Anesthetic Considerations for Urologic Surgery Flashcards
What is a nephron?
outer cortex
inner medulla
How much cardiac output does a kidney receive?
20-25%
What are the three processes of the kidney that help with hemostasis?
filtration
reabsorption
tubular excretion
What is a normal GFR?
125ml/min
What nervous system innervates the kidney?
symapthetic nervous system
What are the six renal hormones?
aldosterone antidiuretic hormone angiotensin atrial naturetic factor vitamin D prostaglandins
What are the three effects of anesthetic drugs on the kidenys?
depress normal renal function
renal blood flow may decrease 30-40%
impairment of autoregulation
General anesthesia and kidney function is associated with a decrease in (4)
renal blood flow
GFR
urinary flow
electrolyte secretion
What do all volatile anesthetics due in the kidneys?
cause a mild increase in renal vasculature resistance
occurs in response to decrease in cardiac output and SVR
What 3 interventions can attenuate reductions in renal blood flow and GFR?
preoperative hydration, decreased concentrations of volatile anesthetics and maintenance of blood pressure
Sevoflurane has not been associated with
nephrotoxicity
Sevoflurane has been associated with what high levels? why?
fluoride
degraded by absorbants-> compound A (vinyl ether)
How can you decrease compound A toxicity?
high gas flows (1L/min FGF for 2 MAC hours max)
decrease gas concentration
use of carbon dioxide absorbents
What two volatile agents are not associated with nephrotoxicity?
isoflurane
desflurane (strongly resists biodegradation)
What is fluoride ion toxicity?
Fluoride interferes with active transport of sodium and chloride in loop of henle
Signs and symptoms of fluoride ion toxicity (5)
polyuria hypernatermia serum hyperosmolality elevated BUN and creatinine decreased creatinine clearance
What is nephrotoxicity related to?
dose, duration and peak fluoride concentrations
Fluroride ion toxicity are potent:
vasodilator and potent inhibitor of many enzyme systems (ADH)
Definition of Acute kidney injury
a renal functional or structural abnormality that occurs within 48 hours
increase creatinine 0.3mg/dl or 50% increase; UO<0.5ml/kg/hr x 6 hours
What increases the risk of acute kidney injury?
hypovolemia
electrolyte imbalance
contrast dye
Causes of prerenal AKI
hypoperfusion of the kidneys without parenchymal damage
Examples of prerenal AKI
hemorrhage, V/D, diuretics, sepsis, shock, CHF, norepinephrine, NSAIDs, ACEi
Causes of intrinsic AKI
result of damage to the renal tissue
Examples of intrinsic AKI
tubular injury due to hypoperfusion, myoglobin, chemotherapy, infections, lymphoma, toxemia of pregnancy vasculitis
Causes of Post renal AKI
due to urinary tract obstruction
Examples of post-renal AKI
renal calculi, peritoneal mass, prostate/bladder urethra tumor, fibrosis, hematoma, strictures
Four Risk factors of AKI
aging (> 50years, preoperative renal dysfunction)
comorbidities (cardiac and hepatic failure)
surgical procedures (cardiac bypass, aortic cross clamp, arteriography, intra-aortic balloon pump)
emergency or high risk procedures (ruptured AAA, ischemic times, large volume of blood transfusion)
AKI Preoperative Treatment includes
fluid deficits attenuation of surgical stress patient monitoring considerations (arterial line, TEE, CVP, foley catheter) fluid replacement improve cardiac output normalize systemic vascular resistance
What is the most difficult AKI to treat?
intra-renal
How are fluid deficits treated pre-operatively for AKI?
balanced salt solutions- minimize ADH and RAAS activation
Describe fluid replacement perioperative treatment for AKI
500-1000ml bolus for hourly urine output below acceptable levels
colloids may not be superior crystalloids
high risk pateints: 0.5-1ml/kg/hr
Are diuretics used to prevent oliguria?
no, not recommended
early treatment of which AKI has the best outcomes?
pre-renal
How is the prognosis for post-renal AKI?
good prognosis with early identification
What is the most common cause of AKI?
prolonged hypo-perfusion
How is the severity of AKI determined?
duration and magnitude of initial insult
What is the treatment of AKI?
administering volume (normal saline) to euvolemia
improving cardiac output by afterload reduction
normalizing SVR
What is the “key strategy” of AKI peri-operative treatment?
limiting magnitude and duration of renal ischemia
How much does renal function decrease per decade?
10%
When does chronic kidney disease exist?
GFR is less then 60ml/min/1.73m2 for three months
When do S&S appear for CKD?
until less then 40% of normal functioning nephrons remain
What symptoms are present with 95% loss of renal function?
uremia, volume overload adn CHF
Stage 1 CKD
kidney damage with normal GFR
Stage 2 CKD
GFR 60-89ml/min/1.73m2 with kidney disease
Stage 3 CKD
GFR 30-59ml/min/1.73m2
Stage 4 CKD
GFR 15-29ml/min/1.72m2
Stage 5 CKD
GFR <15ml/min/ 1.73m2 with end stage failure
What are the cardiovascular symptoms seen in CKD?
hypertension and CHF (90% volume dependent; 10% secondary to increase renin), pericardial effusion
pericarditis
ischemic heart disease
When is pericarditis seen?
in patients with severe uremia
What is the most common cause of death in CKD?
ischemic heart disease (better outcomes with CABG then angioplasty)
What are the respiratory and neurologic effects of CKD?
respiratory depression secondary to delayed clearance
fatigue and weakness are early complaints
autonomic neuropathy
What are the hematologic effects of CKD?
normochromic, normocytic anemia and prolonged bleeding
How does CKD effect hematologic function?
decrease in erythropoietin production
reduction in erythrocyte life secondary to dialysis
blood loss from frequent sampling
decrease in platelet function
dialysis within 24 hours will correct bleeding
What increases levels of factor VIII?
desmopressin
Who is at higher risk for GI bleeding?
dialysis patients
What immune system changes occurs in CKD?
protein malnutrition
neutrophil, mococyte and macrophage changes
What endocrine system changes occurs in CKD?
hyperparathyroidism
adrenal insufficiency
What electrolyte changes occurs in CKD?
sodium wasting
hypocalcemia
hyperkalemia
What are the treatments to hyperkalemia?
25-50 grams of dextrose
10-20 units of regular insulin
50-100mEq of sodium bicarb
When should pre-operative levels of K be checked?
within 6-8 hours of surgery even if dialysis is performed
What are the physiologic effects of dialysis?
hypotension, muscle cramping, anemia, nutritional depletion
What are fluid management considerations with anesthesia in CKD?
UO 0.5-1ml/kg/hr recommended
mildly compromised function: balanced salt solution 3-5ml/kg/hr with 500ml bolus as needed
What fluids are contraindicated in anuric patients?
potassium containing solutions (LR)
Blood products are administered to CKD patients who
need increased oxygen carrying capacity
How are fluids managed in renal insufficiency/ ESRD?
replacement volume deficit pre-operatively
intraoperative losses greater than 15% should replaced with colloid 1:1
crystalloid without potassium at 2-3ml/kg/hr
How are fluids managed in the dialysis patient?
insensible loses- replace with 5-10ml/kg oof D5W
if urine is produced- replaced with 0.45% saline
What is a normal serum creatinine?
0.7-1.5mg/dL
For every 50% reduction in GFR, what will double?
serum creatinine
What is a normal BUN ?
blood urea nitrogen
10-20mg/dL
What is a normal BUN: Creatinine ratio?
10:1
What is a normal creatinine clearance?
95-150ml/mi
What is the most reliable test for renal function?
creatinine clearance
What does creatinine clearance measure?
glumerular ability to excrete creatinine in urine
mild dysfunction 50-80ml/min
moderate dysfunction <25ml/min
<10mL/min requires dialysis
How is pharmacologic sensitivity increased in CKD?
reduced protein binding
What opioid and opioid metabolite is not removed by dialysis?
morphine
normerperidine
What class of drug is highly dependent on renal excretion?
H2 blockers
Regional anesthesia is a good option for CKD patients, but what are some concerns?
intolerance
coagulopathy
peripheral neuropathy
risk of infection
Is block duration affected by renal failure?
no
What are considerations for spinal and epidural placement in CKD?
platelet count
PT/PTT
ASRA coags
What are pharmacokinetic properties of IV drugs during GA with CKD patients?
increased volume of distribution
decreased protein binding
low pH
renal excretion
What drugs are less protein bound in CKD?
ketamine and benzodiazepines
How is precedex cleared?
by the liver
What opioid has reduced clearance in patients with ESRD?
remifentanil
what is the precursor molecule to succinylcholine?
succinylmonocholine
Cholinesterase deficiency occurs in what type of patients?
uremic patients
Pancuronium is X% excreted where?
80% in the urine
What NMD duration is not increased in renal failure?
atracurium, cisaturacurium and mivacurium
Vecuronium and renal disease
approximately 30% excreted via renal system
effects rapidly revered with dialysis
Rocurinium and renal disease
reduces clearance by almost 40%
After major surgery, when should dialysis patients get dialysis?
24-36 hours after
What may uremic patients require for replacement?
red blood cells
fresh frozen plasma
colloid solutions
What is cystoscopy?
urologist uses a cystoscope to examine urethra and bladder
procedures can be quick or last hours
What are anesthetic considerations for cystoscopy?
Local/MAC, Spinal anesthesia (offers relaxation with real-time patient assessment), general anesthesia (LMA vs ET)
What position are patients in for a cystoscopy?
lithotomy
ESWL
extra-corporeal shock wave lithotripsy
non-invasive treatment that uses high energy ultrasound waves to break up the calculi
When is intervention required for nephrolithiasis?
renal calculi are >10mm
What is common with ESWL?
hematuria
What EKG placement is important in ESWL?
R wave used to trigger shocks
What are ESWL contraindications?
active uti
uncorrected bleeding disorder or coagulopathy
distal obstruction
prengnacy
What are complications to ESWL?
dose dependent hemorrhagic leisons on kidneys
perforation, rupture or damage to colon, hepatic structures, lung, spleen, pancreas, abdominal aorta or iliac veins
hematuria develops in most patients
diabetes, new onset HTN or decreased renal function
What type of anesthesia can be used for ESWL?
GA (rapid onset, can control patient movement)
Spinal/epidural (t4/t6)
MAC
topical LA
What are anesthetic considerations for ESWL?
d/c ASA, anticoagulants, platelet inhibitors and NSAIDs 7-10 days prior to procedures
document negative urine culture
HCG (ionizing radiation)
laser eye protection
What is percutaneous nephrolithotomy?
procedure to remove kidney stones 25mm or smaller with rigid scope inserted in renal calyx under fluoroscopy
Complications of percutaneous nephrolithotomy?
anaphylaxis bleeding pain fever pneumothorax, hemothorax renal colic septicemia UTI
What class of medications is used to manage benign prostatic hyperplasia?
alpha blocking agents
What is the most common surgical procedure for men over 60?
TURP
Transurethral resection of the prostate
What is a TURP?
scope placed through urethra to cut away obstructing lobes of prostate
bladder distended and continuous irrigation used
What are the anesthetic risk related to with TURPs?
patient age and associated comorbidities
How is TURP commonly performed?
General anesthesia
How is spinal anesthesia associated with TURP?
better anesthetic choice as it detects signs and symptoms of complications
TURP syndrome
rare, but significant complication with mortality as high as 25%
large amount of fluid absorbed through the prostate
What are the hallmark symptoms to TURP syndrome?
related to combination of water intoxication, fluid overload, and hyponatremia fluid overload water intoxican hyponatremia glycine toxicity
What are signs of fluid overload in TURP syndrome?
HTN bradycardia arrhythmia angina, pulmonary edema, CHF hypotension
What are signs of water intoxication in TURP syndrome?
confusion, restlessness, seizure, lethargy, coma, dilated sluggish pupil
What are signs of hyponatremia in TURP syndrome?
CNS changes, widened QRS, T wave inversion
What are signs of glycine toxicity?
N/V, headache, transient blindness and myocardial depression
What irrigation solutions cause TURP?
distilled water
saline
cytal (sorbitol and mannitol)
glycine
What is the most common fluid used in TURP?
glycine
What are complications of TURP syndrome?
bleeding bladder perforation cardiac effects dilutional hyponatremia with hypo-osmolality hyperglycemia hypothermia glycine absorption infection renal toxicity (glycine) skin burns volume overload with pulmonary edema
What devices have a greater incidence for skin burns during TURP syndrome?
monopolar cutting devices
What is fluid absorption dependent on (TURP)
size of resection duration of resection irrigation of solution pressure number of venous sinuses open at one time provider experience
How much fluid can be absorbed per minute in TURP?
30ml
How much fluid can be absorbed in 2 hours in TURP?
8L
What happens to serum Na with fluid absorption from TURP?
uptake of 1L of irrigant can decrease serum Na 5-8mEq/L
serum Na <120meq/l associated with severe reactions
What is glycine?
amino acid that acts as inhibitory transmitter
What can excessive glycine absorption cause?
nausea and vomiting fixed and dilated pupils headache weakness muscle incooridination TURP blindness seizures hypotension
How can you avoid TURP syndrome?
prevention!
avoid trendelenburg position
limit resection to less than one hour
place irrigating solution less then 60cm above prostate
monitoring electrolytes
use regional techniques with light sedation
How do you treat TURP syndrome?
early recongition correcting hyponatremia 20mg IV furosemide Labs (Hct, electrolytes, creatinine, glucose, ABG, 12 lead EKG) IV midazolam 1mg for seizures intubate for pulmonary edema PRBCs if needed investigate for DIC or primary fibrosis
How do you correct hyponatremia?
3-5% saline <100ml/hr
increase sodium 0.5mEq/hour or 8mEq/day
goal is sodium greater then 120mEq/l
rapid reversal can result in osmotic demyelination syndrome
What are anesthetic concerns with laparoscopic urologic surgery?
pneumoperitoneum
urologic system is retroperitoneal- communicates with thorax- risk for SQemphysema
alterations in renal adn hepatic perfusion
CO2 absorption (potential acidosis)
extremes in patient position (increased intra-abdominal and intrathoracic pressures)
hemorrhage
What are the two types of popular robotic urologic surgeries?
upper tract surgery (simple or radical nephrectomy, radical nephrouretectomy, nephron sparing surgery
Pelvic surgery: radical cystectomy, radical prostatectomy
What are position considerations for robotic urologic surgery?
steep trendelenberg (+ lithotomy for prostatectomy) arms tucked at sides
What are airway concerns for robotic urologic surgery?
airway assessment prior to extubation
What is the duration and EBL for robotic urologic surgery?
3-4 hours
<300ml
What are some considerations for robotic urologic surgery?
limit fluids until urethra is recommended (2 L total IVF)
large bore PIV +/- arterial line
DVT prophylaxis, eye protection, OGT, bair hugger, antibiotics, dexamethasone, remifentanil infusion common
Anesthetic considerations for Nephrectomy
Open vs laparoscopic lateral jack-knife position cardiovascular compromise third spacing and edema hemodynamic monitoring postoperative pain management
What is the mainstay treatment for ESRD?
renal transplant
What is the most frequent solid organ transplant?
kidney
Where is the transplanted kidney placed?
right or left extraperitoneal fossa (right side preferred)
attached via vascular anastomoses of external iliac artery and vein and ureter anastomosed to bladder
