An 82 year old male presents with abdominal pain and a rash
A 60 year old man with a history of shingles presents with a flare up of his post herpetic neuralgia pain. At home he has been using gabapentin , tylenol, ibuprofen and has had little relief. You try some parenteral medications in the emergency department and he has some modest improvement in his symptoms but he still feels uncomfortable . He mainly just wants to feel comfortable enough to go home and get some sleep.
The TAP block is an excellent option for patient’s presenting with pain from postherpetic neuralgia. It offers largely cutaneous effects so it is useful for ED pathologies like abscesses and lacerations. While it is theorized to provide maximal benefit for cutaneous pathologies, it has been shown to help with visceral pain from pathologies such as appendicitis and chronic pancreatitis.
The TAP block will provide analgesia along the T7 to L1 dermatomes on the ipsilateral side that the block is performed on. For example if someone has an abscess on the right side, you would do a right sided TAP block. If that largely right sided abscess crossed the midline, the part of the abscess to the left of midline would not get anesthetized.
Abdominal dermatome map-taken from emdocs.net
To perform the block, you will need approximately 30 cc of the long acting anesthetic of your choice, a 27 g needle and 1-2 cc of a short acting anesthetic for a skin wheel, a 20 G spinal needle, 2% chlorhexadine, and an ultrasound machine with a linear probe. As with any large volume block, you need to ensure that you remain below the toxic dose of the anesthetic. Consider even further dose reduction in elderly patient and those with renal dysfunction.
For a right sided, TAP block have the patient lie in the left lateral decubitus position. Palpate the landmarks of the inferior costal margin and iliac crest. Then place your probe midway between those two landmarks along the midaxillary line
Surface landmarks and rough position of probe. This provider is electing to do the block with the patient supine as opposed to in the decubitus position. I personally find supine positioning more difficult as it is harder to anchor the probe, but whatever floats your boat. Images taken from emdocs.net and highlandultrasound.com
Once you have positined your patient you can identify the relevant anatomy. The TAP block is a plane block. So similar to the Fascia Iliaca block, you are injecting a high volume of medication in a fascial plane and relying on the medicaiton to diffuse and bathe the target nerves.
On ultrasound from superficial to deep you should see some adipose tissue, external oblique, internal oblique, transverse abdominus, and then the peritoneum. Your target is the bright white line between the internal oblique and transverse abdominus.
The blue line is your target. Deep to the transverse abdominus you can see the border of the peritoneum. Dont hit that.
Once you have identified your target, numb the skin up and use in plane guidance to guide yourself down to the target.
You want to kind of “split” the fascia with your anesthetic
I know what you’re thinking-why would i get anywhere near the peritoneum? Well you usually have half a cm or more of vertical distance between your target and the peritoneum. Assuming a 30 degree angle of needle entry, you’d have to advance your needle a whole centimeter of length beyond the target before you’d even be getting close to the peritoneum. So assuming you are doing a good job of visualizing your needle the entire time, you have to really mess up to violate the peritoneum. It sounds scary, but trust me its fairly easy and the ultrasound anatomy is super easy to see.
Case resolution: You monitor your patient for LAST for 30 mins on the cardiac monitor and then go in to check on his pain. He states his pain is largely resolved and requests that you discharge home so he can go home and sleep.