PubMed Health⌕ Search

Biomedical subjects

H Kirchheim

Publications and source records attributed to H Kirchheim.

At least 37 records · Page 2Linked to original sources
PubMed1979

The separate and combined influences of common carotid occlusion and nonhypotensive hemorrhage on kidney blood flow.

The separate and combined effects of bilateral common carotid occlusion (C.C.O.) and hemorrhage on renal blood flow (R.B.F.) were studied in 11 unanesthetized dogs. C.C.O. increased arterial blood pressure (4.4 kPa; 33 mm Hg) and heart rate (10 beats/min) while R.B.F. remained unchanged. When kidney perfusion pressure was maintained at its resting level during C.C.O. (implanted pneumatic cuff) there was also no change in R.B.F. After cutting the aortic nerves in 2 dogs the increase in blood pressure and heart rate with C.C.O. was greater (10.6 kPa; 80 mm Hg and 72 beats/min); however, there was no change in R.B.F. A blood loss of 16% (13.6 ml/kg) reduced central venous pressure (0.3 kPa; 2 mm Hg), increased heart rate (8-14 beats/min) and decreased arterial mean pressure by a maximum of 0.7 kPa (5 mm Hg) (non-hypotensive hemorrhage, N.H.H.). R.B.F. showed a tendency to rise and 90 min after the onset of bleeding was slightly increased (12% of control). After N.H.H. carotid occlusion had no effect on R.B.F. when kidney perfusion pressure increased; when perfusion pressure was controlled during C.C.O. the maximum observed decrease of R.B.F. was 15 ml/min (5% of control). It is concluded that the control of R.B.F. during the baroreceptor reflex under normovolemia and after a blood loss of 16% in the conscious dog at rest does not involve sympathetic vasoconstrictor effects which result in a significant change in total blood flow.

Animals↗
PubMed1976

An isothermal flowmeter with improved frequency response for measuring tissue blood flow.

An isothermal flowmeter with improved frequency response for measuring tissue blood flow was developed using thermistors. Direct heating of the thermistors allows a simple construction of small (0.5 mm outer diameter) capillary probes which do not require any additional heating coil. The changes of a feedback current necessary to keep the thermistor at a constant increment above tissue temperature indicate tissue blood flow; a second thermistor compensates variations of tissue temperature. The dynamic performance of the device shows a low-pass characteristic with a cut-off frequency higher than 5 Hz. For low flow rates the output signal was found to be proportional to the flow; for higher flow rates a linearization was necessary. Since tissue temperature can be recorded continuously, intermittent quantitative in-vivo calibration seems possibly by evaluation of "heater off" curves in the perfused and non-perfused tissue. As the flowmeter is insensitive to tissue temperature, it can be used for long-term recordings.

Animals↗
PubMed1976

Basal vascular tone in the kidney. Evaluation from the static pressure-flow relationship under normal autoregulation and at maximal dilation in the dog.

In conscious dogs static pressure-flow relationships (I-P curves) were obtained both for the normal autoregulating kidney vasculature and under conditions of maximal vasodilation induced by infusion of papaverine or acetylcholine into the renal artery. Concentration-response curves for the substances infused showed the typical S-shape. Control I-P curves exhibited an autoregulatory plateau; under maximal vasodilation the I-P curves were pressure-passive up to a perfusion pressure of 50 mm Hg, following a power function (1 = a-Pn) with an exponent greater than 1. Under the influence of acetylcholine, renal blood flow was significantly higher than under control conditions even at a perfusion pressure of 20 mm Hg. This indicates that there is an appreciable vascular tone even at a low pressure. The I-P curves under acetylcholine showed a break at about 50 mm Hg, above which the I-P curves were straight lines.

Acetylcholine↗