Renal anesthetic considerations

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Questions and Answers

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)?

Prolonged renal hypoperfusion due to hypovolemia. Signup and view all the answers

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

Diuretics and renal dose dopamine. Signup and view all the answers

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

Stimulates red blood cell production 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?

Aldosterone Signup and view all the answers

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

Decreases and efferent arterioles constrict to maintain GFR Signup and view all the answers

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

RBF and GFR remain constant between 60-150 mmHg 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?

Inhibits aldosterone secretion when sodium is reabsorbed sufficiently Signup and view all the answers

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

Decreased nitrogenous waste excretion Signup and view all the answers

What are the paired organs located in the retroperitoneal cavity?

Kidneys Signup and view all the answers

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

Production of hormones for blood pressure regulation Signup and view all the answers

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

Pulmonary edema and CHF Signup and view all the answers

Which electrolyte imbalances are commonly observed in renal patients?

Hyperkalemia Signup and view all the answers

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

Hyperventilation to reduce H+ Signup and view all the answers

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

Lactated Ringer's (LR) Signup and view all the answers

What is a common sign of hypocalcemia?

Muscle cramping Signup and view all the answers

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

Potassium Signup and view all the answers

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

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

What percentage of cardiac output do the kidneys receive?

20-25% Signup and view all the answers

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

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

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

Calcium Signup and view all the answers

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

Calcium and Magnesium Signup and view all the answers

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

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 Signup and view all the answers

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

Lungs Signup and view all the answers

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

Blood vessels Signup and view all the answers

What response does angiotensin II stimulate?

Vasoconstriction Signup and view all the answers

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

All of the above Signup and view all the answers

What urine output is defined as oliguria?

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

What provides parasympathetic input to the kidneys?

Vagus nerve Signup and view all the answers

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

Little to none Signup and view all the answers

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

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

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

Volume depletion Signup and view all the answers

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

Ureteral obstruction Signup and view all the answers

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

Glucose 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?

Reduced blood flow to the kidneys Signup and view all the answers

Why is nitroglycerin used to prevent renal failure?

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

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

Acute tubular necrosis Signup and view all the answers

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

60% Signup and view all the answers

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

15-40% Signup and view all the answers

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

True Signup and view all the answers

Which clotting factors are disrupted by metabolic acidosis?

III and VIII Signup and view all the answers

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

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

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

Thrombocytopenia and impaired platelet function Signup and view all the answers

How is acidosis related to hyperkalemia?

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

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

Antacid use Signup and view all the answers

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

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

Which electrolyte acts as a clotting factor?

Calcium Signup and view all the answers

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

Parathyroid hormone (PTH) Signup and view all the answers

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

All of the above Signup and view all the answers

Why does stridorous breathing occur in hypocalcemia?

Due to prolonged contraction of respiratory and laryngeal muscles Signup and view all the answers

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

Hypersecretion of gastric acid (peptic ulcers) Signup and view all the answers

What is Chvostek's sign?

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

What is Trousseau's sign?

A sudden drop in BP after standing Signup and view all the answers

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

Stimulates the release of von Willebrand factor Signup and view all the answers

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

Decreased safe dosage for local anesthetics Signup and view all the answers

How do chronic kidney disease (CKD) patients respond to induction? A) They appear hypovolemic due to slowing of the sympathetic nervous system activity that impairs compensatory vasoconstriction. B) Their response is the same as healthy individuals. C) They show hypervolemic responses due to fluid retention. D) They exhibit an increased heart rate due to stress.

They appear hypovolemic due to slowing of the sympathetic nervous system activity that impairs compensatory vasoconstriction. Signup and view all the answers

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

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

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

True Signup and view all the answers

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

True Signup and view all the answers

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

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

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

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

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

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

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

Isoflurane Signup and view all the answers

What effect do NSAIDs have on renal perfusion?

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

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

Morphine Signup and view all the answers

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

Prolonged duration of effects Signup and view all the answers

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

Prolonged duration of neuromuscular block Signup and view all the answers

What does the lower urinary tract consist of?

Bladder and Urethra Signup and view all the answers

What does the upper urinary tract consist of?

Kidneys and ureters Signup and view all the answers

What is the purpose of a cystoscopy and ureteroscopy?

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

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

T6 for upper tract and T10 for lower tract Signup and view all the answers

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

To treat urinary obstruction due to BPH Signup and view all the answers

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

Irrigant hydrostatic pressure Signup and view all the answers

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

T10 Signup and view all the answers

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

Positive pressure ventilation decreases irrigant absorption Signup and view all the answers

What is TURP syndrome?

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

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

Bladder perforation Signup and view all the answers

What is a cause of delayed onset of TURP syndrome?

Absorption of irrigant from retroperitoneal and perivesicular spaces Signup and view all the answers

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

Infection Signup and view all the answers

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

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 Signup and view all the answers

Who is a good candidate for a hemodialysis graft?

Patients who are failing fistulas or grafts or are catheter-dependent due to the blockage of veins leading to the heart 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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Test your knowledge on kidney anatomy and their vital functions! This quiz covers topics such as blood filtration, electrolyte balance, and the kidneys' role in erythropoiesis. Gain a better understanding of these critical organs located in the retroperitoneal cavity.