Pregabalin versus placebo in targeting pro-nociceptive mechanisms to prevent chronic pain after whiplash injury in at-risk individuals - a feasibility study for a randomised controlled trial

BACKGROUND

Whiplash-associated disorders (WAD) are an enormous and costly burden to Australian society. Up to 50% of people who experience a whiplash injury will never fully recover. Whiplash is resistant to treatment and no early management approach has yet been shown to prevent chronic pain. The early presence of central sensitization is associated with poor recovery. Pregabalin's effects on central sensitization indicate the potential to prevent or modulate these processes after whiplash injury and to improve health outcomes, but this has not been investigated. This paper describes the protocol for a feasibility study for a randomised controlled trial of pregabalin plus evidence-based advice compared to placebo plus evidence-based advice for individuals with acute whiplash injury who are at risk of poor recovery.

METHODS

This double blind, placebo-controlled randomised feasibility study will examine the feasibility and potential effectiveness of pregabalin and evidence-based advice (intervention) compared to placebo and evidence-based advice (control) for individuals with acute whiplash injury at risk of poor recovery. Thirty participants (15 per group) aged 18-65 years with Grade II WAD, within 48 hours of injury and currently experiencing at least moderate pain (NRS: ≥ 5/10) will be recruited from Emergency Departments of public hospitals in Queensland, Australia. Pregabalin will be commenced at 75 mg bd and titrated up to 300 mg bd as tolerated for 4 weeks followed by 1 week of weaning.

RESULTS

The feasibility of trial procedures will be tested, as well as the potential effect of the intervention on the outcomes. The primary outcome of neck pain intensity at 3 months from randomisation will be compared between the treatment groups using standard analysis of variance techniques.

DISCUSSION

Feasibility and potential effectiveness data will inform an appropriately powered full trial, which if successful, will provide an effective and cost-effective intervention for a costly and treatment resistant condition. It will also have implications for the early management of other traumatic conditions beyond whiplash.

TRIAL REGISTRATION

Clinical Trials Primary Registry: Australian and New Zealand Clinical Trials Registry.

CLINICAL TRIAL REGISTRATION NUMBER

ACTRN12617000059369 . Date of Registration: 11/01/2017. Primary Trial Sponsor: The University of Queensland, Brisbane QLD 4072 Australia.

Breakthrough pain characteristics and syndromes in patients with cancer pain. An international survey

Breakthrough pain (BKP) is a transitory flare of pain that occurs on a background of relatively well controlled baseline pain. Previous surveys have found that BKP is highly prevalent among patients with cancer pain and predicts more severe pain, pain-related distress and functional impairment, and relatively poor quality of life. An international group of investigators assembled by a task force of the International Association for the Study of Pain (IASP) evaluated the prevalence and characteristics of BKP as part of a prospective, cross-sectional survey of cancer pain. Fifty-eight clinicians in 24 countries evaluated a total of 1095 patients with cancer pain using patient-rated items from the Brief Pain Inventory (BPI) and observer-rated measures. The observer-rated information included demographic and tumor-related data, the occurrence of BKP, and responses on checklists of pain syndromes and pathophysiologies. The clinicians reported BKP in 64.8% of patients. Physicians from English-speaking countries were significantly more likely to report BKP than other physicians. BKP was associated with higher pain scores and functional interference on the BPI. Multivariate analysis showed an independent association of BKP with the presence of more than one pain, a vertebral pain syndrome, pain due to plexopathy, and English-speaking country. These data confirm the high prevalence of BKP, its association with more severe pain and functional impairment, and its relationship to specific cancer pain syndromes. Further studies are needed to characterize subtypes of BKP. The uneven distribution of BKP reporting across pain specialists from different countries suggests that more standardized methods for diagnosing BKP are needed.

Changes in median nerve somatosensory transmission and motor output following transient deafferentation of the radial nerve in humans

OBJECTIVE

To determine if transient anaesthetic deafferentation of the radial nerve would lead to alterations in processing of early somatosensory evoked potentials (SEPs) from the median nerve or alter cortico-motor output to the median nerve innervated abductor pollicis brevis (APB) muscle.

METHODS

Spinal, brainstem, and cortical SEPs to median nerve stimulation were recorded before, during and after ipsilateral radial nerve block with local anaesthesia. Motor evoked potentials (MEPs) and motor cortex output maps were recorded from the APB muscle.

RESULTS

There were no significant changes to most early SEP peaks. The N30 peak, however, showed a significant increase in amplitude, which remained elevated throughout the anaesthetic period, returning to baseline once the anaesthetic had completely worn off. MEP amplitude of the median nerve innervated APB muscle was significantly decreased during the radial nerve blockade. There was also a significant alteration in the APB optimal site location, and a small but significant decrease in the silent period during the radial nerve blockade.

CONCLUSIONS

Transient anaesthetic deafferentation of the radial nerve at the elbow leads to a rapid modulation of cortical processing of median nerve input and output. These changes suggest an overall decrease in motor cortex output to a median nerve innervated muscle not affected by the radial nerve block, occurring concomitantly with an increased amplitude of the median nerve generated N30 SEP peak, thought to represent processing in the supplementary motor area (SMA). Independent subcortical connections to the SMA are thought to contribute to the N30 response observed in this study. Unmasking of pre-existing but latent cortico-cortical and/or thalamo-cortical connections may be the mechanism underlying the cortical SEP increases observed following radial nerve deafferentation.

SIGNIFICANCE

Transient deafferentation of the radial nerve, which supplies wrist and hand extensor muscles, has been shown to alter sensory processing from and motor output to the median nerve innervated thenar muscles.

Adverse events regional feasibility study: indicative findings

AIMS

To identify substantive findings of potential clinical and managerial significance from a regional feasibility study of adverse events (AEs).

METHODS

A standardised protocol using structured implicit review was applied to 142 AEs generated in an audit study of three public hospitals in the Auckland region for admissions in 1995. Areas of potential significance addressed were: timing, location and impact of AEs; preventability; and clinical context and predictability.

RESULTS

142 cases were identified as AEs (10.7% of 1,326 screened records). In 102 cases, 7.7% of all screened records, it was considered to be more likely than not that health care management contributed to the AE. About half the reported AEs occurred before the index admission, the majority outside hospital. Over half of all events resulted in disability that was resolved within a month. An average 6.7 extra days stay in hospital were attributable to AEs. For 60% of AEs the evidence for preventability was either low or nonexistent. Areas of potential prevention were predominantly educational. Over half of all AEs occurred in a surgical context. Medical AEs were more likely to have occurred outside hospital, to be drug-related, to be associated with an acute admission, to be classified as highly preventable, and to have a greater impact on hospital stay.

CONCLUSIONS

Although the data generated by a feasibility study must be treated with caution, the pattern of results is consistent with comparable Australian findings and is of potential clinical and managerial significance.

Adverse events regional feasibility study: methodological results

AIMS

To assess the feasibility of research into the occurrence, causation and prevention of adverse events (AEs) in New Zealand public hospitals.

METHODS

A two-stage retrospective review was carried out on 1,575 medical records selected by systematic list sample from admissions for 1995 in three public hospitals in the Auckland region. Following initial screening, medical records were subject to structured implicit review using a standardised protocol. Feasibility measures, using international benchmarks where possible, were: adequacy of sample selection; completeness of medical records; reliability and validity of screener and reviewer judgements; internal consistency and face validity of AE determination and preventability assessment.

RESULTS

The sample selection procedure was effective, although nearly 10% of records could not be secured. Information in medical records was sufficient for the identification and analysis of AEs. Adequate levels of agreement were achieved for screener and reviewer judgements, with kappa scores ranging between 0.302 and 0.622 and positive predictive values between 50.0% and 89.7%. The criteria for AE determination showed internal consistency and face validity, as did those for preventability.

CONCLUSIONS

Research into the occurrence, causation and prevention of AEs in New Zealand health care settings is methodologically feasible and meets international benchmark standards.

Reduction of postoperative mortality and morbidity with epidural or spinal anaesthesia: results from overview of randomised trials

OBJECTIVES

To obtain reliable estimates of the effects of neuraxial blockade with epidural or spinal anaesthesia on postoperative morbidity and mortality.

DESIGN

Systematic review of all trials with randomisation to intraoperative neuraxial blockade or not.

STUDIES

141 trials including 9559 patients for which data were available before 1 January 1997. Trials were eligible irrespective of their primary aims, concomitant use of general anaesthesia, publication status, or language. Trials were identified by extensive search methods, and substantial amounts of data were obtained or confirmed by correspondence with trialists.

MAIN OUTCOME MEASURES

All cause mortality, deep vein thrombosis, pulmonary embolism, myocardial infarction, transfusion requirements, pneumonia, other infections, respiratory depression, and renal failure.

RESULTS

Overall mortality was reduced by about a third in patients allocated to neuraxial blockade (103 deaths/4871 patients versus 144/4688 patients, odds ratio=0.70, 95% confidence interval 0.54 to 0.90, P=0. 006). Neuraxial blockade reduced the odds of deep vein thrombosis by 44%, pulmonary embolism by 55%, transfusion requirements by 50%, pneumonia by 39%, and respiratory depression by 59% (all P<0.001). There were also reductions in myocardial infarction and renal failure. Although there was limited power to assess subgroup effects, the proportional reductions in mortality did not clearly differ by surgical group, type of blockade (epidural or spinal), or in those trials in which neuraxial blockade was combined with general anaesthesia compared with trials in which neuraxial blockade was used alone.

CONCLUSIONS

Neuraxial blockade reduces postoperative mortality and other serious complications. The size of some of these benefits remains uncertain, and further research is required to determine whether these effects are due solely to benefits of neuraxial blockade or partly to avoidance of general anaesthesia. Nevertheless, these findings support more widespread use of neuraxial blockade.

[Pharmacokinetics of combined antibiotic therapy in the newborn infant]

In 66 newborn infants (AGA) suffering from septicemia concentration time courses of gentamicin, ampicillin and cefotaxim were determined to perform and an individual drug monitoring. Gentamicin was analysed from capillar blood samples using EMIT, Ampicillin and Cefotaxim by HPLC-technique. Volumes of distribution, apparent elimination half lives, maximum -, minimum and steady state concentrations were calculated using digital iteration programs. Based on a fixed dose regimen the kinetic parameters of gentamicin were extremely variable. To achieve a median steady state concentration of 3 micrograms/ml gentamicin in serum corrections from -17% to +110% of the foregoing dose were necessary. With 100 mg/kg ampicillin or cefotaxim per day sufficient concentrations in serum were reached. But in some patients a dosage of 5-7 mg/kg/d of gentamicin is too low, while others show concentrations near to the toxic levels. By a combination of gentamicin plus ampicillin pharmacokinetic parameters are not influenced; while if gentamicin is combined with cefotaxim the apparent elimination halflife of gentamicin (beta-slope) is significantly reduced. Therefore an individual drug monitoring of drugs with a small therapeutic range, for example gentamicin, is necessary to optimize therapeutic results.