A three-year old boy is scheduled for outpatient surgery for repair of strabismus under general anesthesia. He has marked kyphoscoliosis and club feet. There is a history of an unexplained intraoperative death of a sibling. Blood pressure is 90/60 mm Hg, pulse is 100, and temperature is 37 degrees.
I. Problems of kyphoscoliosis
1. What are the anesthetic problems associated with kyphoscoliosis?
2. Are they a likely problem in this case? Why or why not?
3. Should arterial blood gasses and pulmonary function tests be obtained?
Pulmonary function tests are expensive and insensitive, and are not routinely ordered for patients with lung disease. The history, physical exam, and chest x-ray should be adequate to plan anesthesia for strabismus surgery. If the patient was to have a lung resection, pulmonary function tests in combination with a ventilation/perfusion scan can assist in anesthetic management and in predicting outcome. These tests can be useful in patients with lung disease who have abdominal or extensive surgery, and a flow volume loop can assist in management of variable intrathoracic obstruction, when paralysis or positive pressure ventilation can adversely affect the obstruction.
4. Which ones would you order? Why?
1. Is this a likely problem? Why or why not?
2. What other questions would be appropriate in obtaining the history?
Has the patient has prior surgeries requiring a breathing machine? Have other family members had problems from anesthesia? Has he or a family member had a fever or muscle pain after running or exercise?
3. Is additional workup required? Why or why not?
Preparation for operation
1. Should a muscle biopsy be obtained prior to strabismus surgery? Why or why not?
2. What test for muscle biopsy should be ordered?
3. Is dantrolene prophylaxis required?
B. Intraoperative course
1. Would you monitor this child differently than a normal healthy 3-year old? Why?
2. What additional monitors would you use? Explain.
II. Anethestic equipment/circuit
1. What circuit and vaporizers would you use? Why?
2. Would you take any special precautions with the circuit? Why or why not?
1. The parent requests no IV be placed until anesthesia is induced. Do you agree?
2. Why or why not?
3. What anesthetic induction would you use? Why?
IV. Anesthetic maintenance
1. What agents will you use to maintain anesthesia?
2. Will you avoid any drugs? Explain.
1. Thirty-minutes after induction, you notice a gradual decrease in oxygen saturation, from 100% to 90%. What is your differential diagnosis?
The major causes of hypoxemia are low inspired FIO2, hypoventilation, shunt, ventilation/perfusion mismatch, decreased cardiac output, decreased oxygen carrying capacity, and diffusion abnormalities.
Decreased FIO2 may be caused by low oxygen mixtures, depleted oxygen supply, or circuit disconnection. Muscular paralysis or the ventilatory depressant effects of any anesthetic gases can also decrease oxygen content. Shunt fraction to thebesian and bronchial veins can be increased by liver failure, sepsis, arteriovenous malformations, pulmonary emboli, and right-to-left shunts. Ventilation/perfusion mismatching can occur from atelectasis, positioning, endobronchial or one-lung ventilation, bronchospasm, pneumonia, mucous plugging, acute respiratory distress syndrome, and airway obstruction. Decreased cardiac output or oxygen carrying capacity can lead to hypoxia, as well as severe pulmonary disease such as pulmonary fibrosis, pulmonary edema, and acute respiratory distress syndrome.
2. Could this hypoxemia be due to kyphoscoliosis?
3. How would you confirm your diagnosis?
4. What is your management?
5. You note that the pulse rate has slowed from 110 to 70 bpm. What can cause this?
6. What is your management?
1. If dantrolene were used intraoperatively, would you continue it postoperatively? Explain.
1. Despite aggressive fluid management, the nurse reports less than 5 ml of urine during each of the first two hours postoperatively. What is your differential diagnosis?
2. What is your management?
1. Would you discharge this patient to home, the ward, or to the intensive care unit? Explain.