RMV->) Your biggest patients might also be your biggest colonoscopy challenges. We once had to tie two stretchers together to scope a 500-plus-pound patient. Even then, all that weight pressing on his abdomen and his short neck made for a tense time. We had the Ambu bag ready, just in case.

Whether it's the obese patient with a compromised airway; the frail, elderly patient at risk for bleeding and perforations; or the patient whose NPO status changes depending on who's doing the asking, colonoscopy can go from routine to red alert in an instant. And this is to say nothing of anesthesia complications or malfunctioning equipment.

Looking back over my decade of experience in the endo suite, here are some suggestions and tips every nurse should be aware of. As you'll see, prevention is the key to an uneventful colonoscopy. There's plenty we can do to minimize problems.

1 Start with a good physical assessment.
There's much you can detect by physically assessing the patient and reviewing his history and physical, including his weight, allergies, current medications, medical history and surgical history. Some examples:

• Patients with recessed jaws or short necks are more likely to have their tongues fall back and occlude their airways during the procedure. You may want to do a chin lift on these patients.
• Perforations are more likely to occur in patients with moderate to severe diverticulosis because the lining of the bowel wall will be weakened.
• An obese patient may require proactive treatment to prevent aspiration and proper positioning to maintain the airway. For some anesthesia providers, the answer might be to raise the head 30 degrees; others like to keep the patient's head flat. If you're using abdominal splinting on an obese patient, chances may be greater that he'll regurgitate. You can decrease the potential complications of aspiration by putting the patient in a slight Trendelenburg position, which will facilitate drainage and maintain the airway. Bottom line: Have suction ready underneath your pillow if you think aspiration is likely. And remember that all sedated patients are at risk for aspiration.
• Patients who've had multiple abdominal surgeries can be especially challenging. The endoscopist may likely have a harder time navigating through the five- to six-foot long colon of a patient with the presence of scar tissue affording less pliability within his bowel. You may find that abdominal splinting will facilitate scope movement in these patients.
• You'll want to assess patients on blood-thinners (anticoagulants) or NSAIDs to determine when they've stopped taking these medications. Often at the discretion of the physician, patients are instructed to eliminate these medications for three to five days before the procedure, especially if they have a history of polyps where biopsy or polyp removal is more likely.

2 Assess every patient for NPO status.
Patients NPO for less than six hours are at higher risk for aspiration. You can never ask a patient too many times about his NPO status - double- and triple-check and you'll see that the glass of water turns into two and that nothing to eat turns into a hot dog consumed one hour ago. Keep in mind that patients may not be totally truthful with the nurse, but may feel the need to confess as soon as the anesthesia provider walks behind the curtain.

3 Keep your pulse oximeter on.
Propofol depresses the central nervous system and may decrease patients' respiratory and cough centers. Maintain good ventilation and keep your pulse oximeter on. It will alert you when something is wrong and allows for early intervention if the patient's oxygen saturation begins to fall below acceptable levels (see "If You're Thinking of Buying ' A Pulse Oximeter" on page 84). It's always a good idea to pre-oxygenate patients before the procedure via nasal cannula, especially smokers and patients with compromised respiratory status. Getting the oxygen level up before you sedate really makes a significant difference. Be careful not to over oxygenate COPD patients.

4 When the procedure's done.
The case is over. All went well. The patient is emerging from sedation. Where's your focus? Likely on the screens and scopes, when it should still be on the patient as he emerges. Make sure the patient is breathing normally. As you know, patients can experience hypoventilation due to medications or laryngospasm at any time.

5 Check your equipment.
Before the patient enters the room, all equipment should be set up, turned on and checked - from top to bottom. It's a long list, but you're going to significantly reduce problems in the long run.

• Check that the monitor is working and programmed.
• Is the printer paper in?
• Is your water canister fully connected to the scope?
• Have you white balanced?
• Is suction working properly?
• Are all accessories available at your fingertips: biopsy forceps, snares and disposable surgical clips for bleeding?
• Is your cautery plugged in and properly set?
• Are the air/water/suction functions on your scope head working properly?

6 When things go wrong.
So far, we've talked about preventing problems before they occur. Now we're going to touch on what to do when things go wrong, as they inevitably will.

• Equipment. Scopes were made to be broken. The scope lens can cloud. The scope channels can clog. Light sources can go out. Your bending rubber can develop leaks. Cables in scopes can break. The suction can fail. And anything can go wrong with fiber optics at any time.

Not long ago, we couldn't connect the water bottle to the scope. The problem? One of the scope's fittings that plugged into the light source was off maybe an eighth of an inch, enough that we couldn't get the water bottle connected. I wouldn't want my equipment rep to hear this, but we needed to fix it then and there, so I pulled out a pair of pliers and tweaked (ever so gingerly) the fitting just a hair. And it fit. Most equipment problems, however, will require you to send the scope out for repair.

• Bleeding. If you're removing a large, broad-based polyp, the potential for bleeding is much higher. Two things to do when this happens. First, make sure your Bovie settings are correct and to close your snare slowly. Your physician may ask you to readjust your cautery setting. Sometimes a lower setting and slower technique is the key to control the bleeding during polypectomy. Second, the physician may want to consider sclerotherapy. The doctor will deliver an injection of epinephrine to halt bleeding, which constricts blood flow to bleeding vessels.
• Perforations. The endoscopist is performing an uneventful procedure, examining a colon that's pretty, pink and healthy. All of a sudden, the screen turns white or yellow. What's that? Something's not right. Within seconds, you know or suspect you've perforated the wall. Rule No. 1: Don't panic. Conclude the procedure as quickly as possible. Monitor vital signs and assess continuously for signs and symptoms of shock. Check the abdomen for distention and bowel sounds. Maintain IV fluids. Make arrangements for transfer to a hospital for surgery. Facilitate communication with the physician, family, patient and hospital/transport caregivers.

In the case of suspected microperforation, typically the patient may run a fever after an uneventful colonoscopy 24 to 48 hours post-procedure. You may discover this on your follow-up call. The physician may choose to treat the patient with oral antibiotics prophylactically and send him for an X-ray.