Safety of Normal Saline in the Pleural Space
Normal saline can safely be introduced into the pleural space and is routinely used for various pleural procedures including flushing chest tubes, diluting fibrinolytic agents, and irrigation of the pleural cavity.
Evidence Supporting Safety of Normal Saline in the Pleural Space
Normal saline is commonly used in pleural procedures for several purposes:
Chest Tube Flushing: Guidelines recommend using normal saline to flush chest tubes when they become blocked. The BTS guidelines specifically state that if a chest tube becomes blocked, "it may be flushed with 20–50 ml normal saline to ensure its patency" 1.
Fibrinolytic Agent Dilution: Normal saline is the standard diluent for fibrinolytic agents used in pleural infections. The BTS guidelines for pediatric pleural infection recommend urokinase be diluted in "40 ml 0.9% saline for children aged 1 year or above, and 10 ml 0.9% saline for children aged under 1 year" 1.
Talc Slurry Preparation: For malignant pleural effusions, talc slurry is prepared by mixing talc with normal saline. The American Journal of Respiratory and Critical Care Medicine guidelines recommend "4–5 g of talc in 50 ml of normal saline" 1.
Pleural Irrigation with Normal Saline
Recent evidence shows that pleural irrigation with normal saline may be beneficial:
A randomized controlled pilot study demonstrated that patients receiving saline irrigation had a significantly greater reduction in pleural collection volume compared to standard care (32.3% vs 15.3% reduction) 2.
Significantly fewer patients in the saline irrigation group required surgical referral (p=0.03) 2.
No serious complications were documented with saline irrigation 2.
Technical Considerations
When introducing normal saline into the pleural space, several technical aspects should be considered:
Volume Control: For large effusions, drain clamping is recommended after initial removal of fluid (10 ml/kg) to prevent re-expansion pulmonary edema 3.
Drainage System: All chest tubes should be connected to a unidirectional flow drainage system (underwater seal bottle) kept below the patient's chest level 1, 3.
Monitoring: After unclamping a chest tube following saline instillation, the patient should be maintained on appropriate suction 1.
Safety Profile
Normal saline is physiologically compatible with the pleural space. The normal pleural fluid volume in healthy humans is approximately 0.26 ml/kg of body mass 4, and the introduction of saline for therapeutic purposes has not been associated with significant adverse effects when used appropriately.
Potential Applications
Beyond standard uses, normal saline has been studied for:
Pleural Infection Treatment: Saline irrigation (three times per day for 3 days) showed improved pleural fluid drainage in patients with pleural infection 2.
Electrolyzed Saline: A study using electrolyzed saline for irrigation of empyema spaces showed facilitation of rapid disinfection and closure of the empyema space with a 90% success rate 5.
Cautions
While normal saline is generally safe in the pleural space, care should be taken in certain situations:
- Never clamp a bubbling chest drain as this can lead to tension pneumothorax 3.
- Ensure proper positioning of chest tubes before instilling saline.
- Monitor patients for signs of discomfort or respiratory distress during and after saline instillation.
Normal saline is a safe and effective solution for use in the pleural space when used according to established guidelines and protocols.