Bench-to-bedside review: Diaphragm muscle function in disuse and acute high-dose corticosteroid treatment

Critically ill patients may require mechanical ventilatory support and short-term high-dose corticosteroid to treat some specific underlying disease processes. Diaphragm muscle inactivity induced by controlled mechanical ventilation produces dramatic alterations in diaphragm muscle structure and significant losses in function. Although the exact mechanisms responsible for losses in diaphragm muscle function are still unknown, recent studies have highlighted the importance of proteolysis and oxidative stress. In experimental animals, short-term strategies that maintain partial diaphragm muscle neuromechanical activation mitigate diaphragmatic force loss. In animal models, studies on the influence of combined controlled mechanical ventilation and short-term high-dose methylprednisolone have given inconsistent results in regard to the effects on diaphragm muscle function. In the critically ill patient, further research is needed to establish the prevalence and mechanisms of ventilator-induced diaphragm muscle dysfunction, and the possible interaction between mechanical ventilation and the administration of high-dose corticosteroid. Until then, in caring for these patients, it is imperative to allow partial activation of the diaphragm, and to administer the lowest dose of corticosteroid for the shortest duration possible.     

Non‐ablative 1550‐nm erbium‐glass and ablative 10 600‐nm carbon dioxide fractional lasers for acne scars: a randomized split‐face study with blinded response evaluation

Background Non‐ablative 1550‐nm erbium‐doped fractional photothermolysis systems (FPS) and 10 600‐nm carbon dioxide fractional laser systems (CO₂ FS) have been effectively used to treat scars. Objective We compared the efficacy and safety of single‐session treatments of FPS and CO₂ FS for acne scars through a randomized, split‐face, evaluator‐blinded study. Methods Eight patients with acne scars were enrolled in this study. Half of each subject’s face was treated with FPS and the other half was treated with CO₂ FS. We used a quartile grading scale for evaluations. Results At 3 months after the treatment, the mean grade of improvement based on clinical assessment was 2.0 ± 0.5 for FPS and 2.5 ± 0.8 for CO₂ FS. On each side treated by FPS and CO₂ FS, the mean duration of post‐therapy crusting and scaling was 2.3 and 7.4 days respectively and that of post‐therapy erythema was 7.5 and 11.5 days respectively. The mean VAS pain score was 3.9 ± 2.0 with the FPS and 7.0 ± 2.0 with the CO₂ FS. Conclusion We demonstrated the efficacy and safety of single‐session acne scar treatment using FPS and CO₂ FS in East Asian patients. We believe that our study could be used as an essential reference when choosing laser modalities for scar treatment.     

美托洛尔治疗右室流出道室性早搏的效果观察

目的：观察美托洛尔对起源于右室流出道室性早搏的疗效。方法：选择起源于右室流出道的室性早搏患25例，给予美托洛尔治疗，剂量从6．25mg开始，无不良反应后，逐渐加量，最大剂量每天100－150mg，疗程3个月，用药前后查12导联体表心电图、24小时动态心电图及结合临床症状进行评定。结果：①临床症状评定：胸闷心悸25例，治疗后减轻20例，有效率为80％；焦虑20例，治疗后症状均消失，有效率为100％；头晕14例，治疗后减轻12例，有效率为85．7％。②室性早搏评定：25例中达到室性早搏抑制率70％有11例，有效率为44％；平均室性早搏抑制率为45．6％，6例成对室性早搏抑制率为80％，3例短阵室速消失，平均心率降低12．6／min。③生化指标：血糖、胆固醇、甘油、三酯治疗前后无明显改变。④2例因血压低未加药量。结论：美托洛尔治疗起源于右室流出道室性早搏疗效肯定，尤其对运动后早搏增多疗效较好，临床太改善较显，观察中未发现明显不良反应，无致心律失常现象。     

Bioavailability of Phenytoin Acid and Phenytoin Sodium with Enteral Feedings

Study Objective . To compare the absolute bioavailability of phenytoin (PHT) sodium solution and PHT acid suspension in healthy volunteers receiving continuously infused enteral feedings. Design . Randomized, open-label, single-dose, three-period crossover study. Setting . University clinical research center. Subjects . Ten healthy volunteers age 23–43 years. Interventions . The three phases of the study were separated by at least 7 days. During phase A, subjects received PHT sodium 435 mg intravenously over 30 minutes. During phases B and C, subjects had a nasogastric feeding tube placed through which PHT acid suspension 400 mg and PHT sodium solution 435 mg were administered, respectively. For phases B and C, continuous enteral feedings were given by feeding tube for 14 hours before and after the PHT dose. Blood samples were collected over 72 hours after each PHT dose, and the serum was analyzed for PHT. Measurements and Main Results . The rate and extent of PHT absorption and PHT pharmacokinetics were determined using an empirical quadratic function of time method. Bioavailability, rate of absorption, maximum concentration (C_max), and time to maximum concentration (T_max) were compared for the two enteral doses by paired Student's t test. There were no significant differences in bioavailability for PHT acid suspension and PHT sodium solution (0.88 ± 0.15 vs 0.91 ± 0.7, p=0.57, 90% CI −0.14–0.071). The C_max was greater (7.4 ± 0.9 mg/L vs 5.5 ± 1.7 mg/L, p=0.019) and T_max was less (2.5 ± 3.8 vs. 14.8 ± 11.2 hrs, p=0.004) for the sodium solution. The time to 50% fractional absorption (0.33 ± 0.08 vs 3.2 ± 2.4 hrs, p=0.004) and 90% fractional absorption (7.9 ± 6.2 vs 22.3 ± 17.2 hrs, p=0.021) was also significantly shorter for the sodium solution. Conclusion . The absolute bioavailability of the two dosage forms of PHT administered with concomitant enteral feedings were not significantly different, however, the absorption patterns were significantly different, with the sodium solution being more rapidly absorbed.     

Body Surface Mapping and Nontraditional ECG Leads in Patients with Wolff-Parkinson-White Syndrome

A method of ECG mapping from 90 points on the chest surface is described in 41 male and 17 female patients, aged 6 to 59 years. All also underwent invasive electrophysiological investigation and intraoperative epicardial mapping. Fifty-two patients had one, three patients two, and one patient had three anomalous accessory pathways. Two patients had nodoventricular tracts (Mahaim fibers). We distinguished seven zones along the atrioventricular groove (AVG) to compare the data derived from epicardial, endocardial, and body surface mapping. A microcomputer was used for the analysis of all ECGs to construct and analyze the isopotential maps. The criterion for localization of the anomalous accessory pathways was determined after analysis of the data from all 58 patients. The localization criterion was the appearance of a minimal deflection (-0.09 +/- 0.03 mV) on the surface isopotential maps within the first 0.28 msec of the QRS complex. This criterion for localization of anomalous accessory pathways from the chest surface was proposed on the basis of comparison of data from selective coronary angiography, the ventriculogram, and the chest X ray i.e., radiographic-topographic-anatomical data. In 20 patients, 10-20 nontraditional ECG leads were recorded from the chest to reflect the atrioventricular groove. The number of nontraditional ECG leads depended on patient age, weight, and height. Localization of the accessory pathway in one of the seven zones was established by the earliest delta wave and its maximum deviation. It was possible to localize the anomalous accessory pathway and to suspect multiple pathways in 95% of cases using nontraditional ECG leads and the listed criteria.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pregnancy augments nitric oxide-dependent dilator response to acetylcholine in the human uterine artery

The influence of pregnancy on the dilator effects of acetylcholine in the isolated human uterine artery was investigated. Acetylcholine (0.1 nM to 0.1 microM) produced concentration- and endothelium-dependent relaxation of norepinephrine (3 microM)-induced contraction. The relaxation was greater in arteries from pregnant patients (P arteries) than from non-pregnant patients (NP arteries). The maximal relaxation was 53.5+/-3.4% (n=21) in P arteries and 23.5+/-2.5% (n=35) in NP arteries. In both P and NP arteries the cholinergic relaxation was increased in the presence of superoxide dismutase and greatly reduced in the presence of the nitric oxide synthase inhibitors, NG-mono-methyl L-arginine (L-NMMA) and L-nitro-arginine-methylester (L-NAME). The effect of these nitric oxide synthase inhibitors was reversed by L- arginine. We conclude that pregnancy enhances acetylcholine-induced nitric oxide synthesis and release in the human uterine artery.      

Increased number of substitutions in the D-loop of mitochondrial DNA in the sudden infant death syndrome

The purpose of the present study was to investigate substitutions in the D-loop of mitochondrial DNA (mtDNA) in sudden infant death syndrome (SIDS) and controls, since several observations indicate the involvement of mtDNA mutations in SIDS. These include elevated levels of vitreous humour hypoxanthine in SIDS victims, familial clustering without mendelian traits, and observations of increased sleepiness and a lower activity score in infants who later succumbed to SIDS. Eighty-two cases of SIDS and 133 controls were investigated and the D-loop sequences were recorded in the base-pair range 16 055-16 500 in the mtDNA sequence. The sequencing was carried out using the Applied Biosystems Sequenase dye terminator method and a ABD373A sequencer. The recorded D-loop sequences were compared with the Cambridge sequence and differences were recorded as substitutions. The SIDS cases had a tendency towards a higher substitution rate in the D-loop than the controls ( p = 0.088). This observation makes it interesting to search for deleterious mutations in other locations in the mtDNA.