Issue and challenges of fluid removal in the critically ill

Defining fluid removal in the intensive care unit: A national and international survey of critical care practice

Design and objectives

To identify and compare how intensive care unit specialists in the United Kingdom and Australia and New Zealand self-reportedly define, assess and manage fluid overload in critically ill patients using a structured online questionnaire.

Results

We assessed 219 responses. Australia and New Zealand and United Kingdom intensive care unit specialists reported using clinical examination findings, bedside tools and radiological features to assess fluid status, diagnose fluid overload and initiate fluid removal in the critically ill. An elevated central venous pressure is not regarded as helpful in diagnosing fluid overload and targeting a clinician-set fluid balance is the most popular management strategy. Renal replacement therapy is used ahead of more diuretic therapy in patients who are oligo/anuric, or when diuretic therapy has not generated an adequate response.

Conclusions

This self-reported account of practice by United Kingdom and Australia and New Zealand intensivists demonstrates that fluid overload remains poorly defined with variability in both management and practice.

A mini volume loading test (mVLT) using 2.5-mLkg-1 boluses of crystalloid for indication of perioperative changes in hydration status

BACKGROUND AND OBJECTIVE

A mini volume loading test (mVLT) evaluating hemodilution during step-wise crystalloid infusion has established that the arterio-capillary plasma dilution difference is inversely correlated to the body hydration level of subjects. This observational study aimed to test whether this can be replicated in a perioperative setting using a 2.5-mLkg^-1 boluses.

MATERIALS AND METHODS

The mVLT was performed before induction of regional anesthesia and 24h later. Step-wise infusion implied six mini fluid challenges. These consisted of 2.5-mLkg^-1 boluses of Ringer's acetate infused during 2-3min and followed by 5-min periods with no fluids. Invasive (arterial) and noninvasive (capillary) measurements of hemoglobin were performed before and after each mini fluid challenge, as well as after a 20-min period without fluid following the last bolus. Hemoglobins were used to calculate the arterio-capillary plasma dilution difference which is used as an indication of changes in body hydration level. The 24-h fluid balance was calculated.

RESULTS

Subjects were 69.5 (6.0) years old, their height was 1.62m (1.56-1.65), weight was 87.0kg (75.5-97.5) and body mass index (BMI) was 33.5kg/m² (31.0-35.1). Preoperative arterio-capillary plasma dilution difference was significantly higher than postoperative (0.085 [0.012-0.141] vs. 0.006 [-0.059 to 0.101], P=0.000). The perioperative 24-h fluid balance was 1976mL (870-2545).

CONCLUSIONS

The mVLT using 2.5-mLkg^-1 boluses of crystalloid was able to detect the higher postoperative body hydration level in total knee arthroplasty patients.

Principles of Fluid Management

Fluid therapy is the most common intervention received by acutely ill hospitalized patients; however, important questions on its optimal use remain. Its prescription should be patient and context specific, with clear indications and contradictions, and have the type, dose, and rate specified. Any fluid therapy, if provided inappropriately, can contribute unnecessary harm to patients. The quantitative toxicity of fluid therapy contributes to worse outcomes; this should prompt greater bedside attention to fluid prescription, fluid balance, development of avoidable complications attributable to fluid overload, and for the timely deresuscitation of patients whose clinical status and physiology allow active fluid mobilization.