Effect of prior administration of succinylcholine on duration of action of vecuronium during enflurane anaesthesia

The effects of succinylcholine, which was given to facilitate tracheal intubation on the duration of action of subsequently administered vecuronium bromide, were evaluated in 54 adult patients who underwent abdominal surgeries under enflurane anaesthesia. The electromyographic response to train–of–four ulnar nerve stimulation was measured. Twenty–seven patients received 1 mg–kg^-1 of succinylcholine, followed by 0.15 mg kg^-1 of vecuronium when the electromyographic response recovered to 50% of control after succinylcholine–induced neuromuscular blockade. The other 27 patients served as the control group, receiving 0.15 mg kg^-1 of vecuronium without prior administration of succinylcholine. In both groups, administration of supplemental 0.04 mg kg^-1 of vecuronium was repeated whenever the electromyographic response recovered to 25% of control during surgical procedures. The duration of blockade induced by the initial 0.15 mg kg^-1 of vecuronium was 56.5 ± 12.8 (mean ± s.d.) min for the group with succinylcholine, and 58.5 ± 21.5 min for the control group. In both groups, the average duration of four consecutive supplemental doses of vecuronium was approximately 35 min. No significant differences between groups were found in the duration of neuromuscular blockade induced by initial and supplemental doses of vecuronium.     

The independent metabolic effects of enflurane anaesthesia and surgery

The metabolic effects of enflurane anaesthesia (1MAC) in air/oxygen were investigated in six healthy unpremedicated women scheduled for total abdominal hysterectomy (TAH). The changes in acid-base status, CO2 production, and circulating concentration of total protein, albumin and a variety of metabolites (glucose, lactate, glycerol and alanine) were measured before and during a 2-h period of anaesthesia alone, during 1 h of anaesthesia plus surgery, and in the recovery period. The subjects were maintained normothermic (36.5 +/- 0.3 degrees C), and with an arterial SaO2 above 95% throughout the period of study. The circulating concentration of all metabolites changed little as a result of anaesthesia alone, but the glucose and lactate levels rose rapidly after the onset of surgery (P less than 0.05). Plasma albumin and total protein concentration decreased during the study, reaching values that were significantly lower than the pre-anaesthetic values (P less than 0.05). CO2 production decreased by 9% during anaesthesia and surgery, but returned towards preoperative values during recovery. This study provides no evidence of any significant effect of enflurane anaesthesia alone on human intermediary metabolism. Most of the changes in circulating metabolite concentrations observed during and after anaesthesia and surgery are likely to be due to the surgical stress.     

Relationships between block-of-twitch and train-of-four fade in the mouse phrenic nerve-diaphragm preparation

The relationships between the block-of-twitch and train-of-four fade in the presence of nondepolarizing neuromuscular blocking drugs (d-tubocurarine, vecuronium and pancuronium) were examined in vitro by measuring the contractile tension from mouse phrenic nerve-diaphragm preparations. The slope of the block/fade relationship differed between onset of and recovery from neuromuscular block following single doses of d-tubocurarine, vecuronium or pancuronium. Decreasing the dose of d-tubocurarine or using a divided dose technique to accelerate onset (i.e., priming) increased the amount of fade for a given amount of block. In addition, the block/fade relationships for cumulative dosing and sequential dilution were the same when measurements were made at steady-state for several doses. It is concluded that the block/fade relationship in the mouse phrenic nerve-diaphragm preparation is variable, and is related to the time course of the neuromuscular block. In addition, the block/fade relationships for d-tubocurarine, vecuronium and pancuronium did not differ when determined at steady-state.     

Plication of the diaphragm for symptomatic phrenic nerve paralysis

Paralysis of the diaphragm in infants may produce severe respiratory difficulty because of the paradoxic motion of the affected diaphragm and shift of a mobile mediastinum to the contralateral side. Six infants with diaphragmatic paralysis and severe respiratory distress underwent plication of the diaphragm by a simple technique. Five of the six infants had significant improvement in respiratory effort and were ultimately weaned from ventilatory support. One patient with bilateral paralysis had only minimal improvement. Diaphragmatic function returned in two patients after plication. Plication of the diaphragm is a safe and useful procedure to improve ventilation in infants with a paralyzed diaphragm. Since this technique does not prevent return of diaphragmatic function, it should be employed prior to the development of sequelae of prolonged assisted ventilation and sooner if the phrenic nerve is permanently injured.     

Effects of halothane and enflurane on myocardial metabolism during postischaemic reperfusion in the rat

In experiments on isolated rat heart-lung preparation, the effects of halothane and enflurane on myocardial metabolism during postischaemic reperfusion were evaluated with intramyocardial high energy phosphates, lactate and glycogen. Hearts were perfused for 10 min initially and made globally ischaemic for 8 min. Afterwards, they were reperfused for 12 min. Halothane or enflurane was administered from 5 min after the start of perfusion to the end of reperfusion. There were no significant differences in contents of high energy phosphates between control (C), halothane (H) and enflurane (E) groups (ATP: 15.50 +/- 0.87, 16.05 +/- 1.99 and 15.16 +/- 2.03 mumol/g dry wt, respectively). However, lactate levels in the hearts in Groups H and E were significantly higher than those in Group C (44.04 +/- 10.54, 40.63 +/- 10.34 vs 28.63 +/- 5.98). Slight deterioration in the myocardial oxidation-reduction state may be caused by inhalational anaesthetics when they are administered during the postischaemic reperfusion period.     

Mechanomyography‐Based Wearable Monitor of Quasi‐Isometric Muscle Fatigue for Motor Neural Prostheses

A motor neural prosthesis based on surface functional electrical stimulation (sFES) can restore functional movement (e.g., standing, walking) in patients with a spinal cord injury (SCI). sFES generates muscle contractions in antigravity muscles and allows balance‐assisted standing. This induced standing has several benefits, such as improved cardiovascular function, decreased incidence of urinary infections, reduced joint contractures, and muscle atrophy. The duration of sFES assisted standing is limited due to the quick onset of muscle fatigue. Currently, there is no method available to reliably estimate real‐time muscle fatigue during sFES. Simply monitoring the M‐wave changes is not suitable due to the high signal disturbances that arise during multi‐channel electrical stimulation. Mechanomyography (MMG) is immune to electrical stimulation artifacts and can be used to detect subtle vibrations on the surface of the skin related to activation of the underlying muscle's motor units (MU). The aim of this study was to develop a method for detecting muscle fatigue brought on by sFES. The method was tested in three different heads of the quadriceps muscle in SCI patients during electrically elicited quasi‐isometric contraction. Six spinal cord–injured male volunteers, with no voluntary control of the quadriceps muscle participated in the study. Electrical bursts of voltage‐controlled monophasic square pulses at frequencies of 1 kHz (50% duty cycle) at 50 Hz (15% duty cycle) were used to generate thigh muscle contractions that controlled the knee joint in the sagittal plane. The pulse amplitudes were set to position the knee joint at a 5° angle from the horizontal plane and when the knee angle dropped to 20° (e.g., the quadriceps were unable to hold the lower leg in the desired position), the test was terminated. Two data segments lasting 10 s each, at the beginning and end of each test, were analyzed. The muscle contraction was assessed by MMG sensors positioned on the rectus femoris, vastus lateralis, and vastus medialis muscles. Data segments were decomposed into 11 frequency bands using a Cauchy wavelet transform. In the initial time interval (non‐fatigued muscle), the power peak was concentrated in the 11.31 Hz frequency band. In the final interval (muscle fatigued) this peak shifted to lower frequencies (2 and 6 Hz frequency bands). The decreased frequency was most prominent during the last 4 s of the recordings. It was shown that MMG could be used as a real‐time indicator of muscle fatigue during FES‐induced isometric contraction of quadriceps; hence, MMG could be used in closed‐loop control as a fatigue detector. Subsequent studies for non‐isometric contractions could possibly lead to prediction of muscle fatigue before contractile failure during functional use of the muscle.     

Investigation of the Relationship Between Electrical Stimulation Frequency and Muscle Frequency Response Under Submaximal Contractions

Neuromuscular electrical stimulation (NMES) is a common tool that is used in clinical and laboratory experiments and can be combined with mechanomyography (MMG) for biofeedback in neuroprostheses. However, it is not clear if the electrical current applied to neuromuscular tissues influences the MMG signal in submaximal contractions. The objective of this study is to investigate whether the electrical stimulation frequency influences the mechanomyographic frequency response of the rectus femoris muscle during submaximal contractions. Thirteen male participants performed three maximal voluntary isometric contractions (MVIC) recorded in isometric conditions to determine the maximal force of knee extensors. This was followed by the application of nine modulated NMES frequencies (20, 25, 30, 35, 40, 45, 50, 75, and 100 Hz) to evoke 5% MVIC. Muscle behavior was monitored by the analysis of MMG signals, which were decomposed into frequency bands by using a Cauchy wavelet transform. For each applied electrical stimulus frequency, the mean MMG spectral/frequency response was estimated for each axis (X, Y, and Z axes) of the MMG sensor with the values of the frequency bands used as weights (weighted mean). Only with respect to the Z (perpendicular) axis of the MMG signal, the stimulus frequency of 20 Hz did not exhibit any difference with the weighted mean (P = 0.666). For the frequencies of 20 and 25 Hz, the MMG signal displayed the bands between 12 and 16 Hz in the three axes (P < 0.050). In the frequencies from 30 to 100 Hz, the muscle presented a higher concentration of the MMG signal between the 22 and 29 Hz bands for the X and Z axes, and between 16 and 34 Hz bands for the Y axis (P < 0.050 for all cases). We observed that MMG signals are not dependent on the applied NMES frequency, because their frequency contents tend to mainly remain between the 20‐ and 25‐Hz bands. Hence, NMES does not interfere with the use of MMG in neuroprosthesis.     

Cerebral Energy State and Glycolytic Metabolism During Enflurane Anesthesia in the Rat

The effects of enflurane anesthesia on the cerebral cortical energy state and glycolytic metabolism were studied in rats. Twenty-four rats were divided into four groups with increasing concentrations of enflurane in the arterial blood, i.e. control (1,9±0.3 mg/dl, means+s.e.mean), level I (16.1 ±1.1 mg/dl), level II (26.0± 1.6 mg/dl), and level III (32.9±0.9 mg/dl). At level I, high voltage 1–3 Hz slow waves superimposed on low voltage 10–12 Hz waves were predominant, and at levels II and III, spiking activity and burst suppression were recorded in the EEG. The duration of suppression at level III was significantly longer than that at level II. During enflurane anesthesia, there were no significant differences compared with the control group in the cerebral energy state or energy charge. Glycolytic metabolism remained unchanged except for an increase in glucose at levels II and III. Effects of hypocapnia and hypercapnia were examined in an additional 12 rats with an enflurane concentration in the blood similar to that al level II. Irrespective of PacOz levels, there were no significant changes in cerebral energy charge and glycolytic metabolites except for a decrease in glucose and an increase in lactate at hypocapnia. It was concluded that there was neither evidence of derangement of energy state nor increased anaerobic metabolism in the cerebral cortex during enflurane anesthesia.     

In vivo effects of halothane, enflurane, and isoflurane on hepatic sinusoidal microcirculation

Background: It has been proposed that halogenated anaesthetics interfere with the endothelium-dependent circulatory control by attenuating the effects of endothelium-derived relaxing factor (EDRF/NO). This study was designed to determine whether or not volatile anaesthetics in vivo influence the microvascular tone in hepatic sinusoids. Methods: Using epifluorescence videomicroscopy, we compared the effects of the volatile anaesthetics halothane, enflurane, and isoflurane on hepatic microcirculation in ventilated Lewis rats. Animals were initially anaesthetized with pentobarbitone (50 mg-kg^-1 i.p.) to allow instrumentation and laparotomy and were randomly allocated to one of 4 groups (n=5–6 each) to receive either a supplementary dose of i.v. pentobarbitone (25 mg kg^-1; control group) or 0.75 MAC halothane, enflurane or isoflurane (1.5 MAC h). Results: Halothane decreased significantly the volumetric blood flow as compared with isoflurane (P < 0.05) or pentobarbitone controls (P < 0.05). The decrease in sinusoidal blood flow caused by halothane was largely attributable to a decrease in sinusoidal diameter (P < 0.05), while red blood cell velocity remained unchanged. Isoflurane led to a significant decrease in sinusoidal width compared with controls (P < 0.05) but an increase in red cell velocity offset the effect of sinusoidal narrowing on volumetric blood flow, while enflurane had no significant effect on any of the measured parameters. Conclusion: This study provides the first direct evidence that the volatile anaesthetics halothane and isoflurane in vivo shift the hepatic microvascular tone toward a more constricted state; however, flow velocity is enhanced with isoflurane, offsetting this effect. As a result the volumetric flow is at least affected by isoflurane, then enflurane and most significantly by halothane. Furthermore, our data are consistent with the concept that volatile anaesthetics in clinically relevant concentrations may influence the balance between endothelium-derived vasoactive factors which control microvascular tone.     

Quantifying the interaction of vecuronium with enflurane using closed-loop feedback control of vecuronium infusion

The influence of different levels of enflurane anaesthesia on infusion requirements of vecuronium was studied in 40 adult surgical patients. Ninety percent neuromuscular block was maintained by computer controlled infusion of vecuronium. During the first 90 min study period all patients received fentanyl-nitrous oxide-oxygen (2:1) anaesthesia. For the following 90 min the patients were randomly assigned to receive enflurane at different end-tidal concentrations: group I, control, fentanyl-nitrous oxide anaesthesia; group II, enflurane 0.3%-nitrous oxide; group III, enflurane 0.6%-nitrous oxide; group IV, enflurane 0.9%-nitrous oxide. Every patient served as his/her own control and the changes of vecuronium infusion requirements were determined individually. When the administration of enflurane was started, vecuronium infusion requirements decreased progressively until 90 min. In group II the infusion rate lowered from 80±28 to 56±20 μg . kg^-1 . h ^-1, in group III from 61 ±29 to 34±17 μg . kg^-1 . h^-1 and in group IV from 65±20 to 30± 14 μg . kg^-1 . h^-1. In the control group the infusion rate decreased during the three hour study period from 69± 17 (first 90 min period) to 59± 16 μg . kg^-1 . h^-1 (second 90 min period). Enflurane reduces the dose requirements of vecuronium administered by continuous infusion in a dose- and time-dependent manner.     

Eventration of the diaphragm due to phrenic nerve injury caused by intercostal drainage.

Acquired eventration of the diaphragm is caused by injury to the phrenic nerve with resultant paralysis and elevation of the entire diaphragm. In this reported case, damage to the phrenic nerve was caused by an intercostal drain. This has not been previously reported.     

Is Transcatheter Aortic Valve Implantation of Living Tissue‐Engineered Valves Feasible? An In Vitro Evaluation Utilizing a Decellularized and Reseeded Biohybrid Valve

Transcatheter aortic valve implantation (TAVI) is a fast‐growing, exciting field of invasive therapy. During the last years many innovations significantly improved this technique. However, the prostheses are still associated with drawbacks. The aim of this study was to create cell‐seeded biohybrid aortic valves (BAVs) as an ideal implant by combination of assets of biological and artificial materials. Furthermore, the influence of TAVI procedure on tissue‐engineered BAV was investigated. BAV (n=6) were designed with decellularized homograft cusps and polyurethane walls. They were seeded with fibroblasts and endothelial cells isolated from saphenous veins. Consecutively, BAV were conditioned under low pulsatile flow (500 mL/min) for 5 days in a specialized bioreactor. After conditioning, TAVI‐simulation was performed. The procedure was concluded with re‐perfusion of the BAV for 2 days at an increased pulsatile flow (1100 mL/min). Functionality was assessed by video‐documentation. Samples were taken after each processing step and evaluated by scanning electron microscopy (SEM), immunohistochemical staining (IHC), and Live/Dead‐assays. The designed BAV were fully functioning and displayed physiologic behavior. After cell seeding, static cultivation and first conditioning, confluent cell layers were observed in SEM. Additionally, IHC indicated the presence of endothelial cells and fibroblasts. A significant construction of extracellular matrix was detected after the conditioning phase. However, a large number of lethal cells were observed after crimping by Live/Dead staining. Analysis revealed that the cells while still being present directly after crimping were removed in subsequent perfusion. Extensive regions of damaged cell‐layers were detected by SEM‐analysis substantiating these findings. Furthermore, increased ICAM expression was detected after re‐perfusion as manifestation of inflammatory reaction. The approach to generate biohybrid valves is promising. However, damages inflicted during the crimping process seem not to be immediately detectable. Due to severe impacts on seeded cells, the strategy of living TE valves for TAVI should be reconsidered.     

Ambiguity in the Presentation of Decellularized Tissue Composition: The Need for Standardized Approaches

Decellularization offers great potential to the field of tissue engineering, as this method gives rise to scaffold material with the native organ architecture by removing all cellular material and leaving much of the extracellular matrix (ECM) intact. However, many parameters may affect decellularization efficacy and ECM retention and, therefore, decellularization protocols need to be optimized for specific needs. This requires robust methods for comparison of decellularized tissue composition. Various representation methods are used in literature to express tissue composition (DNA, glycosaminoglycans, collagen, other ECM proteins, and growth factors). Here, we present and compare the various methods used and demonstrate that normalization to either dry or wet decellularized weight might be misleading and may overestimate true component retention. Moreover, the magnitude of the confounding effect is likely to be decellularization treatment dependent. As a result, we propose alternative comparison strategies: normalization to whole organ or to a unit of whole initial organ weight. We believe proper assessment of decellularized tissue composition is paramount for the successful comparison of different decellularization protocols and clinical translation.     

Intestinal Conditioning After Cardiac Arrest: The Use of Normothermic Extracorporeal Membrane Oxygenation in the Non‐Heart‐Beating Animal Model

The effect of normothermic extracorporeal membrane oxygenation (NECMO) on small bowel preservation in a clinically relevant large animal model of expected donation after cardiac death (eDCD) was evaluated. Thirty domestic crossbred donor pigs were divided into five groups. The first group served as the live donation (LD) group, the second group served as the donation after cardiac death (DCD) group, and the remaining were further assigned into three subgroups: E1 group (1 h NECMO support), E3 group (3 h NECMO support), and E5 group (5 h NECMO support). Pathology, electron microscopy, energy metabolism, cell apoptosis, and tight junction (TJ) protein expression level of intestinal mucosa and the level of plasma d ‐lactic acid were evaluated in normal, cardiac death and at the end of extracorporeal support, respectively. The mean arterial pressure and PaO₂ were maintained over 60 and 267 mm Hg during NECMO support, respectively. One hour of extracorporeal support could improve the energy status in intestines of the DCD group. Although the histologic damage and apoptosis of the E1 group had no significant difference with those of the LD and DCD groups (P > 0.05), the levels of intestinal mucosa TJ protein decreased (P < 0.05), and plasma d ‐lactic acid increased progressively (P < 0.05). With the extension of extracorporeal support, the degree of intestinal mucosa damage and intestinal permeability gradually increased, as well as the content of adenosine triphosphate in intestinal mucosa. The normothermic extracorporeal support for 1 h in DCD is beneficial for improving the energy status and viability of the bowel. However, the integrity of intestinal mucosa was destroyed gradually as extracorporeal support time went by. And the activation of intestinal epithelial apoptosis and hyperoxia might be the factors that lead to intestinal mucosa injury.     

Diagnostic Primer Sets for Microsatellite Instability Optimized for a Minimal Amount of Damaged DNA From Colorectal Tissue Samples

Background: The diagnosis of microsatellite instability from a minimal amount of highly damaged DNA, extracted from formalin-fixed, paraffin-embedded tissue by the microdissection method, is difficult. Therefore, optimized primer sets were newly designed for substitution of documented ones.Methods: DNA was extracted from 15 archival colorectal carcinomas and used as templates for polymerase chain reaction. Nine standard microsatellite markers (BAT-25, BAT-26, BAT-40, D18S69, D2S123, D5S346, D10S197, D17S250, and D18S58) were selected for diagnosis of microsatellite instability in colorectal carcinomas. All polymerase chain reaction conditions for primer sets were unified to save experimental time.Results: The primer sets for the latter five markers documented in the literature were redesigned because of poor efficiency for damaged DNA. As a result, the number of DNA samples, sufficiently amplified at all markers, improved from 0% to 93%.Conclusions: Diagnostic primer sets for microsatellite instability, optimized for a minimal amount of damaged DNA from colorectal tissue samples, were established.     

Rapid Speed Modulation of a Rotary Total Artificial Heart Impeller

Unlike the earlier reciprocating volume displacement–type pumps, rotary blood pumps (RBPs) typically operate at a constant rotational speed and produce continuous outflow. When RBP technology is used in constructing a total artificial heart (TAH), the pressure waveform that the TAH produces is flat, without the rise and fall associated with a normal arterial pulse. Several studies have suggested that pulseless circulation may impair microcirculatory perfusion and the autoregulatory response and may contribute to adverse events such as gastrointestinal bleeding, arteriovenous malformations, and pump thrombosis. It may therefore be beneficial to attempt to reproduce pulsatile output, similar to that generated by the native heart, by rapidly modulating the speed of an RBP impeller. The choice of an appropriate speed profile and control strategy to generate physiologic waveforms while minimizing power consumption and blood trauma becomes a challenge. In this study, pump operation modes with six different speed profiles using the BiVACOR TAH were evaluated in vitro. These modes were compared with respect to: hemodynamic pulsatility, which was quantified as surplus hemodynamic energy (SHE); maximum rate of change of pressure (dP/dt); pulse power index; and motor power consumption as a function of pulse pressure. The results showed that the evaluated variables underwent different trends in response to changes in the speed profile shape. The findings indicated a possible trade‐off between SHE levels and flow rate pulsatility related to the relative systolic duration in the speed profile. Furthermore, none of the evaluated measures was sufficient to fully characterize hemodynamic pulsatility.     

Shear Stress‐Induced Total Blood Trauma in Multiple Species

The common complications in heart failure patients with implanted ventricular assist devices (VADs) include hemolysis, thrombosis, and bleeding. These are linked to shear stress‐induced trauma to erythrocytes, platelets, and von Willebrand factor (vWF). Novel device designs are being developed to reduce the blood trauma, which will need to undergo in vitro and in vivo preclinical testing in large animal models such as cattle, sheep, and pig. To fully understand the impact of device design and enable translation of preclinical results, it is important to identify any potential species‐specific differences in the VAD‐associated common complications. Therefore, the purpose of this study was to evaluate the effects of shear stress on cells and proteins in bovine, ovine, and porcine blood compared to human. Blood from different species was subjected to various shear rates (0–8000/s) using a rheometer. It was then analyzed for complete blood counts, hemolysis by the Harboe assay, platelet activation by flow cytometry, vWF structure by immunoblotting, and function by collagen binding activity ELISA (vWF : CBA). Overall, increasing shear rate caused increased total blood trauma in all tested species. This analysis revealed species‐specific differences in shear‐induced hemolysis, platelet activation, and vWF structure and function. Compared to human blood, porcine blood was the most resilient and showed less hemolysis, similar blood counts, but less platelet activation and less vWF damage in response to shear. Compared to human blood, sheared bovine blood showed less hemolysis, similar blood cell counts, greater platelet activation, and similar degradation of vWF structure, but less impact on its activity in response to shear. The shear‐induced effect on ovine blood depended on whether the blood was collected via gravity at the abattoir or by venepuncture from live sheep. Overall, ovine abattoir blood was the least resilient in response to shear and bovine blood was the most similar to human blood. These results lay the foundations for developing blood trauma evaluation standards to enable the extrapolation of in vitro and in vivo animal data to predict safety and biocompatibility of blood‐handling medical devices in humans. We advise using ovine venepuncture blood instead of ovine abattoir blood due to the greater overall damage in the latter. We propose using bovine blood for total blood damage in vitro device evaluation but multiple species could be used to create a full understanding of the complication risk profile of new devices. Further, this study highlights that choice of antibody clone for evaluating platelet activation in bovine blood can influence the interpretation of results from different studies.