Septic Shock: Symptoms, Causes & Treatment

Septic shock is a life-threatening complication of sepsis. It happens when a large amount of microbial toxin enters the bloodstream, causing a sharp drop in blood pressure and a rise in circulating lactate.

As blood pressure falls, blood has a harder time circulating effectively. This reduces oxygen delivery to vital organs such as the brain, heart, and kidneys.

Because of this reduced circulation and oxygen delivery, more specific signs and symptoms can develop. These include decreased urine output and changes in mental status.

Main symptoms

The main symptoms of septic shock are:

• High, persistent fever;

• Increased heart rate;

• Very low blood pressure, with mean arterial pressure (MAP) less than or equal to 65 mmHg;

• Increased circulating lactate, with levels above 2.0 mmol/L;

• Rapid breathing in an attempt to increase circulating oxygen;

• Temperature higher than normal or an excessive drop in body temperature;

• Decreased urine output;

• Loss of consciousness or confusion

Symptoms of septic shock appear when microorganisms enter the bloodstream and release toxins that trigger an immune response. The body produces inflammatory substances to fight the infection, but if treatment is ineffective or the toxin load is high, the condition can worsen from sepsis to severe sepsis and, ultimately, septic shock.

High toxin levels can severely reduce oxygen delivery to vital organs. According to the World Health Organization (WHO), if sepsis is not recognized and treated promptly, it can lead to septic shock, multiple organ failure, and death.

Confirming a diagnosis

Septic shock is diagnosed based on a person's signs and symptoms and the results of lab tests. Common tests include a complete blood count (CBC), electrolyte measurements, and kidney function tests, which are often abnormal in septic shock.

Additional tests may include blood oxygen assessment, LDH measurement, and blood pressure monitoring. Blood pressure typically remains low even after treatment has started.

To identify the microorganism causing septic shock, a doctor may order blood cultures. These are typically performed by analyzing three blood samples collected in the hospital.

Common causes

The main causes of septic shock are:

• Bacteria, such as Staphylococcus aureus, Streptococcus pneumoniae, Klebsiella pneumoniae, Escherichia coli (E. coli), Pseudomonas aeruginosa, Streptococcus sp., and Neisseria meningitidis, among others

• Viruses, such as influenza H1N1, H5N1, yellow fever virus, or dengue virus, among others;

• Fungi, mainly from the Candida genus.

According to the CDC, infections leading to sepsis most often begin in the lungs, urinary tract, skin, or gastrointestinal tract. Common examples include pneumonia, urinary tract infections, meningitis, erysipelas, infectious cellulitis, surgical wound infections, and catheter-related contamination.

Septic shock is associated with microorganism resistance to treatment and the person’s immune response.

Medical devices such as tubes and catheters also raise infection risk, as they can introduce microorganisms into the bloodstream, where they multiply and release toxins that impair organ function and oxygen delivery.

Risk factors

Factors that increase the risk of septic shock include:

• ICU hospitalization;

• Use of tubes and catheters;

• Undergoing invasive tests or procedures;

• A weakened immune system due to age or illness;

• Chronic diseases, such as diabetes mellitus, heart failure, bone marrow aplasia, and kidney failure.

In addition, the use of immunosuppressive treatments such as chemotherapy, corticosteroids, antibiotics, or radiation therapy can increase the risk of sepsis and septic shock. These treatments can reduce the immune system’s ability to respond to infection.

Treatment options

Treatment for septic shock must be done in the ICU (Intensive Care Unit). The following may be recommended:

1. Use of antibiotics

When septic shock is confirmed, treatment should begin immediately with a broad-spectrum antibiotic, even if the source of infection has not yet been identified. This approach helps eliminate the causative microorganism as quickly as possible.

Evaluating the infectious agent’s sensitivity and resistance profile is essential to guide the choice of the most effective antibiotic.

2. IV fluids

In septic shock, blood circulation is severely impaired, which can reduce oxygen delivery throughout the body. High-volume IV fluids, about 30 mL per kg, are recommended to help maintain adequate blood flow and improve response to medications.

3. Medications for blood pressure

Because low blood pressure often does not improve with IV fluids alone, medications called vasopressors are usually needed. The goal is to reach a mean arterial pressure of at least 65 mmHg.

Examples include norepinephrine, vasopressin, dopamine, and epinephrine, which require strict clinical monitoring to reduce the risk of complications. Another option is using medications that strengthen heart contractions, such as dobutamine.

4. Blood transfusion

A blood transfusion may be needed for patients with signs of inadequate blood flow and anemia with hemoglobin below 7 g/dL.

5. Use of corticosteroids

Corticosteroids such as hydrocortisone may be used to help reduce inflammation.

However, benefits are seen mainly in refractory septic shock, meaning cases in which blood pressure does not improve even with IV fluids and medications.

6. Hemodialysis

Hemodialysis is not always indicated. However, it may be used in severe cases when excess electrolytes must be removed quickly, blood acidity needs correction, or kidney function has stopped.