1. Hello everyone!
This is a study guide discussing the teaching points regarding the clinical case assigned to you.
We have linked Youtube videos throughout that we feel are helpful. This includes teaching
points associated with the vital signs, chief complaint (which is the reason they came to the
doctor), and HPI (history of present illness aka more information about the chief complaint). We
hope this study guide helps you learn the material.
How low blood pressure leads to high pulse rate in reflex tachycardia, how hypotension is
caused by low blood volume (hypovolemic shock), low cardiac output (cardiogenic shock), or
low arterial tone (distributive shock), and how they are evaluated.
1. Hypotension
a. Definition: Systolic BP less than <90 mmHg
i. Normal systolic BP is 120 mmHg
b. Relative hypotension: Drop in systolic blood pressure >40 mmHg from a patient's
baseline
i. What is baseline? What the patient normally measures
c. Causes
i. Low Blood Volume
ii. Reduced Cardiac Output
iii. Reduced Arterial Tone
2. The baroreflex
a. Low blood pressure leads to high pulse rate in reflex tachycardia
b. When low blood pressure is sensed by baroreceptors in the carotid sinus, the
sympathetic nervous system is activated. Increased sympathetic outflowcauses
release of catecholamines, such as epinephrine, that lead to an increased heart
rate.
i. Exception: Patients taking beta-blocking medications such as metoprolol.
These block sympathetic catecholamines and blunt the reflex tachycardia
that occurs when blood pressure drops
c. A video that explains the concept:
https://www.youtube.com/watch?v=pj1VkA9m0-w
d. A negative feedback system responsible for regulation of arterial blood pressure
(minute to minute)
e. Baroreceptors are located in the in the walls of the carotid sinus at the location
that the common carotid arteries divides. The baroreceptors sense stretch.
2. i.
f. Steps of the baroreceptor reflex:
i. Decrease in arterial pressure sensed in the carotid sinus
ii. Decrease in stretch is sensed by the receptors which sends this
information to the vasomotor center in the brain stem
iii. The vasomotor center has a “set point” for mean arterial pressure,
typically about 100 mm Hg. If a pressure that is not within this set point is
sensed, the autonomic nervous system responds in attempt to get the
mean arterial pressure closer to the set point.
iv. The response of the vasomotor center will increase the heart rate in
attempt to increase arterial pressure back to normal.
3. Hypotension/Hypovolemic shock
a. If you have a LOW BLOOD VOLUME there is less pressure put on the vessels
by the blood
i. Picture a water hose with only a little bit of water flowing through it as
opposed to a lot of water flowing through it
ii. Causes: bleeding, diarrhea, vomiting, diuresis (excessive urination),
reduced oral intake
b. Clinical Findings:
i. Dry mucous membranes
3. 1.
ii. Delayed capillary refill
1. How to test capillary refill: https://youtu.be/U-oSBEx6ZSM
iii. Orthostasis
1. How to measure orthostatic blood pressure:
https://youtu.be/QZj0EmFV2to
c. Khan Academy: https://www.khanacademy.org/science/health-and-
medicine/circulatory-system-diseases/shock/v/hypovolemic-shock
4. Cardiogenic shock
a. Caused by REDUCED CARDIAC OUTPUT
i. What is cardiac output?
1. The amount of blood the heart pumps through the circulatory
system in one minute
2. Typically determined by the heart rate aka beats per minute
ii. Causes: Congestive heart failure, valvular heart disease
iii. Clinical findings
1. A diastolic murmur suggests aortic insufficiency that can cause
cardiogenic shock.
2. A systolic murmur would be present if cardiogenic shock were
caused by aortic stenosis.
3. S3 gallop would be audible of cardiogenic shock were due to
ischemic or dilated cardiomyopathy.
4. Crackles on lung exam. Left-sided heart failure in cardiogenic
shock causes pulmonary edema.
5. Peripheral edema might be seen if right-sided heart failure is
present.
4. a.
b. Khan academy: https://www.khanacademy.org/science/health-and-
medicine/circulatory-system-diseases/shock/v/cardiogenic-shock
5. Distributive shock:
a. Caused by excessive vasodilation aka REDUCED ARTERIAL TONE
i. Vasodilation is the increase in diameter of the blood vessels
ii. Vasodilation will cause decreased tissue perfusion, meaning that the
body will receive less blood and therefore less oxygen
b. Common causes:
i. Sepsis
ii. Systemic inflammatory release syndrome (SIRS)
iii. Anaphylaxis
iv. Antihypertensive medicines
c. Clinical Findings:
i. Normal capillary refill and moist mucous membranes (this is normal)
ii. Orthostasis
d. Video: https://youtu.be/A99y0B8jnRA
How underweight, normal weight, overweight, and obesity are calculated via BMI. The pro’s and
con’s of using body mass and surface area to calculate BMI.
● BMI: is a measure of body fat based on height and weight
○ How to calculate via body mass:
5. ■
○ An example of calculation:
■
■ courtesy of: https://www.youtube.com/watch?v=gIZT0Ew0ugU
● This is a good video if more explanation is needed!
○ Once BMI is calculated, you can determine what is normal or not:
○ Underweight vs. normal weight vs. overweight
○
6. ■
● BMI vs Body Surface Area (BSA)
○ BSA: measures the total surface area of the body and is used to calculate drug
dosages and medical indicators or assessments
■ Ex: cytotoxic anticancer agents and other therapeutic cancer drugs like
monoclonal antibodies
● Takes into account the variability in size of patients and fat tissue
to optimize the positive effects of the drug for the patient
○ Calculated via the Mosteller formula
■
○ BMI vs. BSA - which one is “better”?
■
BMI: measures how much a
person is over/underweight
BSA: measures the total surface
area of the body to calculate drug
dosages, etc.
PROS CONS PROS CONS
Easy to Can Used widely Equation has
7. measure and
calculate
over/underestim
ate a person’s
body fat
Ex: athlete -
overestimate;
elderly -
underestimate
throughout
medicine
(see above)
not been
validated
More accurate
estimate of total
body fat than
weight alone
May require a
waist
circumference
for
supplemental
information
Also used to
provide precise
measurements
of other
cardiology
measurements
Can assess risk
of other health
issues (high
blood pressure,
diabetes, etc)
Citation: https://www.nursingcenter.com/ncblog/august-2017/body-
mass-index-and-body-surface-area-what-s-the-d (good site for
examples)
More probable differential diagnosis of pregnancy, urosepsis, acute hyperglycemia,
gastroenteritis, and adrenal insufficiency, which fit the patient’s low blood pressure, high pulse
rate, diarrhea, nausea, vomiting, and excessive thirst/urination. Less probable differential
diagnosis of anaphylaxis, hypothyroidism, pancreatitis, and congestive heart failure.
Alec and Gretchen
1. Symptoms of patient: low blood pressure, high pulse rate, diarrhea, nausea, vomiting,
and excessive thirst/urination
2. Differential Diagnosis
a. Pregnancy
i. What makes this diagnosis likely?
1. Decrease in blood pressure due to systemic vasodilation
2. Nausea (especially in first trimester), vomiting
3. Increased frequency of urination without dysuria, especially in first
trimester due to the pressure of the growing uterus on the bladder
ii. What makes this diagnosis less likely?
1. Pregnancy rarely causes diarrhea, blurred vision, or polydipsia
(increased thirst)
8. 2. Patients last menstrual period was 4 weeks ago- they may have a
period in the upcoming week
3. We have no information on her sexual history
iii. What tests are there for this diagnosis?
1. Human chorionic gonadotropin (hCG)
a. Produced by the placenta of pregnant women
b. Can be measured in the urine (over the counter pregnancy
test)
c. Can be measured in the blood (done at doctor’s office)
b. Urosepsis
i. What is sepsis?
1. Sepsis is a clinical syndrome that has physiologic, biologic, and
biochemical abnormalities caused by a dysregulated inflammatory
response to infection. Sepsis and the inflammatory response that
ensues can lead to multiple organ dysfunction syndrome and
death
a. Source: Up To Date
ii. Urosepsis: the source of sepsis is localized to the urinary tract
1. Urosepsis is a severe infection, distinguishing it from other urinary
tract infections including mild pyelonephritis (Inflammation of the
kidney due to a bacterial infection)
iii. What makes this diagnosis likely?
1. Excessive urination/frequency,high pulse rate (sepsis symptom),
low blood pressure (sepsis symptom)
a. AKA polyuria, tachycardia, hypotension
iv. What makes this diagnosis unlikely?
1. Nausea and vomiting not likely seen
2. No pain while urination, no fever, no flank pain-- you would expect
this in urosepsis
c. Acute hyperglycemia
i. What is acute hyperglycemia?
1. Acute (short onset) hyper (too much) glycemia (blood sugar). It is
often caused by underlying diabetes mellitus, where the body
doesn’t metabolize sugar correctly due to low levels or responses
to insulin, a hormone.
2. Chronic hyperglycemia can worsen acutely with volumeloss (for
example, following an episode of acute gastroenteritis AKA short
onset diarrhea and vomiting)
ii. What makes this diagnosis likely?
1. Excessive thirst, increased urination (classic hyperglycemic
symptoms due to sugar in urine). When a patient is complaining of
being thirsty all the time and urinating frequently, hyperglycemia
should jump to the top of the differential.
9. 2. Nausea and vomiting (build up of ketones created by metabolizing
fats instead of sugars)
3. Obesity and family history
4. May cause blurry vision
iii. What tests exist for this diagnosis?
1. Presence of glucose in urine
2. A1C elevations (blood measurement of long term sugar levels)
3. Fasting blood sugar elevation (short term sugar levels)
d. Gastroenteritis
i. What is gastroenteritis?
1. Inflammation of stomach and intestines
ii. What makes this diagnosis likely?
1. Nausea, vomiting, diarrhea
2. Loss of volume causing hypotension, tachycardia, and dizziness
iii. What makes this diagnosis less likely?
1. Blurred vision and polyuria not commonly seen
e. Adrenal insufficiency
i. What is adrenal insufficiency?
1. Adrenal insufficiency (Addison’s disease) is when the adrenal
glands that sit on top of the kidneys aren’t producing enough of
the hormones that they usually make.
3. Less probable differential diagnosis
a. Anaphylaxis
i. Patient could present with low blood pressure and increased heart rate
ii. Trouble breathing due to bronchospasm is usually a symptom (not
present in this patient)
iii. Presentation is always rapid (minutes to hours) as opposed to this patient
who developed symptoms over days
iv. Does not explain other symptoms such as thirst and urination
b. Hypothyroidism
i. Usually presents as severe fatigue with weight gain
ii. Other major symptoms include dry skin and hair, and intolerance to cold
temperatures
iii. Does not explain other symptoms such as thirst and urination
c. Pancreatitis
i. Could be causing the nausea and vomiting
ii. Usually also has abdominal pain
iii. Does not explain other symptoms such as thirst and urination
d. Congestive heart failure
i. Can cause blood pressure decrease and increase in heart rate
ii. Does not explain other symptoms such as thirst and urination
iii. Much more common in older patient population (60+)
4. What should be at the top of your differential diagnosis right now? AKA what fits the
patients symptoms most accurately?
10. a. ACUTE HYPERGLYCEMIA
b. In the next module, we will discuss the physical exam and lab values-- confirming
or disproving the differential diagnosis
