Kelly W. Smith

The risk and outcomes of epidural hematomas after perioperative and obstetric epidural catheterization: a report from the Multicenter Perioperative Outcomes Group Research Consortium.

BACKGROUND:In this study, we sought to determine the frequency and outcomes of epidural hematomas after epidural catheterization. METHODS:Eleven centers participating in the Multicenter Perioperative Outcomes Group used electronic anesthesia information systems and quality assurance databases to identify patients who had epidural catheters inserted for either obstetrical or surgical indications. From this cohort, patients undergoing laminectomy for the evacuation of hematoma within 6 weeks of epidural placement were identified. RESULTS:Seven of 62,450 patients undergoing perioperative epidural catheterizations developed hematoma requiring surgical evacuation. The event rate was 11.2 × 10−5 (95% confidence interval [CI], 4.5 × 10−5 to 23.1 × 10−5). Four of the 7 had anticoagulation/antiplatelet therapy that deviated from American Society of Regional Anesthesia guidelines. None of 79,837 obstetric patients with epidural catheterizations developed hematoma (upper limit of the 95% CI, 4.6 × 10−5). The hematoma rate in obstetric epidural catheterizations was significantly lower than in perioperative epidural catheterizations (P = 0.003). CONCLUSIONS:In this series, the 95% CI for the frequency of epidural hematoma requiring laminectomy after epidural catheter placement for perioperative anesthesia/analgesia was 1 event per 22,189 placements to 1 event per 4330 placements. Risk was significantly lower in obstetric epidurals.

Antidepressant and Neurocognitive Effects of Isoflurane Anesthesia versus Electroconvulsive Therapy in Refractory Depression

Background Many patients have serious depression that is nonresponsive to medications, but refuse electroconvulsive therapy (ECT). Early research suggested that isoflurane anesthesia may be an effective alternative to ECT. Subsequent studies altered drug, dose or number of treatments, and failed to replicate this success, halting research on isofluranes antidepressant effects for a decade. Our aim was to re-examine whether isoflurane has antidepressant effects comparable to ECT, with less adverse effects on cognition. Method Patients with medication-refractory depression received an average of 10 treatments of bifrontal ECT (n = 20) or isoflurane (n = 8) over 3 weeks. Depression severity (Hamilton Rating Scale for Depression-24) and neurocognitive responses (anterograde and retrograde memory, processing speed and verbal fluency) were assessed at Pretreatment, Post all treatments and 4-week Follow-up. Results Both treatments produced significant reductions in depression scores at Post-treatment and 4-week Follow-up; however, ECT had modestly better antidepressant effect at follow-up in severity-matched patients. Immediately Post-treatment, ECT (but not isoflurane) patients showed declines in memory, fluency, and processing speed. At Follow-up, only autobiographical memory remained below Pretreatment level for ECT patients, but isoflurane patients had greater test-retest neurocognitive score improvement. Conclusions Our data reconfirm that isoflurane has an antidepressant effect approaching ECT with less adverse neurocognitive effects, and reinforce the need for a larger clinical trial.

Monitoring body-core temperature from the trachea : Comparison between pulmonary artery, tympanic, esophageal, and rectal temperatures

Introduction. We designed an endotracheal tube (ETT) for acquiring body-tore temperature from the trachea. This ETT had two temperature sensors, one attached to the inside surface of the cuff, the other mounted on the ETT shaft underneath the cuff. The ETT was evaluatedin vitro and in dogs to determine: 1) optimal position of temperature sensors and 2) the responsiveness, accuracy, and resistance to ventilatory artifacts.Methods.In vitro. An artificial trachea assessed the response-time and accuracy of ETT temperature sensors to abrupt temperature changes and ventilatory flow-rates.In vivo. Body temperature in 5 dogs was lowered to approximately 26°C then elevated toward 39°C using a heat exchanger during carotid jugular bypass. ETT temperature measurements were compared simultaneously with those from the artificial trachea (in vitro) or from the pulmonary artery, tympanic cavity, esophagus, and rectum of dogs using dry and humidified gas.Results. Cuff temperature sensor responded quickly and accurately to temperature changes and was less prone than the tube sensor to ventilatory and humidity artifacts. During carotid-jugular bypass,in vivo tube and cuff mean temperatures averaged 1.4°C and 0.36°C lower, respectively, than pulmonary artery temperatures. There were no statistical differentes (P > 0.05) between cuff temperatures and those measured from the pulmonary artery, tympanic cavity, esophagus, and rectum. Heating and humidifying the inspiratory gas of dogs with a water-bath humidifer or heat moisture exchanger (HME) had minimal effects on the cuff temperature sensor. An in-line HME increasedin vivo tube temperature from baseline values by 1.13 ± 0.80 °C, while cuff temperature increased by 0.21 ±0.24°C.Conclusion. The cuff of the ETT is a reliable site for measuring body-tore temperature in intubated patients.

Comparison of tidal ventilation and high-frequency jet ventilation before and after cardiopulmonary bypass in dogs using two-dimensional transesophageal echocardiography

This study compared the use of high-frequency jet ventilation (HFJV) and tidal ventilation (TV) in a group of dogs with induced global myocardial ischemia before and after cardiopulmonary bypass. Transesophageal echocardiography was used to determine whether HFJV with its lower airway pressures could improve cardiac performance. The surgical procedure was separated into four study periods: closed chest before bypass, open chest before bypass, open chest after bypass, and closed chest after bypass. During each of these study periods, the dogs were randomly ventilated with alternate periods of TV and HFJV to maintain the PaCO2 at 34.3 +/- 3.3 mm Hg (mean +/- SEM). Cardiac output, stroke volume, systemic mean blood pressure, left ventricular ejection fraction, left ventricular end-diastolic volume, left ventricular dP/dt, left ventricular stroke work, and expiratory volumetric flows were higher during HFJV, whereas airway pressures and pulmonary vascular resistance were lower. Increases in cardiac output and stroke volume during HFJV were due to a combination of improved left ventricular contractility indicated by increased LV dP/dt and increased left ventricular end-diastolic volume accompanying decreased airway pressures. These data indicate that HFJV with its lower airway pressure is associated with significantly less impairment of cardiovascular function than TV in dogs with induced global myocardial ischemia.

Monitoring normal and aberrant electrocardiographic activity from an endotracheal tube: Comparison of the surface, esophageal, and tracheal electrocardiograms

Introduction. We designed an endotracheal (ET) tube with orthogonally spaced ECG cuff electrodes. This ET tube was evaluated in dogs and sheep to determine (1) whether ECGs recorded from our tube were sufficient to make accurate clinical decisions concerning heart rate and rhythm; and (2) whether metallic cuff electrodes in direct contact with the trachea could induce mucosal burn injury during episodes of defibrillation.Methods. Using experimental animals, we obtained ECGs from their tracheae and compared our findings with ECGs obtained from surface and esophageal electrodes. The electrical activity of the heart was modified by increasing the depth of anesthesia, occluding the left coronary artery, and administering beta-adrenergic drugs. Before the dogs were euthanized, they were subjected to episodes of transthoracic and intrathoracic defibrillation at energy levels of 200 to 400 J. A postmortem pathological examination of the trachea was performed to determine the incidence of mucosal burn injury.Results. Tracheal electrocardiography provided valid information on heart-rate monitoring and certain morphology profiles. The R-R, PR, QRS, and QT intervals measured from the trachea had a correlation of 1.0, 0.96, 0.83, and 0.98, respectively, when compared with the same intervals obtained from surface electrodes. Two tracheae subjected to intrathoracic defibrillation at >300 J revealed evidence of minor burn injury. Some localized epithelium loss was displayed in all tracheae; we attributed this to tracheal intubation.Conclusion. Tracheal electrocardiography may be useful in trauma patients who require intubation where injury precludes placement of chest ECG electrodes.AbstraktZiel. Wir entwarfen einen Endotrachealtubus (ET) mit rechtwinklig angeordneten EKG-Cuffelektroden. Dieser ET wurde bei Hunden und Schafen getestet, um zu bestimmen, Ob 1) die von unserem Tubus aufgenommenen EKG-Daten ausreichten, um exakte klinische Entscheidungen beziiglich Herzfrequenz und Rhythmus treffen zu konnen; 2) wahrend der Defibrillation metallische Cuffelektroden in direktem Kontakt mit der Trachea Verbrennungsschaden der Schleimhaut verursachen konnten.Methoden. Bei unseren Versuchstieren leiteten wir die EKGs von der Trachea ab und verglichen unsere Ergebnisse mit EKGs, die mit Oberflächen-und Ösophaguselektroden abgeleitet wurden. Wir modifizierten die elektrische Aktivitat des Herzens durch Narkosevertiefung, Verschluβ der linken Koronararterie und Gabe von etasympathomimetika. Vor ihrer Totung wurden die Hunde transthorakal und intrathorakal mit Energien von 200 bis 400 Joule defibrilliert. Postmortal untersuchten wir die Trachea histologisch, um die Inzidenz von Verbrennungsschaden der Schleimhaut zu bestimmen.Ergebnisse. Die tracheale Elektrokardiographie lieferte valide Informationen iiber die Herzfrequenz und gewisse morphologische Profile. Die RR-, PR-, QRS- und QT-Intervalle der Trachealableitung korrelierten mit den entsprechenden Intervallen der Oberflächenableitungen mit Koeffizienten von 1.0, 0.96, 0.83 und 0.98. Die Tracheae zweier Versuchstiere, die intrathorakaler Defibrillation mit >300 Joule unterworfen worden waren, zeigten geringe Verbrennungsschaden. Ortlich begrenzter Verlust von Trachealepithel trat in alien Tracheae auf; wir schrieben dies der Intubation zu.SchluBfolgerung. Die tracheale Elektrokardiographie konnte bei intubationspflichtigen Unfallpatienten, deren Verletzungen die Anlage von Brustelektroden ausschlieβen, nützlich sein.ResumenObjetivo. Disenamos un tubo endotraqueal (ET) con electrodos de ECG en manguito espaciados ortogonalmente. Este tubo ET fue evaluado en perros y ovejas para determinar (1) si los ECG obtenidos desde nuestro tubo eran suficientes para efectuar decisiones clinicas en relacion a la frecuencia y ritmo cardiacos; y (2) si los electrodos metalicos en manguito en contacto directo con la tràquea pudiesen inducir quemaduras de la mucosa durante episodios de defibrilacion.Mètodos. Usando animales experimentales, obtuvimos ECG a partir de sus tràqueas y los comparamos con ECG obtenidos desde electrodos de superficie y desde electrodos esofagicos. La actividad elèctrica cardiaca fue modificada cambiando la profundidad de la anestesia, ocluyendo la arteria coronaria izquierda, y administrando drogas betaadrenèrgicas. Antes de sacrificar los perros, ellos fueron objeto de episodios de defibrilacion transtroràcica e intratoracica con niveles de energia entre 200 y 400 joules. Se realizò examen patològico de la tràquea para determinar la incidencia de quemadura de la mucosa.Resultados. La electrocardiografia traqueal proporcionò informatiòn vàlida en relaciòn a monitorizaciòn de frecuencia cardiaca y algunos perfiles morfo`ogicos. Los intervalos R-R, PR, QRS, y QT medidos en la tràquea tuvieron correlaciones de 1.0, 0.96, 0.83, y 0.98, respectivamente, al ser comparados con los mismos intervalos medidos con electrodos de superficie. Dos traqueas sometidas a defibrilacion intratoracica con energia de 300 joules revelaron evidencia de quemaduras menores. Algun grado de `erdida localizada de epitelio fue observado en todas las traqueas; nosotros atribuimos esto a la intubatiòn traqueal.Conclusion. La electrocardiografia traqueal puede ser ùtil en pacientes traumatizados que requieran intubatiòn en quienes, debido a la injuria, sea poco factible la colocacion de electrodos de ECG en el tòrax.