Saline Lock and IV Fluid Discontinuation
Yes, when a saline lock is ordered, you should discontinue continuous IV fluids. A saline lock (intermittent infusion device) is specifically designed to maintain IV access without continuous fluid infusion, and its use indicates that ongoing fluid administration is no longer necessary or appropriate 1, 2.
Understanding the Purpose of Saline Locks
A saline lock serves as an intermittent infusion device that maintains patent IV access while eliminating the need for continuous fluid administration 1, 2. The device is:
- Flushed with normal saline (typically 2 cc of 0.9% saline) to maintain patency 2
- Used when IV access is needed for potential medication administration or emergency access, but continuous fluids are not indicated 2, 3
- Appropriate for patients who do not require fluid resuscitation, volume replacement, or constant drug infusions 2, 3
When to Transition from Continuous IV to Saline Lock
Postoperative Setting
Discontinue IV fluids when oral intake is adequate. For most patients undergoing elective surgery, intravenous fluid therapy is unnecessary beyond the day of operation 1. Specifically:
- Encourage oral fluids as soon as patients are awake and free of nausea 1
- Start oral diet on the morning after surgery for most procedures 1
- When adequate oral fluid intake is tolerated, discontinue IV administration and restart only if required to maintain fluid and electrolyte balance 1
Maintenance Fluid Considerations
The decision to convert to a saline lock should be based on:
- Patient's ability to maintain hydration orally 1
- Absence of ongoing fluid losses requiring replacement 1
- No need for continuous medication infusions 2, 3
- Potential need for intermittent IV access for medications or emergency situations 2, 3
Saline Lock Maintenance Protocol
Flushing Technique
Central venous access devices can be safely flushed and locked with saline solution when not in use 1. The protocol includes:
- Flush with sterile 0.9% sodium chloride for catheter lumens in frequent use 1
- Use 1-2 cc of normal saline from prefilled syringes for peripheral saline locks 2
- Repeat flush only after medication administration 3
Heparin Considerations
Heparinized solutions should be used as a lock only when recommended by the manufacturer 1:
- For implanted ports or open-ended catheter lumens scheduled to remain closed for more than 8 hours 1
- Not necessary for short closure periods (<8 hours) 1
- Most hospital PN treatments delivered by continuous infusion do not require heparinization 1
Clinical Advantages and Cost Considerations
Practical Benefits
Saline locks offer multiple advantages over continuous IV fluid administration 2, 3:
- Less time-consuming to initiate and maintain (70% of paramedics reported) 2
- Easier to use (65% of paramedics reported) 2
- Facilitates patient transportation and mobility (92% of paramedics reported) 2
- Reduces fluid overload risk by eliminating unnecessary continuous infusion 4, 5
Cost Savings
Significant cost reduction occurs with saline lock use compared to traditional IV setups, with documented savings of $130 to hospitals and $1,710 to patients or carriers in one study 3.
Critical Pitfalls to Avoid
Do Not Use Saline Locks When:
- Active fluid resuscitation is required for shock states 2, 3
- Continuous medication infusions are necessary 2, 3
- Ongoing fluid losses require replacement (vomiting, high stoma output) 1
- Patient cannot maintain adequate oral intake 1
Fluid Overload Risks
Continuing unnecessary IV fluids can cause significant harm 1, 4:
- Fluid overload of as little as 2.5 L causes increased postoperative complications and prolonged hospital stay 1
- Excess fluid causes hyperchloremic acidosis, decreased renal blood flow, impaired tissue oxygenation, and delayed GI recovery 1
- Fluid stewardship principles dictate discontinuation when no longer indicated 4, 5
Monitoring Patency
Check saline lock patency upon arrival to clinical areas 3: