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Weaning from CPB
Dr. S. Parthasarathy
MD., DA., DNB, MD (Acu),
Dip. Diab.DCA, Dip. Software statistics,
Phd (physio)
Mahatma Gandhi Medical college and
research institute , puducherry , India
• Weaning from CPB should represent a smooth
transition from the mechanical pump back to the
patient’s heart and lungs as the source of blood flow
and gas exchange
• Discontinuation – better word !!
• Coordinated --- surgeon, anaes, perfusionist
• This is simple write up !!
• Preop and intraop course – consider
What do we mean by that ??
When does it start ??
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Remove cross clamp !!
Blood starts to flow to coronaries
Heart starts to beat ??
It flushes out the metabolites and then start
De fib if needed – (10 or 20 J )
cold, decreased pressure , not protected well -- fibrillate !!
• Be ready for all the problems !
• What is this readiness ??
Romannof Royster CVP pneumonic
• C
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V
Cold
Ventilation
Conduction Visualization
Cardiac output Vaporizer
Cells
Volume expanders
Calcium
• Coagulation
P
Predictors
Pressure
Pressors
Pacer
Protamine
Potassium
The first “C” stands for “cold”
• patient's temperature at the time of weaning from CPB,
which should be 36°C to 37°C.
• Neither the temperature of the venous blood returning to
the CPB circuit nor nasopharyngeal temperature should
ever exceed 37°C because hyperthermia may increase the
risk for postoperative neurologic complications
• Nasopharyngeal Temp --- brain
• Rectum 2 degrees lower
• A larger than four degrees gradient between
the nasopharyngeal and rectal temperatures is
indicative of inadequate rewarming or
increased vasoconstriction
• Vasodilator ---- warming blankets – children
C for conduction – rate and the rhythm
• Rate - 80 to 100 beats/min
• Brady--- pacing or chronotropy with inotropy
• Need dromotropy also sometimes
tachycardia
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1) Hypoxia
(2) Hypercapnia
(3) Medications (inotropes, pancuronium, )
(4) Light anesthesia, awareness
“Fast track” anesthesia with its lower medication
additional dose of narcotic and benzodiazepine, or
hypnotic (propofol infusion) should be given during the
rewarming period or if tachycardia is present.
• (5) Anemia
• (6) ST and T-wave changes indicative of ischemia
Rhythm
• Sinus rhythm is preferable, particularly in patients with poor
LV compliance, who are especially dependent on an “atrial
kick” to achieve adequate filling.
• If supraventricular tachycardia is present, direct synchronized
cardioversion is often warranted.
• In addition, pharmacologic therapy with amiodarone,
esmolol, verapamil, or adenosine may be used in the initial
treatment
of
or
to
prevent
supraventricular tachycardia.
the
reoccurrence
of
• Stabilize parameters
• Defib
• Pacing
• Then only anti arrhythmic drugs
Cells
• The hemoglobin concentration should be measured
after rewarming.
• If it is less than 6.5 to 7 g/dL before terminating CPB-?? 10 gm is acceptable in many centres!
• 2 units of PRCs, 6 units ready
• Salvaged blood –ready.
• COPD, cyanosis ,residual stenosis, low output ---- aim
for higher hematocrit
“C” stands for “cardiac output” or
“contractility.”
• Following unclamping ,an adequate reperfusion period
must be permitted.
• allows the heart to replenish metabolic substrates,
specifically high-energy phosphates (ATP), and “washes
out” the products of anaerobic metabolism,
• Contractility may be estimated from TEE and cardiac
output can be measured with a PA catheter. -- 3 minutes
interval – ok??
Commonly encountered risk factors for
failure to wean from CPB include:
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poor preoperative ventricular function;
• urgent and emergency surgery;
• prolonged aortic cross-clamp time;
• inadequate myocardial protection;
• incomplete surgical repair.
DRUGS -------- ELECTRO-MECHANICAL
SUPPORT
• • Adrenergic agonists
• (Adrenaline,Dopamine
,Dobutamine,)
• • Phosphodiesterase
inhibitors
• (Milrinone)
• • Calcium sensitizer
• (Levosimedan)
• • Systemic vasodilators NTG,
• NPS)
• • Pulmonary vasodilator (NO,
• PGI2)
. • Bi-Ventricular pacing
• • Intra-Aortic Balloon Pump
• • Extra-Corporeal Membrane
• Oxygenation
• • Ventricular Assist Device
The fifth “C” stands for “coagulation
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the prothrombin time,
partial thromboplastin time,
platelet count
ACT ??
RISK ::
long CPB times;
extreme hypothermia,
chronic renal failure.
• Platelet function tests may be useful in
patients taking platelet inhibitors such as
clopidogrel or aspirin.
• See the field and drains – not the lab values
alone
Calcium
• The concentration of calcium in the plasma
may be reduced by large volumes of citrated
blood, leading to impaired contractility and
vasodilatation.
• Ionized calcium should be maintained above
1.0 mmol/l.
• Calcium – culprit in reperfusion injury –
correct only after establishing serum values
ALL “C “
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Cold
Conduction
Contractility
Calcium
Cells
Coagulation
V
Ventilation
• slowly occlude venous line
• blood into lungs
• Manual ventilation 100 % oxygen few puffs 30 cm
water – open up alveoli
• May continue ventilation as long as it doesnot
hinder surgeon
• Suction pleural space
• ICD in ??
• Anastamosis not stretched ??
• Compliance and bronchodilators
A venous oxygen saturation of 75% and a
minimum venous PO2 of 35mmHg are
satisfactory to start weaning from CPB.
The second “V” is for “visualization
both directly in the surgical field (where the
right-sided chambers are visible) and on TEE,
to estimate global and regional contractility
Blood volume
Air ??
Vaporizer
• Awareness
Vs
• Contractility
Vs
• Hypotension
• Use agent and vasopressors !! 0.7 MAC
isoflurane
• Some use 3 % iso on bypass also
• Analgesia , midazolam, relaxants
Volume
• When all products from the pump have been
exhausted and if blood transfusion is not indicated,
• crystalloid and albumin or hetastarch should be
readily available to rapidly increase preload if
necessary.
• Usually blood in the tubes taken out by us earlier
• Read CVP and MAP
V
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Ventilation
Vision
Vaporizer
Volume
P
Predictors
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Ejection is less
Cold
Long duration
Surgical repair ??
The second “P” is for “pressure.”
• Calibration and re zeroing are accomplished
shortly before starting to wean the patient
from CPB.
• Any discrepancy between distal (usually
radial) arterial pressure and central aortic
pressure should be recognized.
Pressors
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• Phenylephrine
• Norepinephrine
• Terlipressin
• Methylene Blue (1.5 mg/kg)
• Catecholamines
Pressors
• Low SVR -- norad or vasopressin
• Low cardiac output syndrome• Adrenaline , dopamine, dobutamine,
milrinone and levosimendan
“potassium”
• hypokalemia may contribute to dysrhythmias
• hyperkalemia may result in conduction abnormalities.
• Hypo more a common problem – patients on
diuretics
• Off bypass – usually in the range of 2.5
• magnesium (2 to 4 g) is generally administered before
CPB is terminated.
Parameters
• Administration of sodium bicarbonate
solution, usually into the cardiotomy reservoir
of the extracorporeal circuit, generates a
substantial amount of intracellular carbon
dioxide and is often associated with a
reduction in systemic vascular resistance.
• K+, Ca 2+, Mg2+ and acidosis
pH
• a pH of 7.4 and a PCO2 higher than 35 mmHg are
mandatory to safely disconnect a patient from the pump.
• Any degree of acidosis should promptly be corrected
because it depresses myocardial contraction, diminishes
the action of inotropes, and increases pulmonary vascular
resistance.
• Acidosis → sympathetic activity → beta blockers ( preop )
“protamine.”
• 3-4 mg/kg
• Or 1 mg for 100 units of heparin administered
• Slow
• Vasodilation
• Pulmonary vasoconstriction
pacing
• Epicardial pacing is commonly required in the
immediate and early post-CPB period.
• Atrial (AV node ok) , / ventricular ( chronic
AF)
• If cardiac function is adequate after weaning
from CPB, pacing may not prove necessary.
P
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Predictors
Pressure
Pressors
Pacing
Potassium
pH
Protamine
SVR
• Systemic vascular resistance (SVR) values are usually
assumed to be low following CPB
• because of the association between hemodilution
and reduction in SVR and because of the SIRS
• During CPB
• [MAP(mmHg)- RA (mmHg)]/pump flow (l/min) =
SVR (Wood Units)
• 900–1200 dyn.s/cm 5 .
de-airing
• Direct cardiac massage and syringing of left -sided chambers
and venting of the aorta or left -sided chambers is best
undertaken in a head down position, prior to, and after,
aortic unclamping.
• It is customary to ventilate the lungs during the de-airing
process in order to displace air that accumulates in the
pulmonary veins.
Air seen as white specks
Glucose (4.0–7.8 mmol/l)
• Tight glucose control in the postoperative period
has been shown by some investigators to
improve outcome after cardiac surgery.
• Hypoglycemia is rare except in liver diseases
• Lactate may be high (> 2.5 mmol/l) – usually no
treatment
Summarize
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Normal blood parameters - De airing – ACC off – ventilation
Support time – narrow complex, sinus, rate
Pressors
Load with progressive venous occlusion
No distension – load more
BP increase CVP no increase
Perfusionist – occlude aortic line – pump off
Protamine – protamine – assess
Remove venous line
Arterial line – ACT – blood
Separation
CPB : (v. cavae  oxygenator  aorta)
Partial bypass
(v. cavae  oxygenator + RV/lungs/LV  common
return to aorta)
Off CPB : (v. cavae  heart/lungs  aorta)
Transition should be smooth
• Any hiccups
• We may need to go
back to bypass
• More and more
complicated
• Pre and intra op
Thank you all