Transcript The Effects of CPB - cardiac anesthesia basics

The Effects of CPB
Brian Schwartz, CCP
November 5, 2002
Effects of CPB

To some degree or another, our patients
who undergo CPB may suffer some type
of injury.

The longer the bypass time….the better
chance of having some type of injury

Innovative products to help decrease the
incidence of injury
Membrane oxygenators
 Filters
 Bubble detectors
 Coated circuits

Areas that are Effected
The Lungs
The Kidneys
The Brain
The Compliment System
The Endocrine System
The Hepatic System
Effects on the Lungs
Considered to be the most serious injury
as a result of CPB
 By placing our patients on CPB the lungs
automatically undergo some type of
abnormal physiologic changes
 The lungs are subject to injury by the
activation of the blood compliment system
by coming into contact with foreign
substances

Lungs (continued)

Compliment Activation of both C3a and
C5a lead to the activation of leucocytes

Activation of Leucocytes

Leukoembolization may occur in the lungs
with the release of oxygen free radicals and
proteolytic enzymes released by the
neutrophils
Things we might see:

Pump Lung


Congested lungs with intraalveolar edema,
interstitial edema, and atelectasis
Atelectasis
Collapsed lung
 Smoking, chronic bronchitis, obesity, and
pulmonary edema predispose patients for
injury

Donor Blood

Any time donor blood is added to the
pump it should be filtered

It should be filtered mainly for leucocytes
Thrombocytopenia
Defined as low platelet count
 Platelet count usually decreases during
CPB, sometimes even below 50,000
 Because of such a low platelet count we
will see a large blood loss


Due to decreased amount of platelets and
function
Platelets (continued)

As the platelets are activated, they bind to
the tubing, sequestered in the lungs, the
spleen, and liver….all leading to
thrombocytopenia
Effects on the Kidneys

Another common effect of CPB is renal
dysfunction

Normally, 25% of the total C.O. is sent to
the kidneys. On pump this amount is
reduced due to: low flows and low
pressures
Blood flow to kidneys is effected by:

Composition of Prime

The sympathetic nervous system

Hormones
Epinephrine
 Angiotensin

Renal Failure

Acute renal failure


Nitrogen wastes accumulate in the blood
rapidly
Chronic renal failure
Urine decreases in amount and failure signs
begin…
 Increase in fluid intake doesn’t affect output,
mental status changes, seizures, GI bleeding,
and yellowing of the skin

Best Indicator of Failure

Acute renal failure
Nitrogen wastes accumulate in the blood
rapidly
 mg/100ml
 Elevated levels indicate creatine is not being
expelled in the urine

Reasons for poor function post-op
Long bypass run
 Poor pre-op function
 Addition of blood
 Exposure of angiographic dyes
 IABP

Neurological Effects
These results are usually permanent as a
result of an embolic event such as a CVA
or Stroke
 Embolus: defined as an air, blood clot, fat
or calcium debris
 Indicators of air embolism:

Seizures
 Cardiac arrythmias
 Ventricular dysfunction

CT Scan

Best method to determine extent of brain
injury
Ways to prevent neurological
injuries
Use filters
 CO2 flush circuit
 Watch temperature gradients
 Vent heart when clamp is off

Major causes of cerebral injury
Low flows
 Hypotension
 Low pCO2…which leads to
vasoconstriction of cerebral arteries
 High p02…which also leads to
vasoconstriction of cerebral arteries

Hematological Effects
Caused by exposing the patients to blood
products in the circuit
 Caused by using heparin
 Caused by hemodiluting the patients

Hematological Effects (continued)



Patients with pre-existing hematological
problems are at even more of a risk when
having heart surgery
Platelet dysfunction may be a result of diluting
the patients and the blood interaction between
air or pump circuit
Disseminated Intravascular Coagulation


Rare, but seen in long pump runs
Coagulation factors inappropriately activated and
bleeding occurs systemically
Effects on the Compliment System
CS involves complex proteins in the blood
that bind with antibodies against infection
and foreign bodies
 When activated, over 18 plasma proteins
are activated causing an immune
response

Activation of the CS

Release of anaphylatoxins that increase
vascular permeability (edema) and smooth
muscle contraction




C3a and C5a cause migration of neutrophils onto
walls of vessels
Arachidonic acid causes increase vascular
permeability
Chemotactic factors cause WBC’s to migrate to
the area causing inflammation
Release of enzymes and oxygen free radicals
that destroy tissue
Effects on the Endocrine System

A system on ductless glands that secrete
hormones directly into the blood
Adrenal: secretes epi/norepi
 Thyroid: secretes T-3 and T-4 for metabolism
 Pituitary: secretes vasopressin (ADH)
 Pancreas: secretes insulin
 Ovaries/Testis: maturation of eggs and sperm

Major Effect on Endocrine System
Insulin regulates the metabolism of
glucose and regulates the processes for
metabolism of fats, carb’s, and proteins
 Under hypothermic conditions the insulin
response in decreased and thus one’s
blood glucose levels increase. During the
re-warming phases of bypass the insulin
response increases.

Hepatic Effects
The liver is the largest organ in the body
 Consists of 4 lobes and supplied by 2
means

Hepatic artery- oxygen from the heart
 Hepatic portal vein-nutrient filled blood from
the stomach and intestines


Functions of the Liver

Processes glucose, proteins, and fats
Hepatic Injury
Patient becomes jaundice…excessive
bilirubin due to blood transfusions or blood
trauma.
 Jaundice may clear up by itself within a
week
 Elevated liver enzymes indicate injury
 As long as you keep your flows about an
2.2 index, hepatic oxygenation is
maintained and injury may be avoided
