Normal blood pressure is around 120/80 mmHg; 90/60 mmHg or lower is defined as hypotension. This condition can lead to insufficient blood flow to the body’s organs, causing a range of symptoms. For people with cancer, low blood pressure is a frequent complication resulting from the disease, its progression, or the various treatments used to fight it. Understanding the specific causes behind this drop in pressure is important for effective patient management.
Mechanisms of Cancer-Related Hypotension
The malignancy itself can trigger systemic changes leading to a drop in blood pressure, separate from medical intervention. One of the most common internal causes is systemic inflammation, which can progress to sepsis, a severe blood infection. In this state, the body releases inflammatory molecules that cause blood vessels to widen significantly, a process called vasodilation, which lowers overall vascular resistance and blood pressure.
Advanced cancer frequently involves cancer cachexia, a wasting syndrome characterized by profound weight loss and muscle loss. This condition often results in volume depletion, meaning a reduction in the total amount of circulating blood and fluid. The loss of skeletal muscle bulk may also impair the body’s ability to return blood to the heart when standing, contributing to orthostatic hypotension.
Tumors can mechanically or functionally affect the cardiovascular system, contributing to hypotension. Malignancy can cause a pericardial effusion, which is an accumulation of fluid in the sac surrounding the heart. If this fluid builds up quickly, it can compress the heart chambers, a life-threatening condition called cardiac tamponade, which severely restricts the heart’s ability to fill with blood and pump effectively.
Certain cancers can also cause paraneoplastic syndromes, which are effects due to substances released by the tumor rather than its size or location. Paraneoplastic autonomic neuropathy, often seen with small-cell lung cancer, can disrupt the nervous system’s control over blood pressure, leading to persistent or positional hypotension. Other endocrine tumors may disrupt hormonal balances that regulate fluid and blood pressure.
Treatment-Induced Low Blood Pressure
Many cancer treatments can inadvertently cause a drop in blood pressure as a side effect. Chemotherapy drugs, such as certain anthracyclines, can be cardiotoxic, weakening the heart’s ability to pump blood and leading to decreased cardiac output and low blood pressure. Other agents, like irinotecan, may cause non-allergic hypotension by affecting the autonomic nervous system through mechanisms like cholinesterase inhibition.
A frequent indirect cause of hypotension during treatment is severe gastrointestinal side effects. Chemotherapy and radiation can induce extreme nausea, vomiting, and diarrhea, leading to a significant loss of water and electrolytes from the body. This rapid fluid loss results in hypovolemia, a state of low blood volume that directly causes blood pressure to fall.
Acute, sudden drops in blood pressure can occur due to immediate reactions to the drug infusion. Hypersensitivity or allergic reactions to chemotherapy or biologic agents cause the rapid release of inflammatory mediators, resulting in widespread vasodilation and a sudden drop in systemic blood pressure. Additionally, bone marrow damage from chemotherapy can lead to anemia, which reduces the blood’s oxygen-carrying capacity and may contribute to low blood pressure.
Radiation therapy directed at the chest area, particularly for cancers like lung or breast cancer, can have long-term effects on the heart and surrounding structures. Cranio-cervical radiation, for example, can impair the function of baroreceptors, which are the body’s natural pressure sensors, disrupting their ability to regulate blood pressure effectively. This can lead to issues with maintaining stable blood pressure, especially when changing position.
Symptoms and Clinical Management of Hypotension in Cancer Patients
The symptoms of low blood pressure occur because vital organs, especially the brain, are not receiving enough oxygenated blood. Patients commonly report feeling lightheaded or dizzy, particularly when moving from a sitting or lying position to standing, which is a classic sign of orthostatic hypotension. Other frequent complaints include fatigue and weakness.
More severe symptoms can include confusion, blurred vision, and nausea, and in the most serious cases, the patient may faint or lose consciousness. These symptoms can be challenging to identify in cancer patients, as they often overlap with the fatigue and discomfort caused by the disease or its ongoing treatment. Fever and chills accompanying low blood pressure can be a sign of a severe infection like sepsis, which requires immediate attention.
Clinical management focuses on identifying and correcting the underlying cause while stabilizing the patient’s condition. For cases related to hypovolemia or dehydration, the primary immediate response is fluid replacement, often with intravenous isotonic saline solution to quickly restore circulating blood volume. If a specific medication is identified as the cause, the dosage may be adjusted or the drug may be discontinued entirely.
For patients experiencing orthostatic hypotension, simple measures are often recommended, such as moving slowly and deliberately when changing body positions. Healthcare providers also monitor for and discontinue any non-cancer-related medications, such as those for high blood pressure, which may be contributing to the low pressure. In complex cases, especially those involving paraneoplastic syndromes, the treatment of the underlying malignancy is the most effective approach to resolving the associated hypotension.