Anesthesia and Renal Failure

In renal failure, the induction dose of which of the following should be

decreased ?

• Propofol

• Ketamine

• Thiopental

• Etomidate

Induction Anesthetics

• Propofol: undergoes hepatic biotransformation into inactive metabolites; in renal failure duration of action is not affected

• Ketamine: hepatic metabolism and redistribution are responsible for termination of the anesthetic effects and <3% is excreted unchanged in the urine, so duration is not affected by renal failure

Induction Anesthetics

• Thiopental: 85% is protein bound and in the setting of uremia the free fraction is almost doubled, so the induction dose should be decreased

• Etomidate: 75% is protein bound so the free fraction increases in renal failure; however this increase is not clinically significant

In renal failure, the induction dose of which of the following should be

decreased ?

• Propofol

• Ketamine

• Thiopental

• Etomidate

Volatile Anesthetics

• Nitrous Oxide: elimination is through exhalation, so it is not affected by renal failure

Fluoride Induced Nephrotoxicity

• Metabolism of sevoflurane, isoflurane, methoxyflurane, enflurane and halothane results in production of fluoride ions

• Nephrotoxicity is a result of 2 factors: the peak fluoride concentration (with above 50 uM toxic threshold) and the area under the curve of serum fluoride concentration versus time

Fluoride Induced Nephrotoxicity

• Isoflurane: 20 MAC-hours of isoflurane could lead to serum flouride levels above 50uM, however no postoperative renal dysfunction was detected

• Sevoflurane: regularly 7% of patients who receive sevoflurane will have serum flouride levels above 50uM. Yet, no clinically significant renal dysfunction was detected

Fluoride Induced Nephrotoxicity

• Methoxyfluane and enflurane might cause renal dysfunction especially when associated with hypovolemia, shock and renal vasoconstriction

Sevoflurane and compound A

• Sevoflurane is degraded in basic carbon dioxide absorbents, such as Barium Hydroxide and Soda lime, into a vinyl ether called compound A

• Compound A was proven to be nephrotoxic when it reaches certain thershold levels that differ among different animal species

Sevoflurane and compound A

• Human studies have not associated sevoflurane with any detectable postop impairment of renal function

• Some clinicians recommemd that fresh gas flow rate be al least 2L/min to avoid release of compound A

The duration of action of which of the following is not affected by renal

failure?

• Succinylcholine

• Rocuronium

• Vecuronium

• Doxacurium

• Cisatracurium

Renal Failure and Succinylcholine

• Succinylcholine: its duration of action is not significantly prolonged, so its use is justified in rapid sequence induction

• Renal failure patients are more prone to hyperkalemia and succinylcholine results in an increase in serum potassium levels in normal subjects (0.5mEq/L). Therefore, serum potassium levels should be checked and normalized.

• Use of a continuous infusion is not recommended since its major metabolite succinylmonocholine is active and dependent on renal excretion

Intermediate acting Muscle Relaxants

• Vecuronium: has an active metabolite (3-desmethyl vecuronium) that accumulates in renal failure causing an intubating dose to last around 50% longer

• Rocuronium: pharmacokinetic studies on patients

with renal failure had conflicting results with respect to the duration of action

• Atracurium and cisatracurium metabolism is independent of renal and hepatic function, so they are recommended in renal failure

Laundanosine

• It is a breakdown product of Hofmann elimination (of atracurium and cisatracurium) that was found to cause seizures in experimental animals.

• However, intensive care patients with renal failure receiving prolonged infusions of atracurium did not have any seizures

Long acting muscle relaxant

• Doxacurium and pipecuronium have reduced plasma clearance and prolonged duration of action in renal failure patients

The duration of action of which of the following is not affected by renal

failure?

• Succinylcholine

• Rocuronium

• Vecuronium

• Doxacurium

• Cisatracurium

Which of the following opioids is safe in renal failure

• Meperidine

• Fentanil

• Sufentanil

• Morphine

• Remifentanil

Opioids and Renal Failure

• Morphine undergoes hepatic metabolism to morphine-3-glucuronide and morphine-6-glucuronide. These metabolites can accumulate in renal failure and result in narcosis and respiratory depression

• Merperidine is metabolised to normeperidine which might accumulate in renal failure patients and result in CNS toxicity (seizures).

Opioids and Renal Failure

• Fentanyl and alfentanyl are good choices in renal failure since their metabolites are inactive and the change in their free fraction is not clinically significant

• Sufentanil has an active metabolite that might accumulate in renal failure upon chronic use and result in prolonged narcosis

Opioids and Renal Failure

• Remifentanil clearance is not affected by renal failure

• It is metabolized to remifentanyl acid, which would accumulate in renal failure, but is 4,600 times less potent

• Thus, the clinical implications are limited

Which of the following opioids is safe in renal failure

• Meperidine

• Fentanil

• Sufentanil

• Morphine

• Remifentanil

TURP syndrome

• In around 1.5 % of TURPs excessive absorption of the irrigating solution may lead to several symptoms described as TURP syndrome

• Several irrigation solutions are available for use during TURP, such as glycine, sorbitol, mannitol and distilled water

TURP syndrome

• The signs and symptoms can be divided into those common to all irrigating solutions and those peculiar to certain solutions.

• Excessive absorption of any of the solutions might lead to fluid overload and hyponatremia

Common Signs and Symptoms

• Fluid overload might manifest as hypertension, bradycardia and pulmonary edema especially in congestive heart failure patients

• Hyponatremia (if Na<120mEq/L) could present with ECG changes such as widening of QRS complex, ST elevation, ventricular fibrillation and CNS changes from confusion and nausea to coma

Glycine Solutions

• Glycine is an inhibitory neurotransmitter in the cortex and retina

• Excessive absorption might lead to seizures and post-op blindness that resolves when glycine blood levels decrease

Other solutions

• Distilled water might lead to hemolysis and hyponatremia.

• Glucose solutions might cause hyperglycemia

• Sortibol solutions could lead to hyperglycemia and lactic acidosis

Prophylactic measures

• To decrease fluid absorption, it is recommended to:

1) Limit resection time to < 1 hour

2) Suspend the irrigating bag <30cm above the table at the beginning of the procedure and < 15cm at the final stages of resection

TURP Syndrome Treatment

• When symptoms and signs of TURP syndrome occur:

1. Stop using the irrigation solution

2. If pulmonary and cardiac symptoms are present, place the patient in reverse Trendelenberg position to alleviate symptoms by pooling blood in the lower extremities

3. Electrolyte analysis: Sent blood for electrolytes, creatinine, glucose and ABGs

HyponatremiaTreatment

• If patients are symptomatic and have serum [Na] < 120mEq/L, they should be corrected with hypertonic saline at a rate < 100ml/hr till they are asymptomatic or serum [Na] > 120mEq/L

• Then hyponatremia is managed with fluid restriction and loop diuretic (furosemide)

Thank You