Your ALS service is called to evaluate a 47-year-old female with epigastric pain that came on suddenly about six hours ago; she has vomited once. She thought it was the flu and that it would subside, but it has not. She smokes, is overweight and has a family history of early cardiac disease. Her vital signs are unremarkable and her belly is nontender. You perform a 12-lead ECG that shows nonspecific ST-T wave changes inferiorly. You place a few drops of blood obtained as part of your field-drawn bloods into an i-STAT cartridge. The result surprises you: Her cardiac enzyme (troponin I) is markedly elevated. Should she be transported to the closer facility without primary coronary intervention (PCI) capability or further down the road to a facility that has it?

     EMS has been performing point-of-care (POC) testing for years. Blood glucose determination is just one example of this concept. In the last few years, many EMS systems have expanded their ability to provide more definitive diagnostic information to the emergency departments they serve. What difference does it make? This is a legitimate question. EMS has been accused of not fully supporting its activities with quality research. This article will outline current uses of POC testing, limitations and future directions of this technology.

     One of the most commonly used POC testing instruments is the i-STAT (Abbott Point of Care, East Windsor, NJ). This is an easily operated, hand-held, battery-operated device with different insertable cartridges that run the various tests with a few drops of whole blood. The cartridges can test for electrolytes (sodium, potassium, calcium and chloride), glucose, blood urea nitrogen and creatinine (tests for kidney function), hematocrit and bicarbonate. Special cartridges test for beta natriuretic peptide (a test that aids in diagnosing heart failure) and troponin I (a cardiac-specific enzyme elevated in ACS). The device is easy to use and is as accurate as hospital laboratory testing.^1,2

POC TESTING By EMS

ELECTROLYTE EMERGENCIES
     One of the first research papers to look at this technology came from Grand Canyon National Park EMS providers, who showed the device could be used in a hot environment (daily temperatures of 107°F).3 They were able to identify seven out of 29 patients evacuated to their clinic with suspected heat-related illness who were actually hyponatremic (low serum sodium level). The device aided in field triage decisions and assisted in overnight management at ranger stations for visitors suffering from heat-related illnesses and hyponatremia when evacuation was impossible. The authors were one of the early groups to recognize that hyponatremia often presents similar to, and coexists with, heat illnesses.