A 60-year old man is scheduled for an exploratory laparotomy for small bowel obstruction. He has a history of chronic renal failure requiring hemodialysis, and is taking clonidine and propranolol for hypertension. Blood pressure is 170/100 mmHg, pulse is 100 bpm, temperature is 38 degrees C and hemoglobin level is 8 gm/dl.
I. Evaluation of renal function and fluid status
1. How would you decide if the patient needs dialysis prior to surgery?
2. What further tests of renal function would you order? Explain.
3. What other organ systems should be evaluated in a patient with chronic renal failure? Explain.
4. How would you evaluate fluid status preoperatively?
II. Evaluation of cardiovascular status
1. Do you think the blood pressure is adequately controlled? Why or why not?
2. How does poorly controlled hypertension increase the risk of anesthesia?
3. What are the effects of clonidine given at 5 mcg/kg as a premedication?
As a premedication at this dose, clonidine, which is an alpha-2 agonist, attenuates the response of tachycardia and hypertension to laryngoscopy and intubation. It also decreases MAC by up to 40%, and can cause bradycardia and hypotension when used with other antihypertensive agents.
4. The patient states he has not taken his clonidine or propranolol for two days. What are the dangers of this?
5. What treatment do you recommend? Explain your rationale.
1. What monitors should be used for evaluation of fluid status?
2. What monitors should be used for measurement of systemic arterial pressure?
3. What are the advantages and disadvantages of direct measurement vs automated blood pressure cuff?
4. What information can be gained by measurement of end-tidal CO2?
II. Selection and management of anesthesia
1. What are your major considerations in planning induction of general anesthesia for this patient?
2. Should he receive preoperative antacids? Explain.
3. Should he receive preoperative cimetidine? Explain.
4. Should he receive a preoperative nasogastric tube? Explain.
5. Would midazolam offer advantages over thiopental for induction? Explain.
6. What induction agents and muscle relaxant would you use for a rapid sequence induction?
7. Is the priming principle useful?
8. What agents would you use for maintenance?
9. What agents, if any, are contraindicated?
10. What effect does your agent have on the kidneys?
11. What effect does your agent have on gastrointestinal motility?
12. What effect does your agent have on the cardiovascular system?
III. Management of intraoperative hypotension
1. Fifteen minutes after incision, the blood pressure drops to 60/40 mmHg. What is your differential diagnosis?
2. What is your management?
3. Once the blood pressure is restored, you note that the pulsation and bruit over the patient's A-V fistula have disappeared. What will you do?
IV. Management of intraoperative hypoxia
1. One hour after the beginning of the operation, arterial blood gas shows pH=7.33, paCO2 =35 mmHg, paO2=60 mmHg on 50% FIO2. What is your differential diagnosis?
2. What is your management?
I. Criteria for continued mechanical ventilation and extubation
1. Would you plan to keep the patient on mechanical ventilation postoperatively?
2. How do you decide whether or not to continue mechanical ventilation?
3. What criteria would you use to decide when to extubate the patient?
II. Management of postoperative delirium
1. Ten minutes after the patient arrives in the recovery room, you are called to see him because he is thrashing around in bed. The nurse suggests sedation. Do you agree?
2. How would you determine the cause of his delirium?
3. If the cause is pain, how would you treat him?
4. Would epidural narcotics be a good choice?