Virtual Journal Club April 2014: Sensitivity of computed tomography performed within six hours of onset of headache for diagnosis of subarachnoid haemorrhage: prospective cohort study

The standard practice for ruling out SAH has been CT followed by LP.   Some practitioners continue to aggressively perform Lumbar Puncture to rule out SAH while others avoid LP at all cost.  Some explain to the patient that "I AM GOING TO HAVE TO PUT A VERY LONG NEEDLE IN YOUR BACK" (gesturing with hands approximately shoulder width apart)  and allow the patient to decline, "after discussing risks and benefits."  Still others call upon the radiologist to perform the LP under "fluoroscopic guidance", hooray for radiologists!!!

Whichever style you employ, This robust study of over 3000 headache patients explores the utility of performing an LP within 6 hours of a negative head CT.

Link: BMJ 2011;343:d4277

Some popular thinkers in Emergency Medicine argue this question better than I ever could:

DEFER LP: Dr Newman questions the utility of performing an LP following a negative Head CT within 6 hours of headache onset: http://www.epmonthly.com/features/current-features/lp-for-subarachnoid-hemorrhage-the-700-club/

PERFORM LP: Dr Klauer agues that providers should continue performing LP to rule out Subarachnoid: http://www.epmonthly.com/departments/columns/in-my-opinion/a-proud-member-of-the-700-club/

A more recent prospective study using the 6 hour rule incorporated into a decision tool suggests that eliminating LP under 6 hours might be a bit hasty:

http://www.jwatch.org/em201302150000001/2013/02/15/sorry-cant-stop-doing-lumbar-puncture-rule-out

Ultimately, you and your patient will decide!!!

Good luck.

To access the full article and get Continuing Education Credit, please sign up for the virtual journal club invite or access directly through the ALLINA knowledge network (Allina ID and Password required).




Questions:

1. Headache is a common symptom and accounts for about 2% of presenting complaints in the Emergency Department.  A spontaneous subarachnoid hemorrhage, which is a neurosurgical emergency, is identified in about ___% of patients with Headache. 

a.     1%

b.     2%

c.      10%

d.     20%

(Nearly half of all patients with subarachnoid hemorrhage have normal neurological examination and normal vital signs at initial presentation). 

2. True or False: The overall mortality of subarachnoid hemorrhage is high with 25-50% of patients dying within 6 months.

3. True or False:  Although there is no standard definition for subarachnoid hemorrhage, these authors formulated an expert consensus definition: Positive blood on CT, Visual xanthochromia, or red blood cells in the final tube of CSF with abnormal intracranial pressure.

 

4. Most studies that evaluated the sensitivity of computed tomography for subarachnoid hemorrhage were retrospective reviews and found that sensitivity deteriorates rapidly over time because erythrocyte __________ and __________.

a.     dissipation and lysis

b.     deception and lying

c.      decrepit and lynching

d.     dissociation and lyricism

5. True or False: In the group of 953 patients that received CT imaging within 6 hours of headache onset; all 121 patients with subarachnoid hemorrhage were identified by CT scan (yielding a sensitivity of 100%, specificity of 100%, negative predictive value of 100%, and a positive predictive value of 100%.)