hemodynamic monitoring - Unit 2 AH3

hemodynamic monitoring

• early identification of complex medical problems of the critically ill pt (airway breathing circulation)

  • assess for the presence of shock and cardiac and pulmonary abnormalities

  • MI complications

• the nurse can evaluate the pt’s immediate response to txs

  • inotropic meds (ex: dopamine)

  • mechanical support (ex: ventilator)

cardiac output

• the volume of blood pumped by the heart each minute

• normal: 4-6 L/min

• can be measured:

  • pulmonary artery catheter

  • echocardiogram (estimate)

  • indirectly via functional hemodynamics

stroke volume

• the volume of blood pumped by the left ventricle w/ each heartbeat

• dependent on three important factors: preload, afterload, and contractility

preload

• the end diastolic pressure or volume that stretches the right ot left ventricle

• reflects a pts fluid volume status

• volume of blood filling the ventricle during end diastole

• indirectly measured on the right side:

  • right atrial pressure (RAP)

  • central venous pressure (CVP)

  • normal 2-6 mm Hg

• indirectly measure on the left side:

  • pulmonary artery occlusive pressure (PAOP)

  • “wedge” or "PCWP)

  • normal 8-12 mm HG

afterload

• the force or resistance the ventricles must overcome to eject blood into the pulmonary circuit or aorta

contractility

• the inherent ability of the heart muscle to contract independent of preload and afterload

• poor contractility directly affects CO and decreases SV

oxygen delivery

• the amount of o2 delivered to the tissues

• determined through the evaluation of CO and arterial oxygen content (PaO2)

  • normal CO = 4-6 L/min

SVO2 (mixed venous O2 saturation) **on table

• the relationship between oxygen delivery and oxygen extraction at the tissue lvl

• tells you how the patient is UTILIZING oxygen

• can be drawn from a central venous catheter (central line; measures pressure in right atria) or pulmonary artery catheter (swan-ganz; measures pressure in pulmonary artery)

• normal SVO2 = >70%

  • low: <70% = tissues are extracting more O2 than normal, this may result from a decrease in O2 delivery (due to low hemoglobin or low cardiac output)

  • high: normal, should be 70-100%

oxygen ** not on table

• SpO2 95-100%

  • DO2 (decreased O2 delivery)

    • decreased hemoglobin

    • decreased CO

    • decreased SpO2/SaO2

• we normally extract about 25-30% oxygen to the tissues

• SvO2 >70%

  • VO2 (increased O2 consumption)

    • increased work of breathing

    • shivering

    • fever infection

    • agitation

    • nursing care

subtract normal extract of O2 from spo2 and it makes sense that SVO2 is 70%

hemodynamic monitoring systems

• arterial catheter (a-line)

  • measures BP, MAP

  • can obtain ABGs

• central venous catheter

  • measures pressure in the right atria

    • CVP (central venous pressure)

    • can obtain SvO2 through this catheter

• pulmonary artery catheter (aka PA or Swan -Ganz catheter

  • measures pressure in the pulmonary arteries (can indirectly measure left heart function)

  • can obtain SvO2 through this catheter

pressure bag and transducer set up

• pressure bag

• mostly radial, but can have femoral (just don’t want it bc infection near groin can be very common, but can be used if issues with arms (ex: arms crushed)

• pressurized so blood cant come out, and gives blood pressure

Phlebostatic axis

• midpoint of the left atrium, at the fourth intercostal space in the midaxillary line

• transducer need to be even with this axis to get a real bp and if not in line with this axis it can give wrong number

• if move HOB or body make sure transducer stays in line at all times

arterial catheter (a-line) ***on table

• an arterial line is a small catheter inserted into an artery used to display a constant systemic BP

• continuous blood pressure monitoring, MAP

  • especially useful for pts w/ labile BP on vasoactive meds

  • normal BP = 120/80 mmHg

  • normal MAP = >65 mmHg

    • >60 mmHg for organ perfusion, if low not perfusing organs

  • low: hypotension, consider causes

  • high: hypertension, consider causes

• Transducer and pressure bag (so blood cant come out {mostly radial, but can be femoral} set up, leveled at phlebostatic axis (transducer needs to be even w/ this axis, midpoint of left atrium at fourth intercostal space mid clavicular) or could give wrong BP #, if you raise HOB need to keep transducer aligned

• ABG sample

  • monitor a pt acid-base and oxygenation status

• NURSES DON’T DO THIS, A DOCTOR OR RESPIRATORY MUST DO THIS

• NEVER INFUSE ANYTHING THROUGH IT! REMEMBER, IT IS ARTERIAL NOT VENOUS

• if comes out need gauze and pressure because it is an artery (high risk for bleeding)

• pulses paradoxus: exaggerated blood pressure variation w/ respiratory cycles = blood pressure decreased w/ inspiration

  • causes: cardiac tamponade, COPD, asthma

IBP vs NIBP vs MAP

• IBP: invasive BP (in artery)

• NIBP: noninvasive BP (what we as students normally take w/ bp cuff)

• MAP - mean arterial pressure needs to be greater than 65 mmHg

Pulses paradox

• is the term used to describe an exaggerated blood pressure variation w/ the respiratory cycle

• found in cardiac tamponade or during chronic obstructive pulmonary disease or asthma exacerbations

what medications would require an A-line

vasopressers (increased BP)

norepinephrine (Levophed or Levo)

• levo is first line vasopresser

• effect: it’s a vasopressor - increased bp and increased svr, some increased CO

• is titrated - moving it up and down per protocol based on BP

• monitor closely for extravastation

  • IV moves from vein to tissue and will kill the tissue causing necrosis and amputation

  • med is infused into tissue

• watch out for:

  • bradycardia, dysrhythmias, HTN, renal artery vasoconstriction (low urine output)

  • digit and gut ischemia at higher doses

• alpha (periphery {the rest of blood vessels in body and helps constrict vessels) and beta 1 (the heart {beta 2 would be the lungs})

vasopressin (pitressin)

• effect: it’s a vasopressor: increased BP, increased SVR

• DO NOT TITRATE

• 2nd line vasopressor in sepsis and cardiac surgery

• also given for gi bleeding and diabetes inspiidus

phenylephrine

• effect: vasopressor - increased BP, and increased SVR

• TITRATE

• watch out

  • reflex bradycardia - due to selective vasoconstriction and elevation of blood pressure

  • arrhythmias

  • HTN

  • chest pain

• all 3 meds need central line and all need to run on it’s own line

central venous pressure **on table

• central venous pressure - provides information about the Right side of the heart, this reading is taken through the distal port of a central line

  • long catheter placed in the internal jugular (IJ), subclavian (SC), or femoral vein

  • right atrial pressure

    • the CVP lvl indicates mean RA pressure (indirect way to measure preload) and is typicaly used as an estimate of right ventricular filling pressures or volume returning to the right heart from the systemic circulation (preload)

    • normal CVP is 2-6 mmHg

      • lower number = “dry” fluid volume deficit

      • high number = fluid volume overload

    • 
      

pulmonary artery catheter

• provides information about the right and left side of the heart

  • right side:

    • pulmonary artery pressures

      • reflect the BP in the pulmonary artery

      • normal parameters are pulmonary artery (PA) systolic 15-30 mmHg and PA diastolic 4-12 mmHG (about 25/10)

      • if high = pulmonary hypertension

      • if low = impaired right heart function

  • left side:

    • pulmonary artery occlusion pressure/pulmonary artery wedge pressure (PAOP or PAWP) - indirect measurement of left atrial pressure

      • normal is 8-12 mmHg

        • 10mmHg

      • if high:

        • fluid volume overload

        • mitral stenosis or insufficiency

        • left ventricular failure

        • cardiac tamponade

        • constrictive pericarditis

        • high lvl of PEEP

• a PA (Swan-Ganz) catheter is a flexible, balloon tipped catheter that is guided through the right side of the heart and into the pulmonary artery

• the PA catheter is 110 cm long and has four lumens, the distal, proximal, thermistor, and inflation lumens, each of which leads to a specific port. some PA catheters have a second proximal lumen used for IV medication infusion