What is a TAP block?
A TAP or transversus abdominis plane block numbs the abdominal muscles and skin in preparation for surgery.
A transversus abdominis plane (TAP) block is a procedure to anesthetize the nerves that provide sensation and muscle function to the abdominal wall and skin. For a transversus abdominis plane (TAP) block, an anesthetic injection is administered in the area between the internal oblique and transversus abdominis muscles in the stomach wall.
The stomach wall is composed of five pairs of muscles. Two pairs of muscles, the rectus abdominis and the pyramidalis run vertically over the abdomen on either side of the vertical abdominal midline (linea alba). The remaining are flat muscles that form three layers of muscles on either side of the linea alba.
The three pairs of flat muscle layers are
- External oblique (outermost)
- Internal oblique (intermediate)
- Transversus abdominis (innermost)
The abdominal wall nerves pass through the connective tissue (fascia) between the internal oblique and transversus abdominis muscles. An anesthetic solution injected in this region blocks these nerves from sending pain signals from the abdominal wall to the brain.
Why is a TAP block performed?
A TAP block reduces the use of post-surgical opioids and their related side effects such as nausea and vomiting. A TAP block provides more effective post-surgical pain relief (analgesia) for a longer period than general anesthesia alone.
A TAP block is usually performed for analgesia after open or laparoscopic abdominal surgeries such as
- Bowel resection
- Caesarean delivery
- Hysterectomy
- Appendectomy
- Cholecystectomy
- Hernia repair
- Prostatectomy
- Nephrectomy
A TAP block can be performed
- Before, during or after an abdominal surgery to control pain caused by the incision
- When epidural analgesia is not possible
- With insertion of a catheter, to provide continuous analgesia for longer periods
A TAP block is not performed in the presence of
- Infection at the injection site
- Allergy to local anesthetics
How is a TAP block performed?
A TAP block is usually administered to control post-operative pain before the withdrawal of anesthesia. The injection may be administered in the waist above the pelvic bone or/and in the upper abdomen just below the ribs, depending on the requirement.
Analgesia for the entire stomach wall can be achieved by two injections each on either side of the abdomen. Bupivacaine is the commonly used anesthetic agent.
Preparation
- The patient lies flat on their back.
- The patient’s blood pressure, heart rate and oxygen saturation are checked.
Procedure
The doctor
- Identifies the lumbar triangle of Petit, which is a small anatomical triangle in the waist, in line with the armpit.
- The triangle of Petit is formed by the top of the pelvic bone (iliac crest) and the edges of the external oblique and back muscles (latissimus dorsi).
- Inserts the needle perpendicularly in the skin just above the iliac crest.
- Advances the needle through the external and internal oblique muscles till the needle tip reaches the space above the transversus abdominis muscle.
- May use ultrasound guidance to insert and advance the needle towards the transversus abdominis muscle
- In the upper abdomen below the ribs, or
- In the triangle of Petit in the waist
- Aspirates the needle to make certain it is not inside a blood vessel.
- Slowly injects the anesthetic solution and withdraws the needle.
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How long does a TAP block last?
A TAP block is usually done before surgical anesthesia wears off and takes about 20 minutes to become effective. The analgesic effects typically last up to 24 hours. The TAP block provides analgesia from the incisional pain in the stomach wall but does not block any pain in the internal organs in the abdomen.
What are the risks and complications of a TAP block?
A TAP block is a relatively safe procedure and complications are uncommon. Potential complications include:
- Infection at the injection site
- Bruising and bleeding
- Injury to nerves or blood vessels
- Local anesthetic systemic toxicity
- Allergic reaction to the local anesthetic
- Accidental puncture of the abdominal membrane (peritoneum)
- Hematoma in the intestine
- Liver laceration
- Injury to other organs such as spleen or kidney
- Transient femoral nerve palsy with symptoms of temporary weakness in the thighs, due to the anesthetic pooling close to the femoral nerve