Efficacy and safety of intraoperative controlled hypotension: a systematic review and meta-analysis of randomised trials.

BACKGROUND: Intraoperative controlled hypotension improves surgical field visibility by reducing blood loss (efficacy) but poses potential risks linked to organ hypoperfusion (safety). The use of controlled hypotension persists despite increasing evidence of associations between intraoperative inadvertent hypotension and adverse outcomes. Therefore, we tested the hypothesis that the focus and results of intraoperative controlled hypertension research differ across anaesthesia and surgery investigators because of differing priorities. METHODS: We systematically reviewed randomised trials comparing controlled hypotension with usual care with trials categorised by investigators' affiliation. RESULTS: We identified 48 eligible trials, of which 37 were conducted by anaesthesia investigators and 11 by surgery investigators. For the primary outcome, 54% of the anaesthesia-led trials focused on safety, whereas all (100%) surgery-led trials focused on efficacy (P=0.004). Compared with usual care, mean arterial pressure in controlled hypotension was 23% (95% confidence interval [CI] 17-29%) lower in anaesthesia trials and 30% (95% CI 14-37%) lower in surgery trials; estimated blood loss was 44% (95% CI 30-55%) less in anaesthesia trials and 38% (95% CI 30-49%) less in surgery trials. Overall, blood loss was reduced by 43% (95% CI 32-53%), and trial sequential analysis supported an efficacy conclusion. Mean arterial pressure and estimated blood loss reductions were associated (R2=0.41, P=0.002). All trials were underpowered for safety outcomes, and none adequately evaluated myocardial or renal injury. CONCLUSIONS: Anaesthesia researchers prioritised safety outcomes, whereas surgery researchers emphasised efficacy in controlled hypotension trials. Controlled hypotension significantly reduces blood loss. In contrast, safety outcomes were poorly studied. Given increasing observational evidence linking inadvertent hypotension to myocardial and renal injury, the safety of controlled hypotension remains to be addressed. SYSTEMATIC REVIEW PROTOCOL: PROSPERO (CRD42023450397).

Use and Outcomes of Peripheral Vasopressors in Early Sepsis-Induced Hypotension Across Michigan Hospitals: A Retrospective Cohort Study.

BACKGROUND: Vasopressors traditionally are administered via central access, but newer data suggest that peripheral administration may be safe and may avoid delays and complications associated with central line placement. RESEARCH QUESTION: How commonly are vasopressors initiated through peripheral IV lines in routine practice? Is vasopressor initiation route associated with in-hospital mortality? STUDY DESIGN AND METHODS: This retrospective cohort study included adults hospitalized with sepsis (November 2020-September 2022) at 29 hospitals in the Michigan Hospital Medicine Safety Consortium, a Collaborative Quality Initiative sponsored by Blue Cross Blue Shield of Michigan. We assessed route of early vasopressor initiation, factors and outcomes associated with peripheral initiation, and timing of central line placement. RESULTS: Five hundred ninety-four patients received vasopressors within 6 h of hospital arrival and were included in this study. Peripheral vasopressor initiation was common (400/594 [67.3%]). Patients with peripheral vs central initiation were similar; BMI was the only patient factor associated independently with initiation route (adjusted OR [aOR] of peripheral initiation [per 1-kg/m2 increase], 0.98; 95% CI, 0.97-1.00; P = .015). The specific hospital showed a large impact on initiation route (median OR, 2.19; 95% CI, 1.31-3.07). Compared with central initiation, peripheral initiation was faster (median, 2.5 h vs 2.7 h from hospital arrival; P = .002), but was associated with less initial norepinephrine use (84.3% vs 96.8%; P = .001). We found no independent association between initiation route and in-hospital mortality (32.3% vs 42.2%; aOR, 0.66; 95% CI, 0.39-1.12). No tissue injury from peripheral vasopressors was documented. Of patients with peripheral initiation, 135 of 400 patients (33.8%) never received a central line. INTERPRETATION: Peripheral vasopressor initiation was common across Michigan hospitals and had practical benefits, including expedited vasopressor administration and avoidance of central line placement in one-third of patients. However, the findings of wide practice variation that was not explained by patient case mix and lower use of first-line norepinephrine with peripheral administration suggest that additional standardization may be needed.

Can subclavian/infraclavicular axillary vein collapsibility index predict spinal anesthesia-induced hypotension in cesarean-section operations?

OBJECTIVE: Spinal anesthesia-induced hypotension (SAIH) is relatively common in pregnant women and has serious maternal and fetal side effects. In patients who are hypovolemic during spinal anesthesia, there may be a significant decrease in blood pressure caused by the decrease in preload. Subclavian vein sonography is a useful method for evaluating preoperative intravascular volume status. This study aimed to evaluate the efficacy of the pre-operative subclavian vein or infraclavicular axillary vein (SCV-AV) collapsibility index for predicting SAIH in cesarean-section (C-section). PATIENTS AND METHODS: In this prospective observational study, 82 women undergoing elective C-sections were recruited. Sonographic evaluation of SCV-AV was assessed before spinal anesthesia. After spinal anesthesia, changes in blood pressure were noted. The main outcome was the association between the SCV-AV measurements (diameter and collapsibility index) and SAIH. RESULTS: Hypotension developed in 53 (64%) patients after spinal anesthesia. The collapsibility index of the SCV-AV during spontaneous breathing and deep inspirium was not a significant predictor of a decrease in mean blood pressure (MBP) after spinal anesthesia (p<0.979, p<0.380). CONCLUSIONS: It was found that the SCV-AV collapsibility index is not a predictor of SAIH in pregnant women undergoing elective C-sections.

Sevoflurane-induced hypotension causes cognitive dysfunction and hippocampal inflammation in mice.

Sevoflurane commonly adopted for anesthetic in clinical practice, however, its influences on cerebral blood flow and cognitive function remain controversial. Herein, the sevoflurane-induced hypotension on arterial blood pressure, cerebral blood flow, cognitive function, and hippocampal inflammation was investigated in mice. A significant decrease in arterial blood pressure and cerebral blood flow was indicated by the sevoflurane anesthesia treatment. Moreover, sevoflurane-induced hypotension was associated with the impaired cognitive function and the increased levels of NLRP3 inflammasome activation and oxidative stress in hippocampus. These findings suggest that sevoflurane-induced hypotension may lead to the cognitive dysfunction and hippocampal inflammation.

Leg Compression Versus Control for Prevention of Spinal Anesthesia Induced Hypotension in Elective Cesarean Delivery: A Meta-Analysis of Randomized Controlled Trials.

PURPOSE: The aim of this meta-analysis was to assess the effectiveness of leg compression versus control in preventing spinal anesthesia induced hypotension during cesarean delivery. DESIGN: A meta-analysis of randomized controlled trials (RCTs). METHODS: PubMed, Embase, Web of Science and CENTRAL were searched for RCTs that compared leg compression with control for prevention of hypotension in patients undergoing elective cesarean delivery under spinal anesthesia. The primary outcome was the incidence of hypotension. Subgroup analysis was performed according to leg compression methods. Secondary outcomes included nausea and vomiting, the number of vasopressor requirement, and the rates of neonatal Apgar scores ≤7 and umbilical cord blood pH ≤ 7.2. FINDINGS: Twelve studies involving 787 patients were included in this meta-analysis. There was a significant reduction of the incidence of hypotension with leg compression versus control (RR 0.45, 95% CI 0.32 to 0.62, I2 = 81%). Subgroup analysis suggested that leg wrapping may be more effective in preventing hypotension compared with elastic stockings and sequential compression mechanical devices. Leg compression also reduced maternal nausea and vasopressors requirement, but did not impact on neonatal outcomes. CONCLUSIONS: Leg compression, especially leg wrapping, decreases the incidence and severity of hypotension after spinal anesthesia in caesarean delivery. As a simple, non-pharmacologic and cost-effective intervention, leg wrapping can be used for prevention of spinal anesthesia induced hypotension in caesarean delivery, either alone or in combination with vasopressors.

Neonatal outcomes following phenylephrine or norepinephrine for treatment of spinal anaesthesia-induced hypotension at emergency caesarean section in women with fetal compromise: a randomised controlled study.

BACKGROUND: Norepinephrine is as effective as phenylephrine for management of spinal anaesthesia-induced hypotension. Most of the studies comparing these vasopressors have been conducted in healthy pregnant women undergoing elective caesarean section. In the current study, we tested the null hypothesis that there is no difference in neonatal outcome when phenylephrine or norepinephrine is used to treat spinal anaesthesia-induced hypotension in women undergoing emergency caesarean section for fetal compromise. METHODS: Patients undergoing caesarean section for fetal compromise who developed spinal anaesthesia-induced hypotension were randomised to receive phenylephrine 100 µg or norepinephrine 8 µg for treatment of each hypotensive episode, defined as systolic blood pressure <100 mmHg. Umbilical cord arterial and venous blood samples were obtained for blood gas analysis. The primary outcome measure was umbilical artery pH. RESULTS: One hundred patients (50 in each group) were studied. There was no significant difference in umbilical artery pH between the two groups (mean difference 0.001; 95% CI -0.032 to 0.034). The number of hypotensive episodes, vasopressor boluses required, the incidence of bradycardia, heart rate and blood pressure trends following vasopressor administration, and the incidence of nausea/vomiting were not significantly different between groups. CONCLUSION: Phenylephrine 100 µg and norepinephrine 8 µg were not significantly different in terms of neonatal outcome when administered as intravenous boluses for treatment of spinal anaesthesia-induced hypotension in parturients undergoing emergency caesarean sections for fetal compromise.

Controlled hypotension during neuraxial anesthesia is not associated with increased odds of in-hospital common severe medical complications in patients undergoing elective primary total hip arthroplasty - A retrospective case control study.

INTRODUCTION: The use of controlled hypotension during neuraxial anesthesia for joint arthroplasty is controversial. We conducted a large institutional database analysis to assess common in-hospital complications and mortality of patients undergoing primary total hip arthroplasty (THA) under controlled hypotension and neuraxial anesthesia. METHODS: We conducted a large retrospective case control study of 11,292 patients who underwent primary THA using neuraxial anesthesia between March 2016 and May 2019 in a single institution devoted to musculoskeletal care. The degree and duration of various mean arterial pressure (MAP) thresholds were analyzed for adjusted odds ratios with composite common severe complications (in-hospital myocardial infarction, stroke, and/or acute kidney injury) as the primary outcome. RESULTS: Sixty-eight patients developed common severe complications (0.60%). Patients with complications were older (median age 75.6 vs 64.0 years) and had a higher American Society of Anesthesiologists (ASA) classification (45.6% vs 17.6% ASA III). The duration of hypotension at various MAP thresholds (45 to 70 mm Hg) was not associated with increasing odds of common severe medical complications. CONCLUSIONS: Controlled hypotension (ranging from 45 to 70 mmHg) for a moderate duration during neuraxial anesthesia was not associated with increased odds of common severe complications (myocardial infarction, stroke, and/or acute kidney injury) among patients receiving neuraxial anesthesia for elective THA.

Effects of controlled hypotension with restrictive transfusion on intraoperative blood loss and systemic oxygen metabolism in elderly patients who underwent lumbar fusion.

BACKGROUND: The effects of restrictive fluid therapy combined with controlled hypotension in the elderly on systemic oxygen metabolism and renal function are clinical concerns. The aim of this study was to evaluate blood loss, oxygen metabolism, and renal function in different levels of controlled hypotension induced by intravenous nitroglycerin, in combination with limited infusion, in elderly patients undergoing posterior lumbar fusion. METHODS: A total of 40 patients, aged 60-75 with ASA grade II or III, who were planned for posterior lumbar fusion were randomly allocated into two groups: experimental group [target mean arterial pressure 65 mmHg (MAP 65) or control group (MAP 75)]. Indicators for blood loss, hemodynamic, systemic oxygen metabolism, and renal function evaluation index were recorded before operation (T0), 1 h after induced hypotension (T1), 2 h after hypotension (T2), and in recovery (T3). We compared changes in these parameters between groups to evaluate the combined effects of controlled hypotension with restrictive infusion. RESULTS: CI, DO2I, and VO2I were lower in both groups at T1-T3 compared with T0 (p < 0.05). DO2I and VO2I in the MAP 65 group were lower than the MAP 75 group after operation. In both groups, SCysC increased at T1, T2, and T3 (p < 0.05) compared with T0. CONCLUSIONS: Restrictive transfusion and control MAP at 65 mmHg can slightly change in renal function and reduce the risk of insufficient oxygen supply and importantly have no significant effect on blood loss and postoperative complications. TRIAL REGISTRATION: ChiCTR-INR-16008153 . Registered on 25 March 2016.

Does an Earlier or Late Intravenous Injection of Ondansetron Affect the Dose of Phenylephrine Needed to Prevent Spinal-Anesthesia Induced Hypotension in Cesarean Sections?

BACKGROUND: There was controversy about ondansetron can reduce the incidence of spinal-induced hypotension and decrease the consumption of vasopressor in cesarean delivery with spinal anesthesia. We hypothesized that different timing of ondansetron administration may contribute to the controversy. Therefore, we aimed to determine the effect of different timing of ondansetron administration on the dose requirement of preventing phenylephrine via comparing the ED50 of prophylactic phenylephrine. METHODS: Seventy-five parturients were finally enrolled in this prospective, randomized, double-blinded dose finding study. Ondansetron or placebo was administered 5 min or 15 min before intrathecal injection. Up-down allocation method was used to determine the dose of prophylactic phenylephrine for each parturient in the three groups. The initial infusion rate of first patient was 0.5 µg/kg/min. Then, the rate for next patient was varied with increasing or decreasing of 0.05 µg/kg/min according to the response of the previous patient. An effective dose was defined as no hypotension occurred during the study period. An ineffective dose was defined as hypotension occurred during the study period. Study period in this study is from intrathecal injection to neonatal delivery. ED50 of phenylephrine infusion was calculated by probit regression. RESULTS: The ED50 of intravenous phenylephrine calculated by probit analysis was 0.33 (95% CI 0.20 to 0.38) µg/kg/min and 0.36 (95% CI 0.32 to 0.38) µg/kg/min in group A and B, and 0.41 (95% CI 0.37 to 0.44) µg/kg/min in group C for patients undergoing cesarean delivery with combined spinal-epidural anesthesia. CONCLUSION: An earlier administration of 4 mg prophylactic ondansetron contributed no benefits for lowing the dose of prophylactic phenylephrine compared to a late administration, but can decrease the dose of preventing phenylephrine in patients undergoing cesarean delivery with combined spinal-epidural anesthesia. This finding may be useful for clinical practice and further studies.

Comparison of the effect of propofol and desflurane on S-100ß and GFAP levels during controlled hypotension for functional endoscopic sinus surgery: A randomized controlled trial.

BACKGROUND: Although surgical field visualization is important in functional endoscopic sinus surgery (FESS), the complications associated with controlled hypotension for surgery should be considered. Intraoperative hypotension is associated with postoperative stroke, leading to subsequent hypoxia with potential neurologic injury. We investigated the effect of propofol and desflurane anesthesia on S-100ß and glial fibrillary acidic protein (GFAP) levels which are early biomarkers for cerebral ischemic change during controlled hypotension for FESS. METHODS: For controlled hypotension during FESS, anesthesia was maintained with propofol/remifentanil in propofol group (n = 30) and with desflurane/remifentanil in desflurane group (n = 30). For S-100ß and GFAP assay, blood samples were taken at base, 20 and 60 minutes after achieving the target range of mean arterial pressure, and at 60 minutes after surgery. RESULTS: The base levels of S-100ß were 98.04 ±â€Š78.57 and 112.61 ±â€Š66.38 pg/mL in the propofol and desflurane groups, respectively. The base levels of GFAP were 0.997 ±â€Š0.486 and 0.898 ±â€Š0.472 ng/mL in the propofol and desflurane groups, respectively. The S-100ß and GFAP levels were significantly increased in the study period compared to the base levels in both groups (P ≤ .001). There was no significant difference at each time point between the 2 groups. CONCLUSION: On comparing the effects of propofol and desflurane anesthesia for controlled hypotension on the levels of S-100ß and GFAP, we noted that there was no significant difference in S-100ß and GFAP levels between the 2 study groups. CLINICAL TRIAL REGISTRATION: Available at: http://cris.nih.go.kr, KCT0002698.

The beach chair position for shoulder surgery in intravenous general anesthesia and controlled hypotension: Impact on cerebral oxygenation, cerebral blood flow and neurobehavioral outcome.

STUDY OBJECTIVES: The aim of this study was to assess the impact of intravenous general anesthesia and controlled hypotension on cerebral saturation (rScO2), cerebral blood flow measured as middle cerebral artery blood flow velocity (Vmax MCA) and neurobehavioral outcome in patients scheduled for shoulder surgery in beach chair position. DESIGN: Prospective, assessor-blinded observational study. SETTING: University hospital, shoulder surgery operating room. PATIENTS: Forty ASA I-II patients scheduled for shoulder surgery in beach chair position and controlled hypotension. INTERVENTIONS: Neurological and neurobehavioral tests were performed prior and the day after surgery. The baseline data for near-infrared spectroscopy, bispectral index, cerebral blood flow, PaCO2 and invasive blood pressure (radial artery) were taken prior anesthesia and after anesthesia induction, after beach chair positioning and all 20 min after surgery start until discharge of the patient. MEASUREMENTS: Neurological and neurobehavioral tests, cerebral saturation (rScO2) using near-infrared spectroscopy, BIS, cerebral blood flow using Doppler of the middle cerebral artery (Vmax MCA), PaCO2 and invasive blood pressure assessed at heart and at the external acoustic meatus level. MAIN RESULTS: The incidence of cerebral desaturation events (CDEs) was 25%. The blood pressure drop 5 min after beach chair position measured at the acoustic meatus level in the CDE group was higher compared to patients without CDEs (p = 0.009) as was the rScO2 (p = 0.039) and the Vmax MCA (p = 0.002). There were no neurological deficits but patients with CDEs showed a greater negative impact on neurobehavioral tests 24 h after surgery compared to patients without CDEs (p = 0.001). CONCLUSIONS: In ASA I-II patients intravenous general anesthesia and controlled hypotension in the beach chair position affects cerebral blood flow and cerebral oxygenation with impact on the neurobehavioral outcome.

Controlled hypotension during middle ear surgery: hemodynamic effects of remifentanil vs nitroglycerin.

INTRODUCTION: Controlled hypotension is a well-known technique used by anesthesiologists to limit intraoperative bleeding in patients undergoing middle ear surgery and improve visibility of the surgical field. Nitroglycerin and remifentanil are among the drugs used to induce controlled hypotension.The aim of our study was to compare the hemodynamic effects of remifentanil and nitroglycerin in this patient population. METHODS: All consecutive patients who underwent middle ear surgery between January and December 2016, at the University Hospital Vittorio Emanuele in Catania were included in a retrospective study. Patients who were given nitroglycerin to induce controlled hypotension were compared to those given remifentanil. The following parameters were measured systolic and diastolic blood pressure, heart rate, peripheral (capillary) oxygen saturation, and fraction of expired carbon dioxide. A mean arterial pressure of 50-70 mmHg was considered optimal. RESULTS: Thirty patients who underwent stapedioplasty and tympanoplasty, 25 men and 5 women,with a mean age of 43 years (range 32-58 years) were included in the study. Fifteen patients had received nitroglycerin (group A) and 15 patients remifentanil (group B). The target blood pressure was reached in all patients and no significant difference was found between the groups with regard to the level of systolic and diastolic blood pressure, heart rate, peripheral (capillary) oxygen saturation, and fraction of expired carbon dioxide. However the heart rate of 2 younger patients in group A rose to > 100 bpm after the administration of nitroglycerin. CONCLUSION: Both remifentanil and nitroglycerin are effective in inducing controlled hypotension. In younger patients administration of nitroglycerin is associated with an increase in heart rate. KEY WORDS: Controlled hypotension, Middle ear surgery, Nitroglycerin, Remifentanil.

Lack of Association Between Levels and Length of Intraoperative Controlled Hypotension and Acute Kidney Injury in Total Hip Arthroplasty Patients Receiving Neuraxial Anesthesia.

BACKGROUND AND OBJECTIVES: Previous research suggests that increased duration and lower levels of intraoperative hypotension (IOH) are associated with postoperative acute kidney injury (AKI). However, this association has not been evaluated in the context of intraoperative controlled hypotension (IOCH), a practice that has been linked in the past to improved outcomes with respect to blood loss and transfusion needs. This study aimed to investigate whether IOCH is associated with postoperative AKI among total hip arthroplasty patients at an institution where this technique is commonly practiced. METHODS: We performed a retrospective cohort study of 2431 unilateral total hip arthroplasty patients who received IOCH under neuraxial anesthesia as well as invasive arterial monitoring between March 2016 and January 2017. Multiple logistic regression was used to compute the adjusted odds ratios of postoperative AKI, adjusting for covariates including duration of intraoperative mean arterial pressure of less than 60 mm Hg. Sensitivity analyses also considered the effects of IOH defined at mean arterial pressure of less than 55 and less than 65 mm Hg. RESULTS: Acute kidney injury occurred in 45 (1.85%) of the 2431 patients in this cohort. Longer duration of hypotension was not associated with increased odds of postoperative AKI. Preexisting differences, such as compromised renal function, best predicted increased odds of AKI. CONCLUSIONS: In this study, AKI was rare. We found a lack of association between IOH and postoperative AKI in a setting where neuraxial anesthesia-facilitated IOCH is routinely practiced. Therefore, it seems prudent for future research and clinical guidelines to consider the distinction between inadvertent and controlled hypotension.

Risk factors for intraoperative bradycardia during ear, nose, throat and maxillofacial surgery.

Intraoperative bradycardia (IOB) is one of the most common cardiac arrhythmias observed in clinical anaesthetic practice. Controlled hypotension, as a strategy of lowering patient's blood pressure during anesthesia has been practiced for decades in head and neck surgery. The aim of our study was to determine the incidence and the risk factors for intraoperative bradycardia in maxillofacial, ear, nose and throat surgery, as well as to determine whether controlled hypotension affects the occurrence of IOB. The retrospective study included 2304 patients who underwent maxillofacial, ear, nose or throat surgery. We studied the influence of: sex, age, comorbidity, type of surgery, duration of anesthesia and controlled hypotension on the occurrence of IOB. IOB was registered in 473 patients (20.5%). Patients with controlled hypotension had IOB significantly more often than patients without controlled hypotension (33.9 vs 15.1%) (p = 0.000). The significant predictors of IOB were: age (OR = 1.158; 95% CI = 1.068-1.256; p = 0.000), sex (OR = 0.786; 95% CI = 0.623-0.993; p = 0.043), ischemic heart disease (OR = 2.016; 95% CI = 1.182-3.441; p = 0.010); ear surgery (OR = 1.593; 95% CI = 1.232-2.060; p = 0.000), anesthesia duration, (OR = 1.006; 95% CI = 1.004-1.007; p = 0.000) and controlled hypotension (OR = 2.204; 95% CI = 1.761-2.758; p = 0.000). IOB is common in maxillofacial, ear, nose and throat surgery, particularly in male, older age and patients with ishemic heart disease. The ear surgery, longer anesthesia duration and controlled hypotension raise the risk for occurrence of IOB.

The safety of controlled hypotension for shoulder arthroscopy in the beach-chair position.

BACKGROUND: The safety of controlled hypotension during arthroscopic shoulder procedures with the patient in the beach-chair position is controversial. Current practice for the management of intraoperative blood pressure is derived from expert opinion among anesthesiologists, but there is a paucity of clinical data validating their practice. The purpose of this study was to evaluate the effect of controlled hypotension on cerebral perfusion with use of continuous electroencephalographic monitoring in patients undergoing shoulder arthroscopy in the beach-chair position. METHODS: Fifty-two consecutive patients who had undergone shoulder arthroscopy in the beach-chair position were enrolled prospectively in this study. All patients underwent preoperative blood pressure measurements, assignment of an American Society of Anesthesiologists (ASA) grade, and a preoperative and postoperative neurological and Mini-Mental State Examination (MMSE). The target systolic blood pressure for all patients was 90 to 100 mm Hg during surgery. Continuous intraoperative monitoring was performed with standard ASA monitors and a ten-lead portable electroencephalography monitor. Real-time electroencephalographic monitoring was performed by an attending-level neurophysiologist. RESULTS: All patients violated at least one recommended limit for blood pressure reduction. The average decrease in systolic blood pressure and mean arterial pressure from baseline was 36% and 42%, respectively. Three patients demonstrated ischemic changes on electroencephalography that resolved with an increase in blood pressure. No adverse neurological sequelae were observed in any patient on the basis of the MMSE. CONCLUSIONS: This study provides the first prospective data on global cerebral perfusion during shoulder arthroscopy in the beach-chair position with use of controlled hypotension. Our study suggests that patients may be able to safely tolerate a reduction in blood pressure greater than current recommendations. In the future, intraoperative cerebral monitoring may play a role in preventing neurological injury in patients undergoing shoulder arthroscopy in the beach-chair position.