Orthopedics

Feature Article 

Prospective Evaluation of Cognitive Outcomes After Anesthesia for Patients in the Beach Chair Position

Karim Boukhemis, MD; Michael Perez, MD; Erik Olness, MD; Jeremy L. Hensley, MD; Jake Lindstrom, CRNA; E. Barry McDonough, MD; George K. Bal, MD, FACS

Abstract

The beach chair position has been popularized for shoulder surgeries, particularly those involving arthroscopy. Several published case reports and studies have raised concerns for neurologic complications related to anesthesia for surgery performed with patients in the beach chair position. The question has been raised whether cerebral perfusion monitoring should be used routinely to minimize these potential complications. This prospective study evaluated cognitive outcomes in patients who underwent anesthesia in the beach chair position. Patients were randomized to 2 groups. In group 1, the anesthesiologist was blinded to the cerebral monitoring and could treat based only on mean arterial pressure (MAP). In group 2, the anesthesiologist was aware of the results of the cerebral monitoring and could treat any desaturation events. All patients were evaluated pre- and postoperatively with a cognitive assessment tool. A total of 80 patients were enrolled in the study, with 40 patients in each group. There were no significant differences regarding age, body mass index, or American Society of Anesthesiologists score. Only 3 desaturation events occurred with no significant change in cognitive function. The findings indicate no advantage to cerebral perfusion monitoring during anesthesia for surgery performed with patients in the beach chair position as long as MAP is maintained within strict limits. Although little is known about the level of cerebral desaturation that will result in cognitive dysfunction, it may likely be related to MAP and cerebral perfusion. The findings of this study reinforce the need for careful monitoring of MAP during surgery and dispute the need for additional expensive monitoring devices. [Orthopedics. 2020; 4X(X):xx–xx.]

Abstract

The beach chair position has been popularized for shoulder surgeries, particularly those involving arthroscopy. Several published case reports and studies have raised concerns for neurologic complications related to anesthesia for surgery performed with patients in the beach chair position. The question has been raised whether cerebral perfusion monitoring should be used routinely to minimize these potential complications. This prospective study evaluated cognitive outcomes in patients who underwent anesthesia in the beach chair position. Patients were randomized to 2 groups. In group 1, the anesthesiologist was blinded to the cerebral monitoring and could treat based only on mean arterial pressure (MAP). In group 2, the anesthesiologist was aware of the results of the cerebral monitoring and could treat any desaturation events. All patients were evaluated pre- and postoperatively with a cognitive assessment tool. A total of 80 patients were enrolled in the study, with 40 patients in each group. There were no significant differences regarding age, body mass index, or American Society of Anesthesiologists score. Only 3 desaturation events occurred with no significant change in cognitive function. The findings indicate no advantage to cerebral perfusion monitoring during anesthesia for surgery performed with patients in the beach chair position as long as MAP is maintained within strict limits. Although little is known about the level of cerebral desaturation that will result in cognitive dysfunction, it may likely be related to MAP and cerebral perfusion. The findings of this study reinforce the need for careful monitoring of MAP during surgery and dispute the need for additional expensive monitoring devices. [Orthopedics. 2020; 4X(X):xx–xx.]

The beach chair position is widely used for shoulder surgeries and has been described as “allowing better visualization, decreased blood loss, and shorter operative times.”1 However, some case reports in the literature have identified potential complications associated with this surgical position. Adverse neurologic outcomes ranging from cranial nerve injury to cerebral infarction occurring in relatively healthy individuals have been reported,2 sparking investigative interest in this area. One theorized cause was that resultant cerebral hypotension occurred secondary to placing the patient in the beach chair position.3

One commonly used anesthesia protocol is to maintain the mean arterial blood pressure (MAP) at a level greater than 60 mm Hg or within 20% of the preoperative baseline value. Despite maintaining MAP within these ranges, detrimental neurologic deficits and cognitive dysfunction have occurred in patients undergoing surgery in the beach chair position. Consequently, new technologies have been used to monitor cerebral perfusion. One such technology is near-infrared spectroscopy (NIRS), a noninvasive monitoring modality that measures cerebral oxygen saturation and that has been hypothesized as providing an early warning sign of decreased cerebral perfusion in procedures with a high risk of adverse neurologic events.4 A separate tool used to assess cognitive function is the Mini-Mental State Examination (MMSE). This brief but thorough test has been used to detect changes in cognitive abilities. The MMSE, which has been reported to be one of the most accurate methods for recognizing a variation in mental status, can be performed in the office.5 These 2 modalities, when used synergistically, may help identify a clinically significant cognitive decline in patients undergoing procedures in the beach chair position.

In this randomized, prospective, blinded clinical study, a standardized anesthesia protocol was used to maintain MAP during surgery performed with patients in the beach chair position. The current authors hypothesized that if MAP was maintained, then NIRS monitoring would not change intraoperative anesthesia management and would not affect the postoperative cognitive outcomes of patients who underwent surgery in the beach chair position. In addition, a secondary investigation examined the actual incidence of cerebral desaturation events (CDEs) recorded by NIRS occurring in patients placed in the beach chair position if MAP was strictly maintained.

Materials and Methods

After receiving institutional review board approval, patients were enrolled in this prospective, randomized, controlled study. A preoperative power analysis was performed; it was thought that 80 patients would be adequate based on review of other studies. All patients 18 years and older who were scheduled to undergo elective shoulder surgery in the beach chair position were considered for study inclusion. Standard patient demographic information included American Society of Anesthesiologists (ASA) scores, body mass index (BMI), age, and length of surgery.

Exclusion criteria were patients younger than 18 years or those who had a history of traumatic brain injury, transient ischemic attack, cerebrovascular accident, any apparent clinical neurologic dysfunction, carotid artery stenosis, known vascular malformation in the head, inability to measure blood pressure in the opposite upper extremity, malignant hyperthermia, or an MMSE preoperative score of 23 or less. All patients were monitored for CDEs throughout surgery using NIRS. For all patients, MAP was maintained within 20% of their individual baselines. A single faculty anesthesiologist was assigned to the study cases to control for inter-provider variability.

Participants were randomized to one of two groups. For group 1, the anesthesiologist was blinded to the NIRS results, and MAP was maintained within 20% of baseline using standard anesthesia monitoring equipment. For group 2, the anesthesiologist was able to monitor and maintain the NIRS intraoperatively to within 20% of baseline, in addition to maintaining each patient's MAP within 20% of baseline. A baseline MMSE was administered to all patients prior to surgery; the MMSE was administered again at the first postoperative visit, approximately 7 to 10 days after surgery. A score below 24 was deemed as mild cognitive impairment; any individual who did not have a preoperative baseline score of at least 24 was eliminated from the study. Postoperatively, patients who had a decrease of more than 2 points on the MMSE or who had a score below 24 points were deemed to have a decline in cognitive function.

All patients received interscalene peripheral nerve blocks prior to the procedure for postoperative analgesia. Sedation for the nerve block was left to the discretion of the Anesthesia Pain Service. A baseline blood pressure was obtained in the preoperative holding area, and patients then were transported to the operating room. Patients were placed supine on the operative table. Prior to oxygenation, NIRS monitors were placed and baseline values were recorded. The choice of the anesthesia induction technique was based on a protocol established by the attending anesthesiologist author (E.O.), with some variability based on patient comorbidities. Choice of airway management technique (laryngeal mask airway [LMA] vs endotracheal tube) also was left to the discretion of the attending anesthesiologist author. Anesthesia was maintained with a volatile agent in 50% oxygen.

Standard ASA monitors were used in conjunction with NIRS. On the operative day, the treating anesthesiologist author determined whether LMA or endotracheal intubation was necessary. Following anesthesia induction and stabilization of vital signs, the baseline NIRS data were recorded. Patients then were placed in the beach chair position at 60° from horizontal using a dedicated beach chair table. Arthroscopy portals were determined by the treating surgeon at the time of surgery depending on the shoulder injury. Data recorded at 3-minute intervals included NIRS (left and right), blood pressure, MAP, heart rate, temperature, respirations, and end-tidal carbon dioxide concentration. Preinduction vital signs as well as postinduction vital signs (following return of hemodynamic stability) were recorded. The NIRS values were recorded for the extent of the procedure until transfer of the patient to the recovery bed.

For patients in group 1, the anesthesiologist was blinded to the NIRS data. Baseline blood pressure was obtained in the preoperative area. Hypotension was defined as less than 60 mm Hg or greater than 20% change from baseline and was treated with intravenous fluid administration and 5 mg of ephedrine or 60-µg phenylephrine intravenous bolus, titrated as needed.

For patients in group 2, the anesthesiologist treated patients according to the NIRS data. The NIRS alarm sounded if regional cerebral oxygen saturation (rSO2) fell below 80% of baseline. In that event, treatment was to: (1) decrease ventilation to PaCO2 of 40 or greater, (2) treat hypotension as above, and (3) increase fraction of inspired oxygen (FiO2).

Statistical analysis was performed using one-way analysis of variance (ANOVA) with t scores, as well as the Wilcoxon/Kruskal–Wallis test. P<.05 was considered statistically significant.

Results

A total of 80 patients was enrolled in the study; 26 were female and 54 were male. Average ASA score was 2.28 (range, 1–3). Average BMI was 31.14 kg/m2 (range, 17.74–64.5 kg/m2), and average age was 47.7 years (range, 18–74 years). Average anesthesia time from induction to awakening was 75.6 minutes (range, 38–154 minutes).

Three patients (2 males and 1 female) met the criteria for desaturation with the initial requirements; these 3 patients had no significant change in pre- and postoperative MMSE score. In fact, the change in MMSE score in patients with CDEs was almost identical to the MMSE score in patients without CDEs (−0.3 and −0.2, respectively). Overall, the total preoperative and postoperative MMSE scores for all 80 patients were 28.425 and 28.637, respectively. These results were not statistically significant because of the low occurrence of CDEs.

There was no correlation between group 1 (blinded to NIRS data) and group 2 (able to use NIRS data) regarding the final MMSE testing. For patients who had a desaturation event, the one aspect that was statistically significant was whether they underwent LMA or intubation (P=.008). All 3 patients who sustained a desaturation event underwent intubation. For the patients who did not have CDEs, 22 patients were intubated and 55 underwent LMA. The ASA scores did not differ significantly; for the 3 patients who had desaturation, the ASA score was 2.3 compared with 2.2 for the patients who did not have desaturation. The average age of the 3 patients with CDEs was 47.6 years compared with 47.5 years for the patients who did not have CDEs.

In an effort to identify more desaturation events, the threshold criteria for identifying a CDE was changed from a 20% drop from baseline NIRS to a 15% drop. With this change, the total desaturation events increased to 13 patients, which included the previous 3 patients. Among these 13 patients, 3 of the CDEs actually occurred in patients in the supine position prior to being placed into the beach chair position.

There was no significant change in MMSE when comparing the larger desaturation group with the remaining 67 patients (P=.5063). There was no significant difference in any of the other measured parameters. However, it was again noted that a higher number of CDEs occurred with intubation. Of the 13 patients with CDEs, 11 (84.6%) patients were intubated for the surgical procedure compared with 25 (31.2%) of 80 patients who were intubated for the entire study population.

Discussion

The use of the beach chair position during surgical procedures has been associated with potential complications and impairment in cognitive function. These events have been related to CDEs that occur with decreases in MAP. Several reports in the literature have demonstrated that the intraoperative use of NIRS for monitoring cerebral desaturation has been an effective modality.6,7 Pollard et al6 studied NIRS and reported this method provides information on the occurrence of cerebral desaturation that is as accurate as invasive methods. However, NIRS monitoring is expensive and has yet to prove any benefit in preventing the occurrence of these events.

The authors' hypothesis was that a focus on maintaining MAP during surgery in the beach chair position would decrease the prevalence of CDEs. In this study, using a strict anesthesia protocol and a decline of 20% from baseline NIRS data, the rate of CDEs was 3.75% (3 of 80 patients). This finding conflicts with the results of another study that used the same criteria. In their study, Moerman et al8 reported 15 of 20 patients (80%) sustained desaturation when using a cerebral desaturation drop of 20%. However, their study differed from the current study in that their only exclusion criterion was clinically apparent neurologic or cognitive dysfunction. In addition, the anesthesiologist was blinded to the NIRS data and had no set anesthesia protocol.

Another point of evaluation in the current study was that all patients were tested cognitively both pre- and postoperatively (7 to 10 days) using the MMSE. The MMSE was chosen because it is widely used by the neurologic community to determine mental status changes.5 The MMSE is a brief 30-point questionnaire that is used to screen for cognitive impairment; the MMSE commonly is used to screen for dementia. The MMSE also is used to estimate the severity of cognitive impairment and to follow the course of cognitive changes in an individual over time, thus making it an effective way to document an individual's response to treatment. In approximately 10 minutes, the MMSE evaluates functions including arithmetic, memory, and orientation.

Casati et al4 used the MMSE at followup after recording NIRS desaturation in patients who underwent abdominal surgery. They considered cognitive function to be declined if the MMSE dropped 2 or more points from baseline. The current study used a decline in the MMSE of greater than 2 points or if the score fell at or below 23, irrespective of the initial MMSE score, as evidence of a change in cognitive function. Casati et al4 also reported that 20% of patients in their control group and 23% in their treatment group sustained a desaturation. Although their sample size was 122 patients and the sample size in the current study was 80, the current authors did not have the same occurrence of desaturation events.

Gillespie et al1 evaluated controlled hypotension in the beach chair position. This study closely resembled the current study's lack of desaturation results. They reported that only 3 of 52 patients sustained a desaturation event; however, desaturation was determined by electroencephalography and not by NIRS. The authors further concluded that a drop in systolic blood pressure to less than 90 mm Hg, which occurred in 27 (52%) patients, did not correlate with evidence of a cerebral desaturation. Patients also were evaluated with a follow-up MMSE, and no decline in cognitive function was observed in any patient.

Lee et al9 reported comparable results with the beach chair position strictly limited to arthroscopic surgeries. Similar to the current study, Lee et al9 reported 2 episodes of CDEs in 27 patients. These 2 patients sustained a decrease in MAP below 60 mm Hg, which was quickly corrected. Their study only had a single group, and the anesthesia team was not blinded. The MMSE was administered preoperatively and 1 day postoperatively, with a positive drop in MMSE determined to be 2 or greater. Despite strict MMSE criteria, there was no decrease in cognitive function. Data were recorded at 5-minute intervals.9

Jo et al10 examined preoperative variables to determine the likelihood of a hypotensive event occurring in the beach chair position. In their study of 40 patients, 15 patients developed hypotension after being placed in the beach chair position. Their definition of hypotension was a MAP of less than 60 mm Hg or less than 80% of baseline; they did not use NIRS to determine whether a CDE had occurred. They concluded that preinduction values of cardiac index, stroke volume index, and postinduction value of stroke volume variation were the best predictors of hypotension in the beach chair position.

The current study had several strengths. The study was randomized, prospective, and blinded. A single team provided anesthesia for the surgeries and used a standardized protocol. All of the patients underwent preoperative and postoperative cognitive assessment with an accepted evaluation tool. However, there also were several shortcomings to the study. Even with 80 patients enrolled, only a few CDEs occurred, making it difficult to draw certain conclusions.

In reviewing other studies, the number of patients was comparable with a higher incidence of reported CDEs. The initial power analysis determined that 80 patients would be adequate based on this information. However, the actual incidence of CDEs was low, suggesting a larger patient population might provide more information. It appeared that intubation may be related to the occurrence of CDEs. Other than the anesthesia team's concern regarding comorbidities, there were no set criteria to determine the use of LMA or intubation anesthesia. As mentioned previously, the CDEs observed with intubation may have been related to a patient's comorbidities rather than the actual intubation. Future studies may be beneficial in evaluating this finding.

Conclusion

The authors believe that there is a relevant change in blood pressure that occurs with patients placed in the beach chair position. Although the NIRS can identify possible CDEs, their occurrence does not necessarily correlate with postoperative cognitive dysfunction. In fact, from these data, it appears that diligent monitoring of a patient's MAP may be the most reliable way to prevent a CDE. Findings also indicated that potentially debilitating CDEs can occur even with patients in the supine position. Although more CDEs occurred in intubated patients, it is unclear whether this was due to intubation or whether these patients were higher risk; it also is possible that not enough CDEs occurred to identify intubation as a real difference. Findings of this study indicate strict maintenance of MAP, particularly in the beach chair position, is adequate to protect cerebral oxygenation, and there is no added benefit with NIRS monitoring. However, the best method for monitoring patients should be determined on a case-by-case basis.

References

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Authors

The authors are from the Department of Orthopaedics (KB, MP, EBM, GKB) and the Department of Anesthesiology (EO, JLH, JL), West Virginia University, Morgantown, West Virginia.

The authors have no relevant financial relationships to disclose.

Correspondence should be addressed to: George K. Bal, MD, FACS, Department of Orthopaedics, West Virginia University, PO Box 9196, Morgantown, WV 26506-9196 ( gbal@hsc.wvu.edu).

Received: August 30, 2018
Accepted: January 02, 2019
Posted Online: November 06, 2019

10.3928/01477447-20191031-09

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