Dealing with advance directives for critically ill adolescents

Respecting the values and preferences of adolescents regarding treatment is an essential dimension of nursing practice. As public policy and societal thinking about the role of minors in healthcare decisions evolves, critical care nurses are in a pivotal position to provide leadership and guidance. Critical care nurses who care for adolescents should embrace the opportunity created by the PSDA to implement creative strategies for involving minors in decision making, seek improved methods of assessing decision-making capacity, and document the values and preferences of minors.

Effects of clenbuterol on skeletal muscle mass, body composition, and recovery from surgical stress in senescent rats

Aging decreases skeletal muscle mass and strength, which may be exacerbated by age-related diseases. There is a need for therapeutic agents to prevent or restore loss of skeletal muscle in elderly subjects with muscle wasting disorders. Clenbuterol, a beta 2-adrenergic agonist, dramatically increases skeletal muscle mass in young animals and partially prevents or restores muscle loss in experimental models of muscle wasting. However, the protein anabolic and fat catabolic effects of clenbuterol have not been studied in senescent animals. To determine whether this drug has potential for preventing or repairing muscle loss in elderly subjects, we have examined its effects in young and old rats. Clenbuterol was administered by implanted osmotic minipumps to Fischer-344 rats ages 3, 12, and 23 months, at a dose of 1.5 mg/kg/24 h for 3 weeks. The weights of five hindlimb muscles and carcass protein and fat content were determined. Clenbuterol treatment increased the weight of skeletal muscles 22% to 39% in 3-month-old rats, 19% to 35% in 12-month-old rats, and 22% to 25% in 23-month-old animals. Likewise, clenbuterol increased carcass protein content 19% in 3-month-old rats, 16% in 12-month-old rats, and 24% in 23-month-old animals. Conversely, the drug reduced carcass fat content 36% in 3-month-old rats, 32% in 12-month-old rats, and 38% in 23-month-old rats. Therefore, clenbuterol had similar anabolic and catabolic effects in all age groups. In addition, clenbuterol stimulated recovery of skeletal muscle protein lost following pump implantation in senescent rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of the effect of a protein-free and restricted high protein-low carbohydrate diet on ventricular myosin ATPase activity and isomyosin profile in young rats: evidence that protein-depleted animals are euthyroid

Young rats fed a protein-deficient diet have elevated total triiodothyronine (T3) levels in spite of decreased skeletal muscle protein turnover. Interpretation of the thyroid status of these animals is complicated by increased T3 binding by serum proteins. Free T3 levels ranging from normal to low and decreased resting oxygen consumption have been reported. To investigate the thyroid status of animals fed a protein-free diet, ventricular myosin ATPase activity and isomyosin profile have been used as an index of thyroid hormone activity. The effect of the protein-free diet has been compared to a restricted high protein-low carbohydrate diet, which causes clear evidence of decreased thyroid hormone effect. After 28 d, calcium-activated myosin ATPase activity was 1.50 +/- 0.05 mumol Pi/(mg protein.min) in animals fed the basal diet, 1.16 +/- 0.03 mumol Pi/(mg protein.min) in animals fed the restricted high protein-low carbohydrate diet and 1.48 +/- 0.04 mumol Pi/(mg protein.min) in animals fed the protein-free diet. In addition, a shift in isomyosin content with the appearance of V2 and V3 isomyosins occurred with the restricted high protein-low carbohydrate diet but not the protein-free diet. The failure of the protein-depleted rats to decrease myosin ATPase activity and alter isomyosin content suggests that they are euthyroid.

Effect of graded doses of tri-iodothyronine on ventricular myosin ATPase activity and isomyosin profile in young and old rats

Ventricular myosin ATPase activity, V1 isomyosin content and serum T3 (tri-iodothyronine) values decrease with age in male Fischer 344 rats. To determine if the age decrement in ATPase activity and V1 isomyosin content are caused by decreased T3 levels or an age-related decrease in V1 isomyosin induction by T3, 3-, 12- and 24-month-old male Fischer 344 rats were given constant T3 infusions by osmotic minipump. Rats at all ages were given 0.75, 5 and 15 micrograms(/100 g per 24 h) doses of T3, whereas 12- and 24-month-old rats were given an additional 0.4 microgram dose. In control rats, T3 levels decreased from 97 +/- 2.7 at 3 months to 75 +/- 4.7 ng/100 ml at 24 months. Likewise, Ca2+-activated myosin ATPase activity decreased from 1.04 +/- 0.05 to 0.68 +/- 0.05 mumol of Pi/min per mg of protein, and the relative proportion of V1 of isomyosin decreased from 90 +/- 4.0 to 26 +/- 2.0%. The lowest (0.4 microgram) T3 dose, which was sufficient to restore T3 levels in 24-month-old animals to 3-month control values, abolished the age decrement in myosin ATPase activity and markedly increased the proportion of V1 isomyosin present in the ventricle. These findings indicate that the senescent ventricle responds readily to small doses of T3 and strongly suggest that the age decrement in serum T3 levels is sufficient to contribute to the age-related decrease in myosin ATPase activity and V1 isomyosin content. Since these parameters correlate with ventricular contractility, the age decrement in T3 levels may also contribute to the decreased ventricular contractility and cardiac output observed in senescent rats.