Admission weight vs Daily weight for FICK?

[Suivezmoi89, BSN]

So at my previous hospital we had tons of really sick hearts, and generally for CO/CI calculation we did FICKs or a continuous monitor. For our FICKs we had a specific formula that requested the daily weight, and then the answer (CO) was divided by the BSA to get the CI.

At this new hospital they mostly do thermodilution, but have started using FICKs, everyone is telling me that they use the admission weight and BSA for all calculations, never the daily.

Was just curious what y'all's hospitals did. Updated daily weights and BSA were such a big deal for FICK calculations at my old hospital, it's bizarre to see people so adamant about the opposite. (They obviously get daily weights, just don't use them for their CO/CI calculation)

[MunoRN, RN]

Once the initial weight is entered, whether it's admission weight or euvolemic weight, it should not be changed.

It may be useful if the patient's admission weight is severely hypervolemic and then there is significant volume loss to separately calculate a more accurate CI when using thermodilution, or CO when using Fick, using the more accurate euvolemic weight, but it should be separated from the trended original weight, changing the weight being used in the trend will skew the trend.

Thermodilution directly measures CO, then uses height and weight to approximate oxygen metabolic demands to then calculate a CI. Fick directly measures and calculated oxygen metabolic demand and then uses height and weight to calculate a CO.

Day to day changes in weight don't reflect changes in the amount of oxygen metabolizing tissue (unless the patient has had a limb amputated or something), daily weight changes typically represent changes in volume status and since water is not an oxygen metabolizing tissue, it should be calculated into the CO or CI when water retention or water loss occurs.