Antibiotic lock therapy in paediatric patients: primum non nocere.

Antimicrobial lock therapy (ALT) is recommended by the Infectious Diseases Society of America (IDSA) as the standard of care for certain infections associated with central venous access devices (CVADs) since 2009.¹

ALT consists of instilling high concentrations of antimicrobials, usually 1000 times the minimum inhibitory concentration, into the lumen of an infected catheter, where the solution remains for a specified period.

Moreover, in ALT, a substance with anticoagulant activity such as heparin can be used together with antibiotics to maintain the patency of the catheter. It is also believed that it improves the penetration of antibiotics into the microbial biofilm by interfering with fibrin formation in the catheter lumen.² Accordingly, IDSA guidelines recommend combinations of antibiotic and heparin at high concentrations (2500–5000 IU/mL of sodium heparin).¹

However, the addition of heparin is controversial since it may cause precipitation. It also adds a risk of haemorrhagic accidents if the lock therapy is not maintained in the catheter lumen and reaches the patient’s bloodstream, especially in patients with low weight, as is the case in the paediatric population.³ IDSA recommendations on the management of CVADs infections do not contemplate specific measures for paediatric patients due to the limited evidence available.

Considering ALT as a high-risk medication, in our centre, the use of lower concentrations of heparin (10–100 IU/mL) has been implemented, except for aminoglycosides since these antibiotics may precipitate with lower heparin concentrations (table 1).

Table 1.

Final concentrations of antibiotic lock solutions used in our centre for the treatment of catheter-related bloodstream infection.

Antibiotic	Dosage (mg/mL)	Heparin dosage (IU/mL)
Amikacin	2	2500
Gentamicin	1	2500
Amphotericin	5	10–100
Cefazolin	5	10–100
Ceftazidime	5	10–100
Teicoplanin	10	10–100
Vancomycin	5	10–100

Another fundamental aspect for the security ALT is the volume to be instilled. IDSA guidelines recommend the use of a sufficient volume to fill the catheter lumen, usually between 2 and 5 mL. However, in paediatrics, volumes required are usually smaller and variable, depending on the size of the child and the catheter used.

Usually, the volume of the catheter lumen is listed in the manufacturer’s file; however, in paediatric patients, it is common to shorten the infusion line before insertion. In these cases, it is recommended to measure the total volume by flushing the line with normal saline and aspirate until blood flow is seen in the syringe.

Following this line of thought, Cober et al ⁴ proposes to use a lock volume equivalent to the volume of the catheter lumen+0.1 mL in the case of patients under 15 kg and 0.2 mL for those over 15 kg, a proposal that seems reasonable to avoid systemic administration of the ALT.

In addition, in our centre, ALT is prepared in the pharmacy service, in a horizontal laminar flow cabinet that ensures aseptic conditions. Likewise, these elaborations are identified with a warning note with the message ‘Antibiotic lock therapy: ensure topical administration’.

In conclusion, through simple measures, by reducing heparin concentration to 10–100 IU/mL when mixture stability allows it, ensuring adequate lock volume for the patients’ venous access, maintaining aseptic conditions in the preparation and correctly identifying the ALT, the safety of ALT administration could be guaranteed.

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