Bowel Preparation in Colorectal Surgery
Though widely accepted as sensible and logical it has never been subjected to any really stringent scrutiny. The ideal method of mechanical preparation should be simple, inexpensive, without distress, and side effects to the patient. However, such an ideal method does not exist. It must be chosen with respect to patient acceptability, efficiency and influence on fluid and electrolyte imbalance and on fecal microflora. The conventional method involves a 3-day regimen consisting of low residue and clear liquid diet combined with purgation using laxatives and enemas. Although satisfactory in bowel cleansing in about 70 percent of patients, it is rather exhausting due to reduced calorie intake. It is time-consuming and may result in dehydration if the patient drinks an inadequate amount of fluids. These disadvantages stimulated the development of more reliable, efficient, and quicker methods which include.
Elemental Diets
Low residue liquid or elemental diets were used with the intention that nutrients could be absorbed in the small intestine. Although, these results in low fecal bulk, satisfactory cleansing is obtained in only 17 percent of the patients. Nausea and vomiting can occur and the evidence does not favor elemental diets as a sole means of bowel preparation.
Whole Gut Irrigation
Saline: Normal saline is instilled through a nasogastric tube at a constant rate of 50 to 70 ml per minute in 4 hours requiring a total of 10 to 14 liters of fluid. Cleansing effect is achieved in 90 percent of the patients however the concentration of colonic bacteria is not reduced unless antibiotics are added. Many patients complain of abdominal distension, nausea, and vomiting. Other drawbacks of this method include the large volume of irrigants, need of nasogastric tube, risk of electrolyte disturbance and water retention, and nursing care required to assist the patient. It is contradicted in patients with gastrointestinal obstruction, perforation, toxic colitis and has to be used with caution in patients with cardiac problems. Castor oil: (30–60 ml) orally achieves good cleansing but requires a large volume of magnesium citrate purgative to achieve the desired results and requires to be given two days before surgery followed by anal washouts a day prior which entails preoperative admissions for 3 to 4 days. Unpalatibilty is another drawback.
Mannitol: Mannitol is a nonabsorbable oligosaccharide which acts as an osmotic agent by pulling fluid into the bowel and producing a purgative effect by irritating the colon. Being a sugar it is quite palatable and can be flavored by mixing with fruit juice. Usually 4 liters of 5 percent solution is consumed over 4 hours which can be difficult and can result in abdominal discomfort and nausea. To avoid these side effects, hypertonic solutions (10 to 20 percent) can be used but these predispose to dehydration and electrolyte losses. Overall, good cleansing is produced in about 80 percent of the patients a high wound infection rate probably by acting as a bacterial nutrient and production of explosive gases as a result of fermentation into methane and hydrogen by anaerobic bacteria is seen. The same can be overcome by using of an antibiotic. Polyethylene glycol: To overcome the drawbacks of mannitol, polyethylene glycol (PEGLAC) in a balanced electrolyte solution was introduced which also acts as an osmotic purgative. To achieve satisfactory cleansing in more than 90 percent of the patients, an average of 2 to 4 liter of PEGLAC solution must be ingested with tea and lemon. Studies using PEG have shown a significantly lower incidence of fluid retention and lesser aerobic and anaerobic fecal bacterial counts compared to other agents. It is nowadays used as an agent of choice for preparations of the bowel before endoscopy and colonic surgery in a non-obstructed patient.
Bowel preparation in colorectal surgery
Picolax: It (sodium picosulphate and magnesium citrate) is a stimulant purgative that acts mainly on the left colon after activation by colonic bacteria and on osmotic laxative that cleanses the proximal colon. Two sachets in 2 liters of water are administered with dietary restrictions to improve effectiveness. Although acceptable cleansing is achieved in 85 percent of patients undergoing barium enema and colonoscopy, its efficacy for elective colorectal operations is poorly documented. Picolax is well tolerated but does produce fluid and electrolyte losses.
Antibiotic Bowel Preparations
Mechanical cleansing alone has failed to achieve a significant reduction in the total bacterial load of the colon and therefore the associated septic complications. The addition of antibiotics oral as well as parenteral to mechanical cleaning has resulted in a significant reduction of the infection rate from 30 to 60 percent in an uncovered patient to 2 to 10 percent in otherwise patients covered with wide spectrum antibiotics.
Oral Antibiotics
Because the aerobic Escherichia coli and the anaerobic Bacteroides fragilis are frequently involved organisms in septic complications following colorectal operations, oral antibiotics active against both types of bacteria must be given. Oral administration of erythromycin, neomycin, and metronidazole are popular. Several studies have documented the efficacy of oral antibiotics however antimicrobial used alone without mechanical cleansing has little impact on the postoperative infection rate.
Parenteral Antibiotics
Since parenteral antibiotics are effective only when adequate tissue levels are present at the time of contamination, systemic administration should start immediately before the surgery. A second or third-generation cephalosporin with metronidazole is the most commonly preferred agent. Studies have shown conflicting results when parenteral antibiotics were compared with oral or both. Whether antibiotics bowel preparation should be oral, systemic or both are still a controversial issue. The majority of the surgeons would prefer parenteral antibiotics or with concomitant administration of oral antimicrobials together with oral PEGLAC electrolyte solution as the method of choice of preoperative bowel preparation.
Though observational data suggest that mechanical bowel preparation before colorectal surgery reduces fecal mass and bacterial count in the lumen, the practice has been questioned because the bowel preparation liquefies feces, which could increase the risk for intraoperative spillage, and may be associated with bacterial translocation and electrolyte disturbance. Though commonly practiced without the benefit of evidence from randomized trials, and 2 of 3 meta-analyses suggest a higher rate of anastomotic leakage with mechanical bowel preparation thus calling for an end to the practice of mechanical bowel preparation in view of the possible disadvantages of this practice, patient discomfort, and the absence of clinical value. There are others who accept that though routine preoperative bowel cleansing is no longer justified prior to colorectal surgery in general, they call for further evaluation in cases such as total mesorectal resection with low anastomosis where it may still have a role and therefore to consider each case carefully, otherwise the chance of making an inappropriate decision exists with great consequences for patients.
The majority of surgeons believe that patients should have a standard bowel preparation 48 hours before the operation and should receive a single-dose antibiotic dose immediately preoperatively. For the bowel preparation, patients follow a strictly fiber-free diet 8 days before surgery and take a sodium phosphate oral solution the day before surgery. This method is very effective because it ensures an empty digestive tract and a flat small bowel, which facilitates the layering of intestinal loops, a crucial point for achieving adequate exposure. Alternatively, the polyethylene glycol can be used. In this case, administration 2 days before surgery is preferable to avoid distension of small bowel loops that may be difficult to handle during the surgery.
Though widely accepted as sensible and logical it has never been subjected to any really stringent scrutiny. The ideal method of mechanical preparation should be simple, inexpensive, without distress, and side effects to the patient. However, such an ideal method does not exist. It must be chosen with respect to patient acceptability, efficiency and influence on fluid and electrolyte imbalance and on fecal microflora. The conventional method involves a 3-day regimen consisting of low residue and clear liquid diet combined with purgation using laxatives and enemas. Although satisfactory in bowel cleansing in about 70 percent of patients, it is rather exhausting due to reduced calorie intake. It is time-consuming and may result in dehydration if the patient drinks an inadequate amount of fluids. These disadvantages stimulated the development of more reliable, efficient, and quicker methods which include.
Elemental Diets
Low residue liquid or elemental diets were used with the intention that nutrients could be absorbed in the small intestine. Although, these results in low fecal bulk, satisfactory cleansing is obtained in only 17 percent of the patients. Nausea and vomiting can occur and the evidence does not favor elemental diets as a sole means of bowel preparation.
Whole Gut Irrigation
Saline: Normal saline is instilled through a nasogastric tube at a constant rate of 50 to 70 ml per minute in 4 hours requiring a total of 10 to 14 liters of fluid. Cleansing effect is achieved in 90 percent of the patients however the concentration of colonic bacteria is not reduced unless antibiotics are added. Many patients complain of abdominal distension, nausea, and vomiting. Other drawbacks of this method include the large volume of irrigants, need of nasogastric tube, risk of electrolyte disturbance and water retention, and nursing care required to assist the patient. It is contradicted in patients with gastrointestinal obstruction, perforation, toxic colitis and has to be used with caution in patients with cardiac problems. Castor oil: (30–60 ml) orally achieves good cleansing but requires a large volume of magnesium citrate purgative to achieve the desired results and requires to be given two days before surgery followed by anal washouts a day prior which entails preoperative admissions for 3 to 4 days. Unpalatibilty is another drawback.
Mannitol: Mannitol is a nonabsorbable oligosaccharide which acts as an osmotic agent by pulling fluid into the bowel and producing a purgative effect by irritating the colon. Being a sugar it is quite palatable and can be flavored by mixing with fruit juice. Usually 4 liters of 5 percent solution is consumed over 4 hours which can be difficult and can result in abdominal discomfort and nausea. To avoid these side effects, hypertonic solutions (10 to 20 percent) can be used but these predispose to dehydration and electrolyte losses. Overall, good cleansing is produced in about 80 percent of the patients a high wound infection rate probably by acting as a bacterial nutrient and production of explosive gases as a result of fermentation into methane and hydrogen by anaerobic bacteria is seen. The same can be overcome by using of an antibiotic. Polyethylene glycol: To overcome the drawbacks of mannitol, polyethylene glycol (PEGLAC) in a balanced electrolyte solution was introduced which also acts as an osmotic purgative. To achieve satisfactory cleansing in more than 90 percent of the patients, an average of 2 to 4 liter of PEGLAC solution must be ingested with tea and lemon. Studies using PEG have shown a significantly lower incidence of fluid retention and lesser aerobic and anaerobic fecal bacterial counts compared to other agents. It is nowadays used as an agent of choice for preparations of the bowel before endoscopy and colonic surgery in a non-obstructed patient.
Bowel preparation in colorectal surgery
Picolax: It (sodium picosulphate and magnesium citrate) is a stimulant purgative that acts mainly on the left colon after activation by colonic bacteria and on osmotic laxative that cleanses the proximal colon. Two sachets in 2 liters of water are administered with dietary restrictions to improve effectiveness. Although acceptable cleansing is achieved in 85 percent of patients undergoing barium enema and colonoscopy, its efficacy for elective colorectal operations is poorly documented. Picolax is well tolerated but does produce fluid and electrolyte losses.
Antibiotic Bowel Preparations
Mechanical cleansing alone has failed to achieve a significant reduction in the total bacterial load of the colon and therefore the associated septic complications. The addition of antibiotics oral as well as parenteral to mechanical cleaning has resulted in a significant reduction of the infection rate from 30 to 60 percent in an uncovered patient to 2 to 10 percent in otherwise patients covered with wide spectrum antibiotics.
Oral Antibiotics
Because the aerobic Escherichia coli and the anaerobic Bacteroides fragilis are frequently involved organisms in septic complications following colorectal operations, oral antibiotics active against both types of bacteria must be given. Oral administration of erythromycin, neomycin, and metronidazole are popular. Several studies have documented the efficacy of oral antibiotics however antimicrobial used alone without mechanical cleansing has little impact on the postoperative infection rate.
Parenteral Antibiotics
Since parenteral antibiotics are effective only when adequate tissue levels are present at the time of contamination, systemic administration should start immediately before the surgery. A second or third-generation cephalosporin with metronidazole is the most commonly preferred agent. Studies have shown conflicting results when parenteral antibiotics were compared with oral or both. Whether antibiotics bowel preparation should be oral, systemic or both are still a controversial issue. The majority of the surgeons would prefer parenteral antibiotics or with concomitant administration of oral antimicrobials together with oral PEGLAC electrolyte solution as the method of choice of preoperative bowel preparation.
Though observational data suggest that mechanical bowel preparation before colorectal surgery reduces fecal mass and bacterial count in the lumen, the practice has been questioned because the bowel preparation liquefies feces, which could increase the risk for intraoperative spillage, and may be associated with bacterial translocation and electrolyte disturbance. Though commonly practiced without the benefit of evidence from randomized trials, and 2 of 3 meta-analyses suggest a higher rate of anastomotic leakage with mechanical bowel preparation thus calling for an end to the practice of mechanical bowel preparation in view of the possible disadvantages of this practice, patient discomfort, and the absence of clinical value. There are others who accept that though routine preoperative bowel cleansing is no longer justified prior to colorectal surgery in general, they call for further evaluation in cases such as total mesorectal resection with low anastomosis where it may still have a role and therefore to consider each case carefully, otherwise the chance of making an inappropriate decision exists with great consequences for patients.
The majority of surgeons believe that patients should have a standard bowel preparation 48 hours before the operation and should receive a single-dose antibiotic dose immediately preoperatively. For the bowel preparation, patients follow a strictly fiber-free diet 8 days before surgery and take a sodium phosphate oral solution the day before surgery. This method is very effective because it ensures an empty digestive tract and a flat small bowel, which facilitates the layering of intestinal loops, a crucial point for achieving adequate exposure. Alternatively, the polyethylene glycol can be used. In this case, administration 2 days before surgery is preferable to avoid distension of small bowel loops that may be difficult to handle during the surgery.
