Determination of the minimum local analgesic concentrations of epidural bupivacaine and lidocaine in labor

The Effect of Dezocine on the Median Effective Dose of Sufentanil-Induced Respiratory Depression in Patients Undergoing Spinal Anesthesia Combined with Low-Dose Dexmedetomidine

Purpose

The application of sedation and analgesia in spinal anesthesia has many benefits, but the risk of respiratory depression (RD) caused by opioids cannot be ignored. We aimed to observe the effect of dezocine, a partial agonist of μ-receptor, on the median effective dose (ED50) of sufentanil-induced RD in patients undergoing spinal anesthesia combined with low-dose dexmedetomidine.

Patients and Methods

Sixty-two patients were randomly assigned to dezocine group (DS) and control group (MS). After spinal anesthesia, mask oxygen (5 L/min) and dexmedetomidine (0.1 ug/kg) were given. Five minutes later, patients in the DS group received an Intravenous (IV) bolus of sufentanil and 0.05mg/kg dezocine, while patients in the MS group only received an IV bolus of sufentanil.

Results

ED50 of DS group was 0.342 ug/kg, 95% confidence interval (CI) was (0.269, 0.623) ug/kg, and the ED50 of MS group was 0.291 ug/kg, 95% CI was (0.257, 0.346) ug/kg. There was no difference in the type and treatment measures of RD and hemodynamic changes between the two groups, and no serious adverse reactions occurred in either group.

Conclusion

Dezocine can improve RD induced by sufentanil in patients with spinal anesthesia combined with low-dose dexmedetomidine, and increase the safety window of sufentanil use.

Evaluation of association factors for labor episodic pain during epidural analgesia

Purpose

Epidural analgesia provides safe and effective labor pain relief. However, labor episodic pain can occur during epidural analgesia, requiring epidural top-ups, and may result in decreased patient satisfaction. The primary aim of our study was to investigate the factors associated with labor episodic pain during epidural analgesia.

Patients and methods

Electronic and hardcopy records of labor deliveries between January 2012 and December 2015 were reviewed at KK Women's and Children's Hospital, Singapore. The primary outcome was the prevalence of episodic pain. Demographic, clinical and anesthetic data were retrieved. Univariate and multivariate logistic regression analyses were used to identify associated risk factors for labor episodic pain experienced by parturients while receiving epidural analgesia. Model performance was assessed by area under the curve (AUC) from the receiver operating characteristic curve.

Results

The prevalence of labor episodic pain was 14.2% (2,951 of 20,798 parturients). The risk factors associated with labor episodic pain, which are given here as factor (OR, 95% CI), are the following: need for epidural resiting (11.4, 7.53-17.28), higher pain scores intrapartum (1.34, 1.32-1.36), higher Bromage scores (1.12, 1.02-1.22), the need for instrumental delivery (1.32, 1.16-1.52), the need for cesarean delivery (1.41, 1.26-1.59), the presence of venous puncture (1.29, 1.03-1.62), the presence of dural puncture (14.28, 5.92-34.43), the presence of high block (6.05, 1.39-26.35), the need for a urinary catheter (1.17, 1.17-1.34), larger volumes of local anesthetics used (1.01, 1.01-1.01) and higher body mass index (1.01, 1.01-1.02), and decreased maternal satisfaction (0.97, 0.97-0.98). The AUC was 0.80.

Conclusion

Knowledge of these factors may allow for future interventions in management to prevent labor episodic pain. Further research is needed to validate these association factors.

Effect of Baricity of Bupivacaine on Median Effective Doses for Motor Block

Background

The median effective dose (ED₅₀) of a drug gives the amount or dose of drug needed to produce effective therapeutic response or desired effect in at least 50% of the population taking it. Our study focused on determining the ED₅₀ required for effective motor block using hyperbaric and plain bupivacaine, and evaluated the influence of baricity on the ED₅₀ required for motor block.

Material/Methods

A total of 38 patients were randomly assigned into 2 groups according to the baricity of bupivacaine: group P received plain bupivacaine and group H received hyperbaric bupivacaine. The patients were administered 0.5% plain or hyperbaric bupivacaine intrathecally. The dosage of anesthetics in each patient was calculated according to the standard up-down sequential allocation method of Dixon. The first patient in each group received a dose of 7.5 mg bupivacaine, and a dose of 1.0 mg was used as the testing interval. The dose was increased or decreased by 1.0 mg for each patient according to the estimated score of motor block.

Results

The ED₅₀ required for effective motor block in spinal anesthesia was 7.20 and 10.05 mg in groups H and P, respectively. Their relative motor blocking potency ratio was found to be 0.72.

Conclusions

The ED₅₀ for motor block was significantly decreased using hyperbaric bupivacaine intrathecally compared with plain bupivacaine, and the baricity of bupivacaine obviously affected the ED₅₀ for the motor block.

Determination of the median effective dose (ED50) of spinal plain ropivacaine for motor block in adults

BACKGROUND

The median effective dose (ED50) for motor blockade of spinal plain bupivacaine in adults was previously reported; however, that of ropivacaine is unknown. This study aimed to determine the ED50 for motor blockade of spinal plain ropivacaine in adults, evaluating the effect of age on this parameter.

METHODS

133 patients in need of combined spinal and epidural anesthesia were enrolled in this sequential allocation study. They were divided into 6 groups according to age: 20-30, 31-40, 41-50, 51-60, 61-70, and 71-80 years. Using the up-and-down method of Dixon, the ropivacaine dose was varied according to the preceding patient's reaction. The modified Bromage and hip motor function score was used to evaluate the degree of motor block after administration of ropivacaine. ED50 values were estimated by the method of Dixon and Massey. Other indexes, including the onset of motor block, the analgesia level, and the duration of motor block were also assessed.

RESULTS

the ED50 for motor block of intrathecal ropivacaine was 20.96 mg (95 % CI: 19.83-22.16 mg) in 20-30, 19.05 mg (95 % CI: 18.43-19.70 mg) in 31-40, 17.91 mg (95 % CI: 17.10-18.76 mg) in 41-50, 17.91 mg (95 % CI: 16.49-19.44 mg) in 51-60, 16.11 mg (95 % CI: 14.50-17.90 mg) in 61-70, and 15.75 mg (95 % CI: 13.98-17.73 mg) in 71-80 year-old patients. Maximum cephalic analgesic effects were obtained at the L4-T6 and L4-T2 levels, at 5 and 10 min, respectively, after intrathecal administration of ropivacaine in all groups.

CONCLUSION

the ED50 for motor block in spinal plain ropivacaine decreases with advancing age, indicating that age has an influence on the potency of spinal ropivacaine.

Effect of Concentration on Median Effective Dose (ED50) for Motor Block of Intrathecal Plain Bupivacaine in Elderly Patients

Background

The aim of the study was to determine the median effective dose (ED₅₀) for motor block of various concentrations of intrathecally administered plain bupivacaine.

Material/Methods

Between 2011 and 2013, 64 patients aged ≥70 years, undergoing transurethral, or lower limb surgery with combined spinal and epidural anesthesia in a single hospital were enrolled. The patients were randomized into 3 groups to receive intrathecal 0.75% bupivacaine (Group 1), 0.375% bupivacaine (Group 2) or 0.25% bupivacaine (Group 3). Spinal anesthesia was achieved using injections of up-and-down doses of 0.75%, 0.375%, or 0.25% plain bupivacaine. The first patient in each group received 7.5 mg bupivacaine, and the testing interval was set at 0.75 mg. The efficacy of motor block in both legs was determined using a modified Bromage and a hip motor function scale. The ED₅₀ for motor block was estimated according to the Dixon’s up-and-down method.

Results

The ED₅₀ for motor block of bupivacaine was 6.10 (95% CI 5.58–6.66) mg in Group 1, 6.04 (95% CI 5.82–6.28) mg in Group 2, and 5.43 (95% CI 5.19–5.67) mg in Group 3. There were significant differences in the ED₅₀ for motor block among the groups (P=0.008).

Conclusions

The ED₅₀ doses for motor block with 3 bupivacaine concentrations were significantly different in elderly patients; the ED₅₀ dose of 0.75% bupivacaine being significantly higher than that of 0.25% bupivacaine.

Lipid emulsion for local anesthetic systemic toxicity

The accidental overdose of local anesthetics may prove fatal. The commonly used amide local anesthetics have varying adverse effects on the myocardium, and beyond a certain dose all are capable of causing death. Local anesthetics are the most frequently used drugs amongst anesthetists and although uncommon, local anaesthetic systemic toxicity accounts for a high proportion of mortality, with local anaesthetic-induced cardiac arrest particularly resistant to standard resuscitation methods. Over the last decade, there has been convincing evidence of intravenous lipid emulsions as a rescue in local anesthetic-cardiotoxicity, and anesthetic organisations, over the globe have developed guidelines on the use of this drug. Despite this, awareness amongst practitioners appears to be lacking. All who use local anesthetics in their practice should have an appreciation of patients at high risk of toxicity, early symptoms and signs of toxicity, preventative measures when using local anesthetics, and the initial management of systemic toxicity with intravenous lipid emulsion. In this paper we intend to discuss the pharmacology and pathophysiology of local anesthetics and toxicity, and the rationale for lipid emulsion therapy.

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

We determined the minimum local anaesthetic dose (MLAD) of spinal levobupivacaine and ropivacaine for Caesarean section. Ninety women were randomly allocated to two groups and received 3 ml of study solution by a combined spinal/epidural technique. The initial dose was 12 mg for levobupivacaine and 17 mg for ropivacaine groups. To be considered effective, a test solution had to achieve a visual analogue pain score (VAPS) of 30 mm or less at skin incision, uterine incision, birth, peritoneal closure, and at the end of surgery. Effective or ineffective responses determined, respectively, a 0.3 mg decrease or increase of the same drug for the next patient in the same group, using up-down sequential allocation. The MLAD of levobupivacaine was 10.58 mg (CI 95%: 10.08-11.09) and the MLAD of ropivacaine 14.22 mg (CI 95%: 13.67-14.77), using the Dixon and Massey formula. The potency ratio between spinal levobupivacaine and spinal ropivacaine was 1.34.

Levobupivacaine spinal anesthesia in neonates: a dose range finding study

BACKGROUND

Our aim was to determine the clinical efficacy of levobupivacaine for awake spinal anesthesia in ex-premature infants having lower abdominal surgery. The secondary aim was to determine the minimum local analgesic dose (MLAD) defined as the median effective local anesthetic dose for spinal anesthesia in neonates.

METHODS

Fifty neonates < 55 weeks postconceptional age having lower abdominal surgery were enrolled. The dose of levobupivacaine was determined by up-down sequential allocation. The first infant received 1.25 mg x kg(-1) 0.5% levobupivacaine with subsequent doses determined by the response of the previous patient. Dose interval was 0.25 mg x kg(-1).

RESULTS

There were no significant adverse effects attributable to levobupivacaine. Success rates for 1.25, 1, 0.75 and 0.5 mg x kg(-1) were 100, 83, 81 and 46%, respectively. Mean duration (95% confidence interval) of lower limb motor blockade was 81.7 min (75.8-87.6 min). Duration of anesthesia far exceeded surgical duration in all but one case. The up-down sequences were analyzed with the Dixon and Massey method. The motor block MLAD (95% confidence interval) was 0.48 mg x kg(-1) (0.42-0.54). Probit analysis was used to compare calculated ED50 and to calculate an ED95 by extrapolation of data into the clinical range. The ED(50) (95% C.I.) was 0.52 mg x kg(-1) (0.30-0.73). The calculated ED95 was 1.14 mg x kg(-1) (0.78-1.50). These values were confirmed by logit analysis.

CONCLUSIONS

Levobupivacaine is an effective agent for spinal anesthesia in neonates at a recommended dose of 1 mg x kg(-1). It appears to be of equivalent potency to racemic bupivacaine for motor blockade in ex-premature infants requiring lower abdominal surgery.