Volume of fluid required
The volume of fluid needed depends upon the following factors[22,25]:
1) Resuscitation fluid
- Shocked patients (↑heart rate, ↑capillary refill time):
- 20ml/kg of 0.9% (normal) saline over 15 minutes
- If required, further 10ml/kg boluses up to a maximum of 40ml/kg at which point inotropes should be considered
- Boluses for shocked patients should not be subtracted from the fluid deficit
- Non-shocked patients
- 10ml/kg bolus of 0.9% (normal) saline over 60 minutes
- Do not give more than 10ml/kg without decision with the responsible consultant
- Boluses for non-shocked patients should be subtracted from the fluid deficit
2) Fluid deficit
- Deficit (ml) = % dehydration X weight (kg) X 10
- Assume 5% dehydration in mild DKA (pH<7.3 or serum bicarbonate <15mmol/L)
- Assume 7% dehydration in moderate DKA (pH<7.2 or serum bicarbonate <10mmol/L)
- Assume 10% dehydration in severe DKA (pH<7.1 or serum bicarbonate <5mmol/L)
3) Maintenance fluid
-
- Calculations are based upon body weight using the Holliday-Segar formula:
| 1st 10kg = 100ml/kg/day Plus 50ml/kg/day for next 10kg Plus 20ml/kg/day for each additional kg above 20kg (up to a maximum of 80kg total body weight) |
- For DKA fluid calculations this volume needs be doubled as correction occurs over 48 hours[23,33-34]
- APLS maintenance fluid calculations over-estimate requirement (particularly at younger ages) & should NOT be used
4) Fluid calculation
| Hourly rate = (Deficit/48 hours) + maintenance per hour |
- Correction should occur over 48 hours[23,33-34]
- Care should be taken when calculating fluid requirement & this should be documented in the patient’s notes
- Do not give additional fluid to replace urinary losses
- Greater volumes of fluid given within the first 4 hours have been shown to increase the risk of cerebral oedema[35]
- BSPED have an online DKA fluid calculator[36]
Example
What is the fluid requirement for a 20kg boy who has a pH of 7.15 who is not clinically shocked?
Answer
Fluid bolus= 10ml x 20kg = 200ml
Deficit percentage= 7%
Deficit volume= 7% x 20kg x 10 = 1400ml
Deficit volume minus bolus volume = 1400ml – 200ml = 1200ml
Deficit replacement rate = 1200ml ÷48 hours = 25ml/hour
Daily maintenance volume (using Holliday-Segar formula) = 1500ml
Maintenance rate = 1500ml ÷ 24 = 62.5ml/hour
Starting fluid rate = deficit replacement rate + maintenance rate = 87.5ml/hour
Insulin infusion rate = 0.05 units/kg/hour x 20kg = 1.0 units/hour
