RESUMEN
PURPOSE OF REVIEW: Medication administration errors represent a significant yet preventable cause of patient harm in the peripartum period. Implementation of best practices contained in this manuscript can significantly reduce medication errors and associated patient harm. RECENT FINDINGS: Cases of medication errors involving unintended intrathecal administration of tranexamic acid highlight the need to improve medication safety in peripartum patients and obstetric anesthesia. SUMMARY: In obstetric anesthesia, medication errors can include wrong medication, dose, route, time, patient, or infusion setting. These errors are often underreported, have the potential to be catastrophic, and most can be prevented. Implementation of various types of best practice cost effective mitigation strategies include recommendations to improve drug labeling, optimize storage, determine correct medication prior to administration, use non-Luer epidural and intravenous connection ports, follow patient monitoring guidelines, use smart pumps and protocols for all infusions, disseminate medication safety educational material, and optimize staffing models. Vigilance in patient care and implementation of improved patient safety measures are urgently needed to decrease harm to mothers and newborns worldwide.
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Anestesia Obstétrica , Errores de Medicación , Humanos , Errores de Medicación/prevención & control , Embarazo , Anestesia Obstétrica/métodos , Anestesia Obstétrica/efectos adversos , Anestesia Obstétrica/normas , Femenino , Seguridad del Paciente/normas , Etiquetado de Medicamentos/normas , Ácido Tranexámico/administración & dosificación , Ácido Tranexámico/efectos adversos , Recién NacidoRESUMEN
Maternal-fetal surgery is a rapidly evolving specialty, and significant progress has been made over the last 3 decades. A wide range of maternal-fetal interventions are being performed at different stages of pregnancy across multiple fetal therapy centers worldwide, and the anesthetic technique has evolved over the years. The American Society of Anesthesiologists (ASA) recognizes the important role of the anesthesiologist in the multidisciplinary approach to these maternal-fetal interventions and convened a collaborative workgroup with representatives from the ASA Committees of Obstetric and Pediatric Anesthesia and the Board of Directors of the North American Fetal Therapy Network. This consensus statement describes the comprehensive preoperative evaluation, intraoperative anesthetic management, and postoperative care for the different types of maternal-fetal interventions.
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Analgesia Obstétrica , Anestesia Obstétrica , Enfermedades Fetales/cirugía , Terapias Fetales , Procedimientos Quirúrgicos Obstétricos , Complicaciones del Embarazo/cirugía , Analgesia Obstétrica/efectos adversos , Anestesia Obstétrica/efectos adversos , Consenso , Femenino , Terapias Fetales/efectos adversos , Humanos , Procedimientos Quirúrgicos Mínimamente Invasivos , Procedimientos Quirúrgicos Obstétricos/efectos adversos , Complicaciones Posoperatorias/etiología , Embarazo , Medición de Riesgo , Factores de Riesgo , Resultado del TratamientoRESUMEN
A wide range of fetal interventions are being performed worldwide to save the fetus's life, prevent permanent fetal organ damage, and allow a successful transition to extrauterine life. However, these are invasive procedures and can be associated with serious complications. This article focuses on promoting a culture of safety by highlighting five common error traps while anesthetizing patients for fetal interventions. They include failure to preserve uteroplacental perfusion and gas exchange, failure to achieve adequate uterine relaxation prior to hysterotomy, failure to monitor the fetus and prepare for fetal/neonatal resuscitation, failure to prepare for maternal hemorrhage, and failure to promptly treat uterine atony. Practical tips for avoiding these serious complications will also be discussed.
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Anestesia , Enfermedades Fetales , Enfermedades Fetales/cirugía , Feto , Humanos , Recién Nacido , ResucitaciónRESUMEN
INTRODUCTION: A wide range of fetal interventions are performed across fetal therapy centers (FTCs). We hypothesized that there is significant variability in anesthesia staffing and anesthetic techniques. METHODS: We conducted an online survey of anesthesiology directors at every FTC within the North American Fetal Therapy Network (NAFTNet). The survey included details of fetal interventions performed in 2018, anesthesia staffing models, anesthetic techniques, fetal monitoring, and postoperative management. RESULTS: There was a 92% response rate. Most FTCs are located within an adult hospital and employ a small team of anesthesiologists. There is heterogeneity when evaluating anesthesiology fellowship training and staffing, indicating there is a multidisciplinary specialty team-based approach even within anesthesiology. Minimally invasive fetal interventions were the most commonly performed. The majority of FTCs also performed ex utero intrapartum treatment (EXIT) and open mid-gestation procedures under general anesthesia (GA). Compared to FTCs only performing minimally invasive procedures, FTCs performing open fetal procedures were more likely to have a pediatric surgeon as director and performed more minimally invasive procedures. CONCLUSIONS: There is considerable variability in anesthesia staffing, caseload, and anesthetic techniques among FTCs in NAFTNet. Most FTCs used maternal sedation for minimally invasive procedures and GA for EXIT and open fetal surgeries.
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Anestesia , Anestesiología , Enfermedades Fetales , Terapias Fetales , Adulto , Niño , Femenino , Enfermedades Fetales/cirugía , Humanos , América del Norte , EmbarazoRESUMEN
BACKGROUND: Minimally invasive fetal surgery is commonly performed to treat twin-to-twin transfusion syndrome with selective fetoscopic laser photocoagulation and twin-reversed arterial perfusion sequence using radiofrequency ablation. Although an increasing number of centers worldwide are performing these procedures, anesthetic management varies. Both neuraxial anesthesia and monitored anesthesia care with local anesthesia are used at different institutions. We sought to determine the efficacy and outcomes of these 2 anesthetic techniques for fetal procedures at our institution. METHODS: All patients undergoing minimally invasive fetal surgery for twin-to-twin transfusion syndrome or twin-reversed arterial perfusion sequence over a 6-year time period (2011-2016) were reviewed. Patients receiving monitored anesthesia care with local anesthesia were compared with those receiving spinal anesthesia in both selective fetoscopic laser photocoagulation and radiofrequency ablation fetal procedures. The primary outcome examined between the monitored anesthesia care and spinal anesthesia groups was the difference in conversion to general anesthesia using a noninferiority design with a noninferiority margin of 5%. Secondary outcome measures included use of vasopressors, procedure times, intraoperative fluids administered, maternal complications, and unexpected fetal demise within 24 hours of surgery. RESULTS: The difference in failure rate between monitored anesthesia care and spinal was -0.5% (95% CI, -4.8% to 3.7%). Patients receiving monitored anesthesia care plus local anesthesia were significantly less likely to need vasopressors, had a shorter presurgical operating room time, and received less fluid (P < .001). Operative time did not differ significantly. CONCLUSIONS: Monitored anesthesia care plus local anesthesia is a reliable and safe anesthetic choice for minimally invasive fetal surgery. Furthermore, it decreases maternal hemodynamic instability and reduces preincision operating room time.
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Anestesia Local/métodos , Anestesia Raquidea/métodos , Transfusión Feto-Fetal/cirugía , Fetoscopía/métodos , Procedimientos Quirúrgicos Mínimamente Invasivos/métodos , Monitoreo Intraoperatorio/métodos , Adulto , Anestesia Local/normas , Anestesia Raquidea/normas , Femenino , Transfusión Feto-Fetal/diagnóstico por imagen , Fetoscopía/normas , Humanos , Procedimientos Quirúrgicos Mínimamente Invasivos/normas , Monitoreo Intraoperatorio/normas , Embarazo , Ablación por Radiofrecuencia/métodos , Ablación por Radiofrecuencia/normas , Estudios RetrospectivosRESUMEN
BACKGROUND: The inhalation anesthetics are potent greenhouse gases. To reduce the global environmental impact of the health care sector, technologies are sought to limit the release of waste anesthetic gas into the atmosphere. METHODS: Using a photochemical exhaust gas destruction system, removal efficiencies for nitrous oxide, desflurane, and sevoflurane were measured at various inlet concentrations (25% and 50%; 1.5%, 3.0%, and 6.0%; and 0.5%, 1.0%, and 2.0%, respectively) with flow rates ranging from 0.25 to 2.0 L/min. To evaluate the economic competitiveness of the anesthetic waste gas destruction system, its price per ton of carbon dioxide equivalent was calculated and compared to other greenhouse gas abatement technologies and current market prices. RESULTS: All inhaled anesthetics evaluated demonstrate enhanced removal efficiencies with decreasing flow rates (P < .0001). Depending on the anesthetic and its concentration, the photochemical exhaust gas destruction system exhibits a constant first-order removal rate, k. However, there was not a simple relation between the removal rate k and the species concentration. The costs for removing a ton of carbon dioxide equivalents are <$0.005 for desflurane, <$0.114 for sevoflurane, and <$49 for nitrous oxide. CONCLUSIONS: Based on this prototype study, destroying sevoflurane and desflurane with this photochemical anesthetic waste gas destruction system design is efficient and cost-effective. This is likely also true for other halogenated inhalational anesthetics such as isoflurane. Due to differing chemistry of nitrous oxide, modifications of this prototype photochemical reactor system are necessary to improve its removal efficiency for this gas.
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Anestésicos por Inhalación/efectos adversos , Anestésicos por Inhalación/química , Gases de Efecto Invernadero/efectos adversos , Gases de Efecto Invernadero/química , Residuos Peligrosos/efectos adversos , Fotoquímica/métodos , Anestesia por Inhalación/efectos adversos , Anestésicos por Inhalación/análisis , Gases de Efecto Invernadero/análisis , Residuos Peligrosos/análisis , HumanosRESUMEN
INTRODUCTION: Open fetal repair of myelomeningocele (MMC) is an option for prenatally diagnosed spina bifida. Historically, high-dose volatile anesthetic was used for uterine relaxation but is associated with fetal cardiovascular depression. We examined the impact of administering a supplemental remifentanil infusion on the concentration of inhaled anesthetic required for intraoperative uterine relaxation. METHODS: We retrospectively analyzed 22 consecutive patients who underwent open fetal MMC repair with desflurane anesthesia from 2014 to 2018. The anesthetic protocol was modified to include high-dose opioid with remifentanil in 2016. We examined intraoperative end-tidal desflurane concentrations, vasopressor use, incidence of umbilical artery Doppler abnormalities, and incidence of preterm labor and delivery. RESULTS: Patients (n = 11) who received desflurane and remifentanil (Des/Remi) were compared to patients (n = 11) who received desflurane (Des) alone. Intraoperatively, the maximum end-tidal desflurane required to maintain uterine relaxation was lower in the Des/Remi group (7.9 ± 2.2% vs. 13.1 ± 1.2%, p < 0.001). The mean phenylephrine infusion rate was also lower in the Des/Remi group (36 ± 14 vs. 53 ± 10 mcg/min, p = 0.004). DISCUSSION: Use of opioid with supplemental remifentanil was associated with lower volatile anesthetic dosing and decreased vasopressor use; fetal outcomes were not different. Remifentanil may allow for less volatile anesthetic use while maintaining adequate uterine relaxation.
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Anestésicos por Inhalación , Meningomielocele , Feto , Humanos , Recién Nacido , Meningomielocele/diagnóstico por imagen , Meningomielocele/cirugía , Remifentanilo , Estudios RetrospectivosRESUMEN
BACKGROUND: Cerebral oximetry (cerebral oxygen saturation; ScO2) is used to noninvasively monitor cerebral oxygenation. ScO2 readings are based on the fraction of reduced and oxidized hemoglobin as an indirect estimate of brain tissue oxygenation and assume a static ratio of arterial to venous intracranial blood. Conditions that alter cerebral blood flow, such as acute changes in PaCO2, may decrease accuracy. We assessed the performance of two commercial cerebral oximeters across a range of oxygen concentrations during normocapnia and hypocapnia. METHODS: Casmed FORE-SIGHT Elite (CAS Medical Systems, Inc., USA) and Covidien INVOS 5100C (Covidien, USA) oximeter sensors were placed on 12 healthy volunteers. The fractional inspired oxygen tension was varied to achieve seven steady-state levels including hypoxic and hyperoxic PaO2 values. ScO2 and simultaneous arterial and jugular venous blood gas measurements were obtained with both normocapnia and hypocapnia. Oximeter bias was calculated as the difference between the ScO2 and reference saturation using manufacturer-specified weighting ratios from the arterial and venous samples. RESULTS: FORE-SIGHT Elite bias was greater during hypocapnia as compared with normocapnia (4 ± 9% vs. 0 ± 6%; P < 0.001). The INVOS 5100C bias was also lower during normocapnia (5 ± 15% vs. 3 ± 12%; P = 0.01). Hypocapnia resulted in a significant decrease in mixed venous oxygen saturation and mixed venous oxygen tension, as well as increased oxygen extraction across fractional inspired oxygen tension levels (P < 0.0001). Bias increased significantly with increasing oxygen extraction (P < 0.0001). CONCLUSIONS: Changes in PaCO2 affect cerebral oximeter accuracy, and increased bias occurs with hypocapnia. Decreased accuracy may represent an incorrect assumption of a static arterial-venous blood fraction. Understanding cerebral oximetry limitations is especially important in patients at risk for hypoxia-induced brain injury, where PaCO2 may be purposefully altered.
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Encéfalo/irrigación sanguínea , Encéfalo/metabolismo , Dióxido de Carbono/sangre , Circulación Cerebrovascular/fisiología , Oximetría/métodos , Oxígeno/sangre , Adulto , Femenino , Humanos , Masculino , Presión Parcial , Arteria Radial/metabolismo , Adulto JovenRESUMEN
Placenta accreta spectrum is becoming more common and is the most frequent indication for peripartum hysterectomy. Management of cesarean delivery in the setting of a morbidly adherent placenta has potential for massive hemorrhage, coagulopathies, and other morbidities. Anesthetic management of placenta accreta spectrum presents many challenges including optimizing surgical conditions, providing a safe and satisfying maternal delivery experience, preparing for massive hemorrhage and transfusion, preventing coagulopathies, and optimizing postoperative pain control. Balancing these challenging goals requires meticulous preparation with a thorough preoperative evaluation of the parturient and a well-coordinated multidisciplinary approach in order to optimize outcomes for the mother and fetus.
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Anestesia Epidural/métodos , Anestesia General/métodos , Anestesia Obstétrica/métodos , Anestesia Raquidea/métodos , Cesárea/métodos , Histerectomía/métodos , Placenta Accreta/cirugía , Femenino , Humanos , Dolor Postoperatorio/terapia , Planificación de Atención al Paciente , EmbarazoRESUMEN
INTRODUCTION: Umbilical artery (UA) Doppler ultrasound is used to assess uteroplacental insufficiency. Absent or reversed end diastolic flow (AREDF) in the UA is associated with increased perinatal mortality in fetuses with intrauterine growth restriction. We describe the incidence of UA Doppler abnormalities during open fetal surgery. METHODS: We conducted a retrospective review of patients undergoing open in utero myelomeningocele (MMC) repair between 2008 and 2015. Intermittent UA Dopplers were performed during key portions of all cases. Our primary outcome was the rate of any AREDF. Secondary outcomes included analysis of absent versus reversed end diastolic flow (EDF), vasopressor use, and volatile anesthetic and clinical outcomes. RESULTS: Thirty-four of 47 fetuses developed UA Doppler abnormalities intraoperatively. Nineteen had absent EDF and 15 had reversed EDF. No AREDF was present before induction, and all AREDF resolved by postoperative day 1. Ten of 19 (52.6%) patients who received sevoflurane had reversed EDF, versus 5/28 (17.9%) for desflurane, odds ratio (95% CI) 5.11 (1.36-19.16), p = 0.02. One intraoperative fetal death occurred in the AREDF group. DISCUSSION: AREDF is a common phenomenon during open MMC repair. Anesthetic agent choice may influence this risk. Future studies of UA flow during fetal surgery are needed to further evaluate the impact of intraoperative AREDF on fetal well-being.
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Feto/cirugía , Meningomielocele/cirugía , Insuficiencia Placentaria/epidemiología , Arterias Umbilicales/diagnóstico por imagen , Adulto , Velocidad del Flujo Sanguíneo , Femenino , Humanos , Incidencia , Complicaciones Intraoperatorias/diagnóstico por imagen , Complicaciones Intraoperatorias/epidemiología , Complicaciones Intraoperatorias/terapia , Insuficiencia Placentaria/diagnóstico por imagen , Insuficiencia Placentaria/terapia , Embarazo , Estudios Retrospectivos , Ultrasonografía DopplerRESUMEN
Although it is the most effective method to treat labor pain, neuraxial analgesia may be undesired, contraindicated, unsuccessful, or unavailable. Providing safe choices for labor pain relief is a central goal of health care providers alike. Consequently, knowledge of the efficacy, clinical implementation, and side effects of various non-neuraxial strategies is needed to provide appropriate options for laboring patients. In addition to nonpharmacologic alternatives, inhaled nitrous oxide and systemic opioids represent two broad classes of non-neuraxial pharmacologic labor analgesia most commonly available. This review summarizes the current published literature for these non-neuraxial labor analgesic options.
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Analgesia Obstétrica/métodos , Analgésicos Opioides/administración & dosificación , Analgésicos/administración & dosificación , Dolor de Parto/tratamiento farmacológico , Analgesia Epidural , Analgesia Obstétrica/efectos adversos , Analgésicos Opioides/efectos adversos , Femenino , Humanos , Trabajo de Parto , Manejo del Dolor/métodos , Embarazo , Resultado del TratamientoRESUMEN
BACKGROUND: The pupillary light reflex is a critical component of the neurologic examination, yet whether it is present, depressed, or absent is unknown in patients with significant opioid toxicity. Although opioids produce miosis by activating the pupillary sphincter muscle, these agents may induce significant hypercarbia and hypoxia, causing pupillary constriction to be overcome via sympathetic activation. The presence of either "pinpoint pupils" or sympathetically mediated pupillary dilation might prevent light reflex assessment. This study was designed to determine whether the light reflex remains quantifiable during opioid-induced hypercarbia and hypoxia. METHODS: Ten volunteers were administered remifentanil with a gradually increasing infusion rate and intermittent boluses, until the increasing respiratory depression produced an oxyhemoglobin saturation of 85% or less with associated hypercarbia. Subjects' heart rate, blood pressure, respiration, and transcutaneous carbon dioxide level were continuously recorded. Arterial blood gases and pupillary measures were taken before opioid administration, at maximal desaturation, and 15 min after recovery. RESULTS: The opioid-induced oxygen desaturation (≤ 85%) was associated with significant hypercarbia and evidence of sympathetic activation. During maximal hypoxia and hypercarbia, the pupil displayed parasympathetic dominance (2.5 ± 0.2 mm diameter) with a robust quantifiable light reflex. The reflex amplitude was linearly related to pupil diameter. CONCLUSIONS: Opioid administration with significant accompanying hypercarbia and hypoxia results in pupil diameters of 2 to 3 mm and a reduced but quantifiable pupillary light reflex. The authors conclude that the pupillary examination and evaluation of the light reflex remain useful for neurologic assessment during opioid toxicity.
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Analgésicos Opioides/farmacología , Pupila/efectos de los fármacos , Reflejo Pupilar/efectos de los fármacos , Adulto , Analgésicos Opioides/administración & dosificación , Sistema Nervioso Autónomo/efectos de los fármacos , Presión Sanguínea/efectos de los fármacos , Dióxido de Carbono/sangre , Relación Dosis-Respuesta a Droga , Femenino , Frecuencia Cardíaca/efectos de los fármacos , Humanos , Infusiones Intravenosas , Masculino , Oxígeno/sangre , Piperidinas/administración & dosificación , Piperidinas/farmacología , Remifentanilo , Insuficiencia Respiratoria/inducido químicamente , Insuficiencia Respiratoria/fisiopatologíaRESUMEN
We report the case of a term neonate who was somnolent at birth with ventilatory distress and experienced 2 seizures shortly after delivery. Laboratory tests revealed the neonate had a serum sodium of 113 mmol/L. The seizures stopped after treatment with midazolam, and the sodium was corrected slowly with 3% hypertonic saline without further sequelae. The severe neonatal hyponatremia and seizures were attributed to maternal consumption of excessive amounts of coconut water during labor. This case demonstrates the importance of careful consideration of both fluid volume and fluid electrolyte composition during labor to prevent adverse maternal and neonatal outcomes.
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Cocos , Hiponatremia , Convulsiones , Humanos , Recién Nacido , Femenino , Convulsiones/etiología , Hiponatremia/etiología , Embarazo , Adulto , Trabajo de PartoRESUMEN
Recently published results suggest that prenatal repair of fetal myelomeningocele is a potentially preferable alternative when compared to postnatal repair. In this article, the pathology of myelomeningocele, unique physiologic considerations, perioperative anesthetic management, and ethical considerations of open fetal surgery for prenatal myelomeningocele repair are discussed. Open fetal surgeries have many unique anesthetic issues such as inducing profound uterine relaxation, vigilance for maternal or fetal blood loss, fetal monitoring, and possible fetal resuscitation. Postoperative management, including the requirement for postoperative tocolysis and maternal analgesia, are also reviewed. The success of intrauterine myelomeningocele repair relies on a well-coordinated multidisciplinary approach. Fetal surgery is an important topic for anesthesiologists to understand, as the number of fetal procedures is likely to increase as new fetal treatment centers are opened across the United States.
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Anestesia/métodos , Terapias Fetales , Feto/cirugía , Meningomielocele/cirugía , Disrafia Espinal/cirugía , Adulto , Analgesia , Femenino , Terapias Fetales/ética , Feto/fisiología , Edad Gestacional , Humanos , Cuidados Intraoperatorios , Meningomielocele/diagnóstico por imagen , Cuidados Posoperatorios , Embarazo , Diagnóstico Prenatal , Cuidados Preoperatorios , Disrafia Espinal/diagnóstico por imagen , UltrasonografíaRESUMEN
BACKGROUND: Transcranial motor-evoked potentials (TcMEPs) monitor spinal cord motor tract integrity. Using a swine model, the authors studied the effects of vasodilatory hypotension, hemorrhage, and various resuscitation efforts on TcMEP responses. METHODS: Twelve pigs were anesthetized with constant infusions of propofol, ketamine, and fentanyl. Animals were incrementally hemorrhaged, until bilateral tibialis anterior TcMEP amplitude decreased to less than 40% of baseline or until 50% of the blood volume was removed. Mean arterial pressure (MAP), cardiac output (CO), and oxygen delivery (DO2) were examined. Resuscitation with phenylephrine, epinephrine, and colloid were evaluated. In seven animals, vasodilatory hypotension was examined. Paired comparisons and multivariate analysis were performed. RESULTS: Hemorrhage significantly reduced (as a percentage of baseline, mean±SD) TcMEPs (left, 33±29%; right, 26±21%), MAP (60±17%), CO (49±12%), and DO2 (43±13%), P value less than 0.001 for all. Vasodilation reduced MAP comparably, but TcMEPs, CO, and DO2, were not significantly lowered. After hemorrhage, restoration of MAP with phenylephrine did not improve TcMEPs, CO, or DO2, but similar restoration of MAP with epinephrine restored (to percentage of baseline) TcMEPs (59±40%), and significantly increased CO (81±17%) and DO2 (72±19%) compared with both hemorrhage and phenylephrine, P value less than 0.05 for all. Resuscitation with colloid did not improve TcMEPs. Multivariate analysis revealed that changes in TcMEPs were more closely associated with changes in CO and DO2 as compared with MAP. CONCLUSIONS: Hypotension from hemorrhage, but not vasodilation, is associated with a decrease in TcMEP amplitude. After hemorrhage, restoration of TcMEPs with epinephrine but not phenylephrine indicates that CO and DO2 affect TcMEPs more than MAP. Monitoring CO may be beneficial in major spine surgery when using TcMEP monitoring.
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Encéfalo/fisiología , Potenciales Evocados Motores/fisiología , Hemorragia/fisiopatología , Hipotensión/fisiopatología , Animales , Presión Sanguínea/fisiología , Gasto Cardíaco/fisiología , Estimulación Eléctrica , Femenino , Fluidoterapia , Hemodinámica/fisiología , Nitroprusiato/farmacología , Flujo Sanguíneo Regional/efectos de los fármacos , Flujo Sanguíneo Regional/fisiología , Resucitación , Porcinos , Vasoconstrictores/farmacología , Vasodilatación/fisiología , Vasodilatadores/farmacologíaAsunto(s)
Anestesiología/educación , Anestesiología/métodos , Anestesiología/normas , Profesionalismo , Anestesiología/ética , Comunicación , Curriculum , Humanos , Consentimiento Informado , Comunicación Interdisciplinaria , Atención Dirigida al Paciente , Atención Perioperativa/normas , Relaciones Profesional-Paciente , Estudiantes de Medicina , Enseñanza , Estados UnidosRESUMEN
BACKGROUND: Cerebral oximetry is a noninvasive optical technology that measures frontal cortex blood hemoglobin-oxygen saturation. Commercially available cerebral oximeters have not been evaluated independently. Unlike pulse oximeters, there are currently no Food and Drug Administration standards for performance or accuracy. We tested the hypothesis that cerebral oximeters accurately measure a fixed ratio of the oxygen saturation in cerebral mixed venous and arterial blood. METHODS: We evaluated the performance of 5 commercially available cerebral oximeters: the EQUANOX® 7600 in 3- and 4-wavelength versions (Nonin Medical, Plymouth, MN), FORE-SIGHT® (Casmed, Branford, CT), INVOS® 5100C (Covidien, Boulder, CO), and the NIRO-200NX® (Hamamatsu Photonics, Hamamatsu City, Japan) during stable isocapnic hypoxia in volunteers. Twenty-three healthy adults (14 men, 9 women) had sensors placed on each side of the forehead. The subject's inspired oxygen (FIO2) was then changed to produce 6 steady-state arterial oxygen saturation (SaO2) levels between 100% and 70%, while end-tidal CO2 was maintained constant. At each plateau, simultaneous blood samples from the jugular bulb and radial artery were analyzed with a hemoximeter (OSM-3, Radiometer Medical A/S, Copenhagen, Denmark). Each cerebral oximeter's bias was calculated as the difference between the instrument's reading (cerebral saturation, ScO2) with the weighted saturation of venous and arterial blood (Sa/vO2), as specified by each manufacturer (INVOS: 25% arterial/75% venous; FORE-SIGHT, EQUANOX, and NIRO: 30% arterial/70% venous). RESULTS: Five hundred forty-two comparisons between paired blood samples and oximeter readings were analyzed. The pooled root mean square error was 8.06%, a value higher than for pulse oximeters, which is ±3% by Food and Drug Administration standards. The mean % bias ± SD (precision) and root mean square errors were: FORE-SIGHT 1.76 ± 3.92 and 4.28; INVOS 0.05 ± 9.72 and 9.69; NIRO-200NX -1.13 ± 9.64 and 9.68; EQUANOX-3 λ 2.48 ± 8.12 and 8.47; EQUANOX-4 λ 2.84 ± 6.27 and 6.86. The FORE-SIGHT, NIRO-200NX, and EQUANOX-3 λ had significantly more positive bias at lower SaO2. The amount of bias during hypoxia was reduced when the bias was calculated on the basis of difference between oximeter reading and the arterial and mixed venous saturation difference rather than the weighted average of blood saturation, indicating that differences in the ratio between arterial and venous blood volumes account for some of the positive bias at low saturation. Dark skin pigment tended to produce more negative bias in all instruments but bias was significantly larger than zero only for the FORE-SIGHT oximeter. Bias was significantly more negative in women for INVOS and EQUANOX devices but not for the FORE-SIGHT device. CONCLUSIONS: While responsive to desaturation, cerebral oximeters exhibited large variation in reading errors between subjects, with mean bias possibly related to variations in the ratio of arterial and venous blood in the sampling area of the brain. This ratio is probably not fixed, as assumed by the manufacturers, but dynamically changes with hypoxia. Better understanding these factors could improve the performance of cerebral oximeters and help establish saturation or blood flow thresholds for brain well-being.
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Hipoxia/sangre , Oximetría/instrumentación , Oximetría/métodos , Adulto , Encéfalo/metabolismo , Femenino , Humanos , Hipoxia/diagnóstico , Masculino , Persona de Mediana Edad , Oximetría/normas , Consumo de Oxígeno , Factores Sexuales , Pigmentación de la Piel/fisiología , Adulto JovenRESUMEN
BACKGROUND: Carbon monoxide poisoning is a significant problem in most countries, and a reliable method of quick diagnosis would greatly improve patient care. Until the recent introduction of a multiwavelength "pulse CO-oximeter" (Masimo Rainbow SET(®) Radical-7), obtaining carboxyhemoglobin (COHb) levels in blood required blood sampling and laboratory analysis. In this study, we sought to determine whether hypoxemia, which can accompany carbon monoxide poisoning, interferes with the accurate detection of COHb. METHODS: Twelve healthy, nonsmoking, adult volunteers were fitted with 2 standard pulse-oximeter finger probes and 2 Rainbow probes for COHb detection. A radial arterial catheter was placed for blood sampling during 3 interventions: (1) increasing hypoxemia in incremental steps with arterial oxygen saturations (SaO2) of 100% to 80%; (2) normoxia with incremental increases in %COHb to 12%; and (3) elevated COHb combined with hypoxemia with SaO2 of 100% to 80%. Pulse-oximeter (SpCO) readings were compared with simultaneous arterial blood values at the various increments of hypoxemia and carboxyhemoglobinemia (≈25 samples per subject). Pulse CO-oximeter performance was analyzed by calculating the mean bias (SpCO - %COHb), standard deviation of the bias (precision), and the root-mean-square error (A(rms)). RESULTS: The Radical-7 accurately detected hypoxemia with both normal and elevated levels of COHb (bias mean ± SD: 0.44% ± 1.69% at %COHb <4%, and -0.29% ± 1.64% at %COHb ≥4%, P < 0.0001, and A(rms) 1.74% vs 1.67%). COHb was accurately detected during normoxia and moderate hypoxia (bias mean ± SD: -0.98 ± 2.6 at SaO2 ≥95%, and -0.7 ± 4.0 at SaO2 <95%, P = 0.60, and A(rms) 2.8% vs 4.0%), but when SaO2 decreased below approximately 85%, the pulse CO-oximeter always gave low signal quality errors and did not report SpCO values. CONCLUSIONS: In healthy volunteers, the Radical-7 pulse CO-oximeter accurately detects hypoxemia with both low and elevated COHb levels, and accurately detects COHb, but only reads SpCO when SaO2 is more than approximately 85%.
Asunto(s)
Carboxihemoglobina/metabolismo , Hipoxia/sangre , Oximetría/métodos , Oximetría/normas , Adolescente , Adulto , Intoxicación por Monóxido de Carbono/diagnóstico , Femenino , Humanos , Hipoxia/diagnóstico , Masculino , Persona de Mediana Edad , Adulto JovenRESUMEN
OBJECTIVES: Demonstration of the effectiveness for medical student teaching of the electroconvulsive therapy (ECT)-anesthesia exercise (ECTAE). The ECTAE is a self-directed, interdisciplinary (psychiatry and anesthesia) learning exercise. Students are taught the assessment of mood and cognition using structured interviewing methods (psychiatry), basic airway and pharmacologic management (anesthesia), and informed consent and interdisciplinary communication (both). There are online pre-exercise and postexercise assessments. METHODS: Third-year medical students reviewed educational reference materials, participated in ECT clinical encounters with both psychiatry and anesthesia, and debriefed after completion of the interdisciplinary exercise. The impact of the exercise was evaluated through online pre- and postexercise assessments. Quantitative and qualitative results for 3 student cohorts (2007 through 2010) were analyzed. RESULTS: Thirty-eight students participated the study over 3 years. Mean scores for 21 true-false questions increased from 14.3 to 17.5 (n = 30) with P < 0.0001. Similarly, mean scores for 11 multiple choice questions increased from 6.8 to 8.9 (n = 22) with P < 0.0001. Thirty of 31 students who completed the program evaluation reported greater comfort level discussing and recommending ECT after participation in ECTAE. CONCLUSIONS: The ECTAE is an effective learning activity for medical students, which incorporates cross-disciplinary learning objectives through self-directed exercises, online assessments, and actual clinical experience of ECT. It improves student knowledge of both psychiatry and anesthesia learning objectives, as well as increasing comfort about ECT. Further research could determine if this activity is easily transportable to other academic settings.