0.04). In summary, the LL position is associated with a relatively slower block onset, but produces a spinal block with similar characteristics to that obtained in the SW position.

Adult↗
PubMed2002

Auditory evoked response during propofol anaesthesia after pre-induction with midazolam.

BACKGROUND: In clinical use, midazolam reduces the dose requirement for propofol. We studied the effect of midazolam given before anaesthesia on the amount of propofol needed and the time taken, to achieve loss of consciousness (LOC) in 20 patients. METHODS: We compared the auditory evoked responses (AER) in these patients with those in a group of 20 patients who were not given midazolam. RESULTS: LOC, as defined by a loss of response to verbal command and eyelash reflex, occurred after 113 (95% CI, 99-131) s in the control group and 75 (56-101) s in the midazolam group (P < 0.05). In the control group 2.3 (2.0-2.6) mg kg-1 propofol caused LOC compared with 1.3 (1.1-1.5) mg kg-1 in the group pretreated with midazolam (P < 0.001). Pa amplitude decreased by 60% in the control group and by 54% in the midazolam group while Nb latency increased by 24% in the control group and by 32% in the midazolam group following LOC. These differences were not significant. CONCLUSIONS: We confirmed that coinduction of anaesthesia with midazolam and propofol reduces the requirement of propofol. We also demonstrated that the AER reflects anaesthetic depth rather than plasma concentrations of anaesthetic drugs.

Adult↗
PubMed2001

Maternal anti-factor Xa activity following subcutaneous unfractionated heparin after Caesarean section.

Unfractionated heparin is widely used for prophylaxis against venous thromboembolism after Caesarean section. We performed a survey of thromboprophylactic methods after elective Caesarean section in 50 maternity units in the United Kingdom. We found that a variety of regimens were used. Thirteen (26%) used subcutaneous unfractionated heparin at standard (non-pregnant) doses. We then studied anti-Xa activity in women following elective Caesarean section under regional anaesthesia. Initially, eight women were given 5000 U unfractionated heparin subcutaneously after surgery and anti-Xa activity was measured 1, 2, 3, 4, 5, 6, 8 and 10 h after administration. There was no detectable anti-Xa activity in any of the samples so the dose was increased to 7500 U in a further five women and a single anti-Xa assay performed at 3 h when peak activity should occur. Again, no activity was detected so the dose was increased to 10 000 U heparin in a final group of 10 women and anti-Xa activity measured at 0.5, 1, 1.5, 2, 3, 4, 5 and 6 h. Although there was some activity after 10 000 U heparin, the level was below that accepted for prophylaxis. If anti-Xa activity is an appropriate monitor of prophylactic unfractionated heparin, doses up to 10 000 U are inadequate. Since there is evidence that enoxaparin is effective at producing adequate prophylactic anti-Xa activity following Caesarean section, we suggest abandoning the use of unfractionated heparin in favour of enoxaparin for this purpose.

Adult↗
PubMed1998

Extradural anaesthesia for caesarean section in a patient with syringomyelia and Chiari type I anomaly.

We describe elective Caesarean section performed under extradural anaesthesia in a parturient with symptomatic syringomyelia and coexisting Chiari type I anomaly. Syringomyelia is reviewed and the anaesthetic implications of the condition discussed. Anaesthesia should be directed primarily at avoidance of increased intracranial pressure, which can cause sudden deterioration in these patients.

Adult↗
PubMed1997

An alternative method of nitrous oxide delivery into a minimal-flow circle breathing system.

We have sought to define a way in which nitrous oxide can be safely and universally used at minimal to low flows by utilising a circle system with a controlled leak provided by a standard gas analyser sampling line and a fresh gas supply of 50% nitrous oxide in oxygen, entering from a trunk interposed between the ventilator and the circle system. Although preliminary calculations suggested that this arrangement was likely to work, it was found that 13 of 23 patients studied prospectively developed an inspired oxygen fraction below 0.3. We conclude that, although this arrangement provides a new means of introducing nitrous oxide into the circle breathing system, it does not appear inherently safer or more convenient than the conventional route.

Anesthesia, Closed-Circuit↗
PubMed1997

New agents, the circle system and short procedures.

Sevoflurane, desflurane and isoflurane were compared using a circle system in 97 patients undergoing short surgical procedures. Using initial high flows, the time intervals to equilibration between inspired and end-expired agent concentrations were measured; equilibration was defined as FE/FI = 0.8. The mean (SD) times obtained for sevoflurane, desflurane and isoflurane were 8.2 (2.1) min, 3.8 (0.7) min and 19.7 (6.5) min, respectively. These times were significantly different from each other (p < 0.0001). After equilibration total flow were reduced to 500 ml.min-1; at these flows the initial decline in end-expired agent concentration was minimal with desflurane, intermediate with sevoflurane and greatest with isoflurane. Both desflurane and sevoflurane are appropriate for efficient use of the circle system during short anaesthetics.

Adult↗