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Title: The fluid challenge technique : standardization of fluid administration and assessment of fluid responsiveness in critically ill patients
Author: Aya Bernal, Hollmann David
ISNI:       0000 0004 6349 7712
Awarding Body: St George's, University of London
Current Institution: St George's, University of London
Date of Award: 2016
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The objective of this thesis is to analyse the fluid challenge technique. The hypothesis is that a fluid challenge performed in different ways will lead to different results, and so different clinical decisions. If this were true, standardization of the technique would be desirable. The fluid challenge is a very heterogeneous technique. It is mainly used in the process of haemodynamic optimisation for both high-risk surgical patients and septic patients respectively. This therapeutic intervention reduces morbidity and the length of hospital stay for patients who have received cardiac surgery. In order to observe the effect of the fluid challenge, independent from the cardiac function, I measured surrogates of the mean systemic filling pressure (Pmsf). The Pmsf-analogue (Pmsa) increased in both responders and non-responders. The duration of the haemodynamic effect of a fluid challenge is similar in both groups after ten minutes. The least significant change of the Pmsf-arm, a second technique to estimate the Pmsf, is 14% with a single measurement. The minimal dose of crystalloids required to increase the Pmsf-arm by 14%, in a group of post-operative cardiac patients, is about 4 mL/Kg as a proportion to their total body weight. Importantly for this study, the proportion of responders increased along with the dosage of fluids used, confirming my initial hypothesis. A similar study was also conducted in septic patients using between 2 and 5 ml/Kg. None of the doses used increased the Pmsf-arm beyond the limits of precision, and the estimation suggests that about 10 ml/Kg would be required in this group of patients. Finally, no differences were observed in microcirculation after a fluid challenge of 4 ml/Kg between responders and non-responders. However, the baseline microcirculatory variables were good predictors of the changes after the fluid challenge. In conclusion, the response to a fluid challenge depends on the technique used. Full standardisation of this technique is necessary to avoid misleading interpretations.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available