Hemodynamic monitoringMagdy M Khalil, MD, EDIC

Tissue perfusion

•Oxygen delivery = CO x arterial oxygen content

CO = (SV x HR) x {(Hb x 1.39 x SaO2) + (0.003 x PaO2)}

•Arterial pressure (AP) = CO x SVR

Diagnosis of tissue malperfusion

•Clinical assessment•Basic monitoring•Preload monitoring•Minimally invasive cardiac output/cardiac

contractility assessment•Invasive; pulmonary artery catheter•Assessment of tissue perfusion

Clinical assessment

•Thirst, •Cold mottled extremities,•Poor peripheral pulses,•Impaired capillary refill,•Tachypnoea, •Tachycardia, •Altered mentation, or•Oliguria.

Basic monitoring

•Electrocardiography (ECG), •Arterial blood pressure (AP), •Pulse oximetry (SpO2) monitoring, •Baseline serum lactate.

Arterial blood pressureMeasurement• Non-invasive• Invasive

Indications for invasive arterial pressure monitoring: • Labile blood pressure• Severe hypotension• Use of rapidly acting vasoactive drugs• Frequent sampling of arterial blood.Relative indications : • Severe hypertension• Presence of an intra-aortic balloon pump• Morbid obesity.

SpO2 monitoring

•The SpO2 signal is often inaccurate in the presence of altered skin perfusion

Serum lactate

•Normal level in resting humans 1 mmol/l (0.7-1.3).

•Same in venous or arterial blood•Factors affecting serum lactate level:

Venous oxygen saturation•Cardiac output •hypoxia and •anaemia also affect the ScvO2. • pain, shivering and increased work of

breathing can also affect the ScvO2 value.•

carbon monoxide poisoning, cyanide poisoning, and intra-cardiac shunt

•The normal range of ScvO2 in critically ill patients is 70-75%

Preload monitoring • Examination of the right internal jugular vein

• Central venous pressure (CVP). ▫Catheter in SVCAn elevated intracardiac pressure may be due to an elevated volume or an elevated resistance (Acute heart failure, cardiac

tamponade, constrictive pericarditis, restrictive cardiomyopathy, tricuspid stenosis or regurgitation)

▫Estimated from respiratory motion of IVC (SB).

• End-diastolic volumes (TTE /TOE)

Predicting fluid responsiveness

Change in CO in response to a change in preload

•Fluid challenge while monitoring:▫ AP, ▫heart rate, ▫CVP and ▫urine output.

Predicting fluid responsiveness

• Static parametersGEDV is the volume of blood contained in the four chambers of the heart at end diastole. ITBV is the volume of blood in the four chambers and the blood volume in the pulmonary vessels at end diastole

• Dynamic parameters • pulse pressure variation (PPV) ≥13% , • systolic pressure variation (SPV) greater than 10 mmHg

on MVand • stroke volume variation (SVV).

• The normal healthy heart is fluid responsive. The demonstration of fluid responsiveness is not an indication, by itself, to administer fluids

Minimally invasive CO/CC assessmentIndications•Hypotension despite fluid resuscitation, or •Continued evidence of global tissue

hypoperfusion•Low CO + elevated measures of

preload=ventricular failure. •High CO+ tissue hypoperfusion, e.g.

septic shock.

Minimally invasive methods of CO measurement• Echocardiography (EF

>55%) • Pulse contour analysis:

measuries SV on a beat-to-beat basis from the arterial pulse pressure waveform.

• Oesophageal Doppler: measures blood flow velocity) in the descending aorta (70% of total CO)

• Methods using the Fick principle (Patient on MV)

Contraindications to oesophageal Doppler :

• Unexplained history of dysphagia

• Oesophageal pathology e.g. varices, stricture, oesophagitis

• Oropharyngeal pathology • Unstable cervical spine

injury

Transpulmonary thermodilution; cardiac output and volumetric parameters

• Global end-diastolic volume (GEDV): ITTV – PTV (600-800 ml/m 2)

• Intrathoracic thermal blood volume (ITBV): 1.25 x GEDV ( 850-1000 ml/m 2)

• Pulmonary blood volume (PBV): ITBV – GEDV• Extravascular lung water (EVLW): ITTV –

ITBV ( 3.0-7.0 ml/kg).• Pulmonary vascular permeability index

(PVPI) ( 1.0-3.0): EVLW /PBV reflects the permeability of the alveolar–capillary barrier. PVPI is higher in ALI/ARDS

Pulmonary artery catheterContinuous monitoring of :• RAP• PAP• PAOP (5-12 mmHg)• CO• SvO2. Indications:• Circulatory shock with

evidence of tissue hypoperfusion not responding to therapy.

• Management of severe pulmonary oedema.

• Difficulty evaluating right and left ventricular preload in the presence of oliguria.

Interpreting haemodynamic data•Is there evidence of tissue hypoperfusion?•Is there a reduction in arterial oxygen

content?•Is there a question regarding optimal

preload?•Is there a question regarding stroke

volume/cardiac contractility?•Is there a need for PAC?