Shock (including Cardiogenic Shock, Hypovolemic Shock, and Septic Shock)

What are the 2 diagnostic hemodynamic thresholds that define a sustained state of systemic shock?

systolic blood pressure less than 90 mmHg, Mean Arterial Pressure less than 65 mmHg

What specific serum metabolic marker and corresponding numerical threshold establishes a biochemical diagnosis of shock and tissue dysoxia?

serum lactate greater than 2.0 mmol/L

List the 2 primary arterial blood gas threshold values that characterize the primary metabolic acidosis seen in circulatory shock.

systemic pH less than 7.35, serum bicarbonate less than 22 mmol/L

What is the exact adult urine output threshold that signifies severe renal hypoperfusion and acute kidney injury during shock?

less than 0.5 mL/kg/hour

In cardiogenic shock, primary pump failure drops stroke volume, leaving a large residual end-systolic volume that drives a retrograde rise in left ventricular end-diastolic, left atrial, and [...] pressures.

pulmonary venous

Acute pulmonary edema occurs in cardiogenic shock because elevated pulmonary venous pressure is transmitted to the capillaries, driving up pulmonary [...] pressure to force fluid transudation into the alveoli.

capillary hydrostatic

In hypovolemic shock, absolute intravascular fluid loss collapses ventricular preload, reducing end-diastolic volume and fiber stretch, which decreases the number of effective [...] cross-bridge cycles.

actin-myosin

In septic shock, bacterial endotoxins trigger a cytokine storm that upregulates inducible nitric oxide synthase; excess nitric oxide activates [...] to inactivate [...], collapsing systemic vascular resistance.

cGMP, myosin light chain kinase

Systemic relative and absolute hypovolemia occurs in septic shock because pro-inflammatory cytokines induce widespread capillary leak by breaking down endothelial [...].

tight junctions

Which 2 prominent clinical features readily distinguish a massive pulmonary embolism causing obstructive shock from primary cardiogenic shock?

completely clear lung fields on auscultation, S1Q3T3 right-heart strain pattern on ECG

Contrast hypovolemic shock from early septic shock based on jugular venous pressure status and initial peripheral skin characteristics.

hypovolemic shock features a flat JVP and immediately cold pale clammy skin, early septic shock features a raised or normal JVP and characteristically warm flushed skin with bounding pulses

List the 4 clinical signs that rapidly distinguish an IgE-mediated anaphylactic shock from septic or hypovolemic shock.

diffuse urticaria, significant angioedema, facial swelling, prominent expiratory wheezing or stridor

List the 3 components of the classic Beck Triad used to differentiate cardiac tamponade from primary cardiogenic shock.

systemic hypotension, raised jugular venous pressure, muffled or distant heart sounds

Which 2 primary diagnostic findings on an ECG and bedside ultrasound establish a definitive diagnosis of cardiac tamponade over cardiogenic shock?

electrical alternans with low-voltage complexes, large pericardial effusion compressing the heart

What is the strict clinical rule regarding the minimum number and collection timing of blood cultures when managing a patient with suspected septic shock?

a minimum of 3 separate blood culture sets must be drawn using strict aseptic technique before the initiation of empiric antibiotic therapy

When using a butterfly collection set to draw blood cultures for suspected septic shock, which bottle must be filled first?

aerobic bottle first to clear air from the collection tubing

What is the definitive first-line bedside imaging modality used to confirm cardiogenic shock, and what 3 primary parameters does it evaluate?

transthoracic echocardiography evaluating global wall motion abnormalities, structural valvular disruptions, and reduced left ventricular ejection fraction

What classic bedside ultrasound visualization of the inferior vena cava confirms a definitive diagnosis of hypovolemic shock?

completely collapsed narrow inferior vena cava with high respiratory variation or kissing walls

What is the strict maximum timeline permitted for administering the first dose of empiric broad-spectrum intravenous antibiotics in suspected septic shock?

within the first 1 hour of recognition

What is the first-line vasopressor class medication indicated in septic shock if systemic blood pressure or MAP remains low despite adequate crystalloid fluid volume resuscitation?

noradrenaline

Why are aggressive crystalloid fluid boluses strictly avoided and contraindicated as a next step in primary cardiogenic shock?

overloading the circulation will rapidly elevate filling pressures and worsen acute pulmonary edema

What specific pharmacological phenomenon causes a continuous Dobutamine infusion to lose therapeutic efficacy over time, and what cellular mechanism drives it?

tachyphylaxis driven by the rapid down-regulation and desensitization of cardiac beta-1 receptors

What is the exact numerical dose threshold and primary physiological action of a low-dose Dopamine infusion?

1 to 5 mcg/kg/min causing selective renal vasodilation via dopaminergic receptors

What is the exact numerical dose threshold and primary physiological action of a medium-dose Dopamine infusion?

5 to 10 mcg/kg/min stimulating beta-1 adrenergic receptors to drive positive inotropy and increase cardiac contractility

What is the numeric dose threshold for high-dose Dopamine, and why does its primary physiological action act as a severe pitfall in cardiogenic shock?

greater than 10 mcg/kg/min, because it stimulates alpha-1 receptors causing intense peripheral vasoconstriction that heavily elevates myocardial oxygen demand

Name the drug class of milrinone and amrinone, and explain how they optimize a patient in short-term cardiogenic shock.

phosphodiesterase-3 inhibitors, they elevate intracellular cAMP to increase myocardial contractility while inducing vascular smooth muscle relaxation to drop left ventricular afterload

Widespread endotoxin activation of the endothelium and tissue factor cascades in septic shock triggers which lethal systemic hematological complication?

disseminated intravascular coagulation

Severe uncorrected renal hypoperfusion during a state of prolonged hypovolemic shock causes which specific parenchymal kidney pathology?

ischemic acute tubular necrosis

Extensive myocardial infarction tissue necrosis can cause a mechanical breakdown of the subvalvular apparatus, clinically presenting as which acute complication?

ischemic rupture of the papillary muscles leading to acute mitral regurgitation

Contrast the statuses of ventricular preload and left ventricular afterload in cardiogenic shock versus hypovolemic shock.

cardiogenic shock features elevated preload and elevated afterload, hypovolemic shock features severely depressed preload and elevated afterload