Overview of Dialysis Catheter
Dialysis catheters are specialized tubes that are inserted through the skin and used for kidney treatment therapies. They allow doctors to reach areas inside blood vessels or the space within the abdomen (the intraperitoneal space). There are two main types of these tubes: one for treatment outside of the body (extracorporeal), used for procedures like hemodialysis, hemofiltration, hemodiafiltration or ultrafiltration; and another for a treatment known as peritoneal dialysis.
In the first case, the catheters act like large central veins, letting blood move in and out of the patient efficiently. In doing so, they temporarily allow the patient’s blood to leave the body for cleaning in a special machine that does the functions mentioned before. Depending on how long the therapy is intended to last, the tube can be inserted directly through the skin into the target vein, or it may pass under the skin through a short tunnel before reaching the vein. A small felt cuff helps hold it in place in the tissue.
On the other hand, for peritoneal dialysis, the catheter lets a fluid, known as dialysate, fill the space within the abdomen (the intraperitoneal space). Here, it stays in contact with the peritoneal membrane (the lining of the abdominal space) for a while before being taken out. This process helps perform dialysis directly across this lining itself.
Anatomy and Physiology of Dialysis Catheter
For temporary kidney treatment using a process known as extracorporeal renal replacement therapy (RRT), non-tunneled catheters are typically inserted into the body. This is done to help your kidneys do their job when they are not working correctly. Often, doctors will use ultrasound to guide the catheter placement because it helps them see under the skin and reduces the chances of complications. Alternatively, they may insert the catheter based on landmarks on the surface of your body.
This catheter can be placed into different large veins such as the internal jugular vein (located on the side of your neck), subclavian vein (beneath your collar bone), and the femoral vein (in your upper thigh). For catheters that are more permanent, known as tunneled cuffed catheters, they are placed into the subclavian vein using an imaging technique known as fluoroscopy.
With catheters placed in the neck or collar bone area, the best spot for the tip of the catheter is where the superior vena cava (a large vein carrying de-oxygenated blood to the heart) and the right atrium (the upper right heart chamber) meet. These catheters are usually about 15cm long. The subclavian vein is not frequently used in urgent situations because the blood flow might be slower, and this spot may later affect the placement of a more permanent catheter or a surgical connection between an artery and a vein (arteriovenous fistula). Catheters placed in the femoral vein need to be at least 20cm long so the tip can reach the inferior vena cava, another large vein which transports de-oxygenated blood from the lower body to the heart.
However, peritoneal dialysis catheters, which are used for a type of dialysis that uses the lining of your abdomen to filter your blood, target the space within your abdomen rather than a blood vessel. When correctly placed, they go through the front abdominal wall with the tip positioned near the visceral peritoneum (the membrane closest to your abdominal organs) and under the parietal peritoneum (the membrane attached to the abdominal wall), pointing towards your pelvis. The chosen locations for insertion are the borders of the rectus muscle (a large muscle running down the abdominal wall), keeping away from the superficial and inferior epigastric arteries (blood vessels that supply blood to the abdominal area and pelvis).
The Tenckhoff catheter, a commonly used type of peritoneal dialysis catheter, has two cuffs. The deeper of the two should be placed within the pre-peritoneal space in the rectus sheath (a strong layer of connective tissue enclosing the rectus muscle), and the superficial one should be placed 2 to 3cm inwards from the wound on the surface. If the deeper cuff is placed outside the rectus muscle, it may not integrate well with the tissue which could increase the chances of leakage and the formation of a hernia. If the cuff near the surface is placed too deeply, fluid may gather outside the cuff, leading to skin irritation and possible infection.
Why do People Need Dialysis Catheter
If a person needs to start a kidney treatment called extracorporeal Renal Replacement Therapy (RRT) urgently, a new dialysis catheter is usually needed. A dialysis catheter is a special tube inserted into your body to get dialysis, a treatment that cleans your blood when your kidneys can’t. There are two types of catheters – non-tunneled catheters for short-term use and tunneled cuffed catheters for long-term use.
For people with chronic kidney failure, a different method is preferred called arteriovenous (AV) fistula. This involves a surgical procedure to connect an artery and vein, creating a stronger vein that can handle repeated needle insertions for dialysis over a long period. However, as it takes weeks or even months for AV fistulas to be ready for use, catheters are often needed for urgent cases or when preparing an AV fistula in advance is not possible.
For peritoneal dialysis, another type of kidney treatment, a catheter is always needed. This kind of dialysis might be used when it’s hard to access the blood vessels, for patients with unstable blood pressure and poor heart function who may not tolerate the other type of dialysis well, or for children.
When a Person Should Avoid Dialysis Catheter
There are certain conditions that can make it unsafe to place extracorporeal RRT catheters, a type of tube used for blood cleansing treatment outside the body. These unsafe conditions include having an infection at the site where the catheter would be inserted, having a clot (thrombosis) or narrowing (stenosis) in the vein that the catheter would enter, having an abnormal body structure, or having a recently damaged blood vessel.
For other types of dialysis treatment involving catheters inserted into the abdominal cavity, or peritoneal dialysis, it is not safe if the lining of the patient’s abdomen or peritoneum is not normal. This may be due to recent physical injury, infection (sepsis), or a recent abdominal surgery.
Peritoneal dialysis may also not be suitable if a patient’s metabolism is severely disrupted (for example when levels of potassium in the blood are extremely high), or during severe lung distress (known as ARDS) as the fluid in the abdomen may stop the diaphragm from moving freely and make breathing difficult.
It’s currently not clear whether peritoneal dialysis or extracorporeal RRT is safer when a patient has a blood clotting disorder (coagulopathy).
Equipment used for Dialysis Catheter
Catheters for Kidney Dialysis
Dialysis is a treatment that removes waste and excess fluid from your blood when your kidneys can’t do it on their own. It’s important to use the right kind of catheter for this process.
Catheters for hemodialysis (kidney dialysis), also used for other forms of treatment like hemofiltration and ultrafiltration, are large, hollow tubes inserted into your veins. The other end of the catheter connects to the dialysis machine using color-coded connectors – one connector for taking blood (typically red) and another for delivering cleaned blood back into your body (typically blue).
Most catheters have two channels inside – one for withdrawing the blood and another for returning it. Some of these dual-lumen catheters even have a third channel, which can be useful for other tasks, like monitoring heart pressure or injecting medication.
In the old days, the returned and withdrawn blood traveled through the same channel, but modern catheters have two separate, side-by-side channels, lessening chances of cleaned blood getting sucked back into the machine – a problem known as “recirculation” which could make dialysis less effective.
There are two types of catheters: non-tunneled and tunneled catheters. Non-tunneled catheters are inserted directly through the skin into the vein. Tunneled catheters, unlike the former, pass through a small tunnel under the skin before entering your vein. They also have a cuff that’s tucked under your skin and helps in reducing infections and securing the catheter.
When placed properly, the tip of the catheter should rest in the middle of a large vein. It should not be too close to the vein wall as that can block the withdrawal channel. To get the best blood flow, the catheter has to situate just right. So, doctors take the patient’s movement and the catheter’s length into consideration, while placing it.
The following instruments are necessary for non-tunneled catheter placement:
* Local anesthetic (usually Lidocaine), with a syringe and needle
* Introducer needle (or cannula with trocar) and syringe
* Guidewire
* Skin dilator
* Silk suture
* Scalpel
* Bungs for sealing the catheter
* Heparin solution (depending on current practice)
* Sterile normal saline
* A small adhesive pad used for holding the catheter in place
If ultrasound is used to guide the catheter placement, a linear probe, sterile cover for the probe, and sterile gel are required.
Peritoneal Dialysis Catheters
Peritoneal dialysis is another type of dialysis that uses a solution called dialysate to clean and filter blood inside your body. For this, a catheter is used to carry the dialysate into and out of the peritoneal cavity in your abdomen.
These catheters have a single hollow space and are often rigid. However, for patients who need long-term dialysis or have failure in multiple organs, softer, flexible Tenckhoff catheters are the norm. Just like tunneled cuffed catheters, Tenckhoff catheters have one or two cuffs and are inserted with a special insertion device or with the Seldinger technique.
For acute intermittent peritoneal dialysis, around 2000mL of dialysate fluid (or 20-50mL/kg for a child) is instilled through the catheter for 30-60 minutes and then drained.
The following equipment is needed for Tenckhoff peritoneal dialysis placement:
* Local anesthetic, with syringe and needle
* Cannula and syringe
* Warmed sterile normal saline
* Guidewire
* Scalpel
* Sheath with introducer
* Tenckhoff catheter
Who is needed to perform Dialysis Catheter?
Having a trained helper present when putting in a catheter can be helpful, but it’s not a must-have. What’s most important is making sure the patient is in the right position, that the patient is relaxed and ready to help, and that all the equipment needed is at hand.
Preparing for Dialysis Catheter
Where possible, doctors should get the patient’s agreement for the medical procedure after explaining the benefits and risks involved. This agreement should be recorded properly in the patient’s medical history. It’s also important to get access to the patient’s veins (IV access) and start monitoring their heart activity, blood pressure, and oxygen level in the blood using ECG, blood pressure monitor, and pulse oximeter respectively.
If the patient needs a peritoneal dialysis catheter (a tube that helps clean the blood in kidney disease), they should empty their bowel and bladder before the process begins. They should then lie down flat on their back on the treatment bed.
If a catheter needs to be placed in their internal jugular (neck) or subclavian (below the collarbone) vein, the patient should lie with their head at a lower level than their feet (Trendelenburg position), and keep their head facing forward. This position is not needed for placing a catheter in the femoral vein (in the groin); in this case, the groin area should be visible.
The healthcare provider will then sterilize the insertion area with an antiseptic. The clinician will wear a hat and a face mask to stay sterile, and also keep their eyes protected. After cleaning their hands thoroughly, they will put on a sterile gown and gloves. Finally, a sterile sheet with a hole will be placed on the patient to expose only the area where the procedure will be done. This helps to prevent any infection from spreading.
How is Dialysis Catheter performed
There are two main methods for inserting catheters for different types of dialysis or similar treatments: one for inserting catheters into veins (Extracorporeal RRT) and another for inserting them into the abdomen for Peritoneal Dialysis.
In the first procedure for veins, the doctor begins by using a device called an ultrasound to accurately see beneath the skin and locate the targeted vein. After numbing the area with an anesthetic, a needle connected to a syringe is inserted slowly towards the vein. When they see blood entering the syringe, they know they’ve reached the vein. The syringe is then removed, and a guidewire is pushed gently through the needle to help guide the catheter. The needle is taken out, and a small cut is made in the skin where the wire is. The catheter thread is then guided along the wire until it’s at the right depth. Lastly, the wire is removed, and the catheter is secured and covered.
In the second procedure, the Peritoneal Dialysis, a local anesthetic is injected at the chosen site on the abdomen. Once the area is numb, a small incision or cut is made. A needle is then passed through the abdominal muscle, stopping when there’s a loss of resistance indicating the needle has entered the peritoneal space, a part within the abdomen. Fluid is then added to this space creating a path for the catheter. The catheter is then slowly put in through the sheath and removed when the catheter’s cuff is in the right place. More anesthetic is added to the midline wound and a small cut is made at this site. The catheter is passed back through the tunnel and sutured to the skin.
For both procedures, it is very important to ensure the catheter is in the right location and flowing properly for the treatment to be effective.
Possible Complications of Dialysis Catheter
Just like other central venous lines that aid in the transportation of medications and fluids, catheters used for extracorporeal RRT (a procedure that helps the kidney function properly) can also have complications. These complications can include health-threatening blood clotting and infection, injury to nearby areas like the pleura (the lining of the lungs), or arteries. Complications can also include narrowing of the central veins and device failure, resulting in lower blood flow rates and a reduction in the patient’s survival time.
These catheters can stop functioning properly due to many factors. For instance, if the catheter is not correctly placed (like if it’s twisted where it enters the vein, or poorly positioned inside the blood vessel, or if the chosen blood vessel is too narrow for the catheter), the blood might accumulate and clot. This can lead to the formation of a fibrin sheath (protein layer) around the catheter, making it less effective.
But there are various surgical techniques to fix these complications and restore the normal flow and functionality of these catheters. Sometimes, it means replacing the existing catheter for a new one or surgically cleaning up the protein layer that has formed around the device. In the worst-case scenario, the catheter might need to be temporarily removed, the fibrin sheath can be cleared, and then a new catheter can be inserted.
With catheters used for peritoneal dialysis (a treatment to clean the blood of toxins when kidneys aren’t working properly), complications can be due to misplacement of the needle which inserts dialysate (cleaning solution) into the abdomen. This error can cause the fluid to enter the bowel or bladder, leading to sudden diarrhea or a sharp increase in urine production. During this process, if there’s damage resulting in a bowel perforation, which occurs in roughly 1% of cases, the patient could notice fecal matter or significant amounts of blood in the discharge fluid.
Additionally, the cutaneous wound (wound on the skin) can be infected. This is seen less often in the early stages, but peritonitis (an abdominal infection) may occur later which might need treatment with antibiotics, dialysis discontinuation, and switching the patient to extracorporeal RRT (blood cleaning performed outside the body). With time, these catheters can become obstructed due to misposition, twisting, adhesions, clots, or the build-up of a fibrin sheath. In this case, irrigation with saline or urokinase (a drug that helps dissolve blood clots), or re-alignment of the catheter could restore the flow.
At times, fluid might leak through the wound on the skin. This is seen more with rigid catheters than tunneled Tenckhoff catheters (those placed under the skin). If the problem persists, laparoscopy or omentectomy (a procedure to remove the omentum, a large fatty structure in the abdomen) could be needed.
What Else Should I Know About Dialysis Catheter?
If you have chronic kidney disease, you might need a special tube, called a catheter, that helps clean your blood through a process called dialysis. This tube can stay in your body for several months, and it’s important to keep it clean and well-maintained to avoid any complications.
Many of these catheters are made from a material called polyurethane. This is a type of plastic that gets softer at body temperature, while still being strong and sturdy. However, certain substances can weaken this material, including alcohol, most antibiotics (except for a particular cream called triple antibiotic ointment), and an ingredient found in many creams called polyethylene glycol.
Some newer catheters are made from a material called silicone. This is softer and more flexible than polyurethane and therefore, has thicker walls to prevent it from bending or collapsing. Silicone is compatible with creams but can be weakened by exposure to iodine, a disinfectant often used for cleaning.
Therefore, it’s crucial to know which substances are safe to use for cleaning your catheter and to follow the recommended care instructions.