Attenuation of Splanchnic Autotransfusion Following Noninvasive Ultrasound Renal Denervation: A Novel Marker of Procedural Success.

Background: Renal denervation has no validated marker of procedural success. We hypothesized that successful renal denervation would reduce renal sympathetic nerve signaling demonstrated by attenuation of α-1-adrenoceptor-mediated autotransfusion during the Valsalva maneuver.

Methods And Results: In this substudy of the Wave IV Study: Phase II Randomized Sham Controlled Study of Renal Denervation for Subjects With Uncontrolled Hypertension, we enrolled 23 subjects with resistant hypertension.

A Discussion on the Regulation of Blood Flow and Pressure.

This paper discusses two kinds of regulation essential to the circulatory system: namely the regulation of blood flow and that of (systemic) arterial blood pressure. It is pointed out that blood flow requirements sub-serve the nutritional needs of the tissues, adequately catered for by keeping blood flow sufficient for the individual oxygen needs. Individual tissue oxygen requirements vary between tissue types, while highly specific for a given individual tissue.

Clarification of the circulatory patho-physiology of anaesthesia - implications for high-risk surgical patients.

The paper examines the effects of anaesthesia on circulatory physiology and their implications regarding improvement in perioperative anaesthetic management. Changes to current anaesthetic practice, recommended recently, such as the use of flow monitoring in high risk patients, are already beginning to have an impact in reducing complications but not mortality [1]. Better understanding of the patho-physiology should help improve management even further.

Oxygen delivery: the principal role of the circulation.

Autoregulation of blood flow to most individual organs is well known. The balance of oxygen supply relative to the rate of oxygen consumption ensures normal function. There is less reserve as regards oxygen supply than for any other necessary metabolite or waste product so oxygen supply is flow dependent.

A simple volume related model of arterial blood pressure generation.

A single compartment model of the arterial circulation was used to generate an arterial blood pressure waveform from pre-determined stroke volume (SV) and arterial resistance (R). With fixed stroke volume and varying resistances blood pressure waveforms showed mean values proportional to resistance but amplitude lessening with higher pressure; the amplitude of the hypothetical volume waveform of the arterial system was the same for all resistance values. Where SV varied and R changed reciprocally, the waveform when analysed with the PulseCO algorithm gave estimates slightly higher than the input stroke volumes (r 0.

Oxygen delivery at sea level and altitude (after slow ascent to 5000 meters), at rest and in mild exercise.

Oxygen delivery (DO2) calculated from cardiac output, haematocrit (Hct) and arterial oxygen saturation (SaO2), has been obtained on six subjects at sea level (London) and after slow ascent to 5000 meters (Chamlang base camp) at rest and during mild exercise (25 watts and 50 watts). Haematocrit was increased in all six subjects at 5000 m and expressed as haemoglobin (Hb) rose from a mean (+/- standard error; SEM) of 13.8 +/- 0.

Near infra-red spectroscopy and arterial oxygen extraction at altitude.

The ratio of oxygenated to total haemoglobin (Hb), or rSO2, obtained by near infrared spectroscopy (NIRS), includes both arterial and venous blood of the region examined. The relationship of arterial oxygen extraction, E, and saturation, SaO2, to rSO2 can be expressed, for normally functioning tissue, as E = 1.39 (1 - rSO2/SaO2).

Normal cardiac output, oxygen delivery and oxygen extraction.

The total amount of blood flow circulating through the heart, lungs and all the tissues of the body represents the cardiac output. Most individual tissues determine their own flow in proportion to their metabolic rate. The skin is a notable exception where the priority is thermal rather than metabolic.

Cardiac output, oxygen consumption and muscle oxygen delivery in submaximal exercise. Normal and low O2 states.

Cardiac output (Q) changes linearly with oxygen consumption (VO2) in normal subjects undertaking submaximal exercise (Q = A + B x VO2 where A is the y intercept and B the slope). If (hypothesis 1) the increase in cardiac output above the resting state represents the blood flow to exercising muscle (qm) and the increase in VO2 represents the oxygen consumption of exercising muscle (VO2m) then, where CaO2 is the arterial oxygen content, oxygen extraction, Em = 1/(B x CaO2). Secondly, exercising muscle venous oxygen content, CvO2m = CaO2 - 1/B.

Cardiovascular and respiratory adjustments at altitude sustain cerebral oxygen delivery -- Severinghaus revisited.

Analysis of a paper by Severinghaus et al. (see text) has already shown that sea level oxygen delivery (D(a)O(2)) is sustained 8 h after ascent to 3810 m, despite low arterial oxygen content (C(a)O(2)), largely as a result of increased cerebral blood flow (CBF). The present study extends the analysis to show that D(a)O(2) is also sustained after 3 and 5 days at altitude, despite a progressively falling CBF.