A 75-year old 70 kg woman is to have repair of a hip fracture sustained in a fall three days ago. She has been an insulin-dependent diabetic for thirty years, and takes 30 U NPH insulin daily. She is a heavy smoker with a chronic nonproductive cough. Blood pressure is 140/80 mmHg, pulse is 66 bpm, respirations are 16, temperature is 37.5 degrees centigrade, hemoglobin is 9.2, and glucose is 300 mg/dL.
I. Evaluation of diabetes
1. Do you want further information regarding her diabetic status?
2. How would you manage preoperative insulin, glucose, and fluids?
3. How could you tell whether this patient has autonomic dysfunction?
A history of drug use with autonomic effects, orthostatic symptoms, blurry vision, changes in sweating or in moistness of eyes and mouth, incontinence, diarrhea or constipation, and impotence are significant. Physical exam findings of orthostasis and heart rate changes are very important as well.
4. What is your differential diagnosis of autonomic dysfunction?
Causes include drugs, diabetes mellitus, hyperthyroidism, pheochromocytoma, human immunodeficiency virus, amyloidosis, uremia, alcohol use and withdrawal, rheumatoid arthritis, and systemic lupus erythematosus. Less common causes include Guillain-Barre syndrome, Eaton-Lambert syndrome, Shy-Drager syndrome, Fabry's disease, heavy metal autonomic neuropathy, cis-platinum therapy, vincristine chemotherapy, tetanus, botulism, and paraneoplastic autonomic dysfunction.
5. What are some drugs that have autonomic effects?
Anticholinergic effects are seen with antipsychotics, antihistamines, tricyclic antidepressants, cyclobenzaprine, and amantadine. Drugs, which may cause an exaggerated sympathetic response include monoamine oxidase inhibitors, amphetamines and cocaine.
II. Evaluation of pulmonary status
1. How does a heavy smoking history increase risks of anesthesia?
2. What are the pathophysiologic effects of smoking?
3. Would you do bedside pulmonary function tests? Explain.
4. Which tests do you want?
5. Do you want an arterial blood gas?
6. On room air, pH=7.41, paCO2 =45 mmHg, and paO2 =60 mmHg. What is your management?
III. Evaluation of anemia
1. Why is she anemic?
2. Would you give a preoperative transfusion?
3. How do you decide whether or not to transfuse?
4. What are some general methods to decrease intraoperative blood loss?
Rigorous hemostasis, avoiding hypertension, deliberate hypotension, and regional anesthesia are useful methods.
I. Choice of anesthetic
1. Is a regional or a general anesthetic preferred in this patient? Explain.
2. Could there be any contraindications to regional technique in this patient?
3. Discuss epidural vs subarachnoid block, discussing advantages and disadvantages of each.
4. What local anesthetic would you use? Explain.
5. What effect does adding local anesthetic to neuraxial opioids have?
The combination is synergistic; there is greater analgesia than if either one was used alone. This allows fewer side effects, as each can be used in a lower concentration.
5. What drugs would you use as a test dose for an epidural? Explain
6. What drugs would you choose for induction? Explain.
7. What are the respiratory effects of this agent?
8. Is etomidate preferable to thiopental? Explain.
Etomidate is an imidazole dissolved in propylene glycol. At 0.3 mg/kg, unconsciousness occurs rapidly, and recovery of function is equivalent to that of thiopental. It undergoes hepatic metabolism, and is cleared five times faster than thiopental. Myoclonus may occur upon induction, and nausea and vomiting are common. It is known for its cardiovascular profile, which is very stable.
9. What are the cardiovascular effects of each?
10. What would you use for maintenance? Explain.
II. Diagnosis and management of glucose abnormalities
1. A general anesthetic is chosen.
A colleague suggests that you do not give insulin perioperatively because hypoglycemia is dangerous during anesthesia, but hyperglycemia is harmless. Do you agree?
2. How do you diagnose hypoglycemia during general anesthesia?
III. Management of intraoperative cardiac arrhythmia
1. One hour later, unifocal and then multi-focal premature ventricular contractions are noted. How do you determine the etiology?
2. Will you treat?
4. Ventricular tachycardia develops. What is your treatment?
5. Discuss pharmacologic therapy vs synchronized cardioversion vs defibrillation.
6. Normal sinus rhythm is obtained. Should surgery continue? Explain.
I. Management of hypothermia
1. On arrival to the recovery room, central temperature is 33 degrees centigrade. What are the dangers of this?
2. Would you report this temperature to the lab if you were to send an arterial blood gas now? Explain.
3. How would you treat this hypothermia?