CBC count, blood cx, CSF analysis, cx, mono spot/EBV titers Infection, allergy Electrolytes, BUN, CR, glucose, Ca, PO4 , Mg, LFTs, ammonia, TFTs Metabolic/endocrine disease, metabolic disturbance, disease Altered mental status Tetany Bleeding/clotting disorder, pulmonary embolism PT/PTT d-dimer Toxicologic screen blood, urine Nasal, ocular, rectal swab: DFA, PCR, cx Pulmonary embolism Ingestion/intoxication agitation will worsen distress ABG, VBG changes occur late and may not be seen until arrest (A-a) O2 gradient increase suggests ventilation– perfusion mismatch Relative contraindication for lumbar puncture if agitation or positioning will worsen distress Calculate anion gap Negative d-dimer excludes PE in patients with low pretest probability for PE Central nervous system depressants, neuromuscular blockade, electron transport chain poisons Bronchiolitis, Chlamydia Neonates, infants infection, pertussis, viral pneumonia