Filtration and Intravenous Fluid Therapy

Intravenous (IV) therapy is an integral part of modern patient care and is used in the clinical management of more than a quarter of hospitalized patients. IV systems offer numerous benefits including rapid delivery of drugs and fluids to the patient and haemodynamic monitoring. Unfortunately IV systems also provide a direct route for micro-organisms to enter the blood stream. Despite excellent aseptic techniques and practices, nosocomial infections still occur in hospitalized patients, particularly those in critical care environments. It has been estimated that 8.5% of nosocomial infections can be attributed to intravenous catheter sepsis.

IV related septicaemia may be catheter associated or non-catheter associated and can arise from various sources eg. intrinsic catheter contamination, contaminated disinfectants, hands of medical personnel and the patient’s own skin microflora. Catheter hub manipulations have been acknowledged as an important contributor of IV related septicaemia particularly with central lines. Various approaches, including the use of strict aseptic techniques, can be used to minimise IV related septicaemia.

Septicaemia can also result from the delivery of contaminated fluids to the patient. Microbiological contamination of intravenous infusions can be either intrinsic or extrinsic in origin. Intrinsic contamination, where contamination occurs during manufacture, transport or storage, is a rare occurrence now-a-days, due to the excellent quality control procedures carried out by the pharmaceutical industry. However, in the early 1970s a number of cases of hospital acquired septicaemia, as a result of intrinsic microbial contamination, were reported. In one of these outbreaks seven patients became septic and five died postoperatively after receiving 5% dextrose contaminated with Gram-negative bacteria. Contamination was traced to faulty maintenance of autoclaving equipment at the Company’s manufacturing plant. Following these incidents, Departments of Health around Europe formulated hospital guidelines to minimise the clinical consequences should a similar event occur dur ing administration of IV infusions. One of these guidelines was that IV administration sets and the fluid flowing through them should, wherever possible, be changed every 24 hours.

Extrinsic microbial contamination is that which arises due to in-use manipulations of the IV system. Every manipulation of this system, including initial set up, subsequent addition of new solutions, the attachment of three-way taps, addition of medication to the hanging solution and CVP measurements increase the risk of introducing bacterial or fungal contaminants.

When a needle pierces an injection port a tiny meniscus of fluid remains. This damp, warm environment is ideal for microbial proliferation thus resulting in an innoculum culture when further injections are made. It has been reported that in-use contamination of infusion fluids exceeded 30% when additions were injected on the ward compared to a “background” rate of 14%. Marshall and Lloyd carried out a review of the literature and reported that the rate of in-line contamination of IV fluids ranges from 0-30% with an average value of 3%. Basically the more manipulations that are made to the system the greater the likelihood that inadvertent microbial contamination of the IV line will occur. Patients in critical care settings are likely to have a large number of manipulations to their comp lex systems. These patients are obviously particularly susceptible to infection.

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