Acid/base And Fluid Homeostasis In Hospital

Question 1

Default fluid regimen for someone who is ‘nil by mouth’

Answer 1

• 4mL/kg/hr for first 10 kg
• 2 mL/kg/hr for second kg
• 1 mL/kg/hr for kg after that
• in reality not giving more than 3L; which is practically 1L of 0.9% saline and 2L 5% dextrose

Question 2

Examples of how patients may lose fluids and in what composition

Answer 2

• fever: sweat (water, NaCl)
• diabetes mellitus: urine (water, glucose, NaCl, KCl, phosphate)
• vomiting: gastric contents (water, HCl, KCl)
• diarrhoea: faeces (water, NaCl, KCl)
• burns: plasma and evaporation (water, NaCl, protein)
• haemorrhage: blood (RBC, all electrolytes)

Question 3

Patients to be cautious with giving fluids and why

Answer 3

Patients to be cautious with:

• elderly: 20-25 mL/kg/day
• obese: do not exceed 3L
• heart, renal failure (especially those on dialysis), liver failure (reduced albumin, osmotic pressure)

Can precipitate:

• decompensated heart failure
• pulmonary/generalised oedema
• electrolyte derangement

Question 4

Complications of delivery options

Answer 4

• peripheral lines: infection, thrombosis, air embolism

- central lines: misinsertion causing arterial bleeds, thrombosis, embolism of the line, erosion, air embolism

Question 5

Types of fluid

Answer 5

• crystalloid: forms true solutions, pass freely through semi-permeable membranes. Pros: Safer and cheaper. Cons: Remain in intravascular space for less time, thus need greater volume to achieve effect
• colloid: do not form true solutions, do not pass freely through semi-permeable membranes. Pros: remain in the intravascular space and can act as plasma expanders. Cons: cost, hidden electrolytes, allergens, effects of coagulation, renal failure/osmotic nephrosis
• hartmanns: the physiological fluid, most in A&E would use this

Question 6

Conclusions for fluid use

Answer 6

Give crystalloid, probably hartmann’s