Management of RV dysfunction after separation from CPB blue book article

Question 1

What is the precipitous spiral that can occur with RV failure?

Answer 1

RV failure
hypotension
further RV dysfunction
poor LV function & decreased systemic arterial pressure

Question 2

Which heart chamber can better tolerate sudden changes in afterload?

Answer 2

muscular LV

When faced with high afterload, the RV dilates, reducing it’s contractility & SV

Question 3

Which heart chamber better tolerates moderate increases in preload?

Answer 3

RV

Question 4

What does ventricular interdependence refer to?

Answer 4

how the size, shape & compliance of one ventricle affects the haemodynamic properties of the other. Main determinants= the inter ventricular septum (systolic interdependence), pericardium (diastolic interdependence) , shared blood supply & continuity of the myocardial fibres btwn RV & LV

Question 4

What does ventricular interdependence refer to?

Answer 4

how the size, shape & compliance of one ventricle affects the haemodynamic properties of the other. Main determinants= the inter ventricular septum (systolic interdependence), pericardium (diastolic interdependence) , shared blood supply & continuity of the myocardial fibres btwn RV & LV

Question 5

At greater than what RA pressure is RV dysfunction likely to be present?

Answer 5

8-10mmHg
or if RA:PCWP index is >=0.8 (higher= associated with higher PVR & reduced RV function) & the patient has a cardiac index of <2.2L/min/m2
These measures are in spont vent, non-sedated adults

Question 6

What measures raise suspicion of RVOTO?

Answer 6

RV to pulmonary artery pressure gradient of >25mmHg

Question 6

What measures raise suspicion of RVOTO?

Answer 6

RV to pulmonary artery pressure gradient of >25mmHg

Question 7

What’s cardiac index?

Answer 7

relates the CO from the LV in 1 minute to BSA, normal 2.5-4L/min/m2

Question 8

What are the risk factors for developing post-CPB RV failure?

Answer 8

pre-existing RV dysfunction
pulmonary HTN
long CPB times
LVAD insertion (RV failure post LVAD insertion occurs in 20-40% of cases)
heart transplantation (particularly if the donor heart had a long ischaemic time or if mismatched in size)
inadequate myocardial protection (provided while on CPB with cardioplaegia, flooding the surgical field with CO2)
protamine (pulmonary HTN increasing RV afterload is a known side effect)
any obstruction to R) coronary blood flow- a common etiology= inadequate de-airing of the LV prior to coming off CPB. Other aetiologies of decreased flow through R) CA include failed grafting, suturing, occlusion of coronary Ostia during valve surgery, acute thrombus at Ostia or RCA lumen.

Question 9

Strategies to limit the risk of RV dysfunction

Answer 9

optimise ABG (avoid acidaemia, hypoxaemia & hypercapnia) & ventilatory (avoid excess TVs & PEEP) settings to avoid pulm VC

delivery of pulmonary vasodilators, which may be commenced pre-bypass in susceptible pts (eg, those with pre-existing RV dysfunction, pulm HTN, LVAD or heart transplant). Eg. NO, via insp limb of anaesthetic circuit from specific NO delivery system, concentrations monitored & controlled in ppm (starting at 10-20ppm, increasing to 40ppm as desired).
Other options= inhaled milrinone, inhaled prostacyclin such as epoprostenol & iloprost.

aggressive de-airing prior to weaning off CPB.

Question 10

What’s an advantage over inhaled iloprost vs milrinone and epoprostenol?

Answer 10

iloprost is easier to administer. Doesn’t need to be a continuous infusion (unlike NO & epoprostenol)

Question 11

What’s a problem with epoprostenol? how to overcome

Answer 11

may cause bleeding due to anti platelet activity

this complication is seen less with inhaled vs IV epoprostenol

Question 12

Why is CO2 embolism less significant than air?

Answer 12

dissolves more rapidly

Question 13

Does ejection fraction form part of the routine TOE examination of the RV?

Answer 13

no

Question 14

what is the recommended ASE assessment of RV function?

Answer 14

RV size (volumetric quantification is challenging, visual estimation is common)
RA size
systolic PA pressure (estimate RA pressure using IVC dimensions)
a measure of RV systolic function, either FAC, TAPSE, tricuspid annulus peak velocity +/- RV index of myocardial performance.

Question 15

How many mid-oesophageal views are there?

Answer 15

15

Question 15

How many mid-oesophageal views are there?

Answer 15

15

Question 16

How many transgastric views are there on TOE?

Answer 16

9 (looking through diaphragm to heart)

Question 17

How many aortic views are there on TOE?

Answer 17

4

Question 18

What does the mid-oesophageal view of the RA allow?

Answer 18

interrogation through the TCV to the RV apex, allowing assessment of the apical portion of the anterior RV free wall

Question 19

What does the deep transgastric view of the RA allow?

Answer 19

representation of the RV inferior wall, with ante flexion of the probe can view the RV inflow tract & pulmonary valve

Question 20

How is the RA best visualised on echo?

Answer 20

mid-oesophageal 4-chamber view, mid-oesophageal RV inflow/outflow view & bicaval view

Question 21

How are the pulmonary valve & arteries best viewed on TOE? how to assess flow characteristics?

Answer 21

mid oesophageal RV inflow-outflow view (pulmonary valve) & upper oesophageal views (pulmonary arteries)
doppler

Question 22

Given that a comprehensive RV TOE assessment is not feasible when weaning from CPB, a focused exam should be performed comprising of what?

Answer 22

assess RV free wall, septal wall, RV inflow tract, RV outflow tract, TAPSE

Question 23

what's an abnormally thick RV free wall?

Answer 23

>0.5cm

Question 24

What's abnormal RVEF?

Answer 24

<45%

Question 25

what's abnormal pulsed doppler peak tricuspid annulus velocity?

Answer 25

<9.5cm/s

Question 26

What represents high RA pressure?

Answer 26

>5mmHg

Question 27

What represents high tricuspid regurgitation velocity?

Answer 27

>2.8m/s

Question 28

What represents high systolic pulmonary artery pressure?

Answer 28

>35mmHg

Question 29

While there's no agreed perfect index of RV function, what are the most useful views to rapidly assess RV dysfunction? other TOE features indicating RV failure?

Answer 29

mid-oesophageal 4-chamber view RV inflow-outflow view to analyse TAPSE placing colour flow doppler across tricuspid valve to assess for new/worsening TCR Evidence of increased RA pressure (eg. bowing of inter-atrial septum, dilated IVC with reduced collapsibility) incr RV to LV size ratio >0.6 flattened or L)-deviation of IV septum (usually convex to RV)

Question 30

How may cardiac surgery confound measures of TAPSE & tricuspid annulus peak velocity (S')?

Answer 30

CPB & chest closure decrease these measurements

Question 31

What are some CVP parameters that may indicate failing RV?

Answer 31

CVP (surrogate for RA pressure) >20mmHg CVP > PCWP cardiac index <2.1L/min/m2 fusion of c & v waves implies new TCR & failing RV

Question 31

What are some CVP parameters that may indicate failing RV?

Answer 31

CVP (surrogate for RA pressure) >20mmHg CVP > PCWP cardiac index <2.1L/min/m2 fusion of c & v waves implies new TCR & failing RV

Question 32

What's the diastolic slope of the RV pressure waveform in a normal RV? what happens as RV dysfunction occurs?

Answer 32

almost horizontal begins to upslope as RV function deteriorates further, it takes a square root shape finally there's equalisation of the RV & PA diastolic pressures with severe RV failure, there's delay in systolic upstroke & RV pulse pressure reduces

Question 33

What's the pulmonary artery pulsatility index (PAPi)?

Answer 33

a new measure in assessment of RV dysfunction, particularly post RV infarction, advanced HF, cariogenic shock & LVAD implantation PAPi = (systolic PAP - diastolic PAP) / RAP thresholds not established

Question 34

How should management of RV preload be managed when coming off CPB?

Answer 34

If the RV has normal afterload, fluid loading will assist in maintaining SV. If R)-sided filling pressures are low (CVP <15mmHg & RV is not dilated on TOE), judiciously volume load. If RV has high afterload, fluid loading will cause L)-shift of the RV, ventricular interdependence comes into play & reduced LV filling & SV ensues. If RV preload is elevated, reduce by encouraging venous pooling; raise head of table or start GTN infusion to dilate capacitance vessels. could reduce preload by asking perfusionist to empty blood into the bypass circuit via aortic cannula. maintain sinus & treat any high-degree AV block; pacing useful to reduce worsening haemodynamic function. If the RV is hypertrophied & non-compliant in the setting of pulm HTN, it relies on the atrial kick- atrial epicardial leads could be placed. prioritise conversion to sinus with electrical or chemical means (supraventricular arrhythmias poorly tolerated)

Question 35

what are causes of high afterload coming off bypass? how to mitigate risks?

Answer 35

``` atelectasis academia reperfusion injury endothelial damage & release of inflammatory mediators hypoxia, hypercapnia hypothermia ``` ABG, ensure no acidosis PiO2 100% set ventilator to avoid hypercarbia or excess TVs & PEEP (gentle ventilatory recruitment to promote parenchymal lung blood vessel opening) warm consider inhaled pulmonary VDs once ventilatory & physiological parameters addressed (NO, prostacyclin, iloprost, milrinone)

Question 36

Advantages of inhaled vs systemic pulm vasodilators?

Answer 36

reduce PVR with less systemic hypoT & V/Q mismatch

Question 37

How increase RV contractility coming off bypass? side benefit? other option?

Answer 37

dobutamine: increases RV contractility & lowers PVR milrinone is an alternative but may produce more profound systemic hypoT vs dobutamine which risks impaired coronary perfusion & spiral of RV dysfunction May offset hypotension with these inotropes with vasopressor (NAdr low-dose or vasopressin)

Question 38

What's 1st line for sudden post-CPB severe RV failure?

Answer 38

adrenaline. significantly improves RV EF. | other option for post-CPB RV failure is intratracheal milrinone 5mg- efficacy of 60% in restoring RV function.

Question 39

Best drug to use for the vital role of maintaining systemic BP to sustain R) coronary perfusion?

Answer 39

vasopressin: minimal effects on PVR but increases SVR

Question 40

Best drug to use for the vital role of maintaining systemic BP to sustain R) coronary perfusion?

Answer 40

vasopressin: minimal effects on PVR but increases SVR

Question 41

Order of management for RV failure coming off CPB?

Answer 41

assess RV preload. If CVP <15mmHg & RV not dilated on echo, give small fluid challenge (eg. pump blood) if preload high, lower by head up or removing blood from circulation in to CPB circuit, commence GTN if these measures inadequate concurrently, have a vasopressor (ideally vasopressin) running to support coronary perfusion increase RV contractility with dobutamine, consider adrenaline or milrinone if haemodynamic compromise, consider add small boluses or intratracheal 5mg milrinone maintain SR & AV synchrony (cardioversion chemically or electrically, AV pacing consider inhaled pulm VD for raised PA pressures or IV unresponsive cases with severe haemodynamic instability, consider a return to CPB (which may incr M&M), IABP to promote RCA flow or V-A ECMO or RVAD can be considered.