Renal anesthetic considerations
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What is the primary concern with kidney perfusion in relation to medication metabolism?

  • Medications are exclusively metabolized by the kidney.
  • Renal perfusion has no effect on medication excretion.
  • All medications are affected equally by renal perfusion.
  • Impairment can prolong the duration of action of medications and increase toxicity. (correct)
  • In the context of afterload and systemic vascular resistance (SVR), which statements are true?

  • Afterload is the left ventricular internal fiber load during systole (correct)
  • SVR reflects the peripheral vasomotor tone (correct)
  • Afterload and SVR are interchangeable terms in healthy patients. (correct)
  • Afterload can be elevated in certain conditions without affecting SVR (e.g. aortic cross clamp) (correct)
  • Which of the following is a characteristic of chronic renal failure?

  • Renal insufficiency occurs when there are 10% functioning nephrons.
  • Patients with chronic renal failure typically show symptoms at 60% nephron loss.
  • 50% of functioning nephrons are required for normal kidney function.
  • Anemia and coagulopathy are key features in chronic renal failure. (correct)
  • Which conditions are common risk factors associated with acute renal failure (ARF)?

    <p>Prolonged renal hypoperfusion due to hypovolemia.</p> Signup and view all the answers

    What method can be employed to prevent acute renal failure during high-risk surgeries?

    <p>Diuretics and renal dose dopamine.</p> Signup and view all the answers

    What is the primary function of erythropoietin produced by the interstitial kidneys?

    <p>Stimulates red blood cell production</p> Signup and view all the answers

    Which hormone is secreted by the adrenal glands to promote sodium and water reabsorption in the kidneys, thus increasing BP?

    <p>Aldosterone</p> Signup and view all the answers

    What happens to renal blood flow during mild-moderate stress?

    <p>Decreases and efferent arterioles constrict to maintain GFR</p> Signup and view all the answers

    Which of the following statements about renal blood flow (RBF) and glomerular filtration rate (GFR) is accurate?

    <p>RBF and GFR remain constant between 60-150 mmHg</p> Signup and view all the answers

    Which of the following best describes the role of the macula densa (kidney cells located nephron) in kidney function?

    <p>Inhibits aldosterone secretion when sodium is reabsorbed sufficiently</p> Signup and view all the answers

    What is a common outcome of oliguria in patients with renal perfusion issues?

    <p>Decreased nitrogenous waste excretion</p> Signup and view all the answers

    What are the paired organs located in the retroperitoneal cavity?

    <p>Kidneys</p> Signup and view all the answers

    In addition to filtering blood, which of the following is a key function of the kidneys?

    <p>Production of hormones for blood pressure regulation</p> Signup and view all the answers

    What is a potential consequence of fluid overload in renal patients?

    <p>Pulmonary edema and CHF</p> Signup and view all the answers

    Which electrolyte imbalances are commonly observed in renal patients?

    <p>Hyperkalemia</p> Signup and view all the answers

    What treatments are appropriate for hyperkalemia when potassium levels exceed 6.5 mEq/L?

    <p>Hyperventilation to reduce H+</p> Signup and view all the answers

    Which fluid should be avoided in renal patients due to its potassium content?

    <p>Lactated Ringer's (LR)</p> Signup and view all the answers

    What is a common sign of hypocalcemia?

    <p>Muscle cramping</p> Signup and view all the answers

    Which electrolyte is crucial for stabilizing the resting membrane potential (RMP)?

    <p>Potassium</p> Signup and view all the answers

    What leads to decreased production of erythropoietin (EPO) in renal patients?

    <p>A buildup of uremic toxins impairs the kidney's abilities to synthesize EPO</p> Signup and view all the answers

    What percentage of cardiac output do the kidneys receive?

    <p>20-25%</p> Signup and view all the answers

    What is the impact of renal perfusion in a steep Trendelenburg position?

    <p>Decreased renal perfusion due to increased abdominal pressure and effects of gravity</p> Signup and view all the answers

    Which electrolytes do the kidneys play a role in regulating? (Select all that apply)

    <p>Calcium</p> Signup and view all the answers

    Which electrolytes are antagonists of each other? (select 2)

    <p>Calcium and Magnesium</p> Signup and view all the answers

    Match the steps of the Renin-Angiotensin-Aldosterone System (RAAS):

    <p>1 Renin release by the kidneys = Stimulated by low blood pressure 2 Angiotensinogen activation by the liver = Converted by renin to angiotensin I 3 Angiotensin II formation by the lungs = Converted from angiotensin I by ACE 4 Aldosterone secretion by the adrenal glands = Promotes sodium and water retention in kidneys</p> Signup and view all the answers

    Where is the primary site of action for ACE inhibitors (ACEIs)?

    <p>Lungs</p> Signup and view all the answers

    Where is the primary site of action of Angiotensin Receptor Blockers (ARBs)?

    <p>Blood vessels</p> Signup and view all the answers

    What response does angiotensin II stimulate?

    <p>Vasoconstriction</p> Signup and view all the answers

    What are the three main end results of adrenal gland secretion?

    <p>All of the above</p> Signup and view all the answers

    What urine output is defined as oliguria?

    <p>Less than 0.5 mL/kg/hr</p> Signup and view all the answers

    What provides parasympathetic input to the kidneys?

    <p>Vagus nerve</p> Signup and view all the answers

    What is the baseline sympathetic tone of the kidneys in a non-stressed state?

    <p>Little to none</p> Signup and view all the answers

    What is the impact of high doses of epinephrine and norepinephrine on the kidneys?

    <p>Decreased renal blood flow (RBF) and glomerular filtration rate (GFR)</p> Signup and view all the answers

    Which of the following are prerenal cause of acute kidney injury?

    <p>Volume depletion</p> Signup and view all the answers

    What is a classic example of postrenal acute kidney injury (AKI)?

    <p>Ureteral obstruction</p> Signup and view all the answers

    What substances in urine indicate kidney dysfunction? (Select all that apply)

    <p>Glucose</p> Signup and view all the answers

    Why do high-risk surgeries (e.g., cardiopulmonary bypass and aortic surgery) increase the risk of acute renal failure?

    <p>Reduced blood flow to the kidneys</p> Signup and view all the answers

    Why is nitroglycerin used to prevent renal failure?

    <p>It increases renal blood flow by dilating the renal arteries and other capacitance vessels</p> Signup and view all the answers

    Which of the following is considered an intrarenal cause of acute kidney injury (AKI)? (select 2)

    <p>Acute tubular necrosis</p> Signup and view all the answers

    What percentage of functioning nephrons would a patient with Chronic Kidney Disease (CKD) typically have to be asymptomatic?

    <p>60%</p> Signup and view all the answers

    Those with renal insufficiency have ___ functioning nephrons. (Choose the correct percentage.)

    <p>15-40%</p> Signup and view all the answers

    Chronic renal failure characteristics = CAFÉ coagulopathy, anemia, fluids, electrolytes

    <p>True</p> Signup and view all the answers

    Which clotting factors are disrupted by metabolic acidosis?

    <p>III and VIII</p> Signup and view all the answers

    Why is lactated Ringer's solution contraindicated in renal patients?

    <p>It contains potassium, which can lead to hyperkalemia.</p> Signup and view all the answers

    Which of the following describes the coagulopathy seen in chronic kidney disease (CKD)?

    <p>Thrombocytopenia and impaired platelet function</p> Signup and view all the answers

    How is acidosis related to hyperkalemia?

    <p>Acidosis can cause potassium to shift from inside cells to the ECF/bloodstream.</p> Signup and view all the answers

    Which of the following are risk factors for hypermagnesemia? (Select all that apply)

    <p>Antacid use</p> Signup and view all the answers

    Why does hypocalcemia occur in chronic kidney disease (CKD)?

    <p>Decreased renal conversion of vitamin D to its active form resulting in decreased intestinal absorption of calcium</p> Signup and view all the answers

    Which electrolyte acts as a clotting factor?

    <p>Calcium</p> Signup and view all the answers

    Impaired ability to secrete phosphate leads to the secretion of _____ to increase calcium levels and decrease phosphate levels

    <p>Parathyroid hormone (PTH)</p> Signup and view all the answers

    How does parathyroid hormone (PTH) increase calcium levels in the blood?

    <p>All of the above</p> Signup and view all the answers

    Why does stridorous breathing occur in hypocalcemia?

    <p>Due to prolonged contraction of respiratory and laryngeal muscles</p> Signup and view all the answers

    What are the gastrointestinal symptoms of hypocalcemia? (Select all that apply)

    <p>Hypersecretion of gastric acid (peptic ulcers)</p> Signup and view all the answers

    What is Chvostek's sign?

    <p>A neurological sign indicating hypocalcemia, observed by tapping the facial nerve.</p> Signup and view all the answers

    What is Trousseau's sign?

    <p>A spasm of the hand brought on by inflating a blood pressure cuff indicative of hypocalcemia</p> Signup and view all the answers

    What is the mechanism by which (desmopressin) DDAVP is used to treat coagulopathies?

    <p>Stimulates the release of von Willebrand factor</p> Signup and view all the answers

    What is the effect of chronic kidney disease (CKD) on the usage of local anesthetics?

    <p>Decreased safe dosage for local anesthetics</p> Signup and view all the answers

    How do chronic kidney disease (CKD) patients respond to induction?

    <p>They appear hypovolemic due to impairment of the sympathetic nervous system activity that impairs compensatory vasoconstriction.</p> Signup and view all the answers

    Why is vasopressin considered beneficial for patients with chronic kidney disease (CKD)? )(select 2)

    <p>It increases water reabsorption (antidiuretic) in the kidneys.</p> Signup and view all the answers

    Defasculating dose of NDNMB does not slow or decrease the response of hyperkalemia secondary to succinylcholine administration

    <p>True</p> Signup and view all the answers

    Succinylcholine can raise K+ from 0.5-1 mEq/L

    <p>True</p> Signup and view all the answers

    What is unique about the volume of distribution in renal impairment, especially for water-soluble drugs?

    <p>Increased extracellular fluid results in increased volume of distribution, especially in water soluble drugs</p> Signup and view all the answers

    What effect do volatile inhalation agents have on the kidneys? (select 2)

    <p>Decrease renal blood flow in a dose-dependent manner</p> Signup and view all the answers

    What is a characteristic of induction and emergence in renal impairment?

    <p>Quicker induction and emergence due to anemia causing decreased blood gas coefficient</p> Signup and view all the answers

    What are the preferred volatile agents for a patient with renal impairment? (Select all that apply)

    <p>Isoflurane</p> Signup and view all the answers

    What effect do NSAIDs have on renal perfusion?

    <p>They decrease renal perfusion by impairing intrinsic renal vasodilation via prostaglandins</p> Signup and view all the answers

    Which of the following medications should be avoided in renal insufficiency due to active metabolites? (select 2)

    <p>Morphine</p> Signup and view all the answers

    What is the expected outcome of a drug that has an active metabolite?

    <p>Prolonged duration of effects</p> Signup and view all the answers

    What can occur in anephric patients during general anesthesia with neuromuscular blockade? (Select one)

    <p>Prolonged duration of neuromuscular block</p> Signup and view all the answers

    What does the lower urinary tract consist of?

    <p>Bladder and Urethra</p> Signup and view all the answers

    What does the upper urinary tract consist of?

    <p>Kidneys and ureters</p> Signup and view all the answers

    What is the purpose of a cystoscopy and ureteroscopy?

    <p>To diagnose and treat lesions of both the lower and upper urinary tracts</p> Signup and view all the answers

    What spinal levels need to be blocked to perform regional anesthesia for cystoscopy or ureteroscopy?

    <p>T6 for upper tract and T10 for lower tract</p> Signup and view all the answers

    What is the purpose of a TURP (transurethral resection of the prostate)?

    <p>To treat urinary obstruction due to BPH</p> Signup and view all the answers

    What factors affect irrigant absorption during TURP? (Select all that apply)

    <p>Irrigant hydrostatic pressure</p> Signup and view all the answers

    What area needs to be blocked when using regional anesthesia in the management of TURP?

    <p>T10</p> Signup and view all the answers

    In using general anesthesia during TURP, which of the following are characteristics? (Select two)

    <p>Positive pressure ventilation decreases irrigant absorption</p> Signup and view all the answers

    What is TURP syndrome?

    <p>A collection of neurologic and cardiovascular signs and symptoms caused by excessive irrigant absorption</p> Signup and view all the answers

    What are potential complications of TURP (transurethral resection of the prostate) surgery? (Select all that apply)

    <p>Bladder perforation</p> Signup and view all the answers

    What is a cause of delayed onset of TURP syndrome?

    <p>Absorption of irrigant from retroperitoneal and perivesicular spaces</p> Signup and view all the answers

    What complications are associated with peritoneal dialysis? (Select all that apply)

    <p>Infection</p> Signup and view all the answers

    What is the difference between an AV fistula and an AV graft? (select 2)

    <p>An AV fistula is created by connecting an artery directly to a vein, while an AV graft is created using a synthetic tube to connect an artery to a vein</p> Signup and view all the answers

    Who is a good candidate for a hemodialysis graft?

    <p>Patients who are failing fistulas or grafts or are catheter-dependent due to the blockage of veins leading to the heart</p> Signup and view all the answers

    Symptoms from TURP syndrome are usually a result of which of the following?

    <p>All of the above</p> Signup and view all the answers

    Which of the following are functions of the kidney? (Select all that apply)

    <p>Filter blood</p> Signup and view all the answers

    In the absence of renal disease, which factors are related to low renal perfusion and reduced GFR? select 3

    <p>Hypovolemia</p> Signup and view all the answers

    What type of cells contain renin?

    <p>Juxtaglomerular granular cells</p> Signup and view all the answers

    What is associated with high creatinine levels (>6 mg/dL)? select 2

    <p>Increased bleeding times</p> Signup and view all the answers

    What should be used to replace blood loss in patients with renal disease?

    <p>Red Blood Cells (RBCs)</p> Signup and view all the answers

    Under what circumstances should hyperkalemia be treated? select 2

    <p>Only when there are EKG changes</p> Signup and view all the answers

    What are the characteristic electrolyte abnormalities in renal disease? (Select all that apply)

    <p>Hyperkalemia</p> Signup and view all the answers

    What EKG changes are indicative of hyperkalemia? (Select all that apply)

    <p>Peaked T waves</p> Signup and view all the answers

    Which electrolyte abnormality is associated with a prolonged QT interval?

    <p>Hypocalcemia</p> Signup and view all the answers

    When should hemodialysis occur to optimize a patient for surgery?

    <p>Within 24 hours of surgery</p> Signup and view all the answers

    What is the preferred muscle relaxant due to its non-renal excretion (Hoffman elimination)? select 2

    <p>Cisatracurium</p> Signup and view all the answers

    What is the hilum in the kidney?

    <p>The area where blood vessels and nerves enter and exit the kidney</p> Signup and view all the answers

    What is the functional unit of the kidney?

    <p>Nephron</p> Signup and view all the answers

    Which of the following is true regarding urine output?

    <p>Urine output is directly proportional to MAP when MAP is greater than 50.</p> Signup and view all the answers

    How does the juxtaglomerular apparatus regulate renal blood flow (RBF) and glomerular filtration rate (GFR)?

    <p>By acting as a sensor located between the afferent and efferent arterioles</p> Signup and view all the answers

    How does mild constriction of the efferent arteriole lead to an increase in GFR?

    <p>It decreases renal blood flow, increasing intraglomerular hydrostatic pressure.</p> Signup and view all the answers

    Hypovolemia, hyponatremia, and B1 stimulation stimulate kidneys to secrete RENIN. RENIN + ANGIOTENSINOGEN from the liver, produces what substance?

    <p>Angiotensin 1</p> Signup and view all the answers

    What enzyme converts angiotensin I to angiotensin II?

    <p>Angiotensin-converting enzyme (ACE)</p> Signup and view all the answers

    Which of the following conditions can increase renin release? (Select all that apply)

    <p>Decreased renal perfusion pressure</p> Signup and view all the answers

    What factors stimulate aldosterone release? Select all that apply

    <p>RAAS stimulation</p> Signup and view all the answers

    Absorption of a large volume of _____ irrigation solution can produce TURP syndrome.

    <p>Hypo-osmolar</p> Signup and view all the answers

    What are the classic signs and symptoms of TURP syndrome? (Select all that apply)

    <p>HTN</p> Signup and view all the answers

    What is the site of action for aldosterone? select 2

    <p>Distal convoluted tubule</p> Signup and view all the answers

    Study Notes

    Kidney Anatomy and Function

    • Kidneys are paired organs located in the retroperitoneal cavity.
    • Each kidney contains approximately 1 million nephrons.
    • The hilum is the region where nerves and arteries enter and exit the kidney.
    • The kidneys receive 20-25% of cardiac output.
    • Renal blood flow (RBF) and glomerular filtration rate (GFR) are autoregulated, remaining constant between 60-150 mmHg.
    • Kidney position is influenced by body positioning, which can impact blood pressure measurements.

    Kidney Functions

    • Blood Filtration: The kidneys filter blood, removing waste products.
    • Fluid and Electrolyte Balance: They maintain sodium and water balance, crucial for electrolyte homeostasis, particularly for calcium and phosphorus.
    • Bone Metabolism: The kidneys play a role in bone metabolism.
    • Erythropoiesis: The kidneys produce erythropoietin (EPO), which stimulates red blood cell (RBC) production. RBCs transport oxygen via hemoglobin.
    • Blood Pressure Regulation: The kidneys regulate systemic blood pressure through the renin-angiotensin-aldosterone system (RAAS).
      • Renin, secreted by the kidneys, initiates the RAAS cascade.
      • Angiotensin II, a potent vasoconstrictor, is produced through this cascade, leading to increased blood pressure.
      • Angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) are used to manage blood pressure by interfering with the RAAS system.
      • Aldosterone, secreted by the adrenal glands, causes the kidneys to reabsorb sodium and water, elevating blood pressure.

    Urine Output

    • Normal daily urine output is 400-500 mL.
    • Desired urine output is 1 mL/kg/hr.
    • Oliguria is defined as less than 0.5 mL/kg/hr.
    • Decreased GFR in the absence of renal disease is often due to hypovolemia and renal vasoconstriction.

    Kidney Innervation

    • The kidneys are innervated by the autonomic nervous system.
    • Parasympathetic (PSNS) input comes from the vagus nerve.
    • Sympathetic (SNS) activity regulates various kidney functions, including nephron activity, vascular tone, and juxtaglomerular granular cell activity.

    Sympathetic Tone of Kidneys

    • The kidneys have minimal sympathetic tone in non-stressed states.
    • Mild to moderate stress causes a decrease in RBF, with efferent arterioles constricting to maintain GFR.
    • Severe stress, including hypovolemia, hypoxia, hypercarbia, and trauma, can significantly reduce RBF and GFR.

    Kidney Perfusion and Medications

    • Many medications are metabolized by the liver and excreted by the kidneys.
    • Impaired kidney function can affect both active metabolites and overall excretion of medications, potentially prolonging their action.

    Afterload vs Systemic Vascular Resistance (SVR)

    • In healthy patients, afterload and SVR are similar.
    • In situations like temporary aortic clamping, afterload can increase without affecting SVR.

    Acute Renal Failure (ARF)

    • ARF involves a significant decrease in GFR over 2 weeks or less.
    • Its incidence in aortic surgery is approximately 8%.
    • Supraceliac and suprarenal clamps, located above the kidneys, are associated with a higher risk of ARF.
    • Cardiopulmonary bypass reduces RBF by about 30%.
    • Infrarenal AKI results in the least amount of change.

    Prevention of ARF

    • Strategies to prevent ARF include diuretics, renal dose dopamine, and nitroglycerin administration.

    Risk Factors for ARF

    • Pre-existing renal disease
    • Congestive heart failure (CHF)
    • Advanced age
    • Prolonged renal hypoperfusion (e.g., hypovolemia, hypotension)
    • High-risk surgery (e.g., abdominal aneurysm, cardiopulmonary bypass)
    • Extensive burns
    • Sepsis
    • Jaundice

    Chronic Renal Failure (CRF)

    • CRF involves a progressive reduction in the number of functioning nephrons.
    • Patients with 60% of nephrons functioning are typically asymptomatic.
    • Renal insufficiency occurs when 15-40% of nephrons are functional.
    • Renal failure is defined as less than 15% of nephrons functioning.

    Characteristics of CRF: "CAFÉ"

    • "CAFÉ" represents key characteristics of CRF:
      • Coagulopathy:
        • Thrombocytopenia (low platelet count)
        • Impaired platelet function
        • Metabolic acidosis affects coagulation factors III and VIII.
        • Assess bleeding time with creatinine levels over 6 mg/dL.
        • Hemodialysis can reverse bleeding time abnormalities.
      • Anemia:
        • Decreased EPO production due to elevated urea levels.
        • Reduced RBC half-life by 50%.
        • Hemoglobin levels usually around 6-7 g/dL.
      • Fluids:
        • Fluid overload can lead to pulmonary edema and CHF.
        • Strict fluid control is vital.
        • Blood loss should be replaced with blood in a 1:1 ratio.
        • Lactated Ringer's solution (LR) should be avoided due to its potassium content.
        • Isotonic saline (NS) or D5W are preferred fluid choices.
      • Electrolytes:
        • Renal patients struggle to regulate electrolytes.
        • Commonly observed are hyperkalemia, hypermagnesemia, and hypocalcemia.
        • Potassium levels control resting membrane potential (RMP) across cell membranes.
          • Hyperkalemia can cause ECG changes, including peaked T waves, prolonged PR, wide QRS, heart block, and ventricular fibrillation.
          • Treatment for hyperkalemia (K+ levels > 6.5 mEq/L) includes:
            • Ventilation (hyperventilation reduces H+)
            • Albuterol (beta-2-adrenergic receptor stimulation)
            • Insulin/dextrose
            • Bicarbonate
            • Dialysis
        • Magnesium plays a role in muscle/nerve function, protein synthesis, and stabilizing RMP.
          • Hypermagnesemia can cause hypotension.
        • Calcium:
          • Impaired kidney activation of vitamin D reduces calcium absorption.
          • Hypocalcemia induces secondary hyperparathyroidism, increasing parathyroid hormone secretion.
          • Parathyroid hormone increases calcium by breaking down bone via osteoclasts.
          • Hypocalcemia signs include tetany, paresthesias, prolonged QT interval, muscle cramping, stridor, GI issues (anorexia, ileus, hypersecretion, delayed emptying), and asterixis.
            • Chvostek's sign (cheek twitching with tapping) and Trousseau's sign (carpal spasm with prolonged BP cuff inflation) are associated with hypocalcemia.
          • Autonomic and peripheral neuropathies are common.

    Dry Weight

    • Dry weight is the weight of a person's body without excess fluid. This term is particularly important in managing fluid status in patients with chronic renal failure.

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