Patient Preparation and Pharmacotherapeutic Considerations

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Chapter 8 Patient Preparation and Pharmacotherapeutic Considerations

Chapter Outline

General Information about Patient Preparation

Numerous aspects must be considered when preparing patients for endoscopic examinations, including the following:

The endoscopist must have knowledge of the indication for the procedure because this determines not only what procedure is performed but also what interventions or treatment might be required during the procedure. Implicit also is an understanding of the patient’s clinical history and the results of any recent investigations. The preprocedure assessment must extend to the patient’s past medical and surgical history, previous endoscopy results, current medical therapy (including over-the-counter and intermittent medications), and drug allergies. Specific clinical history such as diabetes, a personal or family history of bleeding disorder, anesthetic reactions, or previous adverse reactions to other medical interventions (including reactions to radiologic contrast agents) should also be considered. Armed with this information, the endoscopist is able to determine the proper preparation and any specific modifications that might be required for the individual patient (see Chapter 7).

After the procedure preparation, risks, and potential complications have been discussed, the next phase of the explanatory process is to discuss discharge guidelines. Most endoscopic examinations are performed as day procedures, and frequently patient sedation is administered. Most institutions require that sedated patients are discharged in the care of a responsible person who not only can supervise transportation of the patient home but who also is able to respond to any delayed complications or difficulties. The level of postprocedure supervision depends on the type of intervention and sedation, specific patient factors such as mobility and age, and such things as geographic isolation. These issues must be brought to the patient’s attention before the procedure so that proper planning can occur. Difficulties with discharge arrangements should always be resolved before the endoscopic procedure and never left to be discussed after the procedure has been performed. Although the previous process may seem cumbersome, there are significant advantages for the patient and the endoscopist, such as the following:

Preparation for Endoscopy and Enteroscopy

Patients should not eat solid food for 6 hours or drink fluids for at least 4 hours before an elective endoscopy.1 If a delay in gastric emptying is known or suspected, longer fasting or a period of a fluid-only diet should be considered. Many centers use prokinetic agents to speed gastric emptying in patients when fasting time is inadequate (see subsequent section on special circumstances). In situations in which there is a delay in gastric emptying or in which there is inadequate fasting time, there is a significant risk of pulmonary aspiration, and airway protection with airway intubation should be considered. Normally, it is acceptable for patients to take their usual medicines with a sip of water before endoscopy. Special consideration must be given to patients taking anticoagulant medication or medication to treat diabetes (see separate section).

No data support routine blood tests before diagnostic endoscopy, and screening tests are not required. If a bleeding disorder is suspected or known, tests to evaluate this and direct therapy are indicated. Similarly, if the patient’s clinical condition is unstable or indicates that an abnormality in the blood tests is likely to be present, appropriate testing and correction of relevant abnormalities is indicated. Preparation for antegrade enteroscopy is the same as described earlier. If retrograde enteroscopy is to be performed, preparation requirements are the same as for colonoscopy.

Preparation for Endoscopic Retrograde Cholangiopancreatography

The preparation of patients for endoscopic retrograde cholangiopancreatography (ERCP) is similar to the preparation for endoscopy.1 Generally, patients undergoing ERCP almost always require sedation, and the duration of the procedure is longer; this should be taken into account for purposes of discharge planning. Patients with suspected or proven biliary or pancreatic duct obstruction generally are given prophylactic intravenous antibiotics if there is a clinical suspicion of inadequate duct drainage. Antibiotics may also be given in patients with sclerosing cholangitis and in patients after liver transplantation. Before ERCP, it is important to determine if the patient has a known history of reaction to iodinated contrast agents. Although reaction to the contrast agent in allergic patients during ERCP is rare, it is generally considered appropriate to administer prophylactic steroids, often in combination with an intravenous antihistamine agent. In severe cases, enlisting support of an anesthetist in case of a reaction is a prudent precaution. The use of a noniodinated contrast agent is an alternative strategy.

Because ERCP is performed with radiologic imaging of the abdomen, patients who have had recent barium studies or other oral contrast agents should be checked to ensure that the field of view is clear for the ERCP to be successfully completed. If there is residual contrast material in the gut, a formal bowel preparation may be required. Women of childbearing age must be asked if they are pregnant. If there is uncertainty, the ERCP may need to be deferred until a pregnancy test can be done. If ERCP is considered necessary in a pregnant woman, appropriate lead shielding of the lower abdomen is recommended to protect the fetus. Similarly, pelvic shielding is appropriate for any premenopausal woman.

No data support routine blood tests before diagnostic ERCP, and screening tests are generally not required. If a bleeding disorder is suspected or known, tests to evaluate this and direct therapy are indicated. Similarly, if the patient’s clinical condition is unstable or indicates that an abnormality in the blood tests is likely to be present, appropriate testing and correction of relevant abnormalities is indicated. In patients presenting for ERCP with a history or signs of biliary obstruction, the possibility of disordered coagulation exists. Correction of this type of abnormality before the procedure is appropriate.

Preparation for Colonoscopy

Of all endoscopic procedures, the quality of the preparation before colonoscopy has the greatest effect on the outcome of the procedure.1 The preparation is often regarded as the most unpleasant part of colonoscopy, and many patients are more concerned about this aspect than having the procedure performed. It is vital that the patient be given detailed verbal and written instructions to complete the preparation safely. If the correct preparation is not followed, the procedure usually has to be deferred. The American Society for Gastrointestinal Endoscopy (ASGE) published a technology status evaluation report on colonoscopy preparation that reviews the various bowel preparations in detail.2 Good bowel preparation is essential to provide an optimal view for colonic examination and to minimize the risk of colonic trauma during the procedure resulting from poor view.

To determine the correct preparation, the clinician requires a careful patient assessment to determine which bowel cleansing agent should be used and what modifications to the patient’s diet and regular medications are required. The addition of simethicone to the bowel preparation does not improve cleansing but does reduce bubbles, which may improve the endoscopic view.3 As part of the preparation, most patients are advised to have only a clear liquid diet for 24 hours before the examination.1 Routine blood testing before colonoscopy is not required. Management of patients taking antiplatelet and anticoagulation medications should be carefully considered before the examination to minimize the risk of procedure-related bleeding (see later guidelines). In addition, any medication that might be associated with constipation should be temporarily stopped to facilitate the bowel cleansing process. In particular, oral iron can make the stool black and viscous, and iron should be stopped at least 5 days before the colonoscopy.1 Lastly, specific instructions should be given to diabetic patients who are taking oral hypoglycemic medications or insulin to avoid periprocedural hypoglycemia.

Intravenous sedation is administered to most patients who undergo colonoscopy. It is necessary for the patient to fast before the procedure to reduce the potential for aspiration. The duration of fasting can be comparatively brief because the patient will have been on clear fluids only for 24 hours before the procedure while undergoing bowel preparation. A fasting time of 2 to 4 hours is generally considered adequate.

There are many independent predictors for a potential inadequate bowel preparation, such as a late colonoscopy start time; failure to follow preparation instructions; inpatient status; procedural indication of constipation; use of drugs that impair gut motility (e.g., tricyclic antidepressants, calcium channel blockers, iron); male gender; and a history of cirrhosis, stroke, dementia, obesity, or diabetes mellitus.47 A prior history of failed colonoscopy preparation is also highly predictive of a failed second or subsequent attempt at preparation.8 In these various patient groups, a more prolonged bowel preparation may be required. Many studies have shown an improved effect of the preparation if half is given the day before the procedure and half is given on the day of the examination. This approach also improves patient adherence and tolerance and is a useful strategy if difficulties with the preparation are anticipated. Other options include abstinence from dietary fat for 1 week and a morning procedure time. In patients who develop nausea, vomiting, or excessive bloating and patients who do not tolerate the preparation, one of the following measures can be used:

Currently, the three widely accepted bowel preparations for colonoscopy are polyethylene glycol (PEG)–based solutions, sodium phosphate–based solutions, and sulfate-based preparations. Stimulant and hyperosmotic laxatives, such as castor oil, senna, mannitol, sorbitol, and lactulose, are no longer used because they are ineffective. Nonabsorbable sugars may be metabolized by colonic bacteria, generating hydrogen, and carry the risk of explosion during electrosurgical procedures.9

Polyethylene Glycol–Based Preparations

Golytely, developed in 1980, was the first osmotically balanced electrolyte purge solution. Since then, several modifications of the solution have been made to improve tolerability. An oral purge using 4 L of a PEG-based solution, given the day before colonoscopy at the rate of approximately 1 L/hr, is associated with a good cleansing efficacy and reasonable patient tolerance.1012 Adding a flavor to the preparation is often preferred by patients. Approximately 19% of patients are unable to complete the preparation because of its large volume and unpalatable taste.13 Newer PEG-based solutions such as MoviPrep (supplied by Norgine in Europe and Australia and Salix Pharmaceuticals in the United States) are better tolerated because the ingested volume has been reduced (2 L), and the taste has been significantly improved.14 The efficacy of the lower volume preparation is similar to the standard 4-L products, and the side-effect profile is similar. Metoclopramide may be helpful in selected patients to decrease nausea and vomiting, although routine use of metoclopramide did not confer any significant benefit in a small, randomized trial.15 PEG-based oral lavage (or any form of bowel preparation) is contraindicated in patients with an ileus, significant gastric retention, suspected or established mechanical bowel obstruction, severe colitis, or neurologic impairment that prevents safe swallowing.1 For patients with swallowing difficulties, a nasogastric tube can be used to administer the solution.

Sodium Phosphate–Based Preparations

The sodium phosphate–based bowel preparation is a smaller volume and can be safely given to most healthy individuals. Traditionally, sodium phosphate preparations have been available in liquid form, but more recently Diacol (Pharmatel Fresenius Kabi, Australia, and Dr Falk Pharma, Europe) and Visicol and OsmoPrep (Salix Pharmaceuticals, United States) have been released with sodium phosphate in a tablet form. Less taste than the liquid formulations may improve tolerance, and efficacy seems comparable. Sodium phosphate preparations are administered in split doses before colonoscopy with the exact timing depending on the time that the colonoscopy is to be performed. The preparation acts by exerting a hyperosmotic effect and by indirectly stimulating stretch receptors to increase peristalsis.13 Sodium phosphate–based preparations have been shown to be superior in tolerance and at least as effective as PEG-based preparation.13,1619

Because of its rapid osmotic effect and the possibility of significant hyperphosphatemia, it is recommended that sodium phosphate–based bowel preparation be avoided in patients sensitive to sudden volume shifts, such as patients with congestive heart failure and renal impairment. Caution is also required in patients with the potential for disordered sodium or phosphate balance, such as patients with decompensated cirrhosis, small or large bowel dysmotility, and other preexisting electrolyte imbalances.1,16,17,19 In addition, this preparation is not recommended in patients with proven or suspected inflammatory bowel disease because it can cause colonic inflammation and aphthous ulceration in 25% of cases compared with 2% to 3% in PEG-prepared patients.20 Patients in whom this preparation is prescribed must be advised to drink as much clear fluids as can be tolerated to reduce the risk of dehydration and to facilitate the cleansing effect of the medication. For this reason, it has been suggested that sodium phosphate–based preparations are inappropriate for elderly patients, but Thomson and coworkers21 found that this preparation was safe, effective, and well tolerated in most elderly patients (mean age 72 years). Caution is nonetheless advised because a more recent study has shown sodium phosphate–based solutions are associated with a decline in glomerular filtration rate in elderly patients with creatinine levels in the normal range.22

Preparation for Flexible Sigmoidoscopy

Preparation before flexible sigmoidoscopy generally requires cleansing of only the left colon.1 In most cases, this cleansing can be achieved by administering one or two enemas 1 hour before the procedure. Several types of enemas are available:

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