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Oral case 94

Created: 5/11/2004

A 58-year old, 65 kg man is scheduled for a mediastinoscopy. He lost 10 kg in the last three months, and has a 40-pack year history of smoking. Blood pressure is 160/100 mm Hg, pulse is 78 bpm, respirations are 18, temperature is 37 degrees centigrade, and hemoglobin is 17 gm/dl. Medications include propranolol and a diuretic.

 Preoperative Evaluation

I. Respiratory system

1. Is the hemoglobin of 17 gm/dl significant? Why or why not?

2. How would you evaluate the respiratory system? Would pulmonary function tests be helpful?

3. Which pulmonary tests would you order? Explain.

4. Should he stop smoking? Explain.

5. When?

II. Hypertension

1. Is the blood pressure adequately controlled?

2. Is additional preoperative workup or treatment needed?

3. What do you want done?

4. What additional information is required?

5. The serum potassium is 3.2 mEq/L. Is this a problem?

6. How would you manage this?

7. The electrocardiogram shows left ventricular hypertrophy with nonspecific ST changes. How do you respond to this?

8. Does the patient require an echocardiogram preoperatively?

III. Premedication

1. A colleague suggests morphine 10 mg, and scopolamine 0.4 mg. Do you agree or disagree? Explain.

2. What are your goals for premedication?

3. Describe scopolamine's amnestic and side effects.

It is an anticholinergic as well as an amnestic agent. It is synergistic with benzodiazepines and morphine, but does not reliably cause amnesia like midazolam does. Side effects include tachycardia, mydriasis, cycloplegia, antisialogogue actions, bronchodilation, relaxation of the lower esophageal sphincter, increased body temperature, and delerium.

4. Do the other anticholinergics cause sedation as well?

No. Atropine has minimal central effects, and glycopyrrolate is a quaternary ammonium compound which is incapable of crossing the blood-brain barrier, therefore has no central effects.

5. Describe central anticholinergic syndrome and its treatment.

Atropine or scopolamine can cause this syndrome, which causes restlessness, confusion, or prolonged somnolence after anesthetics are discontinued. Scopolamine produces this syndrome more commonly, and it occurs more commonly in the elderly. The differential diagnosis should include pain, hypoxia, and hypotension. Treatment is with the anticholinesterase physostigmine, at 15-60 mcg doses, to a total dose of 1-2 mg.

 Intraoperative Course

I. Monitors

1. Should you monitor end-tidal CO2? Explain.

2. How do you monitor the adequacy of oxygenation?

3. Is an arterial catheter needed, or are pulse oximeter and capnography sufficient? Explain

II. Choice of anesthetic agents

1. A colleague suggests you avoid thiopental because of possible reactive airways in this patient, and suggests you use midazolam for induction. What is your response?

When given in sufficient doses, midazolam causes respiratory depression; it also decreases blood pressure, cardiac output, and systemic vascular resistance.

2. What agent would you choose for maintenance?

3. Compare the effects of these agents on bronchial tone and the cardiovascular system.

4. How will you prevent the wide swings in blood pressure often seen in hypertensive patients under anesthesia?

III. Intraoperative wheezing

1. During the course of a general anesthetic, the patient begins to wheeze and becomes difficult to ventilate. What is the etiology?

2. How would you search for the cause?

IV. Intraoperative hypotension

1. The blood pressure abruptly falls to 86/50 mmHg, and the pulse increases to 120 bpm fifteen minutes after surgery begins. What is your differential diagnosis?

2. What is the etiology and management of major bleeding?

3. How do you recognize a hemolytic transfusion reaction?

4. What is the management of further acute blood requirements?

5. Would a cell saver be helpful? Why or why not?

6. What are the complications of using the cell saver?

 Postoperative Care

I. Postoperative hypertension

1. On arrival in the recovery room, the blood pressure is 200/120 mmHg. Are you concerned? Why or why not?

2. What are possible causes?

3. What are your treatment choices?

II. Postoperative hoarseness

1. Twenty-four hours postoperatively, the patient complains of painless hoarseness. What do you tell him?

2. What do you do?

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