Single photon emission computed tomography, a rotating gamma camera, and continuous inhalation or infusion of krypton 81m (half life 13 seconds) were used to measure regional ventilation (V), perfusion (Q), and ventilation-perfusion (V/Q) ratios in five normal subjects in supine, prone, and lateral decubitus postures and in three asthmatic patients (supine posture only) before and after inhalation of 2.5 mg nebulised salbutamol. Vertical and horizontal gradients of V, Q, and V/Q were examined at three levels in each lung in regions of 1.9 cm3 size. In normal subjects V and Q increased along the axis of gravity in all postures and at all levels in the lung except for V in the prone position. Smaller horizontal gradients were found with an increase in V and Q from caudal to cranial-again except in the prone posture, where the gradient was slightly reversed. Constraint to outward motion of the ventral chest and abdominal wall is the most likely explanation for the different behaviour in the prone posture. In chronic asthma the vertical gradients of V and V/( were the reverse of normal, but the Q gradient was normal. Bronchodilator treatment did not affect the vertical or horizontal gradients significantly, but analysis of individual regions showed that, relatively, V/0 worsened in 42% of them; this was associated in two thirds with an increase in fractional Q. After inhalation of agonist local vasodilatation may influence V/Q ratios in some units more than bronchodilatation.Three dimensional reconstruction of function in an organ where gravity plays a prominent role offers definite advantages over two dimensional mapping. With emission computed tomography either with single photons (SPECT)' or with positrons (PET)23 ventilation (V), perfusion ((>), and V/Q ratios can be obtained using appropriate radionuclides. Because of their special properties (monoenergetic y ray emission in coincidence) precise attentuation corrections can be made only with positron emission tomography (PET).4 PET machines, in general, offer a limited survey of the lung (at present a maximum of five transaxial cuts), and an online cyclotron is required. With SPECT and a rotating gamma camera the whole lung can be surveyed but the attenuation corrections are extremely complex and of doubtful accuracy, and have generally been omitted.'

SUMMARY BackgroundAlthough exposure to diagnostic radiation may be associated with increased risk of malignancy, the use of abdominal CT (ACT) in the last decade has increased for patients in the emergency department (ED).

BackgroundClinical outcomes of dialysis patients are variable, and improved knowledge of prognosis would inform decisions regarding patient management. We assessed the value of simple, chest X-ray derived measures of cardiac size (cardiothoracic ratio (CTR)) and vascular calcification (Aortic Arch Calcification (AAC)), in predicting death and improving multivariable prognostic models in a prevalent cohort of hemodialysis patients.MethodsEight hundred and twenty-four dialysis patients with one or more postero-anterior (PA) chest X-ray were included in the study. Using a validated calcification score, the AAC was graded from 0 to 3. Cox proportional hazards models were used to assess the association between AAC score, CTR, and mortality. AAC was treated as a categorical variable with 4 levels (0,1,2, or 3). Age, race, diabetes, and heart failure were adjusted for in the multivariable analysis. The criterion for statistical significance was p<0.05.ResultsThe median CTR of the sample was 0.53 [IQR=0.48,0.58] with calcification scores as follows: 0 (54%), 1 (24%), 2 (17%), and 3 (5%). Of 824 patients, 152 (18%) died during follow-up. Age, sex, race, duration of dialysis, diabetes, heart failure, ischemic heart disease and baseline serum creatinine and phosphate were included in a base Cox model. Both CTR (HR 1.78[1.40,2.27] per 0.1 unit change), area under the curve (AUC)=0.60[0.55,0.65], and AAC (AAC 3 vs 0 HR 4.35[2.38,7.66], AAC 2 vs 0 HR 2.22[1.41,3.49], AAC 1 vs 0 HR 2.43[1.64,3.61]), AUC=0.63[0.58,0.68]) were associated with death in univariate Cox analysis. CTR remained significant after adjustment for base model variables (adjusted HR 1.46[1.11,1.92]), but did not increase the AUC of the base model (0.71[0.66,0.76] vs. 0.71[0.66,0.76]) and did not improve net reclassification performance (NRI=0). AAC also remained significant on multivariable analysis, but did not improve net reclassification (NRI=0). All ranges were based on 95% confidence intervals.ConclusionsNeither CTR nor AAC assessed on chest x-ray improved prediction of mortality in this prevalent cohort of dialysis patients. Our data do not support the clinical utility of X-ray measures of cardiac size and vascular calcification for the purpose of mortality prediction in prevalent hemodialysis patients. More advanced imaging techniques may be needed to improve prognostication in this population.

Serum sufentanil and fentanyl concentrations of 0.71 +/- 0.13 ng/ml and 7.3 +/- 1.3 ng/ml, respectively, are on the steep parts of the concentration-response relationships and facilitate prebypass hemodynamic control in patients undergoing coronary artery bypass grafting with opioid-isoflurane anesthesia. Concentrations of sufentanil > or = 1.25 +/- 0.21 ng/ml and of fentanyl > or = 13.3 +/- 2.2 ng/ml minimize isoflurane requirements but do not improve hemodynamic control.