Autotomy and the sciatic functional index

The rat sciatic nerve serves as a good model of nerve regeneration and, as such, is often used in investigations of nerve repair. After transection of the sciatic nerve, rodents frequently scratch and bite their anesthetic foot, resulting in amputation of one or more toes. This is termed autotomy or autophagy. When these rats are part of a study using the sciatic functional index (SFI), autotomy results in unusable data, since necessary foot landmarks have been removed. It would be helpful, therefore, to be familiar with the phenomenon of autotomy and to know which rats are least likely to mutilate themselves. In our experiment involving 64 rats in which the sciatic nerve was transected and repaired, we found that female Sprague-Dawley rats were significantly less likely to perform autotomy than males (33% vs. 65%, P =.04). In addition, we noted that two-thirds of the autotomies that occurred did so by postoperative week 4 and that tabasco sauce did not decrease this activity. We present our experience and a survey of the literature on autotomy and the SFI. © 1993 Wiley-Liss Inc.     

VESICO-URETERIC REFLUX AND SURGICALLY TREATED PELVI-URETERIC JUNCTION OBSTRUCTION IN INFANTS UNDER THE AGE OF 12 MONTHS

Background : Pelvi-ureteric junction obstruction has been increasingly diagnosed in infants, mostly as a consequence of antenatal ultrasound examinations. Methods : Of 55 infants below the age of 12 months who underwent dismembered pyeloplasty over a 7-year period, we aimed to determine the patterns and outcome of associated vesico-ureteric reflux that was present in 15 (28%) of the 53 infants in whom follow-up was available. Results : A total of eight infants had resolution of their reflux with conservative management and the median time to resolution was 15 months. Five infants proceeded to ureteroneocystotomy. Conclusions : Given the association of vesico-ureteric reflux and pelvi-ureteric junction obstruction, routine cystography is recommended when the diagnosis of pelvi-ureteric junction obstruction is made.     

Enhanced Fluid Removal Guided by Blood Volume Monitoring During Chronic Hemodialysis

Fluid overload predisposes chronic hemodialysis patients to cardiovascular disease, a significant cause of morbidity and mortality in these patients. We evaluated the efficacy of monitoring changes in blood volume during routine hemodialysis to detect fluid overload. Intradialytic changes in blood volume were monitored by continuously measuring hematocrit in all 56 patients in a single dialysis unit over 7 weeks. After Week 1, patients were categorized into 2 separate groups depending on their maximum intradialytic decreases in blood volume. In Group 1, 46 of 56 or 82% had greater than a 5% decrease in blood volume while in Group 2, 10 of 56 or 18% had less than a 5% decrease in blood volume. During Weeks 2–7, dialytic fluid removal was intentionally increased in Group 2 patients by 0.80 ± 0.62 L (mean ± SD) or 47 ± 43%. This intervention resulted in a larger (p < 0.02) intradialytic decrease in body weight (2.7 ± 0.9 kg versus 2.0 ± 0.8 kg) and a larger (p < 0.02) intradialytic decrease in blood volume (15 ± 5% versus 4 ± 1%) than experienced during Week 1 with a low incidence of symptoms. We conclude that there is a significant percentage of chronic hemodialysis patients who can tolerate additional fluid removal without hypovolemic symptoms even though they are considered to be at dry weight by routine physical examination and that the identification of these patients can be facilitated by intradialytic blood volume monitoring.     

ENTERAL VERSUS PARENTERAL NUTRITION AFTER OESOPHAGOGASTRIC SURGERY: A PROSPECTIVE RANDOMIZED COMPARISON

Background: There appears to be an emerging consensus that early postoperative nutritional support benefits the high-risk patient by decreasing septic morbidity, maintaining immunocompetence and improving wound healing. Enteral nutrition via a feeding jejunostomy has been associated with serious complications, with a reported mortality rate as high as 10%. while total parenteral nutrition has also been associated with a wide variety of complications. Methods: Ninety-seven patients undergoing oesophagectomy or gastrectomy underwent pre-operative nutritional assessment and were randomized to receive either total parenteral nutrition (47 patients) or enteral nutrition (50 patients). Results: There was no significant difference in the number of catheter-related complications between the two groups, but 9 (45%) patients in the total parenteral nutrition group had major morbidity (potentially fatal in two patients) requiring active intervention. Conclusions: This study demonstrates enteral nutrition to be safe and associated with mainly reversible minor complications. It is probable that immediate postoperative enteral feeding conserves the gut's integrity. Whether this leads to a reduction in postoperative septic complications has not been demonstrated by this study although there appears to be a trend in this direction, supporting the concept of enteral feeding as ‘primary therapy’. This can be safely, simply and economically achieved using a feeding jejunostomy placed at the time of surgery.     

Consequences of misfilling contemporary vaporizers with desflurane

Desflurane is a volatile anaesthetic that combines low blood gas solubility (blood/gas partition coefficient =0.42 at 37° C), moderate potency (MAC = 6–7%), and high volatility (vapour pressure =681 mmHg at 20° C, boiling point = 23.5° C). The volatility and potency of desflurane prevent its safe use in vaporizers of traditional design. We present a mathematical model which demonstrates the potential for desflurane overdose if contemporary vaporizers are misfilled with desflurane. The most hazardous filling error occurs if an enflurane vaporizer is misfilled with desflurane. The calculated desflurane output of a misfilled enflurane vaporizer at a dial setting of 1% and a temperature of 22° C is 57.8%, or 9.6 MAC. For misfilled enflurane, isoflurane, and halothane vaporizers at dial settings equivalent to one MAC at 22° C, the calculated desflurane output is 14.0, 10.2, and 7.8 MAC, respectively. We conclude that the safe delivery of desflurane will require engineering safeguards, additional monitoring, and education of the anesthesia community.     

The Development and Teaching of the Ethical Principles and Guidelines for Family Scientists*

This article describes the development of the Ethical Principles and Guidelines for Family Scientists that the National Council on Family Relations Board of Directors unanimously approved. Furthermore, it discusses the importance of ethics education for family professionals and provides suggestions for educators. Finally, the ethical principles and guidelines are delineated. We argue that the development of a scholarship on ethics education is important for current and future family scientists.     

The intravascular contribution to fmri signal change: monte carlo modeling and diffusion-weighted studies in vivo

Understanding the relationship between fMRI signal changes and activated cortex is paramount to successful mapping of neuronal activity. To this end, the relative extravascular and intravascular contribution to fMRI signal change from capillaries (localized), venules (less localized) and macrovessels (remote, draining veins) must be determined. In this work, the authors assessed both the extravascular and intravascular contribution to blood oxygenation level-dependent gradient echo signal change at 1.5 T by using a Monte Carlo model for susceptibility-based contrast in conjunction with a physiological model for neuronal activation-induced changes in oxygenation and vascular volume fraction. The authors compared our Model results with experimental fMRI signal changes with and without velocity sensitization via bipolar gradients to null the intravascular signal. The model and experimental results are in agreement and suggest that the intravascular spins account for the majority of fMRI signal change on T₂^*-weighted images at 1.5 T.     

Myocardial perfusion and function in dogs with moderate coronary stenosis

MRI studies of first-pass contrast enhancement with polylysine-Gd-DTPA and myocardial tagging using spatial modulation of magnetization (SPAMM) were performed to assess the feasibility of a combined regional myocardial blood flow and 2D deformation exam. Instrumented closed-chest dogs were imaged at a baseline control state (Cntl) followed by two interventions: moderate coronary stenosis (St) achieved by partial occlusion of the left anterior descending (LAD) and moderate coronary stenosis with dobutamine loading (StD). Hypoperfusion of the anterior region (ANT) of the myocardium (LAD distribution) relative to the posterior wall (POS) based on the upslope of the signal intensity time curve from the contrast-enhanced MR images was demonstrated only with dobutamine loading (ANT:POS Cntl=1.077 ± 0.15 versus ANT:POS StD=0.477 ± 0.11, P<0.03) and was confirmed with radio-labeled microspheres measurements (ANT:POS Cntl=1.18 ± 0.2 ml/min/g versus ANT:POS StD=0.44 ± 0.1 ml/min/g; P<0.002). Significant changes in regional myocardial shortening were only seen in the StD state (P<0.02); the anterior region showed impaired myocardial shortening with dobutamine loading (P=NS), whereas the nonaffected POS region showed a marked increase in shortening when compared with Cntl (Cntl=0.964 ± 0.02 versus StD=0.884 ± 0.03; P<0.001). These results demonstrate that an integrated quantitative assessment of regional myocardial function and semiquantitative assessment of myocardial blood flow can be performed noninvasively with ultrafast MRI.