T6 - Choque e Monitorização Hemodinâmica (1)

Question 1

Shock?

Answer 1

➢ State of cellular and tissue hypoxia due to reduced oxygen delivery and/or increased oxygen consumption or inadequate oxygen utilization
➢ Mismatch entre a entrega e o consumo de oxigénio
➢ Pode ser devido a:
- diminuição de entrega
- aumento do consumo
- inadequada utilização do oxigénio pelos tecidos
➢ Estas 3 situações podem combinar-se de diversas maneiras

Question 2

Types of shock?

Answer 2

➢ Distributive:
- Severe peripheral vasodilatation (vasodilatory shock).
- Septic; anaphylactic; neurogenic; drug and toxin induced; endocrinologic.

➢ Cardiogenic:
- Due to intracardiac causes of cardiac pump failure that result in reduced cardiac output (CO).
- Cardiomyopathic; arrhytmic; mechanical.

➢ Hypovolemic:
- due to reduced intravascular volume (ie, reduced preload), which, in turn, reduces CO.
- Hemorrhagic; nonhemorrhagic

➢ Obstructive:
- mostly due to extracardiac causes of cardiac pump failure and often associated with poor right ventricle output.
- Pulmonary vascular; mechanical

Question 3

A the bedside, hemodynamic stability and tissue perfusion are monitored by a combination of?

Answer 3

✓ clinical examination
✓ monitoring devices
✓ laboratory results

Question 4

Hemodynamic monitoring can be approached in a series of steps aimed at assessing global and regional perfusion?

Answer 4

Initial steps
✓ 1. Clinical assessment
✓ 2. Basic monitoring and assessment of global perfusion
✓ 3. Preload monitoring and fluid responsiveness

Advanced monitoring measures
✓ 4. Cardiac output monitoring
✓ 5. Assessment of cardiac contractility

Question 5

Clinical assessment?

Answer 5

✓ Thirst,
✓ Pale and cold extremities,
✓ Poor peripheral pulses and impaired capillary refill (ginástica capilar)
✓ Tachypnoea, tachycardia, (primeiras respostas á inadequada entrega de oxigénio)
✓ Confusion, (encefalopatia)
✓ Oliguria.

Question 6

Skin Mottling?

Answer 6

✓ Pele marmoreada
✓ Particular attention should be made to detecting skin mottling.
✓ It has been shown to independently predict mortality in septic shock.

Question 7

ECG monitoring?

Answer 7

✓ Heart rate is an important determinant of cardiac output.
✓ Tachyarrhythmias are the commonest finding in hypoperfusion states.
✓ Cardiac output = Stroke volume x Heart rate
✓ Taquicardia é uma das 1as respostas orgânicas a tentar repor a redução do DC
✓ Sempre que VE diminui, por perda de contratilidade cardíaca, ou redução de pré-carga ou por aumento de pós-carga, a tendência é a FC aumentar

Question 8

Blood pressure monitoring?

Answer 8

✓ Measuring arterial blood pressure (AP) is a cornerstone of hemodynamic assessment.
✓ The definition of low AP is patient-specific and interpreted in the context of the patient’s usual AP.
✓ Mean arterial blood pressure (MAP) is an approximation of organ perfusion pressure. When stroke volume falls, MAP can initially be maintained by increasing heart rate or peripheral vasomotor tone.
✓ Arterial blood pressure = Cardiac Output x Systemic Vascular Resistance

Question 9

SpO2 monitoring?

Answer 9

✓ Continuous SpO2 monitoring enables almost immediate detection of even a small reduction in arterial oxygen saturation, which is an integral part of oxygen delivery.
✓ Taking into account the shape of the O2 dissociation curve, SpO2 should be maintained at >92% in most critically ill patients.
✓ The SpO2 signal is often inaccurate in the presence of altered skin perfusion, The inability to measure SpO2 is an indicator of abnormal peripheral perfusion
✓ In carbon monoxide poisoning, pulse oximetry does not provide accurate measurement of O2 saturation

Question 10

Serum lactate?

Answer 10

✓ Normal serum lactate level in resting humans is approximately 1 mmol/L (0.7-2.0).
✓ Elevated levels may represent poor tissue perfusion. The association of increased lactate levels with circulatory failure, anaerobic metabolism and the presence of tissue hypoxia has led to its utility as a monitor of tissue perfusion in critically ill patients
✓ Repeated measurements of lactate concentrations over time are particularly useful for monitoring the response to therapy
✓ The liver accounts for approximately 50% of lactate clearance

Question 11

ScvO2 (Central venous oxygen saturation)?

Answer 11

✓ Oxygen saturation of blood in the superior vena cava (needs insertion of a central venous catheter)
✓ Is a global indicator of tissue oxygenation and has been shown to be useful in guiding resuscitation in the early stages of septic shock
✓ The normal range of ScvO2 in critically ill patients is 70-75%
- qnd abaixo - precisamos de melhorar a entrega de O2 aos tecidos, aumentando a pré-carga ou a contratilidade cardíaca ou Hemoglobina
- qnd acima - há um componente distributivo no choque que condiciona uma inadequada extração de oxigénio

Question 12

Basic monitoring and assessment of global perfusion?

Answer 12

An early hemodynamic optimization that targets central venous oxygen saturation (ScvO2) and systemic hemodynamic parameters improve outcomes in severe sepsis and septic shock, reinforcing the idea that tissue perfusion abnormalities are flow-dependent at least during the very early stages

Question 13

cvaCO2 gap (Central venous to arterial CO2 difference)?

Answer 13

✓ CO2 is the end product of aerobic metabolism and its concentration in the venous blood reflects the global tissue blood flow relative to metabolic demand.

✓ Patients with high cvaCO2gap values have lower lactate clearance and CI values.

✓ It’s a useful complementary tool to identify patients who remain inadequately resuscitated when the 70 % ScvO2 threshold value has been reached.

Question 14

Preload?

Answer 14

✓ Defined as end-diastolic myocardial stretch (wall tension) and is often estimated at the bedside by a single/static measurement e.g. central venous pressure, CVP.

✓ Traditionally, CVP has been used to guide fluid management, but it is a poor predictor of fluid responsiveness and may not accurately reflect preload (não se utiliza frequentemente na medicina intensiva)

Question 15

Preload and fluid responsiveness - Testing?

Answer 15

✓ At the bedside, a rapid and easy way to assess fluid responsiveness is to give fluid, called a ‘fluid challenge’.
✓ A patient whose stroke volume increases following a fluid challenge is on the ascending limb of the Frank-Starling (FS)
✓ Give 500 ml of crystalloid over 10-15 minutes and observe the effect on blood pressure and jugular venous/central venous pressure, or stroke volume
✓ Corremos o risco de aumentar o edema intersticial ao dar fluidos a doentes que não necessitavam

✓ An alternative to a fluid challenge is to perform a “passive leg raise’ manoeuvre”.
✓ This produces an ‘autotransfusion’ of blood from the venous compartments in the abdomen and lower limbs. It has the advantage of being easily reversible, and can be used in spontaneously breathing patients

Question 16

Dynamic preload measures?

Answer 16

Are based on the ‘normal’ physiological effects of positive pressure ventilation on the right and left sides of the heart.
✓ Pulse pressure variation (PPV)
✓ Systolic pressure variation (SPV)
✓ Stroke volume variation (SVV)
✓ End-Expiratory Occlusion Test (TOTE)
✓ IVC/SVC Collapsibility by transthoracic/transoesophageal echocardiography

Question 17

Pulse pressure variation (PPV)?

Answer 17

✓ Pulse pressure : difference between the arterial systolic and diastolic pressure.
✓ PPV: refers to the difference between the maximum (PPmax) and minimum (PPmin) pulse pressure over a single mechanical breath.

PPV% = 100 x {(PPmax – PPmin )/ (PPmax + PPmin)/2}

✓ A PPV of ≥13% has been shown to be a specific and sensitive indicator of preload responsiveness

Question 18

Systolic pressure variation (SPV)?

Answer 18

✓ The change in systolic pressure over one mechanical breath is termed systolic pressure variation.
✓ Changes in systolic pressure with mechanical inspiration may predict response to volume expansion, but with less sensitivity and specificity than PPV.

Question 19

Stroke volume variation (SVV)?

Answer 19

✓ Stroke volume can be measured by arterial waveform analysis. It can also be measured using esophageal Doppler technology and echocardiography
✓ SVV of ≥10% has also been shown to be a specific and sensitive predictor of fluid responsiveness

Question 20

End-Expiratory Occlusion Test (TOTE)?

Answer 20

✓ An end-expiratory occlusion may prevent the cyclic impediment in left cardiac preload and may act like a fluid challenge
✓ The end-expiratory occlusion significantly increases arterial pulse pressure by 15% and cardiac index by 12% in responders

Question 21

IVC/SVC Collapsibility by transthoracic/transoesophageal echocardiography?

Answer 21

✓ Positive pressure ventilation also produces change in both superior vena cava (SVC) and inferior vena caval (IVC) diameter.

✓ Cyclical changes in SVC and IVC diameter, termed ‘collapsibility’, during mechanical ventilation may therefore be used to predict fluid responsiveness.