Optimizing postoperative care protocols in thoracic surgery: best evidence and new technology

Introduction

Postoperative clinical pathways reduce length of hospital stay and increase patient satisfaction without increasing adverse events (1-7). Colorectal surgeons lead the way by implementing clinical pathways focusing on early resumption of oral diet and ambulation, which was countercurrent to previously established practice. Similar success with postoperative clinical pathways has been achieved in head and neck surgery with decreased pulmonary complications and shorter length of stay (2). A survey of Canadian cardiac surgery intensive care units found 26 of 28 institutions used clinical pathways (8). There have also been efforts to standardized and streamline the care of patients who undergo lung resection (3-7). More recently, interest in optimizing the care of lung resection patients has been rekindled by the introduction of digital pleural drainage technology into clinical practice.

Clinical pathways

Postoperative clinical pathways have been the backbone of fast-track programs in thoracic surgery. Investigators from Europe reported on the implementation of a fast-track pulmonary resection which included early feeding and ambulation, multimodal analgesia and early removal of chest tubes (3). Although they did not find a significant difference in length of stay, they reported a higher level of patient satisfaction. In Asia, investigators have succeeded in decreasing post-operative delirium, decreasing hospital stay, and lowering health care costs through preoperative identification of high risk patients and successful implementation of pulmonary resection care pathways (4,5,9). Improvements have also been achieved in North American centers using a similar approach (6).

Our institutional pathways and protocols are primarily aimed at standardization of postoperative feeding, blood work, pain management, respiratory care, and allied health team involvement, such as, physiotherapy, respiratory therapy and social work to decrease length of stay. These general aspects of post-surgical care probably enhance patient experience. However, by including more specific aspects of care following lung resection (e.g., chest tube management), the clinical pathways could potentially have a greater impact on recovery and length of hospitalization.

Review of published literature indicates that recommendations for the management of chest tubes are inconsistent (10-12). Clinical decisions are often based on institutional practices, physician training, and preferences developed from experience (13). The ideal chest tube management algorithm has yet to be determined. The timing and parameters under which chest tubes can safely be removed, the best method of removal, and the need for routine chest X-rays are still the subject of debate. Optimizing the duration of chest tube drainage after lung resection is a critical component of improved quality of care as both premature and delayed chest tube removal may lead to increased hospital stay and costs (14-16).

With the implementation for any protocol, outcomes must be continuously measured to allow for an iterative design process leading to optimal protocols meeting the needs of the patients in a particular institutional setting. Successful implementation of care pathways should include mechanisms to monitor compliance. Deviations from the expected chest tube drainage period should be reviewed to understand its feasibility and safety profile, and to allow for data-driven optimization. We have demonstrated the effectiveness of this strategy in the management of postoperative adverse events, which are prospectively recorded and reviewed on a monthly basis at our institution (17,18).

In the following sections, we will discuss four main aspects of developing a chest tube management protocol: (I) appraising the role of chest X-rays in the management of lung resection patients with chest drains; (II) selecting of a fluid output threshold below which chest tubes can be removed safely; (III) deciding whether suction should be applied to chest tubes; (IV) and developing a safe approach to chest tube removal.

Role of postoperative chest X-rays in chest tube management

The use of daily chest X-rays is often part of routine clinical practice in the postoperative management of lung resection patients. In a recent meta-analysis, including 3,649 patients, the use of routine chest X-rays was compared to selective chest X-rays in showing a mean reduction of 3.15 chest X-rays per patient (P<0.01) without any significant increase in mortality, intensive care unit stay or hospital length of stay (19). As part of a prospective randomized trial comparing analog and digital pleural drainage devices completed at our center, 176 patients were monitored prospectively after anatomic lung resection for lung cancer (20). Data on the use of chest X-rays was documented as an ancillary outcome. All chest X-rays were recorded and classified as normal, radiologically abnormal, or clinically abnormal. A chest X-rays was deemed radiologically abnormal when at least one of the following minor abnormalities was present: small pneumothorax (<30%), minimal subcutaneous emphysema that is not palpable and can only be seen on chest X-ray, or a small pleural effusion causing minimal blunting of the costophrenic angle. If the latter findings were more severe or if there was any other significant finding (e.g., lobar atelectasis) then the chest X-ray was labeled clinically abnormal, regardless of the patient’s clinical status. The total number of postoperative chest X-rays performed was 1,550 or 1.5 per patient-day of hospitalization. Of the 176 first postoperative radiographs performed in the recovery room, the vast majority were either normal (79/176; 45%) or radiologically abnormal (87/176; 49%). Of the ten patients (6.0%) who had a clinically abnormal first postoperative chest X-ray, 6 (3.4%) had more than minimal subcutaneous emphysema and 4 (2.6%) had a pneumothorax larger than 30%. All of these patients were observed with the exception of one patient (1/176; 0.5%) for whom chest tube suction was increased in response to the X-ray findings. None of the patients with a clinically abnormal first postoperative chest X-ray developed complications that could have been prevented using the radiologic data. Of the additional 1,374 postoperative chest radiographs performed outside the recovery room, an additional 25% (348/1,374) were normal and 52% (710/1,374) were reported as radiologically abnormal. In other words, more than 77% of routine postoperative chest X-rays showed findings that would be unlikely to influence clinical decisions regarding chest tube management following lung resection. Chest X-rays may be associated with pain or discomfort as a result of patient positioning for image acquisition or, in some cases, during transfer to the radiology department for studies not performed at the bedside. At our institution, this proportion of normal or near-normal X-rays represents an additional unnecessary time and expense. Although we cannot make definitive recommendations based on these results, our institutional data questions the clinical usefulness and cost-effectiveness of routine chest X-rays in the management of patients who are recovering from pulmonary resection. This aspect of patient care should be scrutinized in future efforts to optimize health care efficiency while maintaining high standards of patient safety.

Fluid output threshold for safe chest tube removal

Another common point of contention in the management of chest tubes is the fluid output threshold below which removal is considered appropriate. A safe threshold should minimize the probability of chest tube reinsertion for symptomatic fluid re-accumulation after chest tube removal. Table 1 summarizes the recent literature on safe drainage thresholds to remove chest drains after pulmonary resection. Most recommendations found in the literature advocate the use of a fixed threshold that is independent of the size of the patient. The majority of the trials do not report sample size calculations or rigorously follow the Consolidated Standards of Reporting Trials (CONSORT) 2010 guidelines (27). Almost 15 years ago, randomized controlled trial data demonstrated safety in removing chest tubes draining less than 200 mL in 24 hours (21). The latter threshold was the highest evaluated at that time. Subsequently, non-randomized studies suggested that a much higher fluid output limit, from 400-500 mL per 24 hours, could be considered safe for chest tube removal (22,23,25). More recently, a randomized comparison of 100 vs. 300 mL per 24 hours found that a higher threshold was associated with a shorter hospital stay without any increase in adverse events (24). Another recent randomized trial reported that a fluid output of 300 mL per day was optimal (26). Eight of 51 patients (15.7%) of patients with a chest drain removal threshold of 450 mL required thoracentesis compared to 1 of 99 patients (1%) with a threshold of less than 300 mL per day. In reviewing the published literature on this topic, it is apparent that the 24-hour drainage threshold that is considered safe for chest tube removal has increased consistently over the past 15 years.

Table 1 Literature on safe drainage thresholds for removal of a chest tube
Full table

In attempting to drive consensus amongst surgeons, we developed an approach based on pleural fluid physiology which takes into account patient size and lymphatic flow, similar to what other investigators have previously put forth (28). From a pleural physiology standpoint, using the same pleural fluid output guidelines for a 90-kg man and a 50-kg woman does not make intuitive sense. It has been demonstrated that a patient’s capacity to reabsorb pleural fluid, and avoid pleural fluid accumulation, can be estimated as a fraction of whole-body lymphatic flow (≈1 mL/kg/hour) which is dependent on body weight (29). The maximum pleural lymphatic flow that can occur without overwhelming pleural lymphatic reabsorption is approximately 40% of whole-body lymphatic flow. After lung surgery, it is reasonable to expect a disruption in pleural fluid circulation as a result of parenchymal resection and the inflammatory response associated with surgical trauma. For the purposes of carrying out our aforementioned prospective randomized trial, we agreed on a conservative fluid output guideline of 15% of daily whole-body lymphatic flow as a safe threshold for chest tube removal. Of the 176 study participants, 135 underwent a lobectomy and 41 had a segmentectomy or a wedge resection. The proportion of patients who had VATS resection was similar between these two groups [98/135 (73%) vs. 26/41 (63%); P=0.33]. The average 24-hour fluid output was statistically equivalent for lobar and sublobar resections (238±132 vs. 197±122 mL; P=0.08). However, in keeping with the hypothesis that surgical trauma disrupts pleural fluid reabsorption, thoracoscopic resection was associated with a significantly lower average daily fluid output than the open approach for both lobar resections (208±108 vs. 319±154 mL; P<0.01) and sublobar resections (153±91 vs. 274±134 mL; P<0.01). In this prospective cohort, a fixed volume threshold of 400 mL per 24 hours would have represented a percentage of whole-body lymphatic flow ranging from 11% to 46% [median =23%; interquartile range (IQR) =4%]. For some patients, this fixed-volume guideline would have exceeded the predicted maximum pleural reabsorption rate, and likely lead to pleural fluid accumulation. We think that using a target pleural fluid reabsorption rate, as a percentage of whole-body lymphatic flow, is best suited to variations in patient size commonly encountered in clinical practice. An increase in the selected threshold from 15% to 20% of whole-body lymphatic flow would have been associated with a range of acceptable 24-hour fluid output of 172–715 mL (median =350 mL; IQR =58 mL). In the absence of any other contraindications, the proportion of patients that would have been eligible for chest tube removal based on a 20% whole-body lymphatic flow threshold would have been: 72% on postoperative day 1, 67% on postoperative day 2, 81% on postoperative day 3, 87% on postoperative day 4, and 88% on postoperative day 5. In comparison, our selected threshold to 15% of whole-body lymphatic flow effectively reduced the proportion of patients potentially eligible for chest tube removal by 16–23% on the first 3 postoperative days. On postoperative day 4 and 5, the threshold selected (i.e., 15% or 20%) has a relatively small impact on the proportion of patients who become candidates for chest tube removal (1–6%). Analysis of our institutional data and review of the available literature suggest that, in the absence of a clinically significant air leak, it would be safe to remove all chest drains providing that the 24-hour fluid output is ≤20% of whole-body lymphatic flow (i.e., approximately 5 times the patient’s weight in kilograms).

Chest tube suction versus water seal

Upon review of the evidence in support of the use of intra-pleural suction in chest tube management, it becomes clear that there is no scientific consensus. Creating guidelines is therefore challenging and, unfortunately, the door remains wide open for idiosyncrasies. Table 2 summarizes seven randomized controlled trials and three meta-analyses comparing suction to water seal in the management of chest tubes. It should be noted that the meta-analyses were performed using data from a subset of the seven randomized trials. As summarized in a meta-analysis, all trials reviewed have significant potential for bias (11). The majority of the trials do not report sample size calculations or rigorously follow the CONSORT guidelines (27). All trials do consistently report prolonged air leak as a primary outcome but do not consistently report duration of chest tube and length of stay in hospital. Two of the seven trials and one of the three meta-analyses report an advantage to using water seal (12,30,31). One of these trials found a decrease in pneumothorax with suction in patients with a significant air leak (greater than four out of seven on an analogue scale) (30). However, four trials and two meta-analyses report no difference in incidence of prolonged air leak and duration of chest drain between water seal and suction (10,11,32,34-36). One trial compared water seal alone to a regimen of alternating suction at night with water seal during the day (33). The trial found the alternating regimen yielded a lower incidence of air leak lasting longer than 7 days, a shorter duration of chest drainage and a shorter postoperative hospital stay. This study was performed using analogue drainage device. The authors hypothesize that using suction at night allows apposition of the visceral and parietal pleura while water seal during the day allows early mobilization of the patient. New digital device provide continuous portable suction allowing patients to mobilize while maintaining negative intra-pleural pressure. Only one of seven trials used a digital drainage system to provide active physiologic pleural pressure regulation or provide active negative intra-pleural pressure regulation finding no benefit to negative intra-pleural pressures (37).

Table 2 Literature on the use of suction and water seal after pulmonary resection
Full table

There are a few possible explanations for the conflicting evidence found in the literature with regard to the use of chest tube suction: (I) there is no cause and effect relationship between the use of suction and relevant clinical outcomes; (II) variation in chest tube management protocols introduced bias in the pooled analyses to a degree that is difficult to quantify; and (III) the analogue devices used in the trials are inaccurate and prone to inter-observer variability. Similar to other physiologic systems, it is possible that the time required for a defect in the lung parenchyma to heal may not depend on the pressure in the pleural space. Significant heterogeneity in chest tube management between studies was reported in two of the three meta-analyses (11,38). Conventional, water-sealed pleural drainage systems have been associated with poor inter-observer reliability and are deficient with regard to air leak monitoring over time. Therefore, detection and objective quantification of air leaks, especially when these are small and intermittent, can pose a significant challenge. We previously reported a poor inter-observer agreement amongst members of the surgical team when recording air leak level at the bedside after pulmonary resection (39). We demonstrated that inter-observer reliability was significantly improved with the use of digital devices. Increased adoption of this technology may generate more scientific data on the role of intra-pleural suction and assist in the development of evidence-based guidelines.

Chest tube removal

Removal of a chest tube is a very common task performed during the care of thoracic surgery patients. As part of a chest tube pathway, this task should be standardized so that all team members, including nurses and residents at various stages of training, can provide high-quality care in the removal of chest drains. A prospective randomized controlled trial reported the incidence of pneumothorax after removal of chest tubes after full expiration with a Valsalva maneuver (16%) was significantly less than removal after full inspiration with a Valsalva maneuver (32%, P=0.007) (40). Another randomized trial had previously showed no difference in the incidence of residual pneumothorax after removing chest drains with a Valsalva maneuver either at full inspiration or at full expiration (41). The phase of inhalation or exhalation is not likely as important as a Valsalva maneuver to ensure positive intrathoracic combined with rapid removal of the drain to prevent pneumothorax.

There is ongoing debate on whether a trial of water seal is required prior to removal of a chest tube. A prospective randomized study of 80 trauma patients examined the difference in outcomes between removal of pleural drains while on suction versus water seal (42). The results show that weaning from suction prior to removal prolonged chest tube drainage by an average 20 hours, and lead to an increased number of chest X-rays to monitor care. This study concluded that chest tube removal on suction was safe, and that protocols requiring water seal before removal led to a longer hospital stay and more frequent chest X-rays. Another prospective randomized trial of 205 patients with a similar study design concluded that removal of chest tubes on water seal decreased the incidence of recurrent pneumothorax (13.9% vs. 8.0%, P<0.05) (43). Despite the increased incidence of recurrent pneumothorax, in the group of patients that had their chest tube removed on water seal the probability of requiring chest tube re-insertion was lower (6.2% vs. 10.7%, P<0.05). On initial analysis, there was no significant difference in chest tube duration or hospital length of stay. However, if chest tube replacement was required the hospital length of stay doubled. The authors rationalize that a period of water seal may allow occult air leaks to become clinically apparent as a pneumothorax and thus avoid the need for chest drain re-insertion. These limitations of analog pleural drainage systems have been address by new digital drainage devices which are very sensitive and provide air leak trend monitoring preceding chest tube removal eliminating the need for a trial of water seal. Lastly, the studies are likely underpowered to detect adverse events from chest tube removal. At our institution we have found a probability of chest tube re-insertion after removal of a chest drain is approximately 6%. A much larger sample size (i.e., several hundred patients in each arm) would be needed to power a study to detect a 50% reduction in this particular adverse event.

Conclusions

While there may be a lack of consensus on several aspects of chest tube management, there is ample evidence supporting the use of postoperative clinical pathways to improve patient care and allow for earlier discharge from hospital after lung resection. Our strategy is to create a chest tube management pathway that can gain wide acceptance has been primarily focused on a few key aspects of chest tube care. Based on our our review of recent literature and on institutional data, we conclude that: (I) chest X-rays should be used selectively in the care of lung resection patients with chest drains; (II) there is no strong evidence to recommend the use of intra-pleural suction over water seal; (III) it is safe to remove pleural drains at a 24-hour fluid output threshold much higher than what was previously recommended; (IV) that, with the integration of digital pleural drainage technology into clinical practice, chest drains can be safely removed without a trial period of water seal.

Given the current state of the evidence, we acknowledge that the optimal chest tube management strategy has yet to be established. However, thoracic surgeons should develop a pathway that can be consistently used for all patients at their institution. Digital pleural drainage technology will provide an opportunity to generate new evidence-based guidelines and allow an improved understanding of postoperative intra-pleural mechanics. With proper implementation and close monitoring of outcomes, clinical care pathways can assist our endeavors to maintain and improve surgical quality, and allow judicious use of costly and often limited healthcare resources.

Acknowledgements

None.

Footnote

Conflicts of Interest: The authors have no conflicts of interest to declare.

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