Avaliação da resposta hemodinâmica cerebral através da monitorização com a espectroscopia próxima ao infravermelho (NIRS) em pacientes com doença aterosclerótica da artéria carótida submetidos a endarterectomia / Evaluation of the brain hemodynamic response by means of near-infrared spectroscopy (NIRS) monitoring in patients with atherosclerotic carotid disease undergoing endarterectomy

Resumo Contexto A espectroscopia próxima ao infravermelho (NIRS) é uma técnica não invasiva que detecta as alterações hemodinâmicas teciduais. A NIRS pode monitorar de forma contínua as informações fisiológicas vasculares intracranianas. Por ser portátil, ela pode ser utilizada à beira do leito e no centro cirúrgico. Objetivos Avaliar as possíveis alterações hemodinâmicas cerebrais durante a endarterectomia em pacientes com estenoses maiores que 70% utilizando NIRS. Métodos Foram avaliados 10 voluntários portadores de doença carotídea aterosclerótica com indicação de endarterectomia. Após a seleção dos pacientes, que responderam um questionário com dados epidemiológicos e informações referentes à presença de comorbidades, a doença foi confirmada por métodos diagnósticos. No procedimento cirúrgico, utilizou-se a NIRS para monitorização. Foram avaliadas as variáveis saturação de oxigênio (SatO2), hemoglobina total (HbT), hemoglobina reduzida (HbR) e hemoglobina oxigenada (HbO) nos três tempos cirúrgicos pré-, trans e pós-clampeamento carotídeo. Utilizou-se p < 0,05 como nível de significância. Resultados A avaliação dos resultados obtidos por meio das medidas registradas pela NIRS permite afirmar que HbR e SatO2 variam ao longo das etapas da cirurgia. Durante o clampeamento, a variável HbR mostra valores mais elevados que nas outras duas etapas da cirurgia. Por outro lado, a variável SatO2 mostra redução durante o clampeamento. Conclusões A NIRS é um método viável e aplicável de monitorização intracerebral, não invasivo e em tempo real, durante a endarterectomia carotídea, capaz de medir de forma precisa as mudanças das condições hemodinâmicas capilares intracerebrais.

Abstract Backgrounds Near-infrared spectroscopy (NIRS) is non-invasive technique that detects hemodynamic alterations in tissues. It enables continuous monitoring of intracerebral vascular physiologic information. Due to its portable nature, NIRS may be used bedside or in the operating room. Objectives To evaluate use of NIRS for intraoperative monitoring of the brain hemodynamic response, during carotid endarterectomy. Methods 10 patients with atherosclerotic carotid disease scheduled for endarterectomy were evaluated. After patients had been selected, they answered a questionnaire on epidemiological data and information about comorbidities and then carotid disease was confirmed with diagnostic methods. NRIS monitoring was used during the surgical procedure. The variables analyzed before, during and after carotid clamping were oxygen saturation (SatO2), total hemoglobin (THb), reduced hemoglobin (RHb), and oxyhemoglobin (OHb). A p value of <0.05 was considered statistically significant. Results The results obtained from NIRS show that RHb and SatO2 vary during the different stages of surgery. RHb levels are higher during clamping, when compared with the other two surgical stages. On the other hand, SatO2 is lower during clamping. Conclusions During carotid endarterectomy, NIRS is a feasible, real-time, and non-invasive intracranial monitoring method that accurately and reliably measures the changes in intracerebral capillary hemodynamic conditions.

Aplicação do monitor Narcotrend® para avaliar a profundidade da anestesia em crianças submetidas à cirurgia cardíaca: estudo prospectivo e controlado / Application of Narcotrend® monitor for evaluation of depth of anesthesia in infants undergoing cardiac surgery: a prospective control study / Aplicación del monitor Narcotrend® para evaluar la profundidad de la anestesia en niños sometidos a la cirugía cardíaca: estudio prospectivo y controlado

JUSTIFICATIVA E OBJETIVOS: Investigar a eficácia clínica, segurança e viabilidade do monitor Narcotrend® para avaliar a profundidade da anestesia em crianças com doença cardíaca congênita (DCC) submetidas à cirurgia cardíaca. MÉTODOS: Foram randomicamente selecionadas 80 crianças submetidas à anestesia geral em cirurgia seletiva. As crianças foram divididas em dois grupos de forma aleatória (n = 40 por grupo). No grupo Narcotrend, a profundidade da anestesia foi monitorada com o Narcotrend. No grupo padrão, a profundidade da anestesia foi controlada de acordo com a experiência clínica. A pressão arterial média (PAM) e a frequência cardíaca (FC) foram determinadas e a dose de fentanil e relaxante muscular e os tempos de recuperação e de extubação foram registrados. RESULTADOS: Em ambos os grupos, os sinais vitais apresentaram-se estáveis durante a cirurgia. No grupo Narcotrend, a PAM e a FC foram mais estáveis, a dose total de fentanil e relaxante muscular significativamente menor e os tempos de recuperação e extubação acentuadamente mais reduzidos em comparação com o grupo padrão. CONCLUSÃO: A aplicação do monitor Narcotrend para medir a profundidade da anestesia foi útil para controlar a profundidade da anestesia em crianças com DCC que receberam anestesia intravenosa total, na qual uma pequena quantidade de narcóticos pode obter a anestesia ideal. Além disso, os tempos de recuperação e extubação foram menores e os efeitos secundários, como sensibilização intraoperatória, puderam ser evitados.

BACKGROUND AND OBJECTIVES: To investigate the clinic effectiveness, safety and feasibility of Narcotrend® monitor for evaluation of depth of anesthesia in congenital heart disease (CHD) infants undergoing cardiac surgery. METHODS: A total of 80 infants receiving general anesthesia in selective surgery were randomly selected. Infants were assigned into two groups (n = 40 per group). In the Narcotrend group, the depth of anesthesia was monitored with the Narcotrend monitor. In the standard group, the depth of anesthesia was controlled according to the experience. The mean arterial pressure (MAP) and heart rate (HR) were determined, as well as the dose of fentanyl, muscle relaxant, recovery time and extubation time were recorded. RESULTS: In both groups, vital signs were stable during the surgery. When compared with the standard group, the MAP and HR were more stable, the total dose of fentanyl and muscle relaxant were significantly reduced and the recovery time and extubation time were markedly shortened in the Narcotrend group. CONCLUSION: The application of Narcotrend monitor was beneficial to the control of the depth of anesthesia in CHD infants receiving total intravenous anesthesia, in which small amount of narcotics can achieve optimal anesthesia. Moreover, the recovery time and extubation time are reduced and the harmful consequence such as intraoperative awareness can be avoided.

JUSTIFICATIVA Y OBJETIVOS: Investigar la eficacia clínica, la seguridad y la viabilidad del monitor Narcotrend® para evaluar la profundidad de la anestesia en niños con enfermedad cardíaca congénita (ECC) sometidos a la cirugía cardíaca. MÉTODOS: Un total de 80 niños sometidos a la anestesia general en cirugía selectiva fueron seleccionados aleatoriamente. Los niños fueron divididos en dos grupos de forma aleatoria (N = 40 por grupo). En el grupo Narcotrend, la profundidad de la anestesia se monitorizó con el monitor Narcotrend. En el grupo estándar, la profundidad de la anestesia fue controlada de acuerdo con la experiencia. Se midieron la presión arterial promedio (PAP) y la frecuencia cardíaca (FC). Fueron registrados también la dosis de fentanilo y de relajante muscular junto con los tiempos de recuperación y de desentubación. RESULTADOS: En los dos grupos, los signos vitales se mantuvieron estables durante la cirugía. En el grupo Narcotrend, la PAP y la FC fueron más estables, la dosis total de fentanilo y de relajante muscular significativamente menor y los tiempos de recuperación y desentubación ostensiblemente más reducidos en comparación con el grupo estándar. CONCLUSIONES: La aplicación del monitor Narcotrend para medir la profundidad de la anestesia fue útil en el control de la profundidad de la anestesia en niños con ECC que reciben anestesia intravenosa total, en donde una pequeña cantidad de narcóticos puede alcanzar la anestesia ideal. Además, los tiempos de recuperación y desentubación fueron menores, y el efecto secundario, como la sensibilización intraoperatoria, pudo ser evitado.

Medida do fluxo intraoperatório com fluxômetro TTFM nos enxertos coronários: resultados de amostra nacional / Intraoperative coronary grafts flow measurement using the TTFM flowmeter: results from a domestic sample

OBJETIVO: Avaliar a perviedade dos enxertos no intraoperatório e identificar enxertos com risco de oclusão precoce. MÉTODOS: Cinquenta e quatro pacientes foram submetidos à revascularização do miocárdio e foi utilizado o fluxômetro (Medtronic Medi-Stim) que utiliza o método de tempo de trânsito (TTFM) para avaliação do fluxo nos enxertos. Três pacientes tinham lesão de tronco de artéria coronária esquerda e 48 apresentavam função ventricular normal ou pouco comprometida. RESULTADOS: A mortalidade hospitalar foi de dois (3,7%) pacientes, um por trombose mesentérica e outro por choque cardiogênico. Dezessete (31,4%) pacientes foram operados sem circulação extracorpórea (CEC). O fluxo no enxerto arterial variou de 8 a 106 ml/min, com média de 31,14 ml/min, e nos enxertos venosos de 9 a 149 ml/min, com média de 50,42 ml/min. CONCLUSÃO: O fluxômetro representa maior segurança para o cirurgião e para o paciente. Até mesmo sob o aspecto legal essa documentação dos enxertos pérvios evitará questionamentos futuros.

OBJECTIVE: To evaluate intraoperative graft patency and identify grafts under risk of early occlusion. METHODS: Fifty four patients were submitted to coronary artery bypass surgery and the graft flow was assessed by the Flowmeter (Medtronic Medistim), which utilizes the TTFM method. Three patients had left main disease and 48 had normal or mildly reduced left ventricular function. RESULTS: In hospital mortality was 3.7% (two patients), one for mesenteric thrombosis and one due to cardiogenic chock. Seventeen patients (34%) were submitted to off pump CABG. Arterial Graft flow measures ranged from 8 to 106 ml/min (average 31.14 ml/min), and venous grafts flow ranged from 9 to 149 ml/min (average 50.42 ml/min). CONCLUSION: Flowmeter use represents higher safety both for patients and surgeons. Even under legal aspects, the documentation provided by the device can avoid future questionings.

Comparison of transthoracic electrical bioimpedance cardiac output measurement with thermodilution method in post coronary artery bypass graft patients.

Transthoracic electrical bioimpedance (TEB) has been proposed as a non-invasive, continuous, and cost-effective method of cardiac output (CO) measurement. In this prospective, non-randomized, clinical study, we measured CO with NICOMON (Larsen and Toubro Ltd., Mysore, India) and compared it with thermodilution (TD) method in patients after off-pump coronary artery bypass (OPCAB) graft surgery. We also evaluated the effect of ventilation (mechanical and spontaneous) on the measurement of CO by the two methods. Forty-six post-OPCAB patients were studied at five predefined time points during controlled ventilation and at five time points when breathing spontaneously. A total of 230 data pairs of CO were obtained. During controlled ventilation, TD CO values ranged from 2.29 to 6.74 L/min (mean 4.45 ± 0.85 L/min), while TEB CO values ranged from 1.70 to 6.90 L/min (mean 4.43 ± 0.94 L/min). The average correlation (r) was 0.548 (P = 0.0002), accompanied by a bias of 0.015 L/min and precision of 0.859 L/min. In spontaneously breathing patients, TD CO values ranged from 2.66 to 6.92 L/min (mean 4.66 ± 0.76 L/min), while TEB CO values ranged from 3.08 to 6.90 L/min (mean 4.72 ± 0.82 L/min). Their average correlation was relatively poor (r = 0.469, P= 0.002), accompanied by a bias of −0.059 L/min and precision of 0.818 L/min. The overall percent errors between TD CO and TEB CO were 19.3% (during controlled ventilation) and 17.4% (during spontaneous breathing), respectively. To conclude, a fair correlation was found between TD CO and TEB CO measurements among post-OPCAB patients during controlled ventilation. However, the correlation was weak in spontaneously breathing patients.

Butorphanol premedication to facilitate invasive monitoring in cardiac surgery patients before induction of anaesthesia.

Cannulations (peripheral vein, radial artery and jugular vein) performed for invasive monitoring before induction of anaesthesia in cardiac surgery patients may be associated with stress and anxiety. The efficacy and safety of butorphanol premedication was assessed in setting up of invasive monitoring. The study was a prospective, randomized, double blind, placebo controlled one with 70 patients undergoing elective cardiac surgery. In group-1 patients (n = 35) (placebo) intramuscular saline was administered 1-2 hours before the surgery in equivalent volume to butorphanol. In group-2 (n = 35) butorphanol (1, 1.5 and 2 mg for three body weight groups < 40 kg, 41-60 kg and> 60 kg, respectively) was administered 1-2 hours before surgery. Observer blinded for medication recorded the sedation score, pupil size and pain after each cannulation using visual analogue score (VAS). Student's 't' test and Chi-square test for proportions, Mann-Whitney test for non-parametric data was carried out. The median pain score of cannulation in group-2 (butorphanol) in the hand (10 mm) and neck (20 mm) were significantly (P < 0.05) lower than group-1 (placebo) patients (hand = 30 mm and neck = 40 mm). Pain during neck cannulation was significantly (P < 0.05) reduced (VAS < 30 mm) in patients with the pupil size of < 2.5 mm. Since the pain during neck cannulation was more than pain during hand cannulations in both the groups, we conclude that the intensity of pain depends also upon the site of cannulation. Besides the analgesic effect of butorphanol, its sedative effect helped to effectively decrease the pain during neck cannulation in conscious patients.

Cardiac output monitoring.

Minimally invasive and non-invasive methods of estimation of cardiac output (CO) were developed to overcome the limitations of invasive nature of pulmonary artery catheterization (PAC) and direct Fick method used for the measurement of stroke volume (SV). The important minimally invasive techniques available are: oesophageal Doppler monitoring (ODM), the derivative Fick method (using partial carbon dioxide (CO2 ) breathing), transpulmonary thermodilution, lithium indicator dilution, pulse contour and pulse power analysis. Impedance cardiography is probably the only non-invasive technique in true sense. It provides information about haemodynamic status without the risk, cost and skill associated with the other invasive or minimally invasive techniques. It is important to understand what is really being measured and what assumptions and calculations have been incorporated with respect to a monitoring device. Understanding the basic principles of the above techniques as well as their advantages and limitations may be useful. In addition, the clinical validation of new techniques is necessary to convince that these new tools provide reliable measurements. In this review the physics behind the working of ODM, partial CO2 breathing, transpulmonary thermodilution and lithium dilution techniques are dealt with. The physical and the physiological aspects underlying the pulse contour and pulse power analyses, various pulse contour techniques, their development, advantages and limitations are also covered. The principle of thoracic bioimpedance along with computation of CO from changes in thoracic impedance is explained. The purpose of the review is to help us minimize the dogmatic nature of practice favouring one technique or the other.

Accuflow an infusion rate monitor: an evaluation in pediatric patients.

OBJECTIVE: To evaluate the accuracy of ACCUFLOW an infusion rate monitor as compared to manual reading in pediatric surgical patients. METHODS: An observational study in 47 pediatric patients undergoing elective surgical procedures and needing an intravenous fluid with expected duration of infusion of at least one hour. The infusion rate was adjusted to the required flow rate with the help of the display on the ACCUFLOW. The flow rate as indicated by the ACCUFLOW display was checked every 15 minutes till the end of one hour. A simultaneous record of manual readings was also made. RESULTS: A total of 470 observations were made over the one hour observation period. The infusion rate as observed on the LCD display of the ACCUFLOW compared well with manual reading. A Bland Altman analysis showed the bias between the readings with the two methods to be very small and that there is no significant difference between the methods over the drop rate of 61-74 drops/min. In addition an alarm was heard in 9 cases. The alarm was mainly because of no flow or excess flow (3 cases each). Other causes for the alarm included slow flow, faulty i.v. lines showing fluctuations in flow rate and drip chamber not placed properly (1 patient each). CONCLUSION: ACCUFLOW is a low cost device that can be used to adjust and monitor the infusion flow rate. The alarm would alert the nursing staff when there is deviation from the preset rate of infusion. ACCUFLOW could thus be an attractive option for infusion rate monitoring in developing countries with limited healthcare resources and skewed patient nurse ratios. However applicability to infants and younger children and for longer infusions needs to be determined.

Oximetría cerebral durante paro circulatorio hipotérmico y perfusión cerebral retrógrada / Cerebral oximetry during hypothermic circulatory arrest with retrograde cerebral perfusion

Se presenta el caso de una paciente de 54 años que ingresa con el diagnóstico de disección aórtica tipo A. La reparación del defecto y reemplazo se realiza con paro circulatorio hipotérmico profundo por comprometer el nacimiento del tronco braquiocefálico y perfusión cerebral retrógrada como método de protección cerebral. Durante todo el procedimiento se monitorizó la oximetría cerebral regional para evaluar disminuciones de la saturación y riesgo de isquemia en relación a cambios en la hemodinamia asociados al paro circulatorio, a la perfusión cerebral retrógrada y a las distintas medidas tomadas para aumentar el periodo libre de isquemia durante el paro. La disminución de la oximetría se relaciona a disminución del aporte de oxígeno, y por lo tanto, a un mayor riesgo de isquemia. En el presente caso, se observó el beneficio del uso de perfusión cerebral retrógrada como método de protección cerebral.

A case report of a 54 year patient with a type A aortic disecction is presented. Because of braquiocephalic compromise, the surgery was performed under deep hypotermic circulatory arrest. Retrograde cerebral perfusion was used for cerebral protection. Regional cerebral oxymetry was monitored during the entire procedure in order to correlate hemodynamic changes associated to circulatory arrest with reduction of saturation, risk of ischemia and therapeutics used for augmenting ischemic free periods. The reduction of oxygen supply correlates with low oxygen deliver and with high risk of ischemia. Benefits in cerebral protection were seen with the use of retrograde cerebral perfusion.

Comparison of simultaneous estimation of cardiac output by four techniques in patients undergoing off-pump coronary artery bypass surgery--a prospective observational study.

We prospectively compared four techniques of cardiac output measurement: bolus thermodilution cardiac output (TDCO), continuous cardiac output (CCO), pulse contour cardiac output (PiCCO), and Flowtrac (FCCO), simultaneously in fifteen patients undergoing off-pump coronary artery bypass grafting (OPCAB). All the patients received pulmonary artery catheter (capable of measuring both bolus thermodilution cardiac output and CCO), PiCCO arterial cannula in the left and FCCO in the right femoral artery. Cardiac indices (CI) were obtained every fifteen minutes by using all the four techniques. TDCO was treated as 'control' and the rest were treated as 'test' values. Interchangeability of techniques with TDCO was assessed by Bland and Altman plotting and mountain plot. Four hundred and thirty eight sets of data were obtained from fifteen patients. The values of cardiac output varied between 1 to 6.9 L/min. We found that the values of all the techniques were interchangeable. At certain times, the values of CI measured by both PiCCO and FCCO appeared erratic. The values of CI measured simultaneously appeared in the following descending order of accuracy; TDCO>CCO>FCCO>PiCCO (the % times TDCO correlated with CCO, FCCO, PiCCO was 93, 86 and 80 respectively). The bias and precision (in L/min) for CCO were 0.03, 0.06, PiCCO 0.13, 0.1 and flowtrac 0.15, 0.04 respectively suggesting interchangeability. We conclude that the cardiac output measured by CCO technique and the pulse contour as measured by PiCCO and FCCO were interchangeable with TDCO more than 80% of the times.

Clip readjustment in aneurysm surgery after flow evaluation using the ultrasonic perivascular probe: case report

A medida quantitativa do fluxo sanguíneo nos vasos cerebrais durante a cirurgia de aneurisma pode ajudar na prevenção de eventos isquêmicos e, portanto, melhorar os resultados. Relatamos o caso de paciente portador de aneurisma grande e complexo da bifurcação da artéria de cerebral média (ACM), no qual foram usadas micro-sondas ultrasônicas perivasculares para medir o fluxo de sangue quantitativamente na ACM e nos seus ramos antes e depois da clipagem do aneurisma. Após a clipagem do aneurisma, o fluxo de sangue diminuiu em todos os ramos, fazendo-se necessário o reajuste do clipe. Após vários ajustes na posição do clipe, o fluxo sanguíneo nos segmentos da ACM foi restabelecido. A descoberta imediata da alteração do fluxo de sangue proporcionou a oportunidade ao cirurgião de ajuste do clipe e conseqüentemente o restabelecimento do fluxo a valores compatíveis àqueles antes da clipagem. O uso de micro-sondas ultrasônicas perivasculares para medida do fluxo sanguíneo durante a cirurgia de aneurisma pode prevenir eventos isquêmicos e eventualmente déficits neurológicos.

Ecocardiografía transesofágica intraoperatoria: monitorización hemodinámica durante cirugía no cardíaca / Intraoperative transesophageal echocardiography: hemodynamic monitoring during non cardiac surgery

Introducción: La ecocardiografía transesofágica (ETE) puede ser de utilidad para monitorizar la hemodinamia intraoperatorio de pacientes con riesgo cardiovascular durante cirugía no cardíaca. Sin embargo sus indicaciones y utilidad clínica han sido poco estudiadas en nuestro medio. Objetivo: evaluar el uso de ETE intraoperatorio realizado por anestesiólogos durante cirugía no cardíaca. Métodos: Se monitorizó con un transductor transesofágico multiplanar a 218 pacientes (66 ± 8 años) con alto riesgo cardiovascular sometidos a cirugía no cardíaca; 61 por ciento fueron hombres. Se evaluó la utilidad de la monitorización hemodinámica con ETE en cada enfermo respecto de decidir cambios en el manejo perioperatorio dependientes de los hallazgos ecocardiográficos. Los pacientes fueron clasificados en 4 grupos: grupo 1= sin cambios en el manejo; grupo 2= cambio en manejo de volúmenes y drogas; grupo 3= cambios en el manejo postoperatorio y grupo 4= sustituto de catéter de arteria pulmonar. Resultados: En todos los casos se logró insertar el transductor y obtener visiones satisfactorias. En 96 casos (44 por ciento) hubo cambios en el aporte de volúmenes y fármacos guiados por ETE (grupo 2). En un 25 por ciento de los pacientes, por hallazgos ecocardiográficos hubo cambios postoperatorio (grupo 3). En 30 por ciento no se indicó Swan Ganz guiándose el manejo hemodinámico por la ETE (grupo 4). Conclusiones: La monitorización hemodinámica intraoperatoria con ETE realizada por anestesiólogos demostró alta utilidad, ya que implicó cambios de diagnóstico y conducta en la mayoría de pacientes monitorizados durante cirugía no cardíaca incluidos en esta serie.

Monitorización hemodinámica intraoperatoria con ecocardiografía transesofágica: experiencia clínica / Intraoperatory hemodynamic monitoring with transesophageal echocardiography

Background: Transesophageal echocardiography allows a semi-invasive hemodynamic monitoring, during cardiac and non cardiac surgery. The benefits of such surveillance must be assessed, since it may help to change patient management. Aim: To assess the usefulness of transesophageal echocardiography during surgical procedures in critical patients. Material and methods: Based on the indications of the North American Societies of Cardiology and Anesthesiology, 264 patients were monitored using a multiplanar transducer. The type of surgery, insertion difficulties, quality of visualization, complications and usefulness of the method were recorded. Results: One hundred eleven cardiac and 153 non cardiac surgical procedures were monitored. In 97 percent of cases, visualization was good. In 2 cases, it was impossible to obtain a transgastric axis. No complications of the procedure were recorded. The method was useless in nine patients, helpful to change drug and volume management in 126 (48 percent) patients, helpful to change perioperative management in 49 (19 percent) patients and was a substitute for pulmonary artery catheterization in 79 (30 percent) patients. Conclusions: Intraoperative transesophageal echocardiography is a safe technique that renders high quality images, with a low incidence of complications and that, when well indicated, orients therapeutic changes in 98 percent of patients.

Algo más sobre el monitoreo del paciente bajo anaestesia / Something more about monitoring of the patient during anesthesia

Si se quiere evitar accidentes asociados con la administración de la anestesia durante la cirugía, es evidente que el anestesiólogo debe estar en condiciones de reconocer, medir, evaluar y controlar las modificaciones que se operan en el paciente durante el transcurso del acto médico que se está llevando a cabo. La introducción de nuevos procedimientos de monitoreo y de nuevos fármacos con acciones más específicas y menos efectos colaterales ha cambiado sustancialmente la morbimortalidad del paciente bajo cuidado anestésico. En su sentido más específico, el monitor es empleado para medir variables fisiológicas mediante señales generadas por el paciente. Eso equivale no sólo a reconocer la presencia de la cuestión que demanda nuestra atención, sino, además, a interpretar los datos aportados por el sistema, decidir cuándo ellos se alejan de los límites aceptados como "normales", tomar las decisiones apropiadas para anular los efectos negativos que sobre el organismo pudiese tener el fenómeno y, finalmente, evaluar la eficacia de la acción tomada y la necesidad de su posible corrección. El monitoreo se transforma, así, en un proceso intelectual dinámico y activo, cuya eficacia está intimamente relacionada con la naturaleza y el número de los sistemas de vigilancia que se utilicen y con los conocimientos y la experiencia vivida, simulada o aprendida por el anestesiólogo acerca de los episodios con que puede enfrentarse en la práctica concreta del momento.

Anestesia inhalatoria con circuito cerrado y flujos mínimos / Inhalatory anesthesia with closed circuit and minimum flows

La anestesia inhalatoria con circuito cerrado y flujos mínimos es la técnica más apropiada para suministrar al paciente la cantidad "exacta" de los agentes inhalatorios necesarios para lograr la concentración y la presión deseadas en el sistema nervioso central y en el aire alveolar espirado. Además, con esta técnica, es posible llevar al paciente al plano de anestesia quirúrgica que necesita y mantenerlo allí, así como reducir la pérdida de calor y humedad, al no tener que calentar y humidificar grandes volúmenes de gases frescos, factores que permitirán que el paciente se encuentre en una condición más confortable y permanezca hemodinámicamente estable. Por otra parte, la anestesia inhalatoria con circuito cerrado y flujos mínimos disminuye la contaminación del quirófano y del medio ambiente con vapores anestésicos, al restringir al mínimo la polución generada por estos vapores, y reduce enormemente el costo de la anestesia al consumir cantidades ínfimas de agentes inahalatorios. Para lograr los objetivos mencionados se requiere la capacitación y el entrenamiento del anestesiólogo en la técnica de los circuitos cerrados con flujos mínimos, la disponibilidad de máquinas de anestesia y ventiladores adecuados y la existencia de monitores multiparamétricos que permitan controlar la fracción inspirada y la fracción espirada de los agentes inhalatorios.

Current status of cardiac anaesthesia.

Cardiac anaesthesia continues to advance at a rapid pace. Many innovations in monitoring and pharmacology have wide application in patients with cardiac disease. In recent years many new cardiac procedures have been introduced to improve results and reduce cost. Anaesthesia for these procedures (e.g., mid-cab, port-access) requires special training and experience so as to reduce morbidity and mortality. Recently short acting anaesthetic agents are used to permit early extubation as a part of fast tracking. Constant vigilance and monitoring are necessary to handle potentially dangerous situations and avoid complications.

Un sistema de alarmas inteligentes para vigilancia continua durante cirugía y postoperatorio cardiovascular / An intelligent system of alarm for continuous monitoring during cardiac surgery and postoperative intensive care

Se presenta un sistema experto capaz de integrar la información de siete variables fisiológicas de pacientes en cirugía y postoperatorio cardiovascular. El sistema está basado en lógica difusa y funciona bajo condiciones de información ruidosa o incompleta. El estado del paciente es estimado por medio de análisis simultáneo de las variables e integración de ellas. Las alarmas son reportadas en forma unificada por medio de un mensaje escrito en la pantalla. El sistema fue implementado en un computador personal para vigilancia continua y simultánea de hasta 9 pacientes. El sistema fue comparado con monitores convencionales (SpaceLabsTM PC2) en 20 cirugías cardíacas. Las alarmas reportadas por cada sistema fueron registradas por dos observadores expertos (un médico, un ingeniero) y clasificadas como verdaderas o falsas. Un 75 por ciento de las alarmas reportadas por los monitores convencionales fueron falsas, mientras que menos de un 1 por ciento de las alarmas reportadas por el sistema experto fueron falsas. La sensibilidad de los monitores convencionales fue de 79 por ciento y la del sistema experto de un 92 por ciento. El valor predictivo positivo fue un 31 por ciento con los monitores convencionales y un 97 por ciento con el sistema experto. En conclusion, la confiabilidad de las alarmas mejoró significativamente al integrar información de varias variables, reduciendo notablemente la frecuencia de alarmas falsas. La lógica difusa fue una herramienta poderosa y útil para integrar información fisiológica

Neuromonitorización transoperatoria / Transoperative neuromonitoring

El proposito de este capítulo es revisar la neuromonitorización en quirófano coincidiendo con los metodos actuales y trasmitir nuestra experiencia en la práctica de ellos en nuestro hospital. En quirófano la monitorización de las variables más frecuentes (frecuencia cardiaca, presión arterial, SaO2, temperatura, hemoglobina), son visualizados en forma continua como un monitoreo básico. Estos son de valor para mostrar en todo momento lo referente al flujo sanguíneo cerebral en su componente arterial, de la presión de perfusión cerebral (PPC). El componente venoso es la presión en las venas en el espacio subaracnoideo, esto es bien medido por la presión intracraneana (PIC). La actividad eléctricacerebral (EEG), potenciales evocados (PE), saturación venosa yugularde oxigeno (SVjO2); son monitoreos avanzados empleados en forma opcional, dependiendo de las necesidades quirúrgicas y de la capacidad económica del hospital