[Primary hyperparathyroidism: parathyroid scintigraphy and ultrasound in problem patients]

AIM

In a retrospective study, the sensitivity of parathyroid scintigraphy and ultrasound was investigated in patients with primary hyperparathyroidism (HPT) with prior histories of surgery of the thyroid or parathyroid (unsuccessful or recidive).

METHODS

Preoperative ultrasound and parathyroid scintigraphy were performed on 65 patients who had had successful surgery and on 12 who had had unsuccessful surgery. The scintigraphy was carried out using a combined double phase/double nuclide technique with 300-600 MBq 99mTc-sestamibi for parathyroid imaging and 80-100 MBq 99mTc-pertechnetate for thyroid imaging.

RESULTS

The sensitivity of parathyroid scintigraphy was 86% in patients with normal thyroid glands, 77% in those with recurrent goiter, and 62% in those with recurrent or persistent HPT. The ultrasound sensitivity was 86%, 50%, and 57% respectively.

CONCLUSION

The sensitivity of parathyroid scintigraphy and ultrasound decreases considerably after surgery. That of parathyroid scintigraphy lay significantly below results published to date. However, parathyroid scintigraphy should be performed precisely in these cases, because the number of alternative parathyroid imaging methods aside from ultrasound are limited.

[Cardiac MR flowmetry: experimental validation and results in patients with operated heart defects]

PURPOSE

A flow-sensitive MR sequence (phase-contrast technique) was evaluated in phantom studies with regard to factors influencing measurements and correctness of results. The sequence was additionally used for functional evaluation of operated congenital heart disease.

METHODS

Pulsatile and constant flow were produced with the help of a phantom. Influence of angulation, range and vessel bending was evaluated. An examination protocol was developed from the results. 35 patients with surgically repaired congenital heart disease or without repair were examined.

RESULTS

A range preset below the actual flow velocity as well as angulation of more than 20 degrees were isolated as main pitfalls in MR flowmetry. In addition to morphological MR findings flow measurements were possible in 11 patients at vessel sites which were not or not completely suited for examination by Doppler ultrasound.

CONCLUSION

The evaluated phase-contrast technique allows for fast and reliable flow quantification if the influences identified in phantom studies are considered.

A thin film microelectrode array for monitoring extracellular neuronal activity in vitro

A planar array of microelectrodes has been developed for monitoring the electrical activity of neurons in cell culture. The microelectrode array was tested and characterized using impedance measurements and SEM. To verify the spatial sensitivity of the microelectrodes we used a specially developed simulation device.

No pulmonary edema or congestion after central venous injection of conventional and newer contrast media in dogs

Our aim was to determine whether large central venous doses of ionic diatrizoate, nonionic iopromide, or nonionic iotrolane produce pulmonary edema or pulmonary congestion in dogs. Eighteen dogs (six per group) anesthetized with piritramide and N2O received three sequential doses (1.5 mL/kg body weight) of one contrast medium in less than 20 seconds. Before the first injection, and again 1, 5, 10, 20, and 30 minutes after each contrast injection, extravascular lung water, pulmonary blood volume, and cardiac output were determined by thermal-dye dilution. Neither extravascular lung water nor pulmonary blood volume increased after any contrast medium. Pulmonary blood volume and cardiac output decreased slightly but not significantly after all contrast media during the course of the study. We conclude that diatrizoate, iopromide, or iotrolane do not produce pulmonary edema or congestion in dogs.

Thermal recovery after passage of the pulmonary circulation assessed by deconvolution

For indicator-dilution studies, complete thermal recovery after passage of heat through the pulmonary circulation would be desirable. However, the results in the literature obtained by extrapolation techniques are inconsistent. To overcome problems of the extrapolation approach, transport functions of the pulmonary circulation (including the left heart) were computed by deconvolution of pulmonary arterial and aortic pairs of thermodilution curves after central venous indicator injection (10 ml of an ice-cold blood indocyanine green dye mixture). Thermal recovery was determined as the finite integral of the transport function. Thirteen mongrel dogs under piritramid-N2O anesthesia were examined under base-line conditions, in orthostasis to alter the distribution of pulmonary blood flow (9 dogs), and in oleic acid edema (8 dogs). Using the deconvolution approach, thermal recovery was 0.97 +/- 0.04 under base-line conditions, 0.96 +/- 0.03 in orthostasis, and 0.96 +/- 0.05 in pulmonary edema. Thermal recovery determined from extrapolated dilution curves was greater than 100% in all groups, a physically impossible finding. It is concluded that thermal recovery is incomplete but insensitive with respect to the distribution of blood flow and to the size of the extravascular compartment. Monoexponential extrapolation is unsuited for the determination of thermal recovery.

[Measuring coronary circulation using an inert gas method--a comparison of common indicator gases]

Validation studies of inert gas techniques are limited in number and usually have not included circumstances with marked heterogeneity of flow. This study was intended to investigate the validity of the method in experimental animals under various hemodynamic conditions by parallel application of helium, argon, krypton and xenon as indicators and by comparison with direct flow measurements. Gases were applied by single breath inhalation. In order to avoid the limitations of conventional methods arising from the systemic recirculation of tracer and from shortened measuring periods we used continuous mass spectrometric recording and numeric deconvolution of the dilution curves in arterial and coronary venous blood. When the transit times are evaluated by "stochastic" analysis and commonly used tissue/blood partition-coefficients (lambda He = 0.95, lambda Ar = 1.1) the helium and argon values are found in reasonable agreement with reference flows. The effects of a shortening of measurements that are based on single integrated samples (Argon method) are shown under control conditions, adenosin infusion and elevated ventricular filling pressure. With xenon (lambda Xe = 0.7) coronary blood flow above 100 ml/min X 100 g is underestimated by the "stochastic" and by the "initial slope technique"; parallel measurements with argon suggest that in the initial slope technique a lambda Xe between 0.8 and 0.9 might be more adequate.

Determination of central blood volume and extravascular lung water

In patients undergoing thoracic surgery central blood volume is subject to large variations and extravascular lung water may change critically due to fluid shifts. Therefore, an accurate monitoring of these parameters, in particular under perioperative conditions, seems to be desirable. This study describes an improved method for the measurement of intrathoracic volumes. Experiments were carried our in 9 mongrel dogs under piritramide-N2O anesthesia. In order to produce low cardiac output in combination with uneven distribution of perfusion, measurements were performed under base line conditions and after postural changes. Indicators (cold and indocyanine green dye) were injected into the v. cava and indicator kinetics were recorded from the pulmonary artery and aorta using thermistor-fiberoptic catheters. The transport functions of cold and dye were computed from the corresponding pairs of dilution curves. From the transport functions, the mean transit times of the intravascular (dye) and diffusible (cold) indicator were determined. Central blood volume and extravascular lung thermal volume were calculated from the mean transit times and a thermodilution cardiac output.

RESULTS

Under base line conditions, central blood volume was 15.3 +/- 2.5 ml/kg body weight. In orthostasis, a significant and reversible reduction to 11.6 +/- 2.4 ml/kg body weight was found. Cardiac output fell significantly from 3.3 +/- 0.5 to 2.4 +/- 1.1. l/min. In contrast, the slight decrease of extravascular lung thermal volume was not statistically significant. It is concluded that the method presented is sensitive enough to detect even small changes of central blood volume.(ABSTRACT TRUNCATED AT 250 WORDS)

Preservation of myocardium in transient ischemia by the thromboxane synthetase inhibitor UK 38.485

This study was performed to examine potential protective effects of UK 38.485, an inhibitor of thromboxane synthetase, in canine myocardium stressed by transient ischemia. On anesthetized open-chest mongrel-dogs (n = 9) repeated ischemia (3 min) was produced by proximal, intermittent occlusion of the left anterior descending artery. A total of 18 occlusions after 3 mg UK 38.485/kg body wt. and 12 occlusions after 5 mg UK 38.485/kg body wt. were compared to a total of 24 occlusions under control conditions. In each experiment, 2-3 control occlusions and 3-4 therapy occlusions were performed. The drug was applied i.v. in a dose of 3 or 5 mg/body wt. 30 min before the first therapy occlusion. In both groups, hemodynamics and energetics did not significantly change as compared to control. The efficiency of the drug in protecting ischemically stressed myocardium was examined by (a) quantification of oxygen debt and oxygen repayment in the occlusion and reperfusion periods and (b) the amounts of inorganic phosphate, lactate, and potassium released in the first minute of reperfusion. Compared to control occlusions, premedication with either 3 or 5 mg UK 38.485 led to a significantly reduced oxygen debt combined with a significant decrease of the release of inorganic phosphate, lactate, and potassium. The protective effect is suggested to be mainly due to enhanced flow to ischemic areas. Data obtained in this study suggest protective effects of the compound in the preservation of myocardium in transient ischemia and attest to the concept that thromboxane A2 may aggravate the metabolic and energetic situation of myocardium in circumstances with reduced oxygen supply.