Urologic Flashcards
The kidneys receive ___% CO
20-25%
How do the kidneys maintain homeostasis?
Filtration
Reabsorption
Tubular excretion
Normal GFR
125mL/min
Up to 99% filtrate reabsorbed
Renal Hormones
Aldosterone ADH Angiotensin ANP Vitamin D Prostaglandins
Bowman’s Capsule
Filtration
Proximal Tubule
Reabsorption
Loop of Henle
Concentration
Distal Tubulue
Reabsorption
Collecting Duct
Last chance to concentrate urine & reabsorb H2O
Urine Specific Gravity
1.01 - 1.025
pH 4.6-4.9
Anesthesia Impact
Anesthetic drugs depress normal renal function
↓RBF 30-40%
Autoregulation impairment
↓GFR, urinary flow, & electrolyte secretion
Similar changes after spinal or epidural anesthesia
- Sympathetic blockade & ↓BP
Volatile Anesthetics Effect
Mild ↑renal vascular resistance
Compensatory mechanisms in response to ↓CO/SVR
Goal - preop hydration, ↓volatile agents, maintain BP, & attenuate ↓RBF/GFR
Sevoflurane
Associated w/ elevated fluoride levels
Degraded by absorbents → compound A (vinyl ether)
Compound A nephrotoxicity
↑FGF to prevent risk 1L/min 2 MAC-hours max
↓gas concentration
Utilize carbon dioxide absorbents
Isoflurane
Not associated w/ nephrotoxicity
Desflurane
Resists biodegradation
Not associated w/ nephrotoxicity
Fluoride Ion Toxicity
Fluoride interferes w/ Na+/Cl¯ active transport in the loop of Henle
Potent vasoconstrictor → negative effects on CV
Inhibit enzyme systems (ADH)
Nephrotoxicity - proximal tubular swelling & necrosis
Nephrotoxicity S/S
Polyuria Hypernatremia Serum hyperosmolality ↑BUN/creatinine ↓creatinine clearance Related to dosage, duration, & peak fluoride concentrations
Acute Kidney Injury
Renal functional or structural abnormality that occurs w/in 48hrs
↑creatinine 0.3mg/dL or 50%
UOP <0.5mL/kg/hr x 6 hours
Pre-Renal AKI
Renal hypoperfusion w/o parenchymal damage
- Hemorrhage, vomiting/diarrhea, diuretics, sepsis/shock, CHF, NE, NSAIDs, ACEi
Early identify & treatment causes = BEST outcomes
Intra-Renal AKI
Damage to renal tissue
- Tubular injury d/t hypoperfusion, myoglobin, chemotherapy, infections, lymphoma, toxemia (pregnancy), vasculitis
Most difficult to treat w/ worst oucomes
Post-Renal AKI
Due to urinary tract obstruction
- Renal calculi, peritoneal mass, prostate/bladder urethra tumor, fibrosis, hematoma, strictures
Good prognosis w/ early identification
AKI Risk Factors
Hypovolemia, electrolyte imbalance, contrast dye
Aging - preop renal dysfunction or >50yo
Comorbidities - cardiac or hepatic failure
Surgical procedures - aortic cross-clamp, cardiac bypass, arteriography, intra-aortic balloon pump
Emergency or high risk procedures - ruptured AAA, ischemic time, high volume blood transfusion
AKI Preop Tx
Replace intravascular fluid deficits
- Balanced salt solution minimizes ADH & renin-angiotensin-aldosterone release
- Attenuate surgical stress
A-line, TEE, CVP, foley catheter
AKI Periop Tx
*Fluid replacement Colloids vs. crystalloids Goal 0.5-1mL/kg/hr *Improve CO *Normalize SVR
Avoid diuretics to treat oliguria Prevention & management - Prevent prolonged hypotension - Prophylaxis - Initial insult duration & severity determines AKI
Admin volume NS to euvolemia
↓afterload ↑CO
Limited renal ischemia duration
Chronic Kidney Disease
Renal function ↓10% per decade
GFR < 60mL/min for 3 MONTHS
S/S & abnormal labs do not appear until <40% normal functioning nephrons remain
95% loss renal function → uremia, volume overload, CHF
CKD Systemic Effects
Cardiovascular
HTN & CHF
90% volume dependent
10% 2° ↑renin
Pericardial effusion
Ischemic heart disease = most common cause death
Outcomes better w/ CABG than angioplasty
Pericarditis in patients w/ severe anemia
CKD Systemic Effects
Respiratory
Respiratory depression 2° delayed clearance
CKD Systemic Effects
Neurologic
Fatigue & weakness - early complaints
Autonomic neuropathy
Disequilibrium syndrome → seizures, stupor, & coma
CKD Systemic Effects
Hematologic
Normochromic, normocytic anemia
↓erythropoietin production
↓erythrocyte life 2° dialysis
Blood loss from frequent sampling
Prolonged bleeding ↓clotting factors
↓platelet function
Dialysis w/in 24hrs corrects
Desmopressin ↑factor VIII levels
RBC transfusion citrate binds to Ca2+ → hypocalcemia
CKD Systemic Effects
Gastrointestinal
Dialysis patients ↑risk GI bleeding
Mucosal changes & inflammation
CKD Systemic Effects
Infection
Protein malnutrition
Neutrophil, monocyte, & macrophage changes
CKD Systemic Effects
Endocrine
Hyperparathyroidism (compensatory mechanism)
Adrenal insufficiency
CKD Systemic Effects
Electrolyte
Na+ wasting
Hypocalcemia
Hyperkalemia
Hyperkalemia
K+ 7-8mEq/L → fatal dysrhythmias Treatment: - 25-50g dextrose - 10-20 units regular insulin - 50-100mEq sodium bicarbonate - Hyperventilate ↓CO2 Check preop levels
CKD Anesthetic Considerations
Preop
Labs & diagnostic tests
Continue antihypertensive medications
Renal insufficiency - preop volume replacement
CKD Anesthetic Considerations
Periop
A-line
Regional vs. general anesthesia
Central line
Fluid management
CKD Anesthetic Considerations
Postop
Dialysis w/in 24-36hrs
CKD Anesthetic Considerations
Fluid Management
UOP 0.5-1mL/kg/hr
Treat mildly compromised function w/ balanced salt solution 3-5mL/kg/hr w/ 500mL bolus PRN
LR & other K+ containing solutions contraindicated when patient UOP <100mL/day
Reserve blood products for patients requiring ↑oxygen-carrying capacity
Renal insufficiency or ESRD
- Replace fluid volume deficit preop
- Intraop losses >15% EBL replace w/ 1:1 colloid
- Crystalloid w/o K+ 2-3mL/kg/hr
Dialysis patient
- Insensible losses replace w/ 5-10mL/kg D5W
- Replace urine produced w/ 0.45% saline
Dialysis Physiologic Effects
Hypotension
Muscle cramping
Anemia
Nutritional depletion
Serum Creatinine
0.7-1.5mg/dL
↓GFR 50% → serum creatinine doubles
BUN
Blood urea nitrogen
10-20mg/dL
BUN:creatinine ratio 10:1
Creatinine Clearance
MOST RELIABLE RENAL FUNCTION TEST 95-150mL/min Measure glomerular ability to excrete creatinine in urine Mild dysfunction 50-80mL/min Moderate <25mL/min <10mL/min requires dialysis
Pharmacologic Considerations
↓protein binding ↑sensitivity
Morphine not removed by dialysis
Meperidine metabolite Normeperidine not removed by dialysis
H2 blockers dependent on renal excretion ↓dose
Regional Anesthesia
Well-tolerated
Block DOA not impacted by renal failure
Spinal/epidural - obtain platelet count, PT/PTT, coags
Concerns include intolerance, coagulopathy, peripheral neuropathy, & infection risk
General Anesthesia Drugs
IV ↑Vd ↓protein binding Ketamine & benzos less protein bound Propofol = safe Dexmedetomidine hepatic clearance Remifentanil ↓plasma esterases ↓clearance ESRD patients
NMBs
Succinylcholine - ↑K+ 0.5mEq/L - Cholinesterase deficiency (uremic patients) Pancuronium - 80% renal excretion Atracurium/Cisatracurium/Mivacurium - DOA not impacted in renal failure Vecuronium - 30% renal excretion - Effects rapidly reversed w/ dialysis Rocuronium - Renal failure ↓clearance 40% → longer DOA
Cystoscopy
Any urologic procedure not open Cystoscope to examine urethra & bladder Diagnostic or treatment procedures Position = lithotomy Void prior to discharge home
Extracorporeal Shock Wave Lithotripsy
ESWL
Nephrolithiasis (renal calculi or kidney stones)
<5mm pass w/o intervention
5-10mm medical management
>10mm requires intervention
Non-invasive treatment that uses high-energy ultrasound waves to breakup calculi
- Outpatient procedure under GA
- R wave used to trigger shocks (EKG placement)
- Hematuria common
ESWL Contraindications
Active UTI
Uncorrected bleeding disorder or coagulopathy
Distal obstruction
Pregnancy
ESWL Complications
Dose-dependent hemorrhagic lesions
Perforation, rupture or damage to colon, hepatic structures, lungs, spleen, pancreas, abdominal aorta, or iliac veins
Hematuria develops in most patients
Diabetes, new-onset HTN, or ↓renal function
ESWL Anesthetic Considerations
GA rapid onset & able to control patient movement
Spinal/epidural level T4/T6
MAC
Topical LA
Discontinue ASA, anticoagulants, platelet inhibitors, & NSAIDs 7-10 days prior to procedure ↓hematuria risk
Document negative urine culture
HCG on appropriate patients
Laser eye protection
Percutaneous Nephrolithotomy
Procedure to remove kidney stones <25mm
GA & postop hospitalization (admit inpatient)
Prone or supine position
Percutaneous Nephrolithotomy
Complications
Pain, fever, UTI, renal colic, septicemia, bleeding, pneumothorax/hemothorax, anaphylaxis
TURP
Transurethral resection of prostate (BPH)
Most common surgical procedure performed in men >60yo
Scope placed through urethra to cut away obstructing prostate lobes
Bladder distended & continuous irrigation used
ANESTHETIC RISKS R/T PATIENT AGE & ASSOCIATED COMORBIDITIES
TURP Anesthetic Considerations
Commonly performed under GA Spinal anesthesia preferred to assess patient mental status S/S complications more easily detected PREVENTION most important approach - Avoid trendelenburg position - Limit resection <1 hour - Place irrigation solution <60c, above prostate - Monitor electrolytes - Regional technique w/ sedation
TURP Irrigation Solutions
Distilled water
1° Saline
Cytal (sorbitol & mannitol)
Glycine → toxicity
TURP Complications
Volume overload w/ pulmonary edema Dilutional hyponatremia w/ hypoosmolality → cerebral swelling ↑ICP Cardiac effects Renal toxicity (glycine) Hyperglycemia Hypothermia Glycine absorption Bleeding (difficult to assess d/t irrigation) Bladder perforation Infection Skin burns TURP syndrome
TURP Syndrome
Rare but significant complication
Mortality up to 25%
Fluid absorbed through prostate
TURP Syndrome S/S
Combination water intoxication, fluid overload, & hyponatremia
Water intoxication - confusion, restlessness, seizure, lethargy, coma, dilated sluggish pupils
Fluid overload - HTN, bradycardia, arrhythmia, angina, pulmonary edema, CHF, hypotension
Hyponatremia - CNS changes, widened QRS, T-wave inversion
Glycine toxicity - N/V, headache, transient blindness, myocardial depression
TURP fluid absorption dependent on _____
Resection size & duration
Irrigation solution pressure
Number venous sinuses open at once
Provider experience
TURP Fluid Absorption
30mL fluid absorbed per minute
Up to 8L in 2 hours
1L irrigant uptake ↓serum Na+ 5-8mEq/L
Serum Na+ <120mEq/L associated w/ severe reactions
Glycine Absorption
Glycine - amino acid
Acts as inhibitory transmitter
Excessive absorption → N/V, fixed & dilated pupils, headache, weakness, muscle incoordination, TURP blindness, seizures, hypotension
TURP Syndrome Treatment
Early recognition Notify surgeon to stop surgery Correct hyponatremia Furosemide 20mg IV Labs - electrolytes, glucose, Hct, creatinine, ABG, 12-lead EKG Midazolam 1mg PRN seizures Pulmonary edema → intubate PRBCs Investigate DIC or 1° fibrinolysis
Hyponatremia Correction
3-5% saline <100mL/hr
↑Na+ 0.5mEq/hour or 8mEq/day
Goal Na+ >120mEq/L
Rapid reversal → osmotic demyelination syndrome
Laparoscopic Urologic Surgery
Anesthetic Considerations
Pneumoperitoneum 15mmHg
Urologic system retroperitoneal (communicates w/ thorax) → risk subcutaneous emphysema
Alterations in renal & hepatic perfusion
CO2 absorption → potential acidosis
↑intraabdominal & intrathoracic pressures
Hemorrhage
Robotic Urologic Surgery
Upper tract - simple or radical nephrectomy, radical nephroureterectomy, nephron-sparing
Pelvic - radical cystectomy, radical prostatectomy
Robotic Urologic
Anesthetic Considerations
Steep trendelenburg Lithotomy (prostatectomy) Arms tucked at sides Airway assessment BEFORE extubation Duration 3-4 hours EBL <300mL Limit fluids until urethra reconnected 2L total Large bore PIVs & A-line DVT prophylaxis, eye protection, OG tube, Bair hugger, antibiotics, dexamethasone Remifentanil infusion common
Nephrectomy
Open vs. laparoscopic Lateral jack-knife position (kidney rest) Cardiovascular compromise 3rd spacing & edema Hemodynamic monitoring A-line Postop pain management
Renal Transplant
ESRD treatment
Donors living or deceased
Most frequent solid organ transplant today
5-year survival rate 70%
Transplanted kidney placed in R or L extraperitoneal fossa (R preferred)
Attached via vascular anastomoses external iliac artery & vein & ureter anastomosed to bladder
GA with A-line & CVP monitoring
Propofol & Cisatracurium
Immunosuppressant therapy
