Anesthesia for Urologic Procedures Flashcards
What kind of patient populations do you see for urologic procedures?
patients may be of any age; most are elderly with coexisting medical illnesses
What should you consider anatomically about the ureter openings?
they are posterior and inferior on bladder itself
What drugs can be administered to find the ureter openings?
methylene blue and indigo carmine
What nerve lies close to the ureters and can be stimulated during cautery?
obturator nerve
How do the kidneys get their blood supply?
Via the renal arteries that branch off the aorta
How much of the CO do the kidneys get?
25% or 1200 mL/min
What MAP range are the kidneys able to autoregulate?
75-160 mmHg
What happens in the kidneys if the MAP drops below 60 mmHg?
filtration ceases
Where do the kidneys lie in the body?
retroperitoneal between T12 and L4 vertebrae
What level somatic blockade do you need to have if using spinal anesthesia for a urologic procedure?
T8-L3
What level of somatic blockade do you need for a procedure on the ureters?
T10 sensory level
How does anesthesia affect renal function?
reversible decreases in RBF, GFR, urinary flow, & Na+ excretion occur during regional or general anesthesia
What can partially offset the effects of anesthesia on renal function?
normal BP and intravascular volume
What is the most frequently used position for urologic procedures?
lithotomy
What should you consider when moving the patient’s legs into lithotomy position?
moving them simultaneously
What are some of the respiratory physiologic consequences of lithotomy position?
decreased FRC, decreased vital capacity, lung volume, and lung compliance which can result in atelectasis and hypoxemia
What are some of the cardiophysiologic consequences of lithotomy position?
altered venous return, acute increase or decrease in BP which is why you should always check the BP once the legs are raised
What nerve is commonly injured in the lithotomy position?
peroneal nerve with loss of dorsiflexion due to fibular head compression
What are some risk factors for nerve injury in the lithotomy position?
duration >4 hours
BMI
What other injuries (besides peroneal) can occur with the lithotomy position?
sciatic stretch
hand/finger injuries as foot of table is lowered
incidence of back pain (as high as 37%)
What are some of the physiolgoic consequences of extreme lithotomy?
increased central venous pressure which can result in cerebral edema (especially with a low BP since CPP = MAP - ICP)
facial edema/airway edema
What nerve commonly gets injured in the extreme lithotomy position?
brachial plexus injury resulting from hyperabducted arm
How should you position someone in the lateral flexed position?
iliac crest over the table break; kidney rest up
lower leg flexed at knee/upper leg straight
pad between legs and axillary roll
extend table to separate iliac crest and costal margin
watch eye, ear, and neck position
What are some of the respiratory effects of the lateral flexed position?
- decreased FRC in the dependent lung
- VQ mismatching (greater blood flow in the dependent lung while greater ventilation to the nondependent lung)
- atelectasis in dependent lung and favors hypoxemia
What are some of the cardiac effects of the lateral flexed position?
decreased venous return
What is the hyperextended dorsal position?
lateral oblique position with table hyperextended, incision goes longitudionally up abdomen and up into thoracic area
What nerves can be injured in the hyperextended dorsal position?
brachial plexus peroneal saphenous ulnar back strain
What complication is the patient at risk for in the hyperextended dorsal position?
VAE due to pelvis being above heart
Where is the hyperextended supine position?
iliac crest over break in table and table extended then table tilted head down
What are some of the cardiac effects of the hyperextended supine position?
increased central venous volume which can cause airway edema/facial edema
What are the 3 common transurethral procedures?
cytoscopy
TURP
TURBT
What is the purpose of a cystoscopy?
Diagnosis of urologic problems
Resection of bladder tumors
Access to urinary system for stent placement
What types of anesthesia can you use for a cystoscopy?
local
MAC
Regional (T10 umbilicus)
General
What can be a heat source to start fires during a cystoscopy?
light on cystoscopy camera generates heat and when placed on drapes has the potential to start a fire
What is the common position for cystoscopies?
lithotomy with or without trendelenburg
What nerves can be injured during a cystoscopy?
sciatic
common peroneal
brachial plexus
What is a TURP procedure and why do we do them?
transurethral resection of prostate for BPH which causes obstructive uropathy
What is the size of the prostate gland in order to have a TURP?
prostate gland must be
What are the most common causes of death post-op after a TURP?
MI, PE, renal failure
What comorbidites do patients undergoing a TURP usually have?
pulmonary, cardiac, and renal disease (up to 60%)
What is the estimated surgical time and blood loss for a TURP?
1-2 hours
500 mL
What happens during the TURP procedure?
Performed with cautery loop resectoscope while bladder is continuously irrigated
What is a common complication with a TURP as a result of the continuous bladder irrigation?
excessive absorption of irrigation fluid into the large venous sinuses, cannot determine exact blood loss because of irrigation
What is the limit for resection time due to the continuous irrigation used?
What is the best way to keep track of how much fluid may have been absorbed?
Keep count of the irrigation bags used
What are the characteristics of the irrigation fluid used during a TURP?
non-electrolyte and hypotonic
About how many mLs per minute are absorbed during a TURP?
20 mL/min
How severe a dilutional syndrome is depends on what?
duration of resection and bag height, the higher the height the more pressure that is exerted on the bag
What physiologic disturbances do hypotonic solutions cause?
acute hyponatremia and hypoosmolality
What things can fluid overload with dilutional syndrome cause?
congestive heart failure
pulmonary edema
hypotension
When does dilutional syndrome occur with a TURP?
during procedure or immediately post-op
At what sodium level can you see confusion and restlessness?
120 mEq/L
At what sodium level can you see somnolence and nausea?
115 mEq/L
At what sodium level can you see seizures and coma?
110 mEq/L
How are most dilutional syndromes managed?
fluid restriction and loop diuretics
What is the final line of treatment for dilutional syndrome if fluid restriction and diuretics do not work?
administer 3% saline IV at no more than 100 mL/hr until sodium is above 125 mEq. Diurese with lasix and follow serum electrolytes
What is glycine toxicity?
caused by glycine put in irrigation fluid used for TURP
What is glycine/
inhibitory neurotransmitter in CNS
What is a byproduct of glycine metabolism?
ammonia which can also cause altered mental status and confusion
Why is glycine added to irrigation fluid
good optical effect and aids in prevention of dilutional syndrome
What can hyperglycemia from glycine toxicity lead to?
nausea, malaise, vomiting, confusion, stupid and coma, blindness, seizure
How can you treat glycine toxicity?
lasix and supportive therapy
What are 2 other complications that can occur during a TURP other than dilutional syndrome and glycine toxicity?
bladder perforation
severe blood loss/DIC
What happens if the surgeon perforates the bladder during a TURP?
irrigation goes into the abdomen causing abdominal pain, nausea, diaphoresis (may be masked by general anesthesia or heavy sedation)
What happens if there is severe blood loss during a TURP?
can result from glands 35-45 g or resection time >90 mins
resection may release fibrinolytic enzymes
dilutional thrombocytopenia
What is the obturator reflex during a transurethral procedure?
electrocautery stimulation causes an external rotation and adduction of thigh, patient’s legs will “box” surgeon, cannot be blocked by spinal anesthetic, only way to block it is with GA and paralysis
Can complication can occur for someone who is paralyzed pre-op undergoing a TURP?
autonomic hyperreflexia can occur if spinal cord lesion is above T6-T7, triggered by surgical manipulation, bladder distention; sympathetic hyperactivity from stimulation below cord lesion (will need anesthetic that can prevent this like a spinal)
Causes: severe HTN, bradycardia, and dysrhythmias