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Oral case 45

Created: 5/10/2004

A 28-year old 60 kg woman is six months pregnant and is scheduled for cholecystectomy and common duct exploration for recurrent obstruction and jaundice. She takes Theo-Dur for chronic asthma and is very anxious. Blood pressure is 100/64 mmHg, pulse is 86, respirations are 20, temperature is 37 degrees centigrade, and hematocrit is 34.

 Preoperative evaluation

I. Pulmonary status

1. Are preoperative pulmonary function tests required?

2. Which ones do you particularly want to see?

3. What changes are expected with pregnancy?

4. How do you assess the adequacy of theophylline therapy?

5. Would you start theophylline infusion on the morning of surgery?

6. What are the effects of sympathomimetic bronchodilators on the uterus?

II. Premedication

1. How will you relieve her anxiety?

2. Are you concerned about the effects of drugs on the fetus? Why or why not?

3. Compare the risks of surgery and anesthesia at six months versus very early or very late in pregnancy.

4. Are opioids contraindicated in pregnancy? Explain.

5. Are opioids contraindicated by obstructive jaundice? Why or why not?

Opioids cause spasm of the sphincter of Oddi, and thus increase common bile duct pressures, so should be avoided in patients with gallbladder problems, especially if an intraoperative cholangiogram is to be done. This would avoid the question of spasm, should a restriction be found, and would avoid the use of naloxone for reversal in an anesthetized patient.

Some think that the incidence of opioid-induced spasm of the sphincter of Oddi is so low, and is variable with respect to the opioid used, especially meperidine's low risk, that the theoretical argument is seldom clinically significant.

6. Is metoclopramide indicated?

III. Cardiovascular status

1. Is her hematocrit of concern?

2. Is it normal for pregnancy?

3. Why is it low?

4. Would you transfuse this patient preoperatively?

5. Would you delay the operation in order to work up the low hematocrit?

6. Would you order blood?

 Intraoperative course

I. Monitoring

1. Do pulse oximetry and end-tidal capnography substitute for arterial blood gases?

2. Would you insert an arterial cannula?

3. What are the risks and benefits?

4. Would you insert a central venous catheter?

5. pH = 7.34, PvO2 is 40 mmHg, and PvCO2 is 46 mmHg. What is your interpretation?

6. Would you monitor the fetal heart rate? If so, how?

II. Anesthesia

1. Is continuous epidural a good choice for this patient?

2. What are the effects of a T4 block on ventilation?

3. What are the effects of a T4 block on the fetus?

4. The patient insists on general anesthesia. Is thiopental contraindicated by asthma?

5. Is ketamine a better choice? Why or why not?

6. What volatile anesthetic would you choose for maintenance? Explain.

7. What is the risk of exacerbating jaundice?

8. Would you use nitrous oxide? Why or why not?

Nitrous oxide has been shown to produce skeletal abnormalities when given to pregnant rats at more than 50% concentration for over 24 hours. Direct effects have not been seen in humans, but it probably is best avoided in the first trimester. The mechanism involves inhibition of methionine synthetase, which is involved in DNA synthesis; it may also decrease uterine blood flow.

III. Hypotension and hypoxemia

1. Blood pressure drops to 80/50 mmHg and oxygen saturation is 80% on pulse oximetry. What is your immediate treatment?

2. What is your differential diagnosis?

3. Is supine hypotensive syndrome a realistic cause?

4. What about a pulmonary embolus?

5. How do you establish a diagnosis of pulmonary embolism?

6. Would you place a pulmonary catheter?

7. Would you anticoagulate this patient in the operating room?

IV. Fetal bradycardia

1. The heart rate decreases from 140 to 120 bpm after induction of anesthesia. What is your interpretation?

2. Later, the heart rate decreases to 90 bpm. Are you concerned?

3. What is your differential diagnosis?

4. What is your treatment?

V. Extubation

1. Would you extubate awake or deep? Explain.

2. The patient coughs on the tube, but is not responsive to commands. Do you extubate, or wait until she is awake?

3. She begins to audibly wheeze. What do you do?

 Postoperative care

I. Postoperative pain management

1. What are your alternatives for this patient?

2. Would you give a spinal opioid before or after the case?

3. Would you insert it while the patient is awake or anesthetized?

4. Is this preferable to an intercostal nerve block?

5. What are the benefits and risks of patient controlled anesthesia?

6. What effects on the fetus are seen with patient controlled anesthesia?

II. Oliguria

1. There is only 5 ml urine in the first hour of recovery room stay. What is your differential diagnosis?

2. How would you rule out each of your diagnoses?

3. A colleague suggests rapid infusion of 500 ml of D5LR. Do you agree?

4. There is still minimal urine after the above treatment. Is a diuretic indicated? Why or why not?

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