Presentación del tema: "BIS Índice Biespectral Un nuevo ¨signo vital¨"— Transcripción de la presentación:
1BIS Índice Biespectral Un nuevo ¨signo vital¨ During the evolution of modern anesthesia practice, patient assessment hasundergone gradual change and refinement. Observations of clinical signs such aspupil response, patterns of respiration, quality of the pulse and movement werefirst augmented by direct measurement of physiologic endpoints including bloodpressure, heart rate and respiratory rate and volume. With the development ofpulse oximetry and capnography, a precise assessment of ventilatory managementcould be made. The use of end-tidal agent analysis and peripheral nervestimulation provided anesthesia clinicians the ability to measure pharmacologicagent concentration and effect, respectively. Today, cardiac function can beevaluated using advanced technologies that range from pulmonary arterycatheters and transesophageal echocardiography to new methods of continuousblood pressure and cardiac output monitoring.Despite the remarkable improvements in assessment of the cardiovascular systemduring anesthesia, direct determination of the effect of the anesthetic and sedativeagent(s) on the central nervous system has remained a challenge. Careful clinicalinvestigation demonstrated that hemodynamic responses do not necessarily providean accurate representation of the central nervous system responsiveness toanesthetic agents and therefore were unreliable indicators of brain status.1 Incontrast, a technology that would permit independent neurophysiologicalmonitoring of the central nervous system would provide a direct measure of brainstatus during anesthesia and sedation, allowing clinicians to fine-tune perioperativemanagement and achieve the best possible outcome for each patient. Accuratemonitoring and targeting of brain effect, in combination with assessment of clinicalsigns and traditional monitoring, would permit a more complete approach toadjusting the dosing and mixture of anesthetic, sedative and analgesic agents.Diomer Avendaño Q.Residente 1er añoAnestesiología y Reanimación
2Contenido Cómo funciona? BIS y consideraciones especiales BIS y despertar intraoperatorio (DIO)BIS y mortalidadBIS y costosConclusiones
3Porqué aparece el BIS? ¿Está mi paciente adecuadamente anestesiado? AnalgesiaInmovilidadRelajación¿Está mi paciente adecuadamente anestesiado?Therapeutic targeting is a clear benefit that results from BIS monitoring. Usingthis new parameter, the clinician can manage patients within the optimal planeof anesthesia effect, reducing the unwanted occurrence of excessive or inadequateanesthetic effect.13Clinical investigations of BIS monitoring during anesthesiahave consistently demonstrated an average 25% reduction in intraoperativeanesthetic use and a consistent reduction in the time for emergence from generalanesthesia.The practice of anaesthesia is based on the concept of componentsof anaesthesia resulting from separate pharmacological actions ofmultiple agent administration (Kissin 1997). Many anaesthesiol-ogists rely on somatic signs (motor responses, changes in respi-ratory pattern) and autonomic signs (tachycardia, hypertension,lacrimation, sweating) to guide the dosage of anaesthetic agents inorder to achieve the basic goals of anaesthetic management, that isunconsciousness (hypnotic effects), blockade of somatic motor re-sponses, and suppression of autonomic responses to noxious stim-ulation. However, these clinical signs are not reliable measures ofthe conscious state of anaesthetized patients (Mahla 1997). Theuse of these clinical signs in judging dosage of anaesthetic agentscan lead to either overdosage or underdosage, which can result inadverse effects due to too deep or too light anaesthesia.AmnesiaInconciencia
4EEG en anestesia Cambios en anestesia general Aumento de la amplitud Disminución en frecuenciaBeta( Hz)Alfa( Hz)Theta( Hz)Delta( Hz)
5The BIS has been de-scribed in the literature as a composite index consistingof a weighted combination of four components; how-ever, the details of the BIS algorithm have not beendescribed in their entirety by the manufacturer of theBIS monitors. It has been reported that the four compo-nent subparameters are derived from time-domain,bispectral, and power spectral analyses of the EEG .The time domain subparameter includes Quazi suppres-sion detection and the suppression ratio (SR) , andthese two subparameters represent the deepest anesthe-sia conditions. The bispectral domain subparameter iscalled SyncFastSlow . It represents the low-frequency feature and is associated with moderateanesthetic effect. The frequency domain subparameteris called the relative beta ratio . It represents thehigh-frequency feature and is associated with light anes-thetic effect and beta activation. Therefore, the BIS is acombination of the four subparameters describedabove, and the individual subparameters make the BISa precise, near-linear function across the continuum ofclinical states from awake to isoelectric EEG. However,of the four subparameters, only the SR is available forrecording via the processed EEG port.
6Digital Signal Converter (DSC) The digital signal converter (Figure 3) receives, amplifies anddigitizes the raw EEG signal forsubsequent processing and analysis.In addition, key filters and signalprocessing steps occur in the DSC tidentify and reject certain types ofelectrical artifact (e.g., electrocauteryfilters in DSC-XP systems).The digitized EEG data travelsthrough the DSC cable to the BISengine.The BIS engine, the heart of the BIS system, contains the microprocessorresponsible for rapid signal processing and computation of the BIS Index.Some of the steps involved in the analysis of the EEG include multiple methodsof artifact detection and processing. Segments of the EEG that are compromisedby the presence of artifact are not included in the calculation of the BIS Index.Monitoring Level of Consciousness during Anesthesia and Sedation. Aspect Medical Systems, 2003
7The BIS is a combination of three weighted parameters: (i) the burst suppression ratio (the proportion ofisoelectric EEG signal in an epoch); (ii) the beta ratio (ameasure of the proportion of signal power in the high vsmedium frequency range); and (iii) the SynchFastSlow(which quanti®es the relative bispectral power in the 40±47 Hz frequency band).As anaesthesia deepens, the amplitude of the highfrequency portion of the EEG decreases, and theamplitude of the low frequencies increases.3Thesechanges can be described and quanti®ed statistically.First-order statistics like the mean can be applied to theraw EEG. More useful information is obtained byapplying second-order statistics like the power spectrumand the autocorrelation. However, it is conceivable thatthe different frequencies within the signal may not beindependent of each other. If the oscillations are linkedby a common phase relationship, it is necessary to usethird-order statistics to extract this information. Thebispectral power is said to indicate the presence ofquadratic phase-coupling between different frequencieswithin the signal.4The question arises, how important isthis higher-order information?Los sistemas BIS muestran el valor del Índice BIS como un valorúnico, calculado a partir de datos recopilados en los últimos 15 a 30segundos de registro de EEG y actualizados cada segundo. Laobtención del valor del Índice BIS a partir de varios segundos dedatos de EEG “atenúa” efectivamente los datos para evitarfluctuaciones excesivas de los valores BIS. También permitedeterminar un valor incluso si la señal del EEG se interrumpebrevemente. La mayoría de los sistemas BIS permiten al usuariocambiar la tasa de atenuación para adecuarla al entorno clínico.
9BIS y metabolismo cerebral This research concerning the BIS Index – as a unique processed EEG parameter– also suggests that reductions in cerebral metabolism caused by other factors willresult in decreases in BIS.9For example, in the operating room, physiologicchanges known to impact cerebral metabolic activity – e.g., cardiac arrest,hypothermia – have been characterized by changes in BIS.10.11A clear limitationof the BIS system, however, relates to its derivation from unilateral, frontal-lobeEEG signals. Clinicians must decide whether the capability and limitations ofBIS monitoring may be appropriately utilized as a more encompassing andrevealing measure of brain function.12The established link between cerebral metabolic activity and BIS values canprovide revealing insights into brain function. In a recent study comparingbaseline (awake) BIS values in patients with Alzheimer’s disease and multi-infarctdementia to an age-matched control group, a significant proportion of theneurologically-impaired group showed BIS values less than 93 at baseline.13These abnormally low values might be expected in patients with a disease processthat impairs cerebral function and memory. This observation suggests:• Intraoperative BIS values (as a measure of anesthetic effect)must be interpreted more cautiously in these patientsLos valores del Índice BIS pueden reflejar la tasa metabólica cerebralreducida que producen la mayoría de los agentes hipnóticos. Seobservó una correlación significativa entre los valores del Índice BISy la reducción de la actividad metabólica cerebral completa por elaumento del efecto anestésico mediante tomografía de emisión depositrones (figura 4).Sin embargo, es importante destacar quetambién se pueden producir cambios en el Índice BIS por factoresdistintos de la administración de fármacos que pueden influir en elmetabolismo cerebral (por ejemplo, alteraciones de temperatura uhomeostasis fisiológica).Por último, cabe observar que el valor BIS proporciona unamedición del estado del cerebro derivado del EEG, no laconcentración de un fármaco determinado. Por ejemplo, los valoresBIS disminuyen durante el sueño natural así como durante laadministración de un agente anestésico.
10Interpretación clínica Cuando los valores BIS disminuyen por debajo de 70, la función dememoria se reduce significativamente y la probabilidad de recuerdoexplícito desciende de forma considerable. Durante la sedación, sepueden observar valores BIS >70 en niveles de sedaciónaparentemente adecuados. Sin embargo, en dichos niveles, puedehaber una probabilidad mayor de consciencia y posibilidad derecuerdo.3Anesthesiology. 1997;86:836-47
11Pantalla BISEMGAs we see, Since the BIS is an EEG derived parameter. Would Patients with abnormal EEG patterns influence BIS monitoring??? Indeed !!! As the BIS monitor is always sensitive enough to pick up all these abnormal EEG patterns, this should be kept in mind during BIS interpretation
12Por qué usar el BIS?Brinda información de efecto de los anestésicos sobre el cerebro.Sobre o infra dosificación de anestésicos.Monitoria tradicional no es medida confiable del estado de conciencia.Variabilidad entre pacientes.Anesthetic agent concentrationmeasurement systems(e.g., end-tidal agentconcentration) do not measureanesthetic effect on the targetorgan, the brain. Thus, thesesystems cannot identify alterationsin expected levels of hypnosis dueto pharmacodynamic variabilityamong patients. Rather, theexistence of this variability meansthat identical drug concentrationscommonly produce considerablydifferent hypnotic responsesamong individuals or within thesame person at different times.BIS monitoring continuallymeasures the hypnotic effects ofadministered anesthetic doses,regardless of pharmacokinetic orpharmacodynamic variability.Using BIS values and responses as aguide allows the anesthesia providerto administer a particular anestheticagent at the dose required toachieve the desired hypnotic effectin the individual patientMonitoring hypnotic depth withtechniques such as the BIS index yields clinically use-ful information because routine practice results in sig-nificant variability in anesthetic dosing and patientresponse (18).
13Qué no mide?El BIS no monitorea analgesia o respuesta autónoma o movimiento ante un estimulo.El BIS mide actividad cortical no estado de conciencia.While the EEG changes recorded on the BIScorrelate well with hypnosis and consciousness, patientmovement and autonomic responses to surgical stimuliappear to correlate more with analgesia, which is notpredicted as well as consciousness by BIS. Thus, heart rate(HR) and mean arterial blood pressure (MAP) changesduring surgery are not expected to correlate with theBIS.14T
14BIS y BNMEn ausencia de estimulo doloroso y alta actividad EMG, ninguna de las etapas del bloqueo NM afectan el monitoreo.
15Determinados agentes anestésicos y coadyuvantes Ketamina (0.5mg/kg) causa no respuesta pero no cambia el BIS. Aumento ondas alfa y betaEl O. Nitroso al 70% causa no respuesta pero no altera el BISLa efedrina, pero no la fenilefrina, puede aumentar el BISIsoflurano: se ha registrado respuesta paradójica transitoria al aumento de la dosis
16BIS y opoidesLos opiodes en general producen pocos o ningún cambio en el BIS.El remifentanil cuando se usa con propofol no modifica el BIS a dosis clinicamente utiles.Efecto de los opiodes por estructuras no corticales (locus coeruleus, sistema noradrenergico, medula espinal etc.)Brain Research, 2004, 1:
17BIS y temperatura Hipertermia no altera el BIS Hipotermia: Disminuye requerimiento gases.Por si misma es anestesicaDisminución del BIS 1.12 por cada °C disminuido.Estudios posteriores no lo confirmaneptors, liver and kidney perfusion, and metabolic rate.The depressant effect of incremental hypothermia onthe cerebral metabolic rate for oxygen is manifested onthe electroencephalogram (EEG) by the progression to anisoelectric/burst suppression pattern dominated by iso-electric periods.11Uncertainty regarding the relationship between tem-perature and BIS led us to test the hypothesis that BIS is not affected by temperature. In our study of 100 patientsundergoing cardiac surgery at constant anesthetic depth,we have demonstrated that temperature does have aneffect on the BIS, producing a 1.12 unit decrease for eachdegree Celsius decrease in body temperatureThe association between temperature and theBIS was independent of patient age, predicted brainmidazolam or fentanyl concentration, percent isofluraneadministered, and surgical time point.
19Desordenes neurologicos y BIS EEG de bajo voltajeVariante genética que puede ocurrir entre el 5-10% de la población general, <20 mV en todas las regiones del cerebro.No evidencia de disfunción cerebral.Reporte de paciente con BIS= 40, despierto, media en 3 días separados. EEG de 16 derivadas mostró bajo voltaje (determinado genéticamente).Pacientes en periodo pos ictal muestran gran predominio ondas delta (BIS <60 en 75% ptes)Anesthesiology: 1998, 89 , 1607–1608
20Despertar intraoperatorio (DIO) Un riesgo real?La supuesta causa del despertar intraoperatorio es un período deefecto anestésico inadecuado resultante de una dosis insuficiente deanestésico, interrupción de la administración de anestesia o,potencialmente, resistencia inherente a la anestesia.41Por ejemplo,en algunas situaciones clínicas, la administración de dosis muy bajasde anestésico puede ser apropiada a la luz del riesgo hemodinámicou otros objetivos clínicos. Sin embargo, estas dosis se asocian conuna mayor indidencia de despertar intraoperatorio.Algunos pacientes han relatado descripciones aterradoras dedespertar intraoperatorio en las que destacan las horrendas Algunos pacientes han relatado descripciones aterradoras dedespertar intraoperatorio en las que destacan las horrendassensaciones y emociones que pueden producirse si el efectoanestésico es inadecuado.42Los pacientes que experimentandespertar intraoperatorio pueden desarrollar un espectro delesiones psicológicas que abarcan desde síntomas moderadostransitorios hasta graves síntomas de incapacitación compatibles conel síndrome de estrés postraumático.43nesthesia awareness, also knownas unintended intraoperative awareness, isthe explicit recall of sensory perceptionsduring general anesthesia. Anesthesia awarenessis rare,1,2 but the incidence may approach 1% inpatients at high risk.3-5 Anesthesia awareness canlead to anxiety and post-traumatic stress disorder.6The Joint Commission on Accreditation of Health-care Organizations (JCAHO) has recommendedthat stringent efforts be made to prevent anesthe-sia awareness,7 and the American Society of An-esthesiologists (ASA) has published guidelines onthe subject.8 According to a sentinel-event alertdisseminated by the JCAHO, between 20,000 and40,000 cases of anesthesia awareness may occuryearly in the United States.THE problem of unexpected awareness has concernedpatients and anesthesiologists since the administration ofgeneral anesthesia was first described.1 Indeed, throughmuch of the 19th century, awareness was regarded as anundesirable and unavoidable consequence of the administrationof general anesthesia to facilitate surgery. Theincidence of awareness was probably low for much ofthe 19th century, as inhaled agents (ether, chloroform,nitrous oxide) were the sole agents used to administergeneral anesthesia and were titrated until adequate surgicalconditions were obtained. Of note, hypoxia, proTHE problem of unexpected awareness has concernedconditions were obtained. Of note, hypoxia, profoundcirculatory depression, fire, explosions, and deathwere all also well accepted and relatively frequent complicationsof general anesthesia in this era.2–4 Againstthis backdrop, the occasional patient who had recall ofintraoperative events had a relatively minor problem anda great deal to be thankful for. The incorporation ofparalytic agents into the administration of general anestheticswas associated with an epidemic of cases ofawareness, as anesthesiologists discovered that theseagents did not diminish consciousness in any way.5–9The practice of anesthesia has evolved during the past 50yr, with increasingly safer agents, increasingly reliablemonitoring, and increasing scientific understanding ofgeneral anesthesia. Death, hypoxia, and shock are nowrare events in the operating room compared with theturn of the century.2,4 However, in recent years, therehas been increased attention in the press to the problemof unexpected recall during general anesthetics.
21Factores de riesgo para DIO Anestesia superficialHipovolemiaReserva cardiaca mininaIntubación difícil anticipadaIncremento de los requerimientos anestésicosHistoria de DIOUso crónico de opiodes, BZD, alcohol.Tipo de cirugíaCesárea BAGCardiacaTraumaCirugía mayorOtrosMujeres jovenesObesidad
22BIS y despertar IO AIM trial 19.575 ptes Cohorte Prospectivo PACU y una semana después25 casos claros46 casos no confirmadosFR: ASA III-IVBIS no alteró resultadosThe term “awareness” during anesthesia, as used inthe anesthesia literature, implies that during a periodof intended general anesthesia, the brain is aroused bystimuli that are stored in memory for future explicitrecall. Patients who experience awareness will recallsuch experiences during a state of inadequate anesthe-sia.1Awareness is an uncommon phenomenon, occur-ring in about 0.1% to 0.2% of cases.2A recent study,using the data from hospitals’ quality improvementsystems, reported an incidence of 0.007%.3ProspectiveData from 19,575 patients are presented. A total of 25awareness cases were identified (0.13% incidence).These occurred at a rate of 1–2 cases per 1000 patients ateach site. Awareness was associated with increasedASA physical status (odds ratio, 2.41; 95% confidenceinterval, 1.04–5.60 for ASA status III–V compared withASAstatus I–II).Age and sex did not influence the inci-dence of awareness. There were 46 additional cases(0.24%) of possible awareness and 1183 cases (6.04%) ofpossible intraoperative dreaming. The incidence ofawareness during general anesthesia with recall in theUnited States is comparable to that described in othercountries. Assuming that approximately 20million an-esthetics are administered in the United States annu-ally,we can expect approximately 26,000 cases to occureach year.Awareness is a distressing complication ofanaesthesia.7–10Affected patients report perception ofparalysis, conversations, and surgical manipulations,accompanied by feelings of helplessness, fear, and pain.Some patients have rated it as their worst hospitalexperience;6post-traumatic stress disorder can develop inthose who are severely affected.Awareness results from an imbalance between anaes-thetic need and delivery. During any surgical procedure,the intensity of surgical stimulation, and thus anaestheticneed, varies greatly. Additionally, some patients might haveunpredictably high anesthetic requirement. On the otherhand, anaesthetic delivery may be constrained by concernsabout fetal wellbeing or haemodynamic side-effects of theanaesthetic drugs. Alternatively, insufficient anaesthesiacan be delivered as a result of technical errors or equipmentfailure.34-36Previously, anaesthetists have been unable todirectly monitor the balance between need and delivery.
23SAFE 2 Trial Estudio cohorte prospectivo con controles historicos 4945 pts vs 7826 controlesDiferencias en monitoreo de gasesSeguimiento a 15 diasAwareness with recall after general anesthesia is an in-frequent, butwell described, phenomenon thatmay re-sult in posttraumatic stress disorder. Assuming that approximately 20million an-esthetics are administered in the United States annu-ally,we can expect approximately 26,000 cases to occureach year.Awareness is caused by the administration of gen-eral anesthesia that is inadequate to maintain uncon-sciousness and to prevent recall during surgical stim-ulation. Common causes include large anestheticrequirements, equipment misuse or failure, andsmaller doses of anesthetic drugs (1). Our finding ofan increased risk of awareness with sicker patients(ASA physical status III–V) undergoing major surgery(Table 7) may reflect the use of smaller anestheticdoses and light anesthetic techniques in sicker pa-tients. However, specific details of anesthetic doses19000 patientsIn this study, BIS monitoring reduced the risk of awarenessby 82% in at-risk adults undergoing relaxant generalanaesthesia. BIS monitoring had little effect on the timeneeded to recover from general anaesthesia, as measuredby eye opening, and no measurable effect on the risks ofpostoperative complications. Our findings confirmprevious observational data suggesting that awarenessduring BIS monitoring is less common than during routinecareResultados2 vs 14 p: 0.038Reducción 77% en la incidenciaAmbos casos con BIS mayor de 60; en inducción.
24A 30 días DIO fue menor en el grupo de BIS B-Aware TrialA 30 días DIO fue menor en el grupo de BIS2 (0.17%) vs 11 (0.91%) p: 0.022NNT: 1382 casos: BIS y 55-60RCT doble ciego, multicentrico2500 ptesAlto riesgo de DIODP: Despertar IOSecundarios: tiempo de recuperación, complicaciones mayores, mortalidad a 30 díasSummaryBackground Awareness is an uncommon complication ofanaesthesia, affecting 0·1–0·2% of all surgical patients.Bispectral index (BIS) monitoring measures the depth ofanaesthesia and facilitates anaesthetic titration. In this trialwe determined whether BIS-guided anaesthesia reduced theincidence of awareness during surgery in adults.Methods We did a prospective, randomised, double-blind,multicentre trial. Adult patients at high risk of awarenesswere randomly allocated to BIS-guided anaesthesia or routinecare. Patients were assessed by a blinded observer forawareness at 2–6 h, 24–36 h, and 30 days after surgery. Anindependent committee, blinded to group identity, assessedevery report of awareness. The primary outcome measurewas confirmed awareness under anaesthesia at any time.Findings Of eligible and consenting patients, 1225were assigned to the BIS group and 1238 to the routine caregroup. There were two reports of awareness in the BIS-guidedgroup and 11 reports in the routine care group (p=0·022).BIS-guided anaesthesia reduced the risk of awareness by82% (95% CI 17–98%).Interpretation BIS-guided anaesthesia reduces the risk ofawareness in at-risk adult surgical patients undergoingrelaxant general anaesthesia. With a cost of routine BISmonitoring at US$16 per use in Australia and a numberneeded to treat of 138, the cost of preventing one case ofawareness in high-risk patients is about $2200.Lancet 2004; 363: 1757–63Until 30 days after enrolment, the number of patientswho reported awareness under anaesthesia wassignificantly smaller in the BIS group than in the routinecare group (2 [0·17%] vs 11 [0·91%]; OR 0·18; 95%adjusted CI 0·02–0·84; p=0·022); the absolute reductionin the risk of awareness was 0·74%. The number neededto treat (NNT) was 138 (95% CI 77–641). The benefit ofNo hubo diferencias en: T recuperación, complicaciones mayores, estancia en PACU, T de extubación, satisfacción del pte
252 vs 2 casos (diferencia 0%) B-Unaware TrialEl promedio de BIS fue de 43.1±9.2 vs 43.4±9.8El promedio de MAC fue de 0.81±0.25 vs 0.82±0.23Ni deferencias en consumo de gas.Problema: Incumplimiento del protocoloRCT, doble ciego2000 ptes de alto riesgoBIS vs ETAGDesenlaces: DIO, consumo de gasesIncidencia: 0.21% (95% CI, 0.08 to 0.53)2 vs 2 casos (diferencia 0%)This trial has some important limitations. Al-though the trial did not demonstrate a reductionin anesthesia awareness, with 95% confidence in-tervals for absolute risk reduction of definite an-esthesia awareness of −0.56 to 0.57%, the resultsremain consistent with a clinically significantnumber needed to treat in order to benefit of 179and a clinically significant number needed to treatin order to harm of 175 with the BIS protocol. Thisstudy is also subject to some concerns commonto all studies of anesthesia awareness: the diag-nosis of anesthesia awareness may be subjective,the awareness interview may be invalid becauserepeated questioning may induce false memories,and it may be difficult to distinguish betweenmemories of events in the operating room andevents in the intensive care unit. It is encouragingthat there was good agreement among the threeassessors, who were unaware of the treatment as-signments, and it was unnecessary to refer anydecision to a fourth assessor.It is important to emphasize that the results ofthis trial should not be extrapolated to patientsreceiving total intravenous anesthesia, which isconsidered to be a risk factor for anesthesia aware-ness.7 Indeed, BIS monitoring may be useful dur-ing total intravenous anesthesia, since it is notpresently possible to monitor the blood concentra-tions of anesthetic agents continuously.Anesthesia awareness cannot predictably beprevented in all patients with the BIS monitoringprotocol used in this study. When a potent vola-tile anesthetic gas was administered, a structuredprotocol based on the BIS was not shown to besuperior to a protocol based on ETAG concentra-tions for preventing anesthesia awareness. Reli-ance on BIS technology24 may provide patients andhealth care practitioners with a false sense of se-curity about the reduction in the risk of anesthe-sia awareness. If BIS monitoring were routinelyapplied to all patients in the United States receiv-ing general anesthesia,7 the cost of disposableelectrodes alone would exceed $360 million an-nually. Our study was unable to demonstratesuperiority of a BIS-guided protocol over an ETAG-guided protocol for preventing anesthesia aware-ness and does not provide support for the addi-tional cost of BIS monitoring as part of standardpractice.
26BIS y mortalidad Estudio prospectivo cohorte: 1064 ptes. CXs no cardiaca BAGResultadosMortalidad 0.7% a 30 dias5.5% a un añoWe report a prospective observational study evaluatingthe influence of preoperative patient characteristics andintraoperative anesthetic management on 1-year mortal-ity. Our results indicate that patient comorbidity is themost important predictor of death in the first year aftersurgery. This finding is in agreement with previousstudies that have shown an association between comor-bidity and postoperative mortality. The correlation be-tween increasing ASA physical status and the risk ofpostoperative mortality was originally reported threedecades ago (15). A prospective, longitudinal study ofcomplications associated with anesthesia found that ad-vancing age itself adds little risk in the absence of co-morbid disease (16). Our results suggest that mortality in the first yearafter surgery may be influenced by the intraoperativemanagement of the anesthetic itself, specifically themanagement of hypnotic depth and arterial bloodpressure. The independent association of cumulativedeep hypnotic time with 1-year mortality is an unex-pected new finding of our study.In conclusion, in this study of all-cause mortalityafter noncardiac surgery, we confirm that comorbidityis the major predictor of mortality after major noncar-diac surgery but find new associations between intra-operative hypotension, cumulative deep hypnotictime, and 1-year postoperative mortality. The type andduration of surgery, patient age, and other demo-graphic variables did not explain these findings. Theseassociations suggest that intraoperative anestheticmanagement may affect outcomes over longer timeperiods than previously appreciated. Clearly, largerandomized trials are needed to confirm our resultsand to determine if changes in anesthetic managementcan improve long-term outcome in high-risk patients.Death during the first yearafter surgery is primarily associated with the natural his-tory ofpreexisting conditions.However, cumulativedeephypnotic time and intraoperative hypotension were alsosignificant, independent predictors of increased mortal-ity. These associations suggest that intraoperative anes-theticmanagementmay affect outcomes over longer timeperiods than previously appreciated.PATIENTS withmultiple comorbidities undergoing car-diac surgery can be at substantial risk for perioperativeand late mortality.1Clinical factors that may affect hospitaland long-term survival have been identified over the lastseveral decades and can be grouped into patient-related andsurgery-related variables. The associations between anesthe-sia-related factors and short- and long-term survival aftercardiac surgery remain unclear. In recent years, research hasemerged suggesting that cumulative duration of a low pro-prietary processed electroencephalogram index called thebispectral index (BIS®; Aspect Medical System, Norwood,MA) may be associated with increased intermediate-term
27Mortalidad en el B-Aware trial Seguimiento de 4.1 años (rango: 0–6.5)1947 (83%) de los ptesWhen anesthesia is titrated using bispectral in-dex (BIS) monitoring, patients generally re-ceive lower doses of hypnotic drugs and, as aconsequence, they emerge faster from anesthesia withless postoperative nausea and vomiting.1–3Intraopera-tive hypotension and organ toxicity might also beavoided if lower doses of anesthetics are administered,but whether this translates into a reduction in seriousmorbidity or mortality remains controversial. Monitoring with BIS and absence of BIS values 40 for 5min were associated with improved survival and lessserious morbidity in patients enrolled in the B-Aware Trial.One explanation for this result is that simply monitoringthe depth of anesthesia is insufficient: anesthesiologistsmust also avoid low BIS values by careful titration ofhypnotic drugs to affect long-term outcome. An alternativeor additional explanation is that low BIS values reflectunderlying disease processes and trauma and that thesefactors, rather than anesthetic dosing, affect survival.5Anesth-Analg 2010;110:816–22
28Mortalidad en el B- Unaware trial 460 ptes cx cardiacaSeguimiento: 3 añosMortalidad a 30 dias:3.5% (16 of 460) vs14.3% (66 of 460) a añosThe authors studied 460 patients (mean age, 63.013.1 yr; 287men) who underwent cardiac surgery between Septem-ber 2005 and October 2006 at Washington University Medical Cen-ter, St Louis, Missouri. By using multivariable Cox regression analy-sis, perioperative factors were evaluated for their potentialassociation with intermediate-term all-cause mortalitThis study found an association between cumulativeduration of low BIS and mortality in the setting of cardiac surgery.Notably, this association was independent of both volatile anestheticconcentration and duration of anesthesia, suggesting that interme-diate-term mortality after cardiac surgery was not causally related toexcessive anesthetic dose.y.This study suggests that in patients undergoing cardiac sur-gery, similar to those undergoing noncardiac surgery,2,3cu-mulative duration of low BIS was independently associatedwith intermediate-term mortality. Importantly, however,this association was independent of total anesthetic dose.The cumulative duration of BIS less than 45 has beenidentified as a predictor of poor intermediate-term outcomein patients undergoing noncardiac surgery.The study of
29No diferencia en consumo de anestésicos. ¨El valor del BIS parece ser un fenómeno coincidental más que un evento causal.¨The findings suggest that the relationship between a lowprocessed electroencephalogram index and death is likelyepiphenomenal rather than causal. As an analogy, consider apatient who has electrocardiographic ST segment depressionwith treadmill testing. If this patient dies a year thereafter,this is more likely attributable to underlying heart diseasethan to treadmill test-induced cardiac damage. Similarly,consider a patient who has a low processed electroencepha-logram index with exposure to potent anesthetic agents anddies 1 yr thereafter. It is possible that the anesthesia exposurecontributed to the patient’s late demise. A more parsimoni-ous, albeit mundane, explanation is that the low processedelectroencephalogram index is a marker of underlying illnessor vulnerability. Theseresults in our companion study of cardiac surgery patientsindicate that BIS values lower than 45 are likelymarkers ofsystemic illness, poor cardiac function, or complicatedintraoperative course.10IANESTHESIOLOGY 2010; 112:1070–2.
30Mortalidad en cirugía no cardiaca 1,473 ptesNo asociación con BIS o cantidad de gases acumuladosSi asociación con variables ya conocidas (comorbilidades, ASA, etc)The fact that anindependent association between BIS values less than 45 andmortality has been found in some trials,5,10but not others,13including the current study, suggests that the association islikely epiphenomenal and, when present, is reflective of pa-tient factors or comorbidities rather than anesthetic manage-ment. In conclusion, this second substudy of the B-UnawareTrial found no evidence that either cumulative BIS valuesbelow a threshold of 40 or 45, or cumulative inhalationalanesthetic dose is injurious to patients. In contrast, there wasa strong association among perioperative risk factors, preex-isting malignancy, and mortality. This study does not sup-port the hypothesis that titrating anesthesia according to anarbitrary BIS threshold or limiting anesthetic dose woulddecrease intermediate-term mortality after noncardiac sur-gery. We do acknowledge, however, that only an appropri-
31Uso de BIS reduce uso de Propofol 1. 44mg/kg/hr (662 ptes; 95% CI -1 Reduce el consumo de anestésicos inhalados (desﬂurane, sevoﬂurane, isoﬂurane) en 0.14 MAC (928 ptes; 95% CI a -0.05).
32Reduce tiempo de:Apertura ocular : min, (2446 ptes; 95% CI a -1.29).Respuesta a ordenes: min, (777 ptes; 95% CI a -1.54).Extubación: min; (1488 ptes; 95% CI a -1.99).Permanencia en PACU: min (1940 ptes, 95% CI a -2.76).Alta al domicilio: min (329 ptes; 95% CI a 16.09).
33BIS y costosEn pacientes de alto riesgo (Incidencia DIO 1%) con una reducción del 78%: NNT: 138. Entonce: 138 x $= $Sin considerar mantenimiento, reparación, capacitación, compra de monitores, etc.En pacientes de bajo riesgo (Incidencia de DIO %) con una reducción del 90%, los costos para evitar un caso seria de U$.Our cost analysis used pooled cost averages for anes-thetic agents, incremental cost to reduce postoperativenausea and vomiting, and PACU costs from multiplecountries to provide a global perspective. Overall, theuse of BIS monitoring for ambulatory anesthesia is eco-nomically inefﬁcient. The minor reductions in anestheticconsumption, prevention of postoperative nausea andvomiting, and PACU time were exceeded by the cost forBIS monitoring consumables, without even includingcapital costs of monitoring systems. Adding in any addi-tional capital cost for the BIS monitoring platform wouldfurther increase the cost per patient.El uso del BIS representa 5.55 U$ más por paciente cuando se comparan beneficios contra costo de los electrodos.
34ConclusionesEl BIS es derivado de análisis estadístico de EEG y pruebas de ensayo-error.El BIS mide actividad eléctrica cortical no estado de conciencia. Siempre medir BIS antes de inducir anestesia.El BIS no monitorea analgesia o respuesta autónoma o movimiento ante un estimulo.El BIS no es únicamente un número. Para su interpretación se deberá analizar el estado clínico del paciente y el resto de factores que puedan influir en el valor numérico.
35ConclusionesEl uso del BIS reduce la incidencia de despertar intra operatorio, sobretodo en pacientes de alto riesgo y cuando se compara con anestesia guiada por signos clinicos.No esta justificado reducir los anestésicos para mantener BIS mayor de 45 para reducir mortalidad.El BIS no disminuye significativamente costos, tiempos de recuperación y cantidad de medicamentos utilizados.
36ConclusionesEs probable que la justificación del uso rutinario del BIS no sea por disminución de costos.Aspect Medical Web site:“Clinical judgment should always be used when interpreting the BIS in conjunction with other available clinical signs. Reliance on the BIS alone for intraoperative anesthetic management is not recommended.”
37“Todos somos muy ignorantes “Todos somos muy ignorantes. Lo que ocurre es que no todos ignoramos las mismas cosas”. Albert Einstein