EBQ:Differentiation between traumatic tap and aneurysmal subarachnoid hemorrhage

Under Review Journal Club Article

Perry, J et al.. "Differentiation between traumatic tap and aneurysmal subarachnoid hemorrhage: prospective cohort study". BMJ. 2015. 18(350):epub.
PubMed Full text PDF

Clinical Question

• Can cerebrospinal fluid from patients with acute headache after traumatic lumbar puncture be distinguished from subarachnoid hemorrhage?

Conclusion

• No xanthochromia and red blood cell count < 2000 × 10⁶/L can reasonably excludes the diagnosis of aneurysmal subarachnoid hemorrhage.

Major Points

• In ruling out traumatic subarachnoid hemorrhage, the traumatic tap which causes blood to mix with cerebrospinal fluid can complicate the diagnosis of subarachnoid hemorrhage in up to 30% of LPs.

Study Design

• Planned substudy from the prospective multi center cohort study, designed to derive and validate the Ottawa SAH (subarachnoid hemorrhage) rule
• Conducted between November 2000 - December 2009
• Multicenter at 12 canadian academic EDs

Population

N=1739

Patient Demographics

• Mean Age: 43yo
• Sex: 40% Men/60% Women

Inclusion Criteria

• Age >15
• Alert patients (GCS =15)
• ED patents with acute non-traumatic headache undergoing LP to rule out subarachnoid hemorrhage
• Within 14 days of headache onset

Exclusion Criteria

• Recurrent headaches (3 or more with similar character/intensity over 6 month or greater period
• Transfered from other hospital with confirmed subarachnoid
• Presence of focal neurologic deficits or papilledema
• History of
  • Subarachnoid hemorrhage
  • Aneurysm
  • VP shunt
  • Brain neoplasm

Interventions

• Computed tomography and/or lumbar puncture was performed at the discretion of the treating physician
  • Some LPs were performed before CT scans

• Patients discharged without having both computed tomography imaging and a normal result on lumbar puncture were assessed by telephone interview one month and six months after assessment in the emergency department as well as a review of medical records to identify any recorded subarachnoid hemorrhage.

• Patients without telephone follow-up or subsequent hospital encounters at the enrolling sites were further checked against the coroner’s records to identify any deaths compatible with subarachnoid hemorrhage

Outcomes

Subarachnoid hemorrhage definition:

• Blood in the subarachnoid space on CT brain
• Xanthochromia on examination of CSF
• Red blood cells in the final tube of CSF fluid and aneurysm shown with cerebral angiography requiring any neurovascular intervention or resulting in death.

Normal LP = 1098 Abnormal LP = 641 (36.9%)

• • No aneurysmal subarachnoid = 626
  • Aneurysmal subarachnoid 15
  • Xanthochromia = 7
  • No Xanthochromia = 8

Primary Outcome

There were 15 (0.9%) patients with aneurysmal subarachnoid hemorrhage based on abnormal results of a lumbar puncture.

Secondary Outcomes

The presence of less than 2000 × 10⁶/L red blood cells in addition to no xanthochromia excluded the diagnosis of aneurysmal subarachnoid hemorrhage

• Sensitivity of 100% (95% confidence interval 74.7% to 100%)
• Specificity of 91.2% (88.6% to 93.3%).

Subgroup analysis

Characteristics or patients in Canadian SAH Rule Study

All patients in the SAH Rule derivation and validation cohort

• Neck Pain or stiffness: 33.7%
• Median time of headache onset to peak: 60 seconds
• CT performed: 81.7%
• Mean time from headache onset to LP: 18 hours
• Median RBC count in last tube: 0
• Aneurysmal subarachnoid hemorrhage: 3.5%

Characteristics of patients with abnormal LP

Positive xanthochromia

• Aneurysmal subarachnoid hemorrhage: 46.6%
• No Subarachnoid: 2.6%

Median RBC count in last tube (x10⁶)

• • Aneurysmal subarachnoid: 28741
  • No subarachnoid: 20

Angiography rate

• Aneurysmal subarachnoid hemorrhage: 15%
• No subarachnoid: 64.5%