Minimum local anaesthetic dose (MLAD) of intrathecal levobupivacaine and ropivacaine for Caesarean section*

A Study to Evaluate Intrathecal 1% Chloroprocaine and 0.5% Levobupivacaine in Perianal Surgeries: A Prospective Randomized Study

Background:

With increasing focus on outpatient care, there has been an increased demand for short-acting spinal anesthetics, facilitating early recovery and mobilization of the patient.

Aims:

The aim of the study was to compare 1% chloroprocaine, characterized by short latency and short duration with 0.5% levobupivacaine, which has shown to preserve motor function at low concentrations, with recovery from motor block as the primary objective and recovery from sensory block and hemodynamic stability as secondary objectives.

Settings and Design:

A prospective study to evaluate newer isobaric chloroprocaine and levobupivacaine intrathecally in a cohort of patients using randomization and double blinding.

Materials and Methods:

Sixty American Society of Anesthesiologist physical status Classes I and II patients undergoing perianal surgeries were randomly divided into Group C (n = 30) receiving intrathecal 1% chloroprocaine 3 mL and Group L (n = 30) receiving 0.5% levobupivacaine 1.5 mL. Patients were assessed for sensory and motor block characteristics, hemodynamic changes, period of analgesia, time for ambulation, and urination.

Statistical Analysis:

Qualitative data were analyzed using Chi-square test and quantitative data using Independent t-test.

Results:

There was no significant difference in highest sensory level, onset of motor block, maximum Bromage scale achieved, and hemodynamic changes between the two groups. There was a significant difference in mean Time for Maximum Bromage scale, Time for Sensory regression (Lumbar-L₁), Duration of Motor Block (Group C 50.7 ± 5.7 min and Group L 181 ± 27.8 min), Time for rescue Analgesia, Time for 1^st void, and Time for ambulation (Group C 88.3 ± 9.1 min and Group L₂ 06.7 ± 27.2 min) between chloroprocaine and levobupivacaine group. The above duration was shorter in chloroprocaine group than in levobupivacaine group.

Conclusion:

Thus, chloroprocaine provides good surgical anesthesia and early motor recovery than levobupivacaine and is well suited for day care surgeries.

Randomised Control Trial Comparing Plain Levobupivacaine and Ropivacaine with Hyperbaric Bupivacaine in Caesarean Deliveries

Objective

The study compared spinal block characteristics of equipotent doses of plain 0.5% levobupivacaine, plain 0.75% ropivacaine and hyperbaric 0.5% bupivacaine for elective caesarean (CS) delivery.

Methods

A total of 100 parturient women undergoing elective CS under spinal anaesthesia were enrolled for the study. The parturients were randomly assigned to receive one of the following in a subarachnoid block: hyperbaric 0.5% bupivacaine 10 mg (group B), plain 0.5% levobupivacaine 10 mg (group L), or plain 0.5% ropivacaine 15 mg (group R).

Results

Motor block duration [groups B, LB, R: 143.78 (30.43) minutes, 139.31 (33.38) minutes, 137.32 (27.39) minutes, respectively; P=0.80], sensory block duration [groups B, LB, R: 122.87 (34.93) minutes, 113.03 (39.24) minutes, 125.58 (24.93) minutes, respectively; p=0.30] and first analgesic request time [groups B, LB, R: 136.87 (28.70) minutes, 133.59 (27.30) minutes, 144.19 (32.09) minutes, respectively; p=0.35] were statistically comparable. The groups were statistically comparable for sensory block onset time [T6 block; groups B, LB, R: 4.62 (2.80) minutes, 4.93 (2.63) minutes, 5.73 (3.00) minutes, respectively; p=0.29] but motor block onset time was statistically prolonged for group R as compared to group B [Bromage 3 block; group B, LB, R: 5.93 (3.41) minutes, 9.00 (4.00) minutes, 10.16 (5.66) minutes, respectively; p=0.001]. No statistically significant differences were seen in sensory and motor block recovery times, haemodynamic parameters or side-effects.

Conclusion

The anaesthesia from a spinal block with 10 mg plain levobupivacaine or 15 mg plain ropivacaine is comparable to the anaesthetic effect of 10 mg hyperbaric bupivacaine in elective caesarean deliveries.

Relationship Between Body Mass Index and Spread of Spinal Anesthsia in Pregnant Women: A Randomized Controlled Trial

BACKGROUND The effect of body mass index (BMI) on the spread of spinal anesthesia is not completely clear. The aim of this study was to determine the dose requirements of ropivacaine and the incidence of hypotension in pregnant women with different BMIs during cesarean delivery. MATERIAL AND METHODS In this double-blind study, 405 women undergoing elective cesarean delivery were allocated to group S (BMI <25), group M (25 ≤BMI <30), or group L (BMI ≥30). Women in each group were further assigned to receive 7, 8, 9, 10, 11, 12, 13, 14, or 15 mg of spinal ropivacaine. RESULTS The ED50 and ED95 values of ropivacaine were 9.487 mg and 13.239 mg in Group S, 9.984 mg and 13.737 mg in Group M, and 9.067 mg and 12.819 mg in Group L. There were no significant differences among the 3 groups (p=0.915). Group L had a higher incidence of hypotension and a greater change in MAP after spinal anesthesia compared to the other 2 groups, and also required more doses of ephedrine than the other 2 groups when a dose of 15 mg ropivacaine was used. The incidence of hypotension had a positive correlation with the dose of ropivacaine (OR=1.453, p<0.001) and gestational age (OR=1.894, p<0.001). CONCLUSIONS Spinal ropivacaine dose requirements were similar in the normal BMI range. However, higher doses of spinal ropivacaine were associated with an increased incidence and severity of hypotension in obese patients compared with that in non-obese patients.

Body height and the spread of spinal anaesthesia for caesarean section: a prospective controlled trial

BACKGROUND

No conclusive evidence exists on the effect of patient height on the spread of spinal anaesthesia. Our aim was to measure the ED₅₀ and ED₉₅ values of intrathecal ropivacaine in taller and shorter patients, and thus investigate the hypothesis that the spinal dose requirement in shorter patients is lower than that in taller patients undergoing caesarean section.

METHODS

In this study, 270 pregnant women were assigned to the taller (Group T) or shorter group (Group S) based on their heights. Subjects in both groups were further randomly assigned to one of nine subgroups based on the dosage of intrathecal isobaric ropivacaine to be administered (7, 8, 9, 10, 11, 12, 13, 14 or 15 mg respectively).

RESULTS

The ED₅₀ and ED₉₅ values of ropivacaine were 9.24 mg and 13.36 mg in Group S, and 10.11 mg and 14.63 mg in Group T, with no inter-group difference (P = 0.886). There was a significant inter-group difference in the incidence of hypotension and the changes in mean arterial pressure after spinal anaesthesia using 15 mg ropivacaine. The dose of ephedrine administered in Group S was higher than that in Group T when 15 mg ropivacaine was administered (P = 0.031).

CONCLUSION

The taller and shorter patients did not respond differently to modest intrathecal doses of ropivacaine. However, a larger dose of ropivacaine was associated with an increased incidence of hypotension in shorter patients compared to that in taller patients.

Pencil-point needle bevel direction influences ED50 of isobaric ropivacaine with fentanyl in spinal anesthesia for cesarean delivery: a prospective, double-blind sequential allocation study

BACKGROUND

There is little evidence on the influence of bevel direction of a pencil-point needle on the median effective dose (ED50) of isobaric ropivacaine and fentanyl in spinal anesthesia for cesarean delivery.

METHODS

In this prospective, double-blind, sequential allocation study, 82 parturients scheduled for elective cesarean delivery under combined spinal-epidural anesthesia were included. We sought to determine the median effective dose of intrathecal 0.75% isobaric ropivacaine plus fentanyl 15μg with two different bevel directions of a 26-gauge Whitacre needle using up-down sequential allocation. Parturients were randomly allocated to either Group Ce (needle aperture oriented in a cephalad direction) or Group Ca (aperture directed caudally). The initial dose was 0.75% ropivacaine 11.25mg plus fentanyl 15μg in both groups. Each dose was classified as effective if, after 15min and during the next 60min, there was inability to appreciate pin-prick as sharp at T4, a visual analogue pain score <2 and no requirement for an epidural rescue bolus.

RESULTS

Eighty patients were included in the analysis. The ED50 in group Ca was significantly higher (13.09mg, 95% CI 12.19-14.00) than in group Ce (10.10mg, 95% CI 9.54-10.65, P <0.001).

CONCLUSION

The orientation of the distal aperture of a 26-gauge Whitacre needle during induction of spinal anesthesia for cesarean delivery influences the ED50 of 0.75% ropivacaine.

Comparison of intrathecal levobupivacaine combined with sufentanil, fentanyl, or placebo for elective caesarean section: a prospective, randomized, double-blind, controlled study

Background

The addition of opioids to local anesthetics contributes to the quality of spinal anesthesia and postoperative analgesia.

Objective

In our prospective, randomized, double-blind, controlled study, our aim was to compare the effect of low-dose sufentanil plus levobupivacaine or a fentanyl plus levobupivacaine mixture on anesthesia quality, block characteristics, newborn and mother well-being, surgeon satisfaction, and duration of postoperative analgesia.

Methods

Ninety-three patients were randomized into 3 groups (n = 31). Patients in Group C received 0.5% levobupivacaine (2.2 ± 0.2 mL), Group S received 2.5 µg sufentanil plus 0.5% levobupivacaine (2.2 ± 0.2 mL), and Group F received 10 µg fentanyl plus 0.5% levobupivacaine (2.2 ± 0.2 mL) intrathecally completed to a volume of 3 mL with the addition of saline in all groups. Patients’ demographics, sensory and motor block characteristics, hemodynamics, Apgar scores, umbilical blood gas values, maternal side effects, surgeon satisfaction score, time to first analgesia requirement, and additional analgesic use within 24 hours were recorded.

Results

In Group S and Group F, target levels of sensory and motor block were achieved more rapidly (P < 0.001). The hemodynamic values were lower (P < 0.05), and the duration of sensory blockade and the time of first analgesic requirement were longer (P < 0.001) in Group S. Additional analgesic requirement during first 24-hour period was lowest in Group S, and highest in Group C (P < 0.001). Apgar scores and umbilical blood gas samples were similar between groups. Postoperative pruritus was more frequent in Group S (P < 0.001) and surgeon satisfaction score was significantly lower in Group C (P = 0.003).

Conclusions

We suggest that the addition of sufentanil and fentanyl to intrathecal levobupivacaine during caesarean section surgery is more effective than the administration of levobupivacaine alone. The addition of sufentanil to levobupivacaine allowed rapid onset time for sensory and motor block levels. It also extended the duration of postoperative analgesia and led to a decrease in total analgesic requirement. ClinicalTrials.gov identifier: NCT01858090.

Clinical characteristics of spinal levobupivacaine: hyperbaric compared with isobaric solution

We performed a prospective, double-blinded study in 20 patients undergoing gynecologic surgery with lower abdominal incision, to investigate characteristics of intrathecal hyperbaric levobupivacaine compared with isobaric levobupivacaine. We randomly assigned them to receive 3 mL of either isobaric or hyperbaric 0.42% levobupivacaine intrathecally. We found that hyperbaric levobupivacaine, compared with isobaric levobupivacaine, spread faster to T10 level (2.8 ± 1.1 versus 6.6 ± 4.7 minutes, P = 0.039), reached higher sensory block levels at 5 and 15 minutes after injection (T8 versus L1, P = 0.011, and T4 versus T7, P = 0.027, resp.), and had a higher peak level (T4 versus T8, P = 0.040). Isobaric levobupivacaine caused a wider range of peak levels (L1 to C8) compared with hyperbaric form (T7 to T2). The level of T4 or higher reached 90% in the hyperbaric group compared with 20% in the isobaric group (P = 0.005). Our results suggest that hyperbaric levobupivacaine was more predictable for sensory block level and more effective for surgical procedures with lower abdominal approach. Hyperbaric levobupivacaine seems to be suitable, but the optimal dosage needs further investigation.

Update on local anesthetics: focus on levobupivacaine

In recent years levobupivacaine, the pure S (−)-enantiomer of bupivacaine, emerged as a safer alternative for regional anesthesia than its racemic parent. It demonstrated less affinity and strength of depressant effects onto myocardial and central nervous vital centers in pharmacodynamic studies, and a superior pharmacokinetic profile. Clinically, levobupivacaine is well tolerated in a variety of regional anesthesia techniques both after bolus administration and continuous postoperative infusion. Reports of toxicity with levobupivacaine are scarce and occasional toxic symptoms are usually reversible with minimal treatment with no fatal outcome. Yet, levobupivacaine has not entirely replaced bupivacaine in clinical practice. In anesthesia and analgesia practice, levobupivacaine and bupivacaine produce comparable surgical sensory block with similar adverse side effects, and equal labor pain control with comparable maternal and fetal outcome. The equipotency of the two drugs has been recently questioned, prompting clinicians to increase the dose of levobupivacaine in an attempt to ensure adequate anesthesia and analgesia and offsetting, therefore, the advantages of less motor block with levobupivacaine. In this review we aim to discuss the pharmacological essentials of the safer profile of levobupivacaine, and analyze the evidence regarding the current clinical indications.

Low-dose ropivacaine or levobupivacaine walking spinal anesthesia in ambulatory inguinal herniorrhaphy

PURPOSE

The purpose of our study was to compare the equipotent doses of ropivacaine and levobupivacaine for walk-out criteria and the characteristics of spinal anesthesia in inguinal herniorrhaphy surgery.

METHODS

Combined spinal-epidural anesthesia was performed. Adult patients were randomly allocated to receive 5 mg 0.5% ropivacaine plus 25 μg fentanyl (group RF, n = 25) or 3.75 mg 0.75% levobupivacaine plus 25 μg fentanyl (group LF, n = 25). Each solution was hypobaric, and the same volume, 3 ml, was administered. Sensory and motor block characteristics, hemodynamic changes, side effects, number of patients having ability to stand and walk at the end of the operation, time to first analgesic requirement, time to urination, time to getting out of bed (ambulation), and time to home discharge were determined.

RESULTS

Sensory block onset time and time to reach the T6 dermatome were significantly shorter in group LF, whereas time to the two-segment regression and time to first analgesic requirement were significantly shorter in group RF. All patients in group LF were Bromage 0. Time to home discharge was shorter in group LF, but this difference was not statistically significant.

CONCLUSION

We suggest that both local anesthetics can be used in walking spinal technique. Levobupivacaine may be an alternative local anesthetic for walking spinal anesthesia as it provides minimum motor block and a long duration of postoperative analgesia, even if its use is not associated with a shorter home discharge time.

Improvement of quality of reporting in randomised controlled trials to prevent hypotension after spinal anaesthesia for caesarean section

Hypotension is a frequent complication of spinal anaesthesia for caesarean section and can threaten the well-being of the unborn child. Numerous randomised controlled trials (RCTs) dealt with measures to prevent hypotension. The aim of this study was to determine the reporting quality of RCTs using the Consolidated Standards of Reporting Trials (CONSORT) statement since low quality can lend false credibility to a study and overestimate the effect of an intervention. We performed a systematic literature search in PubMed to identify relevant RCTs in a pre-CONSORT period (1990-1994) and a post-CONSORT period (2004-2008). A comparative evaluation was done between the two periods, and the trials were assessed for compliance with each of the 22 CONSORT items. A total of 37 RCTs was identified. The CONSORT score increased significantly (p < 0.05) from 66.7% (±12.5%) in the pre-CONSORT period to 87.4% (±6.9%) in the post-CONSORT period. A statistically significant improvement was found for eight items, including randomization, blinding and intention-to-treat analysis. The CONSORT score in the post-CONSORT era was fairly good, also in comparison to other medical fields. In the post-CONSORT era, reporting of important items improved, in particular in the domains that are crucial to avoid bias and to improve internal validity. Use of CONSORT should be encouraged in order to keep or even improve the reporting quality.

Definitions of hypotension after spinal anaesthesia for caesarean section: literature search and application to parturients

BACKGROUND

Spinal anaesthesia for caesarean section may cause hypotension, jeopardizing the foetus and its mother. We aimed to identify the spectrum of definitions of hypotension used in the scientific literature. In a second part, we applied these definitions to a prospective cohort in order to evaluate the effect of different definitions on the incidence of hypotension.

METHODS

A systematic literature search in PubMed was performed from 1999 to 2009 with the search terms 'hypotension' and 'caesarean section'. Consecutive parturients undergoing caesarean section under spinal anaesthesia were included in a prospective study.

RESULTS

Sixty-three eligible publications (7120 patients) were retrieved, revealing 15 different definitions of hypotension. A decrease below 80% baseline and the combined definition of a blood pressure below 100 mmHg or a decrease below 80% baseline were the two most frequent definitions, found in 25.4% and 20.6% of the papers, respectively. When applying the spectrum of definitions to a prospective cohort, the incidences of hypotension varied between 7.4% and 74.1%. The incidence increased from 26.7% to 38.5% when using a value below 75% of baseline instead of below 70% of baseline.

CONCLUSION

There is not one accepted definition of hypotension in the scientific literature. The incidence of hypotension varies depending on the chosen definition. Even minor changes of the definition cause major differences in the frequency of hypotension. This makes it difficult to compare studies on interventions to treat/prevent hypotension and probably hampers progress in this area of research.

[Maternal hypotension with low doses of spinal bupivacaine or levobupivacaine and epidural volume expansion with saline for cesarean section]

BACKGROUND AND OBJECTIVE

Epidural volume extension (EVE) with saline solution can contribute to greater cephalad spread of drugs injected into the subarachnoid space during cesarean section. We studied the incidence of material hypotension with spinal bupivacaine or levobupivacaine (L-bupivacaine) and the spread after epidural saline injection.

MATERIAL AND METHODS

After ethics committee approval, we randomized women scheduled for cesarean section to 4 groups to receive 5 mg of 0.25% bupivacaine with (n=51) or without (n=6) saline EVE; 5 mg of 025% L-bupivacaine (n=50); or 6 mg of 03% L-bupivacaine (n=50). All patients also received 25 microg of fentanyl per 2 mL of local hyperbaric spinal anesthetic. In all except the non-EVE group, 10 mL of saline was infused through an epidural catheter 5 minutes after anesthetic infusion. We recorded patient demographic data, procedural and anesthetic times, incision-clamping times, occurrence of hypotension, ephedrine dose required, motor and sensory blockade, requirement for rescue analgesics, and neonatal outcome.

RESULTS

After 6 patients had been randomized to the non-EVE group, no further patients were assigned because all the women required rescue analgesics. Demographic data, duration of procedure, time between. incision and delivery, and Apgar scores were similar in all the groups. The incidence of hypotension was lower in the group receiving 5 mg of L-bupivacaine (26% vs. 52.9% in the bupivacaine 5-mg group, and 56% in the 6-mg L-bupivacaine group, P = .04). More women given 5 mg of L-bupivacaine required rescue analgesia (46%) than did those receiving 5 mg of bupivacaine (235%) or 6 mg of L-bupivacaine (28%) (P = .039). Hypotension was associated with a lower umbilical cord pH (P = .001). Ephedrine doses over 20 mg were also associated with a lower umbilical cord pH (P = .031).

CONCLUSIONS

The incidence of hypotension was lowest in the group anesthetized with 5 mg of L-bupivacaine, but the need for rescue analgesia was greater in this group. Doses of 5 mg and 6 mg may be sufficient for cesarean section, as they provide a good level of sensory blockade.

Pulmonary effects of bupivacaine, ropivacaine, and levobupivacaine in parturients undergoing spinal anaesthesia for elective caesarean delivery: a randomised controlled study

BACKGROUND

Spinal anaesthesia is the method of choice for elective caesarean delivery, but has been reported to worsen dynamic pulmonary function when using bupivacaine. Similar investigations are lacking for ropivacaine and levobupivacaine. We have therefore compared the pulmonary effects of intrathecal bupivacaine, ropivacaine and levobupivacaine used for caesarean delivery.

METHODS

Forced vital capacity, forced expiratory volume in the first second, and peak expiratory flow rate were measured in 48 parturients before and after onset of spinal anaesthesia using either 0.5% bupivacaine 10 mg, 1% ropivacaine 20 mg, or 0.5% levobupivacaine 10 mg. Apgar scores and umbilical arterial pH were recorded.

RESULTS

The final level of sensory blockade was not different between groups. Forced vital capacity was significantly decreased with bupivacaine (3.6+/-0.5 L to 3.5+/-0.4 L, P<0.05) and ropivacaine (3.2+/-0.4 L to 3.1+/-0.5 L, P<0.05), but not with levobupivacaine (3.6+/-0.5 L to 3.4+/-0.6 L). Forced expiratory volume during the first second was not decreased in any group. Peak expiratory flow rate was significantly decreased with ropivacaine (5.5+/-1.5 L/s to 5.0+/-1.1 L/s, P<0.05) and levobupivacaine (from 6.0+/-1.1 L/s to 5.2+/-0.9 L/s, P<0.01). Neonatal vital parameters did not differ between the three groups.

CONCLUSIONS

Decreases in maternal pulmonary function tests were similar following spinal anaesthesia with bupivacaine, ropivacaine, or levobupivacaine for caesarean delivery. The clinical maternal and neonatal effects of these alterations appeared negligible.

Influence of positioning on plain levobupivacaine spinal anesthesia in cesarean section

Background. The behaviour of isobaric levobupivacaine in relation to gravity when used in obstetric spinal anesthesia is unclear. Methods. 46 women with ASA physical status 1 undergoing cesarean section were randomly allocated to 2 groups. Spinal anesthesia with 12.5 mg levobupivacaine was performed in the sitting position in all women. Those in the first group were placed in the supine position immediately after the injection, while those in the second group were asked to remain seated for 2 minutes before assuming the supine position. The sensory block level, the onset of sensory and motor blocks, the regression of the sensory block for 2 dermatomes of the sensory block, the first request for analgesics, and the regression of motor block were recorded. Results. No differences in onset times, sensory level, or Bromage score were observed between the two groups. The time of first analgesic request was earlier in the seated group (supine 131 ± 42 min, seated 106 ± 29 min, P = .02). Conclusion. Isobaric levobupivacaine in women at term produces a subarachnoid block the dermatomal level of which does not depend on gravitational forces.

Intrathecal sufentanil decreases the median effective dose (ED50) of intrathecal hyperbaric ropivacaine for caesarean delivery

BACKGROUND

The addition of opioid to local anaesthetics has become a well-accepted practice of spinal anaesthesia for caesarean delivery. Successful caesarean delivery anaesthesia has been reported with the use of a low dose of intrathecal hyperbaric ropivacaine coadministered with sufentanil. This prospective, double-blinded study determined the median effective dose (ED50) of intrathecal hyperbaric ropivacaine with and without sufentanil for caesarean delivery, to quantify the sparing effect of sufentanil on the ED50 of intrathecal hyperbaric ropivacaine.

METHODS

Sixty-four parturients undergoing elective caesarean delivery with combined spinal-epidural anaesthesia were randomized into two groups: Group R (ropivacaine) and Group RS (ropivacaine plus sufentanil 5 microg). The initial dose of ropivacaine was 13 mg in Group R and 10 mg in Group RS. The effective dose was defined as a T(6) level attained within 10 min and no supplemental epidural anaesthetic required during surgery. Effective or ineffective responses determined, respectively, a 0.3 mg decrease or increase of the dose of ropivacaine for the next patient using an up-down sequential allocation.

RESULTS

The ED50 of intrathecal ropivacaine was 11.2 mg [confidence interval (CI) 95%: 11.0-11.6] in Group R vs. 8.1 mg (CI 95%: 7.8-8.3) in Group RS. Motor block was markedly more intense in Group R than in Group RS, and the incidence of shivering was lower in Group RS than in Group R. There were no differences in the onset time of sensory block or motor block, in the incidence of hypotension, nausea and vomiting.

CONCLUSION

Intrathecal sufentanil 5 microg produced a 28% reduction of ED50 of intrathecal hyperbaric ropivacaine for caesarean delivery.

Adding sufentanil to levobupivacaine or ropivacaine intrathecal anaesthesia affects the minimum local anaesthetic dose required

BACKGROUND

We carried out this prospective, randomized, double-blind study in order to evaluate whether the intrathecal addition of sufentanil 3.3 mcg affects both the minimum local anaesthetic dose (MLAD) of spinal levobupivacaine and ropivacaine for a caesarean section and enhances the spinal block characteristics.

METHODS

One hundred and eighty women were randomly allocated into four groups: levobupivacaine (Group L), levobupivacaine plus sufentanil (Group L+S), ropivacaine (Group R) and ropivacaine plus sufentanil (Group R+S). Each received 3 ml of the study solution intrathecally as part of a combined spinal/epidural technique. The initial dose was 12 mg for Groups L and L+S, and 15 mg for Groups R and R+S. The test solution was required to achieve a visual analogue pain score (VAPS) of 30 mm or less to be considered effective at skin incision, uterine incision, birth, peritoneal closure and at the conclusion of surgery. Effective or ineffective responses determined a 0.5 mg decrease or increase of the same drug, respectively, for the next patient in the same group, using an up-down sequential allocation.

RESULTS

Using the Dixon and Massey formula, the MLAD was 10.65 mg [confidence interval (CI) 95%: 10.14-11.56] in Group L, 4.73 mg (CI 95%: 4.39-5.07) in Group L+S, 14.12 mg (CI 95%: 13.50-14.60) in Group R and 6.44 mg (CI 95%: 5.86-7.02) in Group R+S.

CONCLUSIONS

The addition of sufentanil reduced the MLAD of both the local anaesthetics. It did not affect their potency ratio significantly and resulted in enhanced spinal anaesthesia.

The median effective dose of bupivacaine, levobupivacaine, and ropivacaine after intrathecal injection in lower limb surgery

BACKGROUND

Intrathecal anesthesia is commonly used for lower limb surgery. Bupivacaine, levobupivacaine, and ropivacaine have all been used as intrathecal drugs, but their relative potency in this context has not been fully determined. In this study, we determined the median effective dose (ED(50)) of these three local anesthetics for intrathecal anesthesia in lower limb surgery and hence their relative potencies.

METHODS

Seventy-five patients scheduled for lower limb surgery under combined spinal-epidural anesthesia were randomly allocated to one of three groups receiving intrathecal bupivacaine, levobupivacaine, or ropivacaine. The dose of local anesthetic was varied using up-down sequential allocation technique. The dose for the first patient in each group was 8 mg, and the dosing increment was set at 1 mg. Subsequent doses in each group were determined by the outcome in the previous patient using success or failure of the spinal anesthesia as the primary end point. A success was recorded if a bilateral T12 sensory block to cold was attained within 20 min after intrathecal injection, and the surgery proceeded successfully until at least 50 min after the intrathecal injection without supplementary epidural injection. The ED(50) was calculated using the method of Dixon and Massey.

RESULTS

The ED(50)s were 5.50 mg for bupivacaine (95% confidence interval [CI]: 4.90-6.10 mg), 5.68 mg for levobupivacaine (95% CI: 4.92-6.44 mg), and 8.41 mg for ropivacaine (95% CI: 7.15-9.67 mg) in intrathecal anesthesia. The relative anesthetic potency ratios are 0.97 (95% CI: 0.81-1.17) for levobupivacaine/bupivacaine, 0.65 (95% CI: 0.54-0.80) for ropivacaine/bupivacaine, and 0.68 (95% CI: 0.55-0.84) for ropivacaine/levobupivacaine.

CONCLUSION

This study suggests that in intrathecal anesthesia for lower limb surgery, ropivacaine is less potent than levobupivacaine and bupivacaine, whereas the potency is similar between levobupivacaine and bupivacaine.

Hemodynamic effects of ropivacaine and levobupivacaine intravenous injection in swines

PURPOSE: To compare the hemodynamic effects following a toxic dose of either agent after intravenous injection in swines, as might accidentally occur during regional anesthesia in humans. METHODS: Large White pigs were anesthetized with thiopental, tracheal intubation was performed and mechanical ventilation was instituted. Hemodynamic variables were recorded with invasive pressure monitoring and pulmonary artery catheterization. After a 30-minute resting period, the animals were randomly divided into two groups in a double-blinded fashion and received a bolus intravenous injection of 4 mg.kg-1 of either agent. Hemodynamic results were evaluated at rest and 1, 5, 10, 15, 20 and 30 minutes after intoxication. RESULTS: Hemodynamic repressions of acute intoxication with levobupivacaine were more important and more prolonged than those of ropivacaína. CONCLUSION: In pigs, levobupivacaine was shown to be more toxic than ropivacaine when the same large doses are injected intravenously.

Anaesthesia for urgent (grade 1) caesarean section

PURPOSE OF REVIEW

We describe the different possible anaesthetic techniques for an emergency caesarean section. To choose the right method of anaesthesia may have major implications for mother, child and all involved personnel. The major controversy is whether one have other or better alternatives or both than general anaesthesia, with a rapid sequence induction technique, when the foetus is compromised.

RECENT FINDINGS

Recently published studies indicate that a top-up of a well functioning labour epidural is as fast as general anaesthesia, and that the top-up can be performed during preparation and transport. Spinal anaesthesia, when performed by skilled anaesthetists, is as fast or almost as fast as general anaesthesia with a very low failure rate. Combined spinal/epidural may have advantages, especially in high-risk cardiac patients, but is too time-consuming. General anaesthesia still seems to be the method of choice for most anaesthetists in extremely urgent settings. The major disadvantage with general anaesthesia is the risk of failure and the dramatic consequences of a 'cannot intubate, cannot ventilate' situation. Awareness is another concern, and the incidence varies from 0.26 to 1% in recent literature.

SUMMARY

Regional anaesthesia techniques such as a single-shot spinal or a top-up of a well functioning labour epidural analgesia are good alternatives to general anaesthesia in an emergency caesarean setting.

[Levobupivacaine for parturients undergoing elective caesarean delivery. A dose-finding investigation]

BACKGROUND

The optimum intrathecal dose of hyperbaric levobupivacaine for spinal anaesthesia during elective caesarean section has not yet been investigated.

METHODS

A total of 30 parturients undergoing elective caesarean section were included in this prospective, randomised, double-blind study. Parturients received either 7.5, 10 or 12.5 mg hyperbaric 0.5% levobupivacaine intrathecally. Analgesic, sensory and motor block characteristics as well as maternal and fetal levobupivacaine plasma concentrations were determined.

RESULTS

Of the parturients receiving 7.5 mg levobupivacaine 40% required supplementary intravenous opioid analgesics intraoperatively and none achieved complete motor block. Compared to 7.5 mg levobupivacaine, 10 and 12.5 mg significantly prolonged duration of effective analgesia postoperatively (median: 45 vs. 81 and 96 min, respectively). Both maternal and fetal levobupivacaine plasma concentrations were low, with dose-dependent, statistically significant differences in maternal plasma concentrations.

CONCLUSIONS

Levobupivacaine 7.5 mg did not provide satisfactory intraoperative analgesia in all parturients. There were no statistically significant differences between 10 and 12.5 mg levobupivacaine with respect to analgesic, sensory and motor block characteristics. Therefore, based on these data, 10 mg levobupivacaine is recommended for parturients undergoing elective caesarean section with spinal anaesthesia.