Evaluation of image quality and radiation dose in adolescent thoracic imaging: 64-slice is preferable to 16-slice multislice CT.

There is a constant drive for radiology departments to acquire newer and improved CT machines in order to facilitate faster procedures and a greater repertoire of examinations. However, it is unclear whether the newer technology provides significantly improved image quality, or carries radiation dose implications for patients during everyday clinical practice. We assessed image quality and radiation dose in 15 children and young adults aged 9.3-19.5 years who underwent thoracic imaging on both 16-slice (16CT) and 64-slice (64CT) CT machines. Images were assessed for image quality on a visual analogue scale (1 = unacceptable; 5 = perfect) and preferred image set. All datasets were diagnostically acceptable (scores of 3 or more). The scores for 64CT datasets were significantly better than for 16CT datasets (mean scores of 4.5 and 4.0, respectively; p<0.05). The mean dose-length product (DLP) given was significantly higher during 16CT examinations at 152 mGy cm (effective dose, 2.1 mSv) than for 64CT examinations at 136 mGy cm (1.9 mSv; p<0.05). On average, 64CT examination DLPs were 16 mGy cm (or 9%) lower than the equivalent 16CT examination DLPs. In the context of childhood and adolescent thoracic CT imaging, and using the same software from the same manufacturers, 64CT examinations provide better image quality and give a lower effective dose than do 16CT examinations. If the choice were available, it would be pertinent to use 64CT for this patient group.

Increased inotropic state during splanchnic artery occlusion shock in the dog.

Myocardial function during various forms of shock and its assessment remain the subjects of continuing controversy. Dogs were instrumented for the measurement of a lead II ECG, systemic arterial pressure, LV pressure, LVdP/dt, and LV anterior wall thickness. Afterload was varied with a snare occluder around the aorta. Contractility was assessed by the end-systolic pressure-wall thickness relationship. After taking control measurements, shock was induced by occluding the celiac and the superior and inferior mesenteric arteries for 2 hr followed by reperfusion. The end-systolic pressure-wall thickness relationship was determined at 1 and 2 hr postocclusion and then at 15, 30, 45, and 60 min postrelease and hourly thereafter. The slope of this relationship was either unchanged or increased (ie greater negative slope) during occlusion. Over the first hour of reperfusion of the splanchnic bed the slope averaged 204 +/- 17% of control, and it reached 221 +/- 41% of control by 3 hr postrelease. Myocardial depression was seen only as an agonal event (39 +/- 6% of control). Sham control dogs were stable over a 4 hr period following sham occlusion. Thus, myocardial contractility was increased during splanchnic artery occlusion shock except as a terminal event. Early depression of circulatory performance was a result of decreased venous return and not cardiac dysfunction.

Skeletal muscle insulin unresponsiveness during chronic hyperdynamic sepsis in the dog.

Recent reports from our laboratory and others have documented changes in insulin unresponsiveness and electrolyte and hormonal changes characteristic of hypodynamic shock states in anesthetized animals. Since most acute shock protocols do not adequately mimic the clinical profile of sepsis, the present study was undertaken to document the hemodynamic and metabolic changes associated with chronic hyperdynamic peritonitis in dogs. Mongrel dogs of either sex weighing 20 +/- 2 kg were surgically instrumented with an electromagnetic aortic flow probe for monitoring cardiac output determinations, and aortic and central venous catheters for withdrawing blood for blood pressure and chemical analyses. Following a recovery period (7-10 days) control hemodynamic and metabolic measurements were made. Sepsis was induced (peritoneal abscess) by implanting a 4" X 4" gauze sponge, previously inoculated with human fecal bacteria, amid the intestines. Experimental (N = 18) and pair-fed control (N = 6) animals were monitored daily for 21 days or until death. During the septic protocol, cardiac index increased from a control value of 3.4 L/min/m2 to 5.5 L/min/m2 by the end of the experimental period. Mean arterial blood pressure, total peripheral resistance index, body weight, and plasma Ca++ fell below control values during the experimental period. Body temperature, plasma glucose, insulin, glucagon, and Mg++ were all elevated with sepsis. At the end of the chronic experimental period, skeletal muscle insulin responsiveness was assessed in the isolated, innervated, constantly perfused gracilis muscle preparation. Pair-fed control animals responded to various concentrations of local insulin infusion by increasing glucose uptake by the gracilis muscle. However, septic animals had a blunted response to local insulin infusion resulting in a decrease in the maximum dose response effect. These data demonstrate that: chronic, hyperdynamic peritonitis in the dog more closely mimics the human clinical profile of sepsis; and hyperdynamic sepsis is associated with a state of skeletal muscle insulin unresponsiveness which results from a post-receptor defect.