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Oral case 21

Created: 25/9/2004

A 10-year old 40 kg mentally retarded female is scheduled for outpatient surgery for multiple dental extractions and restorations, secondary to severe caries. She has a seizure disorder, and takes phenobarbital 15 mg tid and Dilantin 80 mg tid. Blood pressure is 105/60 mm Hg, pulse is 104 bpm, respirations are 14, and hemoglobin is 9.2

 Preoperative evaluation

I. Outpatient surgery

1. Is this patient suitable for outpatient surgery? Why or why not?

 Mental retardation

1. What specific anesthetic problems does her mental retardation pose?

2. How would you evaluate for these problems?

3. Would you give premedication to this patient? Why or why not?

 Seizure disorder

1. What is the anesthetic significance of the seizure disorder?

2. What is the anesthetic significance of her antiseizure medications?


1. Does her hemoglobin level concern you?

2. How do you evaluate the cause of anemia?

3. Would you treat this anemia preoperatively?

 Intraoperative course


1. Is electroencephalogram monitoring indicated? Explain.

2. How does a pulse oximeter work?

It is based on the Beer-Lambert law, and spectrophotometric analysis. The incident light source passes through the finger, being transmitted across a distance to the opposite side. A certain concentration of hemoglobin is constant, as is an extinction coefficient. Mathetatical calculations then convert this value to oxygen saturation.

2. Does anemia affect pulse oximetry? Explain.

Pulse oximetry is fairly reliable between an oxygen saturation of 80 to 100%, and is not affected by anemia per se.

3. What are factors that limit its accuracy?

Factors, which limit accuracy, include methemoglobin, carboxyhemoglobin, nail polish, bright light, vasoconstriction, shivering, and motion.

3. Does anemia affect the development of cyanosis? Explain.

 Induction of anesthesia

1. How would you induce anesthesia?

2. The child refuses a mask and you have tried three times unsuccessfully to secure an IV. She is now agitated. How would you proceed?

3. Is ketamine an option? Why or why not?

 Maintenance of anesthesia

1. What agents would you use for maintenance of anesthesia?

2. How does the seizure disorder influence your choices?

3. How does the anti-seizure medication influence your choices?

4. Would the anti-seizure medication alter the anesthetic requirements? Explain.


1. During an inhalation anesthetic with isoflurane/nitrous oxide and with spontaneous ventilation, the pulse oximetry decreases from 99% to 96%. Does this concern you? Explain.

2. What is your management?

3. Pulse oximeter decreases to 89%. How would you manage it now?

 Postoperative care

I. Airway

1. Immediately after extubation, you place a mask on the patient and note that the anesthetic bag is not moving. What is your differential diagnosis?

2. How would you now proceed?

II. Seizure

1. Twenty minutes artery recovery room arrival, the patient develops a grand mal seizure. How would you manage this?

2. What would your management be after the seizure is terminated?

III. Discharge

1. Would you discharge this patient to home? Explain.

2. How would you determine time of discharge?

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