Anesthetic Management Flashcards
Most common cause of intestinal obstruction
Abdominal adhesions
2 main types of intestinal obstruction
- dynamic
2. adynamic
4 general mechanisms of intestinal obstruction
- volvulus with torsion
- incarceration in a confined space
- intrinsic and extrinsic obstruction of the lumen
- intussusception
Location of intestinal obstruction (3)
- high small bowel
- low small bowel
- large bowel
Can also be classified on its effect on the bowel (4)
- simple (lumen obstructed but mesenteric blood flow intact
- strangulated (compromised blood flow)
- closed loop ( bowel is looped)
- pseudoobstruction (no true mechanical obstruction exists)
Explain the pathophysiology of intestinal obstruction
In the early stages, bowel below the obstruction exhibits normal peristalsis and absorption until empty, when it contracts and becomes immobile. In an initial reaction, the bowel above its obstruction increases its blood supply and peristaltic activity in order to overcome the blockade. If the obstrtuction is not relieved, the bowel begins to dilate, causing a reduction in the strength of peristaltic contractions, eventually becoming flaccid. This is initially protective since it prevents vascular damage.
The bowel wall becomes edematous and eventually, fluid leaks into the peritoneum causing peritoneal irritation, contamination and signs of peritonitis. The bowel continues to distend leading to ischemia and necrosis.
The distention proximal to the obstruction is produced by what gas? (90%) (2)
- nitrogen
2. hydrogen sulphide
How does hypochloremic alkalosis occur in small bowel obstruction?
Biochemical investigations reflect sodium and water loss.
Chloride loss by creating an alkalosis, exacerbates potassium loss
How does metabolic acidosis occur?
If obstruction occurs lower in the GI tract, metabolic acidosis occur, because intestinal juices contain more bicarbonate than chloride.
How does hypoalbuminemia occur?
As the bowel becomes inflamed, there is increasing loss of protein. Starvation adds to increasing protein losses and consequent hypoalbuminemia exacerbates fluid shifts.
4 cardinal features of intestinal obstruction
- pain
- vomiting
- distention
- constipation
Small bowel obstruction: colicky pain localized in the epigastrium, hyperactive bowel sounds, nausea, vomiting, (bilious, if it occurs in the second part of the duodenum), vomiting of feculent material (related to enteric bacterial overgrowth)
Large bowel: clinically silent in early stage, abdominal discomfort and absolute constipation, pain in lower quadrants not associated with eating.
Worrying signs of intestinal obstruction:
- localized tenderness
- generalized peritonitis
- hypovolemia
- pyrexia
- tachycardia
Diagnosis
- Leukocyte count >25,000 : mesenteric occlusion or perforation
- Electrolytes can also suggest the location of obstruction: (large bowel) hypokalemia, hypomagnesemia, hypovolemia or hypophosphatemia
- Plain radiographs: confirm the dx (60%)
Large bowel: require enema to diff bet mechanical or pseudo-obstruction
Subdiaphragmatic air: indicating perforation
Anesthetic managment (read only)
- Discussions with the surgical team will revolve around the urgency of surgery, need for pre-operative optimisation, pain relief and availability of postoperative high dependency beds.
- Need for fluid rescucitation and adequate UO.
Pre-operative anesthetic management (what to ask or assess)
- medications
2. hydration status (UO, hypoalbuminemia, NGT, CVP)
