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Eur J Cardiothorac Surg 2005;27:391-394
© 2005 Elsevier Science NL

A prospective randomized controlled trial of suction versus non-suction to the under-water seal drains following lung resection

^a Guy's Hospital, London SE1 9RT, UK
^b Clinical Operational Research Unit, University College London, London, UK

Received 28 September 2004; received in revised form 29 November 2004; accepted 6 December 2004.

^* Corresponding author. Tel.: +44 7957 168 754; fax +44 2077 018 737. (E-mail: tom.treasure{at}ukgateway.net).

	Abstract

Top Abstract 1. Introduction 2. Material and methods 3. Results 4. Discussion 5. Conclusion References

 
Objective: Practice varies as to whether or not suction is applied to under-water seal drains following lung surgery. We tested the null hypothesis that there is no difference with respect to air leak duration. Methods: Patients undergoing thoracotomy or video assisted thoracoscopic surgery for lobectomy or wedge resection had either low-pressure suction or no suction applied to their underwater seal bottles postoperatively. Patients were allocated using minimization, a method of unbiased allocation ensuring balance between the arms of a trial with respect to known or suspected confounding factors. The trial was powered for duration of air leak. If an air leak persisted on the 7th post-operative day, the surgeon determined further management. Kaplan–Meier survival analysis of air leak duration and a log rank test were performed on an intention-to-treat basis, with observations censored at 144h (6 complete days). Results: Of the 254 patients that entered the trial, data were available for analysis for 239 (123 no-suction and 116 suction). There was no significant difference in the cumulative persistence of air leaks between the two groups (P=0.62) and inspection of the Kaplan–Meier curves suggests that any difference is negligible. Conclusions: Applying suction to the underwater seal drains following lung surgery makes no difference in terms of air leak duration. In the light of this finding we have adopted a uniform policy of no suction being applied to the underwater seal, from the time of surgery, unless a specific clinical judgment is made to use it. The anticipated gains are that this will reduce work and cost and aid mobilization.

Key Words: Prospective randomized trial • Lung resection • Suction • Chest drains

	1. Introduction

Top Abstract 1. Introduction 2. Material and methods 3. Results 4. Discussion 5. Conclusion References

 
Chest drainage tubes are routinely placed in the pleural space following thoracic surgery. Whenever the lung is operated upon chest tubes are connected to a one-way escape valve (commonly an under-water seal) so that any persisting air or continuing air leak can escape through a low resistance path. This preserves negative pressure in the pleural cavity and permits lung re-expansion. Under-water seal allows easy inspection and quantification of air leak. The transparent drain bottle allows fluid to be characterized (serous effusion, blood, pus or chyle) and measured.

The under water seal system has the additional advantage that suction can be applied to the chamber beyond the under-water seal. There are two schools of thought regarding suction in this context: for and against. Those of the former opinion apply low-pressure suction (usually about 2kPa). The objective is to expedite the drainage of air and fluid and to eliminate the residual space thereby hastening the expansion of the lung. Those of the latter persuasion do not use suction. They cite the bedside observation that the magnitude of an air leak is considerably greater when the patient is on suction and argue that this might cause the leak to persist when it might otherwise have healed up.

There have been several carefully performed randomized controlled trials to test which of these practices can be supported on evidence [1–4]. However, in all of these studies suction was used initially and then after a period of hours to a day, those allocated to the non-suction arm had the suction disconnected. Since all patients had suction for the first day and thus were exposed to what may have been either a beneficial or deleterious effect in what may well be the most critical phase, the fundamental question as to whether suction is beneficial remains unanswered. We designed our study to establish if there was a difference between a total policy of suction versus non-suction.

	2. Material and methods

Top Abstract 1. Introduction 2. Material and methods 3. Results 4. Discussion 5. Conclusion References

 
2.1. Participants
Between June 2002 and February 2004, all patients under the care of participating surgeons undergoing lung surgery were eligible for inclusion in the trial. These included lobectomy and wedge resections. Patients undergoing lung volume reduction surgery (LVRS) were excluded. The hospital Ethics Committee approved the study. Informed consent was obtained from each patient.

2.2. Interventions
At the end of the operation all chest drains were connected to underwater seal drainage without suction for transfer to the recovery room. We use two drains for lobectomy and one for most video assisted thoracoscopic surgery (VATS) procedures. If there are two one is apical and one basal. If there is one it is usually apical. The allocation to suction yes/no was made at completion of the operations, after the drain placement, so that it could not influence any part of the operative practice. Post operative management included patient controlled analgesia in all patients and paravertebral lignocaine infusion in thoracotomies. It was specified before randomisation and adhered to irrespective of the arm of the trial.

Patients allocated by computer program (Minim) [5] to no suction had no suction. Those allocated to suction had the air space above the water seal connected to a wall-mounted suction via a regulator set at 2kPa. Temporary disconnection for transfer was permitted and, as is our usual practice, patients were allowed to be disconnected from suction for periods not exceeding 15–30min at a time, to mobilise.

Chest tubes were regularly assessed for air leaks and fluid drainage. A specialist registrar or a consultant surgeon determined resolution of air leaks. Chest tubes were removed when there was no air leak and the fluid drainage was less than 200ml/day. Chest radiographs were taken on post-operative day 1, and for patients still with a drain on day 3, day 7 and following chest tube removal.

2.3. Outcome measures
Our primary outcome measure was air leak time (time to last bubble seen). Secondary outcomes included the incidence of persistent air leak (air leak lasting at least 6 complete days). On the seventh post-operative day the consultant surgeon could choose the subsequent management of the chest drain.

2.4. Allocation
Patients underwent unbiased allocation by minimization (MINIM) [5]. Factors for minimization were smoking, sex, surgeon (consultant or trainee), age, type of resection, thoracotomy or VATS procedure and likelihood of leak as perceived by the surgeon at the end of the procedure. At the end of the operation the computer generated allocation was communicated to the recovery room by telephone. The surgeons were blinded to the allocation process. The nature of the interventions precluded any subsequent blinding.

2.5. Statistical methods
Data were prospectively entered into a Microsoft Access 2000 database (Microsoft, Seattle, Washington, USA) and analyzed using SPSS Version 7 (SPSS, Chicago, Il, USA). Analysis was planned on an intention-to-treat basis. The cumulative persistence of air leaks within the two groups was calculated using Kaplan–Meier survival analysis. A log-rank test was performed to test the null-hypothesis of there being no difference in air leak persistence between the two groups. Data were censored at 144h, the earliest time at which management changes could be considered within the protocol. The incidence of leaks that persisted beyond 144h was calculated for each arm along with exact 95% confidence intervals.

	3. Results

Top Abstract 1. Introduction 2. Material and methods 3. Results 4. Discussion 5. Conclusion References

 
The flow of participants through each stage of the trial is depicted in Fig. 1. Of 328 eligible patients, 254 were allocated (126 to suction and 128 to non-suction). A further three patients gave consent but were mistakenly not entered into the trial. For the remaining 71 cases, either consent was not obtained or members of the research team were not available to communicate the allocation on the evening of surgery. Data were not collected for 15 of the 254 patients leaving 239 cases for analysis (116 suction and 123 non-suction).

View larger version (15K): [in this window] [in a new window]   Fig. 1. A summary of the recruitment of patients into the trial. * Three of these 74 patients gave consent but were mistakenly not entered into the trial.

View larger version (15K): [in this window] [in a new window]   Fig. 2. Kaplan–Meier curves of the cumulative persistence of air leaks in the two arms of the trial.

	4. Discussion

Top Abstract 1. Introduction 2. Material and methods 3. Results 4. Discussion 5. Conclusion References

Why have these four previous studies [1–4] used suction initially and then disconnected it? In the case of Cerfolio's study [1] the reason is quite clear. This was an enforced change by the hospital Institutional Review Board (their ethics committee). To not use suction at all was deemed unethical. This is concerning. Ethics committees are there to ensure safe and ethical research practice not for members to influence studies based on what Cerfolio calls a ‘preconceived notion’ about something as mechanistic and amenable to study as the management of chest drains. The inappropriate use of research governance has been challenged in the British Medical Journal [6].

Three of the four previous RCTs found an advantage for ‘non-suction’ [1–4] (Table 3). The fourth [2] found no difference. However since the non-suction arm in all the trials was contaminated by an initial period of suction, the effectiveness of avoiding suction altogether remained unproven. The results of our study displayed in Fig. 2 strongly suggest that there is no significant difference in persistence of air leaks between patients that receive suction. Any advantage of one strategy over the other must be negligible, although it should be stated that the study was not designed to establish equivalence.

On the basis of these findings we have adopted a policy for all surgeons in our unit of not adding suction to under-water seal unless it is specifically judged to be indicated. This has the advantages of simplicity and earlier mobilization and is expected to result in some cost savings and a reduction in nursing tasks to be performed.

	5. Conclusion

Top Abstract 1. Introduction 2. Material and methods 3. Results 4. Discussion 5. Conclusion References

 
Our trial together with earlier studies provides evidence that the use of suction following routine lung resection does not reduce air leak duration (Table 3).

	Acknowledgments

 
The authors wish to acknowledge the efforts of Julie Downer RN and all the nursing staff of the Thoracic Surgical Ward at Guy's Hospital for ensuring compliance with the study protocol.

	Footnotes

 
^☆ Presented at the joint 18th Annual Meeting of the European Association for Cardio-thoraic Surgery and the 12th Annual Meeting of the European Society of Thoracic Surgeons, Leipzig, Germany, September 12–15, 2004.

	References

Top Abstract 1. Introduction 2. Material and methods 3. Results 4. Discussion 5. Conclusion References

 

1. Cerfolio RJ, Bass C, Katholi CR. Prospective randomized trial compares suction versus water seal for air leaks. Ann Thorac Surg 2001;71(5):1613-1617.[Abstract/Free Full Text]
2. Brunelli A, Monteverde M, Borri A, Salati M, Marasco RD, Al Refai M, et al. Comparison of water seal and suction after pulmonary lobectomy: a prospective, randomized trial. Ann Thorac Surg 2004;77(6):1932-1937.[Abstract/Free Full Text]
3. Marshall MB, Deeb ME, Bleier JI, Kucharczuk JC, Friedberg JS, Kaiser LR, et al. Suction vs water seal after pulmonary resection: a randomized prospective study. Chest 2002;121(3):831-835.[Abstract/Free Full Text]
4. Ayed AK. Suction versus water seal after thoracoscopy for primary spontaneous pneumothorax: prospective randomized study. Ann Thorac Surg 2003;75(5):1593-1596.[Abstract/Free Full Text]
5. Treasure T, MacRae KD. Minimisation: the platinum standard for trials? Randomisation doesn't guarantee similarity of groups; minimisation does. Bio Med J 1998;317(7155):362-363.
6. Warlow C. Clinical research under the cosh again. Br Med J 2004;329(7460):241-242.[Free Full Text]
7. Anyanwu AC, Treasure T. Surgical research revisited: clinical trials in the cardiothoracic surgical literature. Eur J Cardiothorac Surg 2004;25:299-303.[Abstract/Free Full Text]

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