Transcript PROCEDURES PERFORMED OUTSIDE THE OPERATING ROOM

Dr Masood Entezariasl
 The
number of diagnostic and therapeutic
medical procedures that require specialized
environments such that they must be
performed away from traditional hospital
and outpatient operating room suites is
increasing (Table)
 Office based anesthesia has become a
primary mode of practice for many
anesthesiologists
Radiology and Nuclear Medicine
Diagnostic radiology and nuclear medicine
Computed tomography
Fluoroscopy
Therapeutic radiology
Interventional body angiography (can involve embolization or stent placement)
lnterventional neuroangiography (can involve embolization or stent placement)
Magnetic resonance imaging
Ultrasound imaging
Radiation Therapy
Standard x-ray therapy with collimated beams
Gamma Knife x-ray surgery for brain tumors and A-V malformations
Cyber Knife x-ray surgery for central nervous system, body tumors, and AVmalformations
Electron beam radiation therapy (usually intraoperative)
Cardiology
Cardiac catheterization with or without electrophysiologic studies
Cardioversion
Gastroenterology
Endoscopy
Colonoscopy
Endoscopic retrograde cholangiopancreatography
Pulmonary Medicine
Tracheal and bronchial stent placement
Bronchoscopy
Pulmonary lavage
Psychiatry
Electroconvulsive therapy
Urology
Extracorporeal shock wave lithotripsy
General Dentistry and Oral and Maxillofacial Surgery
Dental surgery
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Remote locations are much different from self-contained
operating rooms
There should also be clear policies for dealing with remote
equipment problems and unexpected escalations of medical
problems
It is important for an anesthesiologist working in an unfamiliar
remote location to keep track of the identity and role of
personnel who participate in the surgical procedure or patient
care
During times when the anesthesiologist may need experienced
medical assistance (tracheal intubation, placement of a central
venous catheter), it can be important to know which of the
available staff members are qualified to render assistance
Readily available preoperative documents for all patients in
remote locations must include the attending surgeon's history and
physical examination
Arrangements for patient arrival and check-in should be similar
to those for outpatients and inpatients undergoing procedures in
a traditional operating room setting
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Remote locations must provide for the same basic anesthesia
care that is possible in any operating room
There must be adequate monitoring capabilities, the means
to deliver supplemental oxygen by facemask with positive
pressure, the availability of suction, equipment for providing
controlled mechanical ventilation, an adequate supply of
anesthetic drugs and ancillary equipment, and supplemental
lighting for procedures that involve darkness
Although new, portable anesthesia machines (Fig) can
sometimes be placed very close to the patient to facilitate
gas connections, it is often not possible to have an
anesthesia machine as close to the patient as in the
operating room (Fig)
The use of sedation, as for placement of a nerve block,
should take place in an area (block room) where adequate
equipment, drugs, and support personnel are available for
immediate intervention
If anesthetic gases are to be used, scavenging must be
sufficient to ensure that trace amounts are below the upper
limits set by the Occupational Safety and Health
Administration (OSHA)
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Remote locations frequently involve additional hazards,
such as exposure to radiation, high sound levels, and heavy
mechanical equipment
Advance preparation should be made to have all needed
equipment available, such as lead aprons, portable
leadglass shields, and earplugs
At the end of the procedure one must often travel
distances that are typically greater than the usual distance
to the postanesthesia care unit or other patient units
So that patients can be safely and expeditiously taken to a
recovery area, remote locations should always have
available sufficient supplies of supplemental oxygen,
appropriate transport monitoring equipment, and elevator
and passageway keys
The anesthesiologist should always know the location of
the nearest defibrillator, fire extinguisher, gas shutoff
valves, and exits
 Interventional
neuroradiology (endovascular
neurosurgery) mixes traditional neurosurgery
with neuroradiology while also including
certain aspects of head and neck surgery
 Body angiography mixes general surgery with
general radiology
 In angiographic procedures the relevant
blood vessel trees are imaged, after which a
decision is made to continue by providing
one or more therapeutic interventions via
drugs or devices (or both)
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Anesthesia-related concerns include:
(1)
maintenance
of
patient
immobility
and
physiologic stability
(2) perioperative management of anticoagulation
(3)
readiness
for
sudden
unexpected
complications during
the procedure
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provision
of
smooth
and
rapid
emergence
from anesthesia and sedation
at appropriate
times (may be required during
the procedure)
(5)
appropriate
monitoring
and
management
during transport after
completion of the
procedure,
particularly for critically ill
patients, who
may require continuous
evaluation of
breathing and systemic
blood
pressure
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Maintenance of blood pressure is particularly important in
patients with cerebrovascular disease
Blood pressure targets should always be discussed preoperatively
with the surgical team
Maintaining a higher than normal blood pressure is important in
cases in which the patient has occlusive cerebrovascular disease,
such cases include patients undergoing emergency thrombolysis
and patients with aneurysmal subarachnoid hemorrhage in whom
vasospasm has developed
Conversely, prevention of blood pressure increases may be
critical in certain groups , examples include patients with
recently ruptured intracranial aneurysms or recently obliterated
intracranial A-V malformation and patients who have undergone
cerebrovascular angioplasty and stent placement in extracranial
conductance vessels such as the carotid artery
These patients are also susceptible to post-treatment cerebral
hyperperfusion injury and require careful control of systemic
blood pressure after the procedure
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Anticoagulation is often needed during intracranial catheter navigation
to prevent thromboembolic complications
Heparin (70 U/kg) is commonly used to prolong the baseline activated
clotting time (ACT) by a factor of 2 to 3
Hourly monitoring of the ACT is performed to assess the need for
additional heparin, which can be given continuously or as intermittent
boluses
Hemorrhagic complications during the procedure may necessitate
emergency reversal of anticoagulation
If heparin has been administered, a full reversal dose of protamine (1
mg for each 100 units of heparin activity) should always be available for
immediate injection
At the completion of uneventful procedures, heparin can be reversed
with protamine, if deemed appropriate
Antiplatelet agents (aspirin, ticlopidine, and antagonists to glycoprotein
IIb/IIIa receptors) are often used together with heparin, particularly
when placing intraarterial stents
Although antiplatelet drugs decrease the incidence of serious
thromboembolic complications, emergency reversal of their
anticoagulant effects is difficult
The only practical approach to antagonism of these drugs is empirical
provision of exogenous platelets
 During
transport from the imaging suite,
airway management equipment, including a
face mask and an Ambu bag or a JacksonRees circuit, should be immediately available
for providing positive-pressure ventilation
 It is not unusual to maintain an intravenous
sedation regimen (propofol infusion) during
transport or to have given additional
medications just before transport
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Patient immobility during radiation therapy is the
primary goal of sedation or general anesthesia so that
the delivered radiation can be precisely targeted
Radiation therapy may involve daily treatments for
several weeks
Treatments frequently take very little time, and
patients want to quickly resume normal daily
activities
In such instances, sedation or general anesthesia
should be achieved with fast-onset, short-acting
drugs appropriate for brief duration and rapid
emergence while keeping in mind that sedation or
anesthesia will be repeated daily
Anesthesia may also be required for lengthy or
complex cases
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Radiation therapy for cancer delivers large radiation doses to target
tissues
In some patients, radiation is used to kill vulnerable cancer cells
while only minimally injuring noncancer cells
In others, radiation is used to kill all cells in the target region
(reason that the radiation device may be referred to as a "knife")
Such radiation therapy is known as stereotactic because threedimensional MRI and CT images are used by the radiation
instrument to target specific tissue volumes.
GammaKnife simultaneously directs multiple carefully aligned,
pencilthin gamma ray beams into the targeted area
The CyberKnife is also characterized by delivery of a large number
of ovelapping pencil-thin gamma-ray beams to provide lethal
radiation
In contrast to the GammaKnife, which exposes the patient to the
gamma rays as a simultaneous single dose, the CyberKnife exposes
the patient to a sequence of several hundred gamma-ray beams,
each being delivered from a computer-controlled robot arm that
moves around the patient and shoots the beams at cancer regions
from different directions
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Anesthesia for GammaKnife procedures can involve general anesthesia or
sedation for placement of a head frame, subsequent MRI or CT (or both),
transport to the recovery room where anesthesia or sedation is
maintained as one waits for generation of the computer data needed by
the GammaKnife, and finally transport of the anesthetized or sedated
patient to the GammaKnife room for the treatment
CyberKnife procedures require prior surgical implantation of radiopaque
markers
The anesthesiologist must keep the anesthesia machine, the drug cart,
and all tubes and hoses away from all locations that will be occupied by
the robot arm
Robot motions can be monitored closely by a remote video connection to
verify that one's setup is appropriate.
Scattered gamma radiation during therapy reaches high enough levels in
the treatment room to require that all health care personnel be outside
Treatments occur in a heavily shielded room with health care personnel
typically waiting on the other side of a large lead or iron door that takes
30 to 60 seconds to open
Physiologic monitoring is accomplished via two or more remote video
connections
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Other external beam radiation therapy modalities for cancer include
electron beam radiation and heavy particle ion beam radiation
The "heavy particles" are nuclei from atoms larger than helium
This treatment mode has limited availability, but it has significant
advantages because the energy deposition of a heavy ion beam is very
concentrated and it can be targeted with millimeter precision
Intraoperative use of particle beams has become popular in cancer
surgery
During intraoperative radiation therapy (IORT), a giant linear
accelerator is placed in the operating room, and the depth and width
of the electron beam are adjusted according to the patient's needs
Adjacent organs and tissues are shielded with lead
All personnel must leave the room during the radiation treatment, but
thick shielding walls are not Necessary
A single IORT session will typically provide as much therapy as 10 to 20
daily gamma-ray treatments
In some instances the patient cannot receive IORT in the operating
room when an intraoperative gamma-ray treatment is needed. In such
cases, the anesthesiologist must transport the anesthetized patient to
the alternative treatment area
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Electroconvulsive therapy (ECT) is used primarily after
failure of pharmacotherapy for affective disorders,
most notably severe depression, but also bipolar
syndrome and schizophrenia
Because the ECT effect is evident within only a few
treatments, it has been proposed for the treatment of
psychiatric disorders of high acuity, such as suicidal
patients or those unable to take food
There is little doubt about the short-term effectiveness
of ECT for depression, but controversies remain
regarding its place in long-term management, as well
as the definition of failed pharmacotherapy.
ECT's therapeutic effects are thought to result from the
release of neurotransmitters during the electrically
induced grand mal seizure or, perhaps, from the
reestablishment of neurotransmitter levels that occurs
after seizure activity
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It is important that an electrically induced seizure be
of sufficient duration (>20 seconds) for optimal
therapeutic effect
In this regard, the anesthesiologist must consider the
impact of selected anesthetic drugs on the duration
of seizure activity
Electrically induced seizures are characterized by an
initial tonic phase (lasts 10 to 15 seconds), followed
by a second myoclonic phase (lasts 30 to 60 seconds)
Seizure duration is monitored by motor activity and
usually a single-channel electroencephalogram
Needs for adjustments in seizure length should be
discussed with the anesthesiologist before ECT
The two goals of anesthetic management are to:
(1)
provide
partial
neuromuscular
blockade
because unmitigated motor
activity can
result in long bone
fractures and skeletal
muscle injury
(2) render the patient briefly unconscious for
application of the electrical stimulus
 The seizure is associated with a profound amnestic
response and is not painful if motor activity is
blocked
 In the past, anesthetics most often used for ECT
were the short-acting barbiturates methohexital
(0.5 to 1.0 mg/kg IV) and thiopental(1.0-2.0 mg/kg
IV)
 More recently, propofol (1mg/kg IV) and etomidate
(0.3 mg/kg IV) have become popular
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studies have found that systemic
hemodynamics during ECT is more stable
under propofol anesthesia than under
barbiturate anesthesia, it appears that
propofol tends to shorten seizure duration
 In this regard, reducing the propofol dose
while adding a short-acting opioid (alfentanil
or remifentanil) increases seizure duration by
about 50% without causing significant
differences in hemodynamics or recovery
time
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Etomidate may be preferred over propofol because of
its association with longer electrically induced seizures
and minimal cardiovascular and respiratory depression
However, a 50% to 80% incidence of myoclonus has
been reported with etomidate
Although myoclonus is quickly terminated by the
succinylcholine dose that immediately follows the
etomidate injection, it and the skeletal muscle
response to succinylcholine (fasciculations) can
produce myalgias
Large doses of etomidate are known to cause
adrenocortical suppression, and after a single dose
some suppression has been found at 6 hours, with
responses being normal at 24 hours
The adrenocortical effects of daily doses of etomidate
as administered for ECT are not known
In many instances, patients selected for ECT will
have had their psychotropic medications tapered
for 1 or 2 weeks before a series of 10 to 20 ECT
treatments delivered over a period of several
weeks
 However, it is also not unusual for ECT patients
to be taking one or more psychotropic drugs
when they arrive for treatment
 Such
drugs include monoamine oxidase
inhibitors, serotonin uptake inhibitors, tricyclic
antidepressants, lithium, and benzodiazepines
 Hypothyroidism is known to occur in patients
who have been taking lithium for a long time (15
years or more)
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ECT treatments are usually performed as morning
cases in a procedure room that is fully equipped for
general anesthesia, typically in or close to the
postanesthesia care unit. Patients should be NPO
during the preceding night
Preoperative evaluation of ECT patients should follow
the guidelines for other surgical patients, including a
current medical history and physical examination
On the morning of the procedure the anesthesiologist
should document any interval change in the patient's
medical condition
Such changes can occur during a course of several
ECT treatments, with anesthesia having been
provided by multiple personnel
Generally, ECT should not be perfonned on patients
with intracranial mass lesions
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If a pregnant patient undergoes ECT, close monitoring of
the fetus is recommended
Although the overall risk of aspiration in ECT cases is
very small (less than 1 per 2000 cases), esophageal
reflux and hiatal hernia are common findings in ECT
patients
Some centers use drugs before the procedure to
increase gastric fluid pH or decrease gastric fluid
volume, or both
However, there are no data to support this practice
External cardiac pacemaker function should not be
affected by ECT because the current path is far from
the heart
Patients with a history of coronary artery disease,
congestive heart failure, and valvular heart disease may
benefit from invasive monitoring to assess myocardial
function and permit aggressive hemodynamic control
Anesthesia for ECT begins with attachment of all
monitors, administration of 100% oxygen by
facemask, and acquisition of vital signs
 Supplemental oxygen is continued during and
after ECT
 A second blood pressure cuff is placed on the
lower part of the leg or forearm
 This cuff is inflated before administration of the
neuromuscular blocking drug to allow monitoring
of motor activity during the seizure
 Standard neuromuscular blockade monitoring may
be carried out distal to the cuff, if desired
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After preoxygenation, anesthesia is induced by the
administration of propofol (1 to 1.5 mg/kg IV) or etomidate
(0.15 to 0.30 mg/kg IV), alone or in combination with esmolol
and/or a rapidly acting opioid such as remifentanil or
alfentanil
After the patient loses consciousness, the blood pressure cuff
on the leg or arm is inflated above arterial pressure so that it
functions as a tourniquet to prevent distal perfusion
During this time, ECT electrodes are applied by the
psychiatrist to one or both sides of the head, and an oral
airway, if placed previously, is removed and replaced with a
bite block to protect the tongue
Because hypercapnia can increase a patient's seizure
threshold, the anesthesiologist often provides ventilatory
support via the mask just before the therapist energizes the
electrodes
Indeed, ECT therapists often prefer that the anesthesiologist
hyperventilate the patient's lungs to generate hypocapnia and
a lower seizure threshold
 Succinylcholine
(0.5 to 1 mg/kg IV) is
injected just before application of the
electrical current
 Full relaxation is not required to prevent
seizure-induced skeletal muscle and bone
injury
 When succinylcholine is contraindicated, a
short-acting non depolarizing neuromuscular
blocking drug such as mivacurium is selected
 Succinylcholine
is known to increase
intragastric pressure, and suction must be
available to treat regurgitation
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Endotracheal intubation is rarely required, but it is
important to have available all necessary equipment
should unexpected airway problems arise
Monitoring with pulse oximetry is used to guide the
need for continued administration of supplemental
oxygen
The use of a second peripheral nerve stimulator,
placed anywhere proximal to the leg tourniquet, will
confirm the degree of neuromuscular blockade
produced by the neuromuscular blocking drug and
will
also
identity
unexpected
prolonged
neuromuscular blockade, which will occur in patients
with
previously
unrecognized
cholinesterase
deficiency
The electrocardiogram (ECG) is a necessary monitor
because cardiac dysrhythmias can occur during ECT
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Visual monitoring of the seizure is possible by observing
the tonic contractions and myoclonus distal to the
previously inflated tourniquet (blood pressure cuff)
that has been placed on an extremity (serves to isolate
this portion of the body from the circulation and the
effects of the neuromuscular blocking drug)
The electrodes are energized by the psychiatrist once
it is clear from fasciculations or the neural blockade
monitor that succinylcholine has acted throughout the
body (except below the inflated blood pressure cuff)
Just before the ECT shock one can give the patient a
few breaths of supplemental oxygen via the anesthesia
mask, which serves to reduce end-tidal CO2,
denitrogenate the functional residual capacity (FRC),
and help prevent airway collapse during apnea
During the ECT shock it is safe for the anesthesiologist
to be using gloved hands to gently displace the
mandible forward to ensure that the tonic phase of the
seizure does not displace the bite block
The two phases of the electrically induced
seizure (tonic and clonic) have characteristic and
highly predictable effects on the vital signs
 The initial tonic phase is characterized by
profound stimulation of the parasympathetic
nervous system that results in a consistent brief
period of bradycardia
 Blood pressure may decrease as well
 This phase quickly converts to a state of
sympathetic nervous system stimulation as the
seizure enters the clonic phase
 Systemic hypertension and tachycardia are often
observed but usually abate at or soon after the
conclusion of the seizure
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During this time cardiac dysrhythmias may be visible
on the ECG, as well as changes indicative of
myocardial ischemia
Because the maximum blood pressure and heart rate
occur and end so quickly, medications to reduce these
self-limited changes must be used with great caution
If used, they are most effective when given before
the seizure is induced
In appropriate patients, esmolol (0.15 to 1.50 mg/kg
IV) or labetalol (0.13 mg/kg IV) may be administered
30 to 60 seconds before the seizure is induced
Similarly, remifentanil or alfentanil may also be
administered just before seizure induction
However, routine blunting of sympathetic nervous
system responses by β-adrenergic antagonists is not
recommended because severe bradycardia has been
observed
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patients undergo a series of ECT
sessions, after the first treatment one can
evaluate previous cardiovascular responses
to the electrical shocks and revise whatever
decision one made before about esmolol and
other drugs
 One can similarly assess the dose used to
produce neuromuscular blockade
 On rare occasion a seizure will not abate
 Seizures that last longer than 90 seconds
should generally be terminated with a repeat
dose of propofol or equivalent drug
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Pediatric cardiac catheterization is usually performed
for the diagnosis and evaluation of congenital heart
disease.
However, septal defects can sometimes be repaired
Intravenous sedation or general anesthesia must be
adequate to prevent stress-induced changes in heart
rate and systemic blood pressure without interfering
with existing intracardiac shunts as reflected by
arterial blood gas measurements.
Excess myocardial depression or changes in preload as
a result of fluid imbalance must be avoided
Normocapnia is a goal of ventilation during anesthesia
for cardiac catheterization
A high hematocrit may be associated with an increased
risk for thrombosis, whereas lowering the hematocrit
may jeopardize tissue oxygen delivery
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Cardiac dysrhythmias and heart block are important
causes of morbidity, thus emphasizing the need for
prompt access to a defibrillator and resuscitation drugs
Premedication and sedation (often combinations of
midazolam and a short-acting opioid) may be sufficient
to allay the anxiety that could exacerbate coexisting
cardiopulmonary problems
Atropine
premedication
is
sometimes
useful,
particularly if cyanotic congenital heart disease is
present
The onset of action of injected or inhaled drugs (or
both) may be influenced by the presence of a left-to
right or right-to-left intracardiac shunt, as well as by
coexisting congestive heart failure and associated low
cardiac output
Patient monitoring during cardiac catheterization may
include arterial blood gas data
Access to the patient can be limited by fluoroscopy and
the presence of surgical equipment on all sides of the
patient during the procedure
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Adult cases can be extremely challenging, particularly in
patients with advanced myocardial disease, who routinely
have an ejection fraction (EF) below 20% and who come
for installation of programmable pacemaker that is also an
implanted cardioverter/defibrillator (ICD)
It is not uncommon for such pacemakers to provide right
and left dual-chamber pacing.
Timing
parameters
are
adjusted
during
the
electrophysiology session, and the session is concluded
with repeated defibrillator tests during which the
cardiologist induces fibrillation and the device
automatically delivers a rescue shock
Conscious sedation with spontaneous respiration is best in
such cases. Before starting the procedure the
anesthesiologist should be sure to check the filter setting
on the ECG monitoring setup
Many ECG monitors routinely filter out sharp pulses, thus
making pacemaker spikes invisible unless "HIDE" is
changed to "SHOW" under the setting for pacemakers
Using a minidrip intravenous set can be very helpful in
avoiding inadvertent administration of intravenous fluids
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A primary element in the anesthesia plan is avoidance of
positive-pressure ventilation whenever possible because it
will increase pulmonary vascular resistance, decrease left
ventricular filling, and decrease arterial pressure
Systemic blood pressure in cardiomyopathy patients with a
low EF should be monitored continuously via an arterial
catheter; if necessary, the pressure can often be raised with
low-dose boluses of phenylephrine (e.g., 25 to 50 чg per
bolus), but response is slower than in patients with normal
cardiac output
In rare cases phenylephrine can cause an increase in
systemic vascular resistance that is not tolerated by a
cardiomyopathic heart
If such is the case when blood pressure is dangerously low,
gentle inotrope administration is needed, as sometimes
occurs when inducing anesthesia for cardiac transplantation
Although patients with ICDs have many indwelling catheters
and lie on a narrow table, brief neuromuscular blockade is
rarely needed to avoid adverse sudden muscle movements at
the time of ICD testing
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At that time a small dose of propofol after voluntary
preoxygenation and hyperventilation is usually sufficient for
patients undergoing conscious sedation with spontaneous
ventilation
Once ICD testing is complete, gentle hand ventilation via a
mask can be used if needed to maintain oxygenation until
spontaneous respirations return
Cases will occur in which general anesthesia, endotracheal
intubation, and mechanical ventilation are all unavoidable
Low-dose etomidate is a useful induction agent in such
instances
Supplementation with midazolam is helpful in minimizing the
likelihood of awareness
However, spontaneous ventilation will be reduced by
midazolam, and it is important later on to not have serious
interference from this adverse secondary effect
During general anesthesia, maintenance typically consists of
50% or more nitrous oxide and a small amount of vapor
Blood pressure is often improved when dual-chamber cardiac
pacing is initiated by the cardiologist
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Elective cardioversion requires a brief period of sedation and
amnesia for the discomfort produced by the electric Shock
After monitors are attached and emergency drugs and
equipment have been checked, including the availability of
suction, the patient is preoxygenated and the desired level of
sedation is typically produced by the intravenous
administration of a short-acting drug such as propofol
After loss of consciousness, the electrical charge is delivered
to the patient, and gentle assisted ventilation of the patient's
lungs with 100% oxygen is provided as needed, with a bag and
mask used until consciousness has returned
Decreases in systemic blood pressure, especially after the
administration of propofol, can be minimized by the use of a
low dose at a reduced rate of injection
Etomidate is an unlikely selection despite its reduced cardiac
depression because the myoclonus that it often induces can
make airway management and ECG analysis difficult
Because of slower onset, a less profound degree of central
nervous system depression, and duration of action,
benzodiazepines are not as useful for cardioversion
Extracorporeal shock wave lithotripsy (ESWL)
uses focused shock waves (high-intensity
pressure waves of short duration) to pulverize
renal and ureteral calculi into very small
fragments, which are then washed out by normal
urine flow
 Modern lithotripters deliver several precisely
focused, simultaneous shock waves that have
been generated in water-filled cushions at the
surface of a special table on which the patient
lies
 Pain at the skin is usually tolerable or amenable
to short-acting drugs
 Patient immobility during lithotripsy is very
important
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 Ureteroscopic
lithotripsy (also referred to as
"endoscopic lithotripsy") is needed for the
disintegration of complex upper urinary tract
calculi
 A powerful yttrium-aluminum garnet (YAG)
laser is aimed directly at the stones
 ESWL and
ureteroscopic lithotripsy are
routinely performed on an outpatient basis
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ESWL was initially possible only by immersing the
patient from the neck down in a water bath
Modern ESWL has eliminated numerous concerns unique
to patient immersion, which produces effects similar to
those of a G-suit. For example, immersion causes
peripheral venous compression, thereby increasing
central intravascular volume and central venous
pressure-typically by 8 to 11 mm Hg
Immersion lithotripsy also increases the work of
breathing, and breathing in awake patients often
becomes shallow and rapid
Extrinsic pressure on the abdomen and chest results in a
decrease in vital capacity and FRC
Patients with preexisting pulmonary disease may
experience impaired ventilation and oxygenation during
water immersion
Despite the increased central venous pressure,
some patients will exhibit hypotension secondary
to vasodilatation as a result of the effects of warm
water
 Hypotension may also occur during removal from
the water bath
 During
immersion
or
emersion,
cardiac
dysrhythmias can occur, presumably reflecting
abrupt changes in right atrial pressure and rapid
changes in central venous return
 Because placement in a water bath puts patients
with marginal cardiovascular reserve at greater
risk for congestive heart failure or myocardial
ischemia, such patients should undergo lithotripsy
only in modern units that do not involve immersion
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 To
minimize the risk of initiating cardiac
dysrhythmias (especially ventricular tachycardia),
shock waves are triggered from the ECG to occur
20 msec after the R wave, which corresponds to
the absolute refractory period of the heart
 The concern that shock waves could interfere with
functioning of external cardiac pacemakers has
not been validated, and the presence of such a
device is not considered a contraindication to
ESWL, assuming that the external cardiac
pacemaker is not positioned in the path of the
shock waves
Hematuria occurs in nearly all patients,
presumably from renal parenchymal damage or
dislodgement of calculi
 In very rare instances, calcifications in blood
vessels near the kidney can unintentionally be
disintegrated by shock waves aimed at renal
stones
 Thus, vigilance must always be maintained for
bleeding, hematoma formation, or emboli
 Other very rare side effects of shock wave
damage include pulmonary contusions and
pancreatitis
 Flank pain may persist for several days after
ESWL, and petechiae and soft tissue swelling are
common at the shock wave entry site
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Shock waves cause cutaneous pain as they traverse the waterskin interface
"With modern lithotripters the pain is minimal, and
intravenous sedation and analgesia are usually sufficient
Supplemental oxygen should be administered during the
procedure
It is often possible to avoid endotracheal intubation and use a
laryngeal mask, an ordinary facemask, or simply nasal prongs
The pain is greater with immersion lithotripsy, and general or
regional anesthesia is needed
If an epidural technique is used, air should never be injected
because it can create a significant density difference just
outside the dura
It is not uncommon for midline back pain to develop
postoperatively in patients who have had air injected into
their epidural space during immersion lithotripsy
Adequate intravenous fluid administration is essential during
lithotripsy to facilitate the passage of disintegrated stones
and maintenance of systemic blood pressure