SYSTEM AND ANESTHESIA FOR UROLOGIC SURGERY


Acute Renal Failure


•  ↑ of Cr by ≥0.5 mg/dL or ↑ of Cr by ≥20% over 2 wks



•  Prerenal


• Renal hypoperfusion resulting in ↓ GFR


• Causes


• Hypovolemia, ↓ cardiac output, liver failure, sepsis


• Renal vasoconstriction (ACE/COX inhibitors)


•  Intrinsic (renal)


• Damage to renal parenchyma


• Causes


• Acute tubular necrosis (ATN)—causes include ischemia & toxins (aminoglycosides, myoglobin, IV contrast)


• Acute interstitial nephritis (AIN)—usually caused by drugs (NSAIDs, b-lactams, sulfonamides, rifampin)


• Glomerulonephritis


• DIC


• TTP


•  Postrenal


• Outflow obstruction (must have bilateral obstruction, unilateral obstruction if only one kidney present, kinked Foley)


• Causes


• Nephrolithiasis, BPH, prostate cancer, neurogenic bladder



•  Treatment


• Treat underlying disorder


• Avoid nephrotoxic drugs


• Fenoldopam & low-dose dopamine (controversial) may help prevent or treat ARF by dilating renal arteries & ↑ RBF & GFR


•  Dialysis if indicated due to:


• Acidosis


• Electrolyte disturbances (hyperkalemia)


• Intoxication (methanol, ethylene glycol)


• Volume overload


• Uremia


Chronic Renal Failure


•  Either GFR <60 mL/min/1.73 m2 or evidence of kidney damage (abnormal urinalysis, imaging or histology) for ≥3 mos


•  Causes:


• Hypertension


• Diabetes mellitus


• Glomerulonephritis


• Polycystic kidney disease


• Renovascular disease



•  Treatment


• ACE inhibitors/ARBs may slow progression of diabetic renal disease


• Erythropoietin for anemia


• Dialysis as indicated (hemodialysis/peritoneal dialysis)


• Phosphate binders for hyperphosphatemia


• Renal transplantation



For a list of commonly used diuretics, see Chapter 2H-56, Clinical Characteristics of Commonly Encountered Diuretics


ANESTHESIA FOR PATIENTS WITH RENAL DISEASE


Effects of Anesthesia on Renal Function


•  Reversible ↓ in RBF, GFR, urine production during regional & general anesthesia can occur despite maintenance of normal BP/volume status


•  RBF & GFR will usually return to normal within several hours postop


Indirect Effects of Anesthesia


•  Anesthetic agents & sympathetic blockade (during regional techniques)


→ Hypotension & myocardial depression → ↓ RBF & GFR


•  Hydration before anesthesia may lessen hypotension and changes in RBF


Direct Effects of Anesthesia


•  Fluorinated agents can cause direct renal toxicity (fluoride impairs kidney’s ability to concentrate urine & causes tubular necrosis)


• Fluoride production negligible with halothane, desflurane, & isoflurane


• Sevoflurane & enflurane release fluoride (no clinical evidence of renal damage)


•  Sevoflurane reacts with carbon dioxide absorbents to form compound A (shown to cause renal damage in rat models)


• Low fresh gas flows should be avoided with sevoflurane (use flows of ≥1 L/min)


• Consider avoiding sevoflurane in pts with renal insufficiency (theoretical risk of nephrotoxicity)


•  Common IV agents do not cause changes in GFR


MEDICATIONS TO AVOID OR USE WITH CAUTION IN RENAL FAILURE


•  Lipid-insoluble, ionized drugs, & water-soluble metabolites of hepatically metabolized drugs are renally excreted & may accumulate in renal failure


•  Highly protein-bound drugs can accumulate if patient is hypoalbuminemic



UROLOGIC SURGERY


Cystoscopy/Ureteroscopy/TURBT


General Considerations


•  Indications: Need for biopsies, laser lithotripsy, extraction of stones, placement of ureteral stents


•  Pts commonly elderly with comorbid medical conditions


•  Irrigation fluids often used to improve visualization & for flushing


Sterile water: Hypotonic, causes hemolysis & hyponatremia when absorbed systemically; safe with electrocautery


Nonelectrolyte solutions (glycine, sorbitol, mannitol): Slightly hypotonic, can cause hyponatremia if absorbed in large volumes; safe with electrocautery


Electrolyte solutions (NS, LR): Isotonic, do not cause hemolysis when absorbed systemically; cannot be used with electrocautery


Anesthetic Technique


•  Positioning: Lithotomy


•  Usually GA, can use local/MAC/regional (T10 level necessary for instrumentation of lower GU tract), consider using LMA


•  Muscle relaxation not usually necessary (consider ETT with relaxation if surgeon anticipates working near obturator nerve)


•  Minimal to no postop pain; short-acting opioids (fentanyl) usually sufficient


Complications


•  Peroneal nerve injury from lithotomy position (causes foot drop)


•  Bladder perforation: Extraperitoneal perforation is more common; signs and symptoms include nausea, diaphoresis & inguinal, retropubic or lower abdominal pain


Transurethral Resection of the Prostate (TURP)


General Considerations


•  Indications: Relief of bladder obstruction from enlarged prostate (typically BPH)


•  Typically elderly pts with comorbid medical conditions


•  Opening of venous sinuses may lead to absorption of large amounts of irrigation fluid (see cystoscopy above) & can result in TURP syndrome (see below); fluid absorption dependent on duration of procedure, number of sinuses opened (related to prostate size), peripheral venous pressure, & height of irrigation fluid


Anesthetic Technique


•  Positioning: Lithotomy


•  General or regional (T10 level necessary)


• Base choice on pt’s preference, coexisting diseases


• Regional anesthesia allows for evaluation of TURP syndrome during procedure


•  Muscle relaxation not required, although patient movement should be avoided (prevent further bleeding/perforation of prostate)


•  Postop pain usually not significant


Complications


•  TURP syndrome


• Results from absorption of large volumes of irrigant fluid through venous sinuses of prostate


• → Hyponatremia & volume overload


• Signs/symptoms: Headache, confusion, nausea/vomiting, HTN, angina, seizures, coma, cardiovascular collapse


• May also see toxicity from absorption of irrigant solutes


• Glycine: Can cause transient blindness, seizures


• Ammonia: Can cause delayed awakening, encephalopathy


• Hyperglycinemia may result in CNS toxicity & circulatory collapse


• Treatment: Fluid restriction & diuretics to correct hyponatremia & volume overload; if pt has seizures/is comatose → consider hypertonic saline


•  Bladder perforation


•  Coagulopathy: Dilutional thrombocytopenia from excessive fluid absorption & DIC


•  Bacteremia: Since prostate is colonized by bacteria, bacteremia may result after instrumentation


•  Prophylactic antibiotics may ↓ risk of bacteremia/septicemia


Alternatives to TURP


•  Medical management with alpha blockers


•  Vaporization of prostate tissue with electrocautery/laser/thermocoagulation (avoid danger of TURP syndrome)


Urologic Laser Surgery


General Considerations


•  Indications: Condyloma acuminatum, ureteral strictures, BPH, ureteral calculi, & superficial carcinomas of penis, ureter, bladder, or renal pelvis


•  Different lasers may be used (CO2/argon/pulsed dye/Nd-YAG/KTP-532)


•  Safety concerns


• Goggles should be worn by OR personnel & patient to protect eyes from an inadvertent break in laser fiber


• Lasers should be used intermittently to prevent thermal injuries


• Special masks should be worn to prevent inhalation of active HPV particles when condyloma are being treated


Anesthetic Technique


•  Positioning: Lithotomy


•  Local with MAC, general, or regional anesthesia


Open Prostatectomy


General Considerations


•  Indications: Simple prostatectomy for BPH that cannot be resected transurethrally; radical prostatectomy for prostate cancer


•  Pts often elderly with comorbid medical conditions


•  Blood loss can be significant


•  Retroperitoneal lymph node dissection is performed for staging in prostate cancer


•  Bilateral orchiectomy may be performed in symptomatic, advanced disease.


Monitoring/Access


•  Standard monitors; large-bore IV


Anesthetic Technique


Open prostatectomy


•  Positioning: Supine


•  Anesthesia: Regional, general, or combined general/epidural


•  Epidural may ↓ blood loss, improve postop pain relief, & result in recovery of bowel function more quickly


•  Experienced surgeons typically able to perform procedure under general anesthesia with minimal blood loss/small incisions


•  Surgeon may ask for methylene blue/indigo carmine to assess integrity of urinary tract


• Indigo carmine: Can cause hypertension (α-agonism)


• Methylene blue: Can cause hypotension/interfere with SpO2 readings


Laparoscopic and robotic-assisted prostatectomy


•  Laparoscopy +/- robotic-assisted


•  Advantages: Less blood loss (vs. open), smaller incisions with less postop pain


•  Positioning: Lithotomy; steep Trandelenberg


•  Anesthesia: General endotracheal anesthesia


Cystectomy


General Considerations


•  Indications: Simple cystectomy for benign bladder disease (hemorrhagic/radiation cystitis); radical cystectomy for invasive bladder tumors


•  Pts often elderly with comorbid conditions; given the association between smoking & bladder cancer, pts may be at risk for CAD & COPD


•  After cystectomy, a urinary diversion must be constructed


• → Piece of ileum can be formed into an ileal conduit (brought out to the abdominal wall as a stoma)


• → Bladder suspension more involved operation (piece of bowel is formed into a pouch & connected to the urethra)


• Significant blood & fluid loss may occur


Monitoring/Access


•  Standard monitors; consider arterial line, central line given potential for large blood loss & fluid shifts; large bore IV


Anesthetic Technique


•  Positioning: Supine or lithotomy


•  General or combined general/epidural anesthesia


Nephrectomy


General Considerations


•  Indications: Neoplasm, transplantation, chronic hydronephrosis/infection, trauma


•  Pts undergoing nephrectomy for renal cell carcinoma, will undergo preop staging to determine if tumor involves IVC or right atrium


• Tumor may partially/completely obstruct IVC (reduces venous return & may cause hypotension); IVC may need to be clamped during resection


• Tumor may embolize to pulmonary vasculature (signs: ↓ SpO2, hypotension, supraventricular arrhythmias)


• Complications: Venous air embolus, diaphragmatic injury (causing pneumothorax)


•  May be performed open or laparoscopically


Monitoring/Access


•  Standard monitors; consider arterial line


•  Large-bore IV (potential for significant blood loss)


Anesthetic Technique


•  Positioning: Lateral decubitus position for retroperitoneal approach/supine for transabdominal approach


•  General anesthesia or combined general/epidural anesthesia (T7–T9 level)


•  Hydration to preserve renal blood flow


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Aug 28, 2016 | Posted by in ANESTHESIA | Comments Off on SYSTEM AND ANESTHESIA FOR UROLOGIC SURGERY

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