Infections are one of the main causes of physical illness. Infections can happen in various ways and the severity of the infection can vary depending on multiple factors such as:

• The overall health of the person, including any pre-existing conditions they may have
• The age and sex of the person
• The characteristics of the pathogen the person is infected with

Septic thrombophlebitis is an example of a rare infection that can occur when a blood clot forms in a vein and becomes infected. This is a life-threatening condition which can cause serious complications in the patient such as sepsis, organ failure, and even death if it is left untreated.¹ Septic thrombophlebitis differs from thrombophlebitis as there are bacteria or fungi present within the blood clot.² The presence of bacteria or fungi within the blood clot is the reason why this particular thrombophlebitis is extremely dangerous as the infection could spread to different parts of the body. If this were to happen, the body would produce an immune response to fight the infection; however, in the case of septic thrombophlebitis, the immune response produced could lead to even more complications. The severity of this type of infection and its mechanisms will be explored within this article.

How does septic thrombophlebitis occur?

The formation of the blood clot

When a blood vessel is damaged, the cells in the blood vessel will release chemical signals, triggering a response to prevent blood from leaking out.³ Firstly, the blood vessel narrows to prevent any further blood from leaking out;³ then, platelets and proteins with the plasma will work together to form a plug over the site of injury, which eventually becomes a clot.⁴ Blood clots in blood vessels are called a thrombus. After the formation of a thrombus, the body will then repair the injury and naturally dissolve the thrombus once the blood vessel has healed.^3,4 

Sometimes, however, the blood clot does not naturally dissolve or will detach from the site of injury and travel to other parts of the body (called embolisation). This is particularly dangerous as it could potentially restrict the blood flow to important organs of the body, such as the heart and lungs (pulmonary embolisation). Clots may suddenly form in veins too, and can be caused by either slow or stagnant blood flow, known as adeep vein thrombosis (DVT); or due to a person suffering from thrombophilia, a condition where the blood has an increased tendency to form blood clots (hypercoagulability).⁴ 

How are bacteria and fungi introduced into the body?

Bacteria and fungi infect the site of the thrombus when it is introduced into the bloodstream through various ways. One of the main causes is when a medical line or tube is inserted into the body to deliver treatment to the patient or to monitor their health. Some examples include:

• Peripheral IV(Intravenous) catheter (IVs)
• Central venous catheter(CVC) also known as central lines
• Peripherally inserted central catheters (PICCs)
• Pacemakers
• Nasogastric tubes^5,6

Medical lines and tubes are invasive, meaning that it goes inside the body either through cutting or puncturing the skin, or through an orifice on the body.⁷ This could introduce bacteria or fungi into the body as they are considered ‘foreign’ since it comes from outside the body. Septic thrombophlebitis is a complication that can occur after a line is inserted in the body as there is a risk of a blood clot forming around the object. Other ways bacteria can be introduced to the body are through:

• Infection post surgery
• Untreated skin infections
• Severe pre-existing infections in the body

Newborns, the elderly, and women who have recently given birth are some of the groups of people who are most likely at risk of developing septic thrombophlebitis. This is due to their immune systems being very weak in comparison to a healthy person, which in turn increases their risk of them getting an infection on top of the infection itself lasting longer. Other risk factors include:

• Prolonged IV catheter use
• Immunosuppression causing a weakened immune system
• IV drug use
• Any invasive procedures²

What are the symptoms of septic thrombophlebitis?

The typical symptoms are:

• Swelling of the area, typically in the veins closest to the skin. If there are clots in multiple veins, it will appear as multiple lumps in the affected limb
• Pain or soreness in the affected area
• Redness
• Warmth
• Fever⁸

These symptoms are used to help with the diagnosis of thrombophlebitis. They are usually identified during the physical examination where the doctor examines the affected area and the medical history of the patient. To determine if it is septic thrombophlebitis, a series of tests are performed which include:

• Blood culture to detect bacteria or fungi in the bloodstream
• CT scan, or an MRI and MR venography if CT scanning isn’t available
• Ultrasound
• Laboratory tests such as complete blood count, white blood cell count, presence of inflammatory markers²

What are the complications that could occur?

The complications that septic thrombophlebitis can occur are usually serious, hence emphasising the importance of early detection of this infection. Here are some examples.

Sepsis and septic shock

One of the main complications is sepsis and septic shock. This occurs since the infected blood clot contains bacteria or fungi which continually release into the bloodstream until it is dealt with by the immune cells of the body. It causes bacteremia or fungemia. The presence of these pathogens triggers an immune response in the body; however, sometimes the immune response is so overwhelming that it starts to damage your own body, which is known as sepsis.⁹ If left untreated, the body can go into septic shock, which leads to multiple organ failure and potentially death.

Pulmonary embolism

A pulmonary embolism can occur when a piece of the blood clot breaks off, becoming an embolus, and travels through the bloodstream until it reaches and becomes lodged in one of the arteries that supply blood to the lungs (pulmonary arteries). Since the blood clot also contains a pathogen, it can also trigger an immune response which could lead to sepsis. 

Endocarditis

Similarly to a pulmonary embolism, a fragment of the infected blood clot could travel to the heart valves or the inner lining of the heart (endocardium) and attach to it. Once attached, the pathogen can infect the heart structures, leading to it becoming infected and inflamed, which is known as endocarditis.

How can it be treated?

The treatment of septic thrombophlebitis is dependent on various factors such as:

• The source of infection
• The organisms involved
• The structures being affected
• The patient’s medical history

However, the main treatments provided focus on treating the infection. This includes removing the site of infection, which could be done by removing the IV or CVC and administering antibiotics to the patient.² Blood thinners and surgical intervention may be considered if the risk of clotting is high within the patient.⁸ Some supportive treatments to help with managing the symptoms include the prescription of pain medications, warm compresses, elevation of the affected limb, and compression items to prevent further clots from occurring.⁸

Summary

Septic thrombophlebitis is a preventable condition despite it being life-threatening. Proper IV line care and infection control should be a priority to reduce cases of this condition, especially in high-risk groups such as newborns, the elderly, or people who are immunocompromised. These patients should be closely observed for the symptoms of this condition as early diagnosis and treatment can help prevent serious complications from occuring.