Anesthetic considerations for urologic surgery Flashcards
How much cardiac output does the kidney receive?
20-25%
The nephron is made up of
outer cortex & inner medulla
Homeostasis is maintained in the kidney through
filtration
reabsorption &
tubular excretion
Normal GFR is
125 mL/min
Up to ____ of the filtrate is reabsorbed
99%
Things that should not be seen in the urine include
glucose, protein, bilirubin
The renal vasculature is innervated by
SNS
Renal hormones include
aldosterone, antidiuretic hormone, angiotensin, atrial naturetic factor, vitamin D, prostaglandins
Catecholamines result in a
decrease in urine output
Anesthetic drugs affect the kidneys by
depress normal renal function
impairment of autoregulation
renal blood flow may decrease by 30-40%
General anesthesia is associated with a decrease in
renal blood flow GFR urinary flow electrolyte secretion -similar changes occur after spinal & epidural anesthesia- magnitude of change parallels degree of sympathetic block & BP depression
All ______ cause mild increase in renal vascular resistance
volatile anesthetics
-compensatory mechanism in response to decreases in CO & SVR
Historically________ caused high fluoride ion concentrations & _________ characterized by polyuria
methoxyflurane; nephrotoxicity
These factors attenuate reductions in renal blood flow & GFR
preoperative hydration, decreased concentrations of volatile anesthetics, & maintenance of blood pressure
Sevoflurane has not
been associated with nephrotoxicity even though it has been associated with high fluoride levels
Sevoflurane produces
Compound A which can potentially cause nephrotoxicity
In an effort to decrease risk of compound A with sevoflurane,
use high gas flows (1L/min FGF for 2 MAC-hours max)
decrease gas concentration
use of carbon dioxide absorbents
Isoflurane & desflurane are
not associated with nephrotoxicity
Signs and symptoms of fluoride nephrotoxicity include
polyuria hypernatremia serum hyperosmolality elevated BUN & creatinine decreased creatinine clearance
Nephrotoxicity with volatile anesthetics is related to
dosage, duration, & peak fluoride concentrations
Fluoride ion toxicity
fluoride interferes with active transport of sodium & chloride in the loop of Henle
POTENT VASOCONSTRICTOR
potent inhibitor of many enzyme systems (ADH
Nephrotoxicity results in
proximal tubular swelling & necrosis
An acute kidney injury is defined as
a renal functional or structural abnormality that occurs within 48 hours- increase in creatinine 0.3 mg/dL or 50% increase; UO <0.5 mL/kg/hr x 6 hours
Risk for acute kidney injury is increased by
hypovolemia, electrolyte imbalance, & contrast dye
Types of AKI include
prerenal, intrinsic, & post renal
Describe the cause of prerenal AKI
hypoperfusion of the kidneys without parenchymal damage
Describe the cause of intrinsic AKI
result of damage to renal tissue
Describe the cause of postrenal AKI
due to urinary tract obstruction
Provide examples of prerenal AKI
hemorrhage, vomiting, diarrhea, diuretics, sepsis, shock, CHF, norepinephrine, NSAIDs, ACE-I
Provide examples of intrinsic AKI
tubular injury due to hypoperfusion, myoglobin, chemotherapy, infections, lymphoma, toxemia of pregnancy, vasculitis
Provide examples of postrenal AKI
renal calculi, peritoneal mass, prostrate/bladder urethra tumor, fibrosis, hematoma, & strictures
Risk factors for AKI include
aging- >50 years of age, preoperative renal dysfunction
comorbidities- cardiac failure & hepatic failure
surgical procedures- cardiac bypass, aortic cross-clamp, arteriograpy, intra-aortic balloon pump
emergency or high risk procedures- ruptured AAA, ischemic time, large volume of blood transfusion
Describe how to mitigate risks of AKI
hydration, limit contrast dye, diuretics
Anuric is defined as
UO <100 mL/day
Polyuric is defined as
UO >2.5L/day
Oliguric is defined as
UO <400 mL/day
AKI preoperative treatment includes
fluid deficits- BALANCED SALT SOLUTION ( NS) to minimize ADH & RAAS release
attenuation of surgical stress
patient monitoring considerations- arterial line, transesophageal echocardiogram, CVP, foley catheter
Fluid replacement for perioperative AKI treatment includes
500-1L bolus for hourly UO below acceptable levels
colloids may not be superior to crystalloids
high risk patients 0.5-1.0 mL/kg/hr
AKI perioperative treatment includes
fluid replacement
improve cardiac output
normalize SVR
diuretic use to prevent oliguria is not recommended
Early treatment of prerenal causes has
best outcomes
Postrenal has good prognosis with
early identification
The most difficult AKI type to treat is
intrarenal
Most common cause of AKI is
prolonged hypoperfusion
_______ reduces mortality in AKI more than dialysis
prophylaxis
Duration & magnitude of initial insult determine
severity of AKI
Key strategy for perioperative management of AKI is to
limit magnitude & duration of renal ischemia
Treatment for AKI inclues
administering volume (NS) to euvolemia
improving CO by afterload reduction
normalizing SVR
Renal function decreases
10% per decade
CKD is present when
GFR is less than 60 mL/min/1.73 m2 for three months
Signs & abnormal labs do not appear until
less than 40% of normal functioning of nephrons remain
When 95% loss of renal function occurs, symptoms include
uremia, volume overload, CHF
The respiratory effects of CKD includes
respiratory depression secondary to delayed clearance
The neurologic effects of CKD include
fatigue & weakness are early complaints
autonomic neuropathy–> b/c electrolytes mess w/ nerve functioning–> causes airway & aspiration risk
disequilibrium syndrome- severe neurologic effects
The cardiovascular effects of CKD include
hypertension & CHF- 90%volume dependent; 10% secondary to increased renin; pericardial effusion
pericarditis seen in patients with severe anemia
ischemic heart disease is most common cause of death- outcomes better in CABG with angioplasty
Gastrointestinal effects of CKD include
dialysis patients are at greater risk for GI bleeding
Hematologic effects of CKD include
normochromic, normocytic anemia- decrease in erythropoietin production, reduction in erythrocyte life secondary to dialysis, blood loss from frequent sampling
prolonged bleeding- decrease in platelet function, dialysis within 24 hours will correct, desmopressin increases levels of Factor VIII
Infectious effects of CKD include
protein malnutrition
neutrophil, monocyte, & macrophage changes
Endocrine effects of CKD include
hyperparathyroidism
adrenal insufficiency
The leading cause of death in dialysis patients is
infection
Describe electrolyte effects of CKD
sodium wasting
hypocalcemia
hyperkalemia
Hyperkalemia is a
serious disturbance in patients with renal disease
-fatal dysrhythmias or cardiac standstill can occur when K+ levels reach 7-8 mEq/L
Treatment of hyperkalemia includes
25-50 g dextrose 10-20 unites of insulin 50-100 mEq of sodium bicarb calcium chloride albuterol
Preoperative lab levels of potassium should be
checked even if dialysis is performed within 6-8 hours of surgery
Physiologic effects of dialysis include:
hypotension, muscle cramping, anemia, & nutritional depletion
EKG changes for the patient with hyperkalemia include
peaked T waves
progresses to widen QRS, peaked T waves
sinusoidal waves next- very bad
Preoperative anesthetic considerations for the CKD patient includes
pertinent lab & diagnostic tests
continue antihypertensive medications
Intraoperative anesthetic considerations for the CKD patient includes
monitoring, regional anesthesia, general anesthesia, fluid management
Postoperative anesthetic considerations for the CKD patient includes
dialysis within 24 hours
In anuric patients, it is contraindicated to give
potassium containing solutions (LR)
Blood products are reserved for
patients who need increased oxygen-carrying capacity
Fluid management for the prevention of AKI includes
UO 0.5-1.0 mL/kg/hr recommended
mildly compromised function- balanced salt solution at 3-5 mL/kg/hr. with 500 mL bolus as needed
Intraoperative monitoring is based on
patient’s physiologic status & surgical procedure & includes ECG, pulse oximetry, arterial catheter, & echo
Pharmacologic considerations for the patient on dialysis include
morphine is not removed by dialysis
meperidine cannot be removed by dialysis
H2 blockers are highly dependent on renal excretion
hydromorphone has active metabolite that can accumulate
Describe fluid management for the dialysis patient
insensible losses- replace with 5-10 mL/kg of D5W
if urine is produced- replace with 0.45% saline
Fluid management for the renal insufficiency/ESRD patient icnldues
replace volume deficit preoperatively
intraoperative losses greater than 15% should be replaced with colloid 1:1
crystalloid without potassium at 2-3 mL/kg/hr
The most reliable test for renal function is
creatinine clearance
Normal creatinine clearance is
95-150 mL/min.
Creatinine clearance measures
glomerular ability to excrete creatinine in urine
mild dysfunction 50-80 mL/min.
moderate dysfunction <25 mL/min
<10 mL/min requires dialysis
Blood urea nitrogen is
10-20 mg/dL
BUN: creatinine ratio is 10:1
Serum creatinine normal is
0.7-1.5 mg/Dl
for every 50% reduction in GFR, serum creatinine doubles
Regional anesthesia for patients with kidney disease is
generally well tolerated
Major concerns for regional anesthesia for the patient with kidney disease include
intolerance, coagulopathy, peripheral neuropathy, risk of infection
Block duration is _____ by renal failure
not affected
Spinal & epidural considerations for the patient with renal failure includes
platelet count, PT/PTT, ASRA coags
In general anesthesia for the renal failure patient, IV drugs are affected by
volume of distribution is increased
decreased protein binding
low pH
renal excretion
Describe the effects of renal failure on ketamine, benzodiazepines, propofol, dexmedetomidine, & remifentanil.
ketamine & benzodiazepines are less protein bound
propofol appears to be safe
dexmedetomidine cleared by liver
remifentanil- reduced clearance in patients with ESRD
fentanyl has prolonged half-life
Patients with ESRD generally require dialysis
24-36 hours after major surgery
Uremic patients may require fluid replacement with
red blood cells
FFP
colloid solutions
In patients with renal insufficiency, give
preoperative volume replacement
Describe the use of succinylcholine in renal failure patients.
increases serum potassium 0.5 mEq/L
succinylmonocholine (precursor to products of metabolism)
cholinesterase deficiency in uremic patients
Describe the use of pancuronium in renal failure.
80% excreted in urine
Describe the use of atricurium, cisatricurium, and mivacurium in renal failure patients.
duration not increased in renal failure
slower onset with cisatricurium and mivacurium
Describe the use of vecuronium in renal failure patients.
approximately 30% excreted via renal system
effects rapidly reversed with dialysis
Describe the use of rocuronium in renal failure patients
renal failure reduces clearance by almost 40%
& has longer DOA
