The efficacy of clonidine for reducing perioperative haemodynamic changes and volatile anaesthetic requirements in children

Comparison of Intranasal Dexmedetomidine with Intranasal Clonidine as a Premedication in Surgery

OBJECTIVES

To compare effectiveness of intranasal dexmedetomidine and clonidine as anxiolytics and sedatives in pediatric patients undergoing various surgeries.

METHODS

This double blind randomized placebo controlled study was conducted on 105 surgical patients of American Society of Anesthesiologist (ASA) physical status І-ІІ, aged between 2 and 9 y in a tertiary-care hospital (February 2014 to September 2015). Participants were randomly allocated to three groups to receive either intranasal dexmedetomidine 2 μg/kg (Group І) or intranasal clonidine 3 μg/kg (Group ІІ) or intranasal saline 0.5 ml (Group ІІІ). The primary outcome measure was proportion of patients with satisfactory anxiolysis and sedation at 30 min after drug administration. Secondary outcome measures included time taken to achieve Aldrete score of 9 and number of doses of rescue analgesia required in 12 h after surgery.

RESULTS

Satisfactory anxiolysis was achieved by 88.5% in Group І vs. 60% in Group ІІ (p = 0.001) and satisfactory sedation by 57.1% in Group І vs. 25.7% in Group ІІ (p = 0.001) 30 min after premedication. Rescue analgesia requirement was significantly less in Group І as compared to Group ІІ (p = 0.001) while time taken to achieve Aldrete score was comparable between the study groups (p = 0.185).

CONCLUSIONS

Intranasal dexmedetomidine is a better anxiolytic and sedative as compared to clonidine. Postoperative analgesic requirement was also significantly decreased after intranasal dexmedetomidine. Thus, it can be preferred as compared to clonidine for premedication in pediatric surgical patients.

Effect of intravenous clonidine premedication for the bloodless surgical field in patients undergoing middle ear or nasal surgery: A comparison of three different doses

Aim:

To evaluate the effect of intravenous (IV) clonidine premedication for the bloodless surgical field in patients undergoing middle ear or nasal surgery comparing three different doses.

Subjects and Methods:

This prospective randomized, clinical trial was performed on 90 normotensive patients belonging to American Society of Anesthesiologists grade I/II, aged 18–60 years, of either sex, undergoing routine middle ear or nasal surgery. These patients were divided into three Groups A, B, and C with 30 patients in each according to the dose of IV clonidine used as premedicant that is 3, 4, and 5 µg/kg, respectively. The hypotensive period commenced 10 min after the start of surgery till the surgeon's request for no hypotension required any longer. The target mean blood pressure for producing bloodless surgical field was 60–70 mmHg. During the hypotensive period, the surgeons were asked to rate the bleeding severity score on a six-point scale from 0 (no bleeding) to 5 (severe bleeding).

Statistical Analysis Used:

ANOVA, Chi-square test, Z-test, standard deviation and P value.

Results:

IV clonidine premedication in a dose of 4 and 5 µg/kg reduces bleeding and provides a clear field for surgery. It also reduces the requirement of isoflurane, fentanyl, and metoprolol for controlled hypotension. However, clonidine 5 µg/kg was not more effective than clonidine 4 µg/kg in producing these effects rather was associated with some side effects.

Conclusion:

IV clonidine premedication in a dose of 4 µg/kg is safe and effective for producing a bloodless surgical field in the middle ear and nasal surgery.

Continuous infusion of clonidine in ventilated newborns and infants: a randomized controlled trial

OBJECTIVES

To assess the influence of an infusion of clonidine 1 μg/kg/hr on fentanyl and midazolam requirement in ventilated newborns and infants.

DESIGN

Prospective, double-blind, randomized controlled multicenter trial. Controlled trials.com/ISRCTN77772144.

SETTING

Twenty-eight level 3 German PICUs/neonatal ICUs.

PATIENTS

Ventilated newborns and infants: stratum I (1-28 d), stratum II, (29-120 d), and stratum III (121 d to 2 yr).

INTERVENTIONS

Patients received clonidine 1 μg/kg/hr or placebo on day 4 after intubation. Fentanyl and midazolam were adjusted to achieve a defined level of analgesia and sedation according to Hartwig score.

MEASUREMENTS AND MAIN RESULTS

Two hundred nineteen infants were randomized; 212 received study medication, 69.7% were ventilated in the postoperative care and 30.3% for other reasons. Primary endpoint: consumption of fentanyl and midazolam in the 72 hours following the onset of study medication (main observation period) in the overall study population. The confirmatory analysis of the overall population showed no difference in the consumption of fentanyl and midazolam. Explorative age-stratified analysis demonstrated that in stratum I (n = 112) the clonidine group had a significantly lower consumption of fentanyl (clonidine: 2.1 ± 1.8 μg/kg/hr, placebo: 3.2 ± 3.1 μg/kg/hr; p = 0.032) and midazolam (clonidine: 113.0 ± 100.1 μg/kg/hr, placebo: 180.2 ± 204.0 μg/kg/hr; p = 0.030). Strata II (n = 43) and III (n = 46) showed no statistical difference. Sedation and withdrawal-scores were significantly lower in the clonidine group of stratum I (p < 0.001). Frequency of severe adverse events did not differ between groups.

CONCLUSIONS

Clonidine 1 μg/kg/hr in ventilated newborns reduced fentanyl and midazolam demand with deeper levels of analgesia and sedation without substantial side effects. This was not demonstrated in older infants, possibly due to lower clonidine serum levels.

Onset time for pharmacologic premedication with clonidine as a nasal aerosol: a double-blind, placebo-controlled, randomized trial

OBJECTIVES/AIM

To investigate whether nasal aerosol clonidine can reduce the onset time of preoperative sedation.

BACKGROUND

Premedication is common in the pediatric population, but the optimal agent and administration route is still a matter of debate. Clonidine has many beneficial effects in the perioperative period. Clonidine nasal drops produce a similar sedative effect as after oral administration but do not reduce the onset time. Nasal aerosol administration of drugs is generally more effective than drops and an option to decrease the onset time of clonidine.

METHODS

Pediatric ASA status 1 and 2 patients were randomized to receive placebo (P), clonidine 3-4 μg kg(-1) (C4), or clonidine 7-8 μg kg(-1) (C7) as a nasal aerosol. Acceptance of administration, pre- and postoperative sedation, and adverse events were assessed.

RESULTS

A total of 60 patients were enrolled with a median age of 3.5 years (range 0.7-6.9) and median weight of 14.8 kg (range 10-25). In the C7 group, 55% of the children were found adequately sedated at 30 min as compared to 32% in the C4 group (P = 0.1202). At 45 min, adequate sedation was seen in 65% of the patients in both C4 and C7 groups, which were both found to be significantly higher compared with the placebo control group (14%) (P-values = 0.0027 and 0.0013, respectively). The postoperative sedation profile did not differ between the three study groups.

CONCLUSIONS

Clonidine administered as nasal aerosol (3-8 μg kg(-1)) was not found to achieve adequate preoperative sedation within 30 min of administration. Despite its sedative properties, no prolongation of postoperative sedation was noted compared with placebo.

Dexmedetomidine: perioperative applications in children

Dexmedetomidine is a highly specific and selective alpha-2-adrenergic agonist with sedative, anxiolytic, and organ protective effects. Its clinical applications in children include premedication, prevention of emergence delirium, as part of multimodal anesthetic regimen and sedation in the pediatric intensive care unit. Its role in neuroprotection in children undergoing anesthesia should be explored. In this review, various uses of dexmedetomidine are discussed in detail.

Intravenous clonidine infusion in infants after cardiovascular surgery

BACKGROUND

The aim of this study was to investigate the hemodynamic profile and heart rhythm in infants who were given intravenous clonidine infusion after prolonged analgesia/sedation following cardiac surgery.

METHODS

This is a single center retrospective review. A total of 542 cardiovascular surgical procedures in infants aged 0-24 months with congenital heart disease were performed between 01/2003 and 12/2005 at the Deutsches Herzzentrum in Berlin. The majority received no long-term analgesia/sedation, but 50 (9%) of these infants received clonidine (dosed at 0.18-3.6 microg.kg(-1).h(-1)) for sedation and to reduce withdrawal symptoms such as CNS hyperactivation, hypertension, tachycardia, and fever. The hospital records of these infants were studied.

RESULTS

Fifty infants (median age 5.0 months, median body weight 5.3 kg, 32 males/18 females) received prolonged analgesia/sedation to ensure hemodynamic stability. Clonidine infusion started on day 5 (median) after surgery. During clonidine treatment we found an age-related normalized profile of hemodynamic parameters with a reduction of heart rate and mean arterial pressure from the upper norm to the mean within 24 h (P < 0.001). In no case did clonidine cause low blood pressure resulting in additional therapy to reach the target blood pressure. There were no adverse effects on cardiac rhythm, especially no onset of atrioventricular block. Midazolam, fentanyl, and other opioids could be ended on day 4 of clonidine treatment.

CONCLUSIONS

Although off-label, it is feasible to use clonidine infusions in infants in the PICU setting after cardiac surgery without hemodynamic problems arising.

Premedication in children: a comparison of oral midazolam and oral clonidine

BACKGROUND

Oral premedication is widely used in pediatric anesthesia to reduce preoperative anxiety and ensure smooth induction. Midazolam is currently the most commonly used premedicant, but good results have also been reported with clonidine. The aim of the present study was to compare clinical effects of oral midazolam and oral clonidine.

METHODS

We performed a prospective open study in 64 children who were randomly assigned to receive either oral midazolam 0.5 mg.kg (-1) (group M) or oral clonidine 4 microg.kg (-1) (group C) prior to mask induction. Drug acceptance, preoperative sedation and anxiolysis, quality of mask acceptance, recovery profile and parental satisfaction were evaluated.

RESULTS

The taste of oral clonidine was judged as significantly better; 14% of children rejected oral midazolam. Onset of sedation was significantly faster after premedication with midazolam (30+/-13.1 min) than with clonidine (38.5+/-14.6 min), but level of sedation was significantly better after premedication with clonidine. Quality of mask induction was equally successful in both groups. A steal-induction was performed in 66% of patients of group C, but none in group M. We observed a trend towards an increased incidence of emergence agitation after premedication with midazolam. Parental satisfaction was significantly higher in group C.

CONCLUSIONS

In this study, premedication with oral clonidine appeared to be superior to oral midazolam. Quality of mask acceptance was comparable between groups, but oral clonidine was better accepted by the child, produced more effective preoperative sedation, showed a trend towards better recovery from anesthesia and had a higher degree of parental satisfaction.

Steal-induction after clonidine premedication: a comparison of the oral and nasal route

BACKGROUND

Clonidine premedication in children reliably provides preoperative sedation and anxiolysis, but onset of oral clonidine is known to be slow. Nasal clonidine has been shown to reach peak plasma levels within 10 min in rodents. The aim of the present study was to compare clinical effects and percentage of steal-induction after clonidine premedication by the oral and nasal route.

METHODS

Forty children, aged 1-6 years, scheduled for minor infraumbilical surgery, were randomly assigned to receive either pure clonidine 4 microgxkg(-1) intranasally (group CN, n = 20) or clonidine 4 microgxkg(-1) orally in syrup (group CO, n = 20) prior to mask induction. Drug acceptance, preoperative sedation and anxiolysis, quality of mask acceptance, recovery profile and parents' satisfaction were evaluated.

RESULTS

Drug acceptance was similar between groups, but quality of taste was significantly better in the oral group. There was no significant difference of preoperative anxiolysis and sedation. The onset of sedative effect was after 38.3 min for oral clonidine and 47.5 min for nasal clonidine. A steal-induction could be performed in 60% of children in each group. Emergence from anesthesia and parents' satisfaction were comparable.

CONCLUSIONS

Intranasal clonidine administration has no advantage over the oral route. Clinical effects were similar with both routes; there was a trend towards a faster onset of sedation with oral clonidine. Clonidine premedication causes light sleep, which allows a steal-induction in 60% of patients.

Sensitive and convenient method for the quantification of clonidine in serum of pediatric patients using liquid chromatography/tandem mass spectrometry

An improved and easy to use liquid chromatography/tandem mass spectrometric (LC/MS/MS) method in human serum was developed for the quantification of clonidine (CLD), an alpha2-/alpha1-adrenoceptor agonist, used for analgo-sedation and the therapy of opioid withdrawal in pediatric patients. Sample preparation consisted of precipitation of serum proteins by adding acetonitrile and centrifugation of the sample subsequently. [(2)H4]Clonidine (CLD4) served as internal standard. Chromatographic separation of the supernatant was achieved using a 100mmx3mm, 5microm Thermo Electron BetaBasic C4 column with isocratic flow and elution consisting of 0.1% formic acid/acetonitrile (85/15, v/v) and a flow-rate of 350microl/min resulting in a column pressure of 280-420kPa. LC/MS/MS detection was performed by using a triple-stage quadrupole mass spectrometer (TSQ Quantum, Thermo Electron) working in selected reaction monitoring mode with positive electrospray ionization. The analyte was quantified in a single run within 5min. Linearity was demonstrated over the expected concentration range 0.15-50microg/l CLD. The lower limit of quantification (LLOQ) and the limit of detection were 0.1microg/l and 0.01microg/l, respectively. None of the drugs used concomitantly during analgesic therapy interfered in the assay in vitro. Intra-day precision expressed as RSD was 9.6% or less for CLD, while inter-day result was 10.0% or less for CLD. Intra-day and inter-day accuracy was within +/-4.9% and +/-1.8%, respectively. The method was validated according to the international guidelines of the International Conference on Harmonisation (ICH) and the US Food and Drugs Administration (FDA). The described method is suitable to analyse serum samples with very small volumes and sets the stage for pharmacokinetic studies in pediatric studies.

Clonidine: an alternative to benzodiazepines for premedication in children

PURPOSE OF REVIEW

The aim of this review is to summarize the use of clonidine for paediatric premedication and to make a comparison with benzodiazepines. A routine clonidine premedication protocol is also presented.

RECENT FINDINGS

In the US 50% of young children undergoing surgery receive premedication and midazolam is the most frequently used drug. The number of trials that compare midazolam with active controls are few and this premedicant is not adequately validated. Clonidine is still used as premedication in a small number of centres but the literature on paediatric use of clonidine is steadily growing. A recent review article has concluded that the use of clonidine does enhance the quality of perioperative management in infants and children and more recent publications support the use of clonidine for premedication. Its effect on the circulation is mild but routine atropine administration is recommended. Contraindications to the use of clonidine are few. Apart from a general overview on the effects of clonidine this article will also summarise the published trials that have compared clonidine with benzodiazepines for premedication in children.

SUMMARY

Midazolam the most commonly used drug for paediatric premedication worldwide. Despite having a number of beneficial effects it is far from an ideal premedicant, especially concerning its effect on cognition/amnesia, confusion and long-term behavioural disturbances. Clonidine lacks the majority of the negative effects associated with midazolam and is associated with a number of beneficial perioperative effects. Our clinical experience of replacing midazolam with clonidine as premedicant in children, including also outpatients, has been favourable.

Clonidine in paediatric anaesthesia: review of the literature and comparison with benzodiazepines for premedication

BACKGROUND

Children undergoing anaesthesia and surgery can experience significant anxiety and distress during the peri-operative period, but whether routine premedication is necessary is currently debated. Benzodiazepines are the most frequently used drugs as premedication in paediatric anaesthesia. In the US, 50% of young children undergoing surgery receive premedication and midazolam is the most frequently used drug in this context (1). Nishina and coworkers (2) concluded in a review article in 1999 that clonidine, administered via an oral, rectal, or caudal route, is a promising adjunct to anaesthetics and analgesics to enhance quality of peri-operative management in infants and children. Later publications also support the use of clonidine for premedication (3-6). The aim of this communication is to review the use of clonidine in paediatric anaesthesia and to propose clonidine as a promising alternative to midazolam. Clonidine is associated with a number of beneficial effects in the context ofanaesthesia both in adults and children. Why clonidine is not routinely use in clinical practice despite the massive publication list is to a large extent due to the lack of marketing efforts from the pharmaceutical industry since multiplegeneric preparations are now readily available on most markets. Midazolam is also associated with a number of beneficial effects, but is far from an ideal premedicant in children, especially with regards to the amnesia, confusion and long term behavioural disturbances. Clonidine has contrary to midazolam no effect on respiration. We believe that clonidine is a good alternative to midazolam as premedication in infants and children.

Clonidine facilitates controlled hypotension in adolescent children

In this randomized, double-blinded, placebo-controlled trial, we investigated whether clonidine lessened the requirements for isoflurane, fentanyl, and labetalol to provide controlled hypotension in children who underwent oromaxillofacial surgery. We also studied preoperative sedative effects, the hemodynamic response to nasotracheal intubation, and recovery characteristics. Thirty-nine healthy children, aged 10-16 yr, received clonidine 5 micro g/kg or placebo on the night before surgery and 90 min before surgery. By self-assessment, children in both groups showed similar anxiety, whereas observers rated clonidine patients as more sedated (P < 0.01). Heart rate during induction remained significantly decreased in clonidine patients compared with placebo patients (P < 0.001), as did arterial blood pressure before induction (P < 0.01) and peak pressure after intubation (P < 0.001). Children who took clonidine required significantly less isoflurane to maintain a mean arterial blood pressure of 60 +/- 4 mm Hg (mean isoflurane concentration, clonidine 0.99% versus placebo 1.33; P = 0.0004) and required less fentanyl than placebo patients (P = 0.002). Fewer treatment patients received labetalol (clonidine, n = 3 versus placebo, n = 13; P = 0.004). There was a trend toward faster recovery in the clonidine group, with a shortened recovery room stay (P = 0.03). We conclude that clonidine is a useful adjunct for controlled hypotension in children.

IMPLICATIONS

This study shows that adolescents having major jaw surgery are helped by the blood pressure-decreasing drug clonidine. This drug allows smaller doses of anesthetics, pain relievers, and blood pressure-decreasing drugs to be used; reduces changes in heart rate and blood pressure; and provides faster recovery from the anesthetic.

The reduction in minimum alveolar concentration for tracheal extubation after clonidine premedication in children

The effects of clonidine on minimum alveolar concentration for tracheal extubation (MAC-ex) have not been elucidated. Clonidine may lead to prolonged emergence from anesthesia. We investigated the effects of oral clonidine premedication on MAC-ex and examined the emergence properties of sevoflurane in children. Sixty ASA physical status I pediatric patients, aged from 2 to 9 yr, were randomly divided into one of three groups and received placebo, clonidine 2 microg/kg, or clonidine 4 microg/kg (n = 20 each) orally, 100 min before the induction of anesthesia. The induction of anesthesia, tracheal intubation, and maintenance of anesthesia were performed with sevoflurane in air and oxygen. MAC-ex was defined according to the modification of Dixon's up-and-down method, with 0.25% as a step size. In addition, in the Control and 4 microg/kg groups, the time from tracheal extubation to spontaneous eye opening (eye-opening time) and the time from tracheal extubation to leaving the operating room (awakening time) were recorded. MAC-ex for sevoflurane (mean +/- SD) was 1.63% +/- 0.13%, 1.04% +/- 0.26%, and 0.66% +/- 0.09% respectively in the Control group, 2 microg/kg group, and 4 microg/kg group. Significant differences were observed among the three groups. The eye-opening times were 5.7 +/- 3.5 min in the Control group and 5.1 +/- 1.0 min in the 4 microg/kg group. The awakening times were 9.7 +/- 3.7 min in the Control group and 9.2 +/- 3.8 min in the 4 microg/kg group. No significant differences were observed among the groups.

IMPLICATIONS

Oral clonidine premedication decreased MAC for tracheal extubation for sevoflurane dose dependency and did not prolong emergence from anesthesia.

Premedication and parental presence revisited

Up to 60% of all children undergoing anesthesia and surgery experience significant anxiety and distress during the perioperative period. Currently, both behavioral interventions such as parental presence during induction of anesthesia and pharmacological interventions such as sedative premedication are used to treat this clinical phenomenon. In this review, we examine the effectiveness of these interventions on clinically relevant perioperative outcomes.

Ropivacaine-clonidine combination for caudal blockade in children

BACKGROUND

Adding clonidine to weak ropivacaine solutions (<0.2%) could potentially enhance analgesia as well as further reduce the risk for unwanted motor blockade. The aim of the present study was to compare the postoperative pain-relieving quality of a ropivacaine 0.1%-clonidine mixture to that of plain ropivacaine 0.2% following caudal administration in children.

METHODS

In a prospective, observer-blinded fashion, 40 ASA 1 paediatric patients undergoing subumbilical surgery were randomly allocated to receive a caudal injection of either plain ropivacaine 0.2% (1 ml/kg) (R0.2) or a mixture of ropivacaine 0.1% with clonidine 2 microg/kg (1 ml/kg) (R0.1C). Objective pain scale score and need for supplemental analgesia were used to evaluate analgesia during the first 24 h postoperatively. Residual postoperative sedation was also assessed.

RESULTS

A significantly higher number of patients in the R0.1C group (18/20) could be managed without supplemental analgesia during the first 24 h postoperatively compared to the R0.2 group (11/20) (P=0.034). Both the degree and the duration of postoperative sedation was similar in both groups. No signs of postoperative motor blockade were observed.

CONCLUSIONS

The combination of clonidine (2 microg/kg) and ropivacaine 0.1% is associated with an improved quality of postoperative analgesia compared to plain 0.2% ropivacaine. The improved analgesic quality of the clonidine-ropivacaine mixture is achieved without causing any significant degree of postoperative sedation.

Influence of intravenous clonidine pretreatment on anesthetic requirements during bispectral EEG-guided sevoflurane anesthesia

STUDY OBJECTIVE

To assess the anesthetic effects of clonidine during sevoflurane anesthesia guided by the bispectral index (BIS), which is a processed EEG variable correlated with anesthetic-hypnotic depth.

DESIGN

Placebo-controlled, double-blind clinical trial.

SETTINGS

Elective laparoscopic surgery.

PATIENTS

60 ASA physical status I patients scheduled for laparoscopic surgery.

INTERVENTIONS

Patients received either clonidine (3 micrograms/kg, 15 min before induction) or placebo premedication for a sevoflurane-induced and sevoflurane-maintained anesthesia. Sevoflurane was titrated against a BIS held between 40 and 50. Analgesia was provided by local infiltration with bupivacaine. Need for postoperative analgesia was recorded.

RESULTS AND CONCLUSION

Mean sevoflurane requirements were not lower with clonidine pretreatment. There was statistically better perioperative hemodynamic stability (i.e., fewer episodes of hypertension and tachycardia) without clinical relevance. A decreased need for postoperative analgesia was observed.

The effects of clonidine premedication on sevoflurane requirements and anesthetic induction time

We assessed the effects of oral clonidine preanesthetic medication (4.5 microg/kg) on the vital capacity rapid-inhalation anesthetic induction time (VCRII time) and minimum alveolar anesthetic concentration (MAC) to prevent a response to a verbal command in 50% of patients (MAC-Awake) by its hypnotic effect, and on MAC-Skin incision for the analgesic effect in patients anesthetized with sevoflurane. We studied 104 adult patients (control group: n = 52, clonidine group: n = 52) aged 30-48 yr scheduled to undergo general anesthesia. Fifty-two patients received oral clonidine 4.5 microg/kg 1.5 h before arrival in the operating room (clonidine group). The patients exhaled to residual volume and took three vital capacity breaths of 5% sevoflurane in oxygen. The VCRII time was defined as the time interval between the initiation of the VCRII and the disappearance of the response to verbal command. Anesthesia was maintained with sevoflurane in oxygen and air. The end-tidal (ET) sevoflurane concentration reached a predetermined value, then the ratio of predetermined ET to inspiratory concentration was maintained at > or =0.95 for at least 15 min before skin incision. After skin incision, the patients were observed for gross purposeful muscular movements. MAC was defined as the average of the cross-over midpoints in each cross-over. After maintaining the ET sevoflurane concentration for 15 min, patients were judged to be awake or asleep. Average times for VCRII using 5% sevoflurane were achieved in 44+/-11 s (mean +/- SD) and 27+/-6 s in the control and clonidine groups, respectively (P = 0.0001). MAC-Awake values of sevoflurane were 0.66%+/-0.03% and 0.35%+/-0.02% (P = 0.0001), and MAC-Skin incision values were 1.97%+/-0.19% and 1.29%+/-0.13% (P = 0.0001) in the control and clonidine groups, respectively. These results suggest that clonidine may have a more potent hypnotic effect than analgesic effect.

IMPLICATIONS

Oral clonidine preanesthetic medication (4.5 microg/kg) significantly reduces vital capacity rapid inhalation anesthetic induction time and minimum alveolar anesthetic concentration awake for sevoflurane.

Plasma levels of clonidine following epidural bolus injection in children

BACKGROUND

The use of clonidine as an adjunct to epidural administration of local anesthetics in children has been reported to substantially improve the duration and quality of postoperative analgesia. The aims of the present study were to determine the pharmacokinetic profile and to investigate the interaction between postoperative sedation and analgesia after epidurally administered clonidine in children.

METHODS

Plasma levels of clonidine (0-10 h postop) and assessment of postoperative analgesia and sedation (0-24 h postop) were performed at predetermined intervals following lumbar epidural administration of bupivacaine 2.0 mg/kg and clonidine 2 mg/kg in 8 children undergoing ureteral re-implantation surgery using general anesthesia (age range: 1-9 yr, weight range: 9-41 kg). Plasma levels of clonidine were analyzed by radioimmunoassay, and sedation and analgesia were assessed by previously described scoring systems.

RESULTS

The venous plasma pharmacokinetics of clonidine following epidural administration showed a considerable interindividual variation. Cmax and Tmax values of clonidine were found to be within the 0.45-0.77 ng/mL and 48-193 min range, respectively. The time to absorb 95% of the clonidine dose from the epidural space into plasma varied between 36 min and 7.6 h. In 6 of the 8 patients postoperative analgesia substantially outlasted the duration of sedation (> or = 2 h). Sedation could not be detected in any patients at plasma concentrations below 0.3 ng/mL.

CONCLUSIONS

The pharmacokinetic profile associated with epidural clonidine administration in children (1-9 y) was similar to that previously reported in adults. The postoperative analgesia seen after administration of epidural bupivacaine-clonidine during general anesthesia in children cannot only be explained by residual postoperative sedation.