Can we manage a traumatic hemothorax without a chest tube?

Hemothorax: how big is the problem?

Hemothorax is one of the most frequent situations encountered in patients with thoracic trauma.

It is estimated that approximately 300,000 cases of traumatic hemothorax (HTX) occur annually in the United States, with blunt trauma accounting for about 70% of these cases. Untreated HTX is associated with significant pulmonary morbidity, including retained hemothorax, empyema, respiratory failure, and the need for surgical intervention.

Current guidelines recommend tube thoracostomy (TT) for the management of HTX. However, TT has a high complication rate, reaching up to 21%. TT may increase the risk of pulmonary complications in certain cases more than untreated HTX.

Therefore, surgeons seek to better understand which patients require chest drainage for the treatment of traumatic hemothorax, to reduce the risk of complications and increase the safety of care.

The 300ml Rule

Some studies suggest that, in selected patients, the volume of traumatic hemothorax can help make this decision. This is because there is some evidence showing that there is no increased morbidity in patients with a traumatic hemothorax volume of less than 300ml when managed without chest drainage.

But how can the volume of hemothorax be known before draining it? There are several ways to quantify fluid volume in the pleural cavity. One of them is using Mergo’s formula. To apply it, you need to calculate the "depth" (the greatest anteroposterior length on the axial cut of the chest CT) and the "extent" of the effusion (the greatest craniocaudal length on the coronal cut or 3D reconstruction).

According to Mergo, V = d² x L (V: volume; d: depth; L: extent).

The Study

A recent study with Marc deMoya as the senior author evaluated the outcomes of managing patients with traumatic hemothorax following the institution of a guideline suggesting the conservative treatment of stable patients with traumatic hemothorax, i.e., without chest drainage.

This study is a single-center retrospective review involving hemodynamically stable adult patients admitted with HTX confirmed by CT before (2015-2016) and after (2018-2019) the implementation of the 300 mL guideline. Patients admitted during 2017 were excluded to allow for an implementation window of the guideline. Additional exclusion criteria included age <18 years, TT placement before CT, absence of CT, death within 5 days of admission, and concomitant pneumothorax >20mm.

HTX volume was calculated using Mergo's formula. Collected data included demographics, injury severity scores on admission, vital signs, imaging findings on admission (including concomitant pneumothorax, pneumothorax size, HTX volume, number of ipsilateral rib fractures, concomitant pulmonary contusion, diaphragmatic injury), comorbidities, hospital complications, and discharge status. The primary outcome was observation failure, defined as the need for CD, video-assisted thoracoscopic surgery (VATS), and thoracotomy after an initial observation period (>4 hours after CT) due to worsening imaging or symptoms.

Study Results

A total of 357 patients met the inclusion criteria, of whom 210 were admitted after the guideline implementation. The median age of patients was 51 years, with 74% male. The majority of injuries were caused by blunt trauma (88%). There were no significant differences in demographic characteristics or comorbidities between the groups. After the guideline implementation, the observation rate significantly increased from 59% to 75% (p<0.001), and TT placement decreased from 57% to 42% (p<0.001).

The length of hospital stay decreased from a median of 8 days to 6 days (p=0.02), and the ICU stay reduced from 3 days to 2 days (p=0.04). There were no significant differences in observation failure rates (23% vs 28%), pulmonary complications (24% vs 14%), 30-day readmission (7% vs 8%), or 30-day mortality (5% vs 2%). The most common reason for observation failure was HTX progression on CXR (67%), followed by worsening pneumothorax on CXR (16%).

Of the 68 patients who failed observation, 45 (67%) required drainage due to HTX progression, and 11 (16%) due to worsening pneumothorax, as identified on CXR. Other reasons included the need for rib fixation (7%) and unknown causes (9%). Multivariate analysis indicated that concomitant pneumothorax, flail chest, prolonged mechanical ventilation, and HTX volume >300 mL were independent predictors of observation failure.

Study Discussion

Implementing the 300 mL guideline significantly decreased CT placement without increasing observation failure or complication rates. This study supports the safe and effective observation of small traumatic HTX in hemodynamically stable patients, facilitating clinical decision-making in HTX management. Reducing hospital and ICU stays suggests more efficient resource utilization and preventing unnecessary procedures.

However, the authors caution about the study's limitations. The study's retrospective nature increases the risk of selection bias and confounding. The reason for observation failure and subsequent need for CT could not be determined in some patients due to a lack of documentation. The small sample size may have prevented the detection of differences in certain outcomes, such as pulmonary complications. Additional prospective studies are needed to validate a safe cutoff point for traumatic HTX observation and to assess the cost-effectiveness of using CT in thoracic trauma compared to immediate CT placement, especially in low- and middle-income countries.

Conclusion

Defining a 300ml cutoff point for the conservative treatment of stable patients with traumatic hemothorax appears promising. The absence of prospective studies applying the 300ml rule limits the widespread adoption of this concept. Nonetheless, we must acknowledge the contribution of this group in adding a valuable study on traumatic hemothorax and paving the way for further research on this topic.

References

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