Acute Stroke

Acute stroke is the sudden loss of brain function caused by interruption of the blood supply to part of the brain, either by occlusion of an artery (ischaemic stroke) or by rupture and bleeding (haemorrhagic stroke). It is a time-critical neurological emergency and a major cause of death and long-term disability, making rapid recognition central to emergency and critical care nursing.

Definition

Stroke is an acute episode of focal neurological dysfunction caused by infarction or haemorrhage in the brain, spinal cord, or retina; the great majority of strokes are ischaemic, due to arterial occlusion that deprives a region of brain of blood flow, while a minority are haemorrhagic, due to rupture of a blood vessel.

Scope

This entry covers the definition and main types of acute stroke, the pathophysiology of cerebral ischaemia and the ischaemic penumbra, the concept of time-dependent salvageable brain tissue, and the epidemiologic burden. It is a conceptual reference and does not provide thrombolysis or thrombectomy eligibility criteria, drug dosing, or individualized treatment instructions.

Core questions

• What distinguishes ischaemic from haemorrhagic stroke?
• What is the ischaemic penumbra and why does it matter?
• Why is acute stroke described as a time-critical emergency?
• What burden of death and disability does stroke impose globally?

Key concepts

• Ischaemic versus haemorrhagic stroke
• Cerebral ischaemia and infarction
• Ischaemic penumbra (salvageable tissue)
• Time-dependent neuronal loss ('time is brain')
• Reperfusion concepts (thrombolysis and thrombectomy)
• Stroke as a leading cause of disability

Mechanisms

In ischaemic stroke an artery supplying the brain is occluded, usually by thrombosis or embolism, abruptly cutting off oxygen and glucose to the dependent territory. The core of the territory infarcts quickly, but a surrounding zone — the ischaemic penumbra — is hypoperfused yet still viable for a limited time, and it is the target of reperfusion strategies (Berkhemer, 2015; Nogueira, 2018). In haemorrhagic stroke a vessel ruptures, and bleeding both deprives downstream tissue of flow and exerts mechanical and toxic injury on surrounding brain. Because neurons die progressively once flow is lost, the syndrome is fundamentally time-dependent, which underlies the principle that earlier restoration of perfusion preserves more brain (Powers, 2019).

Clinical relevance

Acute stroke is a core reference syndrome for emergency and critical care nursing, framing why neurological deficits of sudden onset are treated as emergencies and why recognition speed matters. This entry explains how stroke is defined, classified, and studied and the physiology of the penumbra; it is descriptive and does not direct individual eligibility for thrombolysis or thrombectomy, drug therapy, or other treatment, which follow current stroke guidelines and institutional protocols.

Epidemiology

Stroke is among the leading global causes of death and the foremost causes of acquired adult disability, with a substantial estimated lifetime risk that varies by region and is rising in many populations (GBD 2016 Lifetime Risk of Stroke Collaborators, 2018). Ischaemic stroke accounts for the large majority of cases, with haemorrhagic stroke a smaller but more lethal share.

History

Stroke was historically described as 'apoplexy' and understood only in broad terms until the vascular basis of cerebral infarction and haemorrhage was clarified. The advent of brain imaging allowed reliable distinction of ischaemic from haemorrhagic stroke, and the demonstration that intravenous thrombolysis and, later, endovascular thrombectomy could rescue the ischaemic penumbra transformed acute care (Berkhemer, 2015; Nogueira, 2018). Successive guidelines have consolidated this evidence into time-based frameworks for early management (Powers, 2019).

Debates

How far can the treatment time window be extended?

Trials using imaging to identify salvageable penumbra have extended reperfusion eligibility well beyond the classic early window for selected patients, reframing the relationship between elapsed time and treatment benefit.

Seminal works

• powers-2019
• berkhemer-2015
• nogueira-2018

Frequently asked questions

What is the difference between an ischaemic and a haemorrhagic stroke?

An ischaemic stroke is caused by a blocked artery cutting off blood flow to part of the brain, while a haemorrhagic stroke is caused by a ruptured vessel bleeding into or around the brain; most strokes are ischaemic, but haemorrhagic strokes tend to be more lethal.

Why is stroke called a time-critical emergency?

Brain tissue deprived of blood flow dies progressively, and a surrounding zone of at-risk but still-viable tissue (the penumbra) can be salvaged only for a limited period, so earlier restoration of blood flow preserves more brain function.