Direct measurement of the preferred sense of NO rotation after collision with argon.

The preferred sense of product molecule rotation (clockwise or counterclockwise) in a bimolecular collision system has been measured. Rotationally inelastic collisions of nitric oxide (NO) molecules with Ar atoms were studied by combining crossed molecular beams, circularly polarized resonant multiphoton ionization probing, and velocity-mapped ion imaging detection. The observed sense of NO product rotation varies with deflection angle and is a strong function of the NO final rotational state. The largest preferences for sense of rotation are observed at the highest kinematically allowed product rotational states; for lower rotational states, the variation with deflection angle becomes oscillatory. Quantum calculations on the most recently reported NO-Ar potential give good agreement with the observed oscillation patterns in the sense of rotation.

Comparison of multiple thawing techniques on thaw time and stability of hemostatic proteins in canine plasma products.

OBJECTIVES: To compare thawing times of fresh frozen canine plasma between a 37 °C warm water bath, running water bath and dry plasma thawer and compare haemostatic protein stability after thawing in a warm water bath or dry plasma thawer. MATERIALS AND METHODS: To measure thawing times, a 240-mL bag of frozen plasma was thawed in warm water bath, running water bath or dry plasma thawer-10 times for each method. To evaluate stability of haemostatic proteins, fresh canine donor plasma samples were split into 120-mL bags and 3-mL control aliquots before freezing. Bags were thawed by warm water bath or dry plasma thawer and aliquots equilibrated to room temperature. Concentrations of haemostatic proteins, albumin, D-dimers, prothrombin time and partial thromboplastin time were obtained. RESULTS: The running water bath had the shortest thaw time: median thaw time of 15 minutes versus 18 minutes for both the dry plasma thawer and warm water bath. Statistically significant differences in partial thromboplastin time, factor VII, factor X, von Willebrand factor, and von Willebrand factor collagen binding assay were detected among groups but were unlikely to be clinically relevant. CLINICAL SIGNIFICANCE: A traditional running water bath provided the fastest thawing time but the dry plasma thawer resulted in the most stable haemostatic proteins.

Biochemical evaluation of storage lesion in canine packed erythrocytes.

OBJECTIVES: To describe the biochemical changes - also known as the storage lesion - that occur in canine packed red blood cells during ex vivo storage. MATERIALS AND METHODS: Ten 125-mL units of non-leuco-reduced packed red blood cells in citrate phosphate dextrose adenine were obtained from a commercial blood bank within 24 hours of donation. Samples were aseptically collected on days 1, 4, 7, 14, 28, 35 and 42 for measurement of sodium, potassium, chloride, lactate, glucose, pH and ammonia concentrations. All units were cultured on day 42. Friedman's repeated measures test with Dunn's multiple comparison test was used for non-parametric data. A repeated-measures analysis of variance with Tukey's multiple comparison test was used for parametric data. Alpha was set to 0·05. RESULTS: All analytes changed significantly during storage. The mean ammonia on day 1 (58·14 g/dL) was significantly lower (P<0·05) than those on days 28 (1266 g/dL), 35 (1668 g/dL) and 42 (1860 g/dL). A significant increase in median lactate concentration over time was also observed, with day 1 (4·385 mmol/L) being significantly less (P<0·05) than days 14 (19·82 mmol/L), 21 (22·81 mmol/L), 35 (20·31 mmol/L) and 42 (20·81 mmol/L). Median pH was significantly decreased after day 7. All bacterial cultures were negative. CLINICAL SIGNIFICANCE: Many biochemical alterations occur in stored canine packed red blood cells, although further studies are required to determine their clinical importance.

Biochemical evaluation of the effects of storage on feline erythrocytes.

OBJECTIVE: To describe the biochemical changes that occur during storage of feline packed red blood cells. METHODS: Feline packed red blood cells were obtained from the manufacturer via overnight delivery immediately following collection. Bag spikes were placed using aseptic technique and samples were drawn on days 1, 4, 7, 14, 21, 28 and 35. Sodium, potassium, chloride, glucose, lactate, pH and ammonia were measured at each time point. Aerobic and anaerobic bacterial cultures were submitted following collection on day 35. RESULTS: There were statistically significant increases in the median concentrations of lactate and ammonia within the first 2 weeks of storage to a concentration of 12·38 mmol/L and 447·96 µmol/L, respectively. Glucose concentrations decreased significantly by day 28 to a mean of 1·86 mmol/L. Median sodium and chloride concentrations increased throughout the course of storage to a concentration of 158·20 and 131·00 mmol/L, respectively. Mean potassium concentrations decreased to a concentration of 2·40 mmol/L. CLINICAL SIGNIFICANCE: These results show that biochemical derangements within feline packed red blood cells are progressive, with some alterations, such as lactate and ammonia, occurring early within the storage periods, while others, including glucose and electrolytes, are slower to develop. Additional prospective research evaluating the clinical effects of these biochemical alterations is required.

The bilateral isodense subdural hematoma on computerized tomographic scan.

Blood causes striking changes on computerized tomography. However, chronic subdural hematomas may become isodense with brain and therefore not visible directly. Midline and ventricular displacement, effacement of cortical sulci, narrowing of white matter on one side, and ventricular distortion should suggest a unilateral isodense process. Bilateral isodense subdural hematomas pose a major problem on computerized tomography since there are no indications of a mass lesion. A negative report could lull the clinician into a false sense of security. In these cases, general disappearance of sulci and considerable narrowing of ventricles are helpful findings. A particularly important and overlooked sign is an abnormally decreased bicaudate cerebroventricular index. Above all, a high degree of suspicion is vital.

Study of single and multiple dose pharmacokinetic/pharmacodynamic modeling of the antihypertensive effects of labetalol.

This was an open-label, two-phase crossover study of labetalol in 11 patients with mild to moderate hypertension. A two- to four-week outpatient placebo phase was followed by a three-day inpatient placebo period. Patients were then randomly assigned to receive either labetalol, 200 mg, as a single dose and three times a day for three days and, on the final day, another single dose or a similar sequence with 300 mg as the single dose and multiple twice a day treatment. A two-week placebo outpatient period was followed by the second phase of the study in which the treatment regimen was reversed for the two groups. Blood samples for the determination of free and conjugated labetalol plasma levels were collected, and blood pressures and heart rate were recorded sequentially for 24 hours after the first and last dose of labetalol, and during the multiple dose treatment period before and two hours after each dose as well as four times daily with the patient supine and upright. Of the 11 patients analyzed, five were men and six were women, ranging in age from 33 to 62 years. Labetalol (200 mg and 300 mg) was rapidly absorbed with peak concentrations achieved in approximately one hour. The pharmacokinetic data best fit a two-compartment pharmacokinetic model with first order absorption. At steady state, the absorption, distribution, and elimination kinetics were similar for both dosage regimens with elimination half life of 7.65 and 7.92 hours for the 200 mg three times a day and 300 mg twice a day regimens, respectively. During the multiple dosing period average steady-state plasma drug concentrations were 0.149 mg/ml and 0.145 mg/ml for the 300 mg twice a day and 200 mg three times a day regimens, respectively. Approximately 12 percent of total plasma labetalol was free drug. The balance was conjugated. The first dose of 200 mg or 300 mg of labetalol significantly (p less than 0.01) lowered standing and supine mean blood pressure over a period of eight to 12 hours, respectively, with peak effects occurring at two (standing) and four (supine) hours. A significant reduction (p less than 0.01) in supine mean blood pressure was present 24 hours after the initial dose of 300 mg. At steady state the antihypertensive effects of the 200 mg three times a day and the 300 mg twice a day dosage regimens were similar.(ABSTRACT TRUNCATED AT 400 WORDS)

Vasopressin and hepatic artery. Effect of selective celiac infusion of vasopressin on the hepatic artery flow.

Electromagnetic flow measurement study was performed in 20 anesthetized dogs to evaluate the effect of selective celiac infusion of vasopressin on the hepatic arterial vasculature. Teh hepatic arterial flow showed a biphasic response with an initial decrease followed by a substantial increase in spite of a continued infusion. The left gastric, splenic, and superior mesentric arteries showed a monophasic response with persistent decrease of flow during the whole infusion. The biphasic response of the hepatic arterial flow is thought to be due to autoregulatory dilative action of the liver to a decrease of the portal flow. The results and previous clinical experience suggest that the selective infusions of vasopressin into arteries supplying the liver can be used for short-term vasoconstrictive therapy of acute gastrointestinal bleeding in patients without liver damage. Further experience is necessary to evaluate the safety of prolonged hepatic infusions in patients with liver damage.

Effect of probenecid on the natriuresis and renin release induced by bumetanide in man.

In a randomized crossover trial in six normal male subjects, the effect of pretreatment with probenecid on natriuresis and renin release in response to bumetanide was studied. The subjects received 120 mEq sodium and 80 mEq potassium per day. A single dose of 2 mg bumetanide was administered on the fourth morning after pretreatment with either placebo or probenecid. Creatinine and uric acid were measured in serum and urine, plasma renin activity was determined by radioimmunoassay of angiotensin I, and plasma and urine concentrations of bumetanide were measured by a highly sensitive radioimmunoassay method. Probenecid reduced both natriuresis and hyperreninemia induced by bumetanide. This effect is postulated to be due not to a direct action on sodium excretion but is probably secondary to inhibition of renal tubular secretion of bumetanide. Consequently, these findings appear to support the concept that the quantity of bumetanide delivered to the tubular lumen is an important determinant of its diuretic effect.

Homocysteine in dogs with systemic inflammatory response syndrome.

OBJECTIVES: To compare serum concentrations of homocysteine in healthy dogs and those fitting the criteria for systemic inflammatory response syndrome and to compare these values to commonly measured B-vitamins. METHODS: Study dogs were classified into non-infectious systemic inflammatory response syndrome or sepsis groups and blood was drawn on Day 1 of the patient's hospitalisation for measurement of serum homocysteine, folate and cobalamin concentrations. Homocysteine concentration was measured in 51 clinically healthy dogs to serve as the control group. RESULTS: A statistically significant difference was found between the homocysteine concentrations of the healthy group when compared to non-infectious systemic inflammatory response syndrome and sepsis groups. Homocysteine values were not correlated with folate, cobalamin or APPLEfast severity scores. Homocysteine concentrations were significantly lower in sick dogs when compared to the control group, which is dissimilar to the human population. CLINICAL SIGNIFICANCE: The clinical significance of homocysteine changes in critically ill dogs is currently unknown.

Intractable bladder hemorrhage: therapeutic angiographic embolization of the hypogastric arteries.

Malignant intractable bladder hemorrhage in an elderly, high risk patient was controlled effectively with bilateral hypogastric artery occlusion by angiographic placement of oxycel autologous clot emboli. Therapeutic alternatives for intractable bladder hemorrhage are reviewed briefly with particular emphasis on angiographic arterial occlusion. Appropriate anatomic and physiologic aspects of this therapy are discussed.

Similarity of arterial and intravenous vasopressin on portal and systemic hemodynamics.

The effects of superior mesenteric arterial and intravenous infusions of vasopressin and low and high dose intravenous infusions of vasopressin on splanchnic and systemic hemodynamics were compared in 20 anesthetized dogs. The following parameters were evaluated: flow in the superior mesenteric artery and portal vein, portal and systemic blood pressure, and cardiac output. In the comparison of selective arterial and intravenous infusions, no statistically significant difference was found between the degree of changes in portal flow, portal and systemic blood pressure, and cardiac output. Only the superior mesenteric artery flow showed a greater decrease with the selective arterial injection. In a comparison of intravenous high dose (corresponding to that used clinically) and low dose (one-fifth) infusions of vasopressin, a relatively high splanchnic and low systemic effectiveness of the low dose was found. It resulted in only a 15 to 20% smaller effect on flow in the superior mesenteric artery and portal vein and portal pressure; however, about 40% lesser systemic effect on arterial blood pressure and cardiac output than the high dose. The results of this experimental work warrant exploration in clinical practice, preferably by a controlled study. If clinical success in controlling hemorrhage confirms these hemodynamic results, an intravenous. low dose infusion of vasopressin would appear to be the method of choice in the vasoconstrictive therapy of gastrointestinal bleeding from varices.

Therapeutic embolization for intractable chronic bleeding.

Intractable, chronic vaginal and/or vesicle bleeding complicating pelvic cancers in five women was treated by transcatheter embolization of the hypogastric artery or its branches. Bleeding was presumed to be from hypervascular granulation tissue formed in response to irradiation in two patients and from tumor tissue in three. The embolic materials were Gelfoam and Oxycel reinforced autologous clots. Bleeding was stopped or reduced in volume by at least 90% in each patient. This form of therapy was useful even though bleeding site was not demonstrated angiographically.