Asymptomatic profound oxyhemoglobin desaturation following interscalene block in a geriatric patient.

BACKGROUND AND OBJECTIVES

Interscalene block can be chosen for complete anesthesia for shoulder surgery. Phrenic nerve block occurs with almost all interscalene blocks, but is well tolerated in most patients. This may not be the case in selected geriatric patients.

METHODS

The patient is a 90-year-old female with osteoarthritis of the left shoulder scheduled for total shoulder anthroplasty. Past medical history revealed hypertension, mild mitral valve insufficiency, and a remote episode of congestive heart failure. She underwent interscalene block with 40 mL of 1.4% mepivacaine, 1:200,000 epinephrine freshly added, alkalinized with sodium bicarbonate.

RESULTS

The onset of the block was rapid and complete. The patient had minimal intravenous sedation (0.5 mg midazolam) and was resting comfortably with a respiratory rate of 12-14 breaths/min. Approximately 5 minutes after the injection of local anesthetic, the patient was noted to be alert, cyanotic, denying dyspnea, with an oxygen saturation of 75-85%. A chest radiograph revealed elevation of the ipsilateral hemidiaphragm and no pneumothorax or other pathology. Despite supplemental oxygen by face mask, desaturation persisted and general anesthesia was induced. On emergence from anesthesia, the patient had a complete interscalene block. Repeat chest radiograph after resolution of the block revealed return of hemidiaphragm position and no other pathology. The patient was extubated in the recovery room without difficulty. Following extubation the patient demonstrated stable respirations and normal oxyhemoglobin saturation.

CONCLUSIONS

Ipsilateral phrenic nerve paralysis caused significant respiratory compromise in an elderly patient without known significant pulmonary disease.