[Electroencephalographic and hemodynamic monitoring at various desflurane concentrations]. / Monitorización electroencefalográfica y hemodinámica a diferentes concentraciones de desflurano.

OBJECTIVES: To assess the electroencephalographic patterns and hemodynamic changes produced by desflurane at 0.5, 1 and 1.5 MAC. MATERIAL AND METHODS: Twenty-four patients undergoing gynecological surgery under general anesthesia were enrolled prospectively. We monitored electroencephalographic (EEG) patterns and hemodynamic parameters as well as inspired and expired desflurane fractions. Anesthetic induction was with 2 mg/kg of propofol, 2 to 3 mg/kg of fentanyl and 0.1 mg/kg vecuronium. Spectral edge frequency (SEF90) and the EEG delta ratio were recorded along with mean systolic and diastolic pressures, heart rate, oxygen saturation and expired CO2 fraction during induction, intubation, 5 min after intubation and at 0.5, 1 and 1.5 MAC during weaning from anesthesia and extubation. RESULTS: Blood pressure fell significantly at 1.5 MAC and increased when anesthesia was withdrawn; heart rate did not change significantly. SEF90 and the delta ratio changed, however, at each phase. SEF90 fell notably at the moment of induction but gradually increased, rising upon intubation, 5 min later, at 0.5 MAC and upon withdrawal of anesthesia. A significant decrease in SEF90 appeared when 1.5 MAC was reached, related to achievement of a deeper plane of anesthesia. CONCLUSIONS: Automated EEG processing can provide a good measure of depth of anesthesia, as it reflects significant changes related to level of anesthesia at each phase. These differences are not always observable with routine monitoring of hemodynamic parameters.

[Changes in the bispectral index and the spectral edge frequency 90 during different phases of anesthesia with sevoflurane]. / Cambios del índice biespectral y del límite espectral 90% (LE90) en las distintas fases de la anestesia con sevoflurano en la cirugía abdominal.

INTRODUCTION: Electroencephalographic monitoring is one of the techniques used to measure hypnosis during anesthesia. Efforts to find a means to apply this monitoring function are justified by cases of intraoperative awakening and are in the interest of guaranteeing patient welfare and controlling anesthesia. OBJECTIVES: To determine the changes in two electroencephalographic parameters, the bispectral index (BIS) and the spectral edge frequency 90 (SEF90), during the different phases of anesthesia. Patients and method. Forty-eight patients undergoing abdominal surgery were studied prospectively. Anesthesia was induced by propofol, fentanyl or sevoflurane. Anesthesia was maintained with sevoflurane and O2/N2O at a concentration of 70% to maintain BIS between 40 and 60. Variables monitored were heart rate, blood pressure, arterial oxygen saturation (with a pulse oximeter), expired CO2 partial pressure, inspired and expired sevoflurane partial pressure, esophageal temperature, SEF90 (defined as the frequency below which 90% of the power in the electroencephalogram resides) and BIS. All variables were recorded during three phases: induction, maintenance and recovery from anesthesia. We then performed an analysis of variance, with p < 0.05 considered significant. RESULTS: During induction mean BIS decreased from 95.6 to 34.7 after intubation, while SEF90 fell from 20.5 Hz to 11.9 Hz. During maintenance BIS, SEF90 and expired sevoflurane partial pressure remained constant. During recovery mean BIS increased from 59.2 to 92.3 upon extubation, and SEF90 went from 15.1 to 22.2 Hz; although heart rate increased, blood pressure did not. The mean electroencephalographic values recorded when movement occurred were 77 for BIS (range 58-96) and 18 for SEF90 (range 13-18). CONCLUSION: Electroencephalographic monitoring is useful for distinguishing between states of consciousness and unconsciousness during anesthesia, and is valid for the phases of induction and recovery. BIS values over 58 and SEF90 values over 13 may indicate inadequate hypnosis.

[Efficacy of topical administration of lidocaine through a Malinckrodt Hi-Lo Jet tube in lessening cough during recovery from general anesthesia]. / La eficacia de la administración tópica de lidocaína a través del tubo Malinckrodt Hi-Lo Jet para atenuar la tos en el despertar de la anestesia general.

To achieve tracheal anesthesia during intubation, an endotracheal tube was purposely designed. The tube had multiple laser-induced perforations in its lower portion produced that allowed administration of the local anesthetic in a pulverized form. We evaluated the efficacy of lidocaine 2% in preventing cough during recovery from general anesthesia. The goal of this study was to perform a topical anesthesia of the hypopharynx, larynx, and trachea. This attenuates the laryngeal reflex occurring during anesthesia recovery and therefore, prevents from potential complications. Sixteen patients ASA I-II underwent surgery with general anesthesia. They were prospectively studied following a randomized double blind protocol. The control group received saline infusion (n = 6) whereas the experimental group (n = 10) was treated with lidocaine. At the end of the anesthesia period, the presence of cough was treated with the test solution. In 90% of cases treated with lidocaine, cough disappeared in about 30 seconds and patients tolerated the endotracheal tube until extubation was performed. All patients who received saline solution presented cough until extubation.

[Usefulness of pulse oximetry in thoracic surgery]. / Utilidad de la pulsioximetría en cirugía torácica.

Saturation of hemoglobin in arterial blood was simultaneously measured by co-oximetry (SaO2) and by pulse oximetry (SpO2) in 228 samples from 42 patients undergoing general anesthesia for thoracic surgery. Data was referred to SaO2 obtained with arterial catheterization. We found a significant correlation (r: 0.949 and p less than 0.001) and the mean differences were 0.77 +/- 1.84. The correlation between PaO2 and the difference among both methods was significantly negative (r: -0.20; p less than 0.001). Although there was a significant correlation, the method loses reliability and accuracy in patients with hypoxemia. In these patients oximetric values are slightly lower than those obtained with arterial cannulation. We emphasize the clinical usefulness of this technique since it is instantaneous and allowed immediate therapeutic actions.

[The incidence of intraoperative conciousness in emergency surgery and its possible relation to the post-traumatic stress syndrome. Presentation of three cases]. / Incidencia de conciencia intraoperatoria en cirugía urgente y su posible relación con el síndrome de estrés postraumático. A propósito de tres casos.

Intraoperative awakening and recall of specific events is a rare complication (0.2 to 1.3%) of surgery. The possibility of developing serious psychiatric complications, such as posttraumatic stress disorder (PTSD) makes the prevention and detection of intraoperative awareness a subject of special interest. We describe our experience with three patients in whom awareness was detected during emergency surgery under general anesthesia. We conducted two structured interviews with the patients three months after surgery in order to detect the possible development of psychiatric complications. One patient suffered insomnia and reexperience of the event during the first two weeks after surgery. Improvement was spontaneous. None of the patients suffered PTSD. Efforts to decrease the incidence of episodes of intraoperative awakening with specific recall must be based on clinical observation and exhaustive monitoring of the patient, including anesthetic gases, given that no ideal method of monitoring depth of anesthesia exists. Cases should be detected in the first few days after surgery by means of a specific test. Likewise, possible causes for the episode should be explained to the patient, who should be followed for six months so that early diagnosis of PTSD or other psychiatric complications can be made.

[Shock. Antioxidant immunologico-therapeutic replacement]. / Consideraciones acerca del shock. Substitución inmunológica-terapéutica antioxidante.

Shock is a specific reaction to a non specific severe injury. The organic reaction is a biphasic (excitation/depression) threefold response: haemodynamic, hemostatic and immunologic. The physiopathology is related with changes produced by injury on macrophages, neutrophils, platelets and endothelial cells. The release of enzymes and certain vasoactive compounds enhance activation of neutrophils, which produce great amounts of free oxygen radicals. Therapy must be basically substitutive, including immunologic substitution. Therapeutic trends are based on the use of substances which can avoid the overproduction or nocive effects of free oxygen radicals.

[Prevention of cross contamination, patient to anesthesia apparatus to patient, using filters]. / Profilaxis de la contaminación cruzada, enfermo-aparato de anestesia-enfermo, mediante filtros.

Concern for cross infections from patient to patient via apparatus is particularly relevant today. There are several ways to prevent patient contamination through anesthetic devices. Although there is no clinical evidence for using one alternative over another and each hospital establishes its own hygienic protocols, we have introduced the systematic use of filters with patients undergoing general anesthesia. We describe the features of filters available on the market and our protocol for their use. The efficacy of a filter depends on whether bacteria or viruses are to be controlled. Filters can be classified into three groups or generations based on mesh quality: 1) heat and humidity exchangers (HHE), with large mesh screens that allow water to pass through; 2) bacterial filters (FHHE), with finer mesh that is permeable to droplets of water and 3) folded membrane filters (FHHE) that are hydrophobic, with very fine mesh that stops water. We describe three basic physical tests (passage of water, passage of smoke and increase of resistance when applied to the patient) for filters to be classified. The ideal filter is hydrophobic and does not increase circuit resistance over the amount specified. Four principles are emphasized in the protocol: 1) the filter forms a part of the patient, not the apparatus; 2) proper placement of the filter is between the patient and the circuit's "Y" piece; 3) the main purpose of the filter is to prevent contamination of the apparatus, and 4) if a hydrophobic filter is used with each patient, the use of a disposable respiratory circuit is not called for.