Modification of local anaeshetics by the addition of agents such as sodium bicarbonate has been practised for a long time. The article by Gaggero e t al. ~ studies the effect of adding sodium bicarbonate to lidocaine 2% when used in epidural anaesthesia for Caesarian section. Modification of a local anaesthetic is usually carried out to either try to speed the onset of blockade, i.e., by adding sodium bicarbonate or prolonging the duration of block, i.e., by adding epinephrine. As yet, there is no local anaesthetic available that combines reliable quick onset (in 10 minutes or less for an epidural block) with a length of action of several hours. The theory behind the practice of adding sodium bicarbonate is that most local anaesthetics, while being weak bases with pKa's varying from 7.7 to 8.90, are supplied in solutions that are acidic. 2 This is done to improve the stability of the local anaesthetic preparations. Local anaesthetics when used in nerve blockade must cross the perineural sheath and nerve membrane. These structures are only permeable to the drug when in its non-ionised form. 3 Thus when injected in an acidic preparation the local anaesthetic will exist mostly in the ionised form and therefore will probably achieve nerve block slower than if a solution is used with a pH that more closely approximates the pKa and contains more of the non-ionised drug. A typical preparation of lidocaine 2% is supplied at a pH of 6.4 and bupivacaine 0.5% is at a pH of 6.0. 2 At these pH's the proportion of the non-ionlsed form is less than 5%. If the pH of lidocaine is raised to 7.0 (pKa is 7.6) the proportion of the non-ionised drug increases to 11%. 3 The pKa of bupivacaine is 8.0 and therefore even less non-ionlsed drug is available in the supplied preparation. A number of studies have reported comparisons between alkalinized and plain (unalkalinized) preparations of local anaesthetics. ~,3-J0 It is difficult to compare the results of these studies as either the local anaesthetic solutions differ, i.e., both bupivacaine and lidocaine have been studied or differing blocks were studied, i.e., epidural for analgesia in labour or Caesarean section and

New iv induction anaestheticsThe history of intravenous (iv) anaesthetic induction agents almost mirrors that of the 50 years of the Canadian Anaesthetists' Society.~ While other agents were available before its introduction, thiopentone has been used for slightly more than 50 yr. 2 In fact, Since its introduction, up until the present day, thiopentone has been considered as the standard against which other/v induction agents have to be judged.3 Over the past 50 yr many agents have been used to induce anaesthesia intravenously; however, only a few can be considered "true"/v induction agents.An ideal /v induction agent should include the following properties.4 1 Predictable, rapid /v induction (one arm-to-brain circulation).2 Lack of cardiovascular and respiratory depression.3 Rapid awakening (recovery).4 Minimal side-effects.5 Minimal anaphylactic reactions.

ABSTRACT Objective To examine the effect of epidural analgesia on the progress and outcome of spontaneous labour in women with a singleton breech presentation at term ( 3=37 weeks). Design A retrospective study. Setting Data Bank, Aberdeen Maternity Hospital. Subjects 643 women (273 primiparae and 370 multiparae) with a singleton breech presentation and spontaneous onset of labour at term. Outcome measures Duration of labour; augmentation of labour with oxytocin infusion; caesarean section rates. Results Epidural analgesia was associated with a significantly increased need for augmentation of labour with oxytocin infusion ( P<0.001 ) and longer duration of labour ( P<0.001 ), irrespective of parity. Comparing women who had epidural analgesia with those who did not, there was no significant difference in caesarean section rates in the first stage of labour in primiparae (odds ratio 1.79; 95% CI0.88–3.63) or multiparae (odds ratio 0.97; 95% CI 0.48–1.96). Epidural analgesia was associated with a significantly increased likelihood of caesarean section in the second stage of labour, both in primiparae (odds ratio 5.43; 95% CI 2.46–11.95) and multiparae (odds ratio 5.37; 95% CI 2.07–13.87). The increased likelihood of caesarean section in the second stage in primiparae with epidurals was independent of the extent of cervical dilatation (<3 cm or ≥3 cm) on admission. However, in multiparae with epidurals, the difference in second stage caesarean section rate was significant only when initial cervical dilatation was <3 cm (odds ratio 3.65; 95% CI 1.14–11.65). Conclusion Epidural analgesia was associated with longer duration of labour, increased need for augmentation of labour with oxytocin infusion and a significantly higher caesarean section rate in the second stage of labour.

This study compares a continuous infusion technique with intermittent “top-up” doses using 0.25 per cent bupivacaine for epidural analgesia for labour and delivery in healthy pritniparous patients. Sixty women were randomized into two groups, A (continuous) and B (intermittent). Twenty-eight patients in Group A and 29 in Group B completed the study, We compared the groups with regard to satisfaction with pain relief for both labour and delivery as measured by a Visual Analogue Scale on five occasions during and after parturition. There was no difference between groups at any of the five stages. The difference in pain scores before the epidural and after the epidural was significant for both groups (p < 0.001). The incidence of missed segments, degrees of motor block, height of sensory block, length of labour and fetal outcome were similar in both groups. Plasma bupivacaine levels were measured in six patients in each group. Mothers in Group A received more drug than those in Group B (p < 0.01) but plasma bupivacaine levels remained low in the mother and the umbilical cord samples in the sub-set from this group. More women in Group A required outlet forceps (p < 0.05) whereas mid-forceps and Caesarean section rates were similar in the two groups. Fewer mothers in the infusion group had spontaneous vaginal delivery. We conclude that infusion techniques are as effective as intermittent top-up epidurals and are well received by mothers in labour.

Preoperative cimetidine, ranitidine, or placebo were administered, orally or intravenously to 190 patients in a double-blind study. The volume and pH of gastric aspirate samples, obtained after tracheal intubation and before extubation, were measured. Both cimetidine and ranitidine produced higher mean pH levels and thus fewer patients "at risk" should gastric aspiration occur (pH less than or equal to 2.5) than did placebo. Intravenous ranitidine (in both 40- and 80-mg doses) produced fewer patients at risk in the event gastric aspiration should occur than did cimetidine, 300 mg, and the 80-mg dose produced a higher mean pH level. Oral ranitidine, 150 mg, produced a significantly higher mean pH level than did oral cimetidine, 300 mg, and tended to give fewer patients at risk. The volumes of gastric contents aspirated were similar following each of the drugs except that the volume was significantly less two hours following oral ranitidine, 150 mg, than after oral cimetidine, 300 mg.

Abstract: Plasma concentrations of minaxolone were measured in 15 female patients during and for up to 3 hours after a minaxolone and nitrous oxide anesthetic. Nine patients received a single dose and six patients two or three doses of minaxolone. Plasma minaxolone decay can be described by two‐compartment kinetics. Distribution is rapid, with a mean half‐life of 2.1 minutes, and the elimination half‐life is short (47 minutes). Plasma clearance is high (1.55 l./min). Plasma levels of minaxolone at recovery were similar in patients receiving both single and multiple doses, suggesting a valid relationship between plasma level and effect. It is suggested that minaxolone may be a suitable agent for administration by continuous infusion.