Postoperative Hypotension: Causes, Symptoms, and Treatment

Introduction

Low blood pressure is also called hypotension. The postoperative (after-surgery) period can be dangerous for patients and associated with significant harm due to hypotension. The mortality is higher in patients postoperatively as compared to preoperative and it is the third leading cause of death in the United States. Critically ill patients such as kidney, myocardial, and liver injury have increased risk of hypotension. Many research has found that patients in surgical intensive care units (ICU) are sensitive to mild amounts of hypotension. Therefore, postoperative care is more important and also it is not expensive. Furthermore, regular monitoring of blood pressure may support early intervention and lead to improved clinical outcomes, lowering the risk of postoperative organ dysfunction including the danger of acute kidney injury.

What Is Postoperative Hypotension?

Hypotension refers to low blood pressure when the systolic pressure is less than 90 mm of Hg.

Postoperative hypotension is a medical condition where a patient's blood pressure drops below normal levels after a surgical procedure. This can occur immediately after surgery or within the first few hours following the procedure. The exact definition of postoperative hypotension can vary, but it is generally defined as systolic blood pressure (the top number) less than 90 mmHg or a decrease in systolic blood pressure of more than 30 percent from the patient's baseline blood pressure. Postoperative hypotension can be caused by a number of factors, including the effects of anesthesia, fluid loss during surgery, and changes in blood volume. It can lead to decreased blood flow to vital organs such as the brain, heart, and kidneys, which can result in organ damage or failure if left untreated. Postoperative hypotension is associated with affected surgical patient outcomes. Hypotension and organ dysfunction (improper functioning of the organ) are correlated and can lead to organ failure.

What Are the Causes of Postoperative Hypotension?

Hypotension during the surgery is linked to postoperative mortality, heart failure, kidney failure, shock, and stroke. Low blood pressure is entirely responsible for organ failure. Organ failure can be prevented by continuous monitoring of blood pressure and critical care of the patients after surgery.

The following are the causes of postoperative hypotension:

• Anesthesia – Anesthesia can cause a decrease in blood pressure by relaxing the muscles in the blood vessels, which leads to vasodilation.

• Surgery – During surgery, a patient may lose blood, either due to the surgical procedure or as a result of complications. This can cause a decrease in blood volume, leading to hypotension.

• Old Age – The advanced age of the patients is more prone to hypotension due to poor recovery after surgery.

• Medicine – Hypotension during surgery can be caused due to medicines such as ACE-1 inhibitors. Nin-cardiac medications may also negatively influence blood pressure such as Tamsulosin used to treat urinary tract obstruction have an adverse effect on blood pressure.

• Myocardial Ischemia – Myocardial ischemia is a condition in which the heart muscle’s ability reduces to pump blood.

• Hypovolemia – Low blood plasma is known as hypovolemia. If a patient is not adequately hydrated before and during surgery, they may experience hypotension due to a decrease in blood volume. Hypovolemia can be caused due to excessive bleeding during the surgery.

• Arrhythmias – Arrhythmias is a type of heart problem in which patients have irregular heartbeat.

• Pneumothorax – The condition in which the lungs get collapsed is called pneumothorax.

• Sepsis – Sepsis is a life-threatening condition in which infection occurs in the bloodstream which causes a sudden drop in blood pressure.

• Bleeding – Excessive bleeding during the surgery can cause postoperative hypotension.

What Are the Symptoms of Postoperative Hypotension?

It is not necessary that all patients with postoperative hypotension will experience symptoms, and some symptoms may be subtle or difficult to notice. This is why it is important for healthcare providers to monitor a patient's blood pressure closely during and after surgery and to be aware of the risk factors for postoperative hypotension. If the patients experience any of these symptoms, they should notify their healthcare team immediately so that appropriate treatment can be given.

The symptoms of postoperative hypotension can vary depending on the severity of the condition, but they may include:

• Dizziness or lightheadedness.

• Fainting or feeling faint.

• Nausea or vomiting.

• Blurred vision.

• Confusion or disorientation.

• Rapid heartbeat.

• Shallow breathing.

• Cold, clammy skin.

• Fatigue or weakness.

• Thirst.

How Postoperative Hypotension Can Be Treated?

Postoperative hypotension, or low blood pressure after surgery, can be treated through a variety of methods depending on the underlying cause of the hypotension. The following are the ways to treat postoperative hypotension:

• Fluid Resuscitation: One of the most common causes of postoperative hypotension is hypovolemia or low blood volume. This can be treated by administering fluids such as saline or colloid solutions to increase the circulating blood volume and improve blood pressure.

• Medications: In some cases, hypotension may be caused by inadequate peripheral vascular resistance. In these cases, vasopressor medications such as Norepinephrine, Phenylephrine, or Epinephrine can be used to constrict blood vessels and increase blood pressure.

• Transfusion: Postoperative hypotension may also be caused by anemia or bleeding. If this is the case, a transfusion of blood or blood products may be necessary to restore blood pressure.

• Pain Management: Pain following surgery can cause decreased blood pressure due to increased sympathetic activity. Proper pain management can help reduce the likelihood of this happening.

• Optimization of Oxygen Delivery: Hypotension may also be a result of inadequate oxygen delivery to tissues. Ensuring proper ventilation and oxygenation can help to improve blood pressure.

• Treat Underlying Causes: It is important to identify and treat any underlying causes of hypotension, such as infections, arrhythmias, or cardiac dysfunction.

Conclusion

Organ functions are significantly influenced by blood pressure. Common perioperative hypotension is associated with organ failure and hypoperfusion. Postoperative hypotension can be prevented by regulating blood pressure optimally during the perioperative period. Hypotension is currently treated after low blood pressure levels are identified. Some measures can be taken to treat hypotension and decrease the frequency and duration of hypotensive episodes such as early detection of hypotension or its clinical prediction during preoperative risk assessment for perioperative hypotension, intraoperative monitoring, and postoperative monitoring. Recently, methods based on machine learning (artificial intelligence) have been used to forecast hypotension. However, clinical trials are required to verify if new technologies can accurately forecast hypotension cases.