Target Hemodynamics and Brain Injury During General Anesthesia in the Elderly
Target Hemodynamics and Brain Injury During General Anesthesia in the Elderly
BACKGROUND: Post-operative cognitive dysfunction (POCD) is a potentially irreversible loss of
 brain functions observed in elderly patients after surgical operations under general
 anaesthesia. POCD at 3 post-operative months is observed in up to 15% of patients aged 70
 years and more, and the only recognized risk factor for this condition is increasing age.
 Importantly, the incidence of POCD at 3 months has been associated to an increased disability
 and mortality.

 OBJECTIVES: The present study will evaluate in patients aged 75 years and older undergoing
 general anaesthesia for non-cardiac surgery, whether an hemodynamic strategy, aiming at
 maintaining intra-operative arterial blood pressure close to patient's preoperative blood
 pressure, i.e., to avoid hypotensive episodes, reduces the incidence of POCD at three months.

 METHODS: Around 1800 consecutive patients scheduled to undergo general anaesthesia for
 elective non-cardiac surgery will be enrolled. Each patient's cognitive function will be
 evaluated preoperatively and at 3 months and 1 year postoperatively, together with the
 occurrence of hearing loss and vestibular function impairment. Furthermore, the incidence of
 postoperative delirium and cardiovascular, respiratory and infectious complications will be
 evaluated.

 EXPECTED RESULTS: The primary outcome is a 25% relative reduction in the incidence of POCD at
 3 postoperative months. Secondary outcomes are the reduction of POCD incidence at 1
 postoperative year, a reduction in postoperative hearing loss and vestibular impairment at 3
 months, a reduction in the incidence of delirium. Hospital length of stay and 90 day
 mortality will also be assessed. This present study could have a high socio-economic impact,
 reduce healthcare costs and patient morbidity and mortality with a simple not expensive
 intraoperative intervention.
BACKGROUND Post-operative cognitive dysfunction (POCD) is defined as a spectrum of
 postoperative central nervous system dysfunctions both acute and persistent, including subtle
 neurologic signs and neuropsychological impairment. The incidence of POCD is clearly
 associated with the age of patients, with older patients being more susceptible to neurologic
 impairment following anesthesia and surgery. Due to the increasing life expectances and
 ameliorated surgical and anesthesiologic techniques, more and more elderly people are
 undergoing surgical procedures. In this respect, POCD is a complication that needs to be
 taken into account in the perioperative course of elderly patients, especially in those with
 reduced neurological functional reserve capacity and high prevalence of comorbidities. It is
 worth underlining that the occurrence of POCD brings a very important subjective burden on
 the quality of life of the patient and also and outstanding social impact.

 Several observational studies have shown that POCD occurs in 25% of patients 1 week after the
 surgical procedure (early POCD) and in approximately 15% of patients at 3 months (late POCD).
 Importantly, the incidence of POCD at 3 months has been associated to an increased disability
 and mortality.

 Post-operative cognitive dysfunction is probably a multifactorial syndrome, nevertheless 3
 principal pathophysiological hypothesis, that certainly could co-exist, have been formulated:

 1. Pharmacological hypothesis: drugs employed during anesthesia can produce alterations in
 the neuronal network, principally through alterations of the cholinergic transduction
 signal;

 2. Toxic hypothesis: the neuronal damage is a direct consequence of the drugs employed
 during anesthesia and of the inflammatory mediators associated to the surgical
 procedure;

 3. Hemodynamic hypothesis: hemodynamic changes induced by general anesthesia cause
 alterations in cerebral blood flow, potentially resulting in ischemic neuronal damage.

 The present study focuses on the third hypothesis and aims to evaluate the influence of a
 target of intraoperative arterial blood pressure based on preoperative values on the
 development of POCD at 3 months after elective non-cardiac surgery under general anesthesia
 in patients aged 75 years and older.

 The present study has a potential high scientific and socio-economic impact as it could
 identify a single and quite easily accomplished intraoperative intervention, i.e. a different
 management of intraoperative blood pressure, that could potentially reduce the incidence of
 neurological deterioration in elderly patients undergoing general anesthesia for non-cardiac
 surgery.

 Furthermore, it will be the first study investigating a population of patients aged 75 years
 and more and, to the best of the investigators' knowledge, the first study that will evaluate
 systematically the possible changes in hearing and vestibular function induced by general
 anesthesia and surgery.

 DETAILED RESEARCH PROTOCOL

 The present study is structured in 3 distinct phases:

 1. Preoperative Phase;

 2. Intraoperative Phase;

 3. Postoperative Phase;

 1) PREOPERATIVE PHASE After obtaining informed consent to the study, several evaluations are
 performed in the Clinic for preoperative anesthesiology evaluation. These include the
 standard anesthesia evaluation, a geriatric and neuropsychological evaluation and an
 audiology evaluation. All preoperative evaluations are performed on the same day and in the
 same place during the normal path followed by outpatients scheduled for elective surgery.
 Geriatric, neuropsychological and audiology evaluation are always performed in the same
 sequence.

 Multidimensional Geriatric Assessment:

 The multidimensional geriatric assessment includes several tests that allow a global
 evaluation of the functional status of the patient, including the cognitive domain and the
 functional performance (ability).

 The Mini Mental State Examination (MMSE) and the Clock Drawing Test will be used to assess
 the cognitive state of the patients. The MMSE is usually employed in clinical practice for
 two reasons: (i) as a quick tool to screen the cognitive status of the patient and (ii) as a
 tool to track the changes over time in cognitive state of the patients. The MMSE consists of
 30 items (questions/tests), that explore different cognitive domains: spatial and temporal
 orientation, memorization of words, attention, calculation, recall, language and constructive
 praxis. The score of the MMSE ranges therefore from 0 to 30. A corrected score of ≤ 23 is
 usually considered suggestive of cognitive decline. The score of the MMSE is corrected for
 age and education of the patient.

 The Clock Drawing test (CDT) is an additional test employed to evaluate the global cognitive
 state of patients and is considered complementary to the MMSE. To perform the CDT the patient
 is asked to draw a circle in order to symbolize a clock face. Furthermore the patient is
 asked to draw the watch hands in order to indicate ten past eleven. The test explores the
 visual-spatial, practical and executive functions of the patient. The maximal obtainable
 score is 5/5 and requires the presence of all numbers, drawn in the correct order and close
 to the border of the clock face, with the correct symmetry and the watch hands correctly
 showing ten past eleven. The presence of extra numbers, segmentation lines or rotation of the
 numbers determines the subtraction of 1 point to the score. Scores > 3/5 are considered
 normal.

 Functional performance is evaluated employing the scores of the "Activities of Daily Living"
 (ADL) and the "Instrumental Activities of Daily Living" (IADL), respectively.

 The ADL are the activities that a person is able to perform independently on a daily basis
 (eat, dress, wash themselves, move from bed to the chair, use the toilet, etc.). The IADL are
 the activities that allow a person to live independently in a house or apartment (cook, clean
 up the house, take medications, use the phone, etc. ).

 Finally the patients will be characterized in terms of frailty. The geriatric concept of
 frailty generically indicates a condition of increased vulnerability to stressful conditions,
 associated to an increased risk of adverse events including falls to the ground, disability,
 hospitalization and mortality. Physical frailty is defined by the presence of 3 or more of
 the following criteria:

 1. Unintentional weight loss (≥ than 5% body weight loss in the last year);

 2. General feeling of exhaustion (subjective, based on questions on the effort in
 performing certain activities);

 3. Weakness as expressed by a reduced handgrip strength, applying different reference
 values for women and men;

 4. Slow walking speed;

 5. Low levels of physical activity; The presence of 1 or 2 of these criteria characterizes
 the so called "pre-frailty", a condition that is more sensitive to eventual
 interventions as compared to frailty (3 or more criteria).

 Finally, patients will be evaluated for "cognitive frailty", which combines physical frailty
 with the score of the Clinical Dementia Rating (CDR) (see below), in order to identify
 non-dement patients in whom physical frailty is however associated to an initial cognitive
 impairment.

 Patients are classified in 4 different categories:

 1. Healthy elderly subjects (no evidence of physical frailty and CDR = 0);

 2. Elderly subjects with physical frailty and normal cognitive function (presence of
 physical frailty and CDR =0);

 3. Elderly subjects without physical frailty but with initial cognitive impairment (no
 physical frailty and CDR = 0.5);

 4. Elderly subjects with physical frailty and initial cognitive impairment (presence of
 physical frailty and CDR = 0.5); The condition of the subjects belonging to group 4 is
 defined as "cognitive frailty".

 The Clinical Dementia Rating (CDR) is a complex scale performed to quantify the severity of
 the symptoms of dementia. It includes queries about the cognitive and functional domains. The
 final score ranges between 0 and 3, with higher scores indicating more severe dementia
 symptoms. A score of 0.5 is suggestive of the presence of mild symptoms. It is therefore
 possible that patients with corrected MMSE ≥ 24 have a CDR score of 0.5. Of note, patients
 included in the study will not undergo the CDR test, as the different items that compose the
 CDR can be derived from the performed geriatric and neuropsychological test batteries (see
 below).

 Neuropsychological Evaluation The cognitive functionality at baseline and its possible
 worsening after anesthesia/surgery, i.e. the development of POCD, is best evaluated through
 the administration of neuropsychological test batteries. During the baseline evaluation a
 neuropsychologist will administer to the patient (or to the subject in the Control group) a
 battery of tests standardized to evaluate specifically different cognitive domains: memory,
 attention, language, executive functions, speed of information processing. The obtained raw
 scores will be corrected for age, gender and education and transformed, according to Italian
 calibration standards, in standardized scores (Equivalent Scores = ES) on an ordinal scale
 that ranges from 0 to 4, where 0 represents scores below the cut-off, i.e., pathological
 scores, 1 that represents borderline scores and 2,3 and 4 which characterize normality.

 The duration of the administration of the test battery is approximately 35 minutes. At 3
 months and 1 year from the surgical procedure/general anesthesia (or from baseline evaluation
 in the Control group) the same test battery will be repeated. In those tests having a
 parallel version, the parallel version will be administered, in order to reduce the learning
 effect. The difference in scores of the tests performed at 3 months (and 1 year) and
 baseline, corrected for the mean difference observed in the Control group in the same
 timeframe, will be used in order to define the occurrence of POCD.

 Patients in whom the difference (worsening) in the global score at 3 months to the global
 score at baseline will be greater than 2 standard deviations from the expected difference,
 i.e., the mean difference between the two evaluations (baseline and 3 months) observed in the
 Control Group, will be diagnosed with POCD. Moreover, changes in raw scores of the different
 tests will be considered with the purpose of identifying possible changes in specific
 cognitive domains.

 The administered neuropsychological tests will be the following:

 -  Trail Making Test: evaluates the visual-motor coordination and speed and task-switching
 skills by assessing someone's ability to follow a simple number sequence (Trails A) and
 a more complex sequence of alternating numbers and letters (Trails B).

 -  Stroop test: evaluates selective attention, executive functions, the inhibition of
 distractions and cognitive flexibility.

 -  Symbol Digit Modalities Test: evaluates sustained attention, with elements of vigilance
 and working memory.

 -  Free and Cued Selective Reminding Test: measures anterograde visual and verbal memory
 skills.

 -  Verbal Phonemic Fluency Test: measures the capacity of access to verbal vocabulary and
 is considered a marker of pre-frontal functionality.

 -  Denomination test: evaluates the capacity of visual access of vocabulary.

 These tests have a score and a cut-off value that allows to categorize the result as normal,
 i.e., that falls within the average results obtained from a control group of healthy subjects
 matched for age, gender and education, or pathological, i.e., below this average value.

 Audiology Evaluation The audiology evaluation will include the following tests: video
 oculography, pure tone audiometry, disyllabic speech audiometry and speech audiometry with
 verbal tasks and motor responses.

 Video oculography analyzes the function of the oculomotor system through the study of
 saccadic eye movements and optokinetic system. It allows to identify an alteration at the
 level of the brainstem, cerebellum or of both structures.

 Saccadic eye movements are rapid, ballistic eye movements, which subserve vision by
 redirecting the visual axis to a new location, i.e., to direct the fovea onto an object or
 region of interest that appeared in the periphery of the field of view. Saccadic eye
 movements represent the majority of eye movements and the control signal of saccadic eye
 movements is the so-called "retinal error".

 Collected parameters during the study of saccadic eye movements include:

 Latency: this is the time taken from the appearance of a target to the beginning of a saccade
 in response to that target; Peak Velocity: this is the highest velocity reached during the
 saccade. Saccade velocity profiles are usually symmetrical at least for small and medium size
 saccades. In some conditions while the size of saccades remains reasonably accurate, the
 saccade velocity is greatly reduced - so-called slowed saccades; Precision: relation between
 angular displacement of the eye and the displacement of the reference target; The
 "optokinetic reflex" causes eye movement in response to objects moving in the periphery while
 the head is stationary and is extremely important for stabilizing the image of visual input
 on the retina and provides for primary control of this capacity when the head is stationary.
 It is composed by a slow phase (SP), directed toward the movement of the panorama, and a
 quick phases (QP) with opposite direction. These movements have similar characteristics to
 saccadic eye movements.

 Collected parameters during the study of optokinetic nystagmus include the slow-phase
 velocity of optokinetic nystagmus, which is dependent upon the speed of the stimulus, gain,
 expressing the percentage of the ratio between the speed of the slow phase of nystagmus and
 the speed of the stimulus, asymmetry, indicating the difference in gain between the two
 sides.

 Pure tone audiometry aims at defining quantitatively and qualitatively the possible
 occurrence of hearing loss, its entity and site of the lesion. Pure tone audiometry is
 performed through the aid of an audiometer and headphones. This study is performed to
 investigate the functionality of the peripheral auditory system.

 Finally, disyllabic speech audiometry and speech audiometry with verbal tasks and motor
 responses will be performed, using controlateral masking (cocktail party noise). These
 evaluations investigate the comprehension of verbal stimuli and numerically quantify the
 ability to repeat disyllabic words. It also evaluates the semantic comprehension of phrases
 and the ability of the subject to follow simple motor commands.

 These tests, taken together, evaluate both the functionality of the peripheral hearing
 apparatus and the cortical integration of peripheral signals. Considered parameters are the
 comprehension of the verbal message (100% represents full understanding) and the sound
 intensity level at which comprehension is maximal, expressed in decibels hearing level (dB
 HL). Another parameter studied during speech audiometry testing is the percent reduction of
 disyllabic words understood as the sound intensity increases. This phenomenon, the reduction
 of understood disyllabic words with increasing sound intensity, is due to pathologic
 distortion of cochlear and retro cochlear structures (VIII cranial nerve).

 Anesthesiology Evaluation The anesthesiology evaluation will be performed as standard
 clinical practice in preparation for surgical procedures under general anesthesia. This
 evaluation will include: physiologic, pathologic and drug history collection, clinical
 examination including peripheral saturation of oxygen by pulse-oximetry (SpO2), resting heart
 rate and non-invasive blood pressure measurement with an automatic sphygmomanometer. Three
 measurements of resting blood pressure will be performed during the visit and the mean value
 of the three measurements of mean blood pressure will represent the baseline mean arterial
 blood pressure of the patient

 2) INTRAOPERATIVE PHASE. The day of the operation the patient will be randomized to one of
 two groups, Treatment or Standard of Care (see below). Vital functions will be recorded once
 the patient is in the operating room, before induction of anesthesia, and throughout the
 entire duration of the surgical procedure and anesthesia up to extubation or transport to the
 post-operative intensive care unit. Parameters recorded will include blood pressure (either
 invasive or non-invasive, depending on clinical need), heart rate, peripheral saturation of
 oxygen, end-tidal concentration of carbon dioxide, ventilator parameters, drugs and fluid
 administered, fluid balance and blood loss. Additional measurements will be performed when
 available: non-invasive cardiac output (Nexfin/Pulsioflex, Edwards Lifesciences),
 non-invasive cerebral oximetry through near-infrared spectroscopy (INVOS, Covidien) and depth
 of anesthesia through bispectral index (BIS) measurement (Bispectral Index Technology,
 Covidien).

 The anesthesiologist will be responsible for the clinical management of the patients assigned
 to the two arms. Violations of the protocol are possible whenever the anesthesiologist judges
 it clinically necessary.

 -  Standard of Care Group: intraoperative hemodynamic management will be left to the
 discretion of the anesthesiologist, without any indication as to the intraoperative
 hemodynamic strategy to be adopted. Of note, baseline mean arterial pressure (as
 measured during the preoperative evaluation) will not be communicated to the
 anesthesiologist in care.

 -  Treatment Group: in this group the anesthesiologist will have as hemodynamic target the
 maintenance of mean arterial blood pressure within 10% of the baseline mean arterial
 blood pressure value. The modalities to reach this target (quantity and type of drugs,
 quantity and type of intravenous fluids, positioning of the patient etc.) will be left
 to the clinical judgment of the anaesthesiologist. All interventions will be recorded.

 The intraoperative protocol requires the acquisition of hemodynamic, respiratory, and all the
 other parameters already described at pre-defined intervals (anesthesia induction, start of
 surgery, every 30 minutes thereafter, end of surgery, extubation/transport to post-surgical
 ICU).

 At the end of the operation the blood pressure recording of the entire duration of general
 anesthesia will be downloaded from the anesthesia monitor and analyzed offline with a
 dedicated software to quantify exactly the time spent in each category (mild, moderate or
 severe, see below) of hypotension or hypertension.

 Any hypotensive or hypertensive episode will be classified as mild, moderate or severe based
 on the worst mean arterial blood pressure recorded during the episode, according to the
 following cut-offs.

 Mild: mean arterial blood pressure 10-20% of baseline mean arterial pressure; Moderate: mean
 arterial blood pressure 20-40% of baseline mean arterial pressure; Severe: mean arterial
 blood pressure < or > 40% of baseline mean arterial pressure.

 3) POSTOPERATIVE PHASE.

 DELIRIUM During the first postoperative week all patients will be evaluated, on a daily
 basis, for delirium occurrence by the CAM-ICU scale (Confusion Assessment Method for the
 Intensive Care Unit).

 POSTOPERATIVE COMPLICATIONS Length of stay in the ICU (if applicable), length of stay in the
 hospital and any postoperative complication will be recorded. Cardiac, respiratory, renal,
 neurologic and hemorrhagic complications will be assessed.

 Cardiac complications

 Acute myocardial infarction (AMI): detection of a rise and/or fall of cardiac biomarker
 values (preferably cardiac troponin, cTn) with at least one value above the 99th percentile
 upper reference limit and with at least one of the following:

 -  symptoms of ischemia;

 -  new or presumed new significant ST-segment-T wave (ST-T) changes or new left bundle
 branch block (LBBB);

 -  development of pathological Q waves in the ECG;

 -  imaging evidence of new loss of viable myocardium or new regional wall motion
 abnormality;

 -  identification of an intracoronary thrombus by angiography or autopsy. Congestive heart
 failure: at least one of the following clinical signs (i.e. elevated jugular venous
 pressure, respiratory rales/crackles, crepitations, or presence of S3) and at least one
 of the following radiographic findings (i.e. vascular redistribution, interstitial
 pulmonary edema, or frank alveolar pulmonary edema).

 Pulmonary embolism: any one of the following:

 1. A high probability ventilation/perfusion lung scan

 2. An intraluminal filling defect of segmental or larger artery on a helical CT scan

 3. An intraluminal filling defect on pulmonary angiography

 4. A positive diagnostic test for deep vein thrombosis (e.g., positive compression
 ultrasound), acute cor pulmonale at cardiac ultrasound and one of the following:

 A. non-diagnostic (i.e., low or intermediate probability) ventilation/perfusion lung scan B.
 non-diagnostic (i.e., subsegmental defects or technically inadequate study) helical CT scan
 Cardiac arrest: documented or presumed ventricular fibrillation, sustained ventricular
 tachycardia, asystole, or pulseless electrical activity requiring cardiopulmonary
 resuscitation, pharmacological therapy, or cardiac defibrillation.

 Atrial fibrillation: new atrial fibrillation that results in angina, congestive heart
 failure, symptomatic hypotension, or that requires treatment with a rate controlling drug,
 antiarrhythmic drug, or electrical cardioversion.

 Neurologic complications Stroke (ischemic or hemorrhagic): new focal neurological deficit
 thought to be vascular in origin with signs or symptoms lasting more than 24 hours or leading
 to death.

 Renal complications Acute kidney injury is defined by an increase in serum creatinine of more
 than or equal to 1.5 times the baseline (preoperative) value or more than or equal to 0.3
 mg/dl.

 Hemorrhagic complications Mild hemorrhage: decrease of Hb levels < 3 g/dl without hemodynamic
 impact, without need for surgical revision or endovascular intervention; conservative
 treatment (transfusion of 2-3 red blood cells units and fluid infusion); Severe hemorrhage:
 decrease of Hb levels > 3 g/dl with hemodynamic impact (tachycardia, hypotension, oliguria
 etc); transfusion of more than 3 red blood cells units; need for surgical revision or
 endovascular treatment.

 POSTOPERATIVE COGNITIVE EVALUATION Patients At 3 months ± 2 weeks and 1 year ± 2 weeks after
 the surgical intervention, patients will undergo the same geriatric, neuropsychological and
 audiology evaluations described in the "Preoperative Phase" section.

 Subjects of the Control Group Subjects enrolled in the Control group will undergo the same
 evaluations (geriatric, neuropsychological and audiology) described in the "Preoperative
 Phase" section and to the same evaluations after 3 months ± 2 weeks and 1 year ± 2 weeks.
 These subjects will not undergo any surgical procedure and will therefore not be evaluated
 for post-operative complications or delirium occurrence.

 STATISTICS

 Sample size calculation.

 Primary outcome measure:

 The incidence of POCD is around 15% in patients aged over 70 years. Despite the lack of data
 in patients aged 75 years and more (the average expected age is around 80 years in this
 population), the investigators estimate an incidence of 20%. Hypothesizing that the proposed
 intervention (intraoperative arterial blood pressure target) could cause a 25% relative
 reduction in the incidence of POCD (from 20% to 15%) the sample size, for a probability of
 type I error α=0.05 and a power (1-β) = 0.8 is of 1812 patients. Of note, at the enrolment of
 906 patients the Data Safety and Monitoring Board (DSMB) will perform an ad interim analysis.

 Secondary outcome measures:

 -  Delirium: the incidence of delirium in very old patients undergoing general anesthesia
 is around 15%. The sample size foreseen for the primary outcome measure (1812 patients)
 provides a power (1-β) = 0.88 with α = 0.05 to detect a 30% relative reduction in this
 secondary outcome measure.

 -  Incidence of POCD at 1 year: the incidence of POCD in patients over 70 years of age, at
 1 year after surgery is estimated to be 16%. In the very old, given the lack of data in
 literature, the investigators estimate that the incidence could be around 20%, therefore
 similar to the incidence of POCD at 3 months after surgery. The sample size foreseen for
 the primary outcome measure (1812 patients) provides a power (1-β) = 0.8 with α = 0.05
 to detect a 25% relative reduction in this secondary outcome measure.

 -  Hearing and vestibular dysfunction: There are not sufficient data in the literature to
 estimate the incidence of this secondary outcome measure. It is therefore not possible
 to estimate the statistical power.

 Design and Pilot Study This is a multicentre international prospective parallel-group
 double-blind (patients and outcome assessors) randomized controlled trial. Currently two
 Centres are involved (Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
 and Universitätsmedizin Göttingen (UMG), Göttingen, Germany). Other Hospitals will be
 involved after the enrolment of the first 100 patients (Pilot study).

 The first 100 enrolled patients will be included in a formal pilot study in order to evaluate
 the feasibility of the study and estimate the real incidence of POCD at 3 months in this
 study population. These patients will be randomized, and the minimization criterion will be
 applied, similarly to the other patients (see below). Of note, these patients will be
 included in the final analysis.

 Randomization Patients will be randomized on the day of the surgical procedure through the
 use of a dedicated software.

 Considering the known risk factors for POCD (advanced age, major surgery and low level of
 education), the minimization criterion will be applied to the randomization. Minimization
 allows to randomize each new patient enrolled in the study in order to minimize the
 differences between the two allocation arms for the risk factors considered. This means that
 when a new patient enters the study, the patient's own characteristics for the risk factors
 considered will affect the patient's probability to be enrolled in one of the two allocation
 arms. The minimization criterion allows to reduce unbalancing for known risk factors between
 the allocation arms of the study.

 The criteria for minimization will be the following:

 -  Age class: 75 ≤ age < 80; 80 ≤ age < 85; age ≥ 85

 -  Foreseen duration of the surgical intervention: < 2 hours; ≥ 2 hours

 -  Education level (years of scholarity): 0-8 years; 9-13 years; >13 years

 Control Group Two hundred and fifty subjects will be enrolled in the Control Group; 30
 subjects will be included in the pilot study. Considering the rule of thumb that requires a
 minimum sample size of 120 for the study of reference intervals, the proposed sample size of
 250 seems definitely adequate. Nevertheless, the pilot study will allow to have a clearer
 view of the application of the parametric method. The sample size of the control group could
 therefore be resized based on preliminary data from the Pilot Study.

 Statistical analysis The analysis of continuous variables will be performed via Student's
 t-test, one or two way analysis of variance (depending on the characteristics of the
 analysis). The study of association between continuous variables will be performed through
 linear regression methods keeping in consideration possible non-linear effects. The analysis
 of non-categorical variables will be performed with contingency tables through the use of
 Fisher's exact test and Chi-square test, together with appropriate indicators of association.
 P<0.05 will be considered as significant. A detailed statistical analysis plan will specify
 the phases of the analysis in relation to the objectives of the research protocol.
 Publications deriving from this research protocol will present data according to the current
 recommendations on parallel-group randomized controlled trials involving non-pharmacological
 treatments.

 The primary and secondary outcomes will be evaluated according an Intention to Treat (ITT)
 analysis, furthermore results will be evaluated according to the effective adherence to the
 study protocol ("Per Protocol" Analysis).

 Finally, the following pre-specified and subgroups analysis will be performed:

 -  Total hypotensive time vs. primary and secondary outcome measures;

 -  Mild, moderate and severe hypotensive time vs. primary and secondary outcome measures;

 -  Analysis of primary and secondary outcome measures related to minimization categories
 (age classes, education level, major vs. minor surgery);

 -  Analysis of primary and secondary outcome measures according to the occurrence of
 intraoperative cerebral desaturation episodes according to values recorded with the
 INVOS.

 -  Analysis of primary and secondary outcome measures in the subgroup of patients with
 hypertension and in patients with diagnosis of "cognitive frailty".

 The study is coordinated by a Steering Committee which includes the scientific
 representatives of the Institutions assuming all the competences and organizational know-how
 required for the trial:

 Istituto di Anestesia e Rianimazione, Fondazione IRCCS - "Ospedale Maggiore Policlinico,
 Mangiagalli, Regina Elena", Università degli Studi di Milano [Coordinating Center]: L.
 Gattinoni, T. Langer, A. Santini, A. Pesenti.

 UOC Geriatria, Dipartimento di Medicina Interna e Specializzazioni Mediche,Area di Medicina
 Interna e Geriatria: D. Mari.

 UOC Audiologia, Dipartimento di Medicina Interna e Specializzazioni Mediche, Area di Medicina
 Specialistica: A. Cesarani Universitaetsmedizin Goettingen, Zentrum Anaesthesiologie-,
 Rettungs- und Intensivmedizin: M.Quintel.
Inclusion Criteria:

 -  any patient aged 75 years and more scheduled for elective non-cardiac surgery under
 general anesthesia.

 Exclusion criteria:

 -  Failure to obtain informed consent to the study;

 -  Impossibility to perform scheduled geriatric and neuropsychological tests during the
 preoperative evaluation;

 -  Mini-mental state examination score (corrected for age and education) ≤ 23 at the
 preoperative evaluation;

 -  Patients scheduled to undergo intracranic neurosurgical procedures or vascular
 surgery;

 -  Patients who have been subjected to a surgical procedure under general anesthesia in
 the preceding 6 months;

 -  Patients with metastatic cancer; patients falling in the category of the American
 Society of Anaesthesiologists (ASA) physical status 4;

 -  Patients already included in the study, i.e. second surgical procedure;

 Inclusion criteria for the Control Group:

 • Subjects of 75 years and more in whom no hospitalization or surgical procedure is
 scheduled in the following 3 months.

 Exclusion criteria for the Control Group:

 -  Failure to obtain informed consent to the study;

 -  Impossibility to perform scheduled geriatric and neuropsychological tests during the
 baseline evaluation;

 -  Mini-mental state examination score (corrected for age and scholarity) ≤ 23 at the
 baseline evaluation;

 -  Subjects who have undergone a surgical procedure under general anesthesia in the
 preceding 6 months;

 -  Subjects who have undergone an unexpected surgical procedure under general anesthesia
 in the timeframe between baseline 3 months evaluation.