Response of lower esophageal contractility to changing concentrations of halothane or isoflurane: A multicenter study

A multiple-center study was performed to determine the relationship between lower esophageal contractility, clinical signs, and anesthetic concentration as expressed by minimum alveolar concentration (MAC). One hundred four American Society of Anesthesiologists Class I through III patients were exposed to isoflurane (with and without nitrous oxide) or halothane in concentrations of 0.5, 1.0, and 1.5 MAC. Heart rate and systolic blood pressure were continuously monitored. Both the amplitude and frequency of spontaneous and provoked lower esophageal contractions were measured in situ by using a 24-F probe equipped with provoking and measuring balloons. Combined results demonstrated statistically significant correlations (P<0.001) between lower esophageal contractility and MAC. Spontaneous lower esophageal contractions decreased from 1.10±0.12 (SEM) contractions per minute (0.5 MAC) to 0.42±0.05 (1 MAC) to 0.18±0.05 (1.5 MAC). Provoked lower esophageal contractility values decreased from 45±4 mm Hg (0.5 MAC) to 29±3 (1 MAC) to 19±2 (1.5 MAC). Heart rate changes did not correlate with MAC, and systolic blood pressure correlated in only one of three centers. Intracenter and intercenter analyses failed to demonstrate a significant relationship between lower esophageal contractility and heart rate or systolic blood pressure. No intracenter differences in either amplitude or frequency of lower esophageal contractions were observed, despite differences in volatile agents, induction techniques and agents, patient populations, and duration of anesthesia. Our studies indicate that lower esophageal contractility may be an indicator of anesthetic depth as reflected by MAC, but further studies are needed to quantify the effects of surgical stimulus, intravenous anesthetics, vasodilators, anticholinergics, calcium channel blockers, beta-adrenergic agonists, and the presence of a nasogastric tube.     

A Test to Detect Chest Tube Kinking

Objectives: To determine whether the Mac‐technique test can detect kinking of the chest tube upon thoracostomy tube placement. Methods: This was a prospective observational study that was conducted October 2000 through October 2001 in an urban Level 1 trauma center. There were 103 consecutive nonrandomized adult trauma patients who required immediate tube thoracostomy during their initial resuscitation who were entered into the study. The Mac‐technique test was performed during standard tube thoracostomy insertion to the appropriate depth. The test involved grasping the external portion of the thoracostomy tube, turning it clockwise 180°, and then releasing the tube. If the tube spontaneously spun back to its original position, the test was considered positive, and the tube was considered kinked. If the tube did not spontaneously spin back and stayed in position upon release, the test was considered negative. Regardless of the results of this test, the tube was secured, and a postprocedure chest radiograph was obtained. The criterion standard for determining a kinked chest tube was its appearance on this chest radiograph. Results: A total of 103 chest tubes were placed by using the Mac‐technique test. The test was positive in eight placements; four tubes were kinked on chest radiograph. The Mac‐technique test was negative in 95 placements; four tubes were kinked on chest radiograph. The Mac technique had a sensitivity of 50% (95% confidence interval [CI] = 15.7% to 84.3%), a specificity of 95.8% (95% CI = 89.6% to 98.8%), a positive likelihood ratio of 11.9, a negative likelihood ratio of 0.52, and an odds ratio using Yates correction of 20.3 (95% CI = 4.1 to 102.1). Conclusions: On the basis of this study, a positive Mac‐technique test is useful to detect chest tubes that are likely to be kinked after insertion and before securing.     

Maternal origin of transferrin receptor positive cells in venous blood of pregnant women

We studied the origin of transferrin receptor (CD71) positive cells in blood from seven women pregnant with a male fetus in order to explore if fetal cells could be detected among them. We used a technique that allows direct chromosomal analysis by in situ hybridization on immunologically and morphologically classified cells. Enrichment was performed by magnetic activated cell sorting (miniMACS)® using an anti-CD71 monoclonal antibody. The cells were immunophenotyped by alkaline phosphatase anti-alkaline phosphatase immunostaining with the same antibody. The origin of the immunophenotyped cells was studied by in situ hybridization using an X cosmid Y repeat chromosome specific probe cocktail. CD71 positive cells were found in six of the seven women at the range of 4 to 43 in respective samples. Over 90% of the CD71 positive cells were nucleated erythrocytes. None of the detected positive cells were shown to be fetal. Thus, the use of transferrin receptor antigen alone in combination with the miniMACS® may not be sufficient for enrichment of fetal cells.     

Intrathecal midazolam reduces isoflurane MAC and increases the apnoeic threshold in rats

Canadian Journal of Anesthesia/Journal canadien d'anesthésie - The purpose of this study was to examine the anaesthetic requirement of intrathecal midazolam in a dose-response fashion in...     

Nimodipine decreases the minimum alveolar concentration of isoflurane in dogs

Nimodipine is a calcium antagonist that binds with high affinity to neuronal membranes. It is a potent cerebrovasodilator and has been demonstrated also to affect neurotransmitter synthesis and release. Because patients undergoing surgery for intracranial aneurysms are frequently receiving nimodipine, the authors determined the MAC of isoflurane in six dogs before and during three infusion doses of nimodipine (0.5, 1.0 and 2.0 micrograms.kg-1.min-1). MAC was also determined in five dogs before and during infusion of the drug vehicle (10 microliters.kg-1.min-1). Nimodipine produced a reduction in MAC from 1.47 +/- 0.33% to 1.19 +/- 0.18, 1.15 +/- 0.18 and 1.15 +/- 0.09% during infusions of nimodipine 0.5, 1.0 and 2.0 micrograms.kg-1.min-1, respectively (P less than 0.05). Infusion of drug vehicle alone produced no change in MAC (1.39 +/- 0.15%). This reduction in anaesthetic requirement by nimodipine may be due to its effect on neurotransmission. Adjustments in anaesthetic dosage may be necessary in patients receiving nimodipine.     

Numerical simulation of unsteady generalized Newtonian blood flow through differently shaped distensible arterial stenoses

An updated numerical simulation of unsteady generalized Newtonian blood flow through differently shaped distensible arterial stenoses is developed. A shear-thinning fluid modelling the deformation dependent viscosity of blood is considered for the characterization of generalized Newtonian behaviour of blood. The arterial model is treated as two-dimensional and axisymmetric with an outline of the stenosis obtained from a three-dimensional casting of a mildly stenosed artery. The full Navier-Stokes equations governing blood flow are written in the dimensionless form and the solution is accomplished by finite time-step advancement through their finite difference staggered grid representations. The marker and cell (MAC) method comprising the use of a set of marker particles moving with the fluid is used for the purpose. Results are obtained for three differently shaped stenoses – irregular, smooth and cosine curve representations. The present results do agree well with those of existing investigations in the steady state, but contrary to their conclusions the present findings demonstrate that the excess pressure drop across the cosine and the smooth stenoses is caused by neither their smoothness nor their higher degree of symmetry relative to the irregular stenosis, but is rather an effect of area cover with respect to the irregular stenosis. This effect clearly prevails throughout the entire physiological range of Reynolds numbers. Further the in-depth study in flow patterns reveals the development of flow separation zones in the diverging part of the stenosis towards the arterial wall, and they are influenced by non-Newtonian blood rheology, distensibility of the wall and flow unsteadiness in order to validate the applicability of the present model.     

Effects of concentrated growth factors (CGF) on the quality of the induced membrane in Masquelet's technique – An experimental study in rabbits

AimsThe aim of the study was to test if the addition of CGF to the Masquelet technique contributes to the quality of the membrane formed surrounding the polymethylmethacrylate (PMMA), in terms of inflammation, proliferation and vasculazition in the Masquelet technique in the early and late phases in a rabbit model.Materials and methodsA critical bone defect of 15 mm was created in radius diaphysis, leaving 3 cm of intact bone to the joint. To mimic the Masquelet technique and to increase stability, a 6-hole 1.5 mm plate with two screws was applied, although it was initialy stable because of the inherently fixed ulna and radius both proximally and distally in the rabbits. Group 1 and Group 3, were soleley treated with the Masquelet technique as control groups, and were sacrificed at 3 and 6 weeks, respectively. Group 2 and Group 4, were treated with the Masquelet technique + CGF prepared from the rabbit blood groups, and were sacrificed at 3 and 6 weeks, respectively. The groups were compared histopathologically and immunohistochemically, in respect of the means of thickness of the membrane and ratio of elastic fibers, membrane vascularization (CD31), inflammation (MAC387), proliferation (Ki67), and presence of stem cells (STRO-1).ResultsThickness of the membrane and CD31 values were significantly higher in Group 4 than Group 3 (p = 0.004 for both). MAC387 was statistically significantly higher in Group 2 compared to Group 1 and Group 4 compared to Group 3 (p = 0.04 for both). Ki67 was significantly higher in Group 2 compared to Group 1 and Group 4 compared to Group 3 (p = 0.05 and p = 0.006, respectively). Proliferation in the membrane was statistically significantly higher in Group 2 compared to Group 1 (p = 0.05). Likewise, the proliferation index of Group 4 was statistically significantly higher than Group 3 (p = 0.06). STRO-1 was significantly higher in Group 2 compared to Group 1 (p = 0036).ConclusionThe addition of CGF to the Masquelet technique contributes to the quality of the membrane formed, in respect of inducing inflammation and proliferation, maintaining vascularization on large diaphyseal bone defects, and increasing the number of stem cells.     

The Detection of Alcoholism in Hospitalized Schizophrenics: A Comparison of the MAST and the MAC

The Michigan Alcoholism Screening Test (MAST) and the MacAndrew Alcoholism Scale (MAC) were administered to forty-one schizophrenic inpatients also meeting DSM-III criteria for either alcohol abuse or alcohol dependence and 29 schizophrenic inpatients who did not qualify for an additional substance abuse diagnosis other than marijuana abuse/dependence. The MAC failed to differentiate between the alcoholic and nonalcoholic groups and both groups scored above the recommended cutting score. The MAST significantly differentiated the alcoholic and nonalcoholic schizophrenic patients and was as sensitive to a history of alcohol abuse as to alcohol dependence. Neither the MAST nor MAC was sensitive to recent versus more remote drinking. The overall classificatory accuracy of the MAST was found to be 80% and that of the MAC was 56%. A logistic regression analysis revealed that the use of just four MAST items can yield a group classificatory rate of 83%. It was concluded that the MAST exhibited sufficient sensitivity and specificity to be used as an initial screening instrument for alcoholism in schizophrenic patients.