Effects of acute blood volume expansion on respiratory mechanics in the rat.

BACKGROUNDS: The effects of acute blood volume expansion (BVE) on the respiratory mechanics of normal animals have been not extensively studied. The subject is of both theoretical and practical interest since BVE is a frequent medical intervention, and the associated increase in cardiac output may occur in different physiopathological situations. OBJECTIVES: To describe the changes in the parameters of respiratory mechanics occurring as an effect of acute BVE and the related increase in cardiac output. METHODS: We applied the end-inflation occlusion method in normal, positive pressure-ventilated rats to measure the respiratory mechanics under control and BVE conditions. RESULTS: Under BVE conditions, we found a statistically significant increase in static respiratory system elastance (E(st,rs)), ohmic airway resistance plus resistance of respiratory system tissues to movement (R(min,rs)), and overall resistance including pendelluft and stress relaxation effects (R(max,rs)). Under BVE conditions, the resistive component due to sole stress relaxation and pendelluft (R(visc,rs)) increased almost significantly while a significant increment in mean respiratory system hysteresis surface area (Hy(rs)) was also found. CONCLUSIONS: Increasing pulmonary blood flow by BVE increases the mechanical work of breathing because of the effects on E(st,rs), R(min,rs) and R(max,rs), and because of the increase in Hy(rs).

Anesthesia and myotonic dystrophy (Steinert's syndrome). The role of total intravenous anesthesia with propofol, cisatracurium and remifentanyl. Case report.

Anesthesia for patients with Steinert's syndrome (myotonic dystrophy, MD) is a challenge for the anaesthetist. MD is a multisystemic disease and the neuromuscular symptoms can be associated with sleep apnea, endocrine disorders (diabetes, hypogonadism, hypothyroidism), cardiac, gastroenteric or cognitive disorders (mental deficiency, attention disorders). The diagnosis is facilitated when one or more of these symptoms are associated with the neuromuscular symptoms; however, the latter are not always present at the onset, which makes the diagnosis of MD a difficult and often late one. The choice of drugs and the choice of anesthesia in these patients can be very challenging for many reasons. A myotonic crisis can be triggered by several factors including hypothermia, shivering and mechanical or electrical stimulation. These patients are very sensitive to the usual anesthetics such as hypnotics and paralyzing agents (both depolarizing and nondepolarizing). The following case report describes pathophysiological considerations and a technique for anaesthesia during thoracic surgery that has been able to assure hemodynamic peroperative stability, early extubation and prolonged respiratory autonomy in a patient affected by this genetic disorder.

[Utility of diagnostic scales for hereditary non-polyposis colon cancer in the Mexican population]. / Utilidad de las escalas diagnósticas para cáncer de colon no polipósico hereditario en la población mexicana.

INTRODUCTION: Hereditary non-polyposis colorectal cancer (HNPCC) represents 2 - 7% of all cancers. Diagnosis is made by means of the Amstedam criteria, or the modified Amsterdam and Bethesda. OBJECTIVE: Aim was to evaluate the clinical application of the diagnostic scales for HNPCC in our population and to determine the clinical characteristics that these patients reveal at the time of diagnosis. METHOD: A retrospective, cross-sectional study in which patients with colon cancer and less than 50 years of age were evaluated in a period of 3 years. The demographic data, patients and relatives history and the characteristics of the tumor were obtained at the time of diagnosis. We applied the Amsterdam criteria, modified Amsterdam and Bethesda to all the patients. RESULTS: 56 of 210 patients were of 50 younger with an average age of 38.3 years. Among the patients 14.3% had familiar cancer history. In 53.6% the tumor was located in right colon, regardless histology they had mucin component and poor cellular differentiation. Only two patients fulfilled criteria of modified Amsterdam and Amsterdam, and no patient fulfilled the Bethesda criteria. CONCLUSIONS: Frequency of CCNPH in our population was 1% by the Amsterdam criteria and modified Amsterdam and 0% by the Bethesda criteria.

Cardiac output measurement by the thermodilution method: an in vitro test of accuracy of three commercially available automatic cardiac output computers.

OBJECTIVE: To describe the accuracy and the reproducibility of the thermodilution flow measurements obtained using 3 commercially available cardiac output computers commonly used in intensive care units. DESIGN: An experimental "in vitro" study. Twelve different values of control flow (Qctr) were measured (Qmsr) using 3 different cardiac output computers (Abbott Critical Care System, Oximetrix 3 SvO2/CO Computer, Baxter Oximeter/Cardiac Output Computer SAT-1; American Edwards Laboratories, 9520 A Cardiac Output Computer). Standard equipment and techniques were employed, taking account of the specific weight and heat of warm water relative to blood. In addition, separate sets of measurements were performed in order to investigate the effect on Qmsr of some variables which may influence the "indicator" loss (time for injection, depth of immersion of the catheter, temperature of the injected fluid). SETTING: Our laboratory, inside the intensive care unit. MEASUREMENTS AND RESULTS: The analysis of the linear regression of Qmsr versus Qctr (r values between 0.992 and 0.984; residual standard deviation values comprised between 0.24 and 0.49 l/min; intercepts and slopes not significantly different from identity line), the values of the percentage errors (PE = [Qctr-Qmsr].100/Qctr; PE mean values 7.9, 5.0 and 13.1), and those of the coefficients of variability (CV = standard deviation mean value, %; CV mean values 5.4, 5.8 and 4.6), show a good level of accuracy and reproducibility of the measurements. Our data confirm previously reported results. Furthermore, the cumulative effect of variables capable of influencing the "indicator" loss, even if corrected according to the "calculation constant" the manufacturers provide, was found to result in statistically significant changes of Qmsr. CONCLUSION: The accuracy and reproducibility of the automatic cardiac computers tested is sufficient for practical clinical purpose. It may also depend on the modality of injection of the cooling bolus, which may significantly influence the effective "indicator" losses.

Acute buflomedil intoxication: a life-threatening condition.

A 15-year-old girl was admitted to ICU in a comatose state. She presented with mydriasis, areflexia, hypoxemia and seizures. She was immediately intubated and connected to a ventilator. The seizures were reversed with intravenous diazepam. CT scan was negative. EEG showed a diffuse fast activity and theta waves with spikes in the anterior and temporal regions, bilaterally. The gastric lavage was suggestive of drug ingestion. The patient completely recovered after 6 h of mechanical ventilation and supportive management. Mydriasis was still present after the resolution of neurological symptoms. The girl told us she had ingested 10 tablets (3 g-55 mg/kg) of Loftyl (buflomedil) for suicidal intention. The buflomedil concentrations at 2-3 h from ingestion were 24.8 mg/l in the blood, 324.4 mg/l in the urine and 6.9 mg/l in the gastric content. The p-desmethyl metabolite was also identified in the urine. Buflomedil is a rheological agent largely used as a vasodilator in some European countries. Some recent reports have emphasized the risk of acute intoxication with this drug. Relatively low doses (50-60 mg/kg) have been associated with an important neurological toxicity and a high mortality. We suggest that the clinical picture we observed might be related to a neuroleptic-type action of buflomedil. We bring to attention the risk of a large, uncontrolled diffusion of a drug capable to cause serious consequences at relatively low doses.

Time scales, persistence and patchiness.

We consider competition in patch-dynamical and more general diffusion-extinction models. These models identify three time scales in ecology. We begin with a reformulation of Levin's 1978 basic model, using a geometric description of diffusion. As in Levin's model, diffusion drives short-term dynamics, and longer-term dynamics depends upon a diffusion-extinction ratio; maximizing this ratio is shown to be an Evolutionarily Stable Strategy. Over still longer times, the effect of organisms upon their environments becomes paramount. We use Mandelbrot's 1977 fractals to develop these models, and thus relate persistence with relative patchiness. Finally, we propose a numerical measure, the fractal exponent H, of successional stage.