Stroke at Sea — Recognition, Time Windows and Evacuation Decisions

In a stroke unit, the phrase "time is brain" drives every protocol. From the moment a patient crosses the threshold, the clock governs triage, imaging, and the decision to administer thrombolysis or proceed to thrombectomy. The system is built around minimising door-to-needle time, because every minute of cerebral ischaemia destroys approximately 1.9 million neurons. The entire architecture of acute stroke care is an exercise in compressing time.

At sea, time is also brain — but time is also distance. The patient who develops sudden-onset facial droop and arm weakness in the dining room of a cruise ship at 2200 hours is not twenty minutes from a stroke unit. They may be twelve hours from the nearest port with a CT scanner. They may be six hours from a helicopter rendezvous point. They may be in the middle of the North Atlantic where no helicopter can reach them at all. The thrombolysis window does not expand because the ocean is wide. It closes at the same rate it always does, and every nautical mile between the ship and the nearest stroke centre is a mile measured in dying neurons.

This article addresses the clinical and operational reality of managing stroke at sea: how to recognise it quickly, how to calculate backwards from treatment windows, how to manage the patient without imaging, when to trigger evacuation, and how to communicate the urgency to the bridge in a way that produces action.

Recognition: The FAST Assessment and Beyond

The FAST mnemonic — Face, Arms, Speech, Time — remains the cornerstone of stroke recognition, and it works just as well in a ship's medical centre as it does in an emergency department. Facial asymmetry, unilateral arm drift, slurred or absent speech, and the precise time of symptom onset are the four data points that launch the entire stroke response. At sea, however, the recognition challenge is compounded by several factors that do not exist ashore.

First, the patient may not present to you promptly. On a cruise ship, passengers who develop symptoms in their cabin at night may not seek help until morning, by which time the thrombolysis window has already closed. Crew members working in the engine room may attribute their sudden clumsiness to fatigue or heat. The delay between symptom onset and presentation is often longer at sea than ashore, and that delay is clinically devastating.

Second, the initial call may come from someone with no medical training. A cabin steward, a dining room manager, a fellow passenger. The information you receive may be vague: "a guest has collapsed," "someone is acting confused," "a crew member cannot move his arm." You need to be at the patient's side rapidly, and you need to perform FAST the moment you arrive, because the clock that matters most — the time of symptom onset — is already running.

Your initial assessment should be structured and rapid:

• Face: Ask the patient to smile. Look for asymmetry. Has one side of the face dropped? Can they raise both eyebrows equally?
• Arms: Ask the patient to raise both arms and hold them at 90 degrees (if sitting) or 45 degrees (if supine) for ten seconds. Does one arm drift downward? Is there complete paralysis on one side?
• Speech: Ask the patient to repeat a simple sentence. Is the speech slurred? Are they using the wrong words? Can they understand your instructions? Is there complete absence of speech?
• Time: Establish the exact time of symptom onset. If the patient woke with symptoms, the onset time is when they were last known to be normal — not when they woke up. This distinction is critical for treatment eligibility.

Beyond FAST, perform a rapid screen for stroke severity. Can the patient move their legs? Do they have visual field deficits? Can they feel touch on both sides? Is there gaze deviation? The National Institutes of Health Stroke Scale (NIHSS) provides a structured framework for this, and even an abbreviated version performed at sea gives the receiving facility valuable information about stroke severity when you hand the patient over.

Differentiating Stroke from Mimics

At sea, you do not have a CT scanner. You cannot distinguish ischaemic stroke from haemorrhagic stroke. You cannot confirm the diagnosis at all. What you can do is differentiate stroke from the conditions that mimic it, several of which are eminently treatable without imaging.

• Hypoglycaemia. This is the most important stroke mimic to exclude, because it is rapidly reversible and because failing to check for it is indefensible. Every patient with acute neurological deficit gets a capillary blood glucose measurement within the first two minutes of your assessment. Hypoglycaemia can produce focal neurological signs that are indistinguishable from stroke: hemiparesis, aphasia, confusion, even gaze deviation. If the glucose is below 3.5 mmol/L (63 mg/dL), correct it immediately and reassess. Many "strokes" at sea turn out to be hypoglycaemia in diabetic patients who missed a meal or over-administered insulin.
• Seizure with post-ictal deficit (Todd's paresis). A patient who has had a witnessed or unwitnessed seizure may present with unilateral weakness that resolves over minutes to hours. Ask about a history of epilepsy, look for tongue biting, check for urinary incontinence, and note whether the deficit is improving. Todd's paresis typically resolves within 24 hours, often much sooner.
• Hemiplegic migraine. Patients with a history of migraine with aura may develop unilateral motor or sensory symptoms that closely mimic stroke. The key differentiator is the temporal pattern: migraine aura typically develops gradually over 20 to 30 minutes and is accompanied by headache, whereas stroke deficits are maximal at onset. However, this distinction is not always reliable, and any patient with acute focal deficit should be treated as a potential stroke until proven otherwise.
• Vestibular disorders. Vertigo, nausea, and ataxia can mimic posterior circulation stroke. The HINTS examination (Head Impulse, Nystagmus, Test of Skew) is the single most useful bedside tool for distinguishing peripheral from central vertigo. A normal head impulse test with direction-changing nystagmus or skew deviation suggests a central cause and should raise suspicion for posterior circulation stroke.
• Hypertensive encephalopathy. Severely elevated blood pressure can produce confusion, visual disturbance, and seizures that may be mistaken for stroke. Check the blood pressure. If it is profoundly elevated (systolic above 220 mmHg or diastolic above 120 mmHg) with signs of end-organ damage, the management changes significantly.

Time Windows: Calculating Backwards from the Nearest Facility

The two treatment windows that drive acute stroke management ashore are the thrombolysis window and the thrombectomy window. Understanding these windows — and calculating backwards from them — is what transforms a clinical event into an operational decision at sea.

Thrombolysis (IV alteplase or tenecteplase) can be administered up to 4.5 hours from symptom onset. This is the narrower window, and it is the one most likely to close before a maritime patient can reach definitive care. If your patient developed symptoms at 2200 and the nearest port with a stroke unit is 8 hours away, the thrombolysis window will close at 0230 — six hours before the ship docks. No amount of clinical excellence at sea can reopen that window.

Mechanical thrombectomy for large vessel occlusion can be performed up to 24 hours from symptom onset in selected patients, based on advanced imaging criteria. This wider window is the reason that even "late" stroke presentations at sea still warrant urgent evacuation. A patient who is 10 hours into a large vessel occlusion may still be a thrombectomy candidate if they can reach a comprehensive stroke centre within the remaining 14 hours.

The critical operational calculation is this: subtract the current elapsed time since symptom onset from the treatment window, and compare the remainder to the estimated transit time to definitive care. If the transit time exceeds the remaining window, the treatment is not available via ship transit. Helicopter evacuation or diversion must be considered.

At sea, the stroke clock runs backwards. You do not count forward from onset — you count backward from the window closing, and you compare that number to the miles between your patient and the nearest CT scanner.

This calculation must be performed immediately upon recognition and communicated to the bridge without delay. It must also be repeated if symptoms change, if the ship's speed changes, or if new information about facility availability becomes available.

Assessment at Sea: Working Without a CT Scanner

The absence of imaging is the defining constraint of stroke management at sea. You cannot distinguish ischaemic from haemorrhagic stroke. You cannot identify large vessel occlusion. You cannot guide thrombolysis. This limitation does not, however, mean that your assessment is without value. What you can do at sea forms the foundation of the handover to the receiving facility and directly influences evacuation priority.

Your assessment should include:

• Blood pressure. Measure on arrival and at 15-minute intervals during the acute phase. Record every reading with a timestamp. Blood pressure management in stroke differs fundamentally depending on whether the stroke is ischaemic or haemorrhagic, and since you cannot distinguish the two, your approach must be conservative.
• Blood glucose. As discussed above, check immediately. Recheck at 30-minute intervals. Both hypoglycaemia and hyperglycaemia are associated with worse outcomes in stroke, and glucose is one of the few variables you can actively manage at sea.
• Oxygen saturation. Maintain SpO2 above 94%. Do not administer supplemental oxygen to patients who are not hypoxic, as hyperoxia has not been shown to benefit stroke patients and may theoretically worsen reperfusion injury.
• Temperature. Fever worsens neurological outcomes in stroke. If the patient is febrile, administer paracetamol (acetaminophen) 1g. Target normothermia.
• Heart rhythm. If you have a cardiac monitor or 12-lead ECG, record the rhythm. Atrial fibrillation is the most common cardiac cause of embolic stroke, and identifying it at sea helps the receiving facility with both diagnosis and long-term management.
• Neurological status. Perform serial assessments using a structured tool. At minimum, record the level of consciousness (using AVPU or GCS), pupil size and reactivity, presence and severity of limb weakness, speech quality, and any visual field deficits. Repeat this assessment every 30 minutes and document each examination with a timestamp.

The purpose of this serial assessment is twofold. It identifies deterioration that may change the evacuation priority, and it provides the receiving stroke team with a timeline of the patient's neurological trajectory — information that influences their treatment decisions.

Management: What You Can Do at Sea

You cannot give thrombolysis at sea. You cannot perform thrombectomy. You cannot obtain the imaging that would guide either intervention. But the care you provide between symptom onset and arrival at definitive care has a measurable impact on outcome. Neuroprotective management at sea focuses on preventing secondary brain injury.

Positioning. Keep the patient supine with the head of the bed elevated to 30 degrees. This optimises cerebral venous drainage while maintaining adequate cerebral perfusion pressure. If the patient is vomiting or has a reduced level of consciousness, place them in the recovery position to protect the airway, prioritising airway over perfusion.

Blood pressure management. This is where the absence of imaging creates a genuine clinical dilemma. In ischaemic stroke, permissive hypertension is generally accepted: do not lower blood pressure unless it exceeds 220/120 mmHg (or 185/110 mmHg if the patient is a thrombolysis candidate). In haemorrhagic stroke, aggressive blood pressure reduction to a target systolic below 140 mmHg improves outcomes. Since you cannot distinguish the two at sea, the conservative approach is to tolerate hypertension up to 220/120 mmHg and only intervene if blood pressure exceeds this threshold or if there are signs of hypertensive emergency (acute pulmonary oedema, aortic dissection, encephalopathy). If you must lower blood pressure, use a titratable agent if available. Labetalol 10–20 mg IV is a reasonable first-line choice. Avoid precipitous drops.

Glucose management. Target blood glucose between 7.8 and 10 mmol/L (140–180 mg/dL). Treat hypoglycaemia aggressively with IV dextrose. Manage hyperglycaemia with insulin if glucose exceeds 10 mmol/L, but avoid tight glucose control that risks hypoglycaemia. Hypoglycaemia is more immediately dangerous than moderate hyperglycaemia.

Aspiration prevention. Stroke patients frequently have dysphagia, and aspiration pneumonia is a leading cause of death after stroke. Keep the patient nil by mouth until swallowing has been formally assessed. If the patient has a reduced level of consciousness, ensure the airway is protected. Suction should be available at the bedside.

Do not give antiplatelet agents. Aspirin is indicated in ischaemic stroke but contraindicated in haemorrhagic stroke. Without imaging, you cannot safely give aspirin, clopidogrel, or any antiplatelet agent. Document this decision and the reasoning. The receiving facility will initiate antiplatelet therapy after imaging confirms the stroke type.

The Medevac Decision: When Stroke Triggers Immediate Evacuation

Not every stroke at sea requires helicopter evacuation. A patient who presents 18 hours after symptom onset with a mild deficit and the ship arriving in port in 6 hours may be appropriately managed with urgent disembarkation. But many stroke presentations at sea demand immediate medevac consideration, and the decision framework centres on the treatment window calculation.

Stroke should trigger immediate medevac evaluation when:

• The thrombolysis window is still open. If the patient is within 4.5 hours of symptom onset and helicopter evacuation can deliver them to a stroke unit before the window closes, this is the strongest indication for immediate medevac. Calculate: time remaining in the 4.5-hour window minus estimated helicopter transit time to the stroke centre. If this number is positive, the patient may be a thrombolysis candidate, and evacuation should be pursued urgently.
• Large vessel occlusion is suspected. Severe deficits (complete hemiplegia, gaze deviation, global aphasia, NIHSS estimated above 10) suggest large vessel occlusion, which is treatable by thrombectomy up to 24 hours. Even if the thrombolysis window has closed, these patients benefit from urgent transfer to a comprehensive stroke centre.
• The patient is deteriorating. A patient whose neurological status is worsening on serial assessments — declining consciousness, expanding deficit, new symptoms — may be experiencing haemorrhagic transformation or a progressing stroke. Deterioration changes the evacuation calculus because it suggests the patient's condition is time-critical in ways that extend beyond the thrombolysis window.
• The ship is more than 12 hours from a stroke-capable port. Even outside treatment windows, stroke patients benefit from early access to stroke unit care, monitoring, and rehabilitation. Prolonged stabilisation at sea with no imaging capability and no neurology input is suboptimal care, and helicopter evacuation shortens the period of suboptimal management.

The medevac decision tool in the Clinical Tools section can assist with structuring this calculation. The Medevac SBAR Template provides the communication framework for requesting evacuation through the appropriate channels.

Bridge Communication: SBAR-M for Stroke Emergencies

The bridge needs to understand why you are requesting a course change, a speed increase, or a helicopter rendezvous — and they need to understand it in operational terms, not clinical ones. The SBAR-M (Situation, Background, Assessment, Recommendation, Maritime context) format, described in detail in the Bridge Phrases article, provides the structure for this communication.

A stroke-specific SBAR-M might sound like this:

Situation: "I have a 68-year-old male passenger with a suspected stroke. He developed sudden weakness on the right side of his body and cannot speak. Symptoms began approximately 90 minutes ago."

Background: "He has a history of high blood pressure and atrial fibrillation. He was well at dinner and was found by his wife with these symptoms at 2130."

Assessment: "This is likely an acute stroke. There is a 4.5-hour treatment window for clot-dissolving medication, which closes at midnight tonight. He needs to be in a hospital with a CT scanner before that window closes. Without treatment, he is likely to have permanent brain damage."

Recommendation: "I am requesting immediate helicopter evacuation to the nearest stroke centre. If helicopter is not available within two hours, I request maximum speed course change toward the nearest stroke-capable port."

Maritime context: "Current position is approximately 180 nautical miles from [nearest port]. At current speed, ETA is 10 hours. The treatment window will have closed 7 hours before arrival. Helicopter evacuation is the only option that preserves the treatment window."

Note the language. "Clot-dissolving medication" rather than "thrombolysis." "CT scanner" rather than "neuroimaging." "Permanent brain damage" rather than "poor neurological outcome." The bridge team are professional mariners, not clinicians. Your communication must translate clinical urgency into language that is both accurate and immediately comprehensible to a non-medical audience. See Bridge Phrases for the full maritime communication framework.

Helicopter Evacuation Considerations

If helicopter evacuation is authorised, your preparation of the patient for transfer must account for the unique constraints of aeromedical evacuation at sea.

• Patient positioning. The patient will be transferred in a stretcher, typically via winch. Ensure the patient is secured, with the head elevated if the stretcher allows it. If the patient is vomiting or has a reduced level of consciousness, they may need to be positioned on their side for airway protection during the winch transfer.
• IV access. Secure at least one large-bore IV cannula before the helicopter arrives. Tape it extensively — the rotor wash and movement during transfer will dislodge anything that is not firmly secured. If you have established two IV lines, secure both.
• Monitoring during transfer. If the flight paramedic or doctor will accompany the patient, prepare a concise handover. If the patient will fly without a clinician (which is uncommon but occurs with some coast guard evacuations), ensure vital signs are documented immediately before departure and that the patient is in the most stable position possible.
• Documentation for the flight crew. Prepare a written summary that includes: time of symptom onset, FAST findings, blood pressure trend, blood glucose, current medications, medical history, allergies, and your clinical assessment. Attach this to the patient. Do not rely on verbal handover alone — the noise on a helicopter deck makes verbal communication unreliable.
• Medications. Send all relevant medications with the patient, clearly labelled. If you have administered any medications, document what was given, the dose, the route, and the time.

Coordinate with the bridge regarding the helicopter approach. The ship may need to alter course to create a suitable wind-over-deck for the helicopter operation. The medical urgency must be balanced against the safety requirements of the flight crew, and this negotiation happens between the bridge and the helicopter pilot — not between the doctor and the pilot.

Documentation and Handover

In stroke care, documentation of symptom onset time is not merely good practice. It is the single most important piece of information for the receiving stroke team, because it determines treatment eligibility. Get it wrong, and a treatable patient may be denied thrombolysis. Fail to record it, and the receiving team must make conservative assumptions that may exclude the patient from treatment.

Your documentation should include:

1. Exact time of symptom onset (or the time the patient was last known to be neurologically normal). Record how this time was established: patient report, witness report, cabin steward observation, CCTV review. If the onset is uncertain, document the range of uncertainty.
2. Serial neurological assessments with timestamps. What was the deficit at first assessment? Did it change? At what time did it change? Is it stable, improving, or worsening?
3. Blood pressure readings with timestamps. Every 15 minutes in the acute phase, then every 30 minutes once the patient is stable.
4. Blood glucose readings with timestamps. Initial reading plus serial readings every 30 minutes.
5. All medications administered, with drug name, dose, route, and time.
6. All communications with the bridge, the coast guard, TMAS (Telemedical Maritime Assistance Service), and the receiving facility. Record the time of each communication, who you spoke to, what you communicated, and what was decided.
7. The evacuation timeline: when evacuation was requested, when it was authorised, when the helicopter arrived, when the patient departed the ship.

This documentation serves two purposes. Clinically, it provides the receiving stroke team with a precise timeline that guides their treatment decisions. Medicolegally, it demonstrates that you recognised the time-critical nature of the presentation, managed the patient appropriately within the constraints of the maritime environment, and communicated the urgency through appropriate channels.

Stroke Mimics at Sea: The Broader Differential

Beyond the common mimics discussed earlier, the maritime environment introduces additional diagnostic considerations that are less common ashore:

• Carbon monoxide poisoning. On vessels with internal combustion engines, incomplete combustion can produce carbon monoxide in enclosed spaces. CO poisoning can present with headache, confusion, and focal neurological signs. If the patient was in an engine room, a poorly ventilated cabin, or near exhaust systems, consider CO exposure. A CO-oximeter, if available, confirms the diagnosis.
• Decompression illness. If the patient is a diver or has been involved in any hyperbaric exposure, neurological decompression sickness can closely mimic stroke. Arterial gas embolism can produce sudden-onset focal deficits that are indistinguishable from ischaemic stroke. Ask specifically about diving activity in the preceding 48 hours.
• Heat stroke. Patients exposed to high ambient temperatures, particularly crew members working in engine rooms or on deck in tropical conditions, can develop hyperthermia with neurological dysfunction including confusion, ataxia, and focal deficits. Core temperature measurement is essential — a temperature above 40 degrees Celsius with neurological symptoms is heat stroke until proven otherwise.
• Medication effects. Seasickness medications (scopolamine patches, high-dose antihistamines), opioid analgesics, and benzodiazepines can produce neurological symptoms that mimic stroke in vulnerable patients. Review the medication history carefully, including over-the-counter seasickness remedies.
• Electrolyte disturbances. Severe hyponatraemia from excessive water intake, prolonged vomiting, or inappropriate ADH secretion can produce confusion, seizures, and focal deficits. If you have the ability to check serum sodium, do so. If not, consider the clinical context: has the patient been vomiting for days? Are they on medications that cause hyponatraemia?

The presence of a plausible mimic does not exclude stroke. Both conditions can coexist, and the safest approach at sea is to treat any acute focal neurological deficit as a potential stroke while simultaneously screening for and treating reversible causes. Correct the glucose. Treat the fever. Check the CO level. But continue the stroke pathway until imaging excludes it.

At sea, you cannot confirm stroke. But you can exclude the mimics that would change your management entirely — and that distinction makes the difference between a patient who receives appropriate care and one who does not.

References

1. Powers WJ, Rabinstein AA, Ackerson T, et al. Guidelines for the Early Management of Patients With Acute Ischemic Stroke: 2019 Update to the 2018 Guidelines. Stroke. 2019;50(12):e344–e418. American Heart Association / American Stroke Association.
2. Berge E, Whiteley W, Audebert H, et al. European Stroke Organisation (ESO) guidelines on intravenous thrombolysis for acute ischaemic stroke. European Stroke Journal. 2021;6(1):I–LXII.
3. Nogueira RG, Jadhav AP, Haussen DC, et al. Thrombectomy 6 to 24 Hours after Stroke with a Mismatch between Deficit and Infarct (DAWN Trial). N Engl J Med. 2018;378(1):11–21.
4. Maritime and Coastguard Agency. The Ship Captain's Medical Guide. 23rd edition. London: TSO; 2019.
5. World Health Organization. International Medical Guide for Ships. 3rd edition. Geneva: WHO; 2007.
6. Dahl E. Passenger mortalities aboard ocean cruise ships. Int Marit Health. 2001;52(1–4):19–23.
7. Lucas R, Boniface K, Engel J. Stroke management in the austere environment. Wilderness Environ Med. 2021;32(3):367–377.
8. Saver JL. Time is brain — quantified. Stroke. 2006;37(1):263–266.

Continue Reading

• Oxygen Is a Clock at Sea
• Why Ship Doctors Need Bridge Phrases
• The 72-Hour Maritime ICU Problem
• When the Patient Is Stable but the Ship Is Not