You are a third year medical student working in Pediatric Emergency when your preceptor sends you to see an 18-month-old presenting with vomiting and diarrhea.

Mom describes a 2 day history of emesis (normal to bilious) and diarrhea, numerous times daily. She states her son has been taking in minimal fluids since the onset of symptoms. The child’s medical history is unremarkable and no infectious contacts have been noted. However, he attends daycare.

Physical examination findings are as follows:

General appearance: Lethargic 18-month-old boy 
Vital signs: HR 160 beats/min, BP 80/50, RR 26/min, T 37.8°C 
HEENT: Dry mucous membranes, eyes slightly sunken 
CVS: No murmurs noted; capillary refill time 3 sec 
Pulmonary: Chest clear to auscultation, no cough 
Abdo: Soft and nontender; diarrhea without mucous or visible blood 
Urinary: Has not voided in last 5 hours 
Skin: Skin turgor decreased

What is your priority at this time?