BIS Índice Biespectral Un nuevo ¨signo vital¨

Presentación del tema: "BIS Índice Biespectral Un nuevo ¨signo vital¨"— Transcripción de la presentación:

1 BIS Índice Biespectral Un nuevo ¨signo vital¨
During the evolution of modern anesthesia practice, patient assessment has undergone gradual change and refinement. Observations of clinical signs such as pupil response, patterns of respiration, quality of the pulse and movement were first augmented by direct measurement of physiologic endpoints including blood pressure, heart rate and respiratory rate and volume. With the development of pulse oximetry and capnography, a precise assessment of ventilatory management could be made. The use of end-tidal agent analysis and peripheral nerve stimulation provided anesthesia clinicians the ability to measure pharmacologic agent concentration and effect, respectively. Today, cardiac function can be evaluated using advanced technologies that range from pulmonary artery catheters and transesophageal echocardiography to new methods of continuous blood pressure and cardiac output monitoring. Despite the remarkable improvements in assessment of the cardiovascular system during anesthesia, direct determination of the effect of the anesthetic and sedative agent(s) on the central nervous system has remained a challenge. Careful clinical investigation demonstrated that hemodynamic responses do not necessarily provide an accurate representation of the central nervous system responsiveness to anesthetic agents and therefore were unreliable indicators of brain status.1 In contrast, a technology that would permit independent neurophysiological monitoring of the central nervous system would provide a direct measure of brain status during anesthesia and sedation, allowing clinicians to fine-tune perioperative management and achieve the best possible outcome for each patient. Accurate monitoring and targeting of brain effect, in combination with assessment of clinical signs and traditional monitoring, would permit a more complete approach to adjusting the dosing and mixture of anesthetic, sedative and analgesic agents. Diomer Avendaño Q. Residente 1er año Anestesiología y Reanimación

2 Contenido Cómo funciona? BIS y consideraciones especiales
BIS y despertar intraoperatorio (DIO) BIS y mortalidad BIS y costos Conclusiones

3 Porqué aparece el BIS? ¿Está mi paciente adecuadamente anestesiado?
Analgesia Inmovilidad Relajación ¿Está mi paciente adecuadamente anestesiado? Therapeutic targeting is a clear benefit that results from BIS monitoring. Using this new parameter, the clinician can manage patients within the optimal plane of anesthesia effect, reducing the unwanted occurrence of excessive or inadequate anesthetic effect. 13 Clinical investigations of BIS monitoring during anesthesia have consistently demonstrated an average 25% reduction in intraoperative anesthetic use and a consistent reduction in the time for emergence from general anesthesia. The practice of anaesthesia is based on the concept of components of anaesthesia resulting from separate pharmacological actions of multiple 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 in order to achieve the basic goals of anaesthetic management, that is unconsciousness (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 of the conscious state of anaesthetized patients (Mahla 1997). The use of these clinical signs in judging dosage of anaesthetic agents can lead to either overdosage or underdosage, which can result in adverse effects due to too deep or too light anaesthesia. Amnesia Inconciencia

4 EEG en anestesia Cambios en anestesia general Aumento de la amplitud
Disminución en frecuencia Beta ( Hz) Alfa ( Hz) Theta ( Hz) Delta ( Hz)

5 The BIS has been de- scribed in the literature as a composite index consisting of a weighted combination of four components; how- ever, the details of the BIS algorithm have not been described in their entirety by the manufacturer of the BIS monitors. It has been reported that the four compo- nent subparameters are derived from time-domain, bispectral, and power spectral analyses of the EEG [1]. The time domain subparameter includes Quazi suppres- sion detection and the suppression ratio (SR) [1], and these two subparameters represent the deepest anesthe- sia conditions. The bispectral domain subparameter is called SyncFastSlow [1]. It represents the low- frequency feature and is associated with moderate anesthetic effect. The frequency domain subparameter is called the relative beta ratio [1]. It represents the high-frequency feature and is associated with light anes- thetic effect and beta activation. Therefore, the BIS is a combination of the four subparameters described above, and the individual subparameters make the BIS a precise, near-linear function across the continuum of clinical states from awake to isoelectric EEG. However, of the four subparameters, only the SR is available for recording via the processed EEG port.

6 Digital Signal Converter (DSC) The digital signal converter
(Figure 3) receives, amplifies and digitizes the raw EEG signal for subsequent processing and analysis. In addition, key filters and signal processing steps occur in the DSC t identify and reject certain types of electrical artifact (e.g., electrocautery filters in DSC-XP systems). The digitized EEG data travels through the DSC cable to the BIS engine. The BIS engine, the heart of the BIS system, contains the microprocessor responsible for rapid signal processing and computation of the BIS Index. Some of the steps involved in the analysis of the EEG include multiple methods of artifact detection and processing. Segments of the EEG that are compromised by 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

7 The BIS is a combination of three weighted
parameters: (i) the burst suppression ratio (the proportion of isoelectric EEG signal in an epoch); (ii) the beta ratio (a measure of the proportion of signal power in the high vs medium 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 high frequency portion of the EEG decreases, and the amplitude of the low frequencies increases. 3 These changes can be described and quanti®ed statistically. First-order statistics like the mean can be applied to the raw EEG. More useful information is obtained by applying second-order statistics like the power spectrum and the autocorrelation. However, it is conceivable that the different frequencies within the signal may not be independent of each other. If the oscillations are linked by a common phase relationship, it is necessary to use third-order statistics to extract this information. The bispectral power is said to indicate the presence of quadratic phase-coupling between different frequencies within the signal. 4 The question arises, how important is this higher-order information? Los sistemas BIS muestran el valor del Índice BIS como un valor único, calculado a partir de datos recopilados en los últimos 15 a 30 segundos de registro de EEG y actualizados cada segundo. La obtención del valor del Índice BIS a partir de varios segundos de datos de EEG “atenúa” efectivamente los datos para evitar fluctuaciones excesivas de los valores BIS. También permite determinar un valor incluso si la señal del EEG se interrumpe brevemente. La mayoría de los sistemas BIS permiten al usuario cambiar la tasa de atenuación para adecuarla al entorno clínico.

8 Evolución del algoritmo del BIS

9 BIS 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 will result in decreases in BIS. 9 For example, in the operating room, physiologic changes known to impact cerebral metabolic activity – e.g., cardiac arrest, hypothermia – have been characterized by changes in BIS. 10.11 A clear limitation of the BIS system, however, relates to its derivation from unilateral, frontal-lobe EEG signals. Clinicians must decide whether the capability and limitations of BIS monitoring may be appropriately utilized as a more encompassing and revealing measure of brain function. 12 The established link between cerebral metabolic activity and BIS values can provide revealing insights into brain function. In a recent study comparing baseline (awake) BIS values in patients with Alzheimer’s disease and multi-infarct dementia to an age-matched control group, a significant proportion of the neurologically-impaired group showed BIS values less than 93 at baseline. 13 These abnormally low values might be expected in patients with a disease process that impairs cerebral function and memory. This observation suggests: • Intraoperative BIS values (as a measure of anesthetic effect) must be interpreted more cautiously in these patients Los valores del Índice BIS pueden reflejar la tasa metabólica cerebral reducida que producen la mayoría de los agentes hipnóticos. Se observó una correlación significativa entre los valores del Índice BIS y la reducción de la actividad metabólica cerebral completa por el aumento del efecto anestésico mediante tomografía de emisión de positrones (figura 4). Sin embargo, es importante destacar que también se pueden producir cambios en el Índice BIS por factores distintos de la administración de fármacos que pueden influir en el metabolismo cerebral (por ejemplo, alteraciones de temperatura u homeostasis fisiológica). Por último, cabe observar que el valor BIS proporciona una medición del estado del cerebro derivado del EEG, no la concentración de un fármaco determinado. Por ejemplo, los valores BIS disminuyen durante el sueño natural así como durante la administración de un agente anestésico.

10 Interpretación clínica
Cuando los valores BIS disminuyen por debajo de 70, la función de memoria se reduce significativamente y la probabilidad de recuerdo explícito desciende de forma considerable. Durante la sedación, se pueden observar valores BIS >70 en niveles de sedación aparentemente adecuados. Sin embargo, en dichos niveles, puede haber una probabilidad mayor de consciencia y posibilidad de recuerdo. 3 Anesthesiology. 1997;86:836-47

11 Pantalla BIS EMG As 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

12 Por 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 concentration measurement systems (e.g., end-tidal agent concentration) do not measure anesthetic effect on the target organ, the brain. Thus, these systems cannot identify alterations in expected levels of hypnosis due to pharmacodynamic variability among patients. Rather, the existence of this variability means that identical drug concentrations commonly produce considerably different hypnotic responses among individuals or within the same person at different times. BIS monitoring continually measures the hypnotic effects of administered anesthetic doses, regardless of pharmacokinetic or pharmacodynamic variability. Using BIS values and responses as a guide allows the anesthesia provider to administer a particular anesthetic agent at the dose required to achieve the desired hypnotic effect in the individual patient Monitoring hypnotic depth with techniques such as the BIS index yields clinically use- ful information because routine practice results in sig- nificant variability in anesthetic dosing and patient response (18).

13 Qué 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 BIS correlate well with hypnosis and consciousness, patient movement and autonomic responses to surgical stimuli appear to correlate more with analgesia, which is not predicted as well as consciousness by BIS. Thus, heart rate (HR) and mean arterial blood pressure (MAP) changes during surgery are not expected to correlate with the BIS. 14 T

14 BIS y BNM En ausencia de estimulo doloroso y alta actividad EMG, ninguna de las etapas del bloqueo NM afectan el monitoreo.

15 Determinados agentes anestésicos y coadyuvantes
Ketamina (0.5mg/kg) causa no respuesta pero no cambia el BIS. Aumento ondas alfa y beta El O. Nitroso al 70% causa no respuesta pero no altera el BIS La efedrina, pero no la fenilefrina, puede aumentar el BIS Isoflurano: se ha registrado respuesta paradójica transitoria al aumento de la dosis

16 BIS y opoides Los 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:

17 BIS y temperatura Hipertermia no altera el BIS
Hipotermia: Disminuye requerimiento gases. Por si misma es anestesica Disminución del BIS 1.12 por cada °C disminuido. Estudios posteriores no lo confirman eptors, liver and kidney perfusion, and metabolic rate. The depressant effect of incremental hypothermia on the cerebral metabolic rate for oxygen is manifested on the electroencephalogram (EEG) by the progression to an isoelectric/burst suppression pattern dominated by iso- electric periods. 11 Uncertainty 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 patients undergoing cardiac surgery at constant anesthetic depth, we have demonstrated that temperature does have an effect on the BIS, producing a 1.12 unit decrease for each degree Celsius decrease in body temperature The association between temperature and the BIS was independent of patient age, predicted brain midazolam or fentanyl concentration, percent isoflurane administered, and surgical time point.

18 Pacientes con demencia

19 Desordenes neurologicos y BIS
EEG de bajo voltaje Variante 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

20 Despertar intraoperatorio (DIO)
Un riesgo real? La supuesta causa del despertar intraoperatorio es un período de efecto anestésico inadecuado resultante de una dosis insuficiente de anestésico, interrupción de la administración de anestesia o, potencialmente, resistencia inherente a la anestesia. 41 Por ejemplo, en algunas situaciones clínicas, la administración de dosis muy bajas de anestésico puede ser apropiada a la luz del riesgo hemodinámico u otros objetivos clínicos. Sin embargo, estas dosis se asocian con una mayor indidencia de despertar intraoperatorio. Algunos pacientes han relatado descripciones aterradoras de despertar intraoperatorio en las que destacan las horrendas Algunos pacientes han relatado descripciones aterradoras de despertar intraoperatorio en las que destacan las horrendas sensaciones y emociones que pueden producirse si el efecto anestésico es inadecuado. 42 Los pacientes que experimentan despertar intraoperatorio pueden desarrollar un espectro de lesiones psicológicas que abarcan desde síntomas moderados transitorios hasta graves síntomas de incapacitación compatibles con el síndrome de estrés postraumático. 43 nesthesia awareness, also known as unintended intraoperative awareness, is the explicit recall of sensory perceptions during general anesthesia. Anesthesia awareness is rare, 1,2 but the incidence may approach 1% in patients at high risk. 3-5 Anesthesia awareness can lead to anxiety and post-traumatic stress disorder. 6 The Joint Commission on Accreditation of Health- care Organizations (JCAHO) has recommended that stringent efforts be made to prevent anesthe- sia awareness, 7 and the American Society of An- esthesiologists (ASA) has published guidelines on the subject. 8 According to a sentinel-event alert disseminated by the JCAHO, between 20,000 and 40,000 cases of anesthesia awareness may occur yearly in the United States. THE problem of unexpected awareness has concerned patients and anesthesiologists since the administration of general anesthesia was first described.1 Indeed, through much of the 19th century, awareness was regarded as an undesirable and unavoidable consequence of the administration of general anesthesia to facilitate surgery. The incidence of awareness was probably low for much of the 19th century, as inhaled agents (ether, chloroform, nitrous oxide) were the sole agents used to administer general anesthesia and were titrated until adequate surgical conditions were obtained. Of note, hypoxia, proTHE problem of unexpected awareness has concerned conditions were obtained. Of note, hypoxia, profound circulatory depression, fire, explosions, and death were all also well accepted and relatively frequent complications of general anesthesia in this era.2–4 Against this backdrop, the occasional patient who had recall of intraoperative events had a relatively minor problem and a great deal to be thankful for. The incorporation of paralytic agents into the administration of general anesthetics was associated with an epidemic of cases of awareness, as anesthesiologists discovered that these agents did not diminish consciousness in any way.5–9 The practice of anesthesia has evolved during the past 50 yr, with increasingly safer agents, increasingly reliable monitoring, and increasing scientific understanding of general anesthesia. Death, hypoxia, and shock are now rare events in the operating room compared with the turn of the century.2,4 However, in recent years, there has been increased attention in the press to the problem of unexpected recall during general anesthetics.

21 Factores de riesgo para DIO
Anestesia superficial Hipovolemia Reserva cardiaca minina Intubación difícil anticipada Incremento de los requerimientos anestésicos Historia de DIO Uso crónico de opiodes, BZD, alcohol. Tipo de cirugía Cesárea BAG Cardiaca Trauma Cirugía mayor Otros Mujeres jovenes Obesidad

22 BIS y despertar IO AIM trial 19.575 ptes Cohorte Prospectivo
PACU y una semana después 25 casos claros 46 casos no confirmados FR: ASA III-IV BIS no alteró resultados The term “awareness” during anesthesia, as used in the anesthesia literature, implies that during a period of intended general anesthesia, the brain is aroused by stimuli that are stored in memory for future explicit recall. Patients who experience awareness will recall such experiences during a state of inadequate anesthe- sia. 1 Awareness is an uncommon phenomenon, occur- ring in about 0.1% to 0.2% of cases. 2 A recent study, using the data from hospitals’ quality improvement systems, reported an incidence of 0.007%. 3 Prospective Data from 19,575 patients are presented. A total of 25 awareness cases were identified (0.13% incidence). These occurred at a rate of 1–2 cases per 1000 patients at each site. Awareness was associated with increased ASA physical status (odds ratio, 2.41; 95% confidence interval, 1.04–5.60 for ASA status III–V compared with ASAstatus 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%) of possible intraoperative dreaming. The incidence of awareness during general anesthesia with recall in the United States is comparable to that described in other countries. Assuming that approximately 20million an- esthetics are administered in the United States annu- ally,we can expect approximately 26,000 cases to occur each year. Awareness is a distressing complication of anaesthesia. 7–10 Affected patients report perception of paralysis, conversations, and surgical manipulations, accompanied by feelings of helplessness, fear, and pain. Some patients have rated it as their worst hospital experience; 6 post-traumatic stress disorder can develop in those 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 anaesthetic need, varies greatly. Additionally, some patients might have unpredictably high anesthetic requirement. On the other hand, anaesthetic delivery may be constrained by concerns about fetal wellbeing or haemodynamic side-effects of the anaesthetic drugs. Alternatively, insufficient anaesthesia can be delivered as a result of technical errors or equipment failure. 34-36 Previously, anaesthetists have been unable to directly monitor the balance between need and delivery.

23 SAFE 2 Trial Estudio cohorte prospectivo con controles historicos
4945 pts vs 7826 controles Diferencias en monitoreo de gases Seguimiento a 15 dias Awareness 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 occur each 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 anesthetic requirements, equipment misuse or failure, and smaller doses of anesthetic drugs (1). Our finding of an increased risk of awareness with sicker patients (ASA physical status III–V) undergoing major surgery (Table 7) may reflect the use of smaller anesthetic doses and light anesthetic techniques in sicker pa- tients. However, specific details of anesthetic doses 19000 patients In this study, BIS monitoring reduced the risk of awareness by 82% in at-risk adults undergoing relaxant general anaesthesia. BIS monitoring had little effect on the time needed to recover from general anaesthesia, as measured by eye opening, and no measurable effect on the risks of postoperative complications. Our findings confirm previous observational data suggesting that awareness during BIS monitoring is less common than during routine care Resultados 2 vs 14 p: 0.038 Reducción 77% en la incidencia Ambos casos con BIS mayor de 60; en inducción.

24 A 30 días DIO fue menor en el grupo de BIS
B-Aware Trial A 30 días DIO fue menor en el grupo de BIS 2 (0.17%) vs 11 (0.91%) p: 0.022 NNT: 138 2 casos: BIS y 55-60 RCT doble ciego, multicentrico 2500 ptes Alto riesgo de DIO DP: Despertar IO Secundarios: tiempo de recuperación, complicaciones mayores, mortalidad a 30 días Summary Background Awareness is an uncommon complication of anaesthesia, affecting 0·1–0·2% of all surgical patients. Bispectral index (BIS) monitoring measures the depth of anaesthesia and facilitates anaesthetic titration. In this trial we determined whether BIS-guided anaesthesia reduced the incidence of awareness during surgery in adults. Methods We did a prospective, randomised, double-blind, multicentre trial. Adult patients at high risk of awareness were randomly allocated to BIS-guided anaesthesia or routine care. Patients were assessed by a blinded observer for awareness at 2–6 h, 24–36 h, and 30 days after surgery. An independent committee, blinded to group identity, assessed every report of awareness. The primary outcome measure was confirmed awareness under anaesthesia at any time. Findings Of eligible and consenting patients, 1225 were assigned to the BIS group and 1238 to the routine care group. There were two reports of awareness in the BIS-guided group and 11 reports in the routine care group (p=0·022). BIS-guided anaesthesia reduced the risk of awareness by 82% (95% CI 17–98%). Interpretation BIS-guided anaesthesia reduces the risk of awareness in at-risk adult surgical patients undergoing relaxant general anaesthesia. With a cost of routine BIS monitoring at US$16 per use in Australia and a number needed to treat of 138, the cost of preventing one case of awareness in high-risk patients is about $2200. Lancet 2004; 363: 1757–63 Until 30 days after enrolment, the number of patients who reported awareness under anaesthesia was significantly smaller in the BIS group than in the routine care group (2 [0·17%] vs 11 [0·91%]; OR 0·18; 95% adjusted CI 0·02–0·84; p=0·022); the absolute reduction in the risk of awareness was 0·74%. The number needed to treat (NNT) was 138 (95% CI 77–641). The benefit of No hubo diferencias en: T recuperación, complicaciones mayores, estancia en PACU, T de extubación, satisfacción del pte

25 2 vs 2 casos (diferencia 0%)
B-Unaware Trial El promedio de BIS fue de 43.1±9.2 vs 43.4±9.8 El promedio de MAC fue de 0.81±0.25 vs 0.82±0.23 Ni deferencias en consumo de gas. Problema: Incumplimiento del protocolo RCT, doble ciego 2000 ptes de alto riesgo BIS vs ETAG Desenlaces: DIO, consumo de gases Incidencia: 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 reduction in anesthesia awareness, with 95% confidence in- tervals for absolute risk reduction of definite an- esthesia awareness of −0.56 to 0.57%, the results remain consistent with a clinically significant number needed to treat in order to benefit of 179 and a clinically significant number needed to treat in order to harm of 175 with the BIS protocol. This study is also subject to some concerns common to all studies of anesthesia awareness: the diag- nosis of anesthesia awareness may be subjective, the awareness interview may be invalid because repeated questioning may induce false memories, and it may be difficult to distinguish between memories of events in the operating room and events in the intensive care unit. It is encouraging that there was good agreement among the three assessors, who were unaware of the treatment as- signments, and it was unnecessary to refer any decision to a fourth assessor. It is important to emphasize that the results of this trial should not be extrapolated to patients receiving total intravenous anesthesia, which is considered to be a risk factor for anesthesia aware- ness. 7 Indeed, BIS monitoring may be useful dur- ing total intravenous anesthesia, since it is not presently possible to monitor the blood concentra- tions of anesthetic agents continuously. Anesthesia awareness cannot predictably be prevented in all patients with the BIS monitoring protocol used in this study. When a potent vola- tile anesthetic gas was administered, a structured protocol based on the BIS was not shown to be superior to a protocol based on ETAG concentra- tions for preventing anesthesia awareness. Reli- ance on BIS technology24 may provide patients and health care practitioners with a false sense of se- curity about the reduction in the risk of anesthe- sia awareness. If BIS monitoring were routinely applied to all patients in the United States receiv- ing general anesthesia, 7 the cost of disposable electrodes alone would exceed $360 million an- nually. Our study was unable to demonstrate superiority 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 standard practice.

26 BIS y mortalidad Estudio prospectivo cohorte: 1064 ptes.
CXs no cardiaca BAG Resultados Mortalidad 0.7% a 30 dias 5.5% a un año We report a prospective observational study evaluating the influence of preoperative patient characteristics and intraoperative anesthetic management on 1-year mortal- ity. Our results indicate that patient comorbidity is the most important predictor of death in the first year after surgery. This finding is in agreement with previous studies that have shown an association between comor- bidity and postoperative mortality. The correlation be- tween increasing ASA physical status and the risk of postoperative mortality was originally reported three decades ago (15). A prospective, longitudinal study of complications 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 year after surgery may be influenced by the intraoperative management of the anesthetic itself, specifically the management of hypnotic depth and arterial blood pressure. The independent association of cumulative deep hypnotic time with 1-year mortality is an unex- pected new finding of our study. In conclusion, in this study of all-cause mortality after noncardiac surgery, we confirm that comorbidity is the major predictor of mortality after major noncar- diac surgery but find new associations between intra- operative hypotension, cumulative deep hypnotic time, and 1-year postoperative mortality. The type and duration of surgery, patient age, and other demo- graphic variables did not explain these findings. These associations suggest that intraoperative anesthetic management may affect outcomes over longer time periods than previously appreciated. Clearly, large randomized trials are needed to confirm our results and to determine if changes in anesthetic management can improve long-term outcome in high-risk patients. Death during the first year after surgery is primarily associated with the natural his- tory ofpreexisting conditions.However, cumulativedeep hypnotic time and intraoperative hypotension were also significant, independent predictors of increased mortal- ity. These associations suggest that intraoperative anes- theticmanagementmay affect outcomes over longer time periods than previously appreciated. PATIENTS withmultiple comorbidities undergoing car- diac surgery can be at substantial risk for perioperative and late mortality. 1 Clinical factors that may affect hospital and long-term survival have been identified over the last several decades and can be grouped into patient-related and surgery-related variables. The associations between anesthe- sia-related factors and short- and long-term survival after cardiac surgery remain unclear. In recent years, research has emerged suggesting that cumulative duration of a low pro- prietary processed electroencephalogram index called the bispectral index (BIS®; Aspect Medical System, Norwood, MA) may be associated with increased intermediate-term

27 Mortalidad en el B-Aware trial
Seguimiento de 4.1 años (rango: 0–6.5) 1947 (83%) de los ptes When anesthesia is titrated using bispectral in- dex (BIS) monitoring, patients generally re- ceive lower doses of hypnotic drugs and, as a consequence, they emerge faster from anesthesia with less postoperative nausea and vomiting. 1–3 Intraopera- tive hypotension and organ toxicity might also be avoided if lower doses of anesthetics are administered, but whether this translates into a reduction in serious morbidity or mortality remains controversial. Monitoring with BIS and absence of BIS values 40 for 5 min were associated with improved survival and less serious morbidity in patients enrolled in the B-Aware Trial. One explanation for this result is that simply monitoring the depth of anesthesia is insufficient: anesthesiologists must also avoid low BIS values by careful titration of hypnotic drugs to affect long-term outcome. An alternative or additional explanation is that low BIS values reflect underlying disease processes and trauma and that these factors, rather than anesthetic dosing, affect survival. 5 Anesth-Analg 2010;110:816–22

28 Mortalidad en el B- Unaware trial
460 ptes cx cardiaca Seguimiento: 3 años Mortalidad a 30 dias: 3.5% (16 of 460) vs 14.3% (66 of 460) a años The authors studied 460 patients (mean age, 63.0 13.1 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 potential association with intermediate-term all-cause mortalitThis study found an association between cumulative duration of low BIS and mortality in the setting of cardiac surgery. Notably, this association was independent of both volatile anesthetic concentration and duration of anesthesia, suggesting that interme- diate-term mortality after cardiac surgery was not causally related to excessive anesthetic dose.y. This study suggests that in patients undergoing cardiac sur- gery, similar to those undergoing noncardiac surgery, 2,3 cu- mulative duration of low BIS was independently associated with intermediate-term mortality. Importantly, however, this association was independent of total anesthetic dose. The cumulative duration of BIS less than 45 has been identified as a predictor of poor intermediate-term outcome in patients undergoing noncardiac surgery. The study of

29 No 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 low processed electroencephalogram index and death is likely epiphenomenal rather than causal. As an analogy, consider a patient who has electrocardiographic ST segment depression with treadmill testing. If this patient dies a year thereafter, this is more likely attributable to underlying heart disease than to treadmill test-induced cardiac damage. Similarly, consider a patient who has a low processed electroencepha- logram index with exposure to potent anesthetic agents and dies 1 yr thereafter. It is possible that the anesthesia exposure contributed to the patient’s late demise. A more parsimoni- ous, albeit mundane, explanation is that the low processed electroencephalogram index is a marker of underlying illness or vulnerability. These results in our companion study of cardiac surgery patients indicate that BIS values lower than 45 are likelymarkers of systemic illness, poor cardiac function, or complicated intraoperative course. 10 I ANESTHESIOLOGY 2010; 112:1070–2.

30 Mortalidad en cirugía no cardiaca
1,473 ptes No asociación con BIS o cantidad de gases acumulados Si asociación con variables ya conocidas (comorbilidades, ASA, etc) The fact that an independent association between BIS values less than 45 and mortality has been found in some trials, 5,10 but not others, 13 including the current study, suggests that the association is likely 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-Unaware Trial found no evidence that either cumulative BIS values below a threshold of 40 or 45, or cumulative inhalational anesthetic dose is injurious to patients. In contrast, there was a strong association among perioperative risk factors, preex- isting malignancy, and mortality. This study does not sup- port the hypothesis that titrating anesthesia according to an arbitrary BIS threshold or limiting anesthetic dose would decrease intermediate-term mortality after noncardiac sur- gery. We do acknowledge, however, that only an appropri-

31 Uso 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).

32 Reduce 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).

33 BIS y costos En 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$. Our cost analysis used pooled cost averages for anes- thetic agents, incremental cost to reduce postoperative nausea and vomiting, and PACU costs from multiple countries to provide a global perspective. Overall, the use of BIS monitoring for ambulatory anesthesia is eco- nomically inefficient. The minor reductions in anesthetic consumption, prevention of postoperative nausea and vomiting, and PACU time were exceeded by the cost for BIS monitoring consumables, without even including capital costs of monitoring systems. Adding in any addi- tional capital cost for the BIS monitoring platform would further increase the cost per patient. El uso del BIS representa 5.55 U$ más por paciente cuando se comparan beneficios contra costo de los electrodos.

34 Conclusiones El 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.

35 Conclusiones El 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.

36 Conclusiones Es 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

38 Gracias por su atención. . .