This month, we will look at the final part of a fluid therapy plan – accounting for ongoing losses. This can be challenging, but some general rules can be helpful.
First, let’s recap the four parts of a fluid therapy plan:
- Perfusion deficit
- Hydration deficit
- Maintenance requirements
- Ongoing losses
When considering ongoing losses, try to not forget about patients with pre-existing polyuric diseases; chronic renal failure is a prime example. Patients with dehydrated chronic renal failure are unlikely to suddenly regain concentrating ability. Polyuria should be considered as an ongoing loss.
Other conditions that may result in additional urinary fluid losses include post-obstructive diuresis, diabetes mellitus, hyperadrenocorticism and hyperthyroidsim.
How much to add?
This is the tricky part. I often add an additional half to one maintenance and frequently reassess clinical parameters, or if a urinary catheter is placed matching ins and outs.
Gastrointestinal tract losses can be collected and weighed; 1g of vomitus or diarrhoea can be roughly equivalent to 1ml of water.
Fluid removed from drains placed in cavities or wounds should also be measured and accounted for.
Remember the key point is regular assessment of the patient’s hydration status, from repeat clinical exams, to track their response. Don’t forget regular retesting of electrolytes – for example, every 12 to 24 hours for patients on IV fluids and not eating.