Chemotherapy is a systemic medical treatment designed to destroy rapidly dividing cancer cells, but it can also affect healthy cells throughout the body. Hypotension is defined as abnormally low blood pressure, occurring when the force of blood pushing against the artery walls is lower than expected. Cancer treatment introduces systemic changes that affect the cardiovascular system and the body’s fluid balance, which regulate blood pressure. The relationship between chemotherapy and low blood pressure is complex, involving both direct drug effects and indirect complications.
Confirming the Link Between Chemotherapy and Hypotension
Chemotherapy can cause or contribute to hypotension, although a direct, drug-specific drop in blood pressure is often less common than other side effects. Some agents, such as bleomycin or irinotecan, are known to have a direct physiological effect on blood pressure regulation. However, most instances of hypotension during cancer therapy result from indirect effects related to treatment side effects.
Chemotherapy-related complications like severe vomiting, diarrhea, or poor appetite can lead to significant dehydration and subsequent low blood pressure. Furthermore, a severe systemic response to infection, such as septic shock, is a major cause of dangerously low blood pressure. This risk is heightened during chemotherapy due to a weakened immune system.
Physiological Reasons for Blood Pressure Reduction
The reduction in blood pressure during chemotherapy is often due to a combination of three distinct physiological mechanisms that disrupt normal circulatory function. The most frequent mechanism is volume depletion, which occurs when the amount of fluid circulating in the blood vessels is significantly reduced. Cytotoxic drugs commonly cause severe nausea, vomiting, and diarrhea, leading to a rapid loss of water and electrolytes.
Poor oral intake, combined with loss of appetite, prevents the body from replenishing lost fluid volume. When total blood volume drops, the heart has less volume to pump, which translates to lower pressure against the vessel walls. Additionally, a drop in red blood cell count (anemia) caused by chemotherapy can contribute to low blood pressure symptoms by reducing the blood’s oxygen-carrying capacity.
A second mechanism involves cardiotoxicity, where certain chemotherapy classes directly impair the heart muscle’s ability to function effectively. Anthracyclines, a common class of chemotherapy drugs, can damage heart cells, leading to reduced cardiac output. If the heart cannot pump a sufficient volume of blood with each beat, the overall pressure exerted on the arteries falls, resulting in hypotension.
The third physiological cause relates to the widening of blood vessels, or vasodilation, often linked to systemic inflammation or direct drug effects. Some drugs, like irinotecan, can induce hypotension by promoting parasympathetic nervous system hyperactivity, causing blood vessels to relax and widen. Acutely, a severe infection can trigger a systemic inflammatory response, causing widespread vasodilation and increased capillary permeability. This combination of vessel widening and volume loss results in a profound drop in blood pressure.
Symptoms and Management of Chemotherapy-Related Hypotension
Recognizing the symptoms of low blood pressure is important. Common signs include feeling lightheaded or dizzy, especially when changing positions, which is known as orthostatic hypotension. Other frequent complaints are overwhelming fatigue, blurred vision, and general malaise.
In more severe cases, patients may experience syncope (fainting), feel nauseous, or notice a rapid, fluttering heart rate (palpitations). If blood pressure drops too low, reduced circulation can also lead to pale skin.
Clinical management begins by addressing the underlying cause of the hypotension. For cases related to dehydration, the primary intervention is the administration of intravenous (IV) fluids to quickly restore circulating blood volume. If the low pressure is due to direct drug effects or cardiotoxicity, the healthcare team may adjust the chemotherapy dose or change the medication schedule.
For severe, persistent hypotension, specialized medications called vasopressors may be used to constrict blood vessels and increase blood pressure. Patients already taking blood pressure medication may have their doses temporarily reduced or stopped to prevent an excessive drop during the treatment cycle. At-home management involves moving slowly when rising from a lying or sitting position to allow the circulatory system time to adjust. Increasing fluid intake is recommended, and a physician may advise cautiously increasing salt intake to help the body retain water. Immediate medical attention is required for warning signs such as a fever of 100.5°F (38°C) or higher, loss of consciousness, or signs of internal bleeding, such as tarry stools.