Anaesthesia in Urology Flashcards
What anaesthetic techniques can be considered for cystoscopy?
- Viscous lidocaine topical anaesthesia
- sufficient for diagnostic studies in most woman (short urethra) - GA for kids
- RA (T10 ok) / GA for adult males
What problems are associated with the lithotomy position
- Inadequate pressure point protection
- Pressure sores
- Nerve injuries (NB position of joints)
- Compartment syndrome - Decreased FRC
- Leg elevation –> increased venous return (CCF)
- Leg lowering –> hypotension
What are 5 most common complications of TURP
- CLOT retention
- Failure to void
- Uncontrolled hematuria (rqring surgical revision)
- UTI
- Chronic hematuria
What are the 5 rarer complications of TURP
- TURP syndrome
- Bladder perforation
- Sepsis
- Hypothermia
- DIC
How does the TURP syndrome occur
- Prostate resection exposes extensive prostatic venous plexus to copious amounts of irrigation fluid –> absorption of excessive irrigation fluid –> TURP syndrome
What is the incidence of TURP syndrome
1%
Why can’t electrolyte solutions be used for irrigation during TURP
Electrolyte solutions disperse the electrocautery current
Water provides excellent visibility because its hypotonicity lyses red blood cells
What are the manifestations of the TURP syndrome
- Hyponatraemia
- Hypo-osmolality
- Fluid overload
- -> CCF
- -> Pulmonary oedema
- -> Hypotension - Hemolysis
- Solute toxicity
- -> Hyperglycinaemia (glycine) - CVS and CNS toxic
- -> Hyperammoninemia (glycine) - CVS and CNS toxic
- -> Hyperglycaemia (sorbitol)
- -> Intravascular volume expansion (mannitol)
What are the principles of management of the TURP syndrome
- ABCDE
- Fluid Restriction
- Furosemide
- HypoNa with seizures:
- Hypertonic NaCl
- Midazolam (2 - 4mg)
- Phenytoin (10 - 20mg/kg)
When is bladder perforation suspected during urological surgery
Anaesthetised patients:
1. Poor return of irrigating fluid
Awake patients
- N, V
- Diaphoresis
- Retropubic and LAP
If large
- -> unexplained hypertension/hypotension
- -> Vagal bradycardia
List the various causes of coagulopathy during TURP
- Release of thromboplastins into circulation during the procedure –> DIC
- Dilutional thrombocytopaenia
- Ca prostate –>Secretion of fibrinolytic enzyme
How can TURP cause septicaemia
Prostate often harbors chronic infection –> bacteraemia
What are the advantages of RA vs GA for TURP
RA
- Decreased postop VTE
- Less likely to mask symptoms of TURP syndrome
- Less likely to mask symptoms of bladder perforation
- Acute hyperNA from TURP migh delay emergence from GA
Why is monitoring of blood loss difficult in TURP
Dilution with withdrawn irrigation fluid
on average 3 - 5ml/min of procedure (200 - 300ml)
–> Transfusion seldom required
How does Extracorporeal Shock Wave Lithotripsy work
Directed high energy sound waves directed at the stone travel through tissue (same acoustic density as water) until reaching the stone where the acoustic impedance changes which causes shear and tear forces on the stone causing it to fragment.
Ureteral stents are placed cystoscopically prior to the procedure
Tissue destruction can result if the acoustic energy is inadvertently directed towards an air fluid interface (e.g.lung or intestine).
Which patients are at risk during Extracorporeal Shock Wave Lithotripsy
Cardiac patients
- at risk of dysrhythmia
- with pacemaker
- with implantable cardiac defibrillator
ESWL can cause dysrhythmia and dysfunction of implanted devices
(ESWL can damage internal components)
How can risk of dysrhythmia be mitigated during ESWL
Synchronization of the shock ways with the ventricular refractory period (20 ms after the R wave)
Asynchronous shock waves may be safe in patients without cardiac disease
What are the haemodynamic effects of immersion in a bath of water at 37 deg C
Warm water –> initial VD –> hydrostatic pressure of water redistributes venous blood centrally –> overall increase in SVR–> elevation in BP –> can precipitate CCF
Increased thoracic blood volume can decrease FRC by 30 - 60% –> predisposition to hypoxia
What type of anaesthesia is used with ESWL
Newer lithotripsy units (no water bath required)
- use conscious sedation
Older water bath lithotripsy
- Continuous epidural anaesthesia with sedation
What is the disadvantage of RA for ESWL
Inability to control diaphragm movement which may move the stone in an out of wave focus
What problems does the lateral flexed or ‘kidney rest’ position bring about for the anaesthetist and why
- VQ mismatch
Decreased FRC dependent lung
Increased FRC nondependent lung
Dependent lung –> greater blood supply and reduced ventilation –> atelectasis + SHUNT –> hypoxemia
Nondependent lung –> reduced blood supply and better ventilation –> DEAD SPACE
- Reduced venous return
- elevation of the ‘kidney rest’ position can lead to compression of the vena cava
What indicates the presence of increased dead space in the lateral flexed ‘kidney rest’ position?
Increased A - a PCO2 as less CO2 is moving into non-perfused alveoli (dead space alveoli)
Which operations are performed with the patient in the hyperextended supine position and describe this position
Iliac crests just over the break in the operating table with the torso/chest and head on a declining ramp and the legs on also on a declining ramp with the fulcrum the patients pelvis
- Pelvic LN dissection
- Retropubic prostatectomy
- Cystectomy
What is the ‘frog leg position’
Variation of hyperextended supine
- Knees flexed
- Hips aBducted
- Hips externally rotated
Why is GA the most appropriate technique to use for TURBT and how does this surgery differ from TURP
Lateral tumours - the cautery resectoscope results in stimulation of the obturator nerve which causes adduction of the legs
Requires GA with paralysis.
No Risk of TURP syndrome
