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Monday, June 2, 2014

What is a "Spinal Anesthetic" for Surgery? Shown and Explained with Color MRI Images!

Spinal Anesthetics are commonly used as a form of Anesthesia for Surgery. The other common forms of Anesthesia are "General Anesthetics", "MAC Anesthetics", and "Local Anesthetics".

In a Spinal Anesthetic, Local Anesthetic medications are injected directly into the Spinal Fluid to anesthetize specific Spinal Nerves which are bathed by the Spinal Fluid. This results in a "numb area" of the part of the Body where Surgery is planned. For a General Anesthetic, medications are injected through an IV (intravenous line) to put a patient to sleep completely (unconscious). After that, a breathing machine (ventilator) will breathe for the patient. In a Spinal Anesthetic, patient usually do receive relaxing medications through an IV, however not for the purpose of putting the patient to sleep completely. A "MAC Anesthetic" (Monitored Anesthesia Care) relies on relaxing medications which are also injected through an IV. However in a MAC Anesthetic, patients may be unconscious, but continue to breathe on their own. A "Local Anesthetic" means that anesthetic medication is injected under the Skin to anesthetize a specific area of the Body.

Lets first take a look at the Anatomy of the Spine to better understand how a Spinal Anesthetic works. This Color MRI Image shows you all the main parts of the Low Back (Lumbar Spine). It may help to focus on the Spinal Nerves and the Spinal Fluid, since this is where the Spinal Anesthetic is given. This is an Interactive Image. As you move your mouse cursor over the Image, Interactive Image Tags appear. Each Tag displays text which explains a specific part of the Image.


Sagittal Lumbar Spine Anatomy Color MRI Image
Interactive Color MRI of the Low Back (Lumbar Spine) showing the Anatomy from a side-view slice

The next Color MRI Image shows you the same Anatomy, but from a different perspective. This is a slice across the Low Back (Lumbar Spine). If you combine the Image above and below, you can get a 3-dimensional sense of the Anatomy. This Image is also Interactive. Just move your mouse cursor over the Image to learn.


Axial Lumbar Spine Color MRI Image of the Lumbar Spine Anatomy
Interactive Color MRI of the Low Back showing the Anatomy as a slice across the Spine


Now that we have looked at the Anatomy, lets talk more about how a Spinal Anesthetic is done and how it works. The Anesthetist usually gives the patient a choice of a Spinal Anesthetic if they believe it is a good option for the type of planned Surgery. Spinal Anesthetics are usually only an option for Surgery below the bottom of our Breast Bone (abdomen, pelvis, rectum, legs, feet, etc.).
If a Spinal is an option, the Anesthetist typically informs the patient about "Risks and Benefits" of the Spinal compared to other Anesthetics (General, MAC, Local). The main risks are twofold: 1. The Spinal may not be an adequate Anesthetic for the Surgery, in which case a General Anesthetic may have to be given. 2. A patient receiving a Spinal Anesthetic may get a "Spinal Headache" afterwards. This type of headache results for the small hole the Spinal Needle leaves in the lining of the Spinal Fluid (dura). This small hole sometimes allow Spinal Fluid to leak which can result in a headache and nausea amongst other symptoms. Other risks to exist (bleeding, infection, etc.) but are less common.

The first step in performing a Spinal is for the patient to sit up or lie on their side and bend forward or curl up. This position separates the Vertebrae in the back and creates a larger opening for the Spinal Needle. After the skin is anesthetized, a Spinal Needle is placed through the Skin and advanced deeper through the Spinal Ligaments. Once the Needle has passed through these Ligaments, it will encounter the Spinal Fluid. This fluid is the target of the Spinal Anesthetic.

Lets look at a Color MRI Image of the Low Back (Lumbar Spine) to show you where the Spinal Needle is placed. This Image is also Interactive. The Interactive Tags explain the important parts of the Spine Image.
 
Sagittal Lumbar Spine Color MRI Spinal Needle Placement
Interactive Color MRI of the Low Back (Lumbar Spine) showing a Spinal Needle placed into the Spinal Fluid

Here is a Color MRI Image showing the placement of the Spinal Needle from a slice across the Spine view. This Image is also Interactive. The Interactive Tags explain the important parts of the Spine Image.

Axial Lumbar Spine Color MRI Spinal Needle Placement
Interactive Color MRI of the Low Back (Lumbar Spine) showing the Spinal Needle Placement in cross-section

After the Spinal Needle is placed in the Spinal Fluid, anesthetic medication can be injected. The type of medication often depends on the type and length of Surgery. The amount of medication typically depends on the patient size and the length of Surgery. A commonly used Anesthetic is Bupivacaine (Marcaine). Sometimes, narcotic pain medications are added to the Anesthetic. Spinal Anesthetics can last for hours, depending on the type and amount of Anesthetic injected.

Here is a Color MRI Image showing the spread of the injected medication. Notice how the medication travels within the Spinal Fluid. The Spinal Nerves are bathed by the Spinal Fluid. This is how the Spinal Nerves receive the medication. This Image is also Interactive.



Sagittal Lumbar Spine Anatomy Color MRI Spinal Injection
Interactive Color MRI of the Low Back (Lumbar Spine) showing the injected medication from a side-view
The next Image shows the Spinal Injection as a slice across the Spine (cross-section). This Image is also Interactive.


Axial Lumbar Spine Color MRI Spinal Anesthesia Injection
Interactive Color MRI of the Low Back (Lumbar Spine) showing the injected medication in cross-section

The Color MRI Image below shows you the parts of the Body which can be anesthetized by the Spinal Anesthetic. The green area are the anesthetized areas.


Whole Body Color MRI Spinal Anesthetic Effects
Whole Body Color MRI showing the effects of a Spinal Anesthetic on the Body

Spinal Anesthetics are generally safe and effective. However, they are the patients choice of Anesthetic. Some patients do not like the idea of having a Spinal Injection for fear of having back pain afterwards. Others do not like the idea of having a feeling of paralysis in their abdomen and legs during Surgery and a period if time afterwards. It is important to discuss all the pros and cons of the Anesthetic with the Anesthetist.

If you liked this Blog, here are some related recent Blogs from MMI:
What is an Epidural Injection? Shown and explained with Color MRI Images
What is a Spinal Discogram Injection? Shown and Explained with Color MRI Images
What is Sciatica? Shown and Explained with Color X-Ray and Color MRI Images
Spinal Stenosis of the Low Back (Lumbar Spine) shown and explained with Color MRI Images
Disc Herniations of the Low Back (Lumbar Spine) shown and explained with Color MRI Images


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