Back in 2016 we published a blog on chest drains and chest aspiration, in which we argued that the dogma of putting in huge drains for traumatic haemothoraces should be questioned.
The dogma of using large drains has puzzled me for many reasons. One reason is that I also work in paediatric major trauma and there no way that I’m going to place a 36F drain in a 6 year old. Apart from anything else I’d probably have to remove a rib to do it, and yet the blood and air still comes out. Big drains might appear to be an obviously good choice for big volumes and maybe we think they clot less, but observational studies in trauma patients have suggested that smaller drains (28-32F vs 36-40F) may be just as effective. How small you can go is uncertain but 36-40F are pretty huge and I’ve stopped using them in my patients. Smaller than this and there is little evidence, but having worked in paeds and adults I’m pretty confident blood does come out of smaller tubes. Back in 2016 we found one study by Russo in swine that suggested 14F tubes may be OK, but it was a small animal study and we expressed caution in extrapolating that to clinical practice.
This month we have new evidence from the US specifically looking at the 14F question in humans. The abstract is below, but as always we want you to read the full paper and make up your own mind.
What kind of study is this?
This is a randomised controlled trial which is the appropriate method for investigation of a therapeutic intervention. The trial was conducted in a number of US centres. Patients were randomised in blocks of 4 using a
Who was studied?
This study recruited patients aged over 18 who required chest drainage for a traumatic haemothorax or haemo-pneumothorax. Those with small amounts of blood in the chest were excluded. The decision to place a chest drain was left to the discretion of the treating clinicians based on clinical and radiological features.
Importantly those who required a drain in extremis were not included, and so those that we place in the resus room directly following the primary survey are probably excluded.
222 patients were assessed for eligibility, 120 were included and 119 made it through to final analysis.
What did they do?
Patients were randomised to either a chest drain sized 28-32F or to a 14F pigtail catheter. Both were placed under sterile conditions. Pigtails were placed using a seldinger technique. In the UK we use a lot of seldinger drains, but they are not pigtails, rather they are straight (not curved), this is unlikely to substantially change the impact, but is worth noting.
They kept all drains on -20mmHg suction.
All other aspects of the management of patients was left to the discretion of the treating clinicians in order to reflect real world practice.
What about the outcomes?
The primary outcome was failure of the procedure as defined as a failure rate for the drainage catheter. Failure rate was defined as an radiographically apparent hemothorax after drainage or a requirement for additional intervention including either a second catheter insertion, a thrombolysis, or a video-assisted thoracoscopy surgery.
Secondary outcomes looked at pain, output, patient journey etc.
Tell me the main results
The patient groups were reasonably well balanced at baseline. In terms of the main outcome the failure rate was 11% for pigtail catheters and 13% for chest drains (p=0.74). There were 2 significant complications, 1 in each group. Unsurprisingly, patients receiving a chest drain had more pain/discomfort on insertion (though using an unvalidated assessment tool).
Based on the authors sample size the results demonstrated non-inferiority (though more on this later)
The authors have stated that the 2.8% difference found is non-inferior, but my rough estimate of the confidence intervals around this suggest that the 95% confidence intervals would be about 10% worse to 17% better, and that’s quite a difference (I know that this was not the analysis they did around non-inferiority and is a superiority based approach, but I’m using it as an illustration here).
How confident can we be that the treatments are really equivalent?
120 is quite a small number of patients as it is based on a power study for non-inferiority that sought to identify a 15% difference based on an event rate of 30% failure. The initial sample size calculation required 95 patients in each arm, but they stopped early following an interim analysis. They state the interim analysis was due to the prolonged period of recruitment, which is not an ideal reason. I am slightly concerned by the sample size as it is based around a non-inferiority margin of 15% which is too wide in my opinion to be clinically relevant. I would not accept a 14.9% margin as non-inferior on the specified estimated event rate of 30%. Keeping the non-inferiority margin large keeps the numbers of patients required low, but if overly large will not influence clinical decision making
It’s also worth noting that the failure rate in the trial was much lower than the predicted 31-33% level that they based their sample calculation on. This brings me to the conclusion that from my perspective the trial is underpowered to assure me that the two treatments are clinically equivalent. As described above, if this were analysed as a superiority trial the confidence intervals would be very wide.
So should we change practice and use smaller drains?
The authors should be congratulated on performing this trial, it certainly adds to the available clinical evidence and it is in keeping with other studies in this area. As a stand alone trial the precision of the main outcome are a little too broad to mandate a change in practice, but there is an increasing body of work that consistently shows that the dogma of very large chest drains in trauma should be challenged.
We should also note that this trial used 14F pigtail catheters which I don’t think are in common use in UK emergency departments (though of course they could be).
The authors describe how difficult it was to complete the study, in part because of established beliefs amongst clinicians regarding the need for large drain sizes. It is likely that this will be the case in other health economies, and it is certainly a factor in Virchester.
From a personal perspective I’ve been using smaller and smaller drains throughout my career with my current go-to drain for trauma patients being a 28F. This study, in conjunction with other data may encourage me to go smaller still.
The increasing use of seldinger drains means that our trainees have less opportunity to develop skills in the insertion of open drains that are still required in the emergency part of our practice. Experience is further curtailed by the increasing use of conservative management of both traumatic and non-traumatic pneumo and pneumo-haemothorax. As clinical practice changes we must be mindful to ensure that we teach and retain the ability to perform an open chest drain with speed and skill.
References and further reading
Narong Kulvatunyou et al The small (14 Fr) percutaneous catheter (P-CAT) versus large (28–32 Fr) open chest tube for traumatic hemothorax: A multicenter randomized clinical trial. J Trauma Acute Care Surg 2021 Nov 1;91(5):809-813
Kulvatunyou N, Joseph B, Friese R, et al. 14 French pigtail catheters placed by surgeons to drain blood on trauma patients: is 14-Fr too small? J Trauma Acute Care Surg. 2012;73(6):1423-1427. [PubMed]
Inaba K, Lustenberger T, Recinos G, et al. Does size matter? A prospective analysis of 28-32 versus 36-40 French chest tube size in trauma. J Trauma Acute Care Surg. 2012;72(2):422-427. [PubMed]
Yi J, Liu H, Zhang M, et al. Management of traumatic hemothorax by closed thoracic drainage using a central venous catheter. J Zhejiang Univ Sci B. 2012;13(1):43-48. [PubMed]
Rivera L, O’Reilly E, Sise M, et al. Small catheter tube thoracostomy: effective in managing chest trauma in stable patients. J Trauma. 2009;66(2):393-399. [PubMed]
Russo R, Zakaluzny S, Neff L, et al. A pilot study of chest tube versus pigtail catheter drainage of acute hemothorax in swine. J Trauma Acute Care Surg. 2015;79(6):1038-43; discussion 1043. [PubMed]
Percutaneous Chest Tubes: The Humane Choice . The Short White Coat in EM. Lauren Westafer. https://shortcoatsinem.blogspot.co.uk/2016/01/percutaneous-chest-tubes-humane-choice.html. Published 2016. Accessed November 18, 2016.
Iain Beardsell, “Critical Appraisal Nuggets – The St.Emlyn’s CAN Podcast,” in St.Emlyn’s, August 10, 2016, https://www.stemlynsblog.org/critical-appraisal-nuggets-the-st-emlyns-can-podcast/.