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Oral case 125

Created: 3/2/2005

A 70-year old 90 kg male is scheduled for transurethral resection of the prostate secondary to prostatic hypertrophy. Past medical history includes heavy smoking and hypertension. He had a myocardial infarction eight months ago that necessitated a permanent pacemaker. He has occasional angina for which he placed nitro-paste daily. He is also on aspirin 325 mg/day, propranolol 120 mg/day, and clonidine 0.3 mg bid. Blood pressure is 160/90 mmHg, pulse is 72 bpm, and respirations are 16.

 Preoperative Evaluation

I. Assessment of cardiac status

1. What further information is needed? Explain.

2. What cardiac signs and symptoms help predict outcome?

3. What is the significance of the previous myocardial infarction?

II. Pacemaker consideration

1. How do you determine if a pacemaker is functioning properly?

2. Is it important to know what type of pacemaker he has?

3. Does anesthesia affect its function? Explain.

4. Does surgery affect its function? Explain.

5. Are special precautions indicated? Explain.

III. Smoking habit

1. Does a history of heavy smoking influence anesthetic risk? Explain.

2. Should patients quit smoking cigarettes preoperatively?

It takes twelve to twenty-four hours of smoking cessation to decrease carbon monoxide and nicotine levels to normal. Ciliary function takes two to three days to normalize, and it takes about two weeks for sputum volume to change. Also, the risk of arterial thrombosis decreases. It takes six to eight weeks of cessation, however, for a significant change in pulmonary morbidity to occur.

After cessation of smoking, patients may be anxious, irritable, and may have increased sputum, exacerbation of reactive airways disease, and increased risk for deep venous thrombosis.

 Intraoperative Course

I. Monitoring

1. Is invasive monitoring indicated? Explain.

2. Discuss central line vs pulmonary artery placement.

3. Is an arterial catheter indicated?

4. How will you monitor pacemaker function?

II. Anesthetic choice:

1. The patient requests information regarding general vs regional anesthesia in light of his cardiac disease. Your answer?

2. The patient requests regional anesthesia. Is this reasonable?

3. What are advantages and disadvantages of regional?

4. What are advantages and disadvantages of epidural vs spinal?

5. Does the use of aspirin influence your decision? Explain.

III. Hyponatremia

1. During the resection, the patient becomes incoherent, hypotensive, and tachycardic. What is the cause?

2. The sodium is 124 mEq/l. What are the effects of hyponatremia on the cardiovascular system?

3. Would you treat with diuretics vs 0.9% saline vs 3% saline? Explain.

4. What are complications of each?

5. Explain what stimulates aldosterone release, and explain its actions.

Aldosterone regulates sodium excretion. When systemic or renal blood pressure decreases, or if hyperkalemia, increased adrenocorticotropic hormone, surgical stimulation, hypovolemia or hyponatremia occur, renin is released from the renal juxtaglomerular cells. This converts angiotensinogen to angiotensin I, and it is converted to angiotensin II in the lung. The two effects of angiotensin II include release of aldosterone from the adrenal cortex, and vasoconstriction. Aldosterone acts on the distal renal tubules and on the cortical collecting ducts, leading to sodium retention.

IV. Low hematocrit

1. The intraoperative hematocrit is 29%. How do you differentiate hemodilution vs bleeding?

2. What are general alternatives to homologous blood transfusion?

Alternatives include autologous transfusion, cell saver, intraoperative isovolemic hemodilution, or the use of crystalloid or colloids. The use of non-blood oxygen-carrying solutions are not yet available, and include such agents as stroma-free hemoglobin, polymerized hemoglobin, and perfluorochemicals.

3. Compare and contrast colloids used for fluid replacement.

Albumin can lead to hypervolemia, causing pulmonary edema. Hetastarch affects coagulation and should be limited to less than 20 ml/kg. Dextran solutions can cause anaphylaxis, interfere with platelet and red cell function, and can interfere with blood crossmatching.

2. Is transfusion indicated? Explain.

3. When should autologous blood be given?

Because these patients are still at risk of clinical errors or contamination, even autologous should be given if clearly indicated, such as for anemia, significant blood loss, or when additional bleeding will occur.

V. Pacemaker Malfunction

1. The heart rate decreases to 30 bpm and the patient feels weak, with prolonged electrocautery use. What is the cause?

2. What is the treatment?

 Postoperative Care

I. Persistent neural block

1. There is no change in sensory level three hours after subarachnoid block with 10 mg tetracaine. Are you concerned? Explain.

2. What is your differential diagnosis?

II. Hypotension

1. The blood pressure steadily decreases in the recovery room to 90/60 mmHg. What are possible causes?

2. How do you differentiate the causes?

3. What is your treatment?

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