Critical Care OB

Question 1

Cardiac output in pregnancy (definition, normal values in pregnancy)

Answer 1

Cardiac Output: amount of blood pumped through the heart in L/min
- Normal value in pregnancy = 5.5-7.5L/min
- Determinants of CO: preload, afterload, contractility, HR

Question 2

Preload ((definition, normal values in pregnancy)

Answer 2

Preload= CVP
volume of blood in ventricle before systole/contracteion
o Right preload reflected by the CVP (4-10mmHg)
o Left preload reflected by PCWP or wedge pressure (6-12 mmHg)
o To increase preload: LLD position, IV fluids, blood
o To decrease preload: sitting position, decrease fluids, diuretics

Question 3

Afterload (definition and normal values in pregnancy)

Answer 3

• Afterload: resistance the ventricle has to overcome to eject blood
  o R afterload determined by pulmonary vascular resistance
   PVR 55-100 dynes/sec/cm-5
  o L afterload determined by systemic vascular resistance
   SVR 1000-1400 dynes/sec/cm-5
  o To increase L afterload: correct preload, LLD position, vasopressors
  o To decrease L afterload: correct preload, antihypertensives

Question 4

Contractility (definition and normal values in pregnancy)

Answer 4

o Strength of ventricular contraction; typically LV is assessed
o Contractility is reflected by LV stroke work index (LVSWI)
o LVSWI 40-55gM/m2
o To increase contractility, correct preload and afterload, give inotropic agents

Question 5

Invasive monitoring for hemodynamics in pregnancy - types and indications for monitoring

Answer 5

o Intra-arterial catheter
 Continuous direct meausurement of pressure within artery
 Radial is most common site
 Convenient for frequent ABG
o Venous Central Pressure Catheter
 Single or multiple lumen advanced until tip is in proximal SVC
 Typically right internal jugular vein or R sublcavian vein
 CVP measurement
 Ports for rapid infusion of fluids or blood
o Pulmonary artery catheter
 Multiple lumen catheter introduced into the PA through central vein (same access as for CVP line)
 Provides CVP, pulmonary artery pressures, PCWP, CO
 Additional ports for rapid infusion of fluids/blood
 Temperature difference is how pulm art catheter measures CO
- Indications for invasive monitoring:
o Sepsis with hypotention or oliguria
o Pulm edema, heart failure
o Severe PIH with pulm edema
o Cardiovascular decompensation
o Massive blood volume replacement
o ARDS
o Shock

Question 6

How to interpret hemodynamic profile

Answer 6

o CO: too high? Too low? (in pregnancy, low is < 3L)
o PCWP: too high or low? (high = wet picture)
o SVR: reflects afterload
o LVSWI: is ventricle contracting normally

o Right preload reflected by the CVP (4-10mmHg)
o Left preload reflected by PCWP or wedge pressure (6-12 mmHg)
o R afterload determined by pulmonary vascular resistance
 PVR 55-100 dynes/sec/cm-5
o L afterload determined by systemic vascular resistance
 SVR 1000-1400 dynes/sec/cm-5