mrcem2-1628

mrcem2-1628

A 45 year old female presents to the emergency department with a 4 day history of persistent vomiting, severe diarrhea, and loss of appetite. The patient reports feeling extremely weak. A peripheral cannula is inserted and blood samples are collected. The initial laboratory results are as follows:

Sodium (Na+): 134 mmol/L
Potassium (K+): 2.4 mmol/L
Urea (Ur): 8.2 mmol/L
Creatinine (Cr): 115 umol/L

Based on these findings, which of the following additional tests should be prioritized and requested?