Intrathecal Fentanyl-induced Pruritus is More Severe in Combination with Procaine Than with Lidocaine or Bupivacaine:

Evaluation of Therapies for Peripheral and Neuraxial Opioid-induced Pruritus based on Molecular and Cellular Discoveries

Opioids are a mainstay of treatment for pain worldwide. Pruritus, a common side effect of opioids, is a patient dissatisfier that limits their use in many clinical settings. Both parenteral and neuraxial administration of opioids frequently evoke pruritus. The ability of opioids to suppress pain while causing itch continues to perplex clinicians and researchers alike. Several mechanisms have been proposed to explain how opioids can give rise to pruritus, but specific knowledge gaps perpetuate debate. This review summarizes the clinical burden of opioid-induced pruritus and emphasizes recent discoveries of peripheral and central mechanisms for opioid-induced pruritus, particularly with respect to scientific and conceptual advances in spinal cord circuitry and mast cell biology. The mechanisms and effectiveness of existing medications used for clinical management of pruritus will be evaluated, and we will highlight the emerging preclinical utility of selective κ-opioid receptor agonists, such as nalfurafine, for the management of opioid-induced pruritus.

Pruritus after continuous administration of epidural morphine for post-cesarean delivery analgesia: a case control study

Background

Pruritus is one of the most common side effects of epidural morphine administered for post-surgery analgesia, and pregnant women tend to be highly susceptible. The relative contributions of morphine concentration, local anesthetics, and level of pain to pruritus after epidural morphine for post-cesarean delivery analgesia remain unclear. Accordingly, the present study aimed to identify risk factors for pruritus after continuous administration of epidural morphine for post-cesarean delivery analgesia.

Methods

This case control study was based on routinely collected clinical data. Participants included women who had undergone cesarean section and adopted a patient-controlled analgesia pump for postoperative analgesia. A series of logistic regression analyses were performed. Interaction terms were added to explore the moderation effects of combined local anesthetics and pain level on associations between morphine concentration and pruritus. Robustness of the results was checked through sensitivity analysis using propensity scores matching approach.

Results

Higher morphine concentration, assisted reproductive treatment, and multipara and cesarean section history were significantly more prevalent in the pruritus group than in the control group. The probabilities of pruritus at morphine concentrations of 10, 15, 20, 25, 30 and 40 μg/mL increased sequentially from 0.05, 0.1, 0.2, 0.35, 0.54 to 0.84, respectively. The trend remained steep in the ropivacaine stratum and became flatter when combined with levobupivacaine. At mild pain combined with levobupivacaine, the incidence of pruritus increased from 0.33 (95% confidence interval [CI] 0.1–0.68) in the 10 μg/mL morphine group to 0.48 (95% CI 0.1–0.88) in the 40 μg/mL morphine group. In the stratum of moderate pain combined with levobupivacaine, the incidence increased from 0.4 (95% CI 0.04–0.92) to 0.56 (95% CI 0.03–0.98). The results in the sensitivity analysis were in consistent with above findings.

Conclusions

Higher concentrations of morphine, multipara, and assisted reproductive treatment were factors associated with a higher probability of pruritus. Pain level or combined local anesthetics could moderate the association between morphine concentration and pruritus.

Comparison of epidural oxycodone and epidural morphine for post-caesarean section analgesia: A randomised controlled trial

Background and Aims:

Epidural morphine after caesarean section may cause moderate to severe pruritus in women. Epidural oxycodone has been shown in non-obstetric trials to reduce pruritus when compared to morphine. We hypothesised that epidural oxycodone may reduce pruritus after caesarean section.

Methods:

A randomised controlled trial was conducted in pregnant women at term who underwent caesarean section with combined spinal-epidural technique initiated with intrathecal fentanyl 15 μg. Women received either epidural morphine 3 mg or epidural oxycodone 3 mg via the epidural catheter after delivery. The primary outcome was the incidence of pruritus at 24 h after caesarean section. The secondary outcomes were the pruritus scores, treatment for post-operative nausea and vomiting (PONV), pain scores and maternal satisfaction.

Results:

One hundred women were randomised (group oxycodone O = 50, morphine M = 50). There was no difference between Group O and M in the incidence of pruritus (n [%] 28 [56%] vs. 31 [62%], P = 0.68) and the worst pruritus scores (mean [standard deviation] 2.6 (2.8) vs. 3.3 [3.1], P = 0.23), respectively. Both groups had similar pain scores at rest (2.7 [2.3] vs. 2.0 [2.7], P = 0.16) and sitting up (5.0 [2.3] vs. 4.6 [2.4], P = 0.38) at 24 h. Pruritus scores were lower at 4–8, 8–12 and 12–24 h with oxycodone, but pain scores were higher. Both groups had a similar need for treatment of PONV and maternal satisfaction with analgesia.

Conclusion:

There was no difference in the incidence of pruritus at 24 h between epidural oxycodone and morphine. However, pruritus scores were lower with oxycodone between 4 and 24 h after surgery with higher pain scores in the same period.

Systematic review of spinal anaesthesia using bupivacaine for ambulatory knee arthroscopy

The use of lidocaine in spinal anaesthesia is associated with transient neurological syndrome (TNS). Bupivacaine has a lower incidence of TNS as an alternative but it may have a prolonged action. This study systematically reviews the literature about the recovery profile of patients undergoing spinal anaesthesia, using bupivacaine for arthroscopic knee surgery. We identified 17 eligible randomized clinical trials (RCTs) (1268 patients). All the articles in this review, except one, used hyperbaric bupivacaine. Five trials compared different doses of bupivacaine (range 3-15 mg). Large doses of bupivacaine (10 and 15 mg) were associated with delayed recovery, and supine positioning was associated with a high incidence of failure. With unilateral positioning, a dose as low as 4-5 mg seems to be sufficient. Five trials comparing bupivacaine or levobupivacaine with ropivacaine showed no significant difference in the time to home discharge. When bupivacaine was combined with fentanyl in two trials, marginal delay in recovery was found [time to discharge (min); weighted mean difference (WMD) 14.1, 95% CI 11.9-40.1] and increased nausea and pruritus but had reduced postoperative pain. Unilateral and bilateral spinal anaesthesia were assessed in two trials, and the latter group was associated with early recovery and discharge [time to discharge (min); WMD -41.6, 95% CI -63.6 to -19.6). The results of our systematic review suggest that 4-5 mg of hyperbaric bupivacaine can effectively produce spinal anaesthesia for knee arthroscopy with unilateral positioning. Ropivacaine or the addition of adjuvants did not improve the recovery time. There is a need for tighter RCTs with more consistent endpoints.

The Combination of Low-Dose Levobupivacaine and Fentanyl for Spinal Anaesthesia in Ambulatory Inguinal Herniorrhaphy

This study investigated whether the addition of 25 μg intrathecal fentanyl to levobupivacaine spinal anaesthesia for outpatient inguinal herniorrhaphy allows a sub-anaesthetic levobupivacaine dose to be used. Forty patients were assigned to receive 5 mg levobupivacaine 0.5% mixed with 25 μg fentanyl (group LF) or 7.5 mg levobupivacaine 0.5% (group L). The highest sensory block levels achieved were T7 (range T5 – T9) and T6 (range T4 – T9) in groups LF and L, respectively. The times to two-segment regression, S2 regression, ambulation, urination and discharge were all significantly shorter in group LF than group L. These results indicate that, for outpatient inguinal herniorrhaphy, intrathecal fentanyl combined with low-dose levobupivacaine provides good quality spinal anaesthesia and minimizes the need for intra-operative analgesia. This protocol is well suited for the outpatient setting because it features rapid recovery of full motor power, sensory function and bladder function.

Advances in regional anesthesia for outpatients

PURPOSE OF REVIEW

This review will bring to the reader's attention recent developments in the literature regarding regional anesthesia in the outpatient setting, and allow the reader to evaluate whether these developments are appropriate for inclusion in clinical practice.

RECENT FINDINGS

The most stimulating developments in the area of regional anesthesia for outpatients revolve around the use of continuous analgesic therapy for outpatients after discharge. This is reflected in recent publications describing the use of continuous catheters for peripheral nerve blockade using portable pumps to provide 48-72 h of postoperative analgesia. These devices have raised the hope of opioid-free pain relief for virtually the entire duration of postsurgical pain in the outpatient setting. There are also increasing numbers of suggestions on ways to improve the quality of spinal anesthesia in the outpatient setting, particularly by using lower doses of lidocaine to reduce the problem of transient neurologic symptoms after spinal blockade. Several authors have investigated the cost implications of regional techniques in the outpatient setting, and have concluded that they are very competitive with the general anesthetic techniques that are frequently employed.

SUMMARY

Recent publications suggest additional ways to add regional anesthesia techniques to outpatient surgical practice, particularly with the promise of extensive postoperative pain relief for the ambulatory surgery patient.

Spinal 2-Chloroprocaine: A Comparison with Procaine in Volunteers

Recent studies using preservative-free 2-chloroprocaine (2-CP) for spinal anesthesia have shown it to be a reliable short-acting drug that provides similar anesthesia to lidocaine. In this randomized, double-blind, crossover study, we compared the characteristics of spinal 2-CP (30 mg) with those of procaine (80 mg) in eight volunteers to determine whether either drug produces spinal anesthetic characteristics ideal for outpatient surgery. By using sensation to pinprick, transcutaneous electrical stimulation, tolerance to thigh tourniquet, and motor blockade as surrogates for surgical efficacy, 2-CP compared similarly to procaine. Peak block height (T9 [range, T6 to T12] versus T6 [T4 to T8]; P = 0.0796), time to two-segment regression (51 +/- 17 min versus 53 +/- 10 min; P = 0.7434), tourniquet time tolerance (37 +/- 16 versus 49 min +/- 17 min; P = 0.1755), and time to return of motor strength (Bromage scale: 54 +/- 23 min versus 55 +/- 44 min, P = 0.9366; return of 90% quadriceps strength: 78 +/- 9 min versus 98 +/- 30 min; P = 0.0721) were all similar. Procaine did produce overall longer sensory blockade (P = 0.0011) and motor blockade at the gastrocnemius (P = 0.0004) and quadriceps (P = 0.0146) muscles. Times until the resolution of sensory blockade (103 +/- 12 min versus 151 +/- 26 min; P = 0.0003), ambulation (103 +/- 12 min versus 151 +/- 26 min; P = 0.0003), and micturition (103 +/- 12 min versus 156 +/- 23 min; P < 0.0001) were all prolonged after procaine. In conclusion, at the doses tested, spinal 2-CP (30 mg) may be a better choice for short outpatient procedures because it provides anesthesia with similar efficacy as procaine (80 mg) but with more rapid fulfillment of discharge criteria.

Regional anesthesia for outpatient surgery

In summary, regional techniques offer significant advantages in the outpatient setting. They can avoid the side effects of nausea, vomiting, and pain that frequently delay discharge or cause admission. They can also provide prolonged analgesia as well as offer, with the use of continuous catheters, the promise of a pain-free perioperative period. The choice of drugs must be carefully adjusted, especially with neuraxial techniques. Despite frequently requiring some additional time at the outset, regional techniques have consistently been shown to provide competitive discharge times and costs when compared with general anesthesia. They deserve a prominent place in outpatient surgery.

Low-dose bupivacaine plus fentanyl for spinal anesthesia during ambulatory inguinal herniorrhaphy: a comparison between 6 mg and 7. 5 mg of bupivacaine

BACKGROUND

Inguinal herniorrhaphy is commonly performed as an outpatient procedure. Spinal anesthesia offers some advantages over general anesthesia in this setting.

METHODS

Forty patients were randomly divided into two groups according to a double-blind protocol: Group L had spinal anesthesia with bupivacaine 6.0 mg and Group H with bupivacaine 7.5 mg; in both groups, fentanyl 25 micro g was added to the spinal anesthetic. The sensory block was measured by 'pin-prick' and the motor block was evaluated by a modified Bromage scale.

RESULTS

No differences were seen in the spread, duration and regression of sensory block between the groups on the operated side. A greater number of patients required analgesics during the operation in Group L (6) compared with Group H (1) (P<0.05). The return of the modified Bromage scale to grade 0 was earlier in Group L than in Group H (P<0.05) but the time to mobilization and discharge was similar. Seven patients (17%) needed to be catheterized and two had the catheter retained overnight. Times to home discharge (median) were 350 and 445 min, respectively, in Groups L and H. Postoperatively and during the first week, visual analog pain scores, analgesic requirements and side-effects were similar between the groups. In Group H, 95% of the patients and in Group L 85% would have the same anesthetic again if operated upon for a similar procedure.

CONCLUSIONS

Spinal anesthesia with bupivacaine 7.5 mg and fentanyl offers an alternative to general or local anesthesia for ambulatory inguinal herniorrhaphy. However, the long discharge times and risk for urinary retention restrict its routine use in all patients.

Minidose lidocaine-fentanyl spinal anesthesia in ambulatory surgery: prophylactic nalbuphine versus nalbuphine plus droperidol

Minidose lidocaine-fentanyl spinal anesthesia (SAB(MLF)) is a safe, effective, and efficient anesthetic for ambulatory surgery. Unfortunately, it has a frequent incidence of pruritus and a substantial incidence of nausea and vomiting. Nalbuphine is effective in treating or preventing pruritus after intrathecal or epidural morphine but may or may not have a beneficial effect on nausea and vomiting. Droperidol has demonstrated antiemetic efficacy with neuraxial opiates. In this study, we examined the prophylactic use of nalbuphine alone compared with nalbuphine with droperidol after SAB(MLF). One-hundred-twenty-four patients having outpatient knee arthroscopy under SAB(MLF) with 20 mg of lidocaine 0.5% and 20 micro g of fentanyl were randomized to receive IV at the end of surgery either 4 mg of nalbuphine (Group N) or droperidol 0.625 mg plus nalbuphine 4 mg (Group ND). The incidences of early (before discharge) and late onset nausea were, respectively, 18% versus 5% and 32% versus 13%. The postoperative incidences of pruritus were 61% versus 40%, whereas 19% of patients in Group N compared with 2% of patients in Group ND requested treatment for this. Group ND had lower pain scores and had a longer delay until first use of analgesic. There were no differences in average times to discharge. The only side effect of the medications was an increased drowsiness in Group ND. In conclusion, as prophylactic medication for use in conjunction with SAB(MLF), the addition of droperidol 0.625 mg to nalbuphine 4 mg was superior to nalbuphine alone. The combination provided for reduced postoperative nausea, pruritus, and pain-benefits that persisted after discharge home. The combination also avoided isolated cases of extreme delay in discharge.

IMPLICATIONS

Droperidol in combination with nalbuphine enhances analgesia and is more effective than nalbuphine alone in preventing pruritus, nausea, and vomiting after minidose lidocaine-fentanyl spinal anesthesia.

Prophylactic ondansetron reduces the incidence of intrathecal fentanyl-induced pruritus

We investigated the effectiveness of prophylactic IV ondansetron in preventing intrathecal fentanyl-induced pruritus. One-hundred-fifty ASA status I-II patients undergoing spinal anesthesia with 7-10 mg of hyperbaric bupivacaine and 25 micro g of fentanyl were randomized to receive ondansetron 8 mg IV or normal saline IV before the commencement of spinal anesthesia. Evaluations were performed every 15 min in the first hour after the injection of study drugs and at 1, 2, 3, 4, 5, and 6 h after the administration of the study drug. Statistical analysis was performed by using chi(2) tests and Student's t-test, as appropriate. The incidence of pruritus was significantly more frequent in the placebo group compared with the ondansetron group (68% versus 39%) (P = 0.001). Time to pruritus was similar in both groups (placebo group, 55 +/- 32 min versus ondansetron group, 50 +/- 31 min). Duration of pruritus was also similar in both groups (placebo group, 98 +/- 60 min versus ondansetron group, 103 +/- 58 min). Ondansetron prophylaxis significantly reduced the incidence of intrathecal fentanyl-induced pruritus in patients undergoing surgery under bupivacaine spinal anesthesia.

IMPLICATIONS

Pruritus is a commonly reported side effect after intrathecal fentanyl administration during spinal anesthesia. This study was performed in a prospective, randomized, double-blinded, placebo-controlled manner to investigate the efficacy of prophylactic IV ondansetron in the prevention of pruritus after intrathecal fentanyl administration during spinal anesthesia. The incidence of pruritus was significantly more frequent in the placebo group compared with the ondansetron group (68% versus 39%) (P = 0.001).