Effects of low and high plasma concentrations of dexmedetomidine on myocardial perfusion and cardiac function in healthy male subjects

BACKGROUND: Dexmedetomidine, a selective alpha2-adrenoceptor agonist, has counteracting effects on the cardiovascular system. It mediates sympatholysis by activating alpha2 adrenoceptors in the central and peripheral nervous system, and vasoconstriction and vasorelaxation by activating postsynaptic alpha2 adrenoceptors in blood vessels. The goal of this study was to determine the effects of therapeutic and high concentrations of dexmedetomidine on myocardial perfusion and cardiac function in healthy subjects. METHODS: The authors studied 12 healthy young men. Myocardial blood flow (assessed with positron emission tomography), myocardial function (by echocardiography), and hemodynamic data were collected before and during low (measured mean plasma concentration, 0.5 ng/ml) and high (5 ng/ml) plasma concentrations of dexmedetomidine. RESULTS: The low concentration of dexmedetomidine reduced myocardial perfusion (mean difference, -27% from baseline [95% confidence interval, -31 to -23%], P < 0.001) in parallel with a reduction in myocardial oxygen demand (estimated by the rate-pressure product (-23% [-28 to -18%], P < 0.001). The high dexmedetomidine plasma concentration did not further attenuate myocardial perfusion (-3% [-12 to +6%] from low dexmedetomidine, P > 0.05; -29% [-39 to -18%] from baseline, P < 0.001) or statistically significantly affect the rate-pressure product (+5% [0 to +10%], P > 0.05). Systolic myocardial function was attenuated by sympatholysis during the low infusion rate and was further attenuated by a combination of the sustained sympatholysis and increased afterload during the high infusion rate. CONCLUSIONS: In healthy subjects, plasma concentrations of dexmedetomidine that significantly exceed the recommended therapeutic level do not seriously attenuate myocardial perfusion below the level that is observed with usual therapeutic concentrations and do not induce evident myocardial ischemia.     

Positive genetic test led to an early diagnosis of myxoma in a 4-year-old boy

Less than 10% of cardiac myxomas are familial. These familial cases are related to Carney complex, a multiple neoplasia and lentiginosis syndrome. Mutations in the PRKAR1alpha gene are the cause of Carney complex in most patients. We report a boy, who had PRKAR1alpha gene mutation, and atrial myxoma that was diagnosed in a routine echocardiographic study at the age of four years. Surgical excision of myxoma was performed. This case demonstrates the benefit of screening genetically the kindreds of patients with familial myxomas, and the importance of close follow-up of individuals affected with this mutation irrespective of age.     

Principles of multiple organ procurement from cadaver donors

The need for cadaveric organs other than kidneys for transplantation is increasing. Principles and techniques that allow their procurement without jeopardizing renal recovery are outlined. These include utilization of brain dead donors, careful donor selection, and surgery which minimizes warm ischema while avoiding iatrogenic injury. Utilizing this approach, a variety of combinations of organs have been removed and transplanted resulting in satisfactory functional results.     

Effective prenatal care decreases the incidence of low birthweight

In Finland a nationwide free prenatal care system was mandated by law in 1944. At present, 99.9% of Finland's pregnant women use it. The primary aim is to provide advice and care to all women in local centers and to identify pregnant women exhibiting risk factors and refer them to specialized prenatal units located in 21 central hospital districts. This screening has succeeded well since the late 1970s, as judged by the low frequency of stillborn and low birthweight children born outside central hospitals. The rate of preterm birth has decreased by 1% during the latter half of the 1970s and is now 5.8%. This decrease occurred concomitantly with an overall decrease of 55% in the use of betamimetic drugs, which suggests that the use of betamimetic agents has had minor or no significant impact on the reduction of the incidence of prematurity. In order to improve the identification of mothers at high risk for preterm delivery, a mathematical model was constructed that included 13 risk factors. This model successfully identified a class made up of 22% of all women in whom 65% of preterm deliveries occurred, but 35% of mothers delivering prematurely still remained unidentified. Efficient screening of genital tract infections, relieving mothers of heavy work, and developing new oxytocin analogues may further reduce prematurity in the future.     

Bone oedema predicts erosive progression on wrist MRI in early RA--a 2-yr observational MRI and NC scintigraphy study

OBJECTIVES: To investigate if disease assessment by contrast-enhanced dynamic and static magnetic resonance imaging (MRI) and quantitative nanocolloid (NC) scintigraphy gives useful additional information in early rheumatoid arthritis (RA). METHODS: Twenty-seven patients with early RA (disease duration < or =12 months) were followed up for 1 yr and 24 of them for 2 yrs with contrast-enhanced MRI and NC scintigraphy of the wrist joint. Synovial inflammation was assessed by measuring time-dependent enhancement rates (E-rate) from dynamic MRI scans and technetium(99m)-labelled nanocolloid ((99m)Tc-NC) uptake from scintigraphy scans. Synovial membrane hypertrophy, bone oedema and erosions were semiquantitatively scored according to the Outcome Measures in Rheumatology Clinical Trials RA-MRI scoring system from static MR images. Response to the treatment was evaluated based on whether or not > or = 50% improvement was achieved in the tender and swollen joint scores and the Health Assessment Questionnaire score, with normal C-reactive protein (CRP) or erythrocyte sedimentation rate (ESR) levels. Progression of the erosion score on wrist MRI was evaluated as the outcome. RESULTS: The baseline MRI bone oedema score (rho= 0.67), MRI synovitis score (rho= 0.57), ESR (rho= 0.56), CRP (rho= 0.48), E-rate (rho= 0.47) and (99m)Tc-NC uptake (rho= 0.45) were related with the change in the MRI erosion score from baseline to 2 yrs (rho= Spearman's correlation). In the multivariate logistic regression model, the bone marrow oedema score was the only baseline variable that predicted erosive progression at 2 yrs' follow-up (OR 4.2, 95% CI 1.3-13.8). The median (interquartile range) change in the erosion score from baseline to 2 yrs was 0 (0, 0) and 4 (2, 5) in the patients with (n= 9) and without (n= 15) a persistent clinical response over the 2 yrs, respectively (P= 0.001). The non-responders who presented with erosive progression from 1 yr to 2 yrs had higher MRI synovitis scores, bone oedema scores, E-rate and (99m)Tc-NC uptake at 1-yr follow-up than the non-responders without progressive bone damage. CONCLUSION: The degree of local synovial inflammation at baseline, evaluated by dynamic and static MRI and quantitative NC scintigraphy, is closely related to the progression of wrist joint erosions during the first 2 yrs of the disease. Furthermore, at follow-up, if no persistent clinical response is achieved, these imaging methods may help to predict future erosiveness and help in clinical therapeutic decision making.