PubMed · 396774
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B L Nichols, V N Nichols. 1979. Lactation.. https://pubmed.ncbi.nlm.nih.gov/396774/
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The magnetic properties and water dynamics of human red blood cells were examined by analysis of the water proton spectra of suspensions of oxygenated, deoxygenated, carbon monoxide-treated, and methemoglobin-containing cells at a magnetic field strength of 7.05 T. Total lineshape analysis of spectra from deoxygenated red blood cell suspensions was performed to determine the transmembrane water exchange rate, the contribution of diffusion in local magnetic field gradients to the transverse relaxation rate, and the difference between the intra- and extracellular chemical shifts of water protons. Mathematical models are proposed to account for the dependence of the chemical shifts and linewidths of these spectra on the magnetic susceptibility or density of the cells.
After being placed on extracorporeal life support (ECLS), newborn patients typically weight 5% to 30% more than their birthweight. Recovery and eventual decannulation from ECLS is associated with a return to baseline weight or birthweight values after a pronounced diuresis. It has been assumed that the increases in weight in these patients are due to increases in extracellular fluid (ECF) and total body water (TBW). This study was undertaken to prove or disprove this hypothesis. ECF space was measured using the compound sodium bromide and TBW was determined with the use of deuterium oxide (nonradioactive heavy water). Fluid compartment measurements were made prior to the institution of ECLS, immediately after placement on bypass, approximately every other day while on bypass, and a final measurement was made once the patient was off bypass. Sodium bromide concentration was analyzed by high-pressure liquid chromatography, and deuterium oxide concentration was measured by the falling drop method. Eight newborns with respiratory failure were placed on either venoarterial (4 patients) or venovenous (4 patients) ECLS for an average of 106 hours (range, 71 to 219 hours). Pre-ECLS TBW was high in the neonates (87% of total body weight v the normal of 75% to 80%). Mean values for each fluid compartment were corrected for the additional volume of the bypass circuit when the patient was on bypass. ECF increased immediately after the institution of ECLS; however, both ECF and TBW decreased during the bypass run, and post-ECLS levels of ECF and TBW were similar to those found prior to ECLS.(ABSTRACT TRUNCATED AT 250 WORDS)
At present, no practical method exists for monitoring the progression and severity of cerebral oedema in a clinical setting on a continuous basis. In search for such a method, we investigated the electrical characteristics of cerebral tissue at microwave frequencies to quantify cerebral oedema. The dielectric constants of normal and oedematous canine cerebral white matter were measured using a Network Analyzer and then compared to the tissue's water content. In addition, salt infiltration and time elapsed after excision of the tissue were examined to determine their effects on the measurements. The water content and dielectric constant of the white matter were linearly related (correlation coefficient, r = 0.903), comparable to results obtained with a Time Domain Reflectometer in previous research. The Network Analyzer, however, is a more robust measurement device and, because of this, can potentially be used for long term measurements. Further, it was found that neither an increased tissue salt content nor the amount of time after excision of the tissue significantly affected the results. This indicates that the dielectric constant of cerebral white matter is mainly a function of the tissue's water content.