How useful are paravertebral catheters for patients with rib fractures?

“Safety, complications and clinical outcome after ultrasound-guided paravertebral catheter insertion for rib fracture analgesia: a single-centre retrospective observational study” Womack et al. Anaesthesia 2019.

“There’s a way to do it better – find it.” Thomas Edison

Background

Rib fractures are associated with significant mortality and morbidity, especially in more venerable groups of patients. Regional analgesic techniques have become a popular option for rib fracture management, including thoracic epidurals and paravertebral catheters (PVCs)

Thoracic PVCs provide chest wall analgesia via a unilateral block, which can cover the size of five dermatomes with spread. The following protocol was employed by the study hospital to provide a PVC service for rib fracture analgesia.

Hospital protocol for rib fracture management and thoracic PVC use:

  • Initial pain management in ED: IV paracetamol  and morphine
  • Rib fractures reviewed by pain team within 24 hours. Analgesia optimised and PVC offered if severe pain, pain limiting expectoration or for those with risk factors for poor outcomes
    • Risk factors: elderly, frailty, pre-existing respiratory disease, multiple rib fractures, rib fracture in more than one anatomical position 
  • Thoracic PVCs inserted with US guidance, in-plane transverse oblique approach
    • 20-40ml of 0.25% levobupivacaine used., then infusion commenced at approximately 8ml/hour
  • Patients reviewed daily by pain team, typical infusion for 5 days
  • 2nd PVCs considered if inadequate analgesia, patients with bilateral fractures or more than 6 unilaterally 

Aim

  • Retrospectively review the outcome of patients with rib fractures following the initiation of a PVC service  
  • Primary outcome measure was in-hospital mortality

Methods

  • Single centre retrospective observational cohort study – Royal Victoria Infirmary, Newcastle (trauma centre)
  • Data analysed for a 4 year period
  • 2 separate databases used to collect and analyse data
    • Hospital’s own pain service database – PVC insertion details, complications and reasons for removal
    • TARN (Trauma Audit and Research Network) database – Patient baseline characteristics, demographics, injury profile and clinical outcome
  • Pain service database used to identify patients treated with PVC insertion, which was then cross-referenced with the data for rib fracture patients from the TARN database
  • Patients with PVCs inserted for analgesia were compared with those with no regional analgesia. Other regional techniques were excluded. Hospital mortality was the primary outcome
  • Propensity matching was used to try to resolve the differences between baseline characteristics of PVC and no PVC groups when analysing data
  • Multivariate analysis was used to create hazard ratios for hospital mortality in all patients with rib fractures

Results

  • There were 314 PVCs inserted in 291 patients with rib fractures over the 4 year period. Overall 829 patients admitted with rib fractures found on the TARN database
  • One insertion complication over the study period
  • Reason for PVC removal documented in 261 cases; 215 planned removal (82%, 95% CI 77-87%), 39 catheter dislodgement/disconnection (15%, 11-20%), 5 ineffective analgesia (2%, 1-4%), 2 due to adverse effects (1%, 0-3%)
  • Proportion of patients with rib fractures receiving PVCs for analgesia increased over the study period from 15.5% to 48.2%
  • Patients with PVCs inserted were more likely to be older, have more rib fractures and have a flail segment. These patients were also more likely to have lower injury severity scores, higher presenting GCS, less likely intubated on the scene/ED and generally had a lower predicted mortality
  • Propensity matching used to try to resolve these differences between baseline characteristics between PVC and no PVC groups
  • Observed:predicted mortality ratio improved year on year from 1.04 to 0.66 for all rib fracture patients.
  • Lower in-hospital mortality rates were found for patients with PVCs inserted compared to no regional technique, 3% to 16.6% respectively (p<0.001), but similar critical care usage and LOS. In propensity matched patients this difference reduced with mortality rates of 3% and 8% respectively (p=0.013)
  • Hazard ratios for hospital mortality in all patients with rib fractures showed that PVC insertion was protective, HR (95%CI) 0.34 (0.15-0.76) p=0.004
  • When PVC insertion was treated as a time-dependent covariate the treatment benefit of PVC insertion on hospital mortality was no longer significant, HR 0.62 (0.28-1.40) p=0.249

Discussion

Strengths

  • Very few adverse effects or complications with PVC insertion recorded over the study period
  • Inadequate analgesia was the reason for PVC removal in only 2% of cases
  • Use of PVCs for rib fracture analgesia increased over the study period for all patterns of rib fractures
  • The above demonstrates that a PVC service for rib fracture analgesia can be a feasible and sustainable, with few complications documented over the study period
  • Improvement in observed:predicted mortality ratio for all patients with rib fractures over the study period. This could be an indicator of enhancement in trauma patient care

Weaknesses

  • Retrospective single centre study
  • No outcome measure relating to pain control used for analysis of analgesic efficacy  e.g. opiate use or pain scores
  • 2 separate databases used for analysis with discrepancies between them. Only 233 of the 291 patients with PVCs inserted found on the TARN database limiting data collection
  • Propensity matching is better used in samples with larger number of control subjects
  • Immortal time bias likely to be responsible for much of the benefit in observed to predicted mortality in PVC group – e.g. to have a PVC inserted patients must have survived to this point, selecting out some of the more unwell patients
  • Hazard ratio showing PVC use as protective for in-hospital mortality was no longer significant once PVC insertion was treated as a time-dependent co-variate

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