Thomas Edrich

Three Patients with Full Facial Transplantation

Unlike conventional reconstruction, facial transplantation seeks to correct severe deformities in a single operation. We report on three patients who received full-face transplants at our institution in 2011 in operations that aimed for functional restoration by coaptation of all main available motor and sensory nerves. We enumerate the technical challenges and postoperative complications and their management, including single episodes of acute rejection in two patients. At 6 months of follow-up, all facial allografts were surviving, facial appearance and function were improved, and glucocorticoids were successfully withdrawn in all patients.

Cardiac output monitoring using indicator-dilution techniques: basics, limits, and perspectives.

The ability to monitor cardiac output is one of the important cornerstones of hemodynamic assessment for managing critically ill patients at increased risk for developing cardiac complications, and in particular in patients with preexisting cardiovascular comorbidities. For >30 years, single-bolus thermodilution measurement through a pulmonary artery catheter for assessment of cardiac output has been widely accepted as the “clinical standard” for advanced hemodynamic monitoring. In this article, we review this clinical standard, along with current alternatives also based on the indicator-dilution technique, such as the transcardiopulmonary thermodilution and lithium dilution techniques. In this review, not only the underlying technical principles and the unique features but also the limitations of each application of indicator dilution are outlined.

Can the blood content of the tissues be determined optically during pulse oximetry without knowledge of the oxygen saturation? -an in-vitro investigation

Current pulse oximeters become unreliable at low oxygen saturations because the influence of physiological artifacts that are not measured independently such as the blood content of the tissues increases considerably. The authors demonstrate that the blood content of simulated tissues in an in-vitro model may be determined and monitored continuously during pulse oximetry by considering the absolute absorption of red and infrared light.

Pulse oximetry: an improved in vitro model that reduces blood flow-related artifacts

Artifacts may occur in many in vitro models of pulse oximetry due to the optical effects of synchronously oriented and/or deformed erythrocytes. Although these artifacts are most likely negligible in living superficial tissues, they are demonstrated to have considerable influence on the calibration curve obtainable from the in vitro simulation of pulse oximetry in such models, especially at low oxygen saturations. Therefore, the authors have developed a modified in vitro model which reduces the effect of these artifacts. This is achieved by excluding data obtained during pressure transients and by raising the blood flow velocity. As a result, the model more closely approximates in vivo pulse oximetry, particularly under clinically important conditions of low blood oxygen saturation levels.

Ketamine for long-term sedation and analgesia of a burn patient

We present a case in which ketamine was used for long-term sedation and analgesia of a burn patient. Under escalating opiate dosages, the patient had developed persistent ileus as well as abdominal distension that caused respiratory compromise, without receiving sufficient analgesia. The opiate-sparing effect of the continuous ketamine infusion was more than 90%. The ileus resolved within 24 h. The quality of sedation also changed favorably. There were no obvious adverse effects of ketamine.

Time-Dependent Block and Resurgent Tail Currents Induced by Mouse β4154–167 Peptide in Cardiac Na+ Channels

Resurgent tail Na+ currents were first discovered in cerebellar Purkinje neurons. A recent study showed that a 14-mer fragment of a mouse β4 subunit, β4154–167, acts as an intracellular open-channel blocker and elicits resurgent currents in Purkinje neurons (Grieco, T.M., J.D. Malhotra, C. Chen, L.L. Isom, and I.M. Raman. 2005. Neuron. 45:233–244). To explore these phenotypes in vitro, we characterized β4154–167 actions in inactivation-deficient cardiac hNav1.5 Na+ channels expressed in human embryonic kidney 293t cells. Intracellular β4154–167 from 25–250 μM elicited a conspicuous time-dependent block of inactivation-deficient Na+ currents at 50 mV in a concentration-dependent manner. On and off rates for β4154–167 binding were estimated at 10.1 μM−1s−1 and 49.1 s−1, respectively. Upon repolarization, large tail currents emerged with a slight delay at −140 mV, probably as a result of the rapid unblocking of β4154–167. Near the activation threshold (approximately −70 mV), resurgent tail currents were robust and long lasting. Likewise, β4154–167 induces resurgent currents in wild-type hNav1.5 Na+ channels, although to a lesser extent. The inactivation peptide acetyl-KIFMK-amide not only restored the fast inactivation phenotype in hNav1.5 inactivation-deficient Na+ channels but also elicited robust resurgent currents. When modified by batrachotoxin (BTX), wild-type hNav1.5 Na+ channels opened persistently but became resistant to β4154–167 and acetyl-KIFMK-amide block. Finally, a lysine substitution of a phenylalanine residue at D4S6, F1760, which forms a part of receptors for local anesthetics and BTX, rendered cardiac Na+ channels resistant to β4154–167. Together, our in vitro studies identify a putative S6-binding site for β4154–167 within the inner cavity of hNav1.5 Na+ channels. Such an S6 receptor readily explains (1) why β4154–167 gains access to its receptor as an open-channel blocker, (2), why bound β4154–167 briefly prevents the activation gate from closing by a “foot-in-the-door” mechanism during deactivation, (3) why BTX inhibits β4154–167 binding by physical exclusion, and (4) why a lysine substitution of residue F1760 eliminates β4154–167 binding.

Usefulness of intraoperative epiaortic echocardiography to resolve discrepancy between transthoracic and transesophageal measurements of aortic valve gradient — a case report

PurposeIntraoperative measurement of the aortic valve (AV) gradient in patients undergoing cardiac surgery is routinely performed using transesophageal echocardiography (TEE). In patients with severe aortic stenosis (AS), TEE Doppler beam alignment with the blood flow through the stenotic valve may be inaccurate, resulting in an underestimation of the AV gradient. We describe here the use of epiaortic echocardiography as an alternative to TEE for the intraoperative evaluation of AS.Clinical featuresA patient diagnosed with severe AS (peak pressure gradient by transthoracic echocardiography: 108 mmHg) was undergoing AV replacement. In contrast, intraoperative TEE examination performed prior to bypass showed only a mild pressure gradient across the AV (peak pressure gradient: 38 mmHg). In order to resolve the conflicting information, epiaortic echocardiography was used to measure the AV gradient, confirming severe AS (peak pressure gradient: 98 mmHg). Most likely, Doppler beam alignment through the stenotic valve was more parallel to blood flow using epiaortic echocardiography, thus revealing the true pressure gradient.ConclusionIntraoperative epiaortic measurement of AV gradients can be successfully performed in patients where TEE may be inaccurate due to difficulty in aligning a Doppler beam with the transvalvular blood flow.ZusammenfassungObjectifLa mesure peropératoire du gradient vaivuiaire aortique (VA) chez des patients qui subissent une intervention chirurgicaie cardiaque est habitueiiement réaiisée par échocardiographie transœsophagienne (ETO). Dans les cas de sténose aortique (SA) sévère, l’alignement du faisceau d’ETO Doppier avec le débit sanguin traversant la vaivuie sténosée peut être imprécis, ce qui peut entraîner une sousestimation du gradient VA. L’utiiisation de l’échocardiographie épiaortique est décrite, en remplacement de l’ETO dans lévaiuation peropératoire de la SA.Éléments cliniquesUn patient souffrant d’une SA sévère (gradient de pression de pointe maximaie par l’échocardiographie transthoracique: 108 mmHg) devait subir ie rempiacement d’une VA. Néanmoins, l’ETO peropératoire réaiisée avant la greffe a montré seulement un léger gradient de pression de part et d’autre de ia VA (gradient de pression de pointe maximaie: 38 mmHg). Pour éliminer les informations contradictoires, nous avons mesuré le gradient VA par échocardiographie épiaortique, ce qui a confirmé une sévère SA (gradient de pression de pointe maximaie: 98 mmHg). L’alignement du faisceau Doppier avec ia valve sténosée était, vraisemblablement, davantage parallèle au débit sanguin à l’échocardiographie épiaortique, révélant ainsi le gradient de pression réel.ConclusionLa mesure épiaortique peropératoire des gradients VA peut être réussie dans les cas où l’ETO est imprécise à cause de difficuité d’alignement du faisceau Doppier avec le débit sanguin transvalvulaire.

Ephedrine blocks rat sciatic nerve in vivo and sodium channels in vitro

Background:The sympathomimetic drug ephedrine has been used intrathecally as the sole local anesthetic for labor and delivery. Because ephedrine may be a useful adjuvant to local anesthetics, the authors investigated the local anesthetic properties of ephedrine in a rat sciatic nerve block model and the underlying mechanism in cultured cells stably expressing Na+ channels. Methods:After approval of the animal protocol, the sciatic nerves of anesthetized rats were exposed by lateral incision of the thighs, 0.2 ml ephedrine at 0.25, 1, 2.5, or 5% and/or bupivacaine at 0.125% was injected, and the wound was closed. Motor and sensory/nociceptive functions were evaluated by the force achieved by pushing against a balance and the reaction to pinch, respectively. The whole cell configuration of the patch clamp technique was used to record Na+ currents from human embryonal kidney cells stably transfected with Nav1.4 channels. Results:The nociception blockade was significantly longer than the motor blockade at test doses of 2.5 and 5% of ephedrine, or when 1% ephedrine was combined with 0.125% bupivacaine (analysis of variance with repeated measures, P < 0.001, n = 8/group). In vitro, the 50% inhibitory concentrations of ephedrine at −150 and −60 mV were 1,043 ± 70 and 473 ± 13 &mgr;m, respectively. High-frequency stimulation revealed a use-dependent block of 18%, similar to most local anesthetics. Conclusions:Because ephedrine’s properties are at least partly due to Na+ channel blockade, detailed histopathologic investigations are justified to determine the potential of ephedrine as an adjuvant to clinically used local anesthetics.

Providing Initial Transthoracic Echocardiography Training for Anesthesiologists: Simulator Training Is Not Inferior to Live Training

OBJECTIVE Transthoracic echocardiography (TTE) is finding increased use in anesthesia and critical care. Efficient options for training anesthesiologists should be explored. Simulator mannequins allow for training of manual acquisition and image recognition skills and may be suitable due to ease of scheduling. The authors tested the hypothesis that training with a simulator would not be inferior to training using a live volunteer. DESIGN Prospective, randomized trial. SETTING University hospital. PARTICIPANTS Forty-six anesthesia residents, fellows, and faculty. INTERVENTIONS After preparation with a written and video tutorial, study subjects received 80 minutes of TTE training using either a simulator or live volunteer. Practical and written tests were completed before and after training to assess improvement in manual image acquisition skills and theoretic knowledge. The written test was repeated 4 weeks later. MEASUREMENTS AND MAIN RESULTS Performance in the practical image-acquisition test improved significantly after training using both the live volunteer and the simulator, improving by 4.0 and 4.3 points out of 15, respectively. Simulator training was found not to be inferior to live training, with a mean difference of -0.30 points and 95% confidence intervals that did not cross the predefined non-inferiority margin. Performance in the written retention test also improved significantly immediately after training for both groups but declined similarly upon repeat testing 4 weeks later. CONCLUSIONS When providing initial TTE training to anesthesiologists, training using a simulator was not inferior to using live volunteers.

State-dependent block of human cardiac hNav1.5 sodium channels by propafenone.

State-dependent blockade of human cardiac hNav1.5 sodium channels by propafenone was studied using whole-cell patch clamp techniques. Both a direct investigation using cells with inactivation-deficient sodium channels and an algorithmic approach used on cells with wild-type channels revealed a rapid binding of propafenone to the open state. This occurs approximately 4000 and 700 times faster than the binding to the resting and inactivated state, respectively. An established mathematical “gating” model was modified to represent the experimental data.