Persistent Hypoglycemia, Newborn, N/IICU — Diagnostic Fast — Clinical Pathway: ICU

Diagnostic Fast

Maximum Duration of Fast
  • < 1 mo: 12-18 hrs
  • 1-12 mos: 18-24 hrs
  • > 12 mos: 24-36 hrs
Prior to Fast
  • Place blood drawing IV if possible
  • Ensure sample tubes are at bedside
  • Review specimen requirements
  • Obtain point of care (POC) blood glucose (BG) and POC betahydroxybutyrate (BOHB) if available
Start of Fast
  • Allow child to feed
  • Immediately following feed child NPO, except for water
    • < 9 mos old: 1/4 normal saline
    • ≥ 9 mos old: water
Monitoring During Fast
  • Check POC BG and if available, POC BOHB
  • Repeat any BG < 70 mg/dL
  • POC BG frequency
    • ≥ 70 mg/dL: q 3 hrs
    • 60-69 mg/dL: q 1 hr
    • 50-59 mg/dL: q 30 min
  • Send STAT confirmatory serum glucose to lab if POC BG < 50 mg/dL
End of Fast Criteria
  • End fast if:
    • BG < 50 mg/dL or BOHB > 2.5 mmol x 2 or
    • Maximum duration of fast is reached or child becomes symptomatic — See hypoglycemia rescue
End of Fast Testing
Hypoglycemia Rescue and Monitoring
  • After testing is complete, allow child to feed
  • If symptomatic or unable to feed, give 2 ml/kg D10W
  • Check BG q20-30 mins until BG > 70 mg/dL
  • Check BOHB q1hr until < 1 mmol/L

Diagnostic Fast Example

Fast Time
(Hours)
Actual Time Glucose
(mg/dL)
BOHB
(mmol/L)
Feeds/Interventions
0 6:00 p.m. 85 0.1 90 ml formula
3 9:00 p.m. 88 0.1 NPO
6 12:00 a.m. 63/68 0.3 NPO
7 1:00 a.m. 60/65 0.3 NPO
8 2:00 a.m. 57/59 0.4 NPO
8.5 2:30 a.m. 51/55 0.6 NPO
9 3:00 a.m. 44/48 0.9 Lab glucose 46 mg/dL
Critical sample obtained
9.5 3:30 a.m. 47/49   Glucagon 1 mg given
  3:40 a.m. 60/64    
  3:50 a.m. 78    
  4:00 a.m. 102    
  4:10 a.m. 110   Testing complete
90 ml formula