RESUMEN

Measuring diet choice in grazing animals is challenging, complicating the assessment of feed efficiency in pasture-based systems. Furthermore, animals may modify their intake of a forage species depending on its nutritive value and on their own physiological status. Various fecal markers have been used to estimate feed intake in grazing animals. However, plant-wax markers such as n-alkanes (ALK) and long-chain alcohols may provide reliable estimates of both dietary choices and intakes. Still, their use in beef cattle has been relatively limited. The present study was designed to test the reliability of the ALK technique to estimate diet choices in beef heifers. Twenty-two Angus-cross heifers were evaluated at both post-weaning and yearling age. At each age, they were offered both red clover and fescue hay as cubes. Following 3-week acclimation periods, daily intake of each forage species was assessed daily for 10 days. During the final 5 days, fecal grab samples were collected twice daily. The ALK fecal concentrations were adjusted using recovery fractions compiled from literature. Diet composition was estimated using two statistical methods. Post-weaning, dietary choices were reliably estimated, with low residual error, regardless of the statistical approach adopted. The regression of observed on estimated red clover proportion ranged from 0.85±0.08 to 1.01±0.09 for fecal samples collected in the p.m. and for daily proportions once averaged, respectively. However, at yearling age, the estimates were less reliable. There was a tendency to overestimate the red clover proportion in diets of heifers preferring fescue, and vice versa. This was due to greater variability in ALK fecal concentrations in the yearling heifers. Overall, the ALK technique provided a reliable tool for estimating diet choice in animals fed a simple forage diet. Although further refinements in the application of this methodology are needed, plant-wax markers provide opportunities for evaluating diet composition in grazing systems in cattle.

Asunto(s)

RESUMEN

Assessing feed efficiency in pasture-based systems can be challenging due to difficulties in measuring feed intake and diet preference. Furthermore, heifers may modify their intake of a particular forage species depending on its nutritive and physical attributes and on their own physiological status. For instance, heifers growing to larger mature sizes have higher maintenance requirements, which may affect their dietary preferences. The present study was designed to determine the influence of frame size (FS) on feed intake and diet selection at 2 age subclasses: postweaning, at, on average, 313 d of age (317 kg BW for larger FS and 285 kg BW for smaller FS), and as yearlings, at, on average, 403 d of age (391 kg BW for larger FS and 343 kg BW for the smaller FS). Twenty-four Angus-cross heifers were evaluated at these ages. They were housed in a drylot equipped with a Broadbent Feeding System and had ad libitum access to cubed red clover and cubed fescue hay in separate buckets. Following 3-wk acclimation periods, DMI of each forage species was assessed daily for 10 d. Body weights were also recorded daily over those 10 d. Larger and smaller FS cattle did not differ in ADG, feed conversion ratio, and Kleiber ratio at either age (P > 0.05). However, heifers from larger FS category had higher total and red clover DMI at both ages (P < 0.05) and higher proportions of red clover in their diet as yearlings (P < 0.001). Cumulative differences between clover and fescue DMI were similar at postweaning in both FS (P > 0.05); however, at yearling age, the larger FS cattle ate consistently and cumulatively more red clover (P < 0.001). The intake and diet selection of heifers across ages were not consistent for either FS category (P = 0.748), suggesting difficulties in predicting lifetime feed efficiencies based on an early measure. Although gains and feed conversion ratios were similar between FS categories, the larger FS heifers ate more. At yearling age, these heifers of larger metabolic size also selected a greater proportion of red clover in their diet. Because the FS and, thereby, BW of cattle affect intakes and diet selections, they also may impact the composition and sustainability of grasslands generally. Therefore, the relationship between FS and pasture usage likely needs to be integrated into descriptions of cow efficiency in pasture-based operations.

Asunto(s)

RESUMEN

Liver enzymes are essential to xenobiotic metabolism. Expression of these enzymes is dependent upon factors such as age and sex. The objective of this study was to determine basal liver enzyme levels in male and female White Leghorn chickens to provide reference values for future studies. Chickens from 2 lines divergently selected for 35 generations for high antibody and low antibody immune response to SRBC were used. Six male and 6 female chickens from each line were killed at each of 4, 8, 12, and 20 wk of age. Livers were collected and used for enzyme analyses. Liver tissue was analyzed for quinone reductase, glutathione-S-transferase, and cytochrome P450 3A4 activity. All data were analyzed using ANOVA. There were no consistent differences in enzyme activity between high- and low-antibody lines at any age. Cytochrome P450 3A4 activity was substantially greater in 4- and 8-wk than in 12- and 20-wk-old chickens (P < 0.001). This study provides insights into enzyme activities of liver enzymes; however, except for cytochrome P450 3A4, no clear trends across ages were observed.

Asunto(s)

RESUMEN

Gossypol, a pigment of cotton, is a hepatic toxin for chickens. Thus, despite its high protein content, inclusion of cottonseed meal in poultry diets is problematic. Silymarin, an extract from milk thistle, has hepatoprotective qualities and could potentially serve as a feed additive to offset the toxicity of gossypol. The objective of this study was to determine if silymarin could counteract gossypol toxicosis. Cockerels (n = 144) from lines divergently selected for humoral immunity were used. Three individuals from each line were randomly assigned to a cage and fed a corn-soybean meal (control) diet for 14 d. Six cages per line were then randomly assigned 1 of 4 dietary treatments (1,000 mg/kg of gossypol, 1,000 mg/kg of silymarin, 1,000 mg/kg of both gossypol and silymarin, or a control diet). Body weight and feed intake data were collected for 21 d, with chickens bled weekly to collect plasma and determine hematocrits. Chickens were then killed, and livers were collected for subsequent histology and enzymatic activity analyses. Endpoints measured weekly were analyzed with repeated measures and regression methodologies. Plasma and liver enzyme activities, and histological measures, were analyzed using ANOVA. No significant interactions between diets and lines were observed. Chickens assigned to the gossypol and gossypol-silymarin diets stopped gaining weight at d 14 (P < 0.001) and lost weight by d 21 (P < 0.001). Gamma glutamyltransferase was also elevated in these chickens at d 14; activities increased further by d 21 (P < 0.001). Histological examination of liver slices indicated substantial lipidosis (P < 0.001). Furthermore, quinone reductase activity was higher in gossypol- and gossypol-silymarin-treated chickens than in control and silymarin-treated chickens (P < 0.001). Silymarin did not alleviate any clinical effects of gossypol toxicosis.

Asunto(s)

RESUMEN

The roles of the carotid arterial baroreceptor reflex and of vagally mediated mechanisms during positive end-expiratory pressure (PEEP) were determined in pentobarbital-anesthetized dogs with isolated carotid sinuses. Spontaneously breathing dogs were placed on PEEP (5-10 cmH2O) with the carotid sinus pressure set to the systemic arterial pressure (with feedback) or to a constant pressure (no feedback). Right atrial volume was measured with a conductance catheter. With carotid baroreceptor feedback before bilateral cervical vagotomy, total peripheral resistance increased (P < 0.01) and mean arterial pressure decreased (-9.8 +/- 4.3 mmHg) in response to PEEP. With no feedback after vagotomy, mean arterial pressure decreased to a greater extent (-45 +/- 6 mmHg, P < 0.01), and total peripheral resistance decreased (P < 0.05) in response to PEEP. In contrast, cardiac index decreased similarly during PEEP (P < 0.01) for all baroreceptor and vagal inputs. This response comprised a decrease in the passive phase of right ventricular filling (P < 0. 01) that was not matched by the estimated increase in active right atrial output. Although the carotid baroreceptor reflex and vagally mediated mechanisms elicit vasoconstriction to compensate for the effects of PEEP on the arterial pressure, these processes fail to defend cardiac output because of the profound effect of PEEP on the passive filling of the right ventricle.

Asunto(s)

Asunto(s)

Asunto(s)

RESUMEN

The radiology nurse's role requires a high level of knowledge, expertise and independence because the department provides services to a wide variety of patients with diverse needs and about whom information may be limited. Radiology nurses routinely start or check peripheral i.v.s, assess infusaports, administer medications, monitor vital signs, suction patients, insert foleys and help patients with their personal needs. The nurse also informs the technologist or radiologist of any unusual patient needs and performs specialized nursing duties, such as administering i.v. sedation or analgesia during special procedures and closely monitoring patients with cardiac/pulse oximeters. Radiology departments call on nurses to care for patients transported from intensive care, patients in emergency situations and pediatric patients and others needing sedation. Teaching is another duty radiology nurses assume, instructing patients and their families, students, technologists, other nurses, radiologists and physicians about patient care. They also teach the radiology staff new nursing policies and national standards as such changes occur. Radiology nurses devote a lot of time to quality improvement and infection control programs: collecting data, keeping records and reporting results. Because radiology nursing is relatively new, the nurse may be called upon to help write patient care policies, design flowsheets or patient instruction sheets and develop protocols or care plans. Radiology nurses utilize skills employed in many other nursing specialties and incorporate them in the radiology setting. They must provide quality nursing care to a large, transient group of patients of all ages, be a spokesperson for patient care and a teacher to other radiology staff members on patient care issues.

Asunto(s)

Asunto(s)

Asunto(s)

RESUMEN

The relationship between the respiratory index (RI = alveolar-arterial oxygen gradient [P(A-a)O2] normalized by PaO2) and the pulmonary shunt (Qsp/Qt) has been examined in 929 studies from 240 critically ill post-traumatic patients. Of these, 88 patients (443 studies) were individuals who developed post-traumatic adult respiratory distress syndrome (ARDS) and 152 were patients (486 studies) who did not develop ARDS. This study demonstrates that the RI to Qsp/Qt [RI/(Qsp/Qt)] relationship was significantly (p less than .0001) increased in patients who developed fatal ARDS compared with those who did not develop ARDS, or with those whose ARDS resolved. Because of the increased oxygen consumption (VO2) in ARDS patients in association with their severe limitations in gas exchange (RI) and increased Qsp/Qt, surviving ARDS patients had a significant increase in the cardiac index which resulted in a higher oxygen delivery to VO2 ratio. ARDS patients showed significant (p less than .0001) evidence of increased pulmonary vascular tone, correlated with the increase in the RI/(Qsp/Qt) relationship. In addition, those patients with high RI/(Qsp/Qt) also had increased right ventricular (RVSW) to left ventricular work (LVSW) ratios which were shown to be a direct function of the rise in RI. This increase in both RVSW/LVSW and RI/(Qsp/Qt) ratios was significantly (p less than .0001) correlated with an increased mortality. Thus, the RI/(Qsp/Qt) relationship, which can be obtained from arterial and mixed venous blood gases and saturations only, can be used to predict the severity of the ARDS process as well as important pulmonary vascular and right ventricular overload consequences.

Asunto(s)

RESUMEN

This study explores the value of combined high-frequency ventilation (CHFV) in a prospective clinical trial of 35 patients suffering from severe post-traumatic and/or septic adult respiratory distress syndrome (ARDS) who were refractory to conventional controlled mechanical ventilatory (CMV) support. The severity of ARDS was quantified by lung mechanics and gas exchange variables and the patients were classified on clinical grounds as well as on the basis of their respiratory index/pulmonary shunt relationship [RI/(Qsp/Qt)]. During the same time period as the CHFV study, data from these patients were compared to those from 88 ARDS patients who had quantitatively similar degrees of respiratory insufficiency, but who were treated only with controlled mechanical ventilation (CMV). The use of CHFV in the 35 CMV refractory patients resulted in an increase in expired tidal volume (VTE) by reducing the CMV inspired tidal volume (VTI) while increasing the volume component derived from high-frequency ventilation (HFV). This procedure appeared to reveal potentially salvageable ARDS patients who were refractory to CMV. In these patients, CHFV significantly reduced pulmonary mean airway pressure (Paw). The RI also decreased significantly and it was possible to reduce significantly the FIO2. In surviving ARDS patients treated with CHFV, an improvement in blood gases at reduced FIO2, without decreased cardiac output, was produced. The CHFV technique was used for less than or equal to 25 days and resulted in 23% survival of patients who were clinically and physiologically indistinguishable from the patients in the ARDS nonsurvivor group who were treated by CMV only. In surviving CHFV patients the decrease in Paw permitted a sustained, or increased, cardiac output with a rise in the oxygen delivery/oxygen consumption ratio, thus allowing for a higher PaO2 for any given level of pulmonary shunt.

Asunto(s)

Asunto(s)

RESUMEN

The management of severe adult respiratory distress syndrome in critically injured patients requires the frequent measurement of arterial blood gases for adjustment of cardiovascular and ventilatory support. Since these require blood withdrawal and laboratory determinations, a noninvasive method of assessment of arterial gas tensions would permit more frequent assessment of the patient as well as permitting rapid changes in the patient's ventilatory status to be detected earlier in the clinical course. The role of transcutaneous O2 and CO2 tension in providing these measurements was evaluated in 92 studies in 38 critically ill patients with ARDS due to trauma and/or sepsis. All patients were normodynamic or hyperdynamic at the time of study (cardiac index 2.5 to 7.6 L/min/m2) and were intubated and on increased inspired oxygen fractions (FIO2 = 30 to 100%) delivered by mechanical ventilation, had a range of body temperature from 35.0 to 39.5 degrees C and pH from 7.29 to 7.57 The data from a transcutaneous O2 and CO2 sensor applied to the skin of the anterior thorax were analyzed by multiple regression analysis of variances. Prediction of the arterial oxygen tension (PaO2) from 52 to 253 torr was possible from regression-corrected measurements of the transcutaneous O2 (TcO2): [PaO2 = 1.1 (TcO2) - 0.28 (FIO2) + 45.5]. The arterial carbon dioxide tension (PaCO2) from 26 to 57 torr was predicted from the transcutaneous CO2 (TcCO2):[PaCO2 = 0.76 (TcCO2) + 0.06 (FIO2) + 0.035 (TcO2) + 4.1]. With these corrections, a noninvasive Respiratory Index was computed for assessing ARDS severity, and dynamic changes in arterial gases could be followed in response to postural changes, ventilatory alterations, or cardiovascular perturbations. These data suggest that a reasonable estimate of the arterial blood gases can be obtained from a regression-corrected measurement of the transcutaneous O2 and CO2 tensions in critically injured normodynamic or hyperdynamic ARDS patients.

Asunto(s)

RESUMEN

The management of impaired respiratory gas exchange in patients with nonuniform posttraumatic and septic adult respiratory distress syndrome (ARDS) contains its own therapeutic paradox, since the need for volume-controlled ventilation and PEEP in the lung with the most reduced compliance increases pulmonary barotrauma to the better lung. A computer-based system has been developed by which respiratory pressure-flow-volume relations and gas exchange characteristics can be obtained and respiratory dynamic and static compliance curves computed and displayed for each lung, as a means of evaluating the effectiveness of ventilation therapy in ARDS. Using these techniques, eight patients with asymmetrical posttraumatic or septic ARDS, or both, have been managed using simultaneous independent lung ventilation (SILV). The computer assessment technique allows quantification of the nonuniform ARDS pattern between the two lungs. This enabled SILV to be utilized using two synchronized servo-ventilators at different pressure-flow-volumes, inspiratory/expiratory ratios, and PEEP settings to optimize the ventilatory volumes and gas exchange of each lung, without inducing excess barotrauma in the better lung. In the patients with nonuniform ARDS, conventional ventilation was not effective in reducing shunt (QS/QT) or in permitting a lower FIO2 to be used for maintenance of an acceptable PaO2. SILV reduced per cent v-a shunt and permitted a higher PaO2 at lower FIO2. Also, there was x-ray evidence of ARDS improvement in the poorer lung. While the ultimate outcome was largely dependent on the patient's injury and the adequacy of the septic host defense, by utilizing the SILV technique to match the quantitative aspects of respiratory dysfunction in each lung at specific times in the clinical course, it was possible to optimize gas exchange, to reduce barotrauma, and often to reverse apparently fixed ARDS changes. In some instances, this type of physiologically directed ventilatory therapy appeared to contribute to a successful recovery.

Asunto(s)