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The kidneys
Location
-The kidneys are a pair of organs located in the back of
the abdomen.
- Each kidney is about 4 or 5 inches long -- about the
size of a fist.
-more specifically in the paravertebral gutter and lie
in a retroperitoneal position at a slightly oblique
angle. There are two, one on each side of the spine
-The left kidney is approximately at the vertebral level
T12 to L3 and the right slightly lower.
-The right kidney sits just below the diaphragm and
posterior to the liver, the left below the diaphragm and
posterior to thespleen.
The asymmetry within the abdominal cavity caused by
the liver typically results in the right kidney being slightly
lower than the left, and left kidney being located slightly
more medial than the right
Anatomy of the Kidney
Functions:
- The kidney participates in the excretion of the body wastes-regulating acid-base balance,
-regulating electrolyte concentrations .
-regulating extracellular fluid volume .
- regulation of blood pressure.
-Hormone secretion (including
- erythropoietin( It stimulates (production of red blood cells) in
the bone marrow),
-the enzyme renin (Part of the renin-angiotensin-aldosterone system ,
renin is an enzyme involved in the regulation of aldosterone levels.
-Calcitriol, the activated form of vitamin D, promotes intestinal
absorption of calcium and the renal reabsorption of phosphate
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Structure and Function of the
Kidney
The functional unit of the kidney is the nephron •
The major functions of the kidney are to maintain •
extracellular fluids, to eliminate wastes resulting
from normal metabolism, and to excrete xenobiotics
and their metabolites
Mammalian kidneys have 10,000-1,000,000 •
nephrons per kidney
Renal toxicology
Structure and Function of the
Kidney (cont)
The glomerulus yields an ultrafiltrate of plasma that
represents 20% of the renal blood flow, ie. 2-3% of cardiac
output
Endothelial surface is negatively charged and contains
fenestrae
The glomerular basement membrane is sandwiched between
the epithelial cells and contains anionic sialoglycoproteins,
glycoproteins and collagen IV
The mesangium provides support
The outer capsule is Bowman’s capsule
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Structure and Function of the
Kidney (cont)
The tubule resorbs greater than 99% of the glomerular
filtrate
The proximal tubule has extensive resorption and
selective secretion (convoluted - S1 and S2, straight - S3).
S2 is primary site for low MW protein resorption and S3 is
primary site for P450.
Thin loop of Henle - resorption of fluids
Distal tubule - resorption of fluids and acid-base balance
Collecting duct - resorption of fluids, antidiuretic hormone
and acid-base balance
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Medullary
ray
P2
P2
Cortical
labyrinth
P1 / P2
P1
P3
Cortex
Outer
Medulla
P3
DT
Outer
Stripe
Inner
Stripe
TLH
CD
Inner
Medulla
Short et al., Laboratory Investigation,564-577 (1987).
Structure and Function of the
Kidney (cont)
Produces erythropoietin, which regulates RBC •
production
Hydroxylates 25-OH-cholecalciferol (vitamin D •
metabolite), to promote bone resorption and
calcium and phosphorus absorption from the gut
Releases renin to regulate the peripheral renin- •
angiotensin-aldosterone system (juctaglomerular
apparatus)
Assessment of Kidney Function:
Morphologic Evaluation
Urinalysis
Gross evaluation of the kidney at necropsy
Histopathology of the kidney
Electron microscopy of the kidney
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Assessment of Kidney Function:
Urinalysis
Proteinuria - indicates glomerular damage
Glycosuria - indicates tubular damage
Urine volume and osmolarity
pH
Enzymes - indicates tubular damage
Microscopic examination - casts, crystals,
bacteria, etc.
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Assessment of Kidney Function:
Blood Chemistries
Blood urea nitrogen (BUN)
Creatinine
Electrolytes - Ca, Mg, K, P
Glomerular filtration rate - determines the
clearance of inulin, creatinine and BUN
Renal clearance - measures the clearance of paminohippuric acid by filtration and secretion
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Glomerular Disease: Toxicities due to
Alteration of Anionic Charge
Hexadimethrine - polycationic molecule •
reduces anionic charge, which permits
escape of anionic molecules such as
albumin and IgG
Polynucleoside of puromycin - damages •
epithelial foot processes
Glomerular Disease:
Immune Complex Disease
Anti-GBM mediated glomerulonephritis is •
induced by heterologous antibodies
Antibodies due to exogenous antigens - •
cationized molecules such as lysozyme, IgG
and BSA bind to anionized surfaces;
Concanavalin A binds to sugars in the GBM
Glomerular Disease:
Immune Complex Disease (cont)
Deposition of circulating immune complexes
Drug or toxin-induced T-cell dependent polyclonal B- •
cell activation - mercury in Brown Norway rats
Unknown mechanism - gold salts, D-penicillamine, •
hydralazine
Antibodies to heterologous proteins - safety •
evaluations of recombinant proteins in laboratory
animals
Nephrosis:
Damage to the renal tubule
Halogenated hydrocarbons - chloroform,
hexachlorobutadiene, trichloroethylene,
dibromochloropropane, & bromobenzene
Heavy metals - cadmium, mercury & lead
Antibiotics - cephalosporins &
aminoglycosides
Mycotoxins - ochratoxin A & citrinin
Ethylene glycol
Antineoplastic drugs - cisplatinum
Alpha2u-globulin nephropathy
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Haloalkane Nephrosis
Chloroform is metabolized by P450 to an
electrophile, phosgene, which is a potent
cytotoxicant.
Carbon tetrachloride is metabolized to free radicals
and phosgene.
P450 is localized in the proximal tubule.
This results in nephrosis with necrosis, enzyme,
glucose and protein excretion in urine, and increased
BUN and creatinine concentrations in serum.
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Haloalkene Nephrotoxicity
1,1-Dichloroethylene, trichloroethylene and •
tetrachloroethylene are metabolized by P450
to electrophilic metabolites and or free
radicals.
These metabolites can be cytotoxic and/or •
genotoxic.
Nephrotoxicity is exacerbated when •
glutathione is depleted.
Glutathione-mediated Nephrosis
Glutathione conjugates of haloalkanes can •
form episulfonium ions.
Primary route for 1,2-dichloroethane, 1,2- •
dibromoethane and 1,2-dibromo-3-chloropropane.
These can alkylate macromolecules and cause •
cytotoxicity and genotoxicity.
Cystine Conjugate -lyase Activation
Stable cystine conjugates from glutathione can •
be formed in the liver from trichloro-ethylene,
tetrafluoroethylene and hexa-chlorobutadiene
and transported to the kidney.
They are further metabolized by -lyase in the •
kidney to generate reactive thiols.
Dialysis unit
is a process for removing waste and excess water from the blood, and is used
primarily to provide an artificial replacement for lost kidney function in people
with renal failure
Indications of dialysis in acute renal failure (ARF)
-Severe fluid overload
-Refractory hypertension
-Uncontrollable hyperkalemia
-Nausea, vomiting, poor appetite, gastritis with hemorrhage
Lethargy, malaise, somnolence, stupor, coma, delirium, asterixis, tremor,
seizures,
-Pericarditis (risk of hemorrhage or tamponade)
-bleeding diathesis (epistaxis, gastrointestinal (GI) bleeding and etc.)
-Severe metabolic acidosis
- Intoxication, that is, acute poisoning with a dialysable drug, such as
lithium, or aspirin.
-Blood urea nitrogen (BUN) > 70 – 100 mg/dl
Indications of dialysis in chronic renal failure (CRF)
-Pericarditis
- Fluid overload or pulmonary edema refractory to diuretics
-Accelerated hypertension poorly responsive to antihypertensives
-Progressive uremic encephalopathy or neuropathy such as confusion,
asterixis,-myoclonus, wrist or foot drop, seizures
-Bleeding diathesis attributable to uremia
Types of Dialysis
-hemodialysis (primary) .
-peritoneal dialysis (primary) .
- hemofiltration (primary) .
- hemodiafiltration (secondary) .
- intestinal dialysis(secondary).
Hemodialyzer
the patient's blood is pumped through the blood compartment of a
dialyzer, exposing it to a partially permeable membrane
Blood flows through the dialyzer, dialysis solution flows around the
outside of the fibers, and water and wastes move between these two
solutions by applying negative pressure ,The cleansed blood is then
returned via the circuit back to the body
Advantages
four dialysis-free days a week.
Facilities are widely available.
Trained professionals are with you
at all times.
You can get to know other
patients.
You don’t have to have a partner
or keep equipment in your home.
Disadvantage
If you travel to another country, you
will have to pre-arrange access to
dialysis facilities
your diet and the amount of fluid that
you drink needs to be restricted
You are advised not to drink more
than a couple of cups of fluid a day
You have to avoid foods that are
high in potassium
Peritoneal dialyzer
In peritoneal dialysis, a sterile solution containing glucose is run
through a tube into the peritoneal cavity, the abdominal body cavity
around theintestine, where the peritoneal membrane acts as a
partially permeable membrane
The dialysate is left there for a period of time to absorb waste
products, and then it is drained out through the tube and discarded.
This cycle or "exchange" is normally repeated 4-5 times during the day,
(sometimes more often overnight with an automated system)
Advantages
- regular visits to a dialysis unit are
not required and, in the case of home
haemodialysis, there is no need to
have a bulky machine installed in your
house
more freedom to travel compared
with haemodialysis patients.
fewer restrictions on diet and fluid
intake compared with haemodialys
Disadvantage
you need to perform it every day,
whereas haemodialysis is usually
only performed three days a week.
major disadvantage of peritoneal
dialysis is that your risk of
developing peritonitis (infection of
the peritoneum) is increased.
Peritonitis causes symptoms that
include:
abdominal pain
vomiting
chills (episodes of shivering and cold)
reduction in protein levels, which can
lead to a lack of energy and in some
cases malnutrition.
Hemofiltration
Hemofiltration is a similar treatment to hemodialysis, but it makes use of a
different principle.
The blood is pumped through a dialyzer or "hemofilter" as in dialysis, but no
dialysate is used.
- A pressure gradient is applied; as a result, water moves across the very
permeable membrane rapidly, "dragging" along with it many dissolved
substances, including ones with large molecular weights, which are not cleared
as well by hemodialysis.
Salts and water lost from the blood during this process are replaced with a
"substitution fluid" that is infused into the extracorporeal circuit during the
treatment.
Hemodiafiltration
Hemodiafiltration is a term used to describe several methods of
combining hemodialysis and hemofiltration in one process.
Intestinal dialysis
In intestinal dialysis, the diet is supplemented with soluble fibres such
as acacia fibre, which is digested by bacteria in the colon.
This bacterial growth increases the amount of nitrogen that is
eliminated in fecal waste
An alternative approach utilizes the ingestion of 1 to 1.5 liters of nonabsorbable solutions of polyethylene glycol or mannitol every fourth
hour.
Electric cardioversion
a medical procedure by which an abnormally fast heart rate or cardiac
arrhythmia is converted to a normal rhythm, using electricity
The purpose of the cardioversion is to interrupt the abnormal electrical
circuit(s) in the heart and to restore a normal heartbeat.
The delivered shock causes all the heart cells to contract
simultaneously, thereby interrupting and terminating the abnormal
electrical rhythm (typically fibrillation of the atria) without damaging
the heart.
two electrode pads are used
These are connected by cables to a machine which has the combined
functions of an ECG display screen and the electrical function of
a defibrillator
Indications:
- Synchronized electrical cardioversion is used to treat hemodynamically significant supraventricular tachycardias,
including atrial fibrillation and atrial flutter. It is also used in the
emergent treatment including ventricular tachycardia, when a pulse is
present.
-Pulseless ventricular tachycardia and ventricular fibrillation are treated
with unsynchronized shocks referred to as defibrillation.
Ventialtor
a machine designed to mechanically move breatheable air into and out of the
lungs, to provide the mechanism of breathing for a patient who is physically
unable to breathe, or breathing insufficiently.
Indications :
-Acute lung injury (including ARDS, trauma)
- Apnea with respiratory arrest, including cases from intoxication
-Chronic obstructive pulmonary disease (COPD)
-Acute respiratory acidosis with partial pressure of carbon dioxide
(pCO2) > 50 mmHg and pH < 7.25, which may be due to paralysis of
the diaphragm due to Guillain-Barré syndrome,Myasthenia
Gravis, spinal cord injury, or the effect of anaesthetic and muscle
relaxant drugs
-Increased work of breathing as evidenced by significant tachypnea,
retractions, and other physical signs of respiratory distress
Lateral Sclerosis
-Hypoxemia with arterial partial pressure of oxygen (PaO2) < 55 mm Hg
with supplemental fraction of inspired oxygen (FiO2) = 1.0
-Hypotension including sepsis, shock, congestive heart failure
Neurological diseases such as Muscular Dystrophy and Amyotrophic
Disadvantages:
It carries many potential complications including pneumothorax, airway
injury, alveolar damage, and ventilator-associated pneumonia.
It is used to support a single failing organ system (the lungs) and
cannot reverse any underlying disease process (such as terminal
cancer)
Cardiac Assist Devices
Wayne E. Ellis, Ph.D., CRNA
Types
Pacemakers
AICDs
VADs
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History
First pacemaker implanted in 1958
First ICD implanted in 1980
Greater than 500,000 patients in the US
population have pacemakers
115,000 implanted each year
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Pacemakers Today
Single or dual chamber
Multiple programmable features
Adaptive rate pacing
Programmable lead configuration
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Internal Cardiac Defibrillators
(ICD)
Transvenous leads
Multiprogrammable
Incorporate all capabilities of contemporary
pacemakers
Storage capacity
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Temporary Pacing Indications
Routes = Transvenous, transcutaneous, esophageal •
Unstable bradydysrhythmias •
Atrioventricular heart block •
Unstable tachydysrhythmias •
*Endpoint reached after resolution of the problem or •
permanent pacemaker implantation
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Permanent Pacing Indications
Chronic AVHB
Chronic Bifascicular and Trifascicular Block
AVHB after Acute MI
Sinus Node Dysfunction
Hypersensitive Carotid Sinus and Neurally Mediated
Syndromes
Miscellaneous Pacing Indications
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Chronic AVHB
Especially if symptomatic •
Pacemaker most commonly indicated for:
Type 2 2º •
Block occurs within or below the Bundle of His –
3º Heart Block •
No communication between atria and ventricles –
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Chronic Bifascicular and
Trifascicular Block
Differentiation between uni, bi, and •
trifascicular block
Syncope common in patients with •
bifascicular block
Intermittent 3º heart block common •
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AVHB after Acute MI
Incidence of high grade AVHB higher •
Indications for pacemaker related to •
intraventricular conduction defects rather
than symptoms
Prognosis related to extent of heart damage •
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Sinus Node Dysfunction
Sinus bradycardia, sinus pause or arrest, or
sinoatrial block, chronotropic incompetence
Often associated with paroxysmal SVTs
(bradycardia-tachycardia syndrome)
May result from drug therapy
Symptomatic?
Often the primary indication for a pacemaker
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Hypersensitive Carotid Sinus
Syndrome
• Syncope or presyncope due to an
exaggerated response to carotid sinus
stimulation
• Defined as asystole greater than 3 sec due to
sinus arrest or AVHB, an abrupt reduction of
BP, or both
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Neurally Mediated Syncope
10-40% of patients with syncope •
Triggering of a neural reflex •
Use of pacemakers is controversial since •
often bradycardia occurs after hypotension
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Miscellaneous
Hypertrophic Obstructive Cardiomyopathy
Dilated cardiomyopathy
Cardiac transplantation
Termination and prevention of
tachydysrhythmias
Pacing in children and adolescents
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Indications for ICDs
Cardiac arrest due to VT/VF not due to a transient or
reversible cause
Spontaneous sustained VT
Syncope with hemodynamically significant sustained VT
or VF
NSVT with CAD, previous MI, LV dysfunction and
inducible VF or VT not suppressed by a class 1
antidysrhythmic
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Device Selection
Temporary pacing (invasive vs. noninvasive) •
Permanent pacemaker •
ICD •
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Pacemaker Characteristics
• Adaptive-rate pacemakers
•Single-pass lead Systems
• Programmable lead configuration
• Automatic Mode-Switching
• Unipolar vs. Bipolar electrode configuration
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ICD selection
Antibradycardia pacing
Antitachycardia pacing
Synchronized or nonsynchronized shocks for
dysrhythmias
Many of the other options incorporated into
pacemakers
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Approaches to Insertion
a. IV approach (endocardial lead)
b. Subcostal approach (epicardial or myocardial
lead)
c. Noninvasive transcutaneous pacing
Alternative to emergency transvenous pacing
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Mechanics
 Provide the rhythm heart cannot produce
 Either temporary or permanent
 Consists of external or internal power
source and a lead to carry the current to
the heart muscle
 Batteries provide the power source
 Pacing lead is a coiled wire spring encased in silicone to
insulate it from body fluids
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Unipolar Pacemaker
Lead has only one electrode that contacts the
heart at its tip (+) pole
The power source is the (-) pole
Patient serves as the grounding source
Patient’s body fluids provide the return
pathway for the electrical signal
Electromagnetic interference occurs more often
in unipolar leads
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Unipolar Pacemaker
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Bipolar Pacemaker
If bipolar, there are two wires to the heart or
one wire with two electrodes at its tip
Provides a built-in ground lead
Circuit is completed within the heart
Provides more contact with the endocardium;
needs lower current to pace
Less chance for cautery interference
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Bipolar Pacemaker
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Indications
1. Sick sinus syndrome (Tachy-brady
syndrome)
2. Symptomatic bradycardia
3. Atrial fibrillation
4. Hypersensitive carotid sinus syndrome
Second-degree heart block/Mobitz II .5
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Indications
6. Complete heart block
Sinus arrest/block .7
Tachyarrhythmias .8
Supraventricular, ventricular
To overdrive the arrhythmia
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Atrial Fibrillation
* A fibrillating atrium cannot be paced
* Place a VVI
* Patient has no atrial kick
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Types
1. Asynchronous/Fixed Rate
2. Synchronous/Demand
3. Single/Dual Chamber
Sequential (A & V)
4. Programmable/nonprogrammable
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Asynchronous/Fixed Rate
 Does not synchronize with intrinsic HR
 Used safely in pts with no intrinsic
ventricular activity
If pt has vent. activity, it may compete
with pt’s own conduction system
VT may result (R-on-T phenomenon)
EX: VOO, AOO, DOO
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Synchronous/Demand
Contains two circuits
* One forms impulses
* One acts as a sensor
When activated by an R wave, sensing circuit
either triggers or inhibits the pacing circuit
Called “Triggered” or “Inhibited” pacers
Most frequently used pacer
Eliminates competition;
Energy sparing
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Examples of Demand Pacemakers
DDI
VVI/VVT
AAI/AAT
Disadvantage: Pacemaker may be fooled by
interference and may not fire
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Dual Chamber: A-V
Sequential
Facilitates a normal sequence between atrial
and ventricular contraction
Provides atrial kick + ventricular pacing
Atrial contraction assures more complete
ventricular filling than the ventricular
demand pacing unit
Increase CO 25-35% over ventricular pacing
alone
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A-V Sequential
Disadvantage: More difficult to place
More expensive
Contraindication: Atrial fibrillation, SVT
Developed due to inadequacy of “pure atrial
pacing”
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Single Chamber
Atrial
Ventricular
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“Pure Atrial Pacing”
Used when SA node is diseased or damaged
but AV conduction system remains intact
Provides atrial kick
Atrial kick can add 15-30% to CO over a
ventricular pacemaker
Electrode in atrium: stimulus produces a P
wave
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Problems with Atrial Pacing
Electrode difficult to secure in atrium
Tends to float
Inability to achieve consistent atrial “demand”
function
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Ventricular Pacemakers
If electrode is placed in right ventricle, stimulus
produces a left BBB pattern
If electrode is placed in left ventricle, stimulus
produces a right BBB pattern
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Programmability
Capacity to noninvasively alter one of several aspects of the
function of a pacer
Desirable since pacer requirements for a person change over
time
Most common programmed areas
Rate
Output
AV delay in dual chamber pacers
R wave sensitivity
Advantage: can overcome interference
caused by electrocautery
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3-Letter or 5-Letter Code
 Devised to simplify the naming of
pacemaker generators
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First letter
Indicates the chamber being paced
A: Atrium
V: Ventricle
D: Dual (Both A and V)
O: None
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Second Letter
Indicates the chamber being sensed
A: Atrium
V: Ventricle
D: Dual (Both A and V)
O: Asynchronous or does not apply
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Third Letter
Indicates the generator’s response to a sensed
signal/R wave
I: Inhibited
T: Triggered
D: Dual (T & I)
O: Asynchronous/ does not apply
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Fourth Letter
Indicates programming information
O: No programming
P: Programming only for output and/or rate
M: Multiprogrammable
C: Communicating
R: Rate modulation
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Fifth Letter
This letter indicates tachyarrhythmia functions
B: Bursts
N: Normal rate competition
S: Scanning
E: External
O: None
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Table of Pacer Codes
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Types of Pulse
Generators
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Examples
AOO
A: Atrium is paced
O: No chamber is sensed
O: Asynchronous/does not apply
VOO
V: Ventricle is paced
O: No chamber is sensed
O: Asynchronous/does not apply
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Examples
VVI
V: Ventricle is the paced chamber
V: Ventricle is the sensed chamber
I: Inhibited response to a sensed signal
Thus, a synchronous generator that paces and
senses in the ventricle
Inhibited if a sinus or escape beat occurs
Called a “demand” pacer
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Examples
DVI
D: Both atrium and ventricle are paced
V: Ventricle is sensed
I: Response is inhibited to a sensed
ventricular signal
For A-V sequential pacing in which atria and
ventricles are paced. If a ventricular signal,
generator won’t fire
Overridden by intrinsic HR if faster
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Examples
DDD
Greatest flexibility in programming
Best approximates normal cardiac response to exercise
DOO
Most apparent potential for serious ventricular arrhythmias
VAT
Ventricular paced, atrial sensed
Should have an atrial refractory period programmed in to
prevent risk of arrhythmias induced by PACs from ectopic
or retrograde conduction
AV interval is usually 150-250 milliseconds
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Other Information
Demand pacer can be momentarily converted to
asynchronous mode by placing magnet externally over
pulse generator in some pacers
Dual chamber pacers preferable for almost all patients except
those with chronic atrial fibrillation (need a working
conduction system)
Asynchronous pacer modes not generally used outside the OR
OR has multiple potential sources of electrical interference which may
prevent normal function of demand pacers
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Other Information
VVI: Standard ventricular demand pacemaker
DVI: AV pacemaker with two pacing electrodes
Demand pacer may be overridden by intrinsic
HR if more rapid
Demand pacer can be momentarily converted to
asynchronous mode by placing magnet
externally over pulse generator
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Sensing
Ability of device to detect intrinsic cardiac
activity
Undersensing: failure to sense
Oversensing: too sensitive to activity
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Undersensing: Failure to
sense
Pacer fails to detect an intrinsic rhythm
Paces unnecessarily
Patient may feel “extra beats”
If an unneeded pacer spike falls in the latter
portion of T wave, dangerous
tachyarrhythmias or V fib may occur (R on
T)
TX: Increase sensitivity of pacer
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Oversensing
Pacer interprets noncardiac electrical signals as
originating in the heart
Detects extraneous signals such as those
produced by electrical equipment or the
activity of skeletal muscles (tensing, flexing
of chest muscles, SUX)
Inhibits itself from pacing as it would a true
heart beat
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Oversensing
On ECG: pauses longer than the normal
pacing interval are present
Often, electrical artifact is seen
Deprived of pacing, the patient suffers  CO,
feels dizzy/light-headed
Most often due to sensitivity being
programmed too high
TX: Reduce sensitivity
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Capture
Depolarization of atria and/or ventricles in
response to a pacing stimulus
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Noncapture/Failure to Capture
Pacer’s electrical stimulus (pacing) fails to
depolarize (capture) the heart
There is no “failure to pace”
Pacing is simply unsuccessful at stimulating a
contraction
ECG shows pacer spikes but no cardiac response
 CO occurs
TX:  threshold/output strength or duration
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Pacer Failure
A. Early
electrode displacement/breakage
B. Failure > 6 months
Premature battery depletion
Faulty pulse generator
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Pacer Malfunctions per ECG
 Failure to capture
 Failure to sense
 Runaway pacemaker
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Pacer Malfunction SX
1. Vertigo/Syncope
*Worsens with exercise
2. Unusual fatigue
3. Low B/P/  peripheral pulses
4. Cyanosis
5. Jugular vein distention
6. Oliguria
7. Dyspnea/Orthopnea
8. Altered mental status
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EKG Evaluation
Capture: Should be 1:1
(spike:EKG complex/pulse)
*Not helpful if patient’s HR is >
pacer rate if synchronous type
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EKG Evaluation
Proper function of demand pacer
Confirmed by seeing captured beats on EKG when
pacer is converted to asynchronous mode
Place external converter magnet over generator
Do not use magnet unless recommended
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CAPTURE
Output: amt of current (mAmps) needed to get
an impulse
Sensitivity: (millivolts); the lower the setting,
the more sensitive
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Anesthesia for Insertion
MAC
To provide comfort
To control dysrhythmias
To check for proper function/capture
Have external pacer/Isuprel/Atropine ready
Continuous ECG and peripheral pulse
Pulse ox with plethysmography to see
perfusion of each complex
(EKG may become unreadable)
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Pacemaker Insertion
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Interference
Things which may modify pacer function:
Sympathomimetic amines may increase myocardial
irritability
Quinidine/Procainamide toxicity may cause failure
of cardiac capture
 K+, advanced ht disease, or fibrosis around
electrode may cause failure of cardiac capture
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Anesthesia for Pt with
Pacemaker
a. Continuous ECG and peripheral pulse
b. Pulse ox with plethysmography to
see perfusion of each complex
(EKG may become unreadable)
c. Defibrillator/crash cart available
d. External pacer available
e. External converter magnet available
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Anesthesia for Pt with
Pacemaker
If using Succinylcholine, consider defasciculating dose of MR
Fasciculations may inhibit firing due to the skeletal muscle
contractions picked up by generator as intrinsic R waves
Place ground pad far from generator but close to cautery tip
Cover pad well with conductive gel
Minimizes detection of cautery current by pulse generator
If patient has a transvenous pacemaker, increased risk of V. fib
from microshock levels of electrical current
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Anesthesia for Pt with
Pacemaker
Cautery may interfere with pacer:
May inhibit triggering (pacer may sense electrical
activity and not fire)
May inadvertently reprogram
May induce arrhythmias secondary to current
May cause fixed-rate pacing
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Automatic
Implantable
Cardiac
Defibrillators
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AICD
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Parts of AICD
 Pulse generator with batteries
and capacitors
 Electrode or lead system
Surgically placed in or on pericardium/myocardium
 Monitors HR and rhythm
Delivers shock if VT or Vfib
117
Placement of AICD
Pulse Generator
118
AICD Indications
 Risk for sudden cardiac death
caused by tachyarrhythmias (VT, Vfib)
 Reduces death from 40% to 2% per year
119
Defibrillator Codes
First letter: Shock Chamber
A: atrium
V: ventricle
D: dual
O: none
120
Defibrillator Codes
Second letter: Antitachycardia Chamber
A: atrium
V: ventricle
D: dual
O: none
Third letter: Tachycardia Detection
E: EKG
H: Hemodynamics
121
Defibrillator Codes
Fourth letter: Antibradycardia Pacing Chamber
A: atrium
V: ventricle
D: dual
O: none
122
Settings
Gives a shock at 0.1-30 joules
Usually 25 joules
Takes 5-20 seconds to sense VT/VF
Takes 5-15 seconds more to charge
2.5-10 second delay before next shock is
administered
Total of 5 shocks, then pauses
If patient is touched, may feel a buzz or tingle
If CPR is needed, wear rubber gloves for insulation
123
Tiered Therapy
Ability of an implanted cardioverter
defibrillator to deliver different types of
therapies in an attempt to terminate
ventricular tachyarrhythmias
EX of therapies:
Anticardiac pacing
Cardioversion
Defibrillation
Antibradycardia pacing
124
Anesthesia
MAC vs General
Usually general due to induction of VT/VF so AICD
can be checked for performance
Lead is placed in heart
Generator is placed in hip area or in upper
chest
125
VADs
Ventricular assist devices
Implantable pumps used for circulatory support
in pts with CHF
Blood fills device through a cannulation site in
V or A
Diaphragm pumps blood into aorta or PA
Set at predetermined rate (fixed) or automatic
(rate changes in response to venous return)
126
Electromagnetic
Interference on Pacers
and AICDs
Electrocautery
May inhibit or trigger output
May revert it to asynchronous mode
May reprogram inappropriately
May induce Afib or Vfib
May burn at lead-tissue interface
127
Electromagnetic Interference on
Pacers and AICDs
Defibrillation
May cause permanent damage to pulse generator
May burn at lead-tissue interface
Radiation Therapy
May damage metal oxide silicon circuitry
May reprogram inappropriately
128
Electromagnetic Interference
on Pacers and AICDs
PET/CT (Contraindicated)
May damage metal oxide silicon circuitry
May reprogram inappropriately
MRI (Contraindicated)
May physically move pulse generator
May reprogram inappropriately
May give inappropriate shock to pt with AICD
PNSs
May cause inappropriate shock or inhibition
Test at highest output setting
129
Deactivating a Pacemaker
Deactivate to prevent inappropriate firing or
inhibition
Can be deactivated by a special programmer/wand
or by a magnet placed over generator for 30
seconds
Put in asynchronous mode or place external pacer
on patient
130
If Pt has a Pacemaker/AICD
Not all models from a certain company behave
the same way with magnet placement !
For all generators, call manufacturer
Most reliable method for determining magnet
response ! !
131
Coding Patient
If patient codes, do not wait for AICD
to work
Start CPR & defibrillate immediately
Person giving CPR may feel slight buzz
A 30-joule shock is < 2 j on pt’s skin
External defibrillation will not harm AICD
Change paddle placement if unsuccessful
attempt
Try A-P paddle placement if A-Lat unsuccessful
132
Pts with
Pacemakers/AICDs/VADs
Obtain information from patient regarding
device
Ask how often patient is shocked/day
High or low K+ may render endothelial cells
more or less refractory to pacing
A properly capturing pacemaker should also be
confirmed by watching the EKG and
palpating the patient’s pulse
133
Anesthetic Considerations
Avoid Succinylcholine
Keep PNS as far from generator as possible
Have backup plan for device failure
Have method other than EKG for assessing
circulation
Have magnet available in OR
134
Electrocautery Use
Place grounding pad as far from generator as
possible
Place grounding pad as near to surgical field as
possible
Use bipolar electrocautery if possible
Have surgeon use short bursts of
electrocautery
(<1 sec, 5-10 seconds apart)
Maintain lowest possible current
135
Electrocautery Use
If cautery causes asystole, place magnet over
control unit & change from inhibited to
fixed mode
Change back afterwards
Be alert for R on T phenomenon
136
Postoperative Considerations
Avoid shivering
Have device checked and reprogrammed if
questions arise about its function
137
Examples of Rhythms
Sensing
Patient’s own beat is sensed by pacemaker so does not fire
138
Examples of Rhythms
Undersensing
Pacemaker doesn’t sense patient’s own beat and fires
(second last beat)
139
Examples of Rhythms
Oversensing
Pacemaker senses heart beat even though it isn’t beating. Note the
long pauses.
140
Examples of Rhythms
Capture
Pacemaker output (spike) is followed by ventricular polarization
(wide QRS).
141
Examples of Rhythms
Noncapture
Pacer stimulus fails to cause myocardial depolarization
Pacer spike is present but no ECG waveform
Oversensing-Fails to fire
UndersensingFails to sense
ECG
Fires but fails to capture
Pacer spikes after theQRS
142
Examples of Rhythms
100 % Atrial Paced Rhythm with 100% Capture
143
Examples of Rhythms
100% Ventricular Paced Rhythm with 100% Capture
144
Examples of Rhythms
100% Atrial and 100% Ventricular Paced Rhythm with
100% Capture
145
Examples of Rhythms
50% Ventricular Paced Rhythm with 100% Capture
146
Examples of Rhythms
25% Ventricular Paced Rhythm with 100% Capture (Note
the sensing that occurs. Pacer senses intrinsic HR and
doesn’t fire).
147
Examples of Rhythms
AICD Shock of VT
Converted to NSR
148
Examples of Rhythms
149
Examples of Rhythms
150
Examples of Rhythms
DDD Pacemaker
151
References
Moser SA, Crawford D, Thomas A. AICDs.
CC Nurse. 1993;62-73.
Nagelhaut JJ, Zaglaniczny KL. Nurse
Anesthesia. Philadelphia: Saunders.1997.
Ouellette, S. (2000). Anesthetic considerations in patients
with cardiac assist devices. CNRA, 23(2), 9-20.
Roth, J. (1994). Programmable and dual chamber
pacemakers: An update. Progress in anes thesiology,
8, chapter 17. WB Saunders.
152
Pacemaker
a medical device that uses electrical impulses, delivered
by electrodes contacting the heart muscles, to regulate the beating of
the heart , and maintain an adequate heart rate, either because of the
heart's native pacemaker is not fast enough, or there is a block in the heart's
electrical conduction system