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Oral case 88

Created: 3/11/2004

A 56-year old 98 kg man with a long history of back pain is scheduled for a lumbar laminectomy and fusion. He is a heavy smoker, and has increased his smoking in the past few months. He is also hypertensive and maintained on hydrochlorothiazide 50 mg qd, and propranolol 10 mg tid. Blood pressure is 170/90 mmHg, pulse is 76 bpm, hemoglobin is 16 gm/dl and potassium is 3.3 mEq/l.

 Preoperative Evaluation

I. Risk of obesity

1. Does obesity increase the risk of anesthesia? Explain.

II. Smoking history

1. How does a history of smoking affect anesthetic risk?

2. Is there an advantage to abstaining from cigarettes twenty-four hours prior to surgery? Explain.

3. Would preoperative IPPB therapy be helpful? Why or why not?

4. How would you manage this?

III. Cardiac status

1. Is this patient's hypertension of concern to you? Why or why not?

2. How would you evaluate his hypertension?

3. Would an electrocardiogram or an echocardiogram help? Explain how.

4. Will you alter his medication regimen? Explain.

5. Is the hemoglobin a problem?

6. What are possible causes of his high hemoglobin?

7. Discuss the oxygen-hemoglobin dissociation curve.

The paO2 is on the x-axis, with saturation on the y-axis. It is a non-linear curve, with a paO2 above 95 mmHg the saturation is above 95%, and at less than a paO2 of 85 mmHg, there are profound changes in saturation. Normal hemoglobin is 100% saturated at a paO2 of 100, and a saturation of 90% corresponds to a paO2 of 60%. A paO2 of 40 mmHg is about 75% saturated, which is normal for mixed venous blood.

7 Does the potassium concern you? Explain.

8. Will you try to decrease or increase it? Explain why.

 Intraoperative Course

I. Monitoring

1.Which monitors will you select? Explain.

2. Is central monitoring required?

3. Would you want a central venous line or a pulmonary artery catheter? Explain.

4. What are the hazards of pulmonary artery catheterization?

5. Which precordial electrocardiogram leads will you use? Explain.

6. Discuss the use of lead V5.

II. Selection of anesthetic drugs

1. Will you use a nitrous/narcotic or a halogenated compound? Explain.

2. What is the effect of halogenated agents on lung disease?

3. What is the effect of halogenated agents on the cardiovascular system?

4. Will you use nitrous oxide?

III. Positioning

1. After turning the patient to the prone position, the blood pressure is 70/30 mmHg. What are possible causes?

2. What is your treatment?

3. How would you prevent this from happening?

4. The surgeon complains of brisk oozing. What are some causes?

5. What effect does positioning have on intraabdominal pressure?

6. How would you treat the patient?

7. Is the brachial plexus especially vulnerable in this position?

8. How does one protect the brachial plexus?

9. Would the kneeling position help?

10. How?

11. List disadvantages of the kneeling position.

IV. Management of hypertension

1. The blood pressure increases to 220/100 mmHg. What are causes?

2. The electrocardiogram shows 3mm depression of ST segments. Is this an ominous sign? Explain.

3. What is your treatment?

4. Which drug will you select?

5. Discuss nitroprusside vs nitroglycerin vs trimethaphan vs high concentrations of halogenated agents.

Nitroprusside and nitroglycerin penetrate vascular endothelium, act as substrates for formation of nitric oxide, which binds to the enzyme guanyl cyclase, which forms cyclic guanine monophosphate, which causes relaxation of smooth muscle vasculature. Nitrogylcerin predominantly acts on capacitance vessels, and nitroprusside acts primarily on arterioles.

6. Discuss the mechanisms of each.

7. Discuss the hazards of each.

V. Management of heart failure

1. The central venous pressure increases from 10 to 20 cm H2O, and the pulmonary compliance decreases. Additionally, wheezes are heard. What is your differential diagnosis?

2. How do you manage the patient?

3. Which digitalis preparation would you use?

4. What is the mechanism of action?

5. What is the relationship to the potassium level?

6. What are the hazards?

 Postoperative Care

I. Management of pain

1. Would you use regional vs intravenous techniques? Explain your rationale.

2. Which narcotic would you select?

3. What are the hazards of this narcotic?

4. Which mode of administration would you use?

II. Diagnosis and treatment of atelectasis

1. The patient is extubated, but postoperatively, is febrile, tachycardic, tachypneic, and has a clear airway, but appears dusky. What is your differential diagnosis?

2. What is your treatment?

III. Brachial plexus injury

1. He complains of numbness and weakness in the left arm. What are possible causes?

2. Discuss the diagnosis of specific sensory, motor, and sympathetic components.

3. What is the prognosis?

4. What is the therapy?

5. What do you tell the patient?

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