Updated: 10/27/2017

Cardiac Output and Variables

Topic
Review Topic
0
0
Questions
7
0
0
Evidence
10
0
0
Videos
2
Cardiac Output
  • Cardiac Output (CO) = Stroke Volume (SV) x Heart Rate (HR)
  • Oxygen delivery = CO x arterial oxygen content (CaO2)
  • Fick principle 
    • VO2 = (Ca-Cv) x CO
      • volume of oxygen consumed = tissue extraction of oxygen times CO
    • applies "conservation of mass" concept to oxygen consumption in body
    • CO = O2 consumption / [ (O2 in pulmonary vein) -   (O2 in pulmonary artery) ]
    • Key
      • the equation above refers to difference of oxygen content between the pulmonary vein (oxygenated blood) and pulmonary artery (deoxygenated blood)
      • when dealing with systemic circulation, one has to substract O2 in systemic veins (deoxygenated blood) from O2 in systemic arteries (oxygenated blood) to avoid negative values
  • Changes in CO
    • ↓ SV in ventricular tachycardia
      • if HR is too high, diastolic filling is incomplete and CO decreases
    • exercise 
      • CO maintained by SV in early stages of exercise
      • CO maintained by HR in late stages of exercise

Stroke Volume
  • Stroke Volume (SV) 
    • SV = CO/HR = End-Diastolic Volume (EDV) - End-Systolic Volume (ESV)
    • volume of blood ejected per heart beat
      • SV ~ 70 mL
  • Variables (assessed by echocardiogram)
    • EDV
      • volume of blood in ventricle before ejection
    • ESV
      • volume of blood in ventricle after ejection
  • Changes in SV 
    • SV in anxiety, exercise, pregnancy
    • ↓ SV in failing heart
  • "SV CAP"
    • Stroke Volume affected by Contractility, Afterload, Preload
      • SV via (1) contractility, (2) ↓ afterload, (3) preload
  • Contractility, ↑ SV via
    • catecholamines
      • activity of Ca2+ pump in SR
    • intracellular Ca2+
    • extracellular Na+
      • activity of Na+/Ca2+ exchanger
    • digitalis
      • intracellular Na+ intracellular Ca2+
  • Contractility, ↓ SV via
    • β1 blockade
      • cAMP
    • heart failure
      • systolic dysfunction
    • acidosis
    • hypoxia/hypercapnea
      • PO2/PCO2
    • non-dihydropyridine Ca2+ channel blockers
  • Myocardial O2 demand via
    • afterload (∝ arterial pressure)
    • contractility
    • HR
    • heart size aka wall tension

Ejection Fraction
  • Ejection Fraction (EF) = SV/EDV
    • fraction of EDV ejected per SV
    • an index of ventricular effectiveness
      • ↓ EF via systolic heart failure
    • an index of cardiac contractility
      • ↑ EF, ↑ contractility
    • EF ~ 0.55 or 55%

Pulse Pressure
  • Pulse Pressure (PP) = Systolic Pressure - Diastolic Pressure
    • PP reflects volume of blood ejected from left ventricle on a single beat
      • PP ∝ SV

Mean Arterial Pressure
  • Mean Arterial Pressure (MAP)
    • average pressure in a complete cardiac cycle
  • Equations
    • MAP = CO x Total Peripheral Resistance (TPR)
    • MAP = 2/3 Diastolic Pressure + 1/3 Systolic Pressure
    • MAP = 1/3 PP + Diastolic Pressure
    • as HR increases, diastole decreases and systole increases in the percentage of time spent, thus influencing the MAP

Preload and Afterload
  • Preload
    • aka ventricular EDV
      • preload "pumps up the heart"
    • preload by
      • exercise (slightly)
      • ↑ blood volume
        • e.g., over-transfusion
      • excitement
        • sympathetics
    • Pathology
      • right wall myocardial infarction (inferior wall)
        • ST elevation seen in leads II, III, and avF
        • preload dependent for cardiac function, thus do not diurese
  • Afterload
    • aka MAP
      • ∝ TPR
  • Pharmacology
    • venodilators (e.g., nitroglycerin) ↓ preload 
    • vasodilators (e.g., hydrAlAzine) ↓ Afterload (Arterial)
 

Please rate topic.

Average 4.7 of 9 Ratings

Thank you for rating! Please vote below and help us build the most advanced adaptive learning platform in medicine

The complexity of this topic is appropriate for?
How important is this topic for board examinations?
How important is this topic for clinical practice?
Questions (7)
Lab Values
Blood, Plasma, Serum Reference Range
ALT 8-20 U/L
Amylase, serum 25-125 U/L
AST 8-20 U/L
Bilirubin, serum (adult) Total // Direct 0.1-1.0 mg/dL // 0.0-0.3 mg/dL
Calcium, serum (Ca2+) 8.4-10.2 mg/dL
Cholesterol, serum Rec: < 200 mg/dL
Cortisol, serum 0800 h: 5-23 μg/dL //1600 h:
3-15 μg/dL
2000 h: ≤ 50% of 0800 h
Creatine kinase, serum Male: 25-90 U/L
Female: 10-70 U/L
Creatinine, serum 0.6-1.2 mg/dL
Electrolytes, serum  
Sodium (Na+) 136-145 mEq/L
Chloride (Cl-) 95-105 mEq/L
Potassium (K+) 3.5-5.0 mEq/L
Bicarbonate (HCO3-) 22-28 mEq/L
Magnesium (Mg2+) 1.5-2.0 mEq/L
Estriol, total, serum (in pregnancy)  
24-28 wks // 32-36 wks 30-170 ng/mL // 60-280 ng/mL
28-32 wk // 36-40 wks 40-220 ng/mL // 80-350 ng/mL
Ferritin, serum Male: 15-200 ng/mL
Female: 12-150 ng/mL
Follicle-stimulating hormone, serum/plasma Male: 4-25 mIU/mL
Female: premenopause: 4-30 mIU/mL
midcycle peak: 10-90 mIU/mL
postmenopause: 40-250
pH 7.35-7.45
PCO2 33-45 mmHg
PO2 75-105 mmHg
Glucose, serum Fasting: 70-110 mg/dL
2-h postprandial:<120 mg/dL
Growth hormone - arginine stimulation Fasting: <5 ng/mL
Provocative stimuli: > 7ng/mL
Immunoglobulins, serum  
IgA 76-390 mg/dL
IgE 0-380 IU/mL
IgG 650-1500 mg/dL
IgM 40-345 mg/dL
Iron 50-170 μg/dL
Lactate dehydrogenase, serum 45-90 U/L
Luteinizing hormone, serum/plasma Male: 6-23 mIU/mL
Female: follicular phase: 5-30 mIU/mL
midcycle: 75-150 mIU/mL
postmenopause 30-200 mIU/mL
Osmolality, serum 275-295 mOsmol/kd H2O
Parathyroid hormone, serume, N-terminal 230-630 pg/mL
Phosphatase (alkaline), serum (p-NPP at 30° C) 20-70 U/L
Phosphorus (inorganic), serum 3.0-4.5 mg/dL
Prolactin, serum (hPRL) < 20 ng/mL
Proteins, serum  
Total (recumbent) 6.0-7.8 g/dL
Albumin 3.5-5.5 g/dL
Globulin 2.3-3.5 g/dL
Thyroid-stimulating hormone, serum or plasma .5-5.0 μU/mL
Thyroidal iodine (123I) uptake 8%-30% of administered dose/24h
Thyroxine (T4), serum 5-12 μg/dL
Triglycerides, serum 35-160 mg/dL
Triiodothyronine (T3), serum (RIA) 115-190 ng/dL
Triiodothyronine (T3) resin uptake 25%-35%
Urea nitrogen, serum 7-18 mg/dL
Uric acid, serum 3.0-8.2 mg/dL
Hematologic Reference Range
Bleeding time 2-7 minutes
Erythrocyte count Male: 4.3-5.9 million/mm3
Female: 3.5-5.5 million mm3
Erythrocyte sedimentation rate (Westergren) Male: 0-15 mm/h
Female: 0-20 mm/h
Hematocrit Male: 41%-53%
Female: 36%-46%
Hemoglobin A1c ≤ 6 %
Hemoglobin, blood Male: 13.5-17.5 g/dL
Female: 12.0-16.0 g/dL
Hemoglobin, plasma 1-4 mg/dL
Leukocyte count and differential  
Leukocyte count 4,500-11,000/mm3
Segmented neutrophils 54%-62%
Bands 3%-5%
Eosinophils 1%-3%
Basophils 0%-0.75%
Lymphocytes 25%-33%
Monocytes 3%-7%
Mean corpuscular hemoglobin 25.4-34.6 pg/cell
Mean corpuscular hemoglobin concentration 31%-36% Hb/cell
Mean corpuscular volume 80-100 μm3
Partial thromboplastin time (activated) 25-40 seconds
Platelet count 150,000-400,000/mm3
Prothrombin time 11-15 seconds
Reticulocyte count 0.5%-1.5% of red cells
Thrombin time < 2 seconds deviation from control
Volume  
Plasma Male: 25-43 mL/kg
Female: 28-45 mL/kg
Red cell Male: 20-36 mL/kg
Female: 19-31 mL/kg
Cerebrospinal Fluid Reference Range
Cell count 0-5/mm3
Chloride 118-132 mEq/L
Gamma globulin 3%-12% total proteins
Glucose 40-70 mg/dL
Pressure 70-180 mm H2O
Proteins, total < 40 mg/dL
Sweat Reference Range
Chloride 0-35 mmol/L
Urine  
Calcium 100-300 mg/24 h
Chloride Varies with intake
Creatinine clearance Male: 97-137 mL/min
Female: 88-128 mL/min
Estriol, total (in pregnancy)  
30 wks 6-18 mg/24 h
35 wks 9-28 mg/24 h
40 wks 13-42 mg/24 h
17-Hydroxycorticosteroids Male: 3.0-10.0 mg/24 h
Female: 2.0-8.0 mg/24 h
17-Ketosteroids, total Male: 8-20 mg/24 h
Female: 6-15 mg/24 h
Osmolality 50-1400 mOsmol/kg H2O
Oxalate 8-40 μg/mL
Potassium Varies with diet
Proteins, total < 150 mg/24 h
Sodium Varies with diet
Uric acid Varies with diet
Body Mass Index (BMI) Adult: 19-25 kg/m2
Calculator

Question locked
Sorry, this question is for
PEAK Premium Subscribers only
Upgrade to PEAK
Question locked
Sorry, this question is for
PEAK Premium Subscribers only
Upgrade to PEAK
Question locked
Sorry, this question is for
PEAK Premium Subscribers only
Upgrade to PEAK
Question locked
Sorry, this question is for
PEAK Premium Subscribers only
Upgrade to PEAK

(M1.CV.146) A 27-year-old man is running on the treadmill at his gym. His blood pressure prior to beginning his workout was 110/72. Which of the following changes in his cardiovascular system may be seen in this man now that he is exercising? Review Topic

QID: 100662
1

Increased systemic vascular resistance

50%

(7/14)

2

Decreased heart rate

0%

(0/14)

3

Decreased stroke volume

0%

(0/14)

4

Decreased systemic vascular resistance

50%

(7/14)

5

Decreased blood pressure

0%

(0/14)

M1

Select Answer to see Preferred Response

PREFERRED RESPONSE 4

(M1.CV.126) An 83-year-old male presents with dyspnea, orthopnea, and a chest radiograph demonstrating pulmonary edema. A diagnosis of congestive heart failure is considered. The following clinical measurements are obtained: 100 bpm heart rate, 0.2 mL O2/mL systemic blood arterial oxygen content, 0.1 mL O2/mL pulmonary arterial oxygen content, and 400 mL O2/min oxygen consumption. Using the above information, which of the following values represents this patient's cardiac stroke volume? Review Topic

QID: 100642
1

30 mL/beat

0%

(0/10)

2

40 mL/beat

80%

(8/10)

3

50 mL/beat

10%

(1/10)

4

60 mL/beat

0%

(0/10)

5

70 mL/beat

10%

(1/10)

M1

Select Answer to see Preferred Response

PREFERRED RESPONSE 2

(M1.CV.94) A 40-year-old Caucasian male presents to the emergency room after being shot in the arm in a hunting accident. His shirt is soaked through with blood. He has a blood pressure of 65/40, a heart rate of 122, and his skin is pale, cool to the touch, and moist. This patient is most likely experiencing all of the following EXCEPT: Review Topic

QID: 100610
1

Confusion and irritability

0%

(0/15)

2

Decreased preload

0%

(0/15)

3

Increased stroke volume

80%

(12/15)

4

Decreased sarcomere length in the myocardium

0%

(0/15)

5

Increased thromboxane A2

20%

(3/15)

M1

Select Answer to see Preferred Response

PREFERRED RESPONSE 3
ARTICLES (10)
VIDEOS (2)
Topic COMMENTS (42)
Private Note