Can a subarachnoid hemorrhage (SAH) cause fever and if so, for how long?

Fever After Subarachnoid Hemorrhage

Yes, subarachnoid hemorrhage commonly causes fever, which can persist for up to 2 weeks after the initial hemorrhage, and this fever is independently associated with worse cognitive outcomes and increased mortality. 1

Incidence and Timing of Fever

• Fever occurs in approximately 41-48% of patients with SAH and is one of the most common complications 2, 3, 4
• Early fever can develop within 24 hours (occurring in 11.9% of patients) or within 72 hours (18.9% of patients) 3
• Fever typically persists for a mean duration of 2.1 ± 3.0 days, though it can recur throughout the first 2 weeks after hemorrhage 3
• The period of risk extends through Day 13 post-hemorrhage, which represents the critical monitoring window 5

Mechanism and Clinical Significance

• Fever of non-infectious origin (central fever) is associated with severity of injury, amount of hemorrhage, and development of vasospasm, representing a systemic inflammatory response triggered by blood and its byproducts 1
• Approximately 50% of SAH patients develop a systemic inflammatory response syndrome, mediated in part by interleukin-1 1
• Fever that persists for >24 hours at temperatures >37.5°C is found in 83% of patients with poor outcomes and correlates with ventricular extension of the hemorrhage 1

Predictors of Fever Development

• Poor Hunt-Hess grade (OR 5.37) is the strongest independent predictor of fever 4
• Presence of intraventricular hemorrhage (OR 5.18) significantly increases fever risk 4
• Older age (OR 1.06 per year) independently predicts fever occurrence 4
• Anterior communicating artery aneurysms, larger SAH sum scores, and higher body mass index are additional risk factors 2

Impact on Outcomes

• Fever is independently associated with worse cognitive outcomes in SAH survivors 1
• Each additional day of fever increases the odds of poor outcome by 14% (OR 1.14 per day of fever) 3
• Fever is an independent risk factor for delayed cerebral ischemia 2
• In-hospital mortality is significantly increased with fever (OR 17.36) 4
• Cumulative fever burden (the sum of temperatures above 100.4°F across all days) correlates with worse functional outcomes, particularly in good-grade patients 5

Infectious vs. Non-Infectious Fever

• An infectious source is identified in only 44.8% of febrile SAH patients, meaning the majority of fever is central (non-infectious) in origin 3
• Bacteremia and ventriculitis are uncommon (≤5%) and are not associated with higher fever burden 5
• Despite the high prevalence of non-infectious fever, all febrile patients require investigation for infectious causes including pneumonia, urinary tract infection, and line infections 6

Management Implications

• Aggressive fever control targeting normothermia (36.5°C ± 0.2°C) is reasonable in the acute phase of SAH (Class IIa; Level of Evidence B) 1
• Acetaminophen should be used as first-line antipyretic therapy, administered regularly rather than sporadically when fevers recur 6
• Improved functional outcomes with effective fever control have been reported 1
• Prolonged fever should be avoided, as days of fever (not just fever severity) is the strongest predictor of poor outcome 3

Critical Pitfall

• Subfebrile temperatures (37-38.2°C) do not influence clinical outcomes and may not justify aggressive intervention, whereas temperatures ≥38.3°C on ≥2 consecutive days are associated with poor outcomes 3