UCONN Emergency Medicine Interest Group

Posts Tagged ‘critical care’

Off Service #3: Critical Care

In OFF SERVICE on February 4, 2012 at 5:19 PM

I’m in the ICU this month, where acid-base disorders are more the rule than the exception. One issue that frequently comes up is metabolic acidoses and the specter of mixed acid-base disorders looming its ugly head. I feel this topic is frequently made overly complex, and thus ends up being ignored, when figuring it out is really not that complicated. I think this is because of the delta gap, or in Dr. Henry’s words, the “delta-delta”:

Delta-delta = (measured anion gap from labs – normal anion gap)/(normal HCO3 – measured HCO3 from labs) = (measured anion gap from labs – 12)/(24 – measured HCO3 from labs)

I think this equation gets easily confused because of the fact that the calculation involves subtraction in the denominator. Since I am not particularly facile at math at the drop of a hat (or at least, not with an ICU team as my audience), I will outline the very simple way that I have reasoned how to determine if a mixed acid-base disorder is present, in a way that should be easy to remember:

In the setting of an INCREASED anion gap metabolic acidosis (AKA an anion gap metabolic acidosis):

If there is an additional METABOLIC ALKALOSIS…

HCO3 is HIGHER than it should be, therefore…
The denominator is SMALLER, therefore…
The delta-delta is BIGGER, and…
If the delta-delta > 2, there is an increased anion gap metabolic acidosis AND a metabolic alkalosis.

If there is an additional NON-ANION GAP METABOLIC ACIDOSIS…

HCO3 is LOWER than it should be, therefore…
The denominator is BIGGER, therefore…
The delta-delta is SMALLER, and…
If the delta-delta < 1, there is an increased anion gap metabolic acidosis AND a non-anion gap metabolic acidosis.

For a more comprehensive discussion, see this selective project created by a UCONN student here.

Why should you care? Well, particularly if you are resuscitating with large volumes of normal saline (which contains a lot of chloride), the pH may not give a full indication of what is going on with the patient, and you may make changes in your management accordingly. For instance, you might want to switch to Lactated Ringers as your IV fluid.

Click below to see a BONUS section on patients with hypoalbuminemia, and how not to miss metabolic disturbances in this population!

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Journal Article Synopsis: Is ED Hyperglycemia a Poor Prognostic Marker in Intracerebral Hemorrhage?

In JOURNAL CLUB on July 11, 2011 at 3:21 PM

Summary of “Emergency Department Hyperglycemia as a Predictor of Early Mortality and Worse Functional Outcome after Intracerebral Hemorrhage” By Latha G Stead et al, Neurocritical Care vol 13: pp. 67-74. 2010.

What is already known on this topic:
Hyperglycemia upon admission was already known to be a predictor for poor outcome in ischemic stroke. A relationship between hyperglycemia and mortality in intracerebral hemorrhage (ICH) had been suggested, but little data was present to define its prognostic ability.

What question this study addressed:
Is hyperglycemia at arrival associated with early mortality and functional outcome in patients with non-traumatic ICH?

What was the study design:
A prospective, cohort study of 237 adults presenting to the ED with CT confirmed, spontaneous ICH between 1/06 to 12/08, with a blood glucose measurement at presentation. Data was collected by two independent, blinded abstractors.

What this study adds to our knowledge:
This study showed that hyperglycemia (defined as blood glucose of ≥140) in both diabetic and non-diabetic patients is a prognostic predictor of higher mortality within 7 days. Among non-diabetics, it is also a predictor of poor clinical outcome  when controlled for stroke severity, age, and volume of hemorrhage. Furthermore, higher blood glucose values correlated with more severe stroke, measured by the NIH Stroke Scale. There was no significant difference shown among diabetic patients when glucose levels were used as a predictor for poor clinical outcome or stroke severity.

How is this relevant to clinical practice:
This study allows confirms that hyperglycemia is a red flag among patients presenting to the Emergency Department with ICH and gives clinicians an early, easily obtained prognostic indicator for mortality and outcome in these patients.

Other considerations:
Further research can be done to see if control of hyperglycemia may lead to better outcomes among ICH patients. This study is limited in its design- it only considered outcome at the end of the hospital stay, but did not control for the length of stay. More research should be done to determine if there is a difference in outcome at  specific time points over a greater length of time (eg. 3, 6, and 12 months).

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