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At least 235 records · Page 13Linked to original sources
PubMed1986

Transcapillary fluid balance in pre-eclampsia.

The fluid transport between the plasma and interstitial fluid compartment is governed by the Starling forces, i.e. the capillary pressure (Pc), interstitial fluid hydrostatic pressure (Pi) and colloid osmotic pressure in plasma (COPp) and interstitial fluid (COPi). Interstitial fluid was collected from subcutaneous tissue on the thorax and ankle by implanted wicks and Pi was measured using the 'wick-in-needle' technique. In pre-eclampsia, COPp is reduced due to hypoproteinaemia and this predisposes towards loss of fluid from the vascular compartment. An important oedema-preventing mechanism is reduction of COPi, which serves as a homeostatic buffer against increased capillary filtration. This mechanism works in moderate, but not in severe pre-eclampsia. A higher COPi was found both at the thorax (8.3 vs 7.0 mmHg) and ankle (5.9 vs 3.9 mmHg) in the group with severe pre-eclampsia compared with the group moderate pre-eclampsia, in spite of a significant reduction in COPp (15.5 vs 19.9 mmHg). These findings suggest that an increased microvascular permeability of plasma proteins to subcutaneous tissue contributes to COPp reduction in severe pre-eclampsia.

Blood↗
PubMed1995

Balancing learner control and realism with specific instructional goals: case studies in fluid balance for nursing students.

In designing instruction, there is an inherent tension between permitting learner control and focusing on specific instructional goals. This tension is particularly problematic in computer-based clinical case studies. In addition, the question of the appropriate level of realistic detail is central to case study design. More learner control and greater detail require greater complexity and interactivity, and consequently longer development time per case. They may also lead to difficulty in focusing on specific content. This program is designed to present computer-based case studies as an adjunct to classroom instruction in a specific content area, with significant compromises in realism compensated by the potential to focus on a specific set of problems and expose students to a fairly large number of "patients." The degree of learner control is necessarily limited by the program's structure, but the design attempts to allow a considerable amount of self-direction within those limits. The program's main path goes through a series of case studies illustrating a variety of fluid and electrolyte problems. These case studies are fairly simple and tightly structured: history, physical assessment, and laboratory data are presented near the beginning of each study, and learners are given predefined choices with immediate feedback at specified decision points. The case studies are designed to be completed fairly rapidly, typically no more than about thirty minutes per case. The distortion of the case study format by the obvious focus on fluid and electrolyte problems is compensated somewhat by inclusion of a number of cases with no relevant problems. Within this structured format, the program gives the learner control over a number of aspects of the learning experience. Hypertext is used hierarchically, with two levels of explanation for some central concepts and one level for material not directly relevant to the main instructional goals. Consequently, the learner controls content density to a considerable degree. Since nursing students are under pressure to absorb large amounts of clinically relevant information within a relatively short time, the availability of additional information on diagnoses, charting abbreviations, normal ranges for lab values, etc., may provide an added incentive to use the program. Though the case studies are linear with no branching, learners have several options in using them. The basic user mode involves simply going through the case studies and "solving" them: evaluating the data, identifying problems, and making basic treatment decisions. Alternatively, the learner may choose a particular problem and use the program as a "semi-tutorial." Backward movement is allowed, either to review the development of a case or to try again after an incorrect response. Accumulated information is available in an on-screen "chart" for ready reference. A "reference library" is accessible for browsing from any point in the program. Learner evaluation of the program is in progress.

Computer Simulation↗
PubMed1986

Interstitial compliance and transcapillary fluid balance in renal hypertensive rats.

Local interstitial fluid volume (IFV) and pressure (IFP) were used to estimate interstitial compliance (= delta IFV/delta IFP) in skin and skeletal muscle of normotensive (NT) and renal hypertensive rats (HT). The IFV was measured as the extravascular 51Cr-EDTA space, and IFP with micropipettes (tip diameter 2-4 microns) connected to a servocontrolled counter-pressure system. After control measurements, overhydration was induced by infusion of saline, 10% of body weight i.v. with or without venous stasis. Alternatively, dehydration was induced by peritoneal dialysis with 20% glucose or by furosemide infusion with or without 24 h fluid deprivation. Control ECV averaged 24.94 and 24.73 ml per 100 g in NT and HT, respectively (P greater than 0.05). Control PV averaged 2.81 and 3.28 ml per 100 g in NT and HT, respectively (P = 0.061), and control IFP was more positive in HT than in NT: 0.4 mmHg in skin (P less than 0.05) and 0.2 mmHg in skeletal muscle (P greater than 0.05). Dehydration changed PV significantly more in HT than in NT (P less than 0.05). The interstitial volume-pressure curve was linear in dehydration and the initial part of overhydration but gradually levelled off, and the maximal rise in IFP was 1-1.5 mmHg in skin and muscle. Interstitial compliance was calculated from the dehydration part of the volume-pressure curve and was in NT 14% per mmHg both in skin and skeletal muscle. In HT, compliance during dehydration was 10.2 and 20.7% reduction in IFV per mmHg fall in IFP in skin and muscle, respectively, not significantly different from corresponding values in NT (P greater than 0.05). We conclude that HT had unaltered ECV and a tendency to higher PV, and that interstitial compliance was not significantly different in normotensive and hypertensive rats.

Animals↗
PubMed1994

Computer simulation of the effect of dDAVP with saline loading on fluid balance after 24-hour head-down tilt.

Fluid loading (FL) before Shuttle reentry is a countermeasure currently in use by NASA to improve the orthostatic tolerance of astronauts during reentry and postflight. The fluid load consists of water and salt tablets equivalent to 32 oz (946 ml) of isotonic saline. However, the effectiveness of this countermeasure has been observed to decrease with the duration of spaceflight. The countermeasure's effectiveness may be improved by enhancing fluid retention using analogs of vasopressin such as lypressin (LVP) and desmopressin (dDAVP). In a computer simulation study reported previously, we attempted to assess the improvement in fluid retention obtained by the use of LVP administered before FL. The present study is concerned with the use of dDAVP. In a recent 24-hour, 6 degree head-down tilt (HDT) study involving seven men, dDAVP was found to improve orthostatic tolerance as assessed by both lower body negative pressure (LBNP) and stand tests. The treatment restored Luft's cumulative stress index (cumulative product of magnitude and duration of LBNP) to nearly pre-bedrest level. The heart rate was lower and stroke volume was marginally higher at the same LBNP levels with administration of dDAVP compared to placebo. Lower heart rates were also observed with dDAVP during stand test, despite the lower level of cardiovascular stress. These improvements were seen with only a small but significant increase in plasma volume of approximately 3 percent. This paper presents a computer simulation analysis of some of the results of this HDT study.

Computer Simulation↗