Today, we reviewed a stepwise approach to evaluating an acutely hypotensive patient.
As a reminder, shock is defined as insufficient cardiac output to meet demands. There are three major categories of shock:
1. Distributive =Low total peripheral resistance
Septic
Hepatic failure
Pancreatitis
Anaphylactic shock
Adrenal insufficiency
Neurogenic shock
Arteriovenous shunts
2. Hypovolemic = Low cardiac output due to low intravascular volume
Trauma
Gastrointestinal hemorrhage
Postsurgical, postprocedural bleeding
Intra-abdominal cause (eg, abdominal aortic aneurysm, ruptured ectopic pregnancy)
Vomiting
Diarrhea
Excessive diuresis (from diuretics or uncontrolled diabetes)
3. Cardiogenic = Low cardiac output despite adequate intravascular volume
Poor contractility
Left ventricular failure
Right ventricular failure
Outflow obstruction (i.e. Aortic stenosis or HOCM)
Arrhythmogenic causes
Backflow (i.e. Acute MR, free wall rupture)
Reduced filling (i.e. Constrictive pericarditis, Tension pneumothorax, or severe MS)
While reading through this lecture remember that Cardiac Output (or your blood pressure!) is equal to heart rate times stroke volume and stroke volume is made up of contractility, afterload, and preload!
An approach to the hypotensive patient
Start with a brief history and bedside examination.
Why was the patient admitted?
When did they become hypotensive?
Any significant past medical history or medications?
Get a one-liner from the bedside nurse. You don’t want a full med list or history but it would be important to know if the patient is on a heparin drip, recently had abdominal surgery, was admitted for neutropenic fever, etc.
1. Evaluate your patient's heart rate.
Your goal is to determine if there is abnormal tachycardia or any bradycardia.
If tachycardia is present, is it the CAUSE or the RESPONSE of the hypotension?
Is the HR above 170? Typically HR > 170 starts to affect diastolic filling and can result in hypotension.
NOTE: AFib w/ RVR may result in hypotension at lower HR thresholds!
Otherwise, the HR may just be compensatory for diminished SV.
If bradycardia is present, check for beta blockade. Any HR less than 50 can be the cause of hypotension!
If the patient's heart rate is appropriate, move on to the next step (volume status).
2. Evaluate your patient's volume status.
You can do this via a quick examination or bedside ultrasound if you are comfortable/competent.
Dry mucous membranes?
Sunken eyes?
Abnormal skin turgor (ie tenting when pinched)?
Poor capillary refill (ie > 2 seconds)?
Weak pulse?
Cool extremities?
If hypovolemia is suspected, give IV fluids. Make sure to think about the WHY of hypovolemia so you can treat the underlying cause
If you think the patient is euvolemic to hypervolemic, move on to Step 3: Cardiac Performance.
3. Evaluate your patient's cardiac performance.
Assess myocardial performance by cardiopulmonary physical examination, ECG, and bedside ultrasound (if competent) to assess left ventricular (LV) function.
Cardiogenic Shock (from one of the many causes discussed above) should be high on your differential diagnosis at this point. You could get EKG and consider troponins too if story fits.
Physical exam findings to look for include:
High-pitched holosystolic murmur radiating to axilla?
Diastolic murmur at RUSB radiating to LLSB?
Systolic murmur at RUSB radiating to neck?
Crackles/rales?
Elevated JVP or obvious JVD?
Peripheral edema?
If you think that hypotension is secondary to cardiogenic shock, consider the following:
STAT Cardiology Consult
Treat the cause of the shock: Cardiology and/or ICU fellow can be helpful here
Vasopressors and inotropes can be used to increase SVR, DBP, coronary artery perfusion if decreased LVEF is suspected
If tamponade is suspected, GIVE IV FLUIDS. KEEP BOLUSING.
If you think that the cardiac function is OK based on examination and studies, move on to Step 4: SVR.
4. Assess your patient's Systemic Vascular Resistance.
If 1-3 are OK and your patient is still hypotensive AND displaying signs of shock, something is wrong with the systemic vascular resistance: your patient must be in distributive shock.
The differential can be broad and relies heavily on the situation and patient. Consider the following:
Sepsis
Anaphylaxis
Medication overdose resulting in vasodilation
Neurogenic Shock
Liver Failure
Severe acidosis resulting in vasodilation
Mitochondrial Poisons (cyanide, CO, etc.)
Toxic ingestions
Do a physical examination to try and determine which of the above are going on.
Determine warm versus cold shock!
Send some labs based on your suspected diagnoses
References
McGee, Abernethy, and Simel. “The rational clinical examination. Is this patient hypovolemic?”. JAMA. 1999 Mar 17;281(11):1022-9.
Klabunde, RE. The Pharmacologic Treatment of Hypotension. Cardiovascular Pharmacology Concepts, 2007.
Isnasious and Singh with Koyfman. “The Hypotensive ED Patient: A Sequential Systematic Approach”. 12/29/2014. from eMDocs.com
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