Changes in oxygen saturation during weaning from short-term ventilator support after coronary artery bypass graft surgery.

OBJECTIVE: To evaluate changes in oxygenation as measured by pulse oximetry (SpO2) and saturated venous oxygenation (SvO2) during weaning from mechanical ventilator support. DESIGN: Exploratory, pilot study. SETTING: Cardiovascular intensive care unit in a private 691-bed acute care medical center in the South. SUBJECTS: Ten adults between 50 and 76 years of age who had uncomplicated coronary artery bypass graft surgery. OUTCOME MEASURES: SpO2 and SvO2 obtained at start of each weaning event and each minute for 5 minutes thereafter. METHOD: Five discrete events associated with the unit's weaning protocol were studied: ventilator adjustments, continuous positive airway pressure trial, respiratory mechanics, removing continuous positive airway pressure and suctioning, and extubation. Weaning events, initiated by unit staff members, were based on subjects' arterial blood gases, SpO2, respiratory rate, blood pressure, heart rate, level of alertness, and respiratory effort. RESULTS: Both SpO2 and SvO2 changed with weaning. For some subjects these changes were clinically important: SvO2 fell by 10% or more, and SpO2 fell to or below 90%. The assessment parameters guiding the weaning process resulted in some weaning events being initiated when SvO2 was at or below 60%. CONCLUSIONS: Measures of SpO2 and SvO2 are sensitive to changes in oxygenation status during weaning. Although more study is needed, SvO2 measures provide valid information about oxygen status and can be used to guide weaning.

Characterization of rat schwannoma-Schwann cell hybrids.

Sciatic nerve Schwann cells from strain LEC rats, homozygous for the c form of 6-phosphogluconate dehydrogenase (6-PGD), and RN22 rat Schwannoma cells, a subclone of RN2 deficient in hypoxanthine phosphoribosyltransferase and expressing the s form of 6-PGD, were fused to produce 'RNS' hybrid clones which proliferate rapidly in a medium containing hypoxanthine, aminopterin and thymidine (HAT) and express c, s and c/s heterodimeric forms of 6-PGD. RNS cells, like both parents, maintain a high baseline activity of 2', 3'-cyclic nucleotide 3'-phosphohydrolase and, as in RN22, activity of this enzyme is further inducible by 1 mM N6, O2'-dibutyryl 3', 5'-cyclic AMP. The RNS clones resemble normal Schwann cells in the capacity to bind radioiodinated axolemmal fragments to their plasma membranes.

Insulin-like growth factor I/somatomedin C: a potent inducer of oligodendrocyte development.

Cell cultures established from cerebrum of 1-day-old rats were used to investigate hormonal regulation of the development of oligodendrocytes, which synthesize myelin in the central nervous system. The number of oligodendrocytes that developed was preferentially increased by insulin, or by insulin-like growth factor I (IGF-I), also known as somatomedin C. High concentrations (5 micrograms/ml) of insulin were required for substantial induction of oligodendrocyte development, whereas only 3.3 ng of IGF-I per ml was needed for a 2-fold increase in oligodendrocyte numbers. At an IGF-I concentration of 100 ng/ml, oligodendrocyte numbers were increased 6-fold in cultures grown in the presence of 10% fetal bovine serum, or up to 60-fold in cultures maintained in serum-free medium. IGF-I produced less than a 2-fold increase in the number of nonoligodendroglial cells in the same cultures. Type I IGF receptors were identified on oligodendrocytes and on a putative oligodendrocyte precursor cell population identified by using mouse monoclonal antibody A2B5. These results indicate that IGF-I is a potent inducer of oligodendrocyte development and suggest a possible mechanism based on IGF deficiency for the hypomyelination that results from early postnatal malnutrition.