Use of a Mini-fluid Bolus to Identify Fluid Responsiveness

Adult patients whom the Consultant Intensivist decides should receive a fluid challenge as part of their standard care in order to improve haemodynamic parameters will be approached. Reasons for fluid administration include evidence of inadequate tissue perfusion such as raised blood lactate or poor urine output, hypotension or attempts to wean vasopressor dose.

Patients will be identified as suitable for inclusion by the Consultant Responsible for the Intensive Care Unit on each day. As fluid responsiveness is a transient phenomenon which disappears after significant fluid resuscitation it is proposed that patients will be immediately entered into the study so that the study contains a mix of fluid responsive and non-responsive patients in order to get the time critical data required which may be lost if there is a significant delay before study entry. Informed consent will be sought from the patient, or if they are incapacitated by critical illness, their relative will be approached for assent as soon as possible and within 48 hours of study enrollment. This is in line with recommendations for Research involving emergency treatment.

The LiDCOrapid machine will be connected in the same manner as the LiDCOplus machine, currently in use on ICU, in order to obtain the stroke volume measurement. A smartcard is inserted and the patient details entered. Monitoring will continue until fluids are clinically indicated. Patients will be given fluid boluses via either peripheral or central venous catheters.

The following data will be collected for each patient:

Age, Gender, Height, Weight, diagnosis requiring ICU admission, location of venous and arterial catheters, APACHE II scores, Cumulative fluid balance at time of bolus administration, Ventilation status (self-ventilating, non-invasive ventilation, invasive ventilation and mode if appropriate), tidal volume if measured, drugs being infused (sedatives, inotropes, vasoactive drugs, diuretics, muscle relaxants, etc), presence of renal replacement therapy.

Fluid administration protocol:

Patients will be monitored just prior to infusion for hemodynamic stability, Standard practice is to administer a bolus of 500ml given via an infusion pump at a rate of 1200mL/hour (25min).

For study patients the first 250ml will be given in 50ml boluses using a 50ml syringe. Each bolus will be given over approximately 1 minute and the study measurements will be recorded followed by a wait for response of 1 minute. This will be repeated for each subsequent bolus until 250ml has been given (i.e. 5 boluses). The remaining 250ml will be given via the standard infusion pump method at a rate of 1000ml/hour which will complete in 15 minutes. In total, the 500ml will be given over 25 minutes.

At the end of each bolus Stroke volume, cardiac output, heart rate, blood pressure will be determined.

Up to 2 sets of data per patient per day will be collected. The majority of patients routinely stay in the ICU for 2 days, while in a smaller group, for much longer. A maximum of 4 data sets will be collected per patient. The fluid boluses will be administered at the discretion of the treating physician who believes that they will improve the clinical condition of the patient. The study team will have no influence on the timing of these.