Prediction of the Effect of Fluid Administration Using Arterial Pressure and Ventilator Data During Abdominal Surgery

University of Aarhus52 enrolled

Overview

It is well known, that patients with circulatory impairment sometimes, but not always, benefit from intravenous fluids. Predicting if a fluid administration will improve circulation is therefore of substantial clinical interest. Ventilator treatment induces cyclic variation in blood pressure due to interaction between the lungs and the heart. This variation is minor, but its amplitude may be used for guiding fluid administration. However, this method of using ventilator-induced variation in blood pressure to predict the effect of fluid administration was developed when different settings for ventilator treatment was recommended, compared with today. With today's recommend ventilator treatment, the method is, unfortunately, less reliable. The investigators will investigate how different ventilator settings influence variation in blood pressure, and the investigators will test if this knowledge allows us to better predict the effect of a fluid administration, by taking the ventilator settings into account.

Study Type

OBSERVATIONAL

Enrollment

Conditions

Hypovolemia Fluid Overload

Interventions

Series of ventilator settings

Before a planned fluid administration, the investigators will apply a series of 10 ventilator settings for 30 seconds each. The settings are the following combinations of respiratory rate (RR) and tidal volume (TV): RR (min\^-1), TV (ml/kg predicted body weight) 31, 6 31, 8 24, 6 24, 8 17, 6 17, 8 10, 4 10, 6 10, 8 10, 10 (the order of the respiratory rates: 17 to 31, will be randomized. 10/min will always be last. Tidal volume is always applied from lowest to highest for each respiratory rate).

Eligibility

Sex: ALLMin age: 18 Years

Medical Language ↔ Plain English

Inclusion Criteria: * Scheduled open abdominal surgery. * Scheduled treatment with Aarhus University Hospital's goal-directed therapy protocol (hemodynamic monitoring). Exclusion Criteria: * Left ventricular ejection fraction ≤ 40 % * Irregular heart rhythm (e.g. atrial fibrillation or frequent ectopic beats) * Known right ventricular dysfunction (if reported qualitatively in pre-operative assessment or objectively via Tricuspid Annular Plane Systolic Excursion (TAPSE) \< 17 mm) * Pregnancy * Prior participation in this study

Outcomes

Primary Outcomes

>10% Increase in stroke volume from before to after a fluid bolus. (Fluid responsiveness)

A patient is considered a fluid responder if they have a \>10% increase in stroke volume (pulse contour analysis by the Edwards EV1000 with a FloTrac sensor). Pre-fluid stroke volume is calculated as the median stroke volume estimate in the two minutes immediately preceding the fluid bolus. Post-fluid stroke volume is calculated as the median stroke volume estimate in the two minutes immediately following the fluid bolus. Change in stroke volume is calculated as: 100% \* (Post-fluid stroke volume - Pre-fluid stroke volume) / Pre-fluid stroke volume

Time frame: From two minutes before to two minutes after a fluid administration.