Heamodynamic monitoring Flashcards
1
Q
Name 9 tools of haemodynamic monitoring?
A
- Physical examination
- ECG
- Blood pressure
- CVP
- ScvO2
- noramlisation of lacttate + base deficit
- pulmonary artery pressure
- SvO2
- measurement of CO/CI
- sonographic assessment of caudal vena cava collapsability
1
Q
What are the normal BP values for a dog?
A
systolic: 150 +/- 20mmHg
mean: 105 +/- 10mmHg
diastolic: 85 +/- 10mmHg
2
Q
What are the normal BP values for a cat?
A
systolic: 125 +/- 10mmHg
mean: 105 +/- 10mmHg
diastolic: 90 +/- 10mmHg
3
Q
How is MAP calculated?
A
MAP = diastolic + (systolic-diastolic)/3
4
Q
How is hypotension defined?
A
SAP < 90mmHg or MAP <60mmHg
5
Q
Name 4 causes of hypotension?
A
- Reduced circulating volume
- Myocardial failure
- Severe brady- or tachyarrythmias
- decreased SVR
6
Q
What are the two types of hypertension?
A
- primary (rare)
- secondary
7
Q
What ist the most common cause of secondary hypertension?
A
kidney injury or failure
8
Q
Name 6 causes of secondary hypertension?
A
- kidney injury or failure
- hyperthyroidism
- pheochromocytoma
- hyperadrenocorticism
- diabetes mellitus
- drugs (glucocorticoids, cyclosporine A, phenylpropanolamine, erythropoietin)
9
Q
Name 5 types of blood pressure measurement?
A
- Doppler
- oscillometric
- high-definition oscillometric
- photoplethysmography
- invasive
10
Q
Discuss the priciple of non-invasive BP measurement?
A
based on inflation of a cuff around a limb or the tail to occlude arterial flow, followed by measurement of the pressure at which flow returns
11
Q
What is the guideline for cuff size in NiBP measurement in dogs and cats? At what level should it be obtained?
A
- 40% of the circumference of the limb for dogs
- 30% of the circumference of the limb for cats
- at the level of the right atrium
12
Q
Discuss the principle and technique of Doppler NiBP measureement?
A
10-MHz ultrasound probe is used to detect blood flow in an artery. The probe is placed over an artery distal to the cuff and the cuff is inflated to a pressure high enough to stop blood flow. Doppler sounds become audible when pressure in the cuff is less than the pressure in the artery.
13
Q
What value of NiBP does Doppler measurement repsent in the dog and cat?
A
- Bourazak et al. JAVMA 2018: in anaesthetised dogs presented SAP
- Caulkett et al. Vet Surg 1998: in healthy, anaesthetised cats Doppler consistently underestimated SAP by 10 to 15 mm Hg and was more closely correlated with MAP
14
Q
Discuss the sensitivity and specifity of Doppler NiBP measurement in anaesthetised dogs?
A
Bourazak et al. JAVMA 2018:
- resulted in errors diagnosing hypotension
- had low sensitivity –> did not detect hypotension in some dogs
- good specificity: could be used to confirm hypotension
15
Q
Discuss the principle and technique of oscillometric NiBP measureement?
A
- cuff is alternately inflated + deflated
- during deflation alterations in cuff pressure due to pulse pressure changes are sensed by the transducer.
- peak amplitude of oscillations equals MAP
- SAP equals pressure at which oscillations are first detected,
- DAP equals pressure at which oscillations decrease rapidly
16
Q
Which blood pressure is actually measured by a regular oscillometric NiBP machine, and which are calculated?
A
- MAP measured, SAP + DAP calculated
17
Q
What can be used to assess reliability of oscillometric NiBP readings and why?
A
- HR
- HR is measured as the number of oscillations/min –> should be compared with the patient’s actual HR
18
Q
How good is the correlation of oscillometric BP measurement and invasive BP measurement in dogs/cats?
A
- some showed acceptable correlation (Bodey et al in Res Vet 1994 - 1996, Stepien et al. JAVMA 1999, Meurs et al. JAAHA 1996, Binns et al JVIM 1995, Pedersen et al JAVMA 2002)
- Acierno et al, JVECC 2013: Poor agreement in anesthetized dogs
- Acierno et al, JAVMA 2010: poor correlation in anesthetized cats
- Bosiack et al, JVECC 2010: awake, ill dogs not well correlated
19
Q
What does the consensus statement on hypertension published by the American College of Internal Medicine state about indirekt BP measurement?
A
none of the units currently available for indirect blood pressure monitoring in awake dogs and cats meet the validation criteria used in human medicine
- currently available devices should be used with a degree of caution
20
Q
What is HDO NiBP measurement and what is the difference to regular oscillometric NiBP measurements?
A
High-definition oscillometry (HDO):
- performs real-time analysis of arterial wall oscillations to obtain pressure-wave amplitudes
- SAP + DAP are measured instead of calculated
- accurate readings from 5 to 300 mm Hg
- high-speed analysis t–> measurements at HR of up to 500 beats/min + during severe arrhythmias
21
Q
Report the findings of Petric et al JFMS 2019 (cats) + Chetboul et al. AJVR 2010 (dogs) about HDO NiBP?
A
Petric et al:
Compared to Doppler, HDO overestimated low pressure and underestimated high pressure values in anaethetised cats
Chetboul et al:
- SAP may be assessed in healthy, awake dogs by use of DU + HDO with good repeatability and reproducibility after a short period of training.
- variability of DAP is higher + longer training is required to assess DAP via DU than via HDO
22
Q
What is photoplethysmography?
A
The blood volume in an extremity varies in a cyclic pattern with each cardiac cycle. The variation is detected by a photoplethysmograph attached to a foot or tail. If the cuff is inflated and deflated fast enough to maintain a constant volume in the extremity/tail the cuff pressure will equal intraarterial pressure.
constant, real-time display of cuff pressure =intraarterial pressure + measurement of SAP + DAP
23
Q
Discuss the principle of and how to perform an invasive BP measurement?
A
- placement of arterial catheter
- connecttion to a semirigid tubing that has been primed with heparinized saline
- fluid bag is pressurized to 300 mm Hg to prevent backward flow of arterial blood into the tubing + maintain patency by administering 3 ml/hr of isotonic saline.
- Attatchment of the tubing from the catheter to a pressure transducer that is connected to a cable + placed at the level of the patient’s heart.
- pressure transducer converts the pressure changes into an electrical signal
- transducer cable carries signal to the monitor
- signal is amplified + displayed on a monitor as a pressure waveform showing the peak systolic pressure, dicrotic notch (which is created by closure of the aortic valve), and diastolic pressure. Monitors can also display numeric values for SAP/MAP/DAP
24
How is the dicrotic notch created in invasive BP measurement?
by the closure of the aortic valve
25
Name 5 reasons for an erroneous invasvie BP reading?
- usage of compliant tubing
- catheter is lodged up against arterial wall
- clot formation at the tip of the catheter
- air bubbles in the catheter or tubing
- kinking of the catheter or tubing
waveform gets dampened --> falsely low SAP and falsely high DAP
26
Name 4 complication of invasive BP monitoring=
- hematoma formation at the site of arterial puncture (most common one)
- infection
- thrombosis of the artery
- necrosis of the tissues distal to the catheter (particularly in cats if > 6 to 12 hr
27
How is Systolic Pressure Variation (SPV) defined? What value correlates with hypovolemia in humans?
difference between maximum systolic pressure (SPmax) during inspiration and minimum systolic pressure (SPmin) during expiration
SPV >10 mm Hg correlates well with hypovolemia + fluid responsiveness in people
28
How is Pulse Pressure Variation (PPV) defined and what values correlate with hypotension and fluid responsiveness, respectively?
PPV (%) = 100 x (PPmax - PPmin)/[(PPmax + PPmin)/2]
PPmax = difference between systole and diastole that is greatest during that breath
PPmin = difference between systole and diastole that is smallest
> 13%: hypotensive + more likely to be fluid responsive
> 10% is positively associated with fluid responsiveness
29
What is the underlying physiologic principle of SPV and PPV for haemodynamic monitoring?
Blood pressure normally varies slightly with respiration; these changes are intensified by hypovolemia. The heart, vena cava + pulmonary veins are somewhat collapsible, and therefore affected by changes in intrathoracic pressure caused by respiration. SPV and PPV are useful techniques in anesthetized patients receiving positive pressure venitlation with static tidal volumes.
30
Why is SPV and PPV not interpretable in non-ventilated patients?
due to changes in tidal volume with spontaneous respiration + use of negative pressure for inhalation
31
What is the principle of telemetric blood pressure monitoring?
Device is placed subcutaneously, and the polyurethane catheter with an antithrombogenic coating and biocompatible gel is fed into the femoral artery.
- used in laboratory settings+ experimentally in cats + dogs
32
What is the Central Venous Pressure (CVP)?
hydrostatic pressure in the intrathoracic vena cava and, in the absence of a vascular obstruction, is approximately equal to right atrial pressure (RAP). When the tricuspid valve is open, RAP equals right ventricular end-diastolic pressure (RVEDP). This pressure is used to estimate right ventricular end-diastolic volume (RVEDV) and the relationship between blood volume and blood volume capacity.
- gives a measure of the relative ability of the heart to pump the volume of blood that is returned to it
33
Name 4 patients that benefit from CVP monitoring?
1. Hypovolemic
2. Septic
3. Renal disease (oliguric/anuric)
4. Cardiac disease
34
Do peripheral and central venous pressure correlate?
Chow et al in AJVR 2006:
- PVP was poorly correlated with CVP when different catheter sizes, catheterization sites, and patient positions were evaluated
- Peripheral venous pressure should not be used to approximate CVP in awake dogs and cats
35
Can a peripheraly inserted central catheter through the femoral vein be used for CVP monitoring?
Yes. It measure CVP accurately in cats without significant intraabdominal disease and in puppies.
36
Discrive the technique of CVP monitoring?
- catheter should be positioned in the cranial or caudal vena cava just outside of the right atrium
- catheter is then connected to a three-way stopcock via noncompliant tubing + to a manometer containing heparinized saline or to a pressure transducer as in invasive BP monitoring
- 0 reference point for the bottom of the manometer/pressure transducer should be the manubrium in lateral recumbency or the point of the shoulder in sternal
CVP measured with a transduce will be in mm Hg --> multiplied by 1.36 to convert the value to cm H2O
37
What is a normal mean CVP value?
- 0-5 cm H2O
- but can vary in individual animals --> trends in the CVP much more significant than individual readings
- Values can be affected by patient positioning (use consistent positioning) as well as catheter positioning
38
Describe the changes of CVP seen during respiration + cardiac cycle?
Inspiration: intrathoracic pressure decreases + CVP falls
Exhalation: intrathoracic pressure increases + CVP rises Patients with increased inspiratory effort secondary to an upper airway obstruction will have exaggerated changes in intratho- racic pressure. Positive pressure ventilation will reverse this pattern.
39
How is CVP monitoring effected by upper airway obstruction?
Patients with increased inspiratory effort secondary to an upper airway obstruction will have exaggerated changes in intrathoracic pressures and therefore CVPs
Positive pressure ventilation will reverse this pattern.
40
How is CVP monitoring effected during PPV + by PEEP?
PPV increases intrathoracic pressures + therefore increases RAP --> increased CVPs
PEEP increases RAP --> increases CVPs
- 5 cmH2O increase in PEEP w= 2.5 cmH2O raise in CVP in people
41
Describe the various waves and their representation seen in the CVP monitoring curve?
a wave = increase in the CVP caused by right atrial con- traction
c-wace = bulging of the tricuspid valve into the RA -->increases RAP + CVP as the RV contracts
v wave = increasing pressure from blood flowing into the RA before the tricuspid valve opens
x descent = decrease in atrial pressure during ventricular ejection
y descent = rapid emptying of the RA as the tricuspid valve opens, allowing blood to flow into the RV
42
What is a large c-wave often associated with?
tricuspid regurgitation
43
Name 2 caues of a CVP <0 cm H2O?
- hypovolemia due to fluid loss
vasodilation secondary to decreased peripheral venous resistance
44
Name 6 caues of a CVP >10 cm H2O?
- volume overload
- right-sided heart dysfunction or failure
- pericardial effusion
- restrictive pericardial disease
- blood flow obstruction (e.g., pulmonic stenosis)
- significant pleural effusion
45
What CVP is associated with edema formation or cavitary effusions?
>16 cmH2O
46
What change in CVP would be expected in a hypovolemic patient as response to a fluid bolus?
CVP will either show no change or will have a transient rise toward normal, then rapidly decrease again
vascular bed is a very compliant system, able to accommodate changes in volume with minimal changes in pressure
47
What change in CVP would be expected in an euvolemic patient as response to a fluid bolus?
small increase of 2-4 cm H2O with a return to baseline within 15 minutes
48
What change in CVP would be expected in an hypervolemic patient as response to a fluid bolus?
A large increase (>4 cm H2O) and slow return to baseline (>30 minutes)
49
What change in CVP would be expected in a patient with reduced cardiac compliance as response to a fluid bolus?
A large increase (>4 cm H2O) and slow return to baseline (>30 minutes)
50
Name x contraindications for CVP monitoring?
Same as for CVC placement:
- coagulopathies that would make puncture of the jugular or femoral vein an unacceptable risk high
- risk of thromboembolic disease (PLN, hyperadrenocorticism, immune-mediated diseases)
- increased ICP (seizures, TBIs, intracranial disease)
51
What was the finding of a systematic review of the literature in 2008 by Marik et al about correlation of CVP + blood volume status and fluid responsiveness?
- very poor relationship between CVP and blood volume status
- inability of CVP or change in CVP to predict fluid responsiveness
52
What do Surviving Sepsis Guidelines say about CVP monitoring?
No longer included
53
What is the biggest limitation of CVP monitoring?
measures the pressures on the right side of the heart instead of the left side but left side supplies the systemic circulation and drains the pulmonary circulation
54
What are PAP and PAOP? Describe the technique, the physiology behind it and the difference of those techniques?
PAP = pulmonary artery pressure
PAOP = pulmonary artery occlusion pressure (pulmonary wedge pressure)
A catheter is placed in jugular vein, through the RA and RV , and into the pulmonary artery. A pulmonary artery catheter allows for measurement of the systolic, diastolic, and mean PAP.
PAOP:
If the catheter is equipped with a balloon PAOP is measured when the balloon at the end of the catheter is inflated in a distal branch of the pulmonary artery. Inflation of the balloon temporarily obstructs blood flow --> measured pressure reflects the LA filling pressure as it equilibrates across the pulmonary capillary bed. When the mitral valve is open, LAP equals LVEDP --> provides the best measure of LV preload + is most accurate predictor of pulmonary edema secondary to VO.
55
What is preload?
- amount of stretch in the ventricle at the end of diastole
- important determinant of CO
56
What is a normal PAOP in dogs?
5-12 mmHg
57
What would a low PAOP (<5mmHg) suggest?
volume depletion + need for fluid administration
58
What would a high PAOP (>12mmHg) suggest?
- VO or cardiac dysfunction
- additional fluid is contraindicated
59
What type of catheter is used for PAP and PAOP monitoring?
Swan-Ganz catheter
60
What can be measured with a Swan Ganz catheter?
- PAP
- PAOP
- RAP
- CO via thermodilution technique
- SvO2 (if equipped with oximeter)
61
What is the formula for Cardiac Index?
CI = CO/BSA (m2)
62
What is the formula for Stroke Volume?
SV = CO/HR
63
What is the formula for Stroke Volume Index?
SVI = SV/BSA
64
What is the formula for Systemic Vascular Resistance?
SVR = (MAP-RAP)/CI
65
What is the formula for Pulmonary Vascular Resistance?
PVR = (mean PAP - PAOP)/CI
66
Name 5 complications of a Swan Ganz catheter (pulmonary artery catheter) placement?
1. Arrhythmias
2. damage to the tricuspid valve
3. damaege to the pulmonic valve
4. pulmonary artery rupture
5. pulmonary thromboembolism
67
What is the normal CO for dogs and cats?
dogs: 125-200 ml/kg/min
cats: 120 ml/kg/min
68
What is the differenve between SvO2 and ScvO2 regarding location and what it measures?
Location:
SvO2: pulmonary artery (needs pulmonary artery catheter)
ScvO2: Vena cava or RA (fewer complications)
Measurement:
SvO2: true mixed venous blood from the entire body after exiting the RV + entering the PA
ScvO2: measures venous blood returning from the upper half of the body (i.e., jugular vein)
69
Name 2 techniques for measurement of SvO2/ScvO2?
1. Co-oximetry
2. real-time measurement via fiberoptic fiber probe + monitor
70
What are normal SvO2 and ScvO2 values in healthy resting animals/humans? Why is one lower than the other?
SvO2: 70-75%
ScvO2: 65-70%
ScvO2 is normally slightly lower than SvO2 due to the higher oxygen demand from the brain
71
How is the correlation between SvO2 and ScvO2?
very strong correlation but can differ by up to 18% in severe shock states
72
What causes a decrease in SvO2/ScvO2?
Tissue hypoxia causes increased extraction of O2 from venous blood --> decrease in SvO2 + ScvO2.
Increased venous oxygen extraction and resulting venous desaturation is one of the major compensatory responses to help maintain delivery of oxygen to the peripheral tissues in low flow states.
73
What does measurement of SvO2 and ScvO2 reflect?
- systemic oxygen balance and cumulative oxygen debt
ScvO2 = prognostic indicator in people with sepsis, trauma, and cardiac disease
74
What were the findings of Rivers et al NJEM 2001 in "Early goal-directed therapy in the treatment of severe sepsis and septic shock"?
Patients with severe sepsis or septic shock:
130 early goal-directed therapy vs. 133 standard therapy:
Endpoint of resuscitation: ScvO2 >70% (among others)
Main finding:
- Significant difference in In-hospital mortality: EGDT 30.5%
and standard therapy 46.5%
- EGDT had a significantly higher mean (+/-SD) ScvO2 (70.4+/-10.7% vs. 65.3+/-11.4%), a lower lactate (3.0+/-4.4 vs. 3.9+/-4.4 mmol/l), a lower base deficit (2.0+/-6.6 vs. 5.1+/-6.7 mmol/l), and a higher pH (7.40+/-0.12 vs. 7.36+/-0.12)
- mean APACHE II scores were significantly lower, indicating less severe organ dysfunction, in the patients assigned to EGDT
More recent studies could not replicate those findings (Yealy et al NEJM 2014; Peake et al. NEJM 2014)
75
What were the major findings of Conti-Patara A et al JVECC 2012 find in "Changes in tissue perfusion parameters in dogs with severe sepsis/septic shock in response to goal-directed hemodynamic optimization at admission to ICU and the relation to outcome" regarding ScvO2?
- prospective, observational study
- 30 dogs with severe sepsis or septic shock caused by pyometra who underwent surgery + admitted to ICU
- ScvO2, lactate, and base deficit on ICU admission were each related independently to death
- ScvO2 and base deficit were the best discriminators between survivors and nonsurvivors
76
Young et al. evaluated traditional global perfusion parameters versus ScvO2 in dogs with clinical shock in JVECC 2014. What were the main findings?
A significant proportion of dogs (38%) still had decreased ScvO2 following standard fluid therapy resuscitation and normalization of heart rate, blood pressure, mentation, and other clinical perfusion parameters.
77
What were the main findings of Hayes et al JSAP 2011 about ScvO2 in critically ill dogs?
- Low ScvO2 was associated with poor outcome
- A ScvO2 < 68% was associated with increased mortality risk - For each 10% drop in ScvO2 < 68%, odds of non-survival increased by 2·66 times
- ScvO2 was equivalent to lactate in predicting non-survival
78
Is ScvO2 a useful prognostic indicator in shock in dogs?
Yes
79
Is ScvO2 a useful prognostic indicator in shock in cats?
Studies are lacking
80
What are some limitations to SvO2 and ScvO2 measurement?
- hemoglobin concentration + SaO2 influence these variables
- loss of correlation between ScvO2 and SvO2 in very-low-flow states
- if underlying defect in oxygen extraction (e.g. sepsis) is present, SvO2 + ScvO2 can be normal or even high despite significant cellular oxygen debt
