Chloroprocaine antagonism of epidural opioid analgesia: a receptor-specific phenomenon?

Comparison of lidocaine bicarbonate with fentanyl and chloroprocaine for epidural anesthesia during cesarean section: a randomized, controlled, double-blind clinical trial

Chloroprocaine and lidocaine bicarbonate are commonly used for epidural anesthesia because of their rapid onset, particularly in the case of conversion from epidural labor analgesia to emergency cesarean section. However, it is unclear whether lidocaine bicarbonate combined with fentanyl has an advantage over chloroprocaine alone in emergency cesarean section. In this study, 102 women who underwent elective cesarean section received 15 mL 3% chloroprocaine and 1 mL saline (CP group) or 15 mL 1.73% lidocaine bicarbonate and 1 mL fentanyl 50 μg (LF group) for epidural anesthesia. Nociceptive block level was assessed by pinprick and recorded every minute. The primary outcome was the onset time to T6 block. The median onset time to T6 analgesia was 10 [10, 10] min in the CP group and 10 [7, 10] min in the LF group (COX model for CP versus LF, HR 0.47, 95% CI 0.23-0.95, p = 0.035). The median onset time to T8 analgesia was 7 [5, 9] min in CP group and 5 [4, 7] min in LF group (COX model for CP versus LF, HR 0.61, 95% CI 0.39-0.95, p = 0.027). The proportion of hypotension episodes occurring before delivery in LF group was lower than that in CP group (p = 0.011). The incidence of block level ≥ T4 after supplemental dosing in the LF group was lower than that in the CP group (p = 0.031). Compared with 3% chloroprocaine, 1.73% lidocaine bicarbonate combined with fentanyl 50 μg has a slightly faster onset time and less hypotension in epidural anesthesia for cesarean section. Clinical Trial Registration: http://www.chictr.org.cn/index.html, identifier ChiCTR2200056180.

Postcesarean Analgesia With Epidural Morphine After Epidural 2-Chloroprocaine: A Randomized Noninferiority Trial

BACKGROUND

Previous studies have suggested that administration of epidural 3% 2-chloroprocaine (CP) before epidural morphine results in decreased analgesic efficacy of epidural morphine. We sought to determine whether these observations were a result of antagonism or a window period between the conclusion of surgical anesthesia for cesarean delivery and the peak onset time of epidural morphine, and whether a method to preserve the analgesic efficacy of epidural morphine exists.

METHODS

Term parturients scheduled for nonemergent, unscheduled cesarean delivery with preexisting labor epidural catheters were recruited for this exploratory, randomized, single-blinded, noninferiority trial. Subjects were randomized to initial dosing to a T4 dermatome surgical anesthetic level with either 3% CP or 2% lidocaine with 1:200,000 epinephrine and sodium bicarbonate (LEB). Subsequent redosing for both groups was performed with LEB at regular intervals. Epidural morphine 3 mg was administered to both groups after delivery. Assessing the difference between the 2 groups in total opioid use for the first 24 hours after epidural morphine administration was the primary objective. The noninferiority margin of 10 oral milligram morphine equivalents was prespecified based on previous noninferiority studies. Secondary end points included time from epidural morphine administration to first rescue opioid request, numerical pain scores, nausea/vomiting, and pruritus.

RESULTS

Data were analyzed for 40 parturients, 20 in each group. The median 24-hour opioid consumption for the CP group was 0 (Q1 = 0 and Q3 = 15.6) oral milligram morphine equivalents compared to 15 (6.3-22.5) for the LEB group. The median difference was -7.5, with a 95% confidence interval -15 to 0. Noninferiority was concluded, as the confidence interval was less than the predetermined noninferiority margin of 10 oral milligram morphine equivalents. There was no treatment effect on time to first opioid request and no statistically significant differences in pain scores or nausea, vomiting, or pruritus at all time points (4, 8, 12, and 24 hours after epidural morphine administration).

CONCLUSION

While designed as an exploratory study, initial epidural dosing with 3% CP and beginning subsequent redosing with LEB within 30 minutes of the initial CP bolus provided noninferior postcesarean analgesia with epidural morphine compared to initial epidural dosing and redosing with LEB. Previous observations of decreased analgesic efficacy of epidural morphine after epidural CP were likely due to a window period that may be mitigated by redosing with lidocaine; however, larger studies are necessary to confirm these findings.

Continuous Epidural Analgesia Using an Ester-Linked Local Anesthetic Agent, 2-Chloroprocaine, During Labor: A Case Report

We report the use of the ester-linked local anesthetic, 2-chloroprocaine, for continuous epidural analgesia in a patient in labor with a history of allergic reaction to amide local anesthetics. The patient gave a reliable history of pruritus, hives, erythema, and swelling on her lower extremity after having received a preservative-free amide local anesthetic. This allergy had been confirmed by a dermatologist by her reports. The patient requested an epidural for labor analgesia that was placed successfully. After an initial bolus, a continuous infusion of 1.5% of 2-chloroprocaine was initiated to achieve satisfactory pain relief throughout an uneventful vaginal delivery.

Chloroprocaine may not affect epidural morphine for postcesarean delivery analgesia

STUDY OBJECTIVE

The purpose of this study is to assess the independent effect of epidural chloroprocaine on morphine used for pain relief after cesarean delivery.

DESIGN

We used a randomized, double blind, placebo-controlled trial.

SETTING

The study took place at the labor and delivery ward of an academic medical center.

PATIENTS

Forty pregnant women undergoing elective cesarean delivery under spinal-epidural anesthesia.

INTERVENTIONS

Patients were randomized to receive either 150 mg of 3% chloroprocaine or placebo, followed by 3 mg of epidural morphine.

MEASUREMENTS

The primary outcome for this investigation was the duration of pain relief after morphine administration, defined as the time at first use of supplemental opioids for analgesia. Secondary outcomes included pain scores, blood pressure, heart rate, respiratory rate, anesthetic sensory level, nausea and vomiting, pruritus, supplemental use of nonsteroidal anti-inflammatory medications, and satisfaction.

MAIN RESULTS

The groups were similar in demographics and duration of spinal anesthesia. Using Kaplan-Meier survival analysis of the duration of morphine analgesia, we found no difference between the groups (chloroprocaine, 1191 minutes, vs placebo, 1267 minutes, P = 0.52). There was no difference in pain scores or the need for supplemental analgesics. Side effects of epidural morphine were similar between the groups.

CONCLUSIONS

We found that epidural chloroprocaine did not reduce the duration or effectiveness of postoperative analgesia from epidural morphine.

Spinal 2-Chloroprocaine: The Effect of Added Fentanyl

Chloroprocaine is being investigated as a possible replacement for spinal lidocaine. Adding fentanyl to lidocaine increases the quality of spinal anesthesia without prolongation of block. We report the characteristics of 2-chloroprocaine (2-CP) spinal anesthesia with or without fentanyl in 8 volunteers receiving 40 mg 2-CP with saline or 20 micro g fentanyl in a double-blinded, randomized, crossover manner. Spinal anesthesia was successful for all subjects with complete block regression, ambulation, and void by 110 min. Itching occurred in all subjects receiving fentanyl, though medication was not required. No subject reported signs of transient neurological symptoms. Peak block with fentanyl averaged T5 (T3-7) and without fentanyl T9 (L1-T4) (P = 0.005). Regression to L1 was 78 +/- 7 min with fentanyl and 53 +/- 19 min without fentanyl (P = 0.02). Tourniquet was tolerated for 51 +/- 8 min with fentanyl and for 34 +/- 14 min without fentanyl (P = 0.02). Complete regression of block occurred at 104 +/- 7 min with fentanyl and by 95 +/- 9 min without fentanyl (P = 0.02). We conclude that 2-CP spinal anesthesia provides rapid onset and adequate potency, giving it a positive profile for ambulatory surgery. The addition of fentanyl lengthens regression to L1 and tourniquet tolerance while minimally lengthening block duration.

IMPLICATIONS

Spinal 2-chloroprocaine (40 mg) provides rapid onset and reliable blockade without signs of transient neurological symptoms, giving it a positive profile for ambulatory surgical settings. The addition of fentanyl appears to lengthen the regression to L1 dermatome and tourniquet time while minimally lengthening duration of block.

Opioid analgesics

Opioids are useful and potent drugs for the management of pain in small animal patients. They have a wide therapeutic index and can be given by a number of different routes. Some of these techniques (e.g., epidural and intraarticular) allow for the production of profound analgesia in a localized area of the body while limiting the dose and the side effects, and others provide a noninvasive method for the delivery of continuous analgesia (e.g., transdermal administration).

2-Chloroprocaine antagonism of epidural morphine analgesia

BACKGROUND

2-Chloroprocaine (2-CP) used for lumbar epidural anesthesia (LEA) reportedly decreases the efficacy of epidural morphine (EM) administered for post-cesarean section (CS) analgesia. The amount of supplemental i.v. morphine self-administered by the patient via the patient-controlled analgesia device (PCA) is used to study the interaction between EM and 2-CP.

METHODS

Forty-two patients scheduled for elective CS were randomly divided into 3 equal groups, and received 2-CP, 2-CP + epinephrine (Epi, 5 micrograms.ml-1) or 2% lidocaine (Lido) with Epi for LEA. All patients received 5 mg EM and i.v. PCA morphine for postoperative pain. Cumulative amount of i.v. morphine used in the first 24 hours as well as the amount of the drug used during each 2-h period were noted. Nonparametric analysis of variance and Chi-squared analysis were used for statistical comparisons.

RESULTS

The mean cumulative 24-h i.v. PCA morphine requirement in the 2-CP, 2-CP+Epi and Lido+Epi groups respectively was 20.5 +/- 24, 33.1.5 +/- 27 and 4.07 +/- (mean +/- SD). The Lido + Epi group used significantly less morphine (P = 0.01) compared to either of the 2-CP groups with no significant difference between the 2-CP groups. The maximum i.v. PCA morphine use occurred in the first 4 hours following surgery in all three groups.

CONCLUSION

Analgesic efficacy of EM is decreased when 2-CP is used for LEA compared to when Lido + Epi is used.

Local and regional anesthesia and analgesia

Many benefits can be obtained from the use of drugs applied locally or regionally when treating dogs and cats that are in pain or will be in pain because of surgical trauma. These techniques often use less medication than for systemic administration with a reduction in the likelihood of toxic effects from these compounds. Complete relief of pain can be achieved by blocking nerves originating from the site of injury by using local anesthetics, but this may entail loss of all sensation and motor paralysis. Other drugs, such as the opioids, may decrease the nociceptive input with minimal effect on motor activity. This report discusses the use of local anesthetics and other drugs for analgesia of the skin, mucous membranes, joints, pleura, and peritoneum, and the application of these drugs for regional blocks of peripheral nerves and epidural/intrathecal injection.

The effect of epidural fentanyl on the minimum local analgesic concentration of epidural chloroprocaine in labor

The minimum local analgesic concentration (MLAC) has been defined as the median effective local analgesic concentration (EC50) in a 20-mL volume in the first stage of labor. The aim of this study was to determine the local anesthetic sparing efficacy of epidural fentanyl by its effect on the MLAC of chloroprocaine. Fifty-six parturients, not exceeding 7 cm cervical dilation, who requested epidural analgesia were allocated to one of two groups in this double-blind, randomized, prospective study. After placing a lumbar epidural catheter, 20 mL of the solution being tested was given: chloroprocaine (n = 28) or chloroprocaine with fentanyl 3 micrograms/mL (60 micrograms) (n = 28). The concentration of chloroprocaine was determined by the response of the previous patient to a higher or lower concentration using up-down sequential allocation. Analgesic efficacy was assessed using 100-mm visual analog pain scores with 10 mm or less within 30 min defined as effective. The MLAC of chloroprocaine was reduced from 0.43% wt/vol to 0.26% wt/vol by fentanyl (P = 0.023). Thus, the addition of epidural fentanyl 3 micrograms/mL (60 micrograms resulted in a significant 40% reduction in the MLAC of chloroprocaine in the first stage of labor.

Drug interactions with intravenous and local anaesthetics

Relatively few clinically significant drug interactions with anaesthetics have been documented in the literature. The following should be stressed since these interactions are not readily predictable or are potentially fatal. Pethidine should never be administered to patients who have received monamine oxidase inhibiting drugs within the last fortnight, since a fatal hyperpyrexia and/or hypertension may result. Thiopentone induction seems to make the heart more susceptible to arrhythmias caused by adrenergic drugs, and may cause severe arterial hypotension in patients treated with diazoxide. Midazolam orally should possibly be avoided as premedication in patients treated with erythromycin since anaesthetic concentrations of midazolam may result. Patients for whom bupivacaine analgesia is planned could preferentially be premedicated with other drugs than diazepam, which causes the serum level of bupivacaine to increase. Bradycardia and hypotension not attributable to sympathetic blockade have been reported following bupivacaine extradurally in verapamil-treated patients. Sulfonamides and the ester group of local anaesthetics, such as prilocaine in combination, may result in severe methaemoglobinaemia in infants. Epinephrine added to local anaesthetics may cause local vasodilation if administered to patients concurrently being treated with cyclic antidepressants, and the combination imposes the risk of severe hypertension and arrhythmias.

Fentanyl: clinical use as postoperative analgesic--epidural/intrathecal route

The administration of epidural and intrathecal opioids for the management of postoperative pain is well established. Fentanyl, because of its greater lipophilicity, offers a number of advantages over morphine for epidural analgesia, including a lower incidence of side effects and reduced risk of delayed-onset respiratory depression. The relatively short duration of action of epidural fentanyl makes this agent more ideally suited for continuous infusion or patient-controlled epidural analgesia (PCEA). The effective doses and adverse effects profile of epidural fentanyl are reasonably well understood. Because of the lack of spread through the cerebrospinal fluid (CSF) and hence the segmental nature of the analgesia achieved, location of epidural catheter placement is of paramount importance when this agent is used. Prolonged epidural infusion of fentanyl may result in high systemic concentrations not dissimilar to IV infusion, and, therefore, the greatest efficacy of epidural fentanyl administration may be in combination with low concentrations of bupivacaine, an approach that achieves a synergistic effect. 2-Chloroprocaine has been shown to antagonize epidural fentanyl analgesia. Intrathecal fentanyl for postoperative analgesia is limited by its short duration of action with single-bolus administration. The widespread international increase in the use of epidural fentanyl for postoperative analgesia promises further improvements and refinement in techniques.

Epidural nalbuphine for analgesia following caesarean delivery: dose-response and effect of local anaesthetic choice

The analgesic profile of epidural nalbuphine for postoperative pain relief and the impact of local anaesthetic choice upon this profile was investigated in 58 patients undergoing elective Caesarean delivery under epidural anaesthesia. Patients were randomized to receive either lidocaine 2% with 1:200,000 epinephrine or 2-chloroprocaine 3% for perioperative anaesthesia, followed by either 10, 20, or 30 mg of epidural nalbuphine administered at the first complaint of postoperative discomfort. Postoperative analgesia was quantitated on a visual analogue (VAS) scale, and by the time from the epidural opioid injection until the first request for supplemental pain medication. The duration of analgesia after lidocaine anaesthesia followed by 10, 20 or 30 mg nalbuphine was 77 (53-127) min, 205 (110-269) min, and 185 (116-241), respectively (median, 95% confidence interval, P less than 0.01, 20 and 30 mg vs 10 mg). Following 2-chloroprocaine anaesthesia, VAS remained consistently elevated: the median duration of analgesia was only 30-40 min and did not differ among the three doses of nalbuphine. Side-effects consisted only of somnolence, and were noted only following lidocaine anaesthesia. Somnolence was observed in 0, 20% and 50% of those receiving 10 mg, 20 mg and 30 mg of nalbuphine respectively (NS). No evidence of respiratory depression was noted in any patient. It is concluded that 20 or 30 mg of epidural nalbuphine provides analgesia for only two to four hours following Caesarean delivery with lidocaine anaesthesia, but anaesthesia with 2-chloroprocaine resulted in minimal or no analgesia from this opioid. Nalbuphine appears to be a disappointing agent for epidural use after Caesarean delivery.