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Hypoperfusion of vital organs associated with hypotension. Shock is a medical emergency. Classification: 1) distributive shock (generalized systemic vasodilation) - septic shock 2) cardiogenic shock (low cardiac output due to left-sided heart failure or right-sided heart failure 3) hypovolemic shock (loss of preload) 4) obstructive shock (massive increase in afterload) - cardiac tamponade, pulmonary embolism, tension pneumothorax 5) anaphylactic shock Pathology: 1) hypoperfusion of vital organs with tissue hypoxia 2) acidemia 3) distributive shock (generalized systemic vasodilation) - high cardiac output, low systemic vascular resistance 4) cardiogenic shock (left-sided heart failure or right-sided heart failure) - low cardiac output, high PCWP, high systemic vascular resistance 5) hypovolemic shock (loss of preload) - low cardiac output, low PCWP, high systemic vascular resistance 6) obstructive shock (massive increase in afterload) - low cardiac output, variable PCWP, high systemic vascular resistance - cardiac tamponade, pulmonary embolism, tension pneumothorax 7) anaphylactic shock - high cardiac output, normal PCWP, low systemic vascular resistance Clinical manifestations: 1) onset is typically acute, but may be gradual 2) systemic hypotension 3) tachycardia occurs with: - pain, fever, hypoxia, hyperthyroidism, stress, myocarditis' 4) bradycardia occurs with: - sick sinus syndrome, heart block, increased vagal tone 5) fever - sepsis, anaphylaxis, adrenal insufficiency 6) cool extremities & delayed capillary refill, known as 'cold shock* 7) warm shock manifests as vasodilation with flash capillary refill* 8) jugular venous flattening or distension 9) pulmonary rales with heart failure, ARDS, pneumonia 10) heart sounds a) distant with cardiac tamponade b) loud P2 with pulmonary hypertension c) delayed A2 with aortic stenosis d) S3 & diffuse impulse with cardiogenic shock e) S4 & prominent impulse with obstructive shock f) murmurs 1] mitral regurgitation 2] hypertrophic cardiomyopathy 3] aortic stenosis 4] aortic insufficiency 5] ventricular septal defect g) pericardial rub with pericarditis h) pericardial knock with pericardial constriction i) diastolic plop with myxoma j) muffling of metallic prosthetic valve clicks may occur * it is not clear if these classifications are reserved for pediatric patients Laboratory: 1) complete blood count (CBC) a) hematocrit drops after hydration with acute blood loss b) hemoconcentration with dehydration c) leukocytosis, left shift & toxic granulation suggests sepsis d) thrombocytopenia may be seen with bleeding diatheses e) schistocytes may be seen with DIC 2) coagulation studies a) prothrombin time b) partial thromboplastin time c) D-dimer or other fibrin-split products d) plasma fibrinogen 3) arterial blood gas (ABG) a) acidemia b) hypoxia 4) blood cultures a) aerobic b) anaerobic c) fungal d) acid-fast organisms 5) urinalysis 6) serum chemistries a) electrolytes b) serum Ca+2 c) serum Mg+2 d) serum glucose e) markers of myocardial infarction 1] serum creatine kinase MB (CKMB) 2] serum lactate dehydrogenase 3] serum troponin-I f) serum amylase g) serum lipase h) renal function tests i) liver function test j) serum phosphorus k) serum cortisol 7) drug levels Special laboratory: 1) electrocardiogram 2) echocardiogram a) transthoracic echocardiogram 1] pericardial effusion 2] generalized hypokinesis with cardiomyopathy 3] focal wall motion abnormalities with MI 4] cardiac valve function 5] cardiac output 6] septal defects 7] left ventricular ejection fraction b) transesophageal echocardiogram 1] pulmonary artery thromboembolism 2] aortic dissection 3] cardiac valve function 4] septal defects 5] congenital heart disease 3) cardiac catheterization a) Swan-Ganz (right heart) catheterization 1] pulmonary artery & wedge pressure 2] cardiac output a] thermodilution b] Fick method 3] calculation of systemic vascular resistance 4] pulmonary angiography 5] of no benefit in management of shock [3] b) left heart catheterization 1] coronary artery catheterization 2] left ventriculography 3] aortography Radiology: 1) chest X-ray a) evaluate for cardiomegaly b) progressive enlargement with cardiac tamponade c) evidence of pulmonary congestion d) dilated aortic arch with dissecting aortic aneurysm e) prominent pulmonary vasculature with septal defects f) pulmonary effusions 1] heart failure 2] pulmonary embolism 3] other conditions 2) ventilation perfusion scan for pulmonary embolism Management: 1) hemodynamic stabilization, restore perfusion of vital organs a) intravenous (IV) fluids - avoid hydroxyethyl starch (hetastarch) [5] b) vasopressors 1] epinephrine, dopamine, dobutamine for cardiogenic shock - epinephrine is 1st line therapy for cold shock with hypotension 2] norepinephrine for warm shock & septic shock c) central line to measure central venous pressure (CVP) d) arterial line to measure arterial blood pressure - a mean arterial pressure of 65 mm Hg is the theshold at which there is sufficient pressure for organ perfusion (most humans) e) pulmonary artery catheter for hemodynamic monitoring f) continuous monitoring of: 1] vital signs 2] blood pressure 3] oxygen saturation 4] ECG for arrhythmias g) glucagon: 1 mg in 1 L of D5W at 5-15 mL (5-15 ug)/min for refractory hypotension 2) treatment of underlying pathology [3] 3) consider administration of a) naloxone (Narcan) for opioid overdose b) flumazenil (Romazicon) for benzodiazepine overdose 4) low-calorie, low-protein enteral nutrition may reduce ICU stay in ventilated patients [7] (see intensive care unit)

Related

anaphylaxis

Specific

cardiogenic shock distributive shock; vasodilatory shock (multiple organ dysfunction syndrome) hypovolemic shock obstructive shock

General

hypotension syndrome

References

  1. Manual of Medical Therapeutics, 28th ed, Ewald & McKenzie (eds), Little, Brown & Co, Boston, 1995, pg 135
  2. Saunders Manual of Medical Practice, Rakel (ed), WB Saunders, Philadelphia, 1996, pg 211-214
  3. Medical Knowledge Self Assessment Program (MKSAP) 11, 16, 18, 19. American College of Physicians, Philadelphia 1998, 2012, 2018, 2022.
  4. Harrison's Principles of Internal Medicine, 14th ed. Fauci et al (eds), McGraw-Hill Inc. NY, 1998, pg 214-222
  5. Zarychanski R et al Association of Hydroxyethyl Starch Administration With Mortality and Acute Kidney Injury in Critically Ill Patients Requiring Volume Resuscitation. A Systematic Review and Meta-analysis. JAMA. 2013;309(7):678-688 PMID: 23423413 http://jama.jamanetwork.com/article.aspx?articleid=1653505
  6. Vincent JL, De Backer D. Circulatory shock. N Engl J Med. 2013 Oct 31;369(18):1726-34. PMID: 24171518 Free full text
  7. Reignier J, Plantefeve G, Mira JP et al. Low versus standard calorie and protein feeding in ventilated adults with shock: A randomised, controlled, multicentre, open-label, parallel-group trial (NUTRIREA-3). Lancet Respir Med 2023 Jul; 11:602. PMID: 36958363 Clinical Trial. https://www.thelancet.com/journals/lanres/article/PIIS2213-2600(23)00092-9/fulltext
  8. NEJM knowledge+ Question of the Week https://knowledgeplus.nejm.org/question-of-week/5108/ - Davis AL et al. American College of Critical Care Medicine clinical practice parameters for hemodynamic support of pediatric and neonatal septic shock. Crit Care Med 2017 Jun; 45:1061. PMID: 28817482 - Yager P, Noviski N. Shock. Pediatr Rev 2010 Aug; 31:311. PMID: 20679096 - Mendelson J. Emergency department management of pediatric shock. Emerg Med Clin North Am 2018 May; 36:427. PMID: 29622332 - Bronicki RA et al. Critical heart failure and shock. Pediatr Crit Care Med 2016 Aug; 17:S124