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Clinical Investigations: SURGERY |

Silastic Drains vs Conventional Chest Tubes After Coronary Artery Bypass* FREE TO VIEW

Timothy L. Frankel; Peter C. Hill; Sotiris C. Stamou; Robert C. Lowery; Albert J. Pfister; Arvind Jain; Paul J. Corso
Author and Funding Information

Affiliations: *From the Sections of Cardiac Surgery, Washington Hospital Center (Mr. Frankel, and Drs. Hill, Lowery, Pfister, and Corso) and Georgetown University Hospital (Dr. Stamou); and MedStar Research Institute (Mr. Jain), Washington, DC.,  Deceased.

Correspondence to: Timothy L. Frankel, BS, 3401 N Street NW, Washington, DC 20007; e-mail: tfrankel@gwu.edu



Chest. 2003;124(1):108-113. doi:10.1378/chest.124.1.108
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Published online

Study objectives: To investigate differences in drainage amounts and early clinical outcomes associated with the use of Silastic drains, as compared with the conventional chest tube after coronary artery bypass grafting (CABG).

Design: Retrospective nonrandomized case control study.

Setting: A tertiary teaching hospital.

Patients and participants: Outcome data from 554 patients who underwent postoperative pericardial decompression using small Silastic drains were compared with those from 556 patients who had conventional chest tubes after first-time CABG at our institution between January 1 and August 1, 2000.

Measurement and results: Univariate analysis of preoperative characteristics was used to ensure similarity between the two patient groups. Operative mortality, mediastinitis, reoperation for bleeding, and early and late cardiac tamponade occurred in 9 patients (1.6%), 6 patients (1.1%), 6 patients (1.1%), 6 patients (1.1%), and 1 patient (0.2%), respectively, in the Silastic drain group, compared with 11 patients (2.0%), 9 patients (1.6%), 4 patients (0.7%), 2 patients (0.4%), and 6 patients (1.1%) in the conventional group. No statistically significant differences between the two drains were identified. Drainage amounts (mean ± SD) were 552.2 ± 281.8 mL and 548.8 mL ± 328.7 mL for the Silastic and conventional groups, respectively (p = 0.51). Postoperative length of stay was longer for the conventional chest tube group (median, 5 d; range, 1 to 119 d) when compared to the Silastic drain group (median, 4 d; range, 1 to 66 d; p = 0.01).

Conclusions: We demonstrated that small Silastic drains are equally as effective as the conventional, large-bore chest tubes after CABG with no significant risk of bleeding or pericardial tamponade. Additionally, use of Silastic drains allows more mobility than the conventional chest tubes. As a result of this study, there was a change in our clinical practice toward the exclusive use of Silastic drains after all cardiac surgical procedures.

Figures in this Article

Thoracic decompression after cardiac surgery has traditionally been accomplished by placing large-bore chest tubes (28F to 36F) in the mediastinal and pleural spaces, allowing accumulating fluid to drain. Despite a history of relative safety and efficacy, alternatives to the cumbersome and sometimes painful conventional large-diameter chest tubes are now being sought. Preliminary reports suggest that small Silastic drains may be superior to the conventional chest tube in patient tolerability, earlier ambulation, and improved pulmonary toilet.12 While increasing patient comfort, the smaller, more flexible Silastic drain may also be less likely to injure adjacent structures or unsettle coronary grafts. The presence of recessed channels along the sides of the Silastic drain (Fig 1 ) allows for a greater tissue contact area and diminishes tissue invagination into the drain.,12 This provides more efficient drainage while minimizing tissue trauma and pain on drain removal. The benefits of the Silastic drain over the conventional chest tube should contribute to a less complicated and better tolerated postoperative recovery course. We sought to investigate the differences in drainage amounts and early clinical outcomes of small Silastic drains compared to conventional chest tubes after first-time coronary artery bypass grafting (CABG).

Patients

The computerized database of the Section of Cardiac Surgery at the Washington Hospital Center was used to identify all patients who underwent first-time CABG between January 1 and August 1, 2000, and postoperatively received either a Silastic drain or a conventional chest tube (n = 1,113). Patients who received both Silastic drains and conventional chest tubes were excluded (n = 3). Selection of chest tube drainage system was based on surgeon preference. Patients were grouped and compared according to drain type: conventional vs the Silastic drain (BLAKE Drain; Ethicon, Inc., a Johnson & Johnson Company; Somerville, NJ). In those receiving conventional chest tubes (n = 556, 50.1%), postoperative drainage was achieved using either one or two 32F chest tubes placed in the mediastinal space and attached to a Pleur-evac suction device (Genzyme Corporation; Cambridge, MA). Unless drainage was excessive (> 150 mL over 8 h), the conventional tube(s) was removed the morning after the operation. When indicated, additional tubes of the same type were placed in pleural spaces. In the group receiving the Silastic drain (n = 554, 49.9%), postoperative drainage was accomplished via placement of two 19F flexible Silastic drains, one placed inferiorly within the cardiac well and the other anteriorly overlying the epicardial surface. A bulb reservoir (Allegiance; Allegiance Healthcare Corporation; McGaw Park, IL) was connected to the free ends to facilitate patient mobility (Fig 2 ). Drains were secured to the skin with nylon suture. In the event of excessive drainage or detection of an air leak, the bulb reservoir was replaced with a Pleur-evac suction device. Drains were removed the morning of postoperative day 2 unless drainage rates remained high. If necessary, additional Silastic tubes were placed in the pleural spaces. The decision to keep the Silastic drain in place for an extra day was based on the clinical judgment of the cardiac team, and proper measures have been taken to adjust for this difference.

Data Collection

Data were collected from the in-house database, patient charts, and through follow-up interviews conducted 30 days after discharge from the hospital. Data on drainage amounts were collected on a randomly selected subset of 600 patients (300 patients from the conventional tube group and 300 patients from the Silastic drain group).

Definitions
Preoperative Variables:

Chronic renal insufficiency was defined as serum creatinine value ≥ 2.0 mg/dL. Recent myocardial infarction (MI) was defined as an MI occurring within 24 h before CABG.

Postoperative Variables:

Early cardiac tamponade was defined as tamponade occurring while chest tubes were still in place. Late cardiac tamponade was defined as tamponade occurring after chest tubes or Silastic drains were removed, but before discharge from the hospital.

Risk Stratification

A Parsonnet risk-stratification model3 was used for risk adjustment to control for potential between-group imbalances in perioperative outcomes. Parsonnet scores are derived from 47 risk factors for mortality during open-heart operations, with 0 being low risk and > 20 being extremely high risk.3

Statistical Analysis

Preoperative data are reported as percentages for categorical variables or mean and SD for continuous variables. Preoperative risk factors were selected from the components of the Parsonnet bedside risk score. Continuous variables were compared using a Student t test. Comparisons of ordinal categorical data were done using Cochran-Armitage test for trends. All other comparisons were made using a χ2 test for independence, unless a Fisher exact test was more appropriate. To investigate study outcomes by drain type, univariate comparisons were made using a Fisher exact test. All tests were two sided; p values < 0.05 were considered significant.

Preoperative Characteristics

A total of 1,110 patients were included in the present study. The Silastic drain group included 554 patients (388 men and 166 women) with a median age of 65 years (range 31 to 95 years). The conventional group consisted of 556 patients (396 men and 160 women) with a median age of 67 years (range, 34 to 97 years). There were no patients in whom the Silastic drains were subsequently replaced by a conventional chest tube due to a complication or inadequate drainage. Preoperative patient characteristics are presented in Table 1 . With respect to the preoperative risk factors by drain type (Table 1) , the conventional and Silastic drain groups are quite similar. The Parsonnet risk scores for the conventional and the Silastic drain groups were 13.9 and 13.1, respectively (p = 0.15). The Silastic drain group patients were slightly younger than the conventional drain group patients (64.3 years vs 65.5 years), with a p value of 0.05; however, multivariate analysis (data not shown) indicated that in this study, age had no effect on measured outcomes. The only other potential study confounder is the occurrence of an MI within 24 h before surgery; however, when fitting a logistic regression model to estimate the odds of operative mortality between drain types, adjusting for recent MI did not alter the inference: odds ratios of 1.2 (p = 0.66) and 1.1 (p = 0.88) for unadjusted and adjusted models, respectively. As none of the preoperative risk factors are deemed potential confounders, we conclude that the two drain groups are similar with regards to preoperative risk factors, and present univariate analyses for comparing outcomes between groups.

Outcomes Analysis

The outcomes by drain type are presented in Table 2 . Operative mortality was slightly higher in the conventional drain group vs the Silastic drain group at 11 patients (2.0%) and 9 patients (1.6%), respectively (p = 0.82). Mediastinitis rates between the Silastic and conventional drain groups were 1.1% (n = 6) and 1.6% (n = 9), respectively (p = 0.60). Six patients who received a Silastic drain (1.1%) returned to the operating room for bleeding, compared with four patients (0.7%) from the conventional drain group (p = 0.55). Early postoperative cardiac tamponade (while chest tubes were still in place) was experienced by six patients (1.1%) from the Silastic drain group and two patients (0.4%) from the conventional drain group (p = 0.18). The incidence of late postoperative cardiac tamponade (after the chest tubes have been removed) was lower in the Silastic drain group when compared to the conventional chest tube group, at 0.2% (n = 1) and 1.1% (n = 6), respectively (p = 0.12).

Drainage Amounts

Because the conventional chest tubes were routinely removed the morning following surgery whereas the Silastic drains were routinely removed the second morning following surgery, only data collected on drainage amounts through the first postoperative morning were used for comparison. These data are presented in Table 3 . The Silastic drain and conventional chest tubes drained comparable amounts of fluid: 552.2 ± 281.8 mL and 548.8 ± 328.7 mL, respectively (p = 0.51). No significant differences were identified in univariate comparisons of these variables.

Hospital and ICU Length of Stay

Patients from the Silastic drain and conventional drain groups left the ICU a median of 1 day after surgery (range, 1 to 26 days and 1 to 72 days, respectively) [p = 0.36]. Patients from the Silastic drain group had a shorter hospital length of stay (median, 4 days; range, 1 to 66 days) when compared to patients from the conventional drain group (median, 5 days; range, 1 to 119 days) [p = 0.01].

The placement of chest tubes following cardiac procedures is essential in decompressing the mediastinal and pleural spaces and preventing cardiac tamponade, and chronic restrictive pericarditis.4 Because of the serosanguinous nature of the fluid typically drained after cardiac operations, the use of large-bore, 32F to 36F rigid tubes has been the drainage modality of choice.5 Although the conventional chest tube has proven highly effective, it possesses many unwanted features. In addition to providing a great degree of discomfort to the patient, the rigid conventional chest tubes may compress coronary structures and/or unsettle bypass grafts.67 Misplacement of these thick rigid tubes has also resulted in serious complications such as dysrhythmia due to cardiac irritation,7 injury to the intercostal nerves,7 parietal pleura or lung parenchyma damage,7 erosion into major intrathoracic vessels,8 and cardiac tamponade.9 Further, thrombus formation may compromise their function and the conventional stripping of chest tubes to prevent thrombus formation has been associated with injury to adjacent structures.10 Chest tubes may also impair pulmonary function as previously recorded.11

Another shortcoming of the conventional chest tube is restriction of patient ambulation following surgery. Its large size and rigidity restricts breathing and causes sufficient pain to limit the degree a patient can comfortably move. Conventional chest tubes also require a larger and more cumbersome drainage reservoir (the Pleur-evac), forcing patients to remain anchored to their beds until the chest tube is removed. Both of these shortcomings contradict the current philosophy of rapid ambulation and early discharge.2

The concept behind the development of the Silastic drain was to create a more flexible, smaller-diameter drainage tube with the same efficacy as the conventional chest tube. The Silastic drain is a 19F fluted noncollapsible silicone tube usually placed as a pair in the anterior and posterior mediastinal spaces. Grooves that run along the length of the tube promote fluid drainage while preventing tissue invagination and clot formation2(Fig 1) . Because of the increased pliability provided by the Silastic drain, there should be a decreased risk of tissue injury and erosion associated with their use compared to the conventional chest tube. Our study showed that the Silastic drain allows adequate drainage of the mediastinal space with comparable risks of major complications echoing previous reports.12 Along with its comparable safety and efficacy, the Silastic drain also benefits from a smaller collection device (the bulb reservoir), which can be attached to the patient’s gown allowing for greater freedom of movement.

Early Clinical Outcome

To assess the safety of the Silastic drain vs the conventional chest tube, we examined a set of complications related to the use of chest tubes. These complications included operative mortality, mediastinitis, reoperation due to bleeding, early cardiac tamponade, and late cardiac tamponade. Our data has revealed no significant difference in outcomes between those patients receiving the Silastic drain and those receiving the conventional chest tube.

Drainage Efficacy

To evaluate drainage efficacy, chest tube output through the first postoperative morning was compared. During this period, the Silastic drains averaged similar output to the conventional chest tubes, proving that along with providing equal if not greater patient comfort, they are as effective in draining fluid from the chest as the conventional chest tubes.

Hospital and ICU Length of Stay

Although there were no differences between the two groups with respect to postoperative ICU length of stay (p = 0.36), patients from the Silastic drain group had a statistically significant shorter overall hospital length of stay (p = 0.01). Though we cannot attribute this shorter length of stay to the chest tube alone, greater ease of ambulation in the early postoperative period may prevent deconditioning and/or immobility related morbidity allowing for a more rapid discharge.

Cost Analysis

The cost of utilization of the Silastic drain system is comparable to the conventional chest tube. The equipment needed includes two Silastic drains ($25 each) and one bulb reservoir ($15.10 each), for a total cost of $65.10. The equipment needed to use a conventional chest tube includes two chest tubes ($4.60 each), one Pleur-evac unit ($32 each), and 1 L of sterile water ($.70), for a total cost of $41.90.

Clinical Implications

Previous studies12 involving the Silastic drain have been limited by small sample size and a lack of comparison with conventional chest tubes. This study is the first case-control study on an unselected cohort of CABG patients with statistical power to compare the outcomes between the Silastic drains and the conventional chest tubes. We found that patients receiving the Silastic drain had similar clinical outcomes compared to those receiving conventional chest tubes. From this we have determined the Silastic drain chest tube can be used with the same safety and efficacy as the conventional chest tube. As a result of the study, there was a change in our clinical practice toward the exclusive use of Silastic drains after any cardiac surgical procedure, including redo sternotomies, valve surgeries, and reoperation for postoperative chest bleeding.

Study Limitations

Although our analysis is the largest comparing the Silastic drain with standard chest tubes, all the limitations of a single-institution retrospective methodology apply. Furthermore, univariate analysis may not adequately account for the inherent selection bias in nonrandomized data. However, retrospective studies with large-enough sample sizes, such as the one presented in this study, may be used to more accurately determine the significance of the Silastic drain vs the conventional chest tube drainage. Prospective randomized studies although of invaluable scientific merit are limited by the small sample size (type II statistical error) and significant cost.

Abbreviations: CABG = coronary artery bypass grafting; MI = myocardial infarction

This study was sponsored by an educational grant by the Ethicon, Inc., a Johnson & Johnson Company, Somerville, NJ.

Robert C. Lowery, MD, FCCP, is a paid consultant to Ethicon, Inc., a Johnson & Johnson Company, Somerville, NJ.

Figure Jump LinkFigure 1. Cross-section of Silastic drain (BLAKE Drain; Ethicon).Grahic Jump Location
Figure Jump LinkFigure 2. Silastic drain (BLAKE Drain; Ethicon) with bulb reservoir (Allegiance Healthcare Corporation).Grahic Jump Location
Table Graphic Jump Location
Table 1. Preoperative Risk Factors by Drain Type*
* 

Data are presented as No. (%), No., or mean (95% confidence interval).

 

Cochran Armitage trend test.

 

Student t test.

Table Graphic Jump Location
Table 2. Outcomes Rates by Drain Type*
* 

Data are presented as No. (%).

Table Graphic Jump Location
Table 3. Drainage Amounts and Pain Assessment Through the First Postoperative Morning by Drain Type
* 

Wilcoxon rank-sum test.

 

t-Test assuming unequal variances.

This study is dedicated to the memory of Albert J. Pfister, MD.

Obney, JA, Barnes, MJ, Lisagor, PG, et al (2000) A method for mediastinal drainage after cardiac procedures using small Silastic drains.Ann Thorac Surg70,1109-1110. [PubMed] [CrossRef]
 
Lancey, RA, Gaca, C, Vander Salm, TJ The use of smaller, more flexible chest drains following open-heart surgery: an initial evaluation.Chest2001;119,19-24. [PubMed]
 
Bernstein, AD, Parsonnet, V Bedside estimation of risk as an aid for decision-making in cardiac surgery.Ann Thorac Surg2000;69,823-828. [PubMed]
 
Smulders, YM, Wiepking, ME, Moulijn, AC, et al How soon should drainage tubes be removed after cardiac operations?Ann Thorac Surg1989;48,540-543. [PubMed]
 
Hyde, J, Sykes, T, Graham, T Reducing morbidity from chest drains.BMJ1997;314,914-915. [PubMed]
 
Svedjeholm, R, Hakanson, E Postoperative myocardial ischemia caused by chest tube compression of vein graft.Ann Thorac Surg1997;64,1806-1808. [PubMed]
 
Kollef, MH, Dothager, DW Reversible cardiogenic shock due to chest tube compression of the right ventricle.Chest1991;99,976-980. [PubMed]
 
Taub, PJ, Lajam, F, Kim, U Erosion into the subclavian artery by a chest tube.J Trauma1999;47,972-974. [PubMed]
 
Quak, JM, Szatmari, A, van den Anker, JN Cardiac tamponade in a preterm neonate secondary to a chest tube.Acta Paediatr1993;82,490-491. [PubMed]
 
Landolfo, K, Smith, P. Postoperative care in cardiac surgery. Sabiston, DC Spencer, FC eds.Surgery of the chest 6th ed.1996,230-286 WB Saunders. Philadelphia, PA:
 
Hagl, C, Harringer, W, Gohrbandt, B, et al Site of pleural drain insertion and early postoperative pulmonary function following coronary artery bypass grafting with internal mammary artery.Chest1999;115,757-761. [PubMed]
 

Figures

Figure Jump LinkFigure 1. Cross-section of Silastic drain (BLAKE Drain; Ethicon).Grahic Jump Location
Figure Jump LinkFigure 2. Silastic drain (BLAKE Drain; Ethicon) with bulb reservoir (Allegiance Healthcare Corporation).Grahic Jump Location

Tables

Table Graphic Jump Location
Table 1. Preoperative Risk Factors by Drain Type*
* 

Data are presented as No. (%), No., or mean (95% confidence interval).

 

Cochran Armitage trend test.

 

Student t test.

Table Graphic Jump Location
Table 2. Outcomes Rates by Drain Type*
* 

Data are presented as No. (%).

Table Graphic Jump Location
Table 3. Drainage Amounts and Pain Assessment Through the First Postoperative Morning by Drain Type
* 

Wilcoxon rank-sum test.

 

t-Test assuming unequal variances.

References

Obney, JA, Barnes, MJ, Lisagor, PG, et al (2000) A method for mediastinal drainage after cardiac procedures using small Silastic drains.Ann Thorac Surg70,1109-1110. [PubMed] [CrossRef]
 
Lancey, RA, Gaca, C, Vander Salm, TJ The use of smaller, more flexible chest drains following open-heart surgery: an initial evaluation.Chest2001;119,19-24. [PubMed]
 
Bernstein, AD, Parsonnet, V Bedside estimation of risk as an aid for decision-making in cardiac surgery.Ann Thorac Surg2000;69,823-828. [PubMed]
 
Smulders, YM, Wiepking, ME, Moulijn, AC, et al How soon should drainage tubes be removed after cardiac operations?Ann Thorac Surg1989;48,540-543. [PubMed]
 
Hyde, J, Sykes, T, Graham, T Reducing morbidity from chest drains.BMJ1997;314,914-915. [PubMed]
 
Svedjeholm, R, Hakanson, E Postoperative myocardial ischemia caused by chest tube compression of vein graft.Ann Thorac Surg1997;64,1806-1808. [PubMed]
 
Kollef, MH, Dothager, DW Reversible cardiogenic shock due to chest tube compression of the right ventricle.Chest1991;99,976-980. [PubMed]
 
Taub, PJ, Lajam, F, Kim, U Erosion into the subclavian artery by a chest tube.J Trauma1999;47,972-974. [PubMed]
 
Quak, JM, Szatmari, A, van den Anker, JN Cardiac tamponade in a preterm neonate secondary to a chest tube.Acta Paediatr1993;82,490-491. [PubMed]
 
Landolfo, K, Smith, P. Postoperative care in cardiac surgery. Sabiston, DC Spencer, FC eds.Surgery of the chest 6th ed.1996,230-286 WB Saunders. Philadelphia, PA:
 
Hagl, C, Harringer, W, Gohrbandt, B, et al Site of pleural drain insertion and early postoperative pulmonary function following coronary artery bypass grafting with internal mammary artery.Chest1999;115,757-761. [PubMed]
 
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