Omar Touzani, Eric T. MacKenzie, in Neurology and Clinical NeuroscienceCerebral Autoregulation Autoregulation of blood flow is a regulatory mechanism that allows blood flow in a vascular bed to remain relatively constant during variations of arterial pressure. This is particularly well developed in the brain and plays an important protective role against the danger of hypoxia at low perfusion pressure and the risk of brain edema at higher arterial pressure.
Understanding renal blood flow and autoregulation Clinical relevance of understanding renal blood flow and autoregulation When faced with a patient suspected of having, or proven to have AKI, intrinsic renal disease and obstruction should always be excluded. The essence of these cases is reduction of the pressure within the glomerular capillaries that drives filtration, management focusing on restoring this pressure.
Even when the insult is toxic or due to urinary tract obstruction, the vascular reflexes that preserve the filtration pressure in the kidneys may still be important.
The most important assessments highlighted by this report were assessment of volume status, assessment of comorbidity and nephrotoxic medications. The importance of these contributory factors is understandable in terms of their impact on the blood supply to and therefore pressure within the glomerular blood vessels.
The assessment is in many respects a search for factors that may compromise glomerular perfusion pressure. Learning Point The kidneys are able to protect themselves using autoregulatory reflexes.
These are inhibited by certain medications. In situations where incoming pressure is reduced e. If reduction of inflow is moderate, GFR may be maintained in the normal range by these mechanisms, albeit reduced compared to the normal GFR in this patient.
Thus, serum creatinine concentration may rise, but only moderately and such reductions in GFR should be considered entirely recoverable with appropriate intervention.
However, autoregulation may not be able to compensate for more severe challenges to glomerular perfusion and a more significant decline in GFR will be seen with more serious biochemical disturbance. This may still be recoverable, but at this stage the chances of recovery to baseline renal function are reduced.
Furthermore, the autoregulatory mechanisms become essential to maintain safe renal function and prevent irreversible damage. These medications therefore severely restrict the ability of the autoregulatory reflexes to maintain kidney function when renal blood flow is reduced.
From this it can be seen that management of AKI requires treatment of any underlying condition that reduces the incoming perfusion pressure whilst ensuring autoregulation is not compromised by NSAIDs including COX-2 inhibitors or drugs blocking the local renin-angiotensin system.
If the filtration barrier is damaged e.
The majority of cases of AKI are due to vascular injuries to the kidney Glomerular filtration rate is maintained by a complex system of autoregulation This autoregulation aims to maintain the glomerular perfusion pressure The autoregulation at the level of the glomerulus relies on controlling the resistance in the incoming afferent and outgoing efferent arterioles Prostaglandins regulate the afferent and Angiotensin ll regulates the efferent arterioles Drugs that affect these autoregulators can contribute to AKI risk e.An abrupt or rapid decline in renal function as evidenced by a rapid rise in serum creatinine or decrease in urine output..
Creatinine clearance or filtration is dependent on the glomerular filtration rate (GFR). The driving force for the GFR is the gradient from the glomerulus to the Bowman space. INTRODUCTION. Renal artery stenosis is a relatively common finding in older patients with hypertension.
However, renal artery stenosis is the primary cause of hypertension (ie, renovascular hypertension) only in certain settings. Sep 17, · The importance of personalized blood pressure management is well recognized.
Because renal pressure–flow relationships may vary among patients, understanding how renal autoregulation may influence blood pressure control is essential.
However, much remains uncertain regarding the determinants of renal autoregulation . Renal autoregulation involves feedback mechanisms intrinsic to the kidney that cause either dilation or constriction in the afferent arteriole so as to counteract blood pressure changes and keep a steady GFR.
For instance, if the mean arterial pressure increases, renal autoregulation causes the afferent arteriole to constrict, preventing the pressure .
Jul 18, · Perinatal asphyxia, more appropriately known as hypoxic-ischemic encephalopathy (HIE), is characterized by clinical and laboratory evidence of acute or .
Renal Autoregulation Myogenic Mechanism The Myogenic Mechanism: The myogenic mechanism is a common property of vascular smooth muscle (myogenic means “muscle produced”).
Arteriolar vascular smooth muscle contract inherently in response to the stretch accompanying increased pressure within the vessel.