Associations of dexamethasone's effect on morphine consumption after total knee arthroplasty-Subgroup analyses

The DEXamethasone twice for pain treatment after Total Knee Arthroplasty (DEX-2-TKA) trial showed that adding one and two doses of 24 mg intravenous dexamethasone to paracetamol, ibuprofen and local infiltration analgesia, reduced morphine consumption (primary outcome) within 48 h after TKA. We aimed to explore the differences in the effect of dexamethasone on morphine consumption in different subgroups. Quantile regression adjusted for site was used to test for significant interaction between the predefined dichotomised subgroups and treatment group. The subgroups were defined based on baseline data: sex (male/female), age (≤65 years/>65 years), American Society of Anaesthesiologists (ASA)-score (ASA I + II/III), visual analogue score of preoperative pain at rest (≤30 mm/>30 mm), pain during mobilisation (≤30 mm/>30 mm), type of anaesthesia (spinal anaesthesia/general anaesthesia and spinal converted to general anaesthesia), and prior daily use of analgesics (either paracetamol and/or NSAID/neither). These analyses were supplemented with post hoc multivariate linear regression analyses. Test of interaction comparing sex in the pairwise comparison between DX2 (dexamethasone [24 mg] + dexamethasone [24 mg]) versus placebo (p = .02), showed a larger effect of dexamethasone on morphine consumption in male patients compared to females. Test of interaction comparing age in the pairwise comparison between DX1 (dexamethasone [24 mg] + placebo) versus placebo (p = .04), showed a larger effect of dexamethasone on morphine consumption in younger patients (≤65 years) compared to older. All remaining subgroup analyses showed no evidence of a difference. The supplemental multivariate analyses did not support any significant interaction for sex (p = .256) or age (p = .730) but supported a significant interaction with the type of anaesthesia (p < .001). Our results from the quantile regression analyses indicate that the male sex and younger age (≤65 years) may be associated with a larger analgesic effect of dexamethasone than the effects in other types of patients. However, this is not supported by post-hoc multivariate linear regression analyses. The two types of analyses both supported a possible interaction with the type of anaesthesia.

DEX-2-TKA-DEXamethasone twice for pain treatment after Total Knee Arthroplasty: A protocol for a randomized, blinded, three-group multicentre clinical trial

BACKGROUND

Multimodal analgesia is considered the leading principle for post-operative pain treatment, but no gold standard after total knee arthroplasty (TKA) exists.

AIM

To investigate the beneficial and harmful effects of one or two doses of 24 mg intravenous dexamethasone (DXM) as part of a multimodal analgesic regimen (paracetamol, NSAID and perioperative local infiltration analgesia) after TKA. We hypothesize that addition of DXM will reduce post-operative opioid consumption.

METHODS

DEXamethasone twice for pain treatment after TKA is a randomized, blinded, three-group multicentre clinical trial. Participants will be randomized to one of three groups: placebo, single dose of DXM or two consecutive doses of DXM. Participants, treatment providers and investigators will be blinded to the allocated intervention. The primary outcome is total opioid consumption (units of morphine equivalents) 0-48 hours post-operatively.

INCLUSION CRITERIA

unilateral, primary TKA; age ≥18 years; American Society of Anesthesiologists-Score 1-3; Body Mass Index ≥18 and ≤40; for women-not pregnant; and written informed consent.

EXCLUSION CRITERIA

allergy or contraindications against trial medication; daily use of high dose opioid and/or use of methadone/transdermal opioids; daily use of systemic glucocorticoids; dysregulated diabetes; and patients suffering from alcohol and/or drug abuse. Four-hundred-and-eighty-six eligible participants are needed to detect or discard a difference of 10 mg morphine equivalents 0-48 hours post-operatively maintaining a familywise error rate of 0.05 and a power of 90% for the three possible pairwise comparisons.

DISCUSSION

Recruiting is planned to commence September 2018 and expected to finish March 2020.

TRIAL REGISTRATION

EudraCT: 2018-001099-39 (08/06-18); ClinicalTrials.gov: NCT03506789 (24/04-2019). Editorial Comment This is the protocol for the largest randomized clinical trial investigating the effect of one or two doses of dexamethasones on pain treatment after total knee arthroplasty. Due to the pragmatic and rigerous design this study will deliver results of high quality and external validity.

A randomized, controlled trial comparing local infiltration analgesia with epidural infusion for total knee arthroplasty

BACKGROUND

There have been few studies describing wound infiltration with additional intraarticular administration of multimodal analgesia for total knee arthroplasty (TKA). In this study, we assessed the efficacy of wound infiltration combined with intraarticular regional analgesia with epidural infusion on analgesic requirements and postoperative pain after TKA.

METHODS

40 consecutive patients undergoing elective, primary TKA were randomized into 2 groups to receive either (1) intraoperative wound infiltration with 150 mL ropivacaine (2 mg/mL), 1 mL ketorolac (30 mg/mL), and 0.5 mL epinephrine (1 mg/mL) (total volume 152 mL) combined with intraarticular infusion (4 mL/h) of 190 mL ropivacaine (2 mg/mL) plus 2 mL ketorolac (30 mg/mL) (group A), or (2) epidural infusion (4 mL/h) of 192 mL ropivacaine (2 mg/mL) combined with 6 intravenous administrations of 0.5 mL ketorolac (30 mg/mL) for 48 h postoperatively (group E). For rescue analgesia, intravenous patient-controlled-analgesia (PCA) morphine was used. Morphine consumption, intensity of knee pain (0–100 mm visual analog scale), and side effects were recorded. Length of stay and corrected length of stay were also recorded (the day-patients fulfilled discharge criteria).

RESULTS

The median cumulated morphine consumption, pain scores at rest, and pain scores during mobilization were reduced in group A compared to group E. Corrected length of stay was reduced by 25% in group A compared to group E.

INTERPRETATION

Peri- and intraarticular analgesia with multimodal drugs provided superior pain relief and reduced morphine consumption compared with continuous epidural infusion with ropivacaine combined with intravenous ketorolac after TKA.

Pharmacokinetics and pharmacodynamics of mivacurium in patients phenotypically heterozygous for the usual and atypical plasma cholinesterase variants (UA)

BACKGROUND

Mivacurium is hydrolyzed by plasma cholinesterase (pChe). The purpose of this study was to evaluate the pharmacodynamics and the pharmacokinetics of the three isomers of mivacurium in patients phenotypically heterozygous for the usual and the atypical pChe variant (UA).

METHODS

Thirty-two patients were included in a dose-response study, in which the patients received one of four doses of mivacurium. An additional bolus dose of mivacurium, to a total of 0.1 mg kg-1, was given followed by a continuous infusion adjusted to maintain 91-99% neuromuscular block. The times to different levels of recovery following the infusion were measured using mechanomyography and train-of-four (TOF) nerve stimulation. Twelve of the patients with an estimated duration of anaesthesia of more than 90 min were (randomly) selected for the pharmacokinetic part of the study. Venous samples were taken for determination of the three isomers of mivacurium. These results were compared with results from a previous study in phenotypically normal patients (UU).

RESULTS

The estimated ED50 and ED95 were 24 and 69 microg kg-1, respectively. The median (range) infusion rate was 3.7 microg kg-1 min-1 (1.2-2.9) and the time to a TOF ratio of 0.7 was 29.8 min (16.1-44.8). The median clearances of the cis-cis, cis-trans and trans-trans isomers were 3.7, 29 and 28 ml kg-1 min-1, respectively. The elimination half-lives of the isomers were 45, 6.7 and 6.3 min, respectively.

CONCLUSION

In patients heterozygous for the usual and the atypical variant (UA), the potency of mivacurium is higher, the infusion requirements lower and the rate of spontaneous recovery prolonged, compared with phenotypically normal patients. The clearances of the active isomers are significantly lower and the elimination half-lives longer in heterozygous patients than in phenotypically normal patients (UU). The pharmacokinetics of the inactive cis-cis isomer was not affected.

Pharmacokinetics and pharmacodynamics of mivacurium in young adult and elderly patients

BACKGROUND

Mivacurium is hydrolyzed by plasma cholinesterase, and is therefore less dependent on liver metabolism and renal elimination than other neuromuscular blocking drugs. This might favor the use of mivacurium in elderly patients. The purpose of this study was to compare the pharmacodynamics and the pharmacokinetics of the three isomers of mivacurium and their metabolites in young adult and elderly patients.

METHODS

Sixty-four patients were included in a dose-response study, in which 32 young adults and 32 elderly patients received one of four doses of mivacurium. An additional bolus dose of mivacurium to a total of 0.1 mg/kg was given followed by a continuous infusion adjusted to maintain a 91-99% neuromuscular block. The times to maximum block and different levels of recovery were measured using mechanomyography and train-of-four (TOF) nerve stimulation. Thirty-two patients were randomly selected for the pharmacokinetic study. Venous samples were taken for determination of the three mivacurium isomers and the metabolites.

RESULTS

The estimated ED95 were 0.053 and 0.061 mg/kg in young adults and elderly patients, respectively (NS). The median infusion rate did not differ, but duration to a TOF ratio of 0.7 was significantly longer in elderly patients than in young adult patients (21.0 vs. 16.5 min). No statistically significant difference between the age groups in clearance and elimination half-life of the isomers was seen. The half-lives of the metabolites were significantly prolonged in the elderly patients.

CONCLUSION

There were no significant differences in the potency or infusion requirements between the adult and elderly patients, but the rate of recovery was significantly, though only moderately prolonged, in the elderly patients. No significant difference in clearance was seen but the elimination half-lives of the metabolites was longer in the elderly patients.

[Infusion of mivacurium and atracurium guided by manual tactile evaluation]

INTRODUCTION

The aim of this investigation was to compare the use of a continuous infusion of mivacurium or atracurium guided by tactile evaluation of the neuromuscular block.

MATERIALS AND METHODS

Forty-five patients were randomly allocated to three groups of patients. Group M and MN received a bolus dose of mivacurium 0.15 mg/kg followed by a continuous infusion and group AN a bolus dose of atracurium 0.4 mg/kg followed by an infusion.

RESULTS

The neuromuscular blockade recovered spontaneously in group M and was antagonised in group MN and AN. The level of block was quantified by tactile evaluation. The time to full recovery was significantly shorter in patients receiving mivacurium compared to patients given atracurium, 14.5, 12.0 and 18.0 min, respectively. Further, reversal with neostigmine significantly enhanced recovery following mivacurium.

CONCLUSION

A continuous infusion of mivacurium and atracurium can easily be performed, guided by tactile evaluation of the neuromuscular block and the effect can be reversed by neostigmine.

The influence of drug-induced low plasma cholinesterase activity on the pharmacokinetics and pharmacodynamics of mivacurium

BACKGROUND

The short duration of action of mivacurium results from its rapid hydrolysis by plasma cholinesterase. Bambuterol, an oral bronchodilator, has an inhibiting effect on plasma cholinesterase. The purpose of this study was to evaluate the effect of bambuterol-induced low plasma cholinesterase activity on the pharmacokinetics and pharmacodynamics of mivacurium.

METHODS

Fourteen patients received 20 mg bambuterol and 14 patients received placebo orally 2 h before induction of anesthesia. During anesthesia the neuromuscular block was monitored at the thumb using train-of-four nerve stimulation every 12 s and mechanomyography. The times to different levels of neuromuscular recovery after 0.2 mg/kg mivacurium were measured. The concentrations in venous blood of the three isomers and the metabolites of mivacurium were measured using high-performance liquid chromatography.

RESULTS

Plasma cholinesterase activity was inhibited a median of 90% (range, 67-97%) after bambuterol. The time to first response to train-of-four nerve stimulation was 15 min (range, 9-21 min) and 59 min (range, 32-179 min) in patients receiving placebo and bambuterol, respectively. The estimated clearances of the isomers were significantly lower and the elimination half-lives of all three isomers significantly prolonged in patients receiving bambuterol. No difference was seen in elimination half-lives of the metabolites. The elimination rate constant from the effect compartment and the potency of mivacurium was not affected by bambuterol.

CONCLUSION

A 90% inhibition of plasma cholinesterase activity significantly reduced clearance of the isomers of mivacurium. Correspondingly, the duration of action of 0.2 mg/kg mivacurium was prolonged three- to fourfold, compared with patients not administered bambuterol.

Clinical importance of plasma cholinesterase for the anaesthetist

Plasma cholinesterase is a glycoprotein synthesized in the liver and is found in plasma, liver, intestinal mucosa and other tissues. Six percent to 7% of patients in most surgical populations have an abnormal plasma cholinesterase activity and about 65% of all cases of prolonged neuromuscular blockade following succinylcholine are due to genetic factors. This review focuses on the causes and clinical significance of plasma cholinesterase for the hydrolyses of succinylcholine. Diagnosis and treatment of prolonged response to succinylcholine in phenotypically normal patients, heterozygous abnormal patients and patients homozygous for the atypical gene is mentioned. Also presented is the relationship between plasma cholinesterase and the new relaxant mivacurium, and bambuterol, a prodrug to terbutaline. Additionally, the recent developments in the identification of the plasma cholinesterase genotypes are presented.

[Anesthesia and porphyria]

The porphyrias are a group of disorders of haem metabolism. A knowledge of which anaesthetic can precipitate an acute attack of porphyria is important, since an accumulation of metabolites can result in life threatening symptoms, such as abdominal pain, vomiting, photophobia, neuropathy, bulbar paresis and respiratory failure. Treatment consists primarily of adequate calorie intake e.g. glucose, but is otherwise symptomatic. Anaesthetic drug recommendations are based both on animal experiments and patient experience, primarily case histories. An array of local anaesthetics, hypnotics, sedatives, neuroleptics, analgesics, muscle relaxants, inhalation anaesthetics and some antibiotics are reviewed. Patients with a history of porphyria should be in an optimal condition and maintain a high calorie intake perioperatively. The pre-operative fast should be a minimum and iv-glucose is advisable while fasting. There are anaesthetic agents that are safe for both regional and general anaesthesia.