Spontaneous intracerebral haemorrhage has long carried an air of clinical resignation, the diagnosis that quietly lowered everyone’s expectations before treatment had even begun. INTERACT3, published in The Lancet in May 2023, unsettled that fatalism. It changed not a drug but a way of thinking, and it has since become impossible to discuss acute haemorrhagic stroke without reference to it.

The Trial in Brief

INTERACT3 was a pragmatic, international stepped-wedge cluster-randomised trial enrolling 7,036 patients across 121 hospitals, most of them in low- and middle-income countries. Instead of testing a single molecule, it asked whether a coordinated care bundle, begun within hours of the bleed, could alter the course of the illness. The bundle drew together four physiologically targeted actions: intensive systolic blood pressure lowering to a target below 140 mmHg; strict glucose control (6.1–7.8 mmol/L in patients without diabetes, 7.8–10.0 mmol/L in those with it); fever control holding temperature at or below 37.5°C; and rapid reversal of anticoagulation to an INR below 1.5.

What the Numbers Showed

The primary outcome was functional recovery, measured by a modified Rankin Scale shift analysis at six months. The bundle came out ahead, with a common odds ratio of 0.86 (95% CI 0.76–0.97; p=0.015). The advantage extended beyond function. Mortality fell from 17.0% to 14.1%, and serious adverse events dropped from 20.1% to 16.0%. In a disease so often treated with a shrug, these are shifts of real consequence.

The Story of Secondary Injury

The physiology explains why. Outcome after an intracerebral haemorrhage is shaped less by the original bleed than by the secondary injury that follows, and each element of the bundle disarms a different, time-sensitive part of that cascade.

The first threat is early haematoma expansion, which occurs in roughly a third of patients within the opening hours and responds to blood pressure. That is the rationale for rapid, controlled lowering of systolic pressure. The trial’s smooth, protocol-guided titration also mattered: it likely spared patients the falls in renal and cerebral perfusion that may have blunted the effect in earlier blood-pressure trials such as ATACH-2.

Alongside pressure sit hyperglycaemia and fever, each an independent driver of perihaematomal oedema, oxidative stress, and a faltering penumbral metabolism. Anticoagulation-associated bleeds carry the highest expansion risk of all, which places rapid reversal among the most valuable components of the bundle.

The deeper lesson runs beneath the individual parts. None of these interventions had previously shown a convincing functional benefit on its own. Delivered together, early and in concert, they moved patients measurably towards independence. The whole outperformed the sum of its parts.

From Nihilism to a Protocol Worth Running

This reframes the disease. Intracerebral haemorrhage moves from a condition met with therapeutic nihilism to an actionable, protocol-driven emergency, one that sits naturally beside the bundled approaches already familiar from sepsis and STEMI care. For the neuroanaesthesiologist and neurointensivist, the implication is concrete: systems-level implementation — standing order sets, rapid-reversal pathways, and pre-specified physiological targets switched on in the emergency department and carried through into the operating room — achieves what isolated pharmacological effort has not.

Reading the Evidence Honestly

Two caveats temper the enthusiasm. The stepped-wedge design is vulnerable to temporal confounding and cannot, by its structure, isolate which single element carried the benefit, which means the bundle should be adopted as a complete package rather than dismantled into favoured parts. And because most patients were recruited in lower-resource settings, questions of external validity and generalisability deserve open acknowledgement rather than quiet assumption.

These limits notwithstanding, INTERACT3 is well positioned to shape forthcoming AHA/ASA and European Stroke Organisation guidance. It establishes early, multimodal physiological control as the emerging standard of care in acute intracerebral haemorrhage.

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Sources: INTERACT3, The Lancet (2023) · INTERACT3 full text, PMC