25. 1 Acute pancreatitis
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СодержаниеLaboratory Tests Treatment of intestinal obstruction |
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Laboratory Tests
Any patient with vomiting or evidence of intra-abdominal fluid loss who is suspected of having intestinal obstruction should have laboratory measurements of serum sodium, chloride, potassium, bicarbonate, and creatinine. The hematocrit, white blood cell count, and serum electrolytes should be measured serially to assess therapy and to detect the earliest evidence of tissue necrosis.
TREATMENT OF INTESTINAL OBSTRUCTION
In most cases, the treatment for intestinal obstruction includes surgical relief of the obstruction. Because severe metabolic derangements may accompany the obstruction, the timing of the operation requires careful judgment. The overlapping sequence of events in managing patients with intestinal obstruction should be investigation, resuscitation, and operation. The timing of operation depends on three factors: duration of obstruction, i.e., severity of fluid, electrolyte, and acid-base abnormalities; the opportunity to improve vital organ function; and consideration of the risk of strangulation. The mortality from obstruction with intestinal gangrene ranges from 4.5% to 31%, whereas with simple mechanical obstruction relieved within 24 hours, the mortality is about 1%. Because no test reliably detects strangulation preoperatively, operation should be performed as soon as is reasonable. Absence of fever, tachycardia, localized tenderness, and leukocytosis indicates that nonoperative management may be safe. However, the presence of any one or more of these findings mandates operation.
A patient with symptoms of short duration—24 to 30 hours—and with minimal metabolic disturbances and no pre-existing pulmonary, cardiac, or renal disease can undergo operation when the diagnosis is made. A patient in whom fluid and electrolyte imbalance develops after several days of illness may profit from 18 to 24 hours of preoperative preparation.
Patients with obstruction of the bowel are likely to be depleted of water, sodium, chloride, and potassium, so intravenous therapy should usually begin with an intravenous isotonic sodium chloride solution. After the patient has formed adequate urine, potassium chloride should be added to the infusion. Sufficient fluids elevate and maintain the central venous pressure to between 5 and 10 cm. of saline. Administration of blood, plasma, or both should be considered if the patient is in shock and if strangulation is suspected. Operation should be considered after pulse, blood pressure, central venous pressure, and urinary output become normal. If marked hemoconcentration and severe electrolyte imbalance were present initially, laboratory studies should be repeated; if the values return to normal, the patient can undergo operation. Antibiotics should be given during resuscitation, particularly if strangulation is suspected.
In addition to fluid therapy, another important adjunct to the supportive care of patients with intestinal obstruction is nasogastric or intestinal suction. Nasogastric suction with a Levin tube empties the stomach, reducing the hazard of pulmonary aspiration of vomitus and minimizing further intestinal distention from swallowed air preoperatively. A nasogastric tube is not effective in decompressing distended intestine.
The urgency for early operation varies among patients thought to have partial obstruction of the small bowel due to adhesions. Some studies reveal that most patients with adhesive partial obstruction of the small bowel had complete resolution with nasogastric suction, and most patients so treated responded within 24 hours. Patients with intestinal obstruction due to intra-abdominal cancer usually do not respond well to conservative treatment, but malignant obstruction can frequently be relieved surgically. Judgment is required, however, in managing malignant intestinal obstruction in a terminally ill patient. Certain patients with obstruction of the small bowel should undergo operation within several hours of admission to the hospital, including those with no history of previous abdominal surgery, those with incarcerated external hernias, those with signs of peritonitis, and any patient suspected of having strangulated bowel.
Operation may be delayed under certain circumstances. In patients with pyloric obstruction, operation can safely be postponed to correct the fluid and electrolyte imbalance. A patient in whom intestinal obstruction develops immediately following an abdominal operation should initially be treated nonoperatively. Overlooked strangulation is a risk in this instance, however. In one report of 41 patients with early postoperative obstruction of the bowel, the obstruction resolved in 30 patients without operation; however, two of those patients later required operation for bowel obstruction. Infants with ileocecal intussusception respond to hydrostatic reduction of the intussusception, which avoids operation entirely. Adults with intussusception should undergo operation because of the high frequency of bowel abnormalities causing the intussusception. In patients with sigmoid volvulus, sigmoidoscopy or colonoscopy can achieve decompression. In patients with intestinal obstruction due to an acute exacerbation of Crohn's disease, a period of conservative treatment may resolve the obstruction. Patients with chronic partial obstruction may be managed by less urgent operative treatment than patients with acute complete obstruction.
Operative Treatment for Intestinal Obstruction
In general, the nature of the problem determines the approach to management of intestinal obstruction. In simple obstruction, such as an incarcerated inguinal hernia, operative reduction and repair of the hernia suffice. Obstruction caused by peritoneal adhesions can be relieved by division of the adhesions. A second approach to obstructing lesions is to create an intestinal bypass. An example of this therapy is the treatment of radiation stricture of the ileum by ileotransverse colon anastomosis. The placement of a cutaneous fistula, such as a colostomy, proximal to the obstruction is another standard form of therapy. Excision of a lesion with restoration of intestinal continuity is also used frequently. An example of this therapy is to treat obstructing carcinomas of the cecum by right colectomy and primary ileotransverse colon anastomosis.
With few exceptions, operation for intestinal obstruction requires general anesthesia administered with an endotracheal tube. One of the risks in operating on patients with intestinal obstruction is vomiting and tracheobronchial aspiration of the feculent vomitus.
In the absence of external hernia in patients with obstruction of the small bowel, a midline incision works well for abdominal exploration. The obstructed point can be identified by following the distended bowel distally to find collapsed intestine. Decompression of the obstructed intestine makes the operative manipulation easier. Passing an intestinal tube through the nose and stomach into the intestine at operation can sometimes empty the distended bowel.
In operating on patients with multiple intra-abdominal adhesions, the surgeon should verify that no additional sites of obstruction remain distal to that which is clinically obvious. The luminal contents can be expressed manually into the cecum to rule out other possible distal obstructing points.
It is often difficult to determine whether a segment of bowel is viable. The criteria generally used in determining bowel viability are color, motility, and arterial pulsation. If intestinal viability is questionable, the bowel segment should be completely released and placed in a saline-moistened sponge for 15 to 20 minutes and then re-examined. If normal color has returned and peristalsis is evident, it is safe to retain the bowel. If there is reasonable doubt about its viability, the bowel should be resected.
The approach to colon obstruction is somewhat different from that to small bowel obstruction. The classic method of treating obstruction of the left colon entails three separate operative steps. First, relief of gaseous distention is achieved by colostomy proximal to the obstruction. Colostomies can be performed where the colon is mobile with a mesentery, such as in the sigmoid or transverse colon. In most instances, transverse colostomy is the best choice in treating left-sided colon obstruction. The diseased segment of colon can then be removed and anastomosed, leaving the colostomy intact. Finally, the colostomy is closed when the anastomosis is completely healed. It would also be appropriate to resect the obstructing lesion and perform a colostomy at one operation and to close the colostomy during a second subsequent operation. Recent reports describe treating left colon obstruction by resection and primary anastomosis. One study of 55 patients with left colon obstruction due to cancer included 13 patients treated by resection and primary anastomosis without mortality.
Obstructive lesions of the cecum and right colon are usually managed by right colectomy with ileotransverse colostomy. Right colectomy can be done safely in patients with obstruction because the obstructed colon can be removed and the dilated small bowel can usually be sutured safely to normal colon. The treatment of volvulus of the cecum depends on the viability of the cecum. If it is nonviable, right colectomy should be done. If it is viable, detorsion with fixation of the cecum is appropriate.