It's 5 am and the lab calls with a critically low calcium level of 5.5. What should you do?
A. Stop everything and page the doctor out of a dead sleep to report the critical finding?
B. Calculate the corrected calcium level to possibly avoid interrupting yours and the doctor's work flow?
In my experience as a hospitalist, 99.99999999999999999% of the time a critically low calcium level is not a critical as determined by the laboratory parameters. Nurses who understand how to interpret a low calcium can safely choose option B without concern for sanctions from their superiors.
I've had this type of discussion before, most recently with the low urine output quandary. In addition, I've talked about critical lab values when hospitals don't allow nurses the ability to use their judgement not to call physicians. I have in the past written do not call parameters at least five times a day and yet I still get called with clock like precision.
I'm here to educate all nurses that have ever walked this earth on why it's not necessary to call the critically low calcium level 99.99999999999% of the time. Most of the time the reported lab value isn't critical. How should a decreased level be interpreted?
About 99% of a body's calcium is found in bone. Of the 1% that isn't, about 50% of it is free in a metabolically active ionized form and 40% is bound to albumin. When a lab reports a calcium level, they are reporting a lab who's value is determined by the album level in the patient's body. If the patient's albumin level is low, the reported calcium level will be low as well. This is what prevents a decreased calcium level from being a critically low calcium level the vast majority of the time. If an effort is made by a nurse who understands how to correct the low calcium level for the patient's albumin level, action plan B can safely be implemented 99.9999999999% of the time.
The corrected calcium formula is very simple. For every one gram below four a patient's albumin level is reported, you must increase the reported low calcium level by 0.8. So if the lab calls with a calcium level of 5.5 and the patient's albumin level two days ago was 1.0, you must increase that 5.5 by ((4-1)*0.8) or 2.4 and you get 7.9 for the corrected calcium level. Clearly this is out of the critical range. Action plan B could saftely be initiated and this patient will survive another moment in noncritical critical lab theater. This is called the corrected calcium level. After correction for albumin, rarely is the calcium in the critical range. If after correcting for albumin, the calcium level remains critically low, than perhaps action plan A should be considered.
Critical calcium levels are rare in the hospitalist population. The differential diagnosis of hypocalcemia is quite limited and having a critically low level is very uncommon. I suspect the actual incidence of my service could be counted on one hand over the last seven years. Hopefully this free source of continuing medical education will help nurses divert unnecessary calls to physicians all across this country by not calling noncritical critical calcium levels, levels which can be better understood through the application of science and math.
Critical calcium levels are rare in the hospitalist population. The differential diagnosis of hypocalcemia is quite limited and having a critically low level is very uncommon. I suspect the actual incidence of my service could be counted on one hand over the last seven years. Hopefully this free source of continuing medical education will help nurses divert unnecessary calls to physicians all across this country by not calling noncritical critical calcium levels, levels which can be better understood through the application of science and math.
