Subarachnoid Haemorrhage Dr Mark Putland MBBS FACEM Co-DEMT

Basics What is the subarachnoid space?

Basics Epidemiology 3% of strokes 5% of stroke deaths 25% of life years lost to stroke Peak age 40-60 years Smokers, hypertensives, family history, connective tissue problems (PCKD, NF, Sickle Cell, α-1 antitrypsin deficiency)

Basics Aetiology Most are traumatic Of the non-traumatic Aneurysm account for most AVM is the most common in kids and young adults Mycotic aneurysm Dissection Hypertensive crisis Sickle cell Tumour Bleeding tendency

Pathology Site Majority in anterior circulation at arterial branch points Circle of Willis Trifurcation of MCA Basilar tip (posterior circulation)

Exercise or sex induced History Thunderclap headache Exercise or sex induced Nausea, vomiting and syncope are common Meningeal irritation develops over time Seizures in 15% Prodrome from expanding aneurysm may cause CN palsy, seizure, TIA, mass effect rarely

History Drugs Premorbid state Social context

Examination Red flags for SAH Meningism HT Depressed or CLOUDED conscious state Focal neurology

Examination Once SAH diagnosed GCS Focal neurology BP Complications APO Arrhythmia

Grading Grade Survival Hunt and Hess WFNS GCS Motor 1 15 No 70% 2 Asymptomatic, slight headache, slight nuchal rigidity 15 No 70% 2 Mod-sev h/a, CN palsy or no defect 13-14 60% 3 Drowsy, confused, mild focal deficit Yes 50% 4 Stupor, mod-sev hemi, vegetative posturing 7-12 Y/N 40% 5 Deep coma, decerebrate, moribund 3-6 10%

Diagnosis CT Can we just get a better scanner? CT grading system 90-95% sensitive in first 24 hours 80% sensitive at 3 days 50% sensitive at 1 week Can we just get a better scanner? CT grading system

Diagnosis Why is the sensitivity still 93%

Diagnosis What does a sensitivity of 93% mean for my patient? What does a sensitivity of 93% mean for my practice?

Stats Sensitivity Specificity A/(A+C) How good is the test at finding the disease Specificity D/(B+D) How good the test is at ruling out the disease Disease Yes No Test Result + A B - C D

Stats Positive Predictive Value Negative predictive value A/(A+B) How meaningful a positive test is in this population Negative predictive value D/(C+D) How meaningful a negative test is for this population Disease Yes No Test Result + A B - C D

HELP!!!!!! How many people with a thunderclap headache have SAH? 8% This is the background prevalence rate Disease Yes No Test Result + A B - C D

HELP!!!!!! The patient starts out with an 8% chance of SAH NPV You have a negative scan This means you have x chance of not having a bleed 920/(920+5)= 99.5% Disease Yes No Test Result + 75 - 5 920

HELP!!!!!! So when the patient doesn’t want an LP what is the chance they have a bleed? 1/200 Disease Yes No Test Result + 75 - 5 920

HELP!!!!!! What does this mean in your practice? I probably see about 2 of these headaches a week 10 years in EM means 1000 such headaches This gives me 80 cases of SAH in 10 years Disease Yes No Test Result + A B - C D

HELP!!!!!! Sensitivity of 93% means out of 1000 thunderclap headaches we capture 75 SAH cases and miss 5. That’s 5 big lawsuits in 10 years Disease Yes No Test Result + 75 - 5 920

HELP!!!!!! So the individual patient cares about negative predictive value The doctor cares about sensitivity Disease Yes No Test Result + 75 - 5 920

So what next with a negative CT? LP RBC Traumatic tap rate ~20% Decreasing cell counts are unreliable so have a wide margin of error Xanthochromia Usually appears within 6 hours, definitely within 12 Longer delay means more rebleeds Generally aim for 6-12 hours

So what next with a negative CT? MRI Good for delayed presentations (up to 2 weeks) Must specify the indication to get the right protocol CT angiogram Finds all but the smallest aneurysms What’s the catch?

CT angio- what’s the catch? It’s a big one! 2% of the normal population have an aneurysm A tiny fraction of these will ever bleed. CT angiogram creates a disease in people who don’t have one.

CT within 6 hours? 3000 patients 11 ED’s Canada (similar to here) http://www.bmj.com/content/343/bmj.d4277.abstract 3000 patients 11 ED’s Canada (similar to here) 7-8% rate of bleed overall 93% sensitivity overall 121 out of 953 bleeds in patients scanned within 6 hours

Management Protect the injured brain Get to a neurosurgeon before CO2 , O2 , Temp, BSL, head up, seizure prevention Get to a neurosurgeon before Rebleed Vasospasm Hydrocephalus Cerebral salt wasting disease, SIADH

Management Neurosurgical hospitals ARV St V, Monash, RMH, Alfred, Austin ARV Defined transfer process. 1300 36 86 61