Systemic lidocaine and human somatosensoryevoked potentials during sufentanil-isoflurane anaesthesia

The effect of systemically administered lidocaine on somatosensory evoked potentials (SSEPs) during general anaesthesia has not been widely reported. Knowledge of the influence of anaesthetic agents on evoked potentials assists in interpreting evoked potential waveforms. Accordingly, we studied the behaviour of cortical and subcortical (recorded at the second cervical vertebra) SSEPs after administration of intravenous lidocaine (3 mg.kg-1 bolus followed by infusion at 4 mg.kg-1.hr-1) during a sufentanil-based anaesthetic regimen in 16 patients undergoing abdominal or orthopaedic surgery. When compared to awake baseline recordings, the sufentanil-nitrous oxide, low-dose isoflurane anaesthetic depressed N1 amplitude by approximately 40% and prolonged latency by 10%. Fifteen minutes after establishment of this anaesthetic, the amplitude and latency of N1 were 1.13 +/- 0.56 microV and 19.81 +/- 1.63 msec, respectively. Within five minutes of adding lidocaine, amplitude decreased further to 0.84 +/- 0.39 microV (P = 0.001), while latency was extended to 20.44 +/- 1.48 msec (P = 0.01). Lidocaine did not affect cervical amplitude and prolonged latency only minimally. Despite the observed effects on amplitude and latency, SSEP waveforms were preserved and interpretable. Plasma lidocaine levels obtained at 5, 20, and 40 minutes after lidocaine were 5.17 +/- 1.33, 3.76 +/- 1.14, and 3.66 +/- 0.9 micrograms.dl-1, respectively. Our results indicate that systemically administered lidocaine at therapeutic plasma levels acts synergistically with a sufentanil-based anaesthetic to depress the amplitude and prolong the latency of SSEPs.     

Intrathecal meperidine for elective Caesarean section: a comparison with lidocaine

The purpose of this study was to determine the efficacy of intrathecal meperidine in patients undergoing Caesarean section, and also to compare meperidine with heavy lidocaine. Fifty fall-term pregnant women, ASA physical status I or II, presenting for elective Caesarean section under spinal anaesthesia were randomly divided into two groups with 25 in each, to receive either intrathecal meperidine or lidocaine. All patients received premedication with oral ranitidine, 150 mg, the night before surgery, and again two hours before surgery. Patients in the meperidine group were also given metoclopramide iv 10 mg one hour before surgery. After iv 20 ml·kg^?1 Ringer’s lactate, patients were given either 5% meperidine 1 mg · kg^?1 or 5% heavy lidocaine 1.2 to 1.4 ml intrathecally. The sensory and motor blockades in all except two patients in each group who required sedation at the time of skin incision were adequate for surgery. None of the mothers suffered from any major side effects. The incidence of hypotension was higher in the lidocaine group than in meperidine group (P < 0.05). Pruritus and drowsiness were more common in meperidine group than in lidocaine group (P < 0.01). All the newborns in both groups cried immediately after birth and had an Apgar scope > 7. The mean duration of postoperative analgesia was six hours in the meperidine group and one hour in the lidocaine group (P < 0.01). Postoperative analgesia requirement was less in the meperidine than in the lidocaine group (P < 0.01). It is concluded that intrathecal 5% meperidine in a dose of 1 mg·kg^?1 is superior to 5% heavy lidocaine because of the prolonged postoperative analgesia. The commercial 5% solution of meperidine can be used, without addition, for this purpose.     

Disposition of propofol infusions for caesarean section

The disposition of propofol was studied in women undergoing elective Caesarean section. Indices of maternal recovery and neonatal assessment were correlated with venous concentrations of propofol. After induction of anaesthesia with propofol 2.0 mg.kg-1, ten patients received propofol 6 mg.kg-1.hr-1 with nitrous oxide 50 per cent in oxygen (low group) and nine were given propofol 9 mg.kg-1.hr-1 with oxygen 100 per cent (high group). Pharmacokinetic variables were similar between the groups. The mean +/- SD Vss = 2.38 +/- 1.16 L.kg-1, Cl = 39.2 +/- 9.75 ml.min-1.kg-1 and t1/2 beta = 126 +/- 68.7 min. At the time of delivery (8-16 min), the concentration of propofol ranged from 1.91-3.82 micrograms.ml-1 in the maternal vein (MV), 1.00-2.00 micrograms.ml-1 in the umbilical vein (UV) and 0.53-1.66 micrograms.ml-1 in the umbilical artery (UA). Neonates with high UV concentrations of propofol at delivery had lower neurologic and adaptive capacity scores 15 minutes later. The concentrations of propofol were similar between groups during the infusion but they declined at a faster rate in the low group postoperatively. Maternal recovery times did not depend on the total dose of propofol but the concentration of propofol at the time of eye opening was greater in the high group than the low group (1.74 +/- 0.51 vs 1.24 +/- 0.32 micrograms.ml-1, P less than 0.01). The rapid placental transfer of propofol during Caesarean section requires propofol infusions to be given cautiously, especially when induction to delivery times are long.     

Plasma lidocaine concentrations during continuous epidural infusion of lidocaine with and without epinephrine

Plasma lidocaine concentrations were measured over a five-hour period in 20 patients following continuous epidural infusion of lidocaine for surgical anaesthesia. Patients were divided into two groups: Group I received plain lidocaine; Group II received lidocaine with epinephrine. Patients initially received 10 ml followed by a constant infusion of 10 ml.hr-1 of two per cent lidocaine. The mean plasma concentrations of lidocaine were significantly higher for the first 40 min in Group I than in Group II. However, from one to five hours, there was no significant difference between the groups. These results demonstrate that the addition of epinephrine to lidocaine does not decrease the plasma concentration of lidocaine during continuous epidural infusion for long operations.     

pH adjustment of mepivacaine decreases the incidence of tourniquet pain during axillary brachial plexus anaesthesia

The effect of pH adjustment of mepivacaine on the incidence of tourniquet pain during axillary brachial plexus anaesthesia was studied. Thirty-nine patients scheduled for hand surgery, during which use of pneumatic tourniquet for longer than 60 min was planned, were randomized into two groups. Both received axillary brachial plexus block with 40 ml, 1.4% mepivacaine, 1:200,000 epinephrine. The study group had 4 ml sodium bicarbonate (1 mEq · ml^{? 1}) added (final pH 7.31), and the control group had 4 ml saline added (final pH 5.6). The incidence of tourniquet pain was determined from cases for which tourniquet inflation lasted longer than 60 min. Tourniquet; pain was defined as poorly localized and distinct from an inadequate axillary block by a blinded observer. More tourniquet pain occurred in the control group. The authors conclude that alkalinization of mepivacaine for axillary brachial plexus anaesthesia may be indicated in cases where use of pneumatic tourniquet for long periods is planned.     

A comparison of two doses of epidural fentanyl during Caesarean section

A prospective, randomized, double-blind study was performed to compare the analgesic efficacy and side effects of epidural fentanyl, 25 pg vs 50 pg, when used to supplement epidural anaesthesia for elective Caesarean section. Fifty ASA I and II patients were randomized into two groups: Group I (n =24) received 25 pg and Group II (n = 26) received 50 pg of epidural fentanyl after the epidural test dose. No differences between the two groups were found on any measures of intraoperative pain, nausea, drowsiness, respiratory depression, hypotension, pruritus and neonatal outcome. The low levels of pain experienced by patients indicates that doses higher than 50 μg of epidural fentanyl are usually unnecessary for optimal analgesia.     

Patient-controlled analgesia following caesarean section under general anaesthesia: a comparison of fentanyl with morphine

This prospective, randomised, double-blind study compared PCA fentanyl with PCA morphine for post-Caesarean section analgesia. Following a standardised general anaesthetic, 37 women were allocated to receive either fentanyl (n = 18) or morphine (n = 19). The PCA was commenced after the women had been made comfortable in the postanaesthetic recovery room with the appropriate opioid solution (mean dose required = fentanyl 375 μg or morphine 16 mg). Initial PCA settings were bolus 1 ml (fentanyl 25 μg or morphine 1 mg), lockout time ten minutes, and no background infusion. Both analgesic solutions provided effective analgesia for a mean of 37 hr with high levels of patient satisfaction, and there were no differences in VAS scores for pain and patient satisfaction, or for side effects (nausea, itch, and sleepiness) between fentanyl or morphine. However, more patients in the fentanyl group required supplementary boluses or alterations to the PCA settings (13/18 vs 4/19: P = 0.005), and one patient was removed from the study due to inadequate analgesia. We conclude that fentanyl is not recommended for routine PCA use following Caesarean section. Cette étude randomisée et à double aveugle compare la PCA au fentanyl avec la PCA à la morphine pour l’analgésie postcésarienne. Après une anesthésie générate standard, 37 femmes sont réparties pour recevoir soil du fentanyl (n = 18) soil de la morphine (n = 19). La PCA est debutée à la salle de réveil des que les patientes se sentent confortables sous une solution appropriée de morphinique (dose moyenne requise, fentanyl 375 μg ou morphine 16 mg). Le régime initial consiste en un bolus d’un ml (fentanyl 25 μg ou morphine 1 mg), un intervalle de sécurité de dix minutes, sans perfusion continue. Les deux solutions produisent une analgésie satisfaisante pour 37 h en moyenne avec un degré élevé de satisfaction pour la patiente, et on ne note pas de différence entre le fentanyl et la morphine pour l’évaluation de la douleur par EVA, le degré de satisfaction, et pour les effets secondaires (nausée, prurit et somnolence). Cependant, plus de patientes sous fentanyl ont eu besoin de bolus supplémentaires ou des modifications aux réglages de la PCA (13/18 vs 4/19; P = 0,005). Une patiente est exclue de l’étude pour raison d’insuffisance d’analgésie. En conclusion, nous ne recommandons pas la PCA au fentanyl après la césarienne.

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Presented at the 1992 meeting of the Society for Obstetric Anesthesia and Perinatology (SOAP) in Charleston, South Carolina, USA.     

Cutaneous ionto-phoretic application of condensed lidocaine

The purpose of this study was to determine whether iontophoretic application of high concentrations of lidocaine, with the same current, would produce cutaneous local anaesthesia rapidly enough for clinical practice. Twenty healthy volunteers, 17 male and three female, were selected for study. After fiveminute or ten-minute iontophoresis using lidocaine 4, 10, 20, 30, 50%, we assessed the response to pin prick with a 27-gauge sterile needle inserted to the depth of 2 mm at five random locations in the iontophoretically-stimulated area. Also, plasma lidocaine concentrations were measured in the venous blood samples which had been taken from three male subjects, at 3, 10, and 30 min after iontophoresis with lidocaine 50%. The pain score after five-minute iontophoresis was higher than that after ten-minute iontophoresis, using each concentration of lidocaine (P< 0.001), whereas the pain scores had no correlation with lidocaine concentration within five-minute and ten-minute iontophoresis groups, respectively (P: NS). On the other hand, plasma lidocaine concentration was <1.0 μg · ml^?1 in all samples. No side effects other than erythema were observed after iontophoresis using high concentrations of lidocaine up to 50%. These results showed that by increasing the lidocaine concentration of the applied solution up to 50%, the application time of iontophoresis cannot be reduced from ten to five minutes without losing analgesic effect, although iontophoresis itself can be performed with safety.     

Temporary back and leg pain after bupivacaine and morphine spinal anaesthesia

Transient neurological symptoms have been reported after hyperbaric lidocaine 5% spinal anaesthetics. We report a patient with neurogenic back and leg pain after uncomplicated bupivacaine and morphine spinal anaesthesia. A healthy 39-yr-old woman received 1.6 ml hyperbaric bupivacaine 0.75% and 250 μg morphine intrathecally. Two hours later, the patient experienced discomfort during suturing of the peritoneum and surgery was completed under general anaesthesia. Recovery was uncomplicated until 13 hr after intrathecal injection, when the patient complained of burning pain in her back extending to the front of the abdomen and similar pain in her thighs. Neurological consultation was obtained. Treatment was started with amitriptyline and the symptoms resolved slowly. Complete recovery occurred over three months. Further studies to assess symptoms after spinal anaesthesia are indicated.     

Comparison of propofol versus thiopentone with midazolam or lidocaine to facilitate laryngeal mask insertion

Purpose  

To assess the ease of insertion of laryngeal mask airway (LMA) comparing propofol with lidocaine or midazolam followed by thiopentone and compare the costs with each technique.     

Spinal anaesthesia for Caesarean section after Harrington instrumentation

A case is presented of a 33-yr-old parturient with Harrington fusion of her spine who received spinal anaesthesia with 15 mg hyperbaric bupivacaine for Caesarean delivery. Multiple attempts of needle insertion in both midline and paramedian at the L_3-4 interspace were unsuccessful, whereas the procedure was performed uneventfully at the midline of the L₅S₁ interspace. The anatomical considerations and difficulties in achieving reliable epidural anaesthesia after Harrington fusion are reviewed. Spinal anaesthesia performed at the L₅S₁ interspace may provide less technical difficulty and a more reliable result in such patients.     

Interpleural block: a new technique for regional anaesthesia during percutaneous nephrostomy and nephrolithotomy

Canadian Journal of Anesthesia/Journal canadien d'anesthésie - Interpleural block was used in four patients undergoing percutaneous nephrostomy, one of whom also underwent percutaneous...     

Clinical and pharmacokinetic aspects of the combination of meperidine and prilocaine for spinal anaesthesia

The aim of this study was to determine whether the addition of a small dose of prilocaine could augment the spinal block induced by meperidine and affect intrathecal meperidine pharmacokinetic behaviour. Spinal anaesthesia was performed in 60 men scheduled for endoscopic resection of a prostatic adenoma or bladder tumour under spinal anaesthesia. They were allocated randomly to receive either 1 mg.kg-1 meperidine (Group 1, n = 30), or 1 mg.kg-1 meperidine plus 0.5 mg.kg-1 prilocaine (Group 2, n = 30). Blood samples were collected prior to and for 24 hr after spinal injection in 24 patients (12 in each group). Plasma meperidine levels were assayed by gas chromatography. Complete motor block was achieved in all Group 2 patients, but was incomplete in seven of Group 1 (P less than 0.05). The onset of both motor and sensory blocks was shorter (P less than 0.01) in Group 2 and the duration was longer (P less than 0.05). Coadministration of prilocaine modifies meperidine pharmacokinetic behaviour. The area under curve was 48% greater (P less than 0.01) and Cmax was higher in Group 2 than in Group 1, 145.8 +/- 42.2 vs 107 +/- 20.5 ng.ml-1 (P less than 0.001). No evidence of respiratory depression was noted in any of the patients. Despite the increase in plasma meperidine concentrations, no side effects were observed. The plasma concentrations remained at one third to one sixth the levels reported to induce a respiratory depression. It is concluded that the addition of prilocaine to meperidine improves motor and sensory block during surgery and alters meperidine kinetics without producing major side effects.     

Obstetrical epidural anaesthesia in a rural Canadian hospital

Few rural hospitals offer obstetric epidural analgesia services and of those that do, there is a paucity of information about these anaesthetics. A retrospective review was conducted of all obstetrical epidurals from 1984–1988 in an 85-bed hospital in Saskatchewan to examine the indications, complications, and infant outcomes. During that period there were 1224 deliveries. From a total of 915 vaginal deliveries, 42 (4.6%) received an epidural. Caesarean sections numbered 309:183 (59.3%) were with epidural analgesia of which 69 were urgent and 114 elective. The overall complication rate was 23% with the most important being hypotension (12%), dural punctures (1.8%), in-adequate block requiring an intravenous supplement (4.0%) or a general anaesthetic (3.1%). Infant outcomes were favourable except for two unrelated intra-uterine deaths preceding labour.     

Uterine and umbilical blood flow velocity during epidural anaesthesia for Caesarean section

The purpose of this study was to use colour Doppler to determine the effect of epidural anaesthesia on the uterine and umbilical blood flow velocities. After determining the precision of the technique, Doppler insonation of the uterine and umbilical arteries was performed in consenting non-labouring patients requesting epidural anaesthesia for Caesarean section. Patients in Group I were normal and those in Group II were at high risk for uteroplacental blood flow abnormalities. The pulsatility indexes (PI) of both uterine and umbilical arteries were compared at the following times: control, after fluid and after anaesthesia using repeated measure analysis of variance. In Group I (n = 30) the PI increased from 0.72 to 0.82 in the left uterine artery and from 0.71 to 0.85 in the right uterine artery (P < 0.05). In Group II (n = 10) the PI increased from 0.67 to 0.85 in the left uterine artery (NS) and from 0.98 to 1.38 in the right uterine artery (P < 0.05). There was no change in the PI in the umbilical artery. We conclude that the PI of the uterine arteries increases after epidural anaesthesia with lidocaine, epinephrine and fentanyl but there is no change in the umbilical PI. While these changes do not appear to be clinically important in the low-risk population, further studies are required to determine the impact on fetuses at high risk for in utero hypoxaemia.     

Maternal death following epidural anaesthesia for Caesarean section delivery in a patient with unsuspected sepsis

Sepsis in the parturient may be difficult to recognize in light of the physiologial changes associated with pregnancy. The purposes of this report are to highlight the signs and symptoms which indicate an underlying septic process and the management of these patients in the peripartum period. This 32-yr-old GII PI woman with twin gestation presented at 36 wk in labour. Her temperature was 35.3° C, she was normotensive and had a normal white blood cell count. After epidural anaesthesia was administered for Caesarean section, she became apnoeic, pulseless and unresponsive. Despite aggressive cardiopulmonary resuscitation, neither she nor her twin babies survived. Post mortem blood work revealed a considerable left shift of her white blood count (>60% bands) and an onion gap acidosis. Autopsy revealed evidence of widespread Group A beta-haemolytic streptococcal sepsis. Diagnosis of sepsis in the parturient involves assessment of the patient’s temperature, WBC and differential and acid-base status. Evaluation of the intra-vascular volume must precede anaesthetic intervention. Epidural anaesthesia may be considered in the labouring and Caesarean section patient who has been fluid-resuscitated. Emergency operative delivery may result in cardiovascular compromise in the patient with severe sepsis.     

Wenckebach type heart block following spinal anaesthesia for Caesarean section

A case is described of complete heart block during spinal anaesthesia for Caesarean section in a fit 23 yr-old-woman. This developed shortly after the institution of the block, with the height of the block below T5 and in the absence of hypotension. The patient was resuscitated successfully with vagolytic and alpha-agonist drugs. A Wenckebach block persisted for a short period postoperatively. The importance of instituting monitoring before the beginning of anaesthesia and the immediate availability of atropine and alpha-agonists before the initiation of spinal anaesthesia is stressed.     

Comparison of perioperative mental function after general anaesthesia and spinal anaesthesia with intravenous sedation

This study compared the postoperative mental function in 44 elderly patients following general anaesthesia (GA) or spinal anaesthesia (SA) with sedation for transurethral resection of prostate. The Mini-Mental State (MMS) was done preoperatively and postoperatively at six hours, one day, three days, five days and one month. The geriatric mental status examination was performed preoperatively and one month after the anaesthetic. There was no significant intergroup difference in the MMS score in the preoperative, six hours, one day, three days, five days and 30 days postoperative scores between the GA and SA with sedation groups. A significant intragroup difference between preoperative and postoperative MMS score was detected in the GA group (P less than 0.02) and in the SA group with sedation (P less than 0.03). In the GA group, the significant decrease in MMS score occurred at 6 h postoperatively (P less than 0.002) whereas in the SA group with sedation, MMS score also decreased significantly at 6 h (P less than 0.005). In conclusion, there was no significant difference in perioperative mental function between the general and spinal anaesthetic groups when supplemental IV sedation was given. In both groups, perioperative mental function decreased significantly at 6 h postoperatively.     

A comparison of spinal and epidural anaesthesia for hip arthroplasty

Spinal and epidural anaesthesia were compared in 65 patients undergoing hip arthroplasty, with regard to the degree of sensory and motor blockade, cardiovascular effects, operating conditions, the dose of propofol required to produce satisfactory hypnosis, and complications. Epidural anaesthesia was successful in 30 patients using an initial dose of 15 ml of 0.5% bupivacaine, and spinal anaesthesia in 32 patients, using 4 ml 0.5% isobaric bupivacaine. The two techniques were similar with regard to the level of sensory blockade (T8), degree of hypotension and perioperative haemorrhage. Differences occurred in the degree of motor blockade (mean Bromage score of 1 in the spinal group vs 3.86 in the epidural group) (P less than 0.05), time to achieve maximal cephalad spread (13 min in the spinal group vs 21 min in the epidural group) (P less than 0.05) and the dose of propofol required to produce adequate hypnosis (1.95 mg.kg-1.hr-1 in the spinal group vs 2.89 mg.kg-1.hr-1 in the epidural group) (P less than 0.05). Only seven patients required urethral catheterization in this spinal group compared with 14 in the epidural group (P less than 0.05). Spinal anaesthesia also proved advantageous by providing better operating conditions for the surgeon, with a lower incidence of patient movement.     

Epidural sufentanil for post-Caesarean section analgesia: lack of benefit of epinephrine

Epidural sufentanil was administered to 57 women after Caesarean section, under epidural anaesthesia, to provide postoperative analgesia. Each patient received a 30 μg dose at the first complaint of pain and this dose was repeated when pain recurred. Epinephrine (1:200,000) was added to the local anaesthetic, sufentanil, both, or neither. The time of onset of analgesia, efficacy, duration of analgesia and the incidence of side-effects were recorded. This dose of epidural sufentanil provided satisfactory postoperative analgesia and no serious side-effects were observed. The onset of analgesia was rapid (4–6 min), but the duration of action was brief (4–5 hr). The addition of 1:200,000 epinephrine had no statistically significant influence on any of the measured variables. Pruritus occurred commonly but never required treatment. Drowsiness was experienced frequently and was felt by some patients to inhibit their interaction with their neonates. Respiratory depression, as defined by a respiratory rate less than 10 bpm, was not observed. A number of patients noted a transient period of euphoria 5–8 min after administration of the epidural sufentanil. The authors feet that epidural sufentanil provides satisfactory analgesia after Caesarean section, but the brief duration of action and the high incidence of drowsiness limit its acceptability for routine use in obstetric patients. Le sufentanil en injection epidurale fut administré à 57 femmes après césarienne pour l’analgésie postopératoire. Chaque patiente a recu 30 μg lors de la première douleur et cette dose fut répétée quand la douleur est revenue. L’épinéphrine (1:200,000) fut ajouté à l’anesthésie locale, le sufentanil, au deux, ou à aucun. Le temps d’installation d’analgésie, l’efficacité, la durée de l’analgésie et l’insuffisance des effets secondaires furent enregistrés. Cette dose de sufentanil en injection épidurale a fourni une analgésie postopératoire satisfaisante et aucun effet secondaire fut observé. Le début de l’analgésie fut rapide (4–6 min), mais la durée d’action fut brève (4–5 hre). L’addition de 1:200,000 épinéphrine n’a eu aucune influence statistiquement significative sur aucune des mesures éludiées. Le prurit fut le plus communément observé mais n’a jamais requis un traitement. La somnolence fut observée fréquemment et certaines patientes l’attachait en la diminution de leur interaction avec les nouveau-nés. La dépression respiratoire définie par une fréquence respiratoire inférieure à 10 resp/min ne fut pas observée. Un certain nombre de patientes out noté une période transitoire d’euphorie de cinq à huit minutes après l’administration de sufentanil en injection épidurale. Les auteurs pensent que le sufentanil en injection épidurale fournit une analgésie satisfaisante après une césarienne mais une durée d’action courte et la haute incidence de somnolence limitent son acceptabilité de routine pour les patientes en obstétrique.

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This study was supported by a grant from Janssen Pharmaceutica.