Using regional anesthesia and sedation, rather than general anesthesia, for patients undergoing shoulder surgery in the beach-chair position reduces the risk of cerebral deoxygenation, according to study results presented by Jason L. Koh, MD, of the NorthShore University Health System, during the American Shoulder and Elbow (ASES) Specialty Day. This suggests that avoiding the use of general anesthesia may reduce the risk of ischemic neurologic injury in this patient population.

The research, summarized in “Cerebral Oxygenation in the Beach Chair Position: A Prospective Study on the Effect of General Anesthesia Compared to Regional Anesthesia and Sedation,” earned the 2012 ASES Charles S. Neer Award for Dr. Koh and his colleagues.

The seated beach-chair position is commonly used for arthroscopic and open shoulder surgeries and is associated with a low risk of complications. However, noted Dr. Koh, rare catastrophic neurologic events such as blindness, stroke, coma, and even death have been reported in patients operated on in the beach-chair position under general anesthesia.

According to Dr. Koh, patients who are in the seated position can experience a ‘waterfall effect,’ causing decreased flow to the brain. Awake patients are able to compensate and are able to maintain cerebral perfusion. However, patients under general anesthesia are unable to fully activate their sympathetic response and are subject to the vasodilating effects of anesthetic medications and limited cerebral autoregulation, resulting in relative cerebral hypoperfusion.

“We hypothesized, therefore, that patients operated on in the beach-chair position would have better cerebral oxygenation with a regional block and sedation than with general anesthesia,” he said.

Study materials, methods
The prospective study involved 60 patients undergoing elective shoulder surgery. After conferring with the surgeon and anesthesiologist, the patients were enrolled in the following groups:

• interscalene block (ISB) anesthesia and sedation with spontaneous ventilation (AWAKE) (n = 30)
• ISB with general anesthesia with mechanical ventilation (ASLEEP) (n = 30)
• Patients were excluded from the study for the following reasons:
• pre-existing cerebrovascular disease or orthostatic hypotension
• age younger than 18 years
• history of allergy to local anesthetics
• pre-existing coagulation abnormalities
• American Society of Anesthesiologists (ASA) class IV or V
• failure of the ISB in the holding area

The researchers obtained baseline and intraoperative data on all patients. Baseline data were obtained in the operating room, with patients in the supine position and breathing room air. Patients in both cohorts were demographically similar with regard to age, sex, height, weight, pre-existing medical conditions, and ASA class; baseline hemodynamic and oxygenation parameters were also similar.

Intraoperatively, cerebral tissue oxygen saturation (SctO2) and hemodynamic parameters including mean arterial pressure (MAP), heart rate (HR), and arterial oxygen saturation (SpO2) were obtained and recorded every 3 minutes. To minimize the risk of cerebral desaturation events, MAP and SctO2 values less than 20 percent of baseline were treated according to prearranged intervention protocols.

Aldrete scores measuring consciousness, breathing, blood pressure, oxygenation, and motor function were collected on arrival and every 15 minutes in the recovery room.

Results
Anesthesia time was longer in the ASLEEP cohort by a mean of 18 minutes, which was likely related to induction and emergence from the general anesthesia, Dr. Koh noted. The researchers found no significant differences in HR and SpO2 between the two cohorts at any time; MAP was also similar at all time points but one. Intervention for decreases in MAP, however, occurred in 73 percent of ASLEEP patients, compared to 10 percent of AWAKE patients (P < 0.001).

The researchers also found that SctO2 values were lower in the ASLEEP group than in the AWAKE group throughout the intraoperative period (P > 0.0001). Intervention for decreases in SctO2 occurred in 43 percent of ASLEEP patients, compared to 0 percent in the AWAKE group (P < 0.001).

In addition, the incidence of cerebral deoxygenation events (CDEs) was 56.7 percent in the ASLEEP group, compared to 0 percent in the AWAKE group (P < 0.001); the mean number of CDEs per patient was 2.97 in the ASLEEP cohort and 0 in the AWAKE cohort (P < 0.001). The total number of CDEs was also significantly higher in the ASLEEP cohort versus the AWAKE cohort (89 and 1, respectively; P < 0.001)

“We found that more than half of the ASLEEP patients had CDEs where the oxygen supply to the brain was decreased, but that all AWAKE patients maintained their cerebral oxygenation,” said Dr. Koh. “The ASLEEP patients also had lower Aldrete scores in the recovery room and a longer time to meet discharge criteria. No permanent neurologic impairment was seen in either group.”

He added, “Use of a regional block and sedation compared to general anesthesia decreases the risk of cerebral deoxygenation for patients in the beach-chair position, which may reduce the risk of neurologic events. We recognize, however, that the regional block and sedation may not be appropriate at times, due to areas of the shoulder that are not anesthetized, the need for muscle relaxation, the risk of airway obstruction, or the prolonged nature of the case.”

Dr. Koh’s coauthors include Steven D. Levin, MD (no conflicts); Eric L. Chehab, MD (no conflicts); and Glenn Murphy, MD (CASMED). Dr. Koh reports ties to Aesculap/B.Braun; Aperion; and Arthrex, Inc.

Maureen Leahy is assistant managing editor of AAOS Now. She can be reached at leahy@aaos.org

Bottom Line

• This prospective study evaluated the effects of regional anesthesia and sedation and general anesthesia on cerebral oxygenation in patients undergoing surgery in the beach-chair position.
• Unlike general anesthesia patients, patients treated with regional anesthesia and sedation demonstrated essentially no cerebral deoxygenation events.
• Avoiding the use of general anesthesia in patients undergoing surgery in the beach-chair position may help decrease the risk of catastrophic neurologic injury.