- 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.
- 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.
- Scurvy-Characteristic Features and Forensic Issues. [Journal Article]
- AJAm J Forensic Med Pathol 2018 Nov 12
- Scurvy is a multisystem condition that arises from vitamin C deficiency. As humans cannot synthesize vitamin C, serum and tissue levels depend on bioavailability, utilization, and renal excretion. De...
Scurvy is a multisystem condition that arises from vitamin C deficiency. As humans cannot synthesize vitamin C, serum and tissue levels depend on bioavailability, utilization, and renal excretion. Deficiencies result in defective collagen formation with swelling of gums, leg ulceration, and bleeding manifestations. Death most often results from infection and hemorrhage. In a forensic context, scurvy may mimic inflicted injuries and may be responsible for sudden death by mechanisms that remain unclear. Cardiac failure and rhythm disturbances with chest pain, hypotension, cardiac tamponade, and dyspnea are associated with vitamin C deficiency. In addition, syncope and seizures may occur. Although far less common than in previous centuries, scurvy is still present in high-risk populations that include alcoholics, isolated elderly individuals, food faddists, institutionalized patients, those with mental illness, and those who have had bariatric surgery or with underlying gastrointestinal conditions. Scurvy should therefore be a diagnosis to consider in medicolegal cases of apparent trauma and sudden death.
- Recent Advances in Short QT Syndrome. [Review]
- FCFront Cardiovasc Med 2018; 5:149
- Short QT syndrome is a highly malignant inherited cardiac disease characterized by ventricular tachyarrhythmias leading to syncope and sudden cardiac death. It is responsible of lethal episodes in yo...
Short QT syndrome is a highly malignant inherited cardiac disease characterized by ventricular tachyarrhythmias leading to syncope and sudden cardiac death. It is responsible of lethal episodes in young people, mainly infants. International guidelines establish diagnostic criteria with the presence of a QTc ≤ 340 ms in the electrocardiogram despite clinical diagnostic values remain controversial. In last years, clinical diagnosis, risk stratification as well as preventive therapies have been improved due to identification of pathophysiological mechanisms. The only effective option is implantation of a defibrillator despite Quinidine may be at times an effective option. Currently, a limited number of rare variants have been identified in seven genes, which account for nearly 20-30% of families. However, some of these variants are associated with phenotypes showing a shorter QT interval but no conclusive diagnosis of Short QT syndrome. Therefore, an exhaustive interpretation of each variant and a close genotype-phenotype correlation is necessary before clinical translation. Here, we review the main clinical and genetic hallmarks of this rare entity.
- Wide Complex Tachycardia and Syncope in a Middle-Aged Woman. [Journal Article]
- JCJAMA Cardiol 2018 Nov 07
- External 30 Days Holter Usefulness in Unexplained Syncope, Palpitations and Cardioembolic Suspected Cryptogenic Stroke Study. [Journal Article]
- ECEur Cardiol 2017; 12(2):101
- [Transient loss of consciousness : Algorithm for the (differential) diagnosis of syncope at emergency department]. [Review]
- MKMed Klin Intensivmed Notfmed 2018 Nov 09
- Transient loss of consciousness (TLoC) is a common complaint leading to presentation at the emergency department. This comprises a heterogeneous group of disorders including cerebral events, metaboli...
Transient loss of consciousness (TLoC) is a common complaint leading to presentation at the emergency department. This comprises a heterogeneous group of disorders including cerebral events, metabolic disturbances, intoxication, psychogenic patterns or any form of syncope. While many causes are benign and self-limited not requiring extensive in-hospital evaluation, others are potentially severe. The optimal evaluation of patients with TLoC/syncope follows a risk-adapted diagnostic algorithm in order to exclude life-threatening conditions and to identify those with high risk for further deterioration like structural heart diseases requiring further diagnostic evaluation. Low-risk patients can be discharged without further extensive diagnostic work up. This article presents an algorithm for structured, evidence-based care of the syncope patient in accordance with the recently launched "2018 ESC guidelines for the diagnosis and management of syncope" in order to ensure that patients requiring hospitalization are managed appropriately and those with benign causes are discharged safely. The English version of this algorithm is available at the end of the article under "Supplementary Material".
- Early mobilisation by head-up tilt with stepping versus standard care after severe traumatic brain injury - Protocol for a randomised clinical feasibility trial. [Journal Article]
- TTrials 2018 Nov 08; 19(1):612
- CONCLUSIONS: Our findings will inform a future, larger-scale randomised clinical trial on early mobilisation using a tilt table early after severe traumatic brain injury.
- Lithium intoxication presenting as altered consciousness and arrhythmia with cardiogenic shock: A case report. [Journal Article]
- MMedicine (Baltimore) 2018; 97(45):e13129
- CONCLUSIONS: If an emergency physician encounters a patient with altered consciousness and arrhythmia with cardiogenic shock, the patient's drug intake history should be carefully reviewed to rule out cardiovascular problems on the basis of the patient's clinical condition.
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- Routine coagulation test abnormalities caused by rivaroxaban: A case report. [Journal Article]
- MMedicine (Baltimore) 2018; 97(45):e13104
- CONCLUSIONS: This case indicates that in real-world situations, a small number of patients may develop changes in both PT and aPTT during rivaroxaban therapy. Therefore, coagulation monitoring should be considered in patients with risk factors for bleeding, such as elderly patients with renal insufficiency.