Hypothermia

Today in morning report we discussed the case of a patient who presented with hypothermia. We don't come across this every day in GIM so it is good to review the causes. Hypothermia is defined as a temperature less than 35 degrees Celsius. It is important to consider getting a second reading from a different body site to confirm that this is a true reading.

Environmental exposure is a common cause of hypothermia which can usually be elicited from the history. However, sometimes there is no history of cold exposure. In these cases you should think about the other causes of hypothermia. You can divide these into broad categories [that relate to the reasons your house might be too cold]:

Increased heat loss [the doors/windows are open]

• Drugs that cause vasodilatation (drugs, alcohol)
• Iatrogenic causes (cold infusions, CRRT, bypass)
• Burns or severe skin conditions (psoriasis)

Reduced heat production [the furnace is not working properly]

• Endocrine causes (hypothyroidism, adrenal insufficiency, hypopituitarism)
• Hypoglycemia
• Malnutrition
• Reduced muscle activity (extreme elderly, inactivity)

Impaired regulation [the thermostat is incorrectly set]

• Central CNS pathology (Stroke, intracranial hemorrhage, hypothalamic dysfunction, parkinsonism, MS, CNS drugs
• Peripheral CNS pathology (spinal cord transection)

Miscellaneous causes [your house has an infection? ok, this one doesn’t apply to the house analogy]

• Sepsis
• Pancreatitis

Check out the following article for a nice review of hypothermia: http://www.aafp.org/afp/2004/1215/p2325.html  

Evaluating a patient with headache

We discussed an interesting case of a young man presenting with a headache. This is such a common complaint that it is worth having a solid organized approach. Here are a few key points we discussed in morning report.

Think of the common and serious causes when evaluating a patient with a headache

Headache is a common, non-specific complaint that can be benign or life-threatening. For this reason it is important to have a good approach to headache. One approach is to come up with a differential for the causes that you don’t want to miss and also a list of the most common causes. You can use these lists to direct your history, physical exam and investigations.

Always consider epidemiology when creating your differential. For example, patients who are immunocompromised or those with previous intracranial pathology/surgery may invoke other diagnoses. Here is the differential diagnosis that we came up with at morning report (and one which I generally start with). Keep in mind that there are many other causes of headache that you may have to consider based on the specific clinical situation.

Common causes: Migraine, Tension-type, Cluster, Medication withdrawal, Headache associated with volume depletion or other systemic illness.

Serious causes: Meningitis, Subarachnoid hemorrhage, Temporal arteritis, CNS lesion, Sinus venous thrombosis, artery dissection, hypertensive emergency.

Use a history and neurological exam to rule in (or out) ‘serious’ causes of headache and guide your subsequent workup

The ‘POUNDing’ criteria was described in JAMA as a method of deciding whether a patient with a headache has a migraine or should undergo neuroimaging (JAMA Article Link). The 5 criteria are: Pulsatile, lasts 4-72 hOurs, Unilateral, Nausea/Vomiting and disabling. If a patient has 4/5 of the POUNDing criteria, the positive likelihood ratio for this being a migraine is 24.

It is also important to ask about red flags associated with the ‘serious causes’ listed above. Your history and physical exam will then direct your investigations. For example, you may order neuroimaging (ie. suspecting subarachnoid hemorrhage or CNS lesion), get a lumbar puncture and give antibiotics (ie. suspecting bacterial meningitis), start steroids (ie. suspecting GCA), and so on.

Bacterial meningitis should always be on your differential for headache

Check out this phenomenal one page CMAJ article on bacterial meningitis that gives a really great overview of 5 things you should know about bacterial meningitis (CMAJ Link). If there is one teaching point that I can highlight it is the following: Do not delay antibiotics (and steroids) in patients who you suspect have bacterial meningitis. This means that if you need neuroimaging or think that the LP will be delayed – give the antibiotics right away. Antibiotics might lower your chances of obtaining a positive diagnostic CSF culture but early antibiotics will improve the outcome for your patient.  Plus, you can still use other CSF indicators, like the WBC count/differential, to help support your diagnosis of bacterial meningitis.

If you are unsure about whether the patient has aseptic meningitis or bacterial meningitis you should consider treating empirically with antibiotics

The patient we discussed in morning report had aseptic meningitis. There is a long list of viral causes of aseptic meningitis.  The major families of viruses to think about include herpesviruses (ie. HSV-II), arboviruses (ie. West Nile virus), enteroviruses (ie. coxsackie) and don’t forget about HIV. Other causes to consider in the appropriate patient includes tuberculous meningitis or fungal meningitis. Choose specific CSF testing based on the clinical picture. 

If the diagnosis is not clear and there is still a suspicion for bacterial meningitis, it is often safest to treat empirically with antibiotics and await culture results.  If you suspect HSV as the cause of aseptic meningitis (ie. oral or genital lesions present) consider treating empirically with acyclovir. 

References:

Detsky, Michael E., et al. "Does this patient with headache have a migraine or need neuroimaging?." Jama 296.10 (2006): 1274-1283.

Moayedi, Yasbanoo, and Wayne L. Gold. "Acute bacterial meningitis in adults." Canadian Medical Association Journal 184.9 (2012): 1060-1060.