Predictors of pleural complications in trauma patients undergoing tube thoracostomy: A prospective observational study

ABSTRACT Objective: to identify variables related to pleural complications in patients undergoing tube thoracostomies due to traumatic injuries. Method: we conducted a prospective observational study from May/2019 to January/2021 including adult trauma patients submitted to tube thoracostomies after hospital admission. Patients undergoing thoracotomies as the initial treatment were not included. We excluded patients with suspected and confirmed COVID-19 diagnosis during the hospitalization. Pleural complications were defined as clotted hemothorax, residual pneumothorax and empyema. Students t, Mann Whitneys, Chi square and Fishers exact test were used to compare variables between groups. We considered p<0.05 as significant. Results: we analyzed 68 patients. The mean age was 36.0 + 12.6 years and 91.2% were male. The mean RTS and ISS were, respectively, 7.0 ± 1.6 and 15.9 ± 7.6. The most frequent trauma mechanism was stab wounds in 50.0%, followed by blunt trauma in 38.2%. The severity of thoracic injuries was stratified (AIS) as 2 (4.4%), 3 (80.9%), 4 (13.2%), e 5 (1.5%). Pleural complications happened in 14 (20.5%) patients, being clotted / residual hemothorax (11.8%), residual pneumothorax (4.4%), empyema (2.9%) and miscellaneous (1.4%). These patients were treated by thoracoscopy (5), thoracotomy (3), chest re-drainage (3) and clinical measures alone (3). There was a significant association between pleural complications with the time of permanence (p<0,001) and the necessity of relocation (p<0,001) of the drain. Conclusion: the predictors of pleural complications in this series were time of permanence and the necessity of relocation of the drain.

many resources are not available to all patients in our country.The identification of variables related to pleural complications allows us to select patients at higher risk early, directing efforts to reduce adverse effects.
The aim of this study is to identify variables related to pleural complications in trauma victims undergoing chest drainage.

METHODS
This study was approved by the Ethics in Research Committee of our institution (Opinion Number: 3.304.287/ CAAE: 11867919.1.0000.5479).
We performed a prospective, observational study between May 2019 and January 2021.We included all adult (age >17 years) victims of trauma (blunt or penetrating) admitted to the emergency room directly from the scene and undergoing chest drainage in the first six hours for the treatment of hemothorax / pneumothorax resulting from the event.We did not include those who did not sign the informed consent form, patients drained in the prehospital setting, those with initial treatment by thoracotomy or sternotomy, those who had chest drainage because of iatrogenic injuries (eg.central catheter insertion), cases initially treated non-operatively, and those with coagulopathy and use of anticoagulants.We excluded those who intentionally removed the chest drain due to lack of cooperation with the treatment and those who were diagnosed with COVID-19 during hospitalization.
In our institution, water-seal chest drainage is indicated for the treatment of traumatic hemothorax and pneumothorax, diagnosed clinically or by imaging tests.There are exceptions in trauma victims with occult pneumothoraces (not identified on radiography, but only on chest tomography), small-volume pneumothorax in asymptomatic patients, and small-volume hemothorax (<2.5cm in length, accumulated in the posterior region at computed tomography).The surgical procedure is performed under local anesthesia according to the technique standardized by the Advanced Trauma Life Support (ATLS) 10 th edition 14 , followed by an anteroposterior chest X-ray to assess drain location.If the drain is not properly functioning (eg, without oscillation of the column in the water seal), with holes in the subcutaneous tissue, or in an atypical location, the drain is promptly relocated.The chest tube is removed after lung expansion (clinical and radiological) and a output of less than 150ml/24h.After removal, the patient undergoes a new chest X-ray in 12 hours.
We collected data on sex, age, trauma mechanism (blunt/penetrating, gunshot wound, stab wound, or other), clinical variables at emergency room admission (vital signs, Glasgow Coma Scale) 15 , Revised Trauma Score (RTS) 16 , identified traumatic injuries and their stratification by the Abbreviated Injury Scale (AIS) 17 and the Injury Severity Score (ISS) 18 , chest drainage site (emergency room or operating room), surgical procedure variables (asepsis and dressing, use of systemic sedation, need for orotracheal intubation), procedure technique (intercostal space of insertion, gauge and positioning of the drain), surgeon experience (resident or staff), chest X-ray performed before the procedure, need for chest redrainage, pre-existing pulmonary comorbidities, technical complications (visceral injuries, subcutaneous orifices, fixation failure), general complications, and deaths.
Pleural complications were defined as: At our institution, small-volume residual pneumothoraces are treated by optimizing analgesia and physical therapy, while medium-and large-volume pneumothoraces are submitted to chest redrainage.Retained or clotted hemothoraces of significant volume are treated by early thoracoscopy (ideally until the 4th or 5 th day), with a small thoracotomy if necessary for postoperative antibiotics.The most frequent anatomical site of drain insertion was the fifth intercostal space (58.8%), followed by the sixth intercostal space (13.2%), fourth intercostal space (7.4%), and others (20.6%).

Predictors of pleural complications in trauma patients undergoing tube thoracostomy: A prospective observational study
Pre-drainage chest radiography was performed in 51 (76.1%) cases.
lavage.Complicated effusions and empyemas receive antibiotics and open chest drainage after the 10 th day and pleurostomy afterwards, depending on the evolution.
We divided patients into two groups: • Group A: with pleural complications (sum of all types described) • Group B: other patients All cases were followed up by the authors during hospitalization.We also obtained data from the electronic medical records (MV ® ) and incorporated them into a Microsoft Excel spreadsheet for Windows, version 2010.At the end of the collection, the data were analyzed by the Biostatistics Service of Santa Casa of Sao Paulo School of Medical Sciences (FCMSCSP).We present data as mean ± standard deviation.In addition to descriptive statistics, we compared the variables of groups A and B to identify predictors of pleural complications.We used the chi-square or Fisher's exact test to analyze categorical variables.We assessed continuous variables with the Student's t or Mann Whitney tests, according to the normality of the sample.Values of p<0.05 were considered significant.

RESULTS
The final sample consisted of 68 cases, with a mean age of 36.0 ± 12.6 years, RTS at admission of 7.0 ± 1.6, and of ISS of 15.9 ± 7.6, 62 patients (91.2%) being male (Table 1

DISCUSSION
The sample of this study is similar to those described in other series, with a predominance of young male adults, victims of penetrating injuries, and chest drainage performed in the trauma room 4,5,8,9,19 .Chest injuries classified as AIS=3 occurred in 80.9%.Most patients were hemodynamically stable at admission.In 76.1% of cases, chest radiography was performed before chest drainage.
The fact that 73.1% of the procedures were performed by first-year residents (R1 of General Surgery) may reinforce the mistaken idea that chest drainage is a procedure with few complications.The rate of pleural complications in our sample (20.5%) was significant and comparable to other series 8,9,19 .We did not observe serious iatrogenic injuries, such as intercostal vascularnervous bundle lesion, lung parenchyma laceration, and diaphragmatic or intra-abdominal injury.However, in about 20% of the cases, the drain was inserted far from the location deemed correct by the ATLS 10 th Edition proposed technique 14 .
None of these complications were directly related to any death.
Chest redrainage was required in 62.5% of the patients who developed pleural complications and in 7.8% of the others (p<0.001).The mean duration of the pleural drain was 12.1 ± 11.1 days in those with pleural complications and 4.7 ± 2.4 in the others (p<0.001)(Tables 2 and 3)..There are studies that report a greater chance of late and after discharge rebleeding in approximately 1.4% of patients with chest injuries 24,25 .
The influence of chest drain caliber on the frequency of complications was also studied by other authors, who did not find differences between larger and smaller diameters 26,27 .In our study, we did not find a relationship between pleural complications and the size of the drains used.The new edition of the ATLS (10 th edition) already suggests smaller caliber drains for chest drainage 14 .
The only variables statistically associated with a higher frequency of pleural complications were the need for chest drainage (due to non-functioning drains) and the length of permanence of the drain.
These variables could also be explained as the treatment of pleural complications and not just as their cause.
However, it makes sense to say that chest redrainages due to malfunction increase the frequency of infection, as reported in the literature 22 .
et al. draw attention to the importance of the operative technique in preventing post-drainage complications28 .These authors emphasize the importance of asepsis, of avoiding the use of trocars, of performing a digital examination before introducing the drain into the pleural cavity, and of directing the drain in a posterior and cranial position.Studies analyzed the use of ultrasound of the chest as part of the post-drainage care protocol with the aim of reducing the length of permanence of the drain29,30 .Fonseca et al., in 2020, demonstrated a reduction in the length of stay of the chest drain from 4.9 to 2.5 days when ultrasound was used for decision making.Perhaps this could be an alternative, as pleural complications were associated precisely with longer permanence of the chest tube.There are some limitations that we need to highlight in our study.The number of patients did not allow us to perform a more in-depth statistical analysis, such as logistic regression, to identify independent factors.It was a study developed in the middle of a pandemic and many patients diagnosed with COVID-19 were not included in the final sample.There were strict selection criteria to control for the many variables involved.Thus, we did not include patients treated directly by thoracotomy or sternotomy, as well as those who had initial nonoperative treatment and requiring late drainage.Our results reinforce that the reduction of pleural complications also depends on measures taken during drainage.Staff must be trained to properly locate and secure the drain.The operative technique must be perfect.If the drain is not working, it must be repositioned right away.By avoiding late draining due to non-functioning drains, we reduced the length of stay, the chance of infection, and, consequently, pleural complications.

Table 1 -
General sample data.
NascimentoPredictors of pleural complications in trauma patients undergoing tube thoracostomy: A prospective observational study

Table 2 -
Comparison of qualitative variables between groups.
Group A: patients with pleural complications; Group B: patients without pleural complications; *p-value derived from chi-square or Fisher tests; R1: first year general surgery resident; OTI: Orotracheal intubation.

Table 3 -
Comparison of quantitative variables between groups.
Group A: patients with pleural complications; Group B: patients without pleural complications; *p value derived from Student's t or Mann Whitney tests; RF: respiratory frequency; SBP: Systolic Blood Pressure; GCS: Glasgow Coma Scale; RTS: Revised Trauma Score; ISS: Injury Severity Score.