RESUMEN
This case conference reports two cases of epidural anesthesia in which air was used to identify the epidural space during a loss-of-resistance placement technique. Both patients subsequently complained of severe pain and subdural air was demonstrated in case 1 by computed tomography and in case 2 by magnetic resonance imaging. The possible causes of the pain syndrome experienced by both patients are discussed.
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Anestesia Epidural/efectos adversos , Anestesia Obstétrica/efectos adversos , Dolor Postoperatorio/etiología , Espacio Subdural/fisiología , Adulto , Anciano , Artroplastia de Reemplazo de Cadera , Femenino , Humanos , Masculino , Oxígeno/sangre , Consumo de Oxígeno/fisiología , Dolor Postoperatorio/diagnóstico por imagen , Embarazo , Reoperación , Espacio Subdural/diagnóstico por imagen , Tomografía Computarizada por Rayos XRESUMEN
We describe a model for simulating a spontaneous electroencephalogram (EEG) and for simulating the effects of anesthesia on the EEG, to allow anesthesiologists and EEG technicians to learn and practice intraoperative EEG monitoring. For this purpose, we developed a linear model to manipulate the amplitude of the activity in each of the traditional EEG frequency bands. Burst suppression patterns are simulated by manipulating an overall gain. To demonstrate the model feasibility, model parameters for thiopental and isoflurane were estimated guided by published data on the EEG effects of these anesthetic drugs. Using these estimates, EEG time signals were simulated for isoflurane at various partial pressures, and for bolus intravenous doses of thiopental. Comparison with actual recorded EEG signals showed that the changes produced by isoflurane and thiopental in the simulated signals are very similar to the changes in the actual signals, which was confirmed by two clinicians with experience and routine practice in intraoperative EEG monitoring.
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Anestesiología/educación , Simulación por Computador , Educación Médica/métodos , Electroencefalografía/efectos de los fármacos , Cuidados Intraoperatorios , Anestésicos/administración & dosificación , Anestésicos/farmacocinética , Anestésicos/farmacología , Electroencefalografía/métodos , Estudios de Factibilidad , Humanos , Isoflurano/administración & dosificación , Isoflurano/farmacocinética , Isoflurano/farmacología , Modelos Lineales , Tiopental/administración & dosificación , Tiopental/farmacocinética , Tiopental/farmacología , Estados Unidos , Recursos HumanosRESUMEN
This article reviews the basic anesthetic considerations for ESWL and PCNL. General principles governing the operation of lithotripters, elements of treatment that impinge on safety, and effective intraoperative anesthesia and complications that may be encountered in the perioperative period are discussed. Factors influencing blood loss and concerns arising from positioning patients prone are addressed in the sections devoted to PCNL.
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Anestesia/métodos , Cálculos Renales/terapia , Litotricia , Nefrostomía Percutánea , Anestesia/efectos adversos , Humanos , Litotricia/efectos adversos , Nefrostomía Percutánea/efectos adversosRESUMEN
Intraoperative cardiac arrest is uncommon. We describe a case of intraoperative cardiac arrest in a patient undergoing anesthesia for surgical repair of an intracranial arteriovenous malformation (AVM).
Asunto(s)
Paro Cardíaco/etiología , Malformaciones Arteriovenosas Intracraneales/cirugía , Complicaciones Intraoperatorias , Anestesia por Inhalación , Anestesia Intravenosa , Hemorragia Cerebral/cirugía , Enfermedad Coronaria/complicaciones , Humanos , Hipotensión/etiología , Masculino , Persona de Mediana Edad , Infarto del Miocardio/etiología , Taquicardia Ventricular/etiologíaRESUMEN
BACKGROUND: The authors compared the performance of a prototype intubation aid that incorporated plastic illumination and image guides into a stylet with fiberoptic bronchoscopy and direct laryngoscopy for tracheal intubation by novice users. METHODS: In a randomized, nonblinded design, patients were assigned to direct laryngoscopy, fiberoptic bronchoscopy, or imaging stylet intubation groups. The quality of laryngeal view and ease with which it was attained for each intubation was graded by the laryngoscopist. Time to intubation was measured in 1-min increments. A sore-throat severity grade was obtained after operation. RESULTS: There were no differences in demographic, physical examination, or surgical course characteristics among the groups. The laryngoscope produced an adequate laryngeal view more easily than did the imaging stylet or bronchoscope (P = 0.001) but caused the highest incidence of postoperative sore throat (P<0.05). Although the time to intubation for direct laryngoscopy was shorter than for imaging stylet, which was shorter than fiberoptic bronchoscopy (P<0.05), the quality of laryngeal view with the imaging stylet was inferior to both direct laryngoscopy and fiberoptic bronchoscopy techniques (P<0.05). CONCLUSIONS: Novices using the imaging stylet produce fewer cases of sore throat (compared with direct laryngoscopy) and can intubate faster than when using a bronchoscope in anesthetized adult patients. The imaging stylet may be a useful aid for tracheal intubation, especially for those unable to maintain skills with a bronchoscope.
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Intubación Intratraqueal/instrumentación , Adulto , Anciano , Broncoscopía , Femenino , Tecnología de Fibra Óptica , Humanos , Laringoscopía , Masculino , Persona de Mediana Edad , Fibras ÓpticasRESUMEN
OBJECTIVE: To implement a realistic autoregulation mechanism to enhance an existing educational brain model that displays in real-time the cerebral metabolic rate (CMRO2), cerebral blood flow (CBF), cerebral blood volume (CBV), intracranial pressure (ICP), and cerebral perfusion pressure (CPP). METHODS: A dynamic cerebrovascular resistance (CVR) feedback loop adjusts automatically to maintain CBF within a range of the CPP and defines autoregulation. The model obtains physiologic parameters from a full-scale patient simulator. We assumed that oxygen demand and arterial partial pressure of carbon dioxide (CO2 responsivity) are the two major factors involved in determining CBF. In addition, our brain model increases oxygen extraction up to 70% once CBF becomes insufficient to support CMRO2. The model was validated against data from the literature. RESULTS: The model's response varied less than 9% from the literature data. Similarly, based on correlation coefficients between the brain model and experimental data, a good fit was obtained for curves describing the relationship between CBF and PaCO2 at a mean arterial blood pressure of 150 mm Hg (R2 = 0.92) and 100 mm Hg (R2 = 0.70). DISCUSSION: The autoregulated brain model, with incorporated CO2 responsivity and a variable oxygen extraction, automatically produces changes in CVR, CBF, CBV, and ICP consistent with literature reports, when run concurrently with a METI full-scale patient simulator (Medical Education Technologies, Inc., Sarasota, Florida). Once the model is enhanced to include herniation, vasospasm, and drug effects, its utility will be expanded beyond demonstrating only basic neuroanesthesia concepts.
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Encéfalo/irrigación sanguínea , Encéfalo/fisiología , Simulación por Computador , Modelos Biológicos , Modelos Educacionales , Consumo de Oxígeno , Homeostasis , Humanos , Presión Intracraneal , Perfusión , Flujo Sanguíneo Regional , Resistencia VascularRESUMEN
OBJECTIVE: We set out to establish whether a novel plastic optical fiber incorporated into an endotracheal tube (ETT) stylet could be used for intubation of a dog. A secondary objective examined the need for a direct illumination source from a laryngoscope. Lastly, the fragility of the system was tested. METHODS: An anesthetized dog was repeatedly intubated using a laryngoscope to elevate the tongue and the view of the larynx conducted through the plastic optical fiber stylet (placed within an endotracheal tube) and displayed on a television monitor. Four prototype identical stylets were tested. Repeated intubations were attempted with each stylet and graded as either successful or failed. All four stylets were tested 10 times each using a Miller 4 blade and direct illumination from the laryngoscope. Two of the four stylets were reused during an additional 10 intubation attempts using a Miller 4 blade and laryngoscope (without batteries) with only ambient light. Finally, one stylet was used for intubation after 10, 20, 30, 40 and 50 sharp 90 degree bend-and-straighten cycles using a Miller 4 blade and laryngoscope for direct illumination. RESULTS: All attempted intubations were successful. However, the image quality was dramatically better when direct illumination from a laryngoscope was used than when ambient light was used. One plastic optical fiber stylet was successfully used to intubate after having been used for 20 intubations and 50 sharp 90 degree bend-and-straighten cycles. A partial lens separation occurred between the 41st and 50th bend cycle but the image remained adequate enough to successfully intubate again. CONCLUSIONS: A novel plastic optical fiber incorporated into an ETT stylet can be used with a laryngoscope for intubation of a dog. Direct illumination from a laryngoscope provides a better television monitor image than when only ambient light is used. The system was durable, withstanding over 20 uses and 40 sharp bend-and-straighten cycles before a lens separation failure occurred.
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Tecnología de Fibra Óptica , Intubación Intratraqueal/instrumentación , Plásticos , Animales , Perros , Diseño de Equipo , Laringoscopios , Fibras ÓpticasRESUMEN
STUDY OBJECTIVE: To determine the effect of dilution with intravascular volume expanders commonly used by anesthesiologists on clinically relevant levels of free serum ketorolac. DESIGN: In vitro study. SETTING: Pharmaceutics laboratory of a medical college. INTERVENTIONS: The effect of 6% hydroxyethylstarch, 5% albumin, 6% dextran 60, and lactated Ringer's solution on in vitro plasma protein binding of ketorolac was investigated by ultrafiltration. The binding was studied at three different drug concentrations: low therapeutic (0.3 microgram/ml), high therapeutic (3 micrograms/ml), and toxic (10 micrograms/ml), and at two or more volume expander dilutions. MEASUREMENTS AND MAIN RESULTS: The effect of plasma dilution on free ketorolac was consistent across all volume expanders tested and for each ketorolac concentration studied. As the plasma dilution with albumin, hydroxyethylstarch, dextran 60, or lactated Ringer's solution increased, the unbound ketorolac also increased from 3.2% to 3.3% in undiluted plasma to 5.0% to 8.7% in 50% dilution of the plasma with the investigated expanders. Dilution of plasma by only 10% resulted in a significant, but relatively minor, increase of unbound ketorolac to 3.2% to 3.8%. CONCLUSION: Because of the pharmacokinetic properties of ketorolac, this pharmacokinetic interaction can be expected to have only minor effects on unbound ketorolac concentrations when ketorolac is administered after the plasma expander. When ketorolac administration is followed by rapid plasma expander infusion, a transient increase of unbound ketorolac in plasma can be expected.
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Antiinflamatorios no Esteroideos/metabolismo , Proteínas Sanguíneas/metabolismo , Sustitutos del Plasma/farmacología , Tolmetina/análogos & derivados , Humanos , Ketorolaco , Unión Proteica , Tolmetina/efectos adversos , Tolmetina/metabolismoRESUMEN
The ability to visualize intracranial dynamics during simulated clinical scenarios is a valuable tool for teaching brain physiology and the consequences of different medical interventions on the brain. Studies have isolated physiologic variables and shown their effects on brain dynamics. However, no studies have shown the combined effects of these variables on intracranial dynamics. This brain model offers one approach that brings all these relationships together and shows how they affect the dynamics of the brain. The brain model obtains its physiologic inputs from a full-scale patient simulator which responds to clinical interventions. This integration allows individuals working on the patient simulator to see the effects of their actions on brain dynamics. The brain model gives a real-time display of intracranial events (cerebral metabolic rate, cerebral blood flow, cerebral blood volume, cerebral perfusion pressure, and intracranial pressure) and responds to changes in the pulmonary and cardiovascular condition of the patient simulator.
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Encéfalo/fisiología , Simulación por Computador , Modelos Neurológicos , Volumen Sanguíneo , Lesiones Encefálicas/fisiopatología , Circulación Cerebrovascular , Humanos , Presión Intracraneal , Presión Parcial , Atención al Paciente , PerfusiónRESUMEN
One of the sources of error in pulse oximetry readings is associated with an abnormal signal-to-noise ratio. The pulse oximeter distinguishes the light absorbance of arterial blood from that of other absorbers by differentiating between a constant component and a pulsating component. The pulsating component is almost exclusively the result of arteriolar bed pulsations. Because pulse oximetry is based on the assumption that arterial blood is the only pulsatile absorber, any other fluctuating phenomenon could constitute a source of error. We report a case in which a low pulse oximetry reading was associated with concomitant use of a pulse oximeter and a peripheral nerve stimulator on the same arm. Further tests conducted using a nerve stimulator and a sensory evoked potential stimulator with different amplitudes and frequencies confirmed the association and delineated the relationship between frequency and amplitude of stimulation and the degree of artificial desaturation. A theoretical explanation for this phenomenon is presented.
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Estimulación Eléctrica/efectos adversos , Potenciales Evocados Somatosensoriales/fisiología , Oximetría/instrumentación , Estimulación Eléctrica/instrumentación , Reacciones Falso Positivas , Humanos , Periodo Intraoperatorio , Masculino , Persona de Mediana Edad , Oximetría/efectos adversos , Oxígeno/sangre , Nervios Periféricos/fisiologíaRESUMEN
OBJECTIVE: To show that an integrated graphic data display can shorten the time taken to detect and correctly identify critical events during anesthesia. METHODS: We developed a graphic display which presents 30 anesthesia-related physiologic variables as shapes and colors, rather than traditional digits and waveforms. To evaluate the new display, we produced four critical events on a computer-based anesthesia simulator and asked two groups of five anesthesiologists to identify the events as quickly as possible. One group observed the new display while the other group viewed a traditional cardiovascular monitor with digital and waveform displays. RESULTS: The group which observed the integrated graphic display saw changes caused by inadequate paralysis 2.4 min sooner, and changes caused by a cuff leak 3.1 min sooner than those observing the traditional display. The integrated display group correctly identified the reason for the change 2.8 min sooner for inadequate paralysis, 3.1 min sooner for cuff leak and 3.1 min sooner for bleeding. These differences were all statistically significant. CONCLUSIONS: The results show that some simulated critical events are detected and correctly identified sooner, when an anesthesiologist views an integrated graphic display, rather than a traditional digital/waveform monitor.
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Anestesiología/instrumentación , Gráficos por Computador , Sistemas de Computación , Monitoreo Intraoperatorio/instrumentación , Adulto , Anestesia General , Anestesia por Inhalación , Pérdida de Sangre Quirúrgica , Presión Sanguínea , Transfusión Sanguínea , Compuestos de Calcio , Dióxido de Carbono/metabolismo , Gasto Cardíaco , Simulación por Computador , Falla de Equipo , Fluidoterapia , Frecuencia Cardíaca , Humanos , Intubación Intratraqueal/instrumentación , Modelos Biológicos , Monitoreo Intraoperatorio/métodos , Bloqueo Neuromuscular , Óxidos , Oxígeno/sangre , Respiración con Presión Positiva , Respiración , Hidróxido de Sodio , Programas Informáticos , Integración de Sistemas , Factores de TiempoAsunto(s)
Monitoreo Fisiológico , Óptica y Fotónica , Oximetría , Humanos , Monitoreo Intraoperatorio , FotopletismografíaRESUMEN
Somatosensory evoked potentials were determined in three patients with hysterical neurologic deficits after minor trauma. In each case the patient denied any sensation of the stimulus in the affected extremity; however, normal evoked potentials were recorded. Objective evidence of the hysterical nature of the neurologic deficit was, therefore, provided.
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Trastornos de Conversión/diagnóstico , Potenciales Evocados Somatosensoriales , Histeria/diagnóstico , Paraplejía/diagnóstico , Adulto , Encéfalo/fisiopatología , Femenino , Humanos , MasculinoAsunto(s)
Hierro/sangre , Estrés Fisiológico/sangre , Natación , Adolescente , Adulto , Humanos , Masculino , Resistencia FísicaRESUMEN
Recent technological advances have led to increased interest in intraoperative evoked potential monitoring. Although theoretically valuable, its precise role remains to be defined, and useful criteria for predicting neurological deficit are not well established. The authors used brain-stem auditory evoked potential (BAEP) monitoring during 21 posterior fossa microvascular decompression procedures to assess the value of this technique in predicting postoperative deficit. The surgeon was notified only if there was complete disappearance of wave V. Although no patients had postoperative deafness, BAEP latencies changed significantly in all cases. In four patients, wave V totally disappeared during cerebellar retraction. The BAEP appears to be a very sensitive monitor of auditory function, such that "false positive" results will be frequent if latency criteria alone are used to trigger alterations in surgical technique.