Can a bowel preparation exacerbate heart failure?
ABSTRACTPolyethylene glycol solutions, used for bowel preparation before colonoscopy, in theory pass through the colon without any absorption of water. However, several investigators have reported that these solutions do increase plasma volume. This review compares polyethylene and sodium phosphate bowel preparations and their effects on patients with heart failure, and also offers recommendations for patients with heart failure who need colonoscopy.
KEY POINTS
- Hyperosmotic sodium phosphate preparations can cause significant volume contraction in vulnerable patients, along with a risk of hyperphosphatemia.
- Low-volume (2-L) polyethylene glycol preparations are more tolerable than 4-L solutions.
- Although increases in plasma volume can be detected with polyethylene glycol solutions, these solutions are still the safest choice in patients with heart failure.
SODIUM PHOSPHATE PREPARATIONS CAN CAUSE FLUID DEPLETION
Aqueous sodium phosphate preparations such as Fleet are low-volume hyperosmotic solutions containing monobasic and dibasic sodium phosphate. They clean the colon by osmotically drawing plasma water into the bowel lumen.
However, this osmotic shift can cause serious volume contraction, electrolyte abnormalities such as hyperphosphatemia, and even death.1 Serious problems are more likely to occur in elderly patients, but also in patients with bowel obstruction, poor gut motility, renal failure, liver failure, or congestive heart failure.
Studies have shown hemodynamic changes indicating hypovolemia during sodium phosphate ingestion.13,14 One reported that 28% of patients had decreases in systolic blood pressure of more than 10 mm Hg, and 12% had decreases in systolic blood pressure of more than 20 mm Hg.13,14
In a study by Barclay et al,15 the concomitant use of a carbohydrate-electrolyte rehydration solution with the sodium phosphate limited the amount of fluid contraction.15 A similar study by Tjandra and Tagkalidis16 using a carbohydrate-electrolyte replacement solution called E-lyte showed a reduction in the degree of intravascular volume contraction, hypokalemia, and need for intravenous rehydration, although there was no effect on hyperphosphatemia resulting from ingestion of sodium phosphate.16
Phosphate nephropathy has also been reported after use of these solutions in patients with renal insufficiency, dehydration, or hypercalcemia, as well as in patients taking angiotensin-converting enzyme inhibitors or angiotensin receptor blockers.9
Current recommendations of the American Society of Colon and Rectal Surgeons, the American Society of Gastrointestinal Endoscopy, and the Society of American Gastrointestinal and Endoscopic Surgeons state that aqueous sodium phosphate is the preferable form of sodium phosphate and is an equal alternative to polyethylene glycol solutions except in pediatric and elderly patients, patients with bowel obstruction and other structural intestinal disorders, and patients with poor gut motility, renal failure, liver failure, or congestive heart failure.9 In fact, because of the significant volume contraction and electrolyte abnormalities that can occur, these groups list sodium phosphate preparations as contraindicated in patients with congestive heart failure.9
POLYETHYLENE GLYCOL IS STILL SAFER FOR THOSE WITH HEART FAILURE
Polyethylene glycol preparations have been shown to cause an increase in plasma volume in patients with disease states that predispose them to fluid retention.11 It has been postulated that these adverse effects may occur less often with preparations that use a lower volume, such as the 2-L polyethylene glycol regimen (HalfLytely) combined with bisacodyl or the 2-L polyethylene glycol 3350 solution (MiraLax). However, our patient experienced a heart failure exacerbation while drinking a reduced-volume preparation.
Another concern with polyethylene glycol solutions, especially HalfLytely, is hyperkalemia. Although no clinical reports have shown this finding, the small amount of potassium in this solution could be worrisome in patients with heart failure who are taking potassium-sparing diuretics or angiotensin-converting enzyme inhibitors.9
Nonetheless, when one considers the risks of fluid shifts with sodium phosphate preparations (which are in any event contraindicated for patients with congestive heart failure), the safest preparation for patients with congestive heart failure would be either a low-volume polyethylene glycol preparation or a split-dose standard-volume polyethylene glycol preparation with careful monitoring during and after use. Clinicians should emphasize to these patients the importance of continuing their cardiac medications during bowel preparation. The patients should also be instructed to notify their doctor about a change in body weight, difficulty breathing, chest tightness, and lower-extremity edema as they are taking the bowel preparation solution.12
Patients with severe left ventricular dysfunction may require short-term intensive care monitoring to manage plasma volume during and after bowel preparation.
