Surgery

• Shock is defined as inadequate tissue perfusion marked by decreased delivery of required metabolic substrate and inadequate removal of cellular waste products.
• Shock involves failure of oxidative metabolism that can involve defects of oxygen (O2) delivery, transport, and/or utilization.
• The initial cellular injury that occurs in shock is reversible; however, the injury will become irreversible if tissue perfusion is prolonged or severe enough such that, at cellular level, compensation is no longer possible.
• Hypovolemic shock is a form of shock caused by fluid loss.
• Traumatic shock is a form of shock caused by physical injury.
• Vasodilatory (septic) shock is a form of shock caused by vasodilation.
• Cardiogenic shock is a form of shock caused by heart disease.
• Obstructive shock is a form of shock caused by an obstruction.
• Neurogenic shock is a form of shock caused by nervous system dysfunction.
• End points in resuscitation are the goals in treating shock.
• Hemorrhagic shock is a form of shock caused by hemorrhage.
• Shock can be classified into different categories based on the underlying etiology.
• Pathophysiology of shock involves tissue hypoperfusion and the developing cellular energy deficit leading to neuroendocrine and inflammatory responses.
• Decreased tissue perfusion can result from hemorrhage, hypovolemia, cardiac failure, or neurologic injury.
• Decreased tissue perfusion and cellular injury can result in immune and inflammatory responses.
• Subclinical Hyperperfusion in ICU is characterized by persistent occult hypoperfusion, which increases infection and mortality.
• The goal of resuscitation is to restore organ perfusion and oxygenation, repaying Oxygen debt, correcting acidosis, and preventing further deterioration.
• Near Infrared Spectroscopy (NIR) is a noninvasive tissue oxygenation measurement that indicates mitochondrial dysfunction and higher organ failure risk.
• Debt Predictors in shock include inability to repay O2 debt and surrogate parameters such as lactate and base deficit.
• Shock is defined as inadequate perfusion causing tissue acidosis and O2 debt.
• Base Deficit measures base needed for pH 7.40 and is linked to deficit magnitude.
• Lactate indirectly measures O2 debt and is a prognostic indicator.
• Resuscitation endpoints include vital signs, cardiac output, pulmonary artery wedge pressure, O2 Delivery, consumption, lactate, and base deficit.
• Left ventricular power output (>320 mmHg·L/min per square meter) associated with improved base deficit clearance and lower organ dysfunction post-injury.
• Compensated Shock is recognized by tissue perfusion inadequacy despite normalized vital signs.
• Right Ventricular End-Diastolic Volume Index (RVEDVI) is better than pulmonary artery wedge pressure for cardiac index prediction and correlates with preload-related cardiac output increase.
• Tissue pH, Oxygen, and Carbon dioxide Concentration are measured by optical sensors and show promise in continuous perfusion assessment.
• Common shock types include Hemorrhagic Shock, Septic Shock, and Traumatic Shock.
• Many of the organ-specific responses aimed at maintaining perfusion in the cerebral and coronary circulation are regulated at multiple levels including stretch receptors and baroreceptors in the heart and vasculature, chemoreceptors, cerebral ischemia responses, release of endogenous vasoconstrictors, shifting of fluid into the intravascular space, renal reabsorption and conservation of salt and water.
• In hypovolemia, the sympatho-adrenal response primarily leads to an increase in heart rate (tachycardia) and peripheral vasoconstriction.
• Recent data in trauma patients suggest that a systolic blood pressure (SBP) of less than 110 mmHg is a clinically relevant definition of hypotension and hypoperfusion based upon an increasing rate of mortality below this pressure.
• Neurogenic shock, resulting from factors like high spinal anesthesia, leads to decreased peripheral vascular resistance.
• Chemoreceptors in the aorta and carotid bodies are sensitive to changes in O2 tension, H+ ion concentration, bicarbonate concentration, and carbon dioxide (CO2) levels.
• Hemorrhage Class IV - Percentage of blood loss is >40% - Manifestations: Confused and lethargic.
• The condition reduces cardiac output due to decreased venous return to the heart.
• Shock due to Carbon Monoxide poisoning is characterized as Vasodilatory Shock.
• A 24-year-old, male arrived in the ER with multiple stab wound with hand trauma, SBP 80, what's the appropriate goal in sustaining at the emergency department.
• A 70 kg male came to the ED following a stab wound to the abdomen, he is hypovolemic, markedly hypotensive, and appears confused, what percent of blood volume has been lost?
• Patients exhibit warm, dry skin, a slower pulse, and hypotension, maintaining normovolemia with preserved urine output.
• While an increase in stroke volume can occur due to increased venous return to the heart, the primary mechanism for increased cardiac output during hypovolemia is an elevated heart rate rather than an increase in stroke volume.