Answer:
Tap water enema utilizes hypotonic solution to promote defecation when the patient lies in a left Sims' position unless contraindicated.
During an enema, the solution passes rectum and enters sigmoid colon. Patient in a left Sims' position would benefit from the pull of gravity and therefore a more effective enema.
The recommended solution for tap water enema is 500 mL or less for the avoidance of water toxicity.
The rationale goes behind the ideas of osmosis and "water always follow solute." While the blood and human physiological environment is slightly more hypertonic (more solute per liter) with sodium than tap water, the hypotonic tap water would naturally follow the higher solute environment and move into the interstitial spaces, causing undesirable hypotonicity in the body referred as "water toxicity." Hence, it is important for clinicians to disregard the common misconception about tap water being "normal" or physiologically safe.
Always use the clinical caution that three being the magic number when it comes to enema procedure and check with physician if more than three enemas is necessary. Excessive enemas would place patient in the harm with water toxicity or electrolyte imbalance.
For insertion, lubricate 2.5 to 3 inches of the rectal tube and point tip in the direction of patient's umbilicus. Insertion length varies from 3-4 inches for adults, 2-3 inches for children, and 1-1.5 inches for infants. During instillation, the recommended height between the level of enema container or bag and the level of anus is 12 to 18 inches for high enemas, 12 inches for regular enemas, and 3 inches for low enemas.
Caution patient the feeling of distention is normal and the desire to evacuate stool might arise. Advise patient to contract rectal sphincter as long as patient can tolerate to promote better stimulation of peristalsis and defecation.
Place patient in semi or high Fowler's position with squatting position to promote defecation.
To withdraw the rectal tube, place toilet tissues around the tube at anus.
If patient's able to ambulate to the bathroom, advise patient not to flush toilet so inspection of amount, color (along with prescience of fresh or dark blood), and consistency (additional mucus or fluid) can be made.