A protocol to standardise intravenous fluid therapy after cardiac surgery

Introduction of a protocol to guide intravenous fluid resuscitation post cardiac surgery based on calculation of the "mean systemic filling pressure analogue" (Pmsa). Before-and-after trial comparing data after introduction of protocol to previously collected (retrospective) data from an earlier quality assurance audit, with the aim to reduce the amount of IV fluid administered post-operatively. Participants will be recruited upon arrival into the ICU immediately post-operatively. The Pmsa is calculated on arrival and then every 2 hours, or if the patient is not meeting MAP (mean arterial pressure) and CO (cardiac output) targets and the most recent Pmsa is more than 15 minutes old. The Pmsa is calculated from use of a Swan-Ganz catheter and the below equation: Pmsa = aCVP + bMAP + cCO where a = 0.96, b = 0.04 and c is determined from patient anthropometrics (height and weight). A spreadsheet will be loaded to the bedside computer with formulas for calculation, and at each time for calculation a CO will be measured by thermodilution using the Swan-Ganz catheter. The values for height, weight, MAP, CVP, and CO are entered into the spreadsheet to calculate Pmsa. The Pmsa is calculated regularly to guide fluid management, and treating clinician's are advised to avoid further IV fluid boluses once the Pmsa is above 17 (based on previous studies showing a Pmsa of 17 or higher indicates fluid non-responsiveness). This will be conducted by the bedside nurse and treating clinician (registrar/consultant) for each patient post-cardiac surgery in a tertiary ICU. Education will be provided on implementing the protocol and chart review will occur to determine compliance. Any consultants who do not wish to enrol a patient will be required to provide a reason for future inclusion/exclusion criteria.