Colonoscopy / Sigmoidoscopy

Anesthesia Implications

Position: Left Lateral, Right Lateral, arms free at side
Time: 5-30 min (very short)
Blood Loss: Zero
Post-op Pain: Minimal (1-3)
Maintenance Paralytic: No

Approach – These procedures are almost always done with sedation only. In most cases, a 22 gauge IV will be sufficient. Preoperative medications (typically 2 mg of versed) are sometimes given prior to the procedure. The patient is given a bolus of sedative medication (typically propofol ~ 50-100 mg) to induce sedation. Many providers use the ETCO2 monitor to assess breathing (chest rise and fall should be the primary assessment).

Dehydration – The patients require bowel prep, which leaves the patient dehydrated.

Vagal Response – Make sure to have Robinul or atropine available to treat a possible vagal response that occasionally manifest when the scope is advanced and/or the colon is inflated.

From the Pros – When the endoscopist is withdrawing the scope, it is helpful to give a small bolus of propofol prior to reaching the sigmoid and rectum. This area is more stimulating to the patient. Retroflexion of the scope is usually performed to view the interior of the anus just prior to removal of the scope. This may cause a lightly sedated patient to feel as if they are having a bowel movement.
Give midazolam and ketamine to higher risk patients without significant cardiac disease (i.e. those who are obese & can’t tolerate large amounts of propofol without obstructing). Pretreat with glycopyrrolate to counter the increased secretions secondary to the ketamine. It works like a dream and keeps the propofol requirements significantly lower!

Lateral position (general considerations): If an ETT has been placed, make sure ETT is secure with extra tape.  Unhook anesthesia circuit while turning lateral and be especially careful to keep patient’s head neutral and aligned with body to avoid neck injury. Once lateral, use pillows/blankets/foam headrest to keep the patient’s head in neutral position. The most common nerve injury for orthopedic lateral procedures are neurapraxias of the brachial plexus. These are motor and/or sensory loss for 6-8 weeks due to pressure on the contralateral (dependent) axilla. To prevent this, place an axillary roll under the patient (caudad to the axilla, on the rib cage, and NOT in the axilla). Check routinely to make sure the axillary roll does not migrate into the axilla. If the non-dependent arm is placed on a board, check padding and reposition regularly to avoid radial nerve compression. If a bean bag is employed, check the hard edges to ensure that unnecessary pressure isn’t being put on soft tissues. Pad all dependent bony prominences such as the fibular head (to prevent peroneal nerve injury), and place pillows between the knees and ankles (to prevent saphenous nerve injury). If anterior hip supports are in place, ensure they are properly padded or neuropraxias and/or occlusions of large blood vessels may result.

The surgery is done to screen for colon cancer. This is a recommended as a yearly procedure for anyone greater than 50 years of age. Also recommended for anyone that has first-degree relatives with a history of colorectal cancer or polyps.

A colonoscope is a flexible tube which ranges from 4-6 feet long. This is lubricated and inserted into the anus. Advancement is made slowly while visualizing the structures of the GI tract all the way to the cecum. Air is used to expand the colon, which gives better visualization. Occasionally, an assistant will press at various points on the abdomen which gives the physician better visualization. This can be very stimulating and may require additional doses of sedative medication to be given to the patient.