What is the expected drainage volume from pleural and mediastinal chest tubes after heart surgery?

Expected Chest Tube Drainage After Heart Surgery

After cardiac surgery, there is no universally established "normal" drainage volume threshold, but chest tubes are typically removed when drainage is less than 100-200 mL per 24 hours, with practice varying widely between institutions due to lack of high-quality evidence specific to cardiac surgery. 1

Key Drainage Expectations

Initial Drainage Period

• Meticulous monitoring of chest tube drainage is critical to surgical outcomes after cardiac surgery, as pooling of shed mediastinal blood correlates with complications including pericardial and pleural effusions 1
• A small volume of residual blood is expected within the mediastinum after cardiac surgical procedures 1
• The amount of drainage varies significantly based on surgical procedure type, with CABG, valve replacements, and aortic interventions showing different drainage patterns 1

Removal Thresholds: The Evidence Gap

The critical issue is that chest drain management in cardiac surgery remains largely tradition-based rather than evidence-based 1. Current practice is governed by institutional standards passed down from mentor to trainee, creating wide variability between and within institutions 1

Practical Management Approach

When to Consider Removal

While specific cardiac surgery data is limited, the available evidence suggests:

• Traditional practice typically removes drains at 100-200 mL/24 hours, though this threshold lacks robust validation 1
• Studies in thoracic surgery (which provide the best available proxy data) demonstrate safety with higher thresholds up to 450-500 mL/day 1, 2
• No significant differences in reintervention rates, complications, or mortality occur with higher drainage thresholds (250-500 mL/day) in thoracic surgery patients 2

Critical Monitoring Parameters Beyond Volume

• Character of drainage: Serous fluid versus bloody drainage matters more than volume alone 1
• Absence of air leaks: Essential criterion regardless of fluid volume 1
• Clinical status: Respiratory function, oxygen saturation, and symptoms guide decision-making 3
• Imaging findings: Chest X-ray or ultrasound assessment of residual collections 1, 3

Important Caveats and Pitfalls

Suction Level Affects Output

• Higher suction levels (-20 cm H₂O) produce significantly more fluid output than lower suction (-5 cm H₂O) 4
• After 24 hours: 523 ± 215 mL with high suction versus 338 ± 265 mL with low suction 4
• Switching to water seal after 12 hours of wall suction is safe and does not increase complications compared to continuous wall suction until removal 5

Drain Type Considerations

• Silicone-rubber (Blake) drains yield 71% more drainage with 49% decrease in pericardial effusion volume compared to semirigid drains 1
• No significant differences in mediastinal exploration rates (2.08% vs 3.47%) or pleural effusion requiring drainage (9.87% vs 9.54%) between Blake drains and conventional chest tubes 6

Post-Removal Effusions

• Pleural effusions requiring subsequent drainage occur in approximately 9-10% of cardiac surgery patients regardless of drain type 6
• Most post-cardiac surgery effusions can be managed conservatively or with thoracentesis rather than requiring drain reinsertion 1
• Ultrasound can quantify effusions using the formula: V (mL) = 16 × D (mm), where D is the distance between diaphragm and visceral pleura 3

Clinical Decision Algorithm

1. Monitor drainage volume, character, and clinical status continuously 1
2. Consider water seal transition after 12 hours if drainage is decreasing and patient is stable 5
3. Remove drains when:
   • Drainage is serous (not bloody) 1
   • Volume is decreasing trend toward <200 mL/24h (traditional threshold) 1
   • No air leaks present 1
   • Patient is clinically stable with adequate respiratory function 3
4. Accept that some patients will develop effusions requiring later intervention (approximately 10%), but this does not mandate prolonged drainage 6

The fundamental limitation is that chest drain management after cardiac surgery remains an area with significant practice variation and insufficient high-quality evidence to establish definitive thresholds 1. Clinical judgment incorporating drainage trends, fluid character, and patient status remains paramount until better evidence emerges.