- StatPearls [BOOK]
- BOOKStatPearls Publishing: Treasure Island (FL)
- Orthostasis, from the Greek orthos (upright) and histanai (to stand), is a normal physiological response of the sympathetic system to counteract a fall in blood pressure when a person is laying down ...
Orthostasis, from the Greek orthos (upright) and histanai (to stand), is a normal physiological response of the sympathetic system to counteract a fall in blood pressure when a person is laying down and assumes the upright position. This compensatory response of the autonomic nervous system reveals the evolutionary adaptation of the human being to meet the needs of an erect posture, a unique characteristic that distinguishes humans from other species. Physiology When one stands up, gravity causes a shift of 500 to 800 mL of blood volume from the upper body to the lower body and the splanchnic circulation. This redistribution of blood decreases the venous return and the right atrium’s pressure, reducing the stroke volume and eventually a fall in arterial blood pressure. For this change in position, the body has 4 compensatory mechanisms: Irregular distribution of blood in the venous system (there are pools of blood located in the central circulation, that can be used when hypotension is detected). Non-uniform distensibility (small vessels are more rigid than large vessels. Thus, small veins prevent a large accumulation of blood in the lower body and help to maintain a relative upward flow of blood). Muscle pumps (increase the venous return). Autonomic reflexes. Out of these, autonomic reflexes are the most important mechanism. There are baroreceptors in the carotid sinus and in the aortic arch which play an important role in regulating blood pressure by sensing the grade of distension of the vessels. When there is a fall in blood pressure, tension on the vessel walls decreases and the afferent baroreceptor nerves decrease their firing rate to the medullary cardiovascular center (nucleus tractus solitarii in the medulla). This synapsis will inhibit the parasympathetic response (vagal) and stimulate the sympathetic response, causing generalized vasoconstriction, increased heart rate, and contractility. Baroreceptor activation also causes the activation of the renin-angiotensin-aldosterone system and the release of vasopressin by the pituitary gland. It results in sodium and water reabsorption by the kidney, increasing the plasma volume, and arterial vasoconstriction through angiotensin II type 1 receptor and V1 receptors in arterial blood vessels. Normally, an adequate response increases heart rate by 10 to 15 bpm, maintains the systolic pressure and elevates the diastolic pressure about 10 mm Hg. Pulmonary baroreceptors and atrial low-pressure baroreceptors play a small response, causing renal vasoconstriction the last one, with no significant contribution to increasing the blood pressure. Clinical Relevance When the autonomic compensatory mechanism is affected, there is a significant decrease of the central blood pressure, and symptoms of hypoperfusion can appear, e.g., dizziness, lightheadedness or syncope. This is called orthostatic hypotension. Orthostatic hypotension (OH) is a clinical finding defined by a fall in systolic blood pressure over 20 mmHg or a fall of in diastolic pressure over 10 mm Hg within 3 minutes of standing. Symptoms may be present, or it can be asymptomatic as well.
- StatPearls [BOOK]
- BOOKStatPearls Publishing: Treasure Island (FL)
- The establishment of venous access is essential to the treatment and resuscitation of both the medically and traumatically ill patient. Adequate venous access allows the delivery of fluids, blood pr...
The establishment of venous access is essential to the treatment and resuscitation of both the medically and traumatically ill patient. Adequate venous access allows the delivery of fluids, blood products, medications, and repeated blood draws. The venous cutdown technique is a surgical procedure to gain venous access when relatively less invasive percutaneous procedures such as the Seldinger technique (percutaneous access), ultrasound-guided venous access, and intraosseous vascular access have failed. Percutaneous access can be difficult to achieve in certain patient populations (pediatric patients with small and nonpalpable veins, patients in hypovolemic shock with collapsed veins, patients with peripheral vascular disease with altered vascular anatomy) making venous cutdown a useful alternative in an acute setting.
- Intradialytic Hypotension: Is Midodrine the Answer? [Editorial]
- AJAm J Nephrol 2018 Nov 13; 48(5):378-380
- The Impact of Midodrine on Outcomes in Patients with Intradialytic Hypotension. [Journal Article]
- AJAm J Nephrol 2018 Nov 13; 48(5):381-388
- CONCLUSIONS: Although residual confounding may have influenced the results, the associations observed here are not consistent with a potent beneficial effect of midodrine with respect to either clinical or hemodynamic outcomes.
- The link between social context-dependent anxious behavior and habenular mast cells in fear-conditioned rats. [Journal Article]
- BBBehav Brain Res 2018 Nov 10
- Affiliative social behavior relieves the physiological reactivity to stressors, while social inequity, represented by unfairness in the social environment, causes emotional distress in animals. Mast ...
Affiliative social behavior relieves the physiological reactivity to stressors, while social inequity, represented by unfairness in the social environment, causes emotional distress in animals. Mast cells are immune cells found in the brain that affect both the nervous system and emotional behavior. To determine the role of neuro-immunity in the programming of emotional behaviors, we observed brain mast cells and anxiety-like behaviors in female rats exposed to electrical foot shocks in different social environments. The following groups of rats were used in this study: control (unshocked) rats, solitarily shock-exposed rats, and shock-exposed rats in the presence of unshocked (unequal) or shocked (equal) conspecifics. An absence of significant difference in body weight or sucrose preference was seen among the different groups. Additionally, fear memory was augmented in rats shocked in the presence of either unshocked or shocked conspecifics than rats in the solitarily shocked group. Furthermore, rats shocked in the presence of unshocked conspecifics showed intensified anxiety-like behaviors after fear conditioning. Finally, we found an increase in the number of habenular mast cells in the intensified anxiogenic group, which had a significant correlation with the decreasing rate of anxiety-like behaviors. This provides evidence that habenular mast cells might be of importance in relieving the amplified biopsychological responses caused by social stress.
- Cytotoxicity and global transcriptional responses induced by zinc oxide nanoparticles NM 110 in PMA-differentiated THP-1 cells. [Journal Article]
- TLToxicol Lett 2018 Nov 10
- Despite a wide production and use of zinc oxide nanoparticles (ZnONP), their toxicological study is only of limited number and their impact at a molecular level is seldom addressed. Thus, we have use...
Despite a wide production and use of zinc oxide nanoparticles (ZnONP), their toxicological study is only of limited number and their impact at a molecular level is seldom addressed. Thus, we have used, as a model, zinc oxide nanoparticle NM110 (ZnO110NP) exposure to PMA-differentiated THP-1 macrophages. The cell viability was studied at the cellular level using WST-1, LDH and Alamar Blue® assays, as well as at the molecular level by transcriptomic analysis. Exposure of cells to ZnO110NP for 24 h decreased their viability in a dose-dependent manner with mean inhibitory concentrations (IC50) of 8.1 µg/mL. Transcriptomic study of cells exposed to two concentrations of ZnO110NP: IC50 and a quarter of it (IC50/4) for 4 h showed that the expressions of genes involved in metal metabolism are perturbed. In addition, expression of genes acting in transcription regulation and DNA binding, as well as clusters of genes related to protein synthesis and structure were altered. It has to be noted that the expressions of metallothioneins genes (MT1, MT2) and genes of heat-shock proteins genes (HSP) were strongly upregulated for both conditions. These genes might be used as an early marker of exposition to ZnONP. On the contrary, at IC50 exposure, modifications of gene expression involved in inflammation, apoptosis and mitochondrial suffering were noted indicating a less specific cellular response. Overall, this study brings a resource of transcriptional data for ZnONP toxicity for further mechanistic studies.
- Effects of Simulated Heat Wave and Ozone on High Fat Diet ApoE Deficient Mice. [Journal Article]
- BEBiomed Environ Sci 2018; 31(10):757-768
- CONCLUSIONS: A short-term exposure to a heat wave and ozone causes severe toxic effects on the heart. Cardiac damage was most significant under combined heat wave and severe ozone exposure simulations.
- Mild Allergic Transfusion Reactions: Impact of Associated Clinical Symptoms? [Journal Article]
- AJAm J Clin Pathol 2018 Nov 13
- CONCLUSIONS: Understanding symptoms associated with mild ATRs may lead to improved management of patients, with fewer unnecessary transfusions and less wastage.
- What's New in Shock, December 2018? [Journal Article]
- SShock 2018; 50(6):613-615
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- Envenomation by the common European adder (Vipera berus): a case series of 219 patients. [Journal Article]
- EJEur J Emerg Med 2018 Nov 12
- CONCLUSIONS: Most patients only showed symptoms of no or mild envenomation. Fifteen percent were transferred to the ICU and five patients (all children) required fasciotomy because of suspected compartment syndrome. Only 10 patients received antivenom.