A concussion is a mild traumatic brain injury that temporarily disrupts normal brain function. Low blood pressure, or hypotension, occurs when the force of blood pushing against artery walls is abnormally low, resulting in insufficient blood flow to the body’s organs. Research confirms a physiological relationship exists between these two conditions, as a head injury can interfere with the systems responsible for regulating circulation. This article explores how a concussion can lead to low blood pressure and how this condition is managed.
Concussion and Autonomic Dysfunction
The body’s control over heart rate, breathing, and blood pressure is maintained by the Autonomic Nervous System (ANS). This system is primarily regulated by centers within the brainstem. A concussion causes a widespread bio-chemical and functional disturbance across these neural pathways, even without visible structural damage on imaging.
This disruption is known as dysautonomia, representing an imbalance within the ANS. The ANS is divided into the sympathetic (“fight-or-flight”) and parasympathetic (“rest-and-digest”) systems. Following a concussion, the balance between these two branches can be thrown off, often leading to a failure of appropriate signaling.
When the ANS is unable to send the correct signals, the body loses its ability to maintain stable blood pressure and heart rate. This instability affects the cardiovascular system’s response to demands like changing posture. This dysfunction, which can manifest as either high or low blood pressure, is a direct consequence of the brain injury.
Understanding Orthostatic Hypotension After Head Injury
The most frequent clinical manifestation of post-concussion low blood pressure is Orthostatic Hypotension (OH). OH is defined by an abnormal drop in blood pressure that occurs when a person moves from a lying or sitting position to an upright standing posture, due to a failure of the body’s compensatory mechanisms against gravity.
When standing up, gravity causes blood to pool in the lower extremities and abdomen. In a healthy person, the ANS immediately triggers vasoconstriction, or tightening of the blood vessels, and increases heart rate to push blood back toward the brain. In the concussed brain, the dysregulated ANS often fails to initiate this rapid and adequate vasoconstriction response.
The result is a temporary, measurable drop in systolic blood pressure of 20 mmHg or more, or a drop in diastolic blood pressure of 10 mmHg or more within three minutes of standing. This insufficient response leads to a transient reduction in blood flow to the brain, which directly causes the patient’s symptoms.
Identifying Symptoms Related to Low Blood Pressure
The symptoms of low blood pressure following a concussion stem primarily from inadequate blood flow reaching the brain. Patients often report lightheadedness or a feeling of being unsteady, particularly when transitioning to a standing position. This sensation is known as pre-syncope, the feeling that one is about to faint.
In more severe cases, the lack of cerebral blood flow can lead to syncope, or temporary loss of consciousness. Individuals also experience persistent fatigue, generalized weakness, and difficulty concentrating. They may also notice visual disturbances like the world briefly “greying out” or developing “tunnel vision” immediately after standing up.
These symptoms can be compounded by environmental factors. Heat or dehydration further reduce overall blood volume, worsening the body’s ability to maintain pressure.
Diagnosis and Strategies for Managing Hypotension
Diagnosis of post-concussion hypotension involves specialized testing to observe the body’s reaction to positional changes. The Active Standing Test measures blood pressure and heart rate as the patient moves from lying down to standing. For a more definitive assessment, a physician may order a Tilt Table Test, which monitors vital signs while the patient is slowly tilted upright.
Management focuses on restoring fluid balance and training the cardiovascular system to adapt to upright posture. Non-pharmacological interventions are the first line of defense. These include significantly increasing fluid and salt intake to boost overall blood volume. Wearing compression garments, such as waist-high stockings, also helps prevent blood from pooling in the lower body.
Patients are often advised to raise the head of their bed by a few inches to induce a mild gravitational stimulus overnight, helping the ANS acclimatize. If lifestyle changes are insufficient, a physician may consider pharmacological options. These medications are designed to enhance vascular tone or help the body retain salt and water. Consulting a neurologist or a concussion specialist is important to tailor a management plan that safely supports the patient’s return to activity.