Mean arterial pressure (MAP) <65. Keep in mind that a patient who is usually hypertensive can experience hypoperfusion at higher MAPs.

• Remember hypotension = death. Presence of normal mentation simply indicates that the patient still has a pulse and should not be reassuring in itself.
• Treat all episodes of hypotension very seriously; all hypotensive patients should be seen and evaluated promptly.
• Use this equation to think through the differential diagnosis of hypotension:
  MAP = SVR x CO = SVR x HR x SV

Decreased SVR (warm extremities, flushing)

• Sepsis
• Medication overdose/error
• Adrenal insufficiency
• Anaphylaxis
• Neurogenic

</WRAP> | <WRAP> Decreased preload (cool extremities)

• Hypovolemia: bleed, diarrhea, third spacing, insensible losses
• Pulm: PE, tension PTX
• Cardiac: tamponade, RV infarct, pulmonary HTN

</WRAP> |

Decreased contractility

• Myocardial dysfunction (CAD/CHF)
• Medications (beta blockers, CCB)
• Valvular dysfunction (AS, AI, MR)
• Aortic dissection

</WRAP> | <WRAP> Abnormal heart rate

• Very tachycardic
• Very bradycardic

</WRAP> |

• Decreased SVR: Exam = warm extremities, sometimes flushing.
  • Sepsis: Common cause. Obtain blood cultures x 2, CXR, UA/micro/culture. Rapid administration of IVF and antibiotics will be crucial. See Critical Care: early goal-directed therapy for sepsis.
  • Medications: Look for antihypertensives, pain meds, sedatives, illicit drugs, and possible dosage errors; if concern for opiate overdose, give narcan.
  • Adrenal insufficiency: Is the patient on chronic steroids and unable to mount a stress response? Consider stress dose steroids (See Endocrine: Adrenal Insufficiency).
  • Anaphylaxis: Look at medication list/diet for offending agent. Give epinephrine 0.2-0.5 ml (0.2-0.5 mg) of 1:1000 SC/IM q20 minutes (diluted dose—different from “code blue” dose), diphenhydramine 50 mg IV, hydrocortisone 100 mg IV.
  • Neurogenic: “Spinal shock” rare cause in an already hospitalized patient. Spinal compression. Treatment is epinephrine.

• Decreased preload: Exam = cool extremities, variable JVP)
  • Hypovolemia: bleed, diarrhea, third spacing, insensible losses. Get STAT CBC, consider Central Venous Pressue (CVP) monitoring, review Ins and Outs. Increase preload by putting the patient in Trendelenberg, giving IVF bolus (almost never wrong, though check if the patient has known ventricular dysfunction).
  • Pulmonary embolism: See Pulmonary: Pulmonary Embolism.
  • Tension pneumothorax (PTX): Unequal breath sounds on exam. Do not wait for a CXR. Insert a 14 or 16-gauge needle into the second intercostal space at the midclavicular line ASAP.
  • Tamponade: Remember Beck’s triad: elevated JVP, muffled heart sounds, and hypotension. Get pulsus, call cardiology to perform an echo and pericardiocentesis. See Cardiology: Tamponade.
  • Right ventricular infarct: Obtain right-sided ECG. See Cardiology: RV Myocardial Infarction.
  • Pulmonary hypertension: See Cardiology: Pulmonary Hypertension.

• Decreased contractility: Exam = listen for gallop, murmurs (especially new), and rales/crackles.
  • Myocardial dysfunction: New infarct vs. prior ventricular dysfunction and precipitating event. Review history of CAD/CHF and cardiac risk factors. Get STAT ECG, cycle troponins, telemetry; see Cardiology: Rule out Myocardial Infarction, ACS, Congestive Heart Failure.
  • Medications: Look for B-blockers and CCB.
  • Valvular dysfunction (AS, Al, MR): Acute worsening of known valve disease? Infarction causing papillary muscle rupture? Endocarditis? Get STAT echo. Treatment is specific to the valvular abnormality (e.g. afterload reduction with nitroprusside drip for severe MR).
  • Aortic dissection: Any history of peripheral vascular disease? Get STAT chest CT.

• Abnormal heart rate: Look at the ECG for pathologic tachycardia, bradycardia. Unlikely to be primary cause unless HR is very high or very low.
  • Additional Points on Differential Diagnosis and initial evaluation: After using MAP=SVR x CO, consider the following:
    • Overlap syndromes: Get more data with a PA line or echocardiogram + CVP.
      • Sepsis + cardiogenic / sepsis + hypovolemia / cardiogenic + hypovolemia.
    • Consider other causes of hypotension as listed above and as follows:
      • Increased cardiac output without sepsis: ESLD or fulminant hepatic failure, severe pancreatitis, trauma with SIRS, thyroid storm, AV fistula.
      • Increased CVP without LV failure: pulmonary hypertension, PE, RV infarct, tamponade.
      • Non-responsive hypovolemia: adrenal insufficiency, anaphylaxis, cold sepsis.
      • Autonomic dysfunction: review patient’s problem list/past medical history

• Always start with: “Is the patient stable?” and go evaluate the patient promptly:
• Above all, stay calm. Crashing patients are scary. Do not try to manage shock by yourself. Discuss the case with other residents, ICU fellow, etc.
• Have a low threshold to transfer a hypotensive patient to the ICU for better nursing support and/or for facilitated intubation. Call a code blue for immediate help.
• If the BP is undetectable, palpate for pulses. A palpable femoral pulse indicates systolic blood pressure (SBP) > 80 mmHg and a palpable carotid pulse indicates SBP > 60 mmHg.
• Treatment is aimed at the underlying cause (see DDx and evaluation section above), but almost all cases call for fluid resuscitation. If suspicion of CHF is low, then give rapid isotonic fluid resuscitation.
• In general, start O,, additional large bore peripheral IVs, put patient in Trendelenberg, draw basic STAT labs (lactate, CBC, lytes, BUN, creatinine, glucose, LFT's, blood/urine cultures), and get STAT ECG, CXR, ABG.
• See Critical Care sections (e.g., Initial Choice of vasopressor in hypotension, Stepwise Approach to the ICU patient with septic shock) for more information.
• If the patient is stable, then move on to these questions:
  • Is this BP real? Measure the BP manually with the correct sized cuff. Get a repeat full set of vitals.
  • Is the BP any different from prior values? If the patient usually has a BP of 80/40 mmHg, then the acuity
  • y be decreased somewhat.
  • Is there associated hypoxemia, altered mental status, or increased respiratory rate (reasons for intubation)?
  • Access? Think about placing additional large bore peripheral IVs, a central line, or a PA line.
  • Monitoring? Arterial line placement gives real time accurate blood pressure measurements. Foley catheter to measure urine output (renal perfusion).
  • Is the mean arterial pressure (MAP) < 60 mmHg? MAP = (SBP + 2(DBP))/3. MAP less than 60 mmHg = significant risk of hypoperfusion to vital organs.