Ropivacaine, a new long acting amide type local anaesthetic, was compared with bupivacaine in a randomized double-blind study. One hundred and ten patients undergoing extradural anaesthesia received a test dose of 3 ml of 1% lignocaine with adrenaline which was followed by 15 ml of one of five solutions: 0.5, 0.75 or 1.0% ropivacaine or 0.5 or 0.75% bupivacaine. There was little difference between the groups with respect to speed of onset or sensory block. The duration of analgesia was increased by increasing the concentration of both drugs, but this had minimal effect on onset time or extent of block. When the same concentration of each drug was administered, there were inconsistent differences in duration of sensory block, none of which was statistically significant. Increasing concentration of both drugs resulted in greater degree and longer duration of motor block. Ropivacaine produced a slower onset, shorter duration and less intense motor block than the same concentration of bupivacaine. The cardiovascular changes were similar in all groups.
Ninety-one patients were allocated randomly to three groups to receive 1% ropivacaine 10 ml, 0.5% ropivacaine 20 ml or 0.5% bupivacaine 20 ml extradurally. Intermittent sensory (pinprick) and motor (Bromage scale) assessments of the block produced were recorded, with an assessment of the quality of the block and the requirement for supplementary analgesia. There was little difference between the groups in frequency, onset, duration or spread of sensory block. However, the motor block produced by 0.5% ropivacaine was less intense and of shorter duration than that with bupivacaine. The block produced by the smaller volume of ropivacaine was less reliable clinically than the larger, more dilute, solution and more anaesthetic supplements were required in that group. Cardiovascular changes were similar in all three groups. The peak plasma concentration of ropivacaine was significantly greater and T1/2 significantly shorter than those of bupivacaine, although no patient showed any features of systemic toxicity. The systemic kinetics of ropivacaine were not influenced significantly by varying the concentration or volume administered.
We have compared the effects of extradural fentanyl and fentanyl plus adrenaline with adrenaline alone as adjuncts to extradural bupivacaine in patients undergoing elective Caesarean section. Forty-five patients were allocated randomly to receive 0.45% bupivacaine 20 ml with adrenaline 4.5 micrograms ml-1, fentanyl 4.5 micrograms ml-1 or adrenaline plus fentanyl (4.5 micrograms ml-1 of each) as supplements. The main outcome measures were time to bilateral analgesia of T6 or higher, need for intraoperative analgesic supplements, observer rating of intraoperative analgesia and patient assessment of analgesia using a 10-cm visual analogue scale. The time to onset of analgesia to T6 was reduced insignificantly by the fentanyl solutions compared with adrenaline only. The quality of analgesia as assessed by the need for analgesic supplements was superior for the patients given fentanyl. An observer rating of pain and visual analogue pain scoring by the patient also indicated superior analgesia with fentanyl supplementation. Two patients experienced respiratory depression after extradural fentanyl and were given naloxone. Two neonates were also given naloxone. Close supervision is therefore recommended in the early postoperative period when this technique is used.
The cardiorespiratory effects of a new nonopioid analgesic, ketorolac tromethamine, were compared with alfentanil as part of a balanced technique in which anaesthesia was maintained by a constant infusion of propofol. Twenty patients were allocated randomly to receive a single dose of either ketorolac 30 mg or alfentanil 0.5 mg. The study medication was given during the anaesthetic when the rate of ventilation had been stable (+/- 1 b.p.m.) for 5 min. Measurements of ventilatory rate, end-tidal carbon dioxide partial pressure, arterial oxygen saturation (SaO2), heart rate and systemic arterial pressure were made at 1-min intervals for 15 min following the test drug. Patients having alfentanil developed significant decreases in ventilatory rate, heart rate and mean arterial pressure. A significant increase in end-tidal carbon dioxide partial pressure occurred also. No changes occurred in any of the measured variables in the ketorolac group.
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