Vomiting, or emesis, is a forceful reflex that expels stomach contents through the mouth. Blood pressure (BP) is the force of blood pushing against the walls of your arteries, measured as systolic pressure over diastolic pressure. The answer to whether vomiting increases blood pressure is twofold: the physical act itself causes a brief, sharp rise in pressure, but repeated or prolonged episodes typically lead to a systemic drop in blood pressure.
The Immediate Spike in Blood Pressure
The initial, transient increase in blood pressure during an episode of vomiting is a direct result of intense physical exertion. The act of emesis requires a powerful, coordinated contraction of the abdominal muscles, diaphragm, and chest wall. This muscular effort creates a sudden and dramatic increase in both intra-abdominal and intrathoracic pressure.
The physiological response mirrors the initial phase of what is known as the Valsalva maneuver, where a person strains against a closed airway. This sudden pressure surge compresses the arteries and veins in the chest and abdomen, which momentarily increases the pressure in the aorta and other major blood vessels.
In healthy individuals, this temporary pressure increase is managed effectively by the body’s cardiovascular reflexes, and the blood pressure quickly returns to its baseline level once the retching ceases. However, this sudden spike can pose a risk to people with pre-existing conditions, particularly those with weakened or diseased blood vessels.
How Prolonged Vomiting Leads to Low Blood Pressure
While the physical strain of vomiting causes a temporary rise in pressure, the systemic consequence of repeated or prolonged episodes is a reduction in circulating blood volume, which leads to hypotension, or low blood pressure. Vomiting results in the rapid loss of fluids and key electrolytes, such as sodium and potassium. This fluid deficit is what causes dehydration, which is the primary driver of the subsequent drop in blood pressure.
Dehydration directly lowers the body’s total plasma volume, meaning there is less fluid circulating through the blood vessels. This decreased blood volume reduces the amount of blood returning to the heart, which in turn lowers the heart’s stroke volume and overall cardiac output. The body attempts to compensate for this reduced volume by increasing the heart rate, a condition called compensatory tachycardia, to keep blood flowing to the brain and other organs.
This state of reduced blood volume often causes orthostatic hypotension, where a person feels dizzy or lightheaded upon standing up. If the fluid loss becomes severe, the resulting drop in blood pressure can progress to hypovolemic shock, a life-threatening condition where organs do not receive enough oxygen and nutrients.
Recognizing Serious Complications
Severe dehydration, a direct consequence of prolonged vomiting, requires immediate medical attention if the patient is unable to keep any liquids down. Signs of severe volume loss include profound thirst, reduced or absent urination, and confusion or lethargy.
One acute physical complication is the potential for an esophageal tear, known as a Mallory-Weiss tear, which is caused by the violent muscle contractions during retching. This tear can lead to bleeding and is signaled by the presence of blood in the vomit.
A severe headache or persistent chest pain following an episode of vomiting also warrants emergency evaluation, as this combination of symptoms may indicate a more serious event, such as a possible stroke. The sudden increase in pressure can potentially trigger a cerebrovascular event, such as an intracranial hemorrhage, especially if the patient also experiences a severe, acute headache.
Any instance where vomiting is accompanied by symptoms like unremitting chest pain, neurological changes, or a blood pressure reading that remains severely elevated or dangerously low should prompt an immediate consultation with a healthcare provider.