Seizures can definitively cause low blood pressure (hypotension). A seizure is a temporary episode resulting from abnormal, excessive neuronal activity in the brain. These electrical disturbances can spread to areas controlling the body’s involuntary functions, including blood pressure regulation. Hypotension is typically defined as a reading lower than 90 millimeters of mercury (mm Hg) systolic over 60 mm Hg diastolic.
How Seizures Disrupt Blood Pressure Regulation
The brain maintains stable blood pressure through the Autonomic Nervous System (ANS), which operates outside of conscious control. The ANS has two main branches: the sympathetic system (fight-or-flight) and the parasympathetic system (rest-and-digest). While most seizures trigger a sympathetic surge leading to a temporary increase in blood pressure, some seizures cause the opposite effect. The uncontrolled electrical discharge can propagate to areas of the central autonomic network, such as the insular cortex or the hypothalamus, which are deeply involved in cardiovascular control.
If seizure activity stimulates regions that promote parasympathetic outflow, it leads to an inappropriate dominance of the “rest and digest” response. This shift results in a dual effect: bradycardia (slowing of the heart rate) and vasodilation (widening of the blood vessels). The combination of a slower heart and wider vascular space significantly reduces the pressure within the arteries, leading to hypotension.
Recognizing Hypotension During and After a Seizure
The drop in blood pressure can occur during the seizure (ictal) or, more commonly, immediately following it (post-ictal). During a generalized convulsive seizure, changes in blood pressure are often difficult to measure accurately due to movement. Post-ictal hypotension sometimes lasts for more than a minute after the seizure has ended.
This sudden drop presents with observable signs and symptoms. Common complaints include dizziness, lightheadedness, and profound nausea. An observer might notice pallor in the patient’s skin. Severe hypotension can lead to syncope (temporary loss of consciousness) or near-fainting (presyncope).
Severe post-ictal hypotension may be linked to a failure of the body’s baroreflex sensitivity, the mechanism that rapidly adjusts blood pressure. This failure, combined with pooling of blood in the dilated vessels, can result in insufficient blood flow to the brain (cerebral hypo-perfusion). This lack of adequate blood supply increases the risk of injury from falling and has been implicated as a possible mechanism in sudden unexpected death in epilepsy (SUDEP).
Addressing Low Blood Pressure in Seizure Management
Managing low blood pressure requires a focus on both immediate stabilization and long-term seizure control. In a clinical setting, continuous monitoring of vital signs is important for high-risk patients or immediately following a severe seizure. Accurate measurement helps distinguish a transient drop from a more sustained hypotensive episode.
For immediate, mild post-seizure hypotension, positional changes can be helpful, such as having the individual lie down or raising their legs. If the drop is significant and prolonged, medical intervention may be necessary, often including rapid administration of intravenous (IV) fluids to increase blood volume and pressure.
In cases of life-threatening hypotension or status epilepticus, healthcare providers must carefully select anti-seizure medications, as some can worsen low blood pressure. For example, medications like propofol are generally avoided in hypotensive patients. Adjusting a patient’s long-term antiseizure medication regimen may also be necessary if a specific drug contributes to chronic hypotension. Ongoing communication with a healthcare provider is essential to ensure a management plan that balances seizure control with cardiovascular stability.