It’s hard to believe we used to administer an IV-drug combo called the “coma cocktail” – 25 grams of dextrose, 100 milligrams of thiamine and 2 milligrams of naloxone – to patients with altered mental status of unknown etiology. Even if you started riding in the 2000s you’ve probably heard of that concoction, but I doubt you’re still giving it.
Let me rephrase: I hope you’re not still giving it. Thanks to the emergence of prehospital glucometry in the mid 1990s, (and the practice of titrating naloxone to somewhere between sleep and death), there’s no longer a reason to push megadoses of wake-up meds when they might be unnecessary or even harmful.
Identifying normal blood glucose levels in the field
Before we were able to check blood glucose in the field, a just-in-case amp of D50 was our hedge against hypoglycemia. Thiamine was supposed to help metabolize the sugar and prevent Wernicke’s encephalopathy, a severe mental disorder caused by B1 deficiency sometimes secondary to alcoholism and/or malnutrition, but now it’s questionable whether 100 mg of thiamine is even therapeutic in emergent hypoglycemia [1]. More importantly, Wernicke’s encephalopathy is one of the least likely consequences of a dextrose bolus [1].
Did you know infiltrated D50 can necrotize tissue [2]? I remember learning something about that in medic school, but I was more fixated on saving as many insulin-saturated diabetics as I could. For a young medic, it didn’t get much better than watching a comatose patient with snoring respirations suddenly wake up and ask what the hell was going on.
What we didn’t discover until at least 10 years after introduction of prehospital glucometry is that dextrose, even when administered through a patent line, can worsen the outcome of acute coronary syndromes. In a 2008 statement, the American Heart Association labeled hyperglycemia “a powerful predictor of survival and increased risk of in-hospital complications in patients both with and without diabetes [3].” Higher blood glucose levels were associated not only with vascular inflammation and degradation, but also with impaired glucose utilization leading to increased myocardial oxygen demand [3]. The AHA conceded, though, that post-ACS blood-glucose targets would have to wait for further studies [3].
Speaking of ischemia, the AHA also notes, in its 2015 version of ACLS, that ischemic strokes are worsened by hyperglycemia [4]. Our old coma cocktail is starting to look like voodoo medicine.
How accurate are prehospital blood glucose levels?
An early impediment to street glucometry was the CLIA (Clinical Laboratory Improvement Amendments) waiver that acknowledges blood sugar measurement is “a simple laboratory examination (with) an insignificant risk of erroneous result.” I’m not so sure about the “insignificant risk” part.
Merely carrying a glucometer doesn’t guarantee accurate glucose levels; devices must be calibrated regularly for source-specific blood – capillary or venous. Why? Because according to research, mean postprandial capillary blood glucose – the closer approximation of arterial blood glucose – is 35 percent higher than mean venous blood glucose [5]. That means if you dip a glucometer calibrated for finger sticks into IV flashback, you might understate the patient’s blood sugar and overtreat hypoglycemia.
The way you obtain blood samples matters, too. If you have to work hard at squeezing blood after a finger prick, your sample may be diluted by plasma or contaminated by debris. If the sample is too small, it might clot before being drawn onto the test strip.
Glucometry: An Underused Prehospital Tool?
The principal value of prehospital glucometry isn’t confirming hypoglycemia in insulin-dependent diabetics; it’s discovering when hypoglycemia is mimicking or contributing to unrelated conditions.
Even when blood glucose levels are easily obtained, hypoglycemia is often mistaken for alcohol intoxication, strokes, behavioral disorders and even head injuries. Smart prehospital providers check blood sugar even when AMS seems secondary to trauma.
Many years ago I responded to a motor vehicle accident involving a medical colleague. He was barely responsive to voice with a gash on his forehead. When I checked his blood glucose, it was dangerously low. He became alert after an amp of D50 en route. I didn’t know until we got to the hospital he was an insulin-dependent diabetic.
Glucometry grows up
Modern glucometers are much easier to use than the devices of 20 years ago. They’re smaller, much faster and they analyze blood hands-free. In fact, checking blood glucose has become so routine, some EMS systems have added it to their EMT curricula.
Now all we need is for patients to stop flinching when they’re stuck.
References
1. Bowman J. Thiamine before glucose, where’s the science? The Resuscitationist. Available at: www.resuscitationist.com
2. Lawson S, Brady W, Mahmoud A. Identification of highly concentrated dextrose solution (50% dextrose) extravasation and treatment – a clinical report. American Journal of Emergency Medicine. 2013;31:886.e3-886e5.
3. Deedwania P, Kosiborod M, Barrett E, et al. Hyperglycemia and Acute Coronary Syndrome. Circulation. 2008;117:1610-1619.
4. American Heart Association. Advanced Cardiac Life Support Provider Manual. 2016.
5. Yang C, Chang C, Lin J. A Comparison between Venous and Finger-Prick Blood Sampling on Values of Blood Glucose. International Proceedings of Chemical, Biological and Environmental Engineering. 2012;39:206-210.
