Management of gestational nephrolithiasis in the presence of a bicornuate uterus and pelvic kidney

A 39-year-old para 0(+1) woman with known nephrolithiasis within a left-sided pelvic kidney presented with left-sided renal colic at 7 weeks gestation. She had a previous miscarriage due to a bicornuate uterus. Ultrasound and magnetic resonance urography confirmed an incomplete obstruction of the left upper renal tract which was relieved by percutaneous nephrostomy. She presented again at 14 weeks with renal colic and minimal output. An ultrasound confirmed recurrent hydronephrosis and a nephrostogram showed that the catheter had retracted almost completely from the collecting system. This was considered to be due to the upward pressure of the enlarging uterus on the catheter, which had been fixed externally to the skin. This problem was obviated by not securing the replacement nephrostomy tube to the skin. She developed pre-eclamptic toxaemia and gave birth at 35 weeks gestation by caesarean section. The calculus was later dissolved using extra-corporeal shockwave lithotripsy.     

Improved Nonthoracotomy Defibrillation Based on Ventricular Fibrillation Waveform Characteristics

The heart has been shown to be more susceptible to defibrillation at a higher absolute ventricular fibrillation voltage (AVFV) measured on the surface ECG. This study evaluated in a closed-chest canine model (n = 7) the clinical applicability of using a real-time VF waveform analysis system using an electrogram defined between the generator can and an RV endocardial electrode. Under fluoroscopic guidance, superior vena cava and RV spring coil catheter electrodes were inserted through the external jugular vein. A subcutaneous patch was placed on the left chest. A two-parameter tracking algorithm was used to dynamically identify the high AVFV area, and a biphasic shock was triggered synchronously at the next peak. The performance of this new peak shock method (PSM) was compared to the conventional method of shocking at a fixed time in 175 paired trials. Five shocks per voltage and five voltages per animal were randomized between the two methods to permit the generation of sigmoidal dose response curves for the estimation of 50% (E50), 75% (E75), and 100% (E100) success energies. Induction of VF and discharge voltage were kept constant while energy delivered, impedance (R), and AVFV at the point of shock were measured. Energy (8.63 ± 0.40 vs 8.64 ± 0.40 J), R (48.60 ± 0.30 vs 48.59 ± 0.30 Ω), and current (7.50 ± 0.18 vs 7.51 ± 0.16 A) were not significantly different between trials for either the conventional or the PSM. The time from the onset of VF until the defibrillation shock was 7.98 ± 1.44 seconds. Higher overall successes (46.3% vs 33.1%; P < 0.01) and lower E50, E75, and E100 were observed for the PSM. Finally, the significantly higher AVFV (9.12 ± 0.32 vs 4.73 ± 0.34 mV; P < 0.0001) with the peak method suggests that the high VF voltage could be detected as it occurred in real-time. The improved defibrillation success supports the use of this method for nonthoracotomy defibrillation.     

The Harris-Benedict Studies of Human Basal Metabolism: History and Limitations

In the early part of the 20th century, numerous studies of human basal metabolism were conducted at the Nutrition Laboratory of the Carnegie Institution of Washington in Boston, Mass, under the direction of Francis G. Benedict. Prediction equations for basal energy expenditure (BEE) were developed from these studies. The expressed purpose of these equations was to establish normal standards to serve as a benchmark for comparison with BEE of persons with various disease states such as diabetes, thyroid, and other febrile diseases. The Harris-Benedict equations remain the most common method for calculating BEE for clinical and research purposes. The widespread use of the equations and the relative inaccessibility of the original work highlights the importance of reviewing the data from which the standards were developed. A review of the data reveals that the methods and conclusions of Harris and Benedict appear valid and reasonable, albeit not error free. All of the variables used in the equations have sound physiologic basis for use in predicting BEE. Supplemental data from the Nutrition Laboratory indicates that the original equations can be applied over a wide range of age and body types. The commonly held assumption that the Harris-Benedict equations overestimate BEE in obese persons may not be true for persons who are moderately obese. J Am Diet Assoc. 1998;98:439-445.     

Lipid Peroxidation and Formation of 8-Hydroxydeoxyguanosine from Acute Doses of Halogenated Acetic Acids

Chlorinated, brominated, and mixed bromochloro acetates aremajor by-products of water disinfection by chlorine or ozone.The chlorinated acetates, trichloroacetate (TCA) and dichloroacetate(DCA), are carcinogenic in rodents. Brominated analogs of TCAand DCA have received little study. TCA and DCA induce lipidperoxidation in the livers of rodents when administered acutely.Oxidative stress can also result in oxidative damage to DNA,most commonly measured as increases in 8-hydroxydeoxyguanosine(8-OHdG) adducts. In this study, the ability of acute dosesof TCA, DCA, dibromoacetate (DBA), bromodichloroacetate (BDCA),and bromochloroacetate (BCA) to induce lipid peroxidation and8-OHdG formation was examined. Male B6C3F1 mice developed significantincreases in 8-OHdG/dG ratios in nuclear DNA isolated from liverswhen treated with haloacetates. The extent of 8-OHdG formationappeared to be related to the ability to induce thiobarbi-turicacid-reactive substances (TBARS). The order of potency was DBA BCA > BDCA > DCA > TCA. The induction of 8-OHdG wasfound to be generally more sensitive to treatment with haloacetatesthan the TBARS response. Significantly elevated levels of 8-OHdGwere observed at doses of DBA, BCA, and BDCA as low as 30 mg/kg.We suggest that formation of 8-OHdG by brominated haloacetatesmay contribute to their toxicological effects.     

Measurement of Outcomes of General Practice: Comparison of Three Health Status Measures

The broad range of medical problems seen in general practicemeans that the assessment of health outcomes shares much withthe assessment of health status in the general community. Thelast two decades have seen considerable progress in health statusmeasurement for this purpose. This paper reports the use ofthree such measures in a general practice setting. The ‘Randhealth insurance study battery’, the ‘sickness impactprofile’ and the ‘general health questionnaire’were tested in two general practices in Sydney, Australia, todetermine patient compliance, to assess the range of scoresand discriminative ability of the instruments, and to comparethe different instruments. There was a high degree of acceptanceof the questionnaires, showing that patients visiting theirgeneral practitioners are prepared to complete such questionnaires.The range of scores obtained was less skewed for the Rand measuresthan for the sickness impact profile or the general health questionnaire,suggesting that the Rand measures should be the preferred generalhealth status measure.     

Mode of Induction of Ventricular Tachycardia and Prognosis in Patients with Coronary Disease: The Multicenter UnSustained Tachycardia Trial (MUSTT)

Introduction: Programmed stimulation is an important prognostic tool in the evaluation of patients with an ejection fraction ≤40% after myocardial infarction. Many believe that ventricular tachycardia (VT) requiring 3 ventricular extrastimuli (VES) for induction is less likely to occur spontaneously and has less predictive value. However, it is unknown whether the mode of VT induction is associated with long-term prognosis.
Methods and Results: We analyzed a cohort of 371 patients enrolled in MUSTT who had inducible monomorphic VT and who were not treated with antiarrhythmic drugs or an implantable cardioverter defibrillator during the trial. Patients in whom sustained VT was induced with 1 or 2 VES or burst pacing (single VES n = 15, double VES n = 127, burst n = 7, total n = 149) were compared with those in whom VT was induced with 3 VES (n = 222). Compared with the others, patients requiring 3 VES were closer to their most recent myocardial infarction (17 vs 51 months, P = 0.035) and showed a trend toward a lower ejection fraction (26% vs 30%, P = 0.057). VT requiring 3 VES had a shorter cycle length (240 vs 260 ms, P < 0.001). Despite these findings, there was no difference in the incidence of arrhythmic death or cardiac arrest (HR 1.02; 95% CI 0.69-1.51) or all-cause mortality (HR 1.03; 95% CI 0.76-1.39) according to the mode of induction in adjusted analyses.
Conclusions: The prognostic significance of VT induced by 3 VES is similar to that of VT induced by 1 or 2 VES, or burst pacing, in patients with coronary disease and abnormal LV function.     

Separation Between Virtual Sources Modifies the Response of Cardiac Tissue to Field Stimulation

INTRODUCTION: While it is now understood that the tissue geometry and the electric field distribution are important in generating virtual electrodes, the effects of interaction between a collection of electrodes have not been examined. To develop a basis for understanding such interactions, we have studied a single pair of oppositely polarized virtual sources. Although such oppositely polarized pairs of virtual electrodes can be generated by a variety of field distributions and tissue geometries, we examine one simple system that incorporates the salient features of source interaction. METHODS AND RESULTS: Our model system is a homogeneous tissue strip stimulated by a uniform extracellular field. To clarify virtual source interaction, we show that field stimulated tissue can be equivalently polarized by a set of intracellular current sources with magnitude and distribution defined by the generalized activating function. In our model system, an intracellular current source is produced at one edge of the tissue and an intracellular current sink at the other. Therefore, the tissue length acts to modulate the overlap, or interaction, between the polarizations arising from each source. To quantify the effects of source interaction, the chronaxie and rheobase values of the strength-duration relation were determined for source separations varying between 1.0 cm and 100 microm (active membrane dynamics were modeled with the Luo-Rudy phase I formulation). At all separations >3.0 mm, the chronaxie was constant at 3.09 msec and the rheobase was 0.38 V/cm. Under 0.2 mm, the chronaxie decreased to 0.55 msec while the rheobase increased linearly with the inverse of source separation. The dependence of these parameters on separation primarily reflects passive electrotonic interactions between the two virtual electrodes. However, the exact values are strongly dependent upon active tissue properties-largely the inward rectifier potassium channel and activation of the sodium current. CONCLUSION: Tissue excitation in response to field stimulation is strongly modulated by the proximity of, and therefore the interaction between, oppositely polarized virtual electrode sources.