Torsten Birkholz

Incidence and predictors of difficult laryngoscopy in 11.219 pediatric anesthesia procedures

Objective:  Difficult laryngoscopy in pediatric patients undergoing anesthesia.

Guided bone regeneration: dynamic procedures versus static shielding in an animal model.

Due to its osteoinductive potential, the periosteum plays a crucial role in the process of neoosteogenesis. Therefore, periosteal elevation can lead to new bone formation in an artificially created space. In this study, we compared dynamic periosteal elevation with static shielding in an animal experiment. Different elevation/shielding heights of 5, 10, and 15 mm were tested with regard to various consolidation periods. Histological analysis, histomorphometry, and microradiography were used to measure the quantity and quality of the newly formed bone. No significant differences regarding bone quantity or quality were found between the two techniques. The cumulative results for the bone regeneration in the space created by distraction/elevation were about 66% in the dynamic and 67% in static procedure. The main advantages of both techniques are minimal invasion and low morbidity. In terms of clinical applications, periosteal elevation could be applied in cranio-maxillofacial surgery, in pre-implant augmentation and in reconstructive surgery.

Static and dynamic periosteal elevation: a pilot study in a pig model

The osteoinductive potential of periosteum and bone can be stimulated by elevating the periosteum in a distraction-like modus, but also by an ad-hoc elevation. This was tested and proved in an experiment in 9 Goettingen mini-pigs with elevation heights of 5, 10 and 15mm. Specially designed and perforated titanium meshes were implanted subperiosteally to compare the dynamic elevation procedure with static shielding. The cumulative results for bone formation underneath the mesh were 66% in dynamic and 67% in non-dynamic elevation. The cumulative results for mineralization of the bone regenerates in comparison with the underlying basal bone of the skull showed independently from the technique applied no difference bigger than 5%. No major difference in bone formation could be observed in this pilot study. The main advantages of dynamic periosteal elevation and static shielding are minimal invasion and morbidity. Periosteal elevation could be applied in cranio-maxillofacial surgery, in preimplantological augmentation and in reconstructive surgery of the skull; applications in other specialties may be possible.

Anesthetic management of patients with ornithine transcarbamylase deficiency

Ornithine transcarbamylase deficiency (OTCD) is the most common inborn error of the urea cycle. Several specific factors require care during anesthesia in patients with this condition to avoid metabolic decompensation with acute hyperammonemia and encephalopathy. We report monozygous twins with severe neonatal‐onset OTCD undergoing general anesthesia twice each, with midazolam, s‐ketamine, fentanyl and isoflurane in combination with surgical field infiltration with ropivacaine. Alternative pathway medication and high‐caloric diet with 10% glucose solutions were continuously administered during the perioperative course. Both children were extubated within 10 min of the final suture, and their neurological state remained unchanged. Perioperatively, blood ammonia levels remained within the normal range.

Immunohistochemical evaluation after ex vivo perfusion of rectus abdominis muscle flaps in a porcine model.

Background: The purpose of this study was to investigate whether and how the extracorporal perfusion of muscle flaps with a miniaturized perfusion system could change the expression of the proapoptotic protein caspase 3 and of the ischemia-sensitive protein hypoxia-inducible factor (HIF)-1&agr; as a first step toward the development of a clinically reliable tool for circumventing ischemia problems in free muscle flap transfer. Methods: In this study, 25 porcine rectus abdominis muscles were used and assigned to five different groups. In the baseline group (group I), the muscle flap remained in situ; in groups II and III, the muscle flap was harvested and remained ex vivo without or with subsequent single-shot heparinized flush; and in groups IV and V, the flaps were perfused with either heparinized autologous whole blood or crystalloid fluid (Jonosteril), using a miniaturized perfusion system without Exogen oxygenation. Muscle samples were taken for immunohistochemical evaluation. The proportion of positive cells for HIF-1&agr; and caspase 3 was compared for each group (groups II through V) to the baseline group (group I). Results: The expression of HIF-1&agr; and caspase 3 was increased in both groups without perfusion and was low during in vivo perfusion and extracorporal perfusion with crystalloid fluid. Heparinized autologous whole blood perfusion shows no protective effect, in contrast to the crystalloid fluid. Conclusions: The data of this study indicate that the extracorporal perfusion of muscle flaps with crystalloid fluid is a possible protective strategy against ischemia. Autologous heparinized whole blood seems to have no additional protective effect in a pure perfusion setting without oxygenation.

Online oxygen measurements in ex vivo perfused muscle tissue in a porcine model using dynamic quenching methods

IntroductionTransplantation of autologous free tissue flaps is the best applicable technique for treating large and complex tissue defects and still has one major failure criterion. Tissue—and in particular muscle tissue—is strongly sensitive to ischemia, thus after a critical period of oxygen depletion the risk of a partial or total flap loss is high.Materials and methodsFor that reason a miniaturized ex vivo perfusion system has been developed, that supplies the tissue during operational delays. The purpose of this study was to determine the oxygenation levels during such a perfusion using different perfusates and therefore to objectify if a complementary oxygenation unit is required to improve perfusion quality. The oxygen levels of the tissue, as well of the perfusate, were measured by using minimal invasive optical oxygen sensors that are based on dynamic quenching. The ex vivo perfused tissue was the porcine rectus abdominis muscle.ResultsResults show, that during perfusion with heparinized crystalloid fluid (Jonosteril®) and heparinized autologous whole blood, additional oxygenation of the perfusion reactor led to different ex vivo oxygen tissue saturations, which can be detected by dynamic quenching.ConclusionDynamic quenching methods are a promising and valuable technique to perform online oxygen measurements in ex vivo perfused muscle tissue in a porcine model.

Ischaemia-related cell damage in extracorporeal preserved tissue - new findings with a novel perfusion model.

Tissue undergoing free transfer in transplant or reconstructive surgery always is at high risk of ischaemia‐related cell damage. This study aims at assessing different procedures using an extracorporeal perfusion and oxygenation system to investigate the expression of hypoxia inducible factor (HIF)‐1‐α as marker for hypoxia and of the pro‐apoptotic protein Caspase‐3 in skeletal muscle to elucidate potential improvements in tissue conservation. Twenty‐four porcine rectus abdominis muscles were assigned to five different groups and examined after they had been extracorporeally preserved for 60 min. time. Group I was left untreated (control), group II was perfused with a cardioplegic solution, group III was flushed with 10 ml of a cardioplegic solution and then left untreated. Group IV and V were perfused and oxygenated with either an isotone crystalloid solution or a cardioplegic solution. Among others, immunohistochemistry (Caspase‐3 and HIF‐1‐α) of muscle samples was performed. Furthermore, oxygen partial pressure in the perfusate at the arterial and venous branch was measured. Expression of Caspase‐3 after 60 min. was reduced in all groups compared to the control group. Furthermore, all groups (except group III) expressed less HIF‐1‐α than the control group. Oxygenation leads to higher oxygen levels at the venous branch compared to groups without oxygenation. Using an extracorporeal perfusion and oxygenation system cell damage could be reduced as indicated by stabilized expressions of Caspase‐3 and HIF‐1‐α for 60 min. of tissue preservation. Complete depletion of oxygen at the venous branch can be prevented by oxygenation of the perfusate with ambient air.

Incidence and predictors of poor laryngoscopic view in children undergoing pediatric cardiac surgery.

OBJECTIVE Previous investigations reported a higher incidence of poor laryngoscopic views in pediatric patients undergoing cardiac surgery. The objective of this study was to analyze why children undergoing cardiac surgery have such an increased incidence of poor laryngoscopic views during anesthesia induction. DESIGN This study was designed as a retrospective analysis. SETTING This analysis was based on a single-center cohort of a university hospital. PARTICIPANTS One thousand one hundred seventy-seven general anesthesia procedures, including a direct laryngoscopic view over a period of 6 consecutive years, in pediatric patients undergoing cardiac surgery. INTERVENTIONS Because of the retrospective character of this study, there were no study-related interventions. MEASUREMENTS AND MAIN RESULTS Poor laryngoscopic views were defined as Cormack and Lehane (CML) grade III and IV. The overall incidence of poor laryngoscopic views was 3.5%. In patients younger than 1 year of age, the incidence of CML III or IV was significantly higher than in the older patients (5.6% v 1.7%). None of the patients with CML III/IV findings had Down syndrome; whereas in 9 of 41 patients with CML grade III/IV, a concomitant congenital syndrome like DiGeorge syndrome or CHARGE syndrome was found. CONCLUSIONS The general incidence of CML III/IV findings during the induction of anesthesia for pediatric cardiac surgery is more than twice as high as reported in unselected pediatric cohorts. In patients below 1 year of age and in male patients, difficult laryngoscopy is more frequent. Concomitant Down syndrome was not associated with difficult laryngoscopy.

Assessing viability of extracorporeal preserved muscle transplants using external field stimulation: a novel tool to improve methods prolonging bridge-to-transplantation time

Preventing ischemia-related cell damage is a priority when preserving tissue for transplantation. Perfusion protocols have been established for a variety of applications and proven to be superior to procedures used in clinical routine. Extracorporeal perfusion of muscle tissue though cumbersome is highly desirable since it is highly susceptible to ischemia-related damage. To show the efficacy of different perfusion protocols external field stimulation can be used to immediately visualize improvement or deterioration of the tissue during active and running perfusion protocols. This method has been used to show the superiority of extracorporeal perfusion using porcine rectus abdominis muscles perfused with heparinized saline solution. Perfused muscles showed statistically significant higher ability to exert force compared to nonperfused ones. These findings can be confirmed using Annexin V as marker for cell damage, perfusion of muscle tissue limits damage significantly compared to nonperfused tissue. The combination of extracorporeal perfusion and external field stimulation may improve organ conservation research.

Evaluation of a novel algorithm for primary mass casualty triage by paramedics in a physician manned EMS system: a dummy based trial

BackgroundThe Amberg-Schwandorf Algorithm for Primary Triage (ASAV) is a novel primary triage concept specifically for physician manned emergency medical services (EMS) systems. In this study, we determined the diagnostic reliability and the time requirements of ASAV triage.MethodsSeven hundred eighty triage runs performed by 76 trained EMS providers of varying professional qualification were included into the study. Patients were simulated using human dummies with written vital signs sheets. Triage results were compared to a standard solution, which was developed in a modified Delphi procedure. Test performance parameters (e.g. sensitivity, specificity, likelihood ratios (LR), under-triage, and over-triage) were calculated. Time measurements comprised the complete triage and tagging process and included the time span for walking to the subsequent patient. Results were compared to those published for mSTaRT. Additionally, a subgroup analysis was performed for employment status (career/volunteer), team qualification, and previous triage training.ResultsFor red patients, ASAV sensitivity was 87%, specificity 91%, positive LR 9.7, negative LR 0.139, over-triage 6%, and under-triage 10%. There were no significant differences related to mSTaRT. Per patient, ASAV triage required a mean of 35.4 sec (75th percentile 46 sec, 90th percentile 58 sec). Volunteers needed slightly more time to perform triage than EMS professionals. Previous mSTaRT training of the provider reduced under-triage significantly. There were significant differences in time requirements for triage depending on the expected triage category.ConclusionsThe ASAV is a specific concept for primary triage in physician governed EMS systems. It may detect red patients reliably. The test performance criteria are comparable to that of mSTaRT, whereas ASAV triage might be accomplished slightly faster. From the data, there was no evidence for a clinically significant reliability difference between typical staffing of mobile intensive care units, patient transport ambulances, or disaster response volunteers. Up to now, there is no clinical validation of either triage concept. Therefore, reality based evaluation studies are needed.German AbstractHintergrundDer Amberg-Schwandorf-Algorithmus für die Vorsichtung (ASAV) ist ein neues Ablaufschema für die Vorsichtung durch Nicht-Ärzte beim Massenanfall von Verletzten und speziell für notarztbasierte Rettungsdienstsysteme entwickelt. In der vorliegenden Arbeit untersuchten wir die Testgütekriterien und den Zeitbedarf für die Vorsichtung mittels ASAV.Methodenfür die Studie wurden 780 Sichtungsvorgänge von 76 Probanden unterschiedlicher Qualifikation ausgewertet. Als Patienten wurden Dummies, ausgestattet mit einer schriftlichen Zustandsbeschreibung verwendet. Die Sichtungsergebnisse wurden mit einer Musterlösung verglichen, welche in einem modifizierten Delphi-Prozess erstellt wurden. Daraus wurden Testgütekriterien wie Sensitivität, Spezifität, Wahrscheinlichkeitsverhältnisse (LR), Über- und Untertriage berechnet. Die Zeitmessung umfasste den kompletten Sichtungs- und Sichtungskennzeichnungsvorgang einschließlich der Wegezeit zum nächsten Patienten. Die Ergebnisse wurden zu den für mSTaRT veröffentlichten Daten verglichen. Zusätzlich wurde eine vordefinierte Subgruppenanalyse in Bezug auf Beschäftigungsverhältnis (Haupt- vs. Ehrenamt), Teamzusammensetzung und vorherige Sichtungsausbildung durchgeführt.ErgebnisseBezogen auf die roten Patienten betrug die Sensitivität 87%, die Spezifität 91%, die positive LR 9,7, die negative LR 0,139, die Übertriage 6% und die Untertriage 10%. Signifikante Unterschiede zu mSTaRT konnten nicht nachgewiesen werden. Die Sichtung mittels ASAV benötigte durchschnittlich 35,4 Sek. pro Patient (75. Perzentil 46 Sek., 90. Perzentil 58 Sek.). Ehrenamtliche benötigten geringfügig länger für die Vorsichtung. Eine vorausgehende Ausbildung in einem anderen Sichtungskonzept reduzierte die Untertriage signifikant. Je nach erwarteter Sichtungskategorie unterschied sich der Zeitbedarf für die Vorsichtung signifikant.SchlussfolgerungenDer ASAV ist ein Konzept für die Vorsichtung speziell für notarztbasierte Rettungsdienstsysteme. Durch ASAV scheinen sich die roten Patienten verlässlich identifizieren zu lassen. Die Testgütekriterien sind vergleichbar mit den für mSTaRT publizierten Werten, wobei ASAV etwas weniger Zeit in Anspruch zu nehmen scheint. Unsere Daten ergaben keinen signifikanten Unterschied bei der Vorsichtungs-Reliabilität zwischen typischen Besatzungen von Rettungstransportwägen, Krankentransportwägen oder ehrenamtlichen Katastrophenschutzeinheiten. Gegenwärtig ist kein Vorsichtungsalgorithmus klinisch validiert. Daher sind weitere Untersuchungen an Realeinsätzen notwendig.