ANESTHESIA FOR INTESTINAL OBSTRUCTION

Preoperative Management

1. Fluid and Electrolyte Imbalance

2. Bowel and Abdominal Distention

3. Respiratory Problem

4. CVS Problem

5. Vomiting, Regurgitation and Aspiration.

6. Investigation

7. Premedication

1. Fluid and Electrolyte Imbalance

Dehydration: Normally 7-9L of fluids are secreted into the upper

intestinal tract daily.

In small intestinal obstruction, fluid loss occurs due to:

Accumulation of fluids

Increased secretion

Decreased reabsorption

This causes loss of isotonic salt water resulting in isotonic contraction of ECF volume.

SO; dehydration and increased hematocrit occur.

1. Fluid and Electrolyte Imbalance

6000ml of fluid accumulation in bowel.

At late stages with hypotension and tachycardia

3000ml of fluid accumulation in bowel.

At Well established cases with vomiting

1500ml of fluid accumulation in bowel.

At Early stage

1. Fluid and Electrolyte Imbalance

The degree of dehydration is evaluated by:1. Duration of illness

2. Presence of vomiting

3. Skin elasticity

4. Sunken eye

5. Oliguria....ect.

The dgree of ECF loss can be monitored by serial hematocrit determinations

Rise in Hct is proportional to the amount of fluid loss.

If Hct increases to 55% this indicates that about 40% of plasma and ECF volume have been lost.

Treatment 2-6 liters of IV fluid are needed according to the degree of

dehydration by RL or NS

I. Fluid and Electrolyte Imbalance

Electrolyte Disturbances:1. Hyponatremia and Hypochloremia.

Because fluid accumulation and vomiting.

2. Hypokalemia. Mainly due to renal mechanisms.

Secondary to metabolic alkalosis and hyperaldosteronism.

Acid Base Imbalance: Metabolic Acidosis are more common due to:

Dehydration and loss of alkaline intestinal secretion

Starvation ketosis.

II. Bowel and Abdominal Distention

Occurs due to accumulation of fluids and gases.

Resulting in:

a. Blockade of the venous outflow.

b. Blockade of the blood supply to the obstructed segment.

c. Hindering of diaphragmatic movement.

d. Decreasing venous return.

e. Progressive distention may cause rupture of colon.

f. Progressive distention may cause tense abdominal wall.

II. Bowel and Abdominal Distention

We need:

1. Naso-gastric tube for abdominal decompression in preoperative Mx..

2. Deeper anestheisa and muscle relaxants to provide adequate operative conditions.

3. Gradual escape of fluid and Monitor BP frequently during incision.( sudden escape of fluids into the peritoneal cavity may cause severe hypotension ).

Role of nasogastric aspiration

1. Reduce bowel distension

2. Improve pulmonary ventilation

3. Reduce risk of subsequent aspiration during induction of anesthesia and post extubation

III.Respiratory Problems

Due to:

1. Abdominal distention which hinders the diaphragm resulting in inadequate ventilation.

This decreases ( Vt, FRC, ) and causes a decrease in PaO2 and an increase in PaCO2.

2. Weakness of intercostal muscles due to hypokalemia.

IV.CVS Problem

Hypotenion and Tachycardia up to shock.

Due to:

1. Hypovolemia

2. Decreased VR.

3. Septic shock

4. Hyponatremia

Arrhythmias ( ventricular ).

Due to:

1. Hypokalemia

V. Vomiting, Regurgitation and Aspiration.

Reversal of peristalsis and mechanical obstructionpushes the intestinal juice in addition to the gastric juice to produce a full stomach with an increased inta-abdominal pressure.

VI.Investigation

1. X-ray abdominal in supine and erect position: To ensure diagnosis of intestinal obstruction.

2. Ix. To detect complications: Hct.

WBCs

Elecrtolytes, Acid base disturbances.

Atrerial blood gases PaO2 and PaCO2.

VII.Premedication

Avoid all oral premedication.

Avoid drugs that may inhibit respiration e.g. ( opioids, sedative, ....

Avoid anticholinergics e.g. If fever or tachycardia occure.

Avoid antiacids or H2 blockers although there is a risk of aspiration as;

The may stimulate vomiting.

They are of low value if a large volume of fluids are already sequestrated in the bowel e.g. High intestinal obstruction.

Intraoperative Management

1. Choice of anesthesia.

2. Monitoring.

3. Induction and Intubation.

4. Maintenance.

5. Extubation.

Intraoperative management

Choice of anesthesia Regional anesthesia :

Its avoided if significant fluid depletion is suspected.

General anesthesia :

Monitoring: Standard + UOP, CVP and PCWP.

Intraoperative management

Induction and Intubation: There is a major risk of aspiration causing very high

mortality rates.

1. Awake Intubation:

In cooperative patient.

N.B.; Avoid anesthesia of the larynx to avoid loss of protective reflexes of the larynx against vomiting or regurgitation.

Then do laryngoscopy and intubation followed by induction

Intraoperative management

2. Rapid sequence crash induction:

Its done in supine or lateral position with head down tilt (10 dgree) to avoid aspiration if vomiting occurs.

Preoxygenation: 8-10L OF 100% O2 for 2-5 min.

Precurarization (defasciculation) does of NDMR to avoid suxamethonium fasciculation.

Naso-gastric tube should be removed before intubation to:

Allow effective cricoid pressure.

Avoid lower esophageal sphincter dysfunction.

Avoid hindering of laryngoscopy and intubation.

Intraoperative management

Iv agents:

1. Thiopentone is a good choice if there is NO hypotension.

2. Ketamin or Etomidate are good choice if there is hypotenion.

Intraoperative management

Maintenance : O2 +Potent inhalational agent+NDMR+IPPV

Careful titration of doses of inhalation agents is needed to avoid severe hypotension.

N2O should be avoided in bowel obstruction because it increases gas distention which increases intra-luminal gas volume and pressure.

This results in:

1. More increased abdominal distention

2. Increased bowel ischemia and necrosis.

3. Difficulties with abdominal closure at the end of surgery.

Intraoperative management

Extubation: Awake extubation in left lateral position.

After returning of upper airway reflexes

After good suctioning.

Postoperative management

Continue the preoperative managment Fluid and electrolyte correction.

Respiratory and CVS monitoring.

Pstoperative ileus Due to hyponatremia and hypokalemia.

Pstoperative abdominal decompression Continued for 5-6 days

Postoperative management

Pstoperative respiratory problems Abdominal distention is present

Abdominal pain is present

Residual effects of inhaled and IV anesthetic.

Reduction 15-20 % of FRC more than a week after any upper abdominal surgery.