The effect of volume replacement on serum protein concentration during cardiopulmonary bypass.

Although controversy exists concerning the optimal total protein and colloid osmotic pressure that should be maintained during cardiopulmonary bypass (CPB), the primary volume expanders remain albumin and 6% hetastarch. The purpose of this study was to quantify the effect of adding boluses of volume replacement agents under various conditions to total serum protein values during CPB. A standard CPB circuit was utilized in eight 45-kg swine that had a priming volume (physiologic saline solution) of 2309 +/- 245 mL. Volumetric alterations occurred throughout the CPB period by the addition of combinations of physiologic saline solution, 6% hetastarch or 5% swine albumin. Pre- and postadministration samples were assayed for total serum protein, total protein, and albumin throughout the CPB period and at pre- and postvolume administration times. There was a significant decline in total serum protein with the initiation of CPB (6.14 +/- 0.49 g/dL vs. 3.40 +/- 0.43 g/dL, p < .0001). Addition of 12.5 g of swine albumin (N = 5) to two different swine increased total serum protein significantly when compared to adding 500 mL of 6% hetastarch (N = 6) (swine albumin 12.4 +/- 6.3% vs. hetastarch 3.3 +/- 2.1%, p < .005). A reduction in total serum protein occurred after hemodilution with varying amount of physiologic saline solution: 250-450 mL (7.4 +/- 4.5%), 451-650 mL (9.6 +/- 5.6%), and 651-1050 mL (19.4 +/- 4.0%). In summary, knowledge of total serum protein concentration and estimated circulating blood volume can be used to guide albumin and hetastarch administration following hemodilution.

Higher prevalence of smoking in patients diagnosed as having obstructive sleep apnea.

Nightly nicotine withdrawal as well as other respiratory and pulmonary effects of smoking may result in sleep-disordered breathing, especially obstructive sleep apnea (OSA). We hypothesize that there is higher prevalence of smoking in patients with OSA. We also hypothesize that smoking is an independent risk factor for OSA. The aim of this study is to determine whether there is a higher prevalence of smoking in patients with OSA compared with patients who do not have OSA. To investigate this, we randomly selected a group of 108 patients who were diagnosed as having OSA, defined by an apnea-hypopnea index (AHI) of greater than 10 events per hour. We compared their smoking history with another randomly selected group of 106 patients without OSA, defined by an AHI of less than five events per hour. The prevalence of smoking in patients with OSA was found to be 35%, whereas it was only 18% in patients without OSA. Logistic regression analyses were performed to investigate the effects of smoking while adjusting for age, gender, body mass index (BMI), and number of alcoholic drinks per week. While holding fixed the BMI, gender, age, and number of alcoholic drinks per week, current smokers were found to be 2.5 times more likely to have OSA than former smokers and nonsmokers combined (odds ratio = 2.5, CI 1.3-4.7, p = 0.0049), and 2.8 times more likely to have OSA than former smokers alone (odds ratio = 2.8, CI = 1.4-5.4, p = 0.0028). Adjusted for BMI, gender, age, and number of alcoholic drinks per week, former smokers were not more likely than never smokers to have OSA (odds ratio = 1.2, CI = 0.55-2.7, p = 0.64). We conclude that cigarette smoke may be an independent risk factor for OSA in this referral population.

DNA sequence-dependent deformability deduced from protein-DNA crystal complexes.

The deformability of double helical DNA is critical for its packaging in the cell, recognition by other molecules, and transient opening during biochemically important processes. Here, a complete set of sequence-dependent empirical energy functions suitable for describing such behavior is extracted from the fluctuations and correlations of structural parameters in DNA-protein crystal complexes. These elastic functions provide useful stereochemical measures of the local base step movements operative in sequence-specific recognition and protein-induced deformations. In particular, the pyrimidine-purine dimers stand out as the most variable steps in the DNA-protein complexes, apparently acting as flexible "hinges" fitting the duplex to the protein surface. In addition to the angular parameters widely used to describe DNA deformations (i.e., the bend and twist angles), the translational parameters describing the displacements of base pairs along and across the helical axis are analyzed. The observed correlations of base pair bending and shearing motions are important for nonplanar folding of DNA in nucleosomes and other nucleoprotein complexes. The knowledge-based energies also offer realistic three-dimensional models for the study of long DNA polymers at the global level, incorporating structural features beyond the scope of conventional elastic rod treatments and adding a new dimension to literal analyses of genomic sequences.