Cushing's Triad: Signs of Rising Intracranial Pressure

Cushing's triad is three vital sign changes that together point to dangerously high pressure inside the skull: rising blood pressure with a widening pulse pressure, a slowing heart rate, and irregular breathing. It is named for the neurosurgeon Harvey Cushing, who described the reflex behind it around 1900. It is not the same thing as Cushing's syndrome, which is a hormone disorder and has nothing to do with this.

What is happening inside the skull

The skull is a closed box holding brain, blood and cerebrospinal fluid. When something takes up more room, such as bleeding, swelling, a tumor or blocked fluid drainage, the pressure inside the box rises. Blood can only reach the brain if the pressure pushing it in is higher than the pressure inside the skull. As intracranial pressure climbs, the brain's blood supply falls.

Cushing's triad is the body's last attempt to keep blood flowing to the brain, and the signs of the brainstem beginning to fail.

The three signs

The combination is what matters. A fast heart rate and low blood pressure in a head-injured patient is a different picture, and usually means bleeding somewhere else. A slow heart rate with a high and climbing pressure in a patient whose level of consciousness is falling is the pattern to recognize.

A late sign, and the earlier ones

By the time all three signs are present the brain is often herniating, which means being pushed through the openings in the skull. Many patients show only one or two of the signs, and some deteriorate without a clear triad at all. Waiting for the full triad means waiting too long.

The earlier warnings of rising pressure are in the neurological exam, which is why it is repeated so often on a head-injured patient.

• A falling level of consciousness. A drop in the GCS or a patient who becomes harder to rouse is the most important trend to catch.
• A pupil that becomes larger, slower to react or fixed, usually on one side first.
• Abnormal posturing: flexion or extension of the arms in response to pain.
• Weakness on one side of the body.
• Severe or worsening headache, vomiting, confusion or agitation in a patient who can still report them.
• A seizure.

Common causes

• Traumatic brain injury, especially an expanding bleed after a fall or a blow to the head, which can follow a lucid interval in which the patient seemed fine.
• Bleeding stroke.
• A brain tumor.
• Infection such as meningitis or an abscess.
• Blocked drainage of cerebrospinal fluid, including a failed shunt in a child or adult who has one.

In infants and children

An infant whose skull bones have not yet fused may show a bulging fontanelle, a high-pitched cry, irritability, poor feeding or vomiting before vital signs change. Ask about a shunt in any child with a known history of hydrocephalus, because a blocked shunt is a common and treatable cause. Normal vital signs change with age, so judge a child's heart rate and pressure against the norms for their age.

EMS priorities

There is no prehospital treatment for the cause of raised intracranial pressure. What EMS controls is how much further damage the brain suffers on the way to definitive care. The Brain Trauma Foundation's prehospital guidelines for traumatic brain injury, now in their third edition, are built around a short list of principles, and your protocol turns them into numbers.

• Prevent hypoxia. Even brief periods of low oxygen in a head-injured patient are associated with worse outcomes. Manage the airway and give oxygen to the target your protocol sets.
• Prevent hypotension. A brain under pressure needs blood pressure to be perfused. Treat low pressure as your protocol directs and do not let it go unaddressed.
• Do not treat the high blood pressure. In Cushing's triad the hypertension is what is keeping blood reaching the brain. Bringing it down lowers the brain's blood supply.
• Ventilate normally. Over-breathing for a patient lowers carbon dioxide, which narrows the blood vessels in the brain and reduces blood flow to it. Routine hyperventilation is not recommended. Any deliberate change in ventilation for signs of herniation is a protocol decision, and capnography is how you know what you are actually doing.
• Check the blood glucose, because low blood sugar causes altered mental status and is correctable.
• Elevate the head if spinal precautions and blood pressure allow it and your protocol calls for it, and make sure nothing around the neck, including a collar, is tight enough to obstruct venous drainage.
• Repeat and record the neurological exam, including GCS and pupils, so a change can be seen and reported.
• Transport without delay to a facility your system designates for this kind of patient, and tell them early what you are seeing.

Score and trend the Glasgow Coma Scale

Score the pediatric Glasgow Coma Scale for a preverbal child

Cushing's triad and Beck's triad

The two triads are often learned together and confused on exams. Beck's triad (low blood pressure, distended neck veins and muffled heart sounds) suggests cardiac tamponade, and its blood pressure goes down. Cushing's triad suggests raised intracranial pressure, and its blood pressure goes up while the heart rate goes down.

The short version

• Cushing's triad is a rising blood pressure with a widening pulse pressure, a slowing heart rate and irregular breathing.
• It means raised intracranial pressure and often herniation. It is a late sign.
• Catch it earlier in the neurological exam: a falling GCS, a changing pupil, posturing.
• Prevent hypoxia and hypotension, ventilate normally, and do not lower the blood pressure.
• Your protocol sets the numbers. Transport without delay.