Renal ds

1. Anesthesia for Patients with
Renal Disease

2. • renal pathophysiololgy
– The effect of anesthetic agent and Muscle relaxant
– technique on renal function
– Positioning on renal surgery
• Anesthesia for Genitourinary Surgery (7hrs)
– Kidney transplantation
– Lithotripsy
– Percutaneous ultrasonic lithotripsy
– Extra corporeal shock wave lithotripsy
– Prostatectomy
– Trans-vesical resection
– Trans-urethral resection

3. Anesthesia and surgery has an effect directly or
indirectly on the renal surgery
Direct effects
All inhalational and many iv induction agents
cause
Myocardial depression
Hypotension
Increased renal vascular resistance
Effect – decreased RBF
_ decreased GFR, then decreased UOP

4. • In direct effects ;
Of a great consern
 direct toxicity of fluorinated agent
Fluoride ion :- inhibit metabolic process
Cause proximal tubular swelling & necrosis
Affect urine concentrated ability

5. Altered Renal Function & the Effects of
Anesthetic Agent
Intravenous Agents
Propofol & Etomidate
• The pharmacokinetics of both propofol and etomidate
are not significantly affected by impaired renal function.
Decreased protein binding of etomidate in patients with
hypoalbuminemia may enhance its pharmacological
effects.

6. Barbiturates
• Patients with renal disease often exhibit increased
sensitivity to barbiturates during induction, even
though pharmacokinetic profiles appear to be
unchanged. The mechanism appears to be an
increase in free circulating barbiturate as a result of
decreased protein binding. Acidosis may also favor a
more rapid entry of these agents into the brain by
increasing the nonionized fraction of the drug

7. Ketamine
• Ketamine pharmacokinetics are minimally altered
by renal disease. Some active hepatic metabolites
are dependent on renal excretion and can
potentially accumulate in renal failure.
Ketamine's secondary hypertensive effect may be
undesirable in hypertensive renal patients.

8. Benzodiazepines
• Benzodiazepines undergo hepatic metabolism and
conjugation prior to elimination in urine. Because
most are highly protein bound, increased sensitivity
may be seen in patients with hypoalbuminemia.
Diazepam should be used cautiously in the presence
of renal impairment because of a potential for the
accumulation of active metabolites.

9. Opioids
• Most opioids currently in use in anesthetic management
are inactivated by the liver; some of these metabolites
are then excreted in urine. The accumulation of
morphine (morphine-6-glucuronide) and meperidine
metabolites has been reported to prolong respiratory
depression in some patients with renal failure. Increased
levels of normeperidine, a meperidine metabolite, have
been associated with seizures. The pharmacokinetics of
the most commonly used opioid agonist–antagonists
(butorphanol, nalbuphine, and buprenorphine) are
unaffected by renal failure.

10. Anticholinergic Agents
• In doses used for premedication, atropine and
glycopyrrolate can generally be used safely in
patients with renal impairment. Because up to 50%
of these drugs and their active metabolites are
normally excreted in urine, however, the potential
for accumulation exists following repeated doses.
Scopolamine is less dependent on renal excretion,
but its central nervous system effects can be
enhanced by azotemia.

11.  Phenothiazines, H2 Blockers, & Related Agents
• Most phenothiazines, such as promethazine, are
metabolized to inactive compounds by the liver.
Although pharmacokinetic profiles are not
appreciably altered by renal impairment,
potentiation of their central depressant effects by
azotemia can also occur
• All H2-receptor blockers are very dependent on renal
excretion. Metoclopramide is partly excreted
unchanged in urine and will also accumulate in renal
failure

12. Inhalation Agents
Volatile Agents
• Volatile anesthetic agents are nearly
ideal for patients with renal dysfunction
because of their lack of dependence on
the kidneys for elimination, their ability
to control blood pressure, and generally
minimal direct effects on renal blood
flow .

13. • Although patients with mild to moderate renal
impairment do not exhibit altered uptake or
distribution, accelerated induction and
emergence may be seen in severely anemic
patients (hemoglobin < 5 g/dL) with chronic
renal failure; this observation may be
explained by a decrease in the blood:gas
partition coefficient or a decrease in minimum
alveolar concentration.

14. • Enflurane and sevoflurane (with < 2 L/min gas
flows) are considered undesirable for patients
with renal disease undergoing long
procedures because of the potential for
fluoride accumulation .
• Methoxyflourane ???????

15. Nitrous Oxide
• Many clinicians omit or limit the use of nitrous oxide
to 50% in patients with renal failure in an attempt to
increase arterial oxygen content in the presence of
anemia.
• This rationale may be justified only in severely
anemic patients (hemoglobin < 7 g/dL), in whom
even a small increase in the dissolved oxygen content
may represent a significant percentage of the arterial
to venous oxygen difference.

16. Muscle Relaxants
Succinylcholine
• Succinylcholine can be safely used in the presence of
renal failure, provided the serum potassium
concentration is known to be less than 5 mEq/L at the
time of induction. When the serum potassium is higher
or is in doubt, a nondepolarizing muscle relaxant should
be used instead.
• Although decreased pseudocholinesterase levels have
been reported in a few uremic patients following dialysis,
significant prolongation of neuromuscular blockade is
rarely seen.

17.  Cisatracurium, Atracurium, & Mivacurium
• Mivacurium is minimally dependent on the kidneys
for elimination. Minor prolongation of effect may be
observed due to reduced plasma
pseudocholinesterase. Cisatracurium and atracurium
are degraded in plasma by enzymatic ester hydrolysis
and nonenzymatic Hofmann elimination. These
agents may be the drugs of choice for muscle
relaxation in patients with renal failure.

18.  Vecuronium & Rocuronium
• The elimination of vecuronium is primarily hepatic,
but up to 20% of the drug is eliminated in urine. The
effects of large doses of vecuronium (> 0.1 mg/kg)
are only modestly prolonged in patients with renal
insufficiency. Rocuronium primarily undergoes
hepatic elimination, but prolongation by severe renal
disease has been reported.

19.  Pancuronium, Pipecuronium, Alcuronium,
& Doxacurium
• These agents are all primarily dependent on renal
excretion (60–90%). Although pancuronium is
metabolized by the liver into less active
intermediates, its elimination half-life is still
primarily dependent on renal excretion (60–80%).
Neuromuscular function should be closely
monitored if these agents are used in patients
with abnormal renal function.

20. Metocurine, Gallamine, & Decamethonium
• All three agents are almost entirely dependent on renal
excretion for elimination and should generally be avoided
in patients with impaired renal function.
 Reversal Agents
• Renal excretion is the principal route of elimination for
edrophonium, neostigmine, and pyridostigmine. The half-
lives of these agents in patients with renal impairment are
therefore prolonged at least as much as any of the above
relaxants. Problems with inadequate reversal of
neuromuscular blockade are usually related to other factors
.

21. Anesthesia for Patients with Renal
Failure
 Preoperative Considerations
ARF
CRF
Manifestations of Renal Failure
Metabolic
Hematological
Cardiovascular
Pulmonary
Endocrine
Gastrointestinal
Neurological

22. Preoperative Evaluation
o In Patients with acute renal failure a Optimal
perioperative management is dependent on
preoperative dialysis.
o In Patients with chronic renal failure regardless of the
procedure or the anesthetic employed, complete
evaluation is required to make certain that they are in
optimal medical condition; all reversible
manifestations of uremia should be controlled.
Preoperative dialysis on the day of surgery or on the
previous day is usually necessary.

23. o Physical and laboratory evaluation should focus on
both cardiac and respiratory functions
• Arterial blood gas analysis is useful in detecting
hypoxemia and evaluating acid–base status
• The electrocardiogram should be examined carefully for
signs of hyperkalemia or hypocalcemia as well as
ischemia, conduction blocks, and ventricular
hypertrophy
• Signs of fluid overload or hypovolemia should be
sought . Intravascular volume depletion often results
from overzealous dialysis.

24. o Preoperative red blood cell transfusions should
generally be given only to severely anemic
patients (hemoglobin < 6–7 g/dL) or when
significant intraoperative blood loss is expected.

25. o A bleeding time and coagulation studies are
advisable, particularly if regional anesthesia is
being considered. Serum electrolyte, BUN, and
creatinine measurements can assess the adequacy
of dialysis.
o Preoperative drug therapy should be carefully
reviewed for drugs with significant renal
elimination . Dosage adjustments and
measurements of blood levels (when available)
are necessary to prevent drug toxicity.

26.  Premedication
– Alert patients who are relatively stable can be given
reduced doses of an opioid or a benzodiazepine.
Promethazine, 12.5–25 mg intramuscularly, is a useful
adjunct for additional sedation and for its antiemetic
properties.
– Aspiration prophylaxis with an H2 blocker may be
indicated in patients with nausea, vomiting, or
gastrointestinal bleeding . Metoclopramide, 10 mg
orally or slowly intravenously, may also be useful in
accelerating gastric emptying, preventing nausea, and
decreasing the risk of aspiration

27.  Intraoperative Considerations
Monitoring
• Intraarterial, central venous, and pulmonary artery
monitoring are often indicated, particularly for patients
undergoing procedures associated with major fluid shifts
• Direct intraarterial blood pressure monitoring may also be
indicated in poorly controlled hypertensive patients regardless
of the procedure
• Aggressive invasive monitoring may be indicated, particularly
in diabetic patients with advanced renal disease undergoing
major surgery; this group of patients may have up to 10 times
the perioperative morbidity of diabetic patients without renal
disease

28. Induction
• Patients with nausea, vomiting, or gastrointestinal
bleeding should undergo rapid-sequence induction
with cricoid pressure
• The dose of the induction agent should be reduced in
debilitated or critically ill patients.
• Thiopental, 2–3 mg/kg, or propofol, 1–2 mg/kg, is
often used. Etomidate, 0.2–0.4 mg/kg, may be
preferable in hemodynamically stable patients.
• Ketamine , 1-2 kg for hemodynamically unstable pts
if pts are not hypertensive.

29. • An opioid, beta-blocker (esmolol), or lidocaine
may be used to blunt the hypertensive response
to intubation .
• Succinylcholine, 1.5 mg/kg, can be used for
endotracheal intubation if the serum potassium
is less than 5 mEq/L.
• Rocuronium (0.6 mg/kg), cisatracurium (0.15
mg/kg), atracurium (0.4 mg/kg), or mivacurium
(0.15 mg/kg) should be used for intubating
patients with hyperkalemia.

30. • Vecuronium, 0.1 mg/kg, may be a suitable
alternative, but some prolongation of its
effects should be expected.
• Use of a laryngeal mask airway, when
appropriate , usually avoids the excessive
sympathetic (hypertensive) response
sometimes associated with intubation and the
need for muscle paralysis.

31. Maintenance
• The ideal maintenance technique should be able to
control hypertension with minimal effects on cardiac
output, because an increase in cardiac output is the
principal compensatory mechanism for anemia.
• Volatile anesthetics, nitrous oxide, propofol, fentanyl,
sufentanil, alfentanil, remifentanil, hydromorphone,
and morphine are generally regarded as satisfactory
maintenance agents.
• Isoflurane and desflurane may be the preferred
volatile agents because they have the least effect on
cardiac output .

32. • Nitrous oxide should be used cautiously in
patients with poor ventricular function and
should probably not be used in patients with very
low hemoglobin concentrations (< 7 g/dL) to
allow the administration of 100% oxygen .
• Meperidine may not be a good choice because of
the accumulation of normeperidine . Morphine
may be used, but some prolongation of its effects
should be expected.
• Controlled ventilation should be considered for
patients with renal failure.

33. • Inadequate spontaneous ventilation with
progressive hypercarbia under anesthesia can
result in respiratory acidosis that may
exacerbate preexisting acidemia, lead to
potentially severe circulatory depression, and
dangerously increase serum potassium
concentration

34. Fluid theraphy
• Superficial operations involving minimal tissue
trauma require replacement of only insensible
fluid losses with 5% dextrose in water.
• Procedures associated with major fluid losses or
shifts require isotonic crystalloids, colloids, or
both .
• Lactated Ringer's injection is best avoided in
hyperkalemic patients when large volumes of
fluid may be required, because it contains
potassium (4 mEq/L); normal saline may be used
instead.

35. • Glucose-free solutions should generally be used
because of the glucose intolerance associated
with uremia.
• Blood that is lost should generally be replaced
with packed red blood cells.
• Blood transfusion either has no effect or may be
beneficial for patients in renal failure who are
candidates for renal transplant; transfusion may
decrease the likelihood of rejection following
renal transplantation in some patients

36. Thank you &
GOOD LUCK

37. positioning
Assignment
common positioning
their physiologic effect
their uses and complication

38. Commonly used position in urologic
surgery
• Lithotomy position
– Use
– Physiologic effects
• Trendelenburg
– Use
– Physiologic effects
• Lateral /kidney rest/flank
– Use
– Physiologic effects
– Complication

39. Common procedures in urology
• Bladder – cystoscopy, removal of stone,
suprapubic catheter
• Vaginal – VVF, RVF
• Prostate – TURP, open prostatectomy
• Urethral – urethroplasty , urethrectomy
• Scrotal – orchidopexy, orchidectomy,
hydrocelectomy
• Penile – penilectomy, hypospadia, circumcision,
phimosis

40. Cystoscopy
• Important to evaluate for treatment or diagnosis or
both
• Indication – hematurea, pyuria, trauma, cancer,
obstruction, calculi
• Anesthesia – dilatation of urethra , ureter, bladder,
by dilator are painful w/c needs anesthesia. Perhaps
some patients tolerate it.

41. • Choice of anesthesia
– With out anesthesia
– LA/cream/spray/jelly
– GA, slight sedation, ketamine &diazepam or opoids
– RA – SA
– Upper tract instrumentation – T-6 block
– Lower tract instrumentation - T-10 block

42. Hydrocelectomy , orchidopexy,
orchidectomy
• Indication
– Congenital neoplasm
– Testicular torsion
• Anesthesia
– RA – T-9 block is required for orchidopexy/ectomy
– GA – in children

43. Trans urethral resection of the
prostate (TURP)
• Its performed by special instrument called a
resectoscope (instrument having an electrode
capable for transmitting both cutting and
coagulating currents) with out incision simply
by inserting.
• Is often preceded by cystoscopy
• Continuous irrigating fluid is used to distend
the bladder and to wash away blood and
dissected prostatic tissue.

44. Irrigating fluids
• Distilled water
– Provide least interference with visibility but
absorption of large amount of water can lead to
excessive dilutional hyponatremia which results in
hemolysis of RBC, water intoxication and CNS
symptoms ranging from confusion to convulsion
and coma.
– So distilled water is abandoned

45. • Electrolyte solution
– NS/RL do least harm when absorbed into
circulation , but they are highly ionized and
promote dispersion of high current from
resectoscope .

46. • Non-electrolyte solution consisting sorbitol
and Mannitol(cytal) or glycin 1.5%
– Which are slightly hypo osmolar to the blood
– Have been used most often
– Since the prostate gland contains large venous
sinuses, it is inevitable that irrigating solutions will
be absorbed.

47. • The volume of irrigating fluids absorbed depend
on
– Hydrostatic pressure deriving fluid in to prostatic veins
and sinuses which is determined by
• Height of container must>60cm
• Cystoscopic site
• Flow rate
– Experience and technique of surgeon
• Maximum duration 1-2hrs
• Amount is proportional to duration
• 10- 30 ml /min of resection.

48. – Number /size of venous sinuses opened during
resection
• Ideal irrigating solutions for TURP are iso-osmolar,
weakly or non ionized, non- hemolytic, transparent ,
non – metabolized , non –toxic , rapidly excreted and
inexpensive
• But there is no ideal irrigating fluid
• Now a day’s most common irrigating fluid for TURP are
– Glycin and Mannitol

49. Anaesthesia management
o GA/SA
• Patients are old with co – existing disease
• Patient should not move , other wise
sphincter perforation.
General anaesthesia
– Adequate depth to prevent coughing & movement
– Movement cause bladder / prostate capsule
perforation , so increase bleeding
– Disadvantage of GA is it masks early symptoms of
TURP syndrome

50. Regional anesthesia
Advantages
• Improves sugical exposure – bladder atony
• Easier to detect TURP syndrome because patient is
awake
• More rapid hemostasis
• Reduce operative blood loss
• Decrease RBF

51. COMPLICATION OF TURP
I. TURP syndrome (water intoxication
syndrome)
 Syndrome due to excessive absorption of
irrigating fluid
• Reflects absorption of excessive amount of
irrigating fluids leading to
a) Dilutional hyponatremia
b) Hypervolumia
c) Hypo-osmolarity
d) Adverse hemodynamic and CVS changes

52. Sign and symptom
During RA
 Awake patient initially xzed by headache ,
confusion, N/V, dizziness, restlessness,
hypertension, stupor, seizure, coma,
bradycardia, skeletal muscle twiching
 All signs and symptoms are effects of
irrigating fluids

53. During GA
 Less specific , unexplained tachycardia or bradycardia,
pulmonary edema , cardiac dysarrhythmia,
 ECG evidence occurs when – when Na+ < 115 meq/l
- widen QRS
complex
- elevation of ST
segment

54.  CNS symptoms
-significant when serum Na+ <120
meq/l
-confusion, restelessness,
dizziness, coma
-visual disturbance

55. • Treatment
– Notify the surgeon
– Stop the surgery as soon as possible
– Fluid restriction
– Diuretics – to remove excess fluid
– Administer Na+ with careful measurement
• 0.9% N/S – conc Na+ > 120 meq/l
• 3% N/S – conc Na+ < 120 meq/l

56. II. Perforation of the bladder
can be due to
• Difficult resection made by cutting loop
• Over distention of bladder by irrigating fluid
• In adequate anesthesia
Perforation of prostatic capsule is suspected if the
irrigation fluid fails to return as it should
.

57. Management
1. Generally excreted by the kidney
2. Catheter drainage
3. Surprapubic drainage best, most
efficient for removing collecting fluid

58. III. Bactermia/sepsis /fever
– Common occurrence following TURP
– Prostatitis should be controlled prior to surgery
– Sudden cardio vascular collapse folllowing TURP is the
most common sign and symptom
Treatment
Broad spectrum antibiotics

59. IV. Blood loss
Estimation of blood loss is difficult (
15ml/mi/gm of prostate
Blood loss is related to
Vascularity of the gland
Surgeon technique and experience
Weight of prostate gland
Length of operation

60. Treatment
Blood , fluid
 Blood transfusion should be based on pre op hct ,
clinical assessment of the patient , duration /
difficulty of resection
 Generally prostate mass 30-80 gm;2 unit and if
>80gm ; 4 unit of blood should be prepared

61. V. Hypothermia
Older patients has thermoregulatory impairment
due to decline in autonomic nervous system
Elderly patients tolerate hypothermia poorly
Causes ; -irrigating with cold fluid
-intravenous absorption of fluid
-cold operating room
-GA

62. Prevention and treatment
Use warm irrigating or iv fluid
Heating the room
Cover the patient with blanket
Oxygen administration
Analgesic like ……..

63. Open prostatectomy
• Can be performed through supra/retro pubic
or perineal approach
• Mostly in supine position
• The choice of using open or TURP is depend
on the size of the prostate
– Prostate gland >60-80gm are conventionally
removed by open prostatectomy to reduce the
morbidity associated with TURP

64. • Anesthesia consideration
– The choice of anesthesia is influenced by status of
patient (CVS/PS & mental status )
– Uncooperative confused patient need GA
– GA
• Control of ventilation of lung
• Ensuring adequate oxygenation

65. – RA
• Simple to administer
• Post op analgesia
• Reduce operative blood loss
• Lessen post op agitation and restlessness
– Post op complication
• Blood loss
• Nerve injury
• DVT
• Blockage of irrigation

66. Nephrectomy
• Indication
– neoplasm / renal tumor – most common
– Hydronephrosis
– Chronic infection of the kidney
– Trauma
– Cystic/caliculi disease of the kidney
– Transplantation of the kidney

67. • Anesthesia
– GA in lateral / flank position
– Preoperative
• Asses renal function
• Anemia may accompany impaired renal function
– Patient require ETTI
– Pay attention for position of the upper and lower
limbs  insert a cotton b/n the legs on the knee
and ankle , pad pressure points

68. – Good relaxation is important
– Better to use atracurium or mivacurium
– Do not use pancuronium and gallamine
– EBL~500 ml
– Duration ~ 2-3 hrs

69. – As the legs are dependent, venous return
decreasesthis may be exacerbated by kinking the
inferior venacava as a result of the position of the
kidney
– After positioning of the patient correct placement of
ETT should be checked , incase inadvertent extubation
or endobronchial intubation has been occurred
– Complication
• Nerve injury
• Hypotension
• pneumothorax

70. • Pylolithotomy
– Removal of renal pelvic stone
– Anesthesia same as nephrectomy
• Penilectomy
– Removal of penis
– GA (prepare blood)

71. • Minor procedures
A. Circumcision – surgical removal of the foreskin
B. Phimosis – contraction of the prepuce usually
treated by circumcision
C. Paraphimosis – retraction of the prepuce
behined the glans penis with inability to restore
it to the normal position
Anesthesia (A-C)
All are children
Mask induction with pre cordial stethoscope

72. • Epispadia
– A congenital malformation in which the urethra
opens on the dorsum of the penis
• Hypospadia
– Malformation of the lower wall of the urethra, so
that the urethra opens on the under surface of the
penis
Anesthesia
– GA with ETTI or SA

73. Home take message
• Always you should change your anesthetic
management according to the status of the
particular patient. You may intubate a patient
even if it is done for most of the patients with
only halothane and mask. Rigidity should be
avoided in anesthesia.

74. Reading assignment
• Extracorporeal shock wave lithotripsy(ESWL)
– Physiologic effects of immersion
– Anesthetic consideration
– Contraindications
– complications

75. Extracorporeal Shock Wave
Lithotripsy
• What is shock wave lithotripsy?
– Shock Wave Lithotripsy (SWL) is the most common
treatment for kidney stones &uretral stone in the
U.S. Shock waves from outside the body are
targeted at a kidney stone causing the stone to
fragment. The stones are broken into tiny pieces.
lt is sometimes called ESWL: Extracorporeal Shock
Wave Lithotripsy.

76. • These are what the words mean:
ESWL
–extracorporeal: from outside the body
– shock waves: pressure waves
– lithotripsy (the Greek roots of this word are "litho"
meaning stone, "tripsy" meaning crushed)

77. • ESWL a nonsurgical technique for treating stones in
the kidney or ureter (the tube going from the kidney
to the bladder) using high-energy shock waves.
Stones are broken into "stone dust" or fragments
that are small enough to pass in urine. lf large pieces
remain, another treatment can be performed

78. • Very large stones cannot be treated this way.
• The size and shape of stone, where it is lodged
in your urinary tract, your health, and your
kidneys' health will be part of the decision to
use it.
• Stones that are smaller than 2 cm in diameter
are the best size for SWL. The treatment might
not be effective in very large ones.

79. • SWL is contraindicated
– In the following pts
– Because x-rays and shock waves are needed in
SWL,
– pregnant women with stones are not treated this
way.
– People with bleeding disorders,
– infections,

80. • severe skeletal abnormalities, or who are
morbidly obese also not usually good
candidates for SWL.
• lf your kidneys have other abnormalities,
• lf you have a cardiac pacemaker,

81. • What does the treatment involve?
– Pts will be positioned on an operating table. A
soft, water-filled cushion may be placed on your
abdomen or behind your kidney.
– The body is positioned so that the stone can be
targeted precisely with the shock wave. In an
older method, the patient is placed in a tub of
lukewarm water.

82. • About 1-2 thousand shock waves are needed to
crush the stones. The complete treatment takes
about 45 to 60 minutes
• Sometimes, insert a tube via the bladder and thread
it up to the kidney just prior to SWL. These tubes
(called stents) are used when the ureter is blocked,
when there is a risk of infection and in patients with
intolerable pain or reduced kidney function.

83. • After the procedure, you will usually stay for
about an hour then be allowed to return home if
all goes well.
• You will be asked to drink plenty of liquid, strain
your urine through a filter to capture the stone
pieces for testing, and you may need to take
antibiotics and painkillers.
• Some studies have reported stones may come
out better if certain drugs (calcium antagonists or
alpha-blockers) are used after SWL

85. • Does the patient need anesthesia?
– General anaesthesia (GA) for SWL treatment offers
optimized pain control and controlled respiratory
excursion. This creates optimal conditions for
stone targeting and consecutive fragmentation. In
modern anesthetic practice, GA is considered to
be safe with a low morbidity. However, it seems
preferable to avoid, if not mandatory, especially in
high-risk patients.

86. • Disadvantages are the need to involve an
anesthetic specialist and the need for
postoperative recovery, increasing the overall
costs and making GA less suitable in the
common outpatient SWL setup of most
urological departments. Solely in children or in
extremely anxious patients, it is still the
preferred option.

87. • Other potential indications are particularly
long treatments as in patients with bilateral
stones, concomitant renal and ureteral stones
or in patients with very hard calculi (cystine,
calcium oxalate monohydrate, or brushite),
which are known to be resistant to
fragmentation and require high, potentially
painful energy levels

88. • Inhalation Anaesthesia with Nitrous
OxideNitrous oxide is a medical anesthetic gas
and on the market as Entonox, a mixture of 50%
nitrous oxide and 50% oxygen.
• It was discovered in 1776 by Joseph Priestly [18]
and constitutes another analgesic option for SWL
treatment. This colourless gas is highly soluble in
blood and the arterial concentration reaches a
plateau 10 minutes after commencing the
inhalation.

89. • It diffuses rapidly through the cellular
membranes, does no bind to haemoglobin,
and is eliminated unchanged via the lungs.
The analgesic effect commences 20 to 30
seconds after inhalation and a peak effect is
reached after 3 to 5 minutes.

90. • Reflexes of coughing and airway protection are
not noticeable altered [18]. This rapid onset and
quick loss of effect make nitrous oxide an
attractive option for day-case procedures.
• Especially in treatments of short duration such as
SWL, Entonox can be used in spontaneously
breathing patients to provide analgesia.
Regarding its analgesic effect, the concentration
of 30% of nitrous oxide is reported to be
equivalent to 10–15 mg of morphine

91. • Adverse effects of Entonox are mainly transient
nausea and light headedness. A further issue can
be slight cardiac depression; therefore, the gas
should be used carefully in patients with
congestive heart failure and in those with
obstructive airway disease [20]. It is
contraindicated in patients with pathological air-
filled body cavities (pneumothorax or obstructed
bowels) as nitrous oxide is diffusing into these,
consecutively increasing volume and pressure
therein.

92. • The use of Entonox during SWL was reported in
only one RCT study up to now; 150 patients
undergoing treatment where randomized into 3
groups, one to receive Entonox, the other to have
intravenous pethidine, and the last one to inhale
compressed air. A significantly reduced
procedure-related pain (P = 0.001) for nitrous
oxide could be shown and it proved as effective
as intravenous administered pethidine

93. • IMMETION EFFECT