Intravenous fluids play an important role in the management of critically ill patients; they provide a means by which fluid balance can be maintained in the absence of adequate oral intake. While their administration should always be carefully planned and monitored, nowhere is this more important than within this patient group, who are particularly susceptible to fluid overload and electrolyte imbalances, which can increase the risk of complications and mortality.
Abnormal levels of sodium, potassium, magnesium, calcium and phosphate are commonly found in patients within the intensive care unit and appropriate selection of intravenous fluids and additions can be used to correct these. However, chloride levels are also frequently disturbed in critically ill patients, often as a result of intravenous fluid therapy that contains higher concentrations of chloride than usually present in the body. Yet, this has not been as well studied as other electrolyte imbalances.
Here we consider a piece of research featured in the Journal of the American Medical Association in 2012, which investigates the issue of chloride delivery through intravenous therapy for those who are critically ill.
A study published at the end of last year investigated the benefit of restricting the delivery of chloride via intravenous fluids to patients in the intensive care setting. This research focused on the impact of different levels of chloride administration on kidney function, as abnormally high chloride levels can reduce blood flow to the kidneys and impair their ability to filter the blood.
Those patients receiving lower levels of chloride through fluid therapy were significantly less likely to develop acute injury to their kidneys and as a result renal replacement therapy was not needed as frequently amongst these patients, both of which are usually indicators of a poorer prognosis.
The study was conducted by researchers at Monash University Sunway Campus in Malaysia and involved 760 control patients admitted to an intensive care unit during a six month period in 2008 who received standard intravenous fluids, followed by 773 patients in the next six months who received chloride-restricted intravenous fluids.
The outcome measures recorded were primarily the change in creatinine level – an indicator of renal function – and the incidence of acute kidney injury, though the use of renal replacement therapy, the length of intensive care unit and hospital stay and survival rate were also considered. Amongst those receiving the standard intravenous fluids their creatinine levels rose by 22.6μmol/L and incidence of acute kidney injury was 14%, compared to those who received the chloride-poor intravenous fluids who experienced a significantly lower 14.8μmol/L rise and 8.4% incidence.
The use of renal replacement therapy was also significantly lower amongst those receiving less chloride in their fluid therapy – 6.3% compared to 10%. These differences remained significant even when confounding variables were controlled for, though no difference was found between the two groups for the length of their stay in intensive care and hospital or their survival rate.
The findings that chloride-restricted intravenous therapy is associated with a lower incidence of acute kidney injury and renal replacement therapy add further weight to the argument that administration of chloride in fluid therapy for those who are critically ill needs to be carefully considered. However, additional research will be required before intensive care units change their prescription practices for intravenous fluids.
The results of one study is not sufficient evidence to re-evaluate the way that fluid therapy is given and some doubt has been cast on the design of this piece of research. It would have been expected that a significantly lower prevalence of acute kidney injury and the need to use renal replacement therapy would have translated into a shorter length of stay in hospital and a greater chance of survival, though this was not seen. Certainly the fact that the study was not conducted blind – those involved in the study knew which fluids were being administered – may have had an impact on the outcomes.
The choice of which intravenous fluids to prescribe for patients at present is often determined more by what is regarded as standard practice rather than what evidence from studies has shown to be optimal in certain physiological states, owing to the lack of research. Even though conclusive results may not be able to be drawn from this study, it certainly will encourage further research into the most appropriate fluid therapy for use with critically ill patients. This in turn will pave the way to review the recommendations in place for which intravenous fluids are best used in intensive care units.
Evelyn Graham is an expert in intensive care procedures. Having graduated in International Business and Journalism a few years ago, she has covered everything from science to local news, environment, sustainability issues and a lot in between.