Difference in the cardiovascular response to prolonged sitting in men and women.

Orthostatic stress, sitting, results in adjustments of cardiovascular variables to maintain blood pressure and is prominent in a variety of occupations. Sitting serves as the control position for head-out water immersion studies. This study addressed gender differences in the cardiovascular response to prolonged sitting. Ten men and 10 women had cardiovascular measurements in the supine position compared with measurements during 2 hours in the seated position (Sit). Supine cardiovascular measurements were similar for both sexes. Heart rate changed similarly for both sexes with Sit. With Sit, men had elevated mean arterial pressure (9 +/- 3%), total peripheral resistance (54 +/- 9%), and decreased cardiac index (-27 +/- 5%), while women had no change in mean arterial pressure, lesser elevations in total peripheral resistance (17 +/- 7%), and lesser decreases in cardiac index (-12 +/- 5%) than men. Thus men, compared to women, had an elevated mean arterial pressure response to prolonged orthostatic stress.

Hyperemesis, hyperthyroidism, or both?

Nausea and vomiting are common during pregnancy and, when severe enough to require intervention, may develop into the syndrome known as hyperemesis gravidarum. When the diagnosis of hyperemesis is considered, a careful search for secondary causes is necessary. The list of secondary causes includes hyperthyroidism, a relatively uncommon condition during pregnancy. Because many of the signs and symptoms of hyperthyroidism are common, and thyroid function tests are more difficult to interpret during normal pregnancy, making the diagnosis of hyperemesis gravidarum is a challenge. The decision to treat or to await spontaneous resolution depends on the severity of the illness and the likelihood of the presence of true Graves' disease. The case summarized here demonstrates these issues, and includes treatment options for hyperemesis-associated hyperthyroidism.

Effect of the prelaunch position on the cardiovascular response to standing.

Astronauts spend a minimum of 2 h in the reclined seated position (prelaunch position) prior to the launch of the Space Shuttle. This position favors a cephalad shift of blood volume and subsequent loss of body fluid volume, a physiologic situation associated with cardiovascular deconditioning and orthostatic intolerance following spaceflight. It is not known if the prelaunch position results in cardiovascular deconditioning and, therefore, impaired cardiovascular performance during standing. If so, this might hinder the ability of the crewmember to make an emergency egress from the shuttle during the launch. The purpose of this study was to evaluate the cardiovascular responses of men and women to the stand test before and after 2 h in the prelaunch position. Nine men and nine women performed the stand test before and after 2 h in the seated position (SIT), the prelaunch position (PL), or seated immersed to the neck in water (WI). Heart rate, blood pressure, and cardiac output were measured. Men had higher blood pressures than women and demonstrated increases in blood pressure with standing. There were no other gender differences. SIT did not alter the cardiovascular response to standing, while PL and WI resulted in greater increases in heart rate after 2 h in the position. This increase was only 4 to 7 beats/min greater than after SIT, and was the same for PL and WI. Thus, a small, but significant, degree of cardiovascular deconditioning occurred during the minimum time astronauts spend in the prelaunch position.