Plasma lidocaine concentrations during continuous thoracic epidural anesthesia after clonidine premedication in children

Comparison of bupivacaine alone and in a combination with lidocaine for caudal block in patients undergoing circumcision: A historical cohort study

OBJECTIVE

Optimal analgesia following ambulatory surgery is an important matter in patient satisfaction, and it reduces unnecessary hospital admissions. This study investigated whether a caudal block with bupivacaine alone or in a combination with lidocaine can alter postoperative pain scores, complications, and peroperative and postoperative analgesic consumption.

MATERIAL AND METHODS

This is a retrospective study that included children who underwent elective circumcision surgery under general anesthesia and caudal analgesia between January and June 2018. Among the 103 children, 17 cases were not analyzed due to an unsuccessful caudal block and procedures simultaneously underwent another operation unrelated to circumcision. We divided the study participants into two groups according to the type of local anesthetic applied: 0.5 mL/kg 0.25% bupivacaine (Group B) and 0.5 mL/kg 0.25% bupivacaine + 3 mg/kg 1% lidocaine (Group BL) caudally.

RESULTS

Pain scores were similar between these groups and remained in the mild-to-moderate range throughout the hospitalization (p>0.05). There were significant differences regarding the rescue analgesic use, first micturition, and mobilization times (p<0.001). In addition, we applied the multivariable logistic regression for fentanyl consumption adjusted for first mobilization and micturition time, unlike mobilization, a significantly increased risk for postoperative delayed micturition (OR, 1.06; 95% CI, 1.0-1.12; p=0.038) was found with intra-operative intravenous fentanyl use.

CONCLUSION

Our results suggest that the caudal block with a lidocaine+bupivacaine combination decreases rescue analgesic consumption at day-case surgery. In circumcision procedures, the caudal block is an effective and safe analgesic method for intraoperative and postoperative pain control with no side effects. This trial was registered at Clinicaltrals.gov, NCT03911648.

Absorption characteristics of epidural levobupivacaine with adrenaline and clonidine in children

AIM

To determine if the addition of adrenaline, clonidine, or their combination altered the pharmacokinetic profile of levobupivacaine administered via the caudal epidural route in children.

METHODS

Children aged <18 years old scheduled to undergo sub-umbilical surgery were administered caudal levobupivacaine plain 2.5 mg · ml(-1) or with adjuvants adrenaline 5 mcg · ml(-1) or clonidine 2 mcg · ml(-1) or their combination. Covariate analysis included weight and postnatal age (PNA). Time-concentration profile analysis was undertaken using nonlinear mixed effects models. A one-compartment linear disposition model with first-order input and first-order elimination was used to describe the data. The effect of either clonidine or adrenaline on absorption was investigated using a scaling parameter (Fabs(CLON), Fabs(ADR)) applied to the absorption half-life (Tabs).

RESULTS

There were 240 children (median weight 11.0, range 1.9-56.1 kg; median postnatal age 16.7, range 0.6-167.6 months). Absorption of levobupivacaine was faster when mixed with clonidine (Fabs(CLON) 0.60; 95%CI 0.44, 0.83) but slower when mixed with adrenaline (Fabs(ADR) 2.12; 95%CI 1.45, 3.08). The addition of adrenaline to levobupivacaine resulted in a bifid absorption pattern. While initial absorption was unchanged (Tabs 0.15 h 95%CI 0.12, 0.18 h), there was a late absorption peak characterized by a Tabs(LATE) 2.34 h (95%CI 1.44, 4.97 h). The additional use of clonidine with adrenaline had minimal effect on the bifid absorption profile observed with adrenaline alone. Neither clonidine nor adrenaline had any effect on clearance. The population parameter estimate for volume of distribution was 157 l 70 kg(-1). Clearance was 6.5 l · h(-1) 70 kg(-1) at 1-month PNA and increased with a maturation half-time of 1.6 months to reach 90% of the mature value (18.5 l · h(-1) 70 kg(-1)) by 5 months PNA.

CONCLUSIONS

The addition of adrenaline decreases the rate of levobupivacaine systemic absorption, reducing peak concentration by half. Levobupivacaine concentrations with adrenaline adjuvant were reduced compared to plain levobupivacaine for up to 3.5 hours. Clonidine as an adjuvant results in faster systemic absorption of levobupivacaine and similar concentration time profile to levobupivacaine alone. Adding adrenaline with clonidine does not alter the concentration profile observed with adrenaline alone.

Pharmacology in the very young: anaesthetic implications

Anaesthesia dosing in infants (0-2 years) should be based on pharmacokinetic-pharmacodynamic considerations and adverse effects profiles. Disease processes and treatments in this group are distinct from those in adults. Absorption, distribution and clearance change dramatically during this period because of maturation of anatomical and physiological processes as well as behavioural changes. Pharmacogenomic expression also matures in this period. Population-based and physiological-based pharmacokinetic modelling has improved the understanding of maturation and subsequent dose approximation. Postmenstrual, rather than postnatal, age is a reasonable measure for maturation. There remains a need for clinically applicable tools to assess pharmacodynamics which can provide response feedback; this has been achieved for neuromuscular monitoring, but not yet fully for depth of anaesthesia, sedation or pain. Morbidity and mortality associated with paediatric anaesthesia have historically been highest in this age group and continue to be so. Some of this morbidity was attributable to a poor understanding of developmental pharmacology; this facet continues to plague the specialty.

Clonidine--a potent analgesic adjuvant

PURPOSE OF REVIEW

The alpha(2)-adrenoceptor agonist clonidine is one of the most widely investigated substances in anaesthesia and pain therapy. Recently, numerous experimental and clinical studies have allowed a better understanding of its underlying mechanisms of action and interactions with other analgesic drugs.

RECENT FINDINGS

Several experimental studies have shown that clonidine may improve the analgesic effect of anti-inflammatory agents and also have significant peripheral antinociceptive effects. Volunteer and clinical studies have demonstrated analgesic effects of clonidine after systemic administration, whereas local administration of plain clonidine (e.g. intra-articular, intravenous regional) showed only limited clinical efficacy. The major clinical place of clonidine may thus be as an adjuvant to other analgesics, as shown in a number of studies in which clonidine has been investigated in combination with local anaesthetics, opioids and ketamine. An increasing number of studies have now investigated clonidine in paediatric patients and have demonstrated that the effects are generally similar to those in adults. Furthermore, it seems that in paediatric patients the side-effects of clonidine are predictable and of limited clinical importance.

SUMMARY

During the past decade clonidine has been investigated as an adjuvant for general and regional anaesthesia and in the postoperative period. There is no doubt that clonidine improves analgesia after systemic, spinal or peripheral opioids, and prolongs the analgesic action of most local anaesthetics. The side-effects of usual doses of clonidine are predictable. Given the clinical experience of an increasing number of hospitals, clonidine should no longer be considered an experimental drug, but a useful addendum to the pharmacological armamentarium.

A study of the in vitro interaction between lidocaine and premedications using human liver microsomes*

OBJECTIVE

To investigate potential interactions between lidocaine (lignocaine) metabolism and premedication drugs, i.e. psychotropic and antianxiety agents (diazepam, midazolam), hypnotics (pentobarbital, thiamylal), depolarizing neuromuscular blocking agents (vecuronium, pancuronium and suxamethonium), an antihypertensive agent (clonidine) and an H2-receptor blocking agent (cimetidine) using human liver microsomes in vitro.

METHODS

The interaction effects between lidocaine and premedication were examined using human liver microsomal preparations and monitored for enzyme activity. The lidocaine and its main metabolite (monoethylglycinexylide) were measured by HPLC/UV.

RESULTS

Lidocaine metabolism was non-competitively inhibited by midazolam (Ki = 77.6 microM). Thiamylal was a competitive inhibitor of lidocaine metabolism (Ki = 885 microM). Cimethidine, pancuronium and vecuronium weakly inhibited lidocaine metabolism in a concentration-depend manner over the therapeutic range in human liver microsomes. On the contrary, suxamethonium, pentobarbital and clonidine did not inhibit lidocaine metabolism over the therapeutic range in human liver microsomes.

CONCLUSION

These results show that the interactions between lidocaine and midazolam and thiamylal are of potential toxicological and clinical significance.

Clonidine in paediatric anaesthesia

PURPOSE OF REVIEW

This review aims to summarize results of recently published studies concerning clonidine application in paediatric anaesthesia, to analyse trends in these studies, and to discuss perspectives of the perioperative use of clonidine for children.

RECENT FINDINGS

Reassessment of clonidine premedication has revealed that oral clonidine is inferior to midazolam for preoperative sedation. Oral or intravenous clonidine has been successfully used for the prevention of sevoflurane-induced agitation during emergence from anaesthesia. Peripheral injection or caudal (epidural) administration of clonidine prolonged the duration and enhanced the quality of postoperative analgesia by local anaesthetics without severe side effects. However, some negative results concerning potentiation of postoperative analgesia with clonidine have been reported.

SUMMARY

Clonidine may be less favored than midazolam as premedication for children because of inferior clonidine-induced sedation. Additional comparative studies are required, however, to confirm this finding. On the other hand, clonidine-induced analgesia may well be useful and find wide application in paediatric anaesthesia. Prospective multicentre trials using a larger number of patients will be needed to verify the usefulness of caudal clonidine for postoperative pain relief. Prophylactic use of clonidine against sevoflurane-induced agitation may represent a new and promising application. Assessment of the efficacy of clonidine in potentiating regional anaesthesia/analgesia by local anaesthetics in children also needs more investigation. Moreover, it may be worthwhile to try new successful applications demonstrated in adults for paediatric anaesthesia.