Uremic Encephalopathy Dr. Abrar Ali Katpar Resident Nephrology King Khalid Hospital, Hail, K.S.A
Background
Uremia is final stage of progressive renal insufficiency & resultant multiorgan failure.
It results from accumulating metabolites of proteins & amino acids & concomitant failure of renal catabolic, metabolic, and endocrinologic processes.
No single metabolite has been identified as the sole cause of uremia.
Uremic encephalopathy (UE) is one of many manifestations of renal failure (RF).
Introduction
Uremic encephalopathy is an organic brain disorder.
Occurs due to build up of toxins which are normally cleared by kidneys.
It develops in pts with RF, usually when creatinine clearance levels fall & remain below 15 mL/min.
Manifestations vary from
Mild symptoms (eg, lassitude, fatigue) to
Severe symptoms (eg, seizures, coma).
Severity & progression depend on rate of decline in renal function.
Symptoms are usually worse in ARF.
Prompt identification of uremia as the cause of encephalopathy is essential because symptoms are readily reversible following initiation of dialysis.
Patho-physiology
It has a complex pathophysiology.
With unknown exact cause.
Endogenous guanidino compounds are neurotoxic.
Accumulating metabolites of proteins & amino acids affect the entire neuraxis.
Several organic substances accumulate
Urea,
Guanidine compounds,
Uric acid,
Hippuric acid,
Various amino acids,
Polypeptides,
Polyamines,
Phenols & conjugates of phenols,
Phenolic and indolic acids,
Acetoin,
Glucuronic acid,
Carnitine,
Myoinositol,
Sulfates,
Phosphates, and middle molecules.
In terminal renal failure
Increase levels in various regions of brain with uremia
Guanidinosuccinic acid & guanidine >100-fold
Methylguanidine >20-fold.
Creatinine >5-fold
Disturbance in kynurenic pathway occurs,
Tryptophan is converted to neuroactive kynurenines.
Elevation of kynurenine, 2 kynurenines, 3-hydroxykynurenine, with chronic renal insufficiency.
Leads to alterations in cellular metabolism cellular damage, and eventually cell death.
Kynurenine can induce convultions.
Study shows In rats brain with RF
Increased level
CP = Creatine Phosphate.
ATP = adinosine triphosphate
Glucose.
Decreased levels
ADP = Adinosine Diaphosphate
AMP = Adinosine Monophosphate
Lactate.
This suggest that uremic brain less uses ATP and produce less ADP and AMP and lactate then normal brain.
And is consistent of generalized decrease in metabolic brain function.
Transketolase
Transketolase is a thiamine-dependent enzyme of pentose phosphate pathway.
Found mainly in myelinated neurons.
it maintains axon-cylinder myelin sheaths.
Guanidinosuccinic acid can inhibit transketolase resulting demylination.
It also inhibit excitatory synaptic transmission in CA1 region of hippocampus, contributing to cognitive syndrome in UE.
Accumulation of diamethylarginine
It’s a NOS ( nitric oxide synthase) inhibitor.
Observed in uremic Pts leads to vasoconstriction.
Induces hypertension.
Increases ischemia & vulnerability to uremic brain.
Hormones
Increased levels.
PTH
Insulin
Growth hormone
Glucagon
Thyrotropin
Prolectin
Luteinizing hormone
Gastrin
PTH is thought to promote the entry of Ca into neurons specially in cerebral cortex, which leads to many changes observed.
Leads to distorted balance of excitatory & inhibitory effects, contributes to systemic changes in UE. These changes in CSF may be response of early phase of disorder. Alterations occur in metabolism of dopamine & serotonin in brain, which may lead to early symptoms eg, sensorial clouding.
Increased levels
Ca activity
Organic acids
Free tryptophan
Decrease levels
GABA (gamma-aminobutyric acid)
Glutamine
Glycin activity
As uremia progresses
accumulation of guanidino compounds results in
activation of excitatory N-methyl-D-aspartate (NMDA) receptors &
inhibition of inhibitory GABA receptors, which may cause myoclonus & seizures .
The encephalopathy correlates roughly with BUN level, urea itself is not thought to be causative.
Abnormalities may be associated with UE
Acidosis
Hyponatremia
Hyperkalemia
Hypocalcaemia
Hypermagnacemia
Over hydration
Dehydration.
Frequency
United States
CrCl level < 10% of normal probably develop some degree of encephalopathy.
In one pediatric study, encephalopathy occurred in 40%, with a BUN level > 90 mg/dL.
Mortality/Morbidity
Symptoms include :-
Somnolence & decreased mentation.
Asterixis usually present.
Symptoms are reversible following
Institution of dialysis
Renal transplantation .
The severe complications seizures coma leads to death.
Early recognition is crucial to prevent morbidity or mortality.
Race
No racial predilection exists.
Sex
No association
Age
Any age, mostly after 65 years as general.
Clinical
History
Symptoms begin insidiously
Not noticed by patients but by family members/caregivers.
In many cases, CNS impairment provides first indication of metabolic derangements.
Symptoms may progress slowly or rapidly.
Changes in sensorium include:-
Loss of memory,
Impaired concentration,
Depression,
Delusions,
Lethargy,
Irritability,
Fatigue,
Insomnia,
Psychosis,
Stupor,
Catatonia, &
Coma.
Patients may complain of:
Slurred speech,
Pruritus,
Muscle twitches, or
Restless legs.
History
Early symptoms
Anorexia
Nausea
Restlessness
Drowsiness
Diminished ability to concentrate
Slowed cognitive functions
More severe symptoms
Vomiting
Emotional volatility
Decreased cognitive function
Disorientation
Confusion
Bizarre behavior
History
As uremic encephalopathy progresses, patients may develop:-
Myoclonus,
Asterixis,
Seizures,
Stupor &
Coma.
Physical exam
Variable & depending on severity of encephalopathy.
Neurologic findings range from normal to a comatose state.
Altered mental status (confusion)
Cranial nerve signs (nystagmus)
Papilledema
Hyperreflexia, clonus, asterixis
Stupor
Coma occurs only if uremia remains untreated & progresses.
Findings
Include :
Myoclonic jerks, twitches, or fasciculations (ie, uremic twitch-convulsive syndrome postulated by Adams et al in 1997)
Asterixis
Dysarthria
Agitation
Tetany
Seizures, usually generalized tonic-clonic
DD
Encephalopathy, Hepatic
Hyperparathyroidism
Encephalopathy, Hypertensive
Hypoglycemia
Hypercalcemia
Hyponatremia
Hypermagnesemia
Hypophosphatemia
Hypernatremia
Subdural Hematoma
Hyperosmolar Coma
Wernicke-Korsakoff Syndrome
Alzheimer Disease
Alzheimer Disease in Individuals With Down Syndrome
Aphasia
Apraxia and Related Syndromes
Complex Partial Seizures
Dementia in Motor Neuron Disease
Dementia With Lewy Bodies
EEG in Dementia and Encephalopathy
EEG in Status Epilepticus
Frontal and Temporal Lobe Dementia
Generalized EEG Waveform Abnormalities
Huntington Disease
Intracranial Hemorrhage
Normal Pressure Hydrocephalus
Pick Disease
Status Epilepticus
Subdural Hematoma
Tonic-Clonic Seizures
Transient Global Amnesia
Other Problems to Be Considered
Drug intoxication
CVA
Encephalopathy from drugs normally excreted or metabolized by the kidney (ie, meperidine, cimetidine)
Dementia
Complex partial status epilepticus
Dementia in Huntington disease
Dementia in Parkinson disease
Dementia in progressive supranuclear palsy
Epileptic encephalopathies
Vascular dementia
EEG in coma
Tonic seizures
Workup
Laboratory Studies
1. Electrolytes, BUN, creat, & glucose
A- Markedly elevated BUN & creatinine levels indicate UE.
B- Obtain serum electrolyte & glucose measurements to rule out other causes:-
-hyponatremia, -hypernatremia,
- hyperglycemia &
-hyperosmolar syndromes
2. Obtain CBC to detect leukocytosis, which may suggest an infectious cause and determine whether anemia is present. (Anemia may contribute to the severity of mental alterations.)
3. Obtain serum calcium, phosphate, and PTH levels to determine the presence of hypercalcemia, hypophosphatemia, and severe hyperparathyroidism, which cause metabolic encephalopathy.
4. Serum magnesium levels may be elevated in a patient with renal insufficiency, particularly if the patient is ingesting magnesium-containing antacids. Hypermagnesemia may manifest as encephalopathy.
5. Order a toxicology screen in all patients.
6. Contributing to encephalopathy Medication levels
A- Determine detectabale drugs
digoxin,
lithium etc.
B- Some medications cannot be detected & are excreted by kidney. eg,
penicillin,
cimetidine,
meperidine,
Baclofen etc.
Imaging Studies
Brain imaging is of limited value.
CT and MRI studies typically show cerebral atrophy & secondary ventricular dilatation.
These studies are valuable for excluding intracranial hemorrhage & subdural hematoma when patients have an acute change in mental status.
Case reports have documented increased signal intensity in the cortical and subcortical areas of the parietal and occipital lobes.
These findings are thought to reflect local edema that resolved after dialysis treatments.
Improvement on MRI has been correlated with improved serum creatinine and BUN levels.
Imaging Studies
Severe symptoms
Obtain an MRI or head CT with severe neurologic symptoms to rule out structural abnormalities (eg, CVA, intracranial mass).
CT does not demonstrate any characteristic findings for UE.
With milder symptoms
initially treat with dialysis &
observe for neurologic improvement.
ROI placement. Axial FLAIR-prepped echo-planar T2-weighed images (TR/TE/TI, 10,000/91.7/2200; FOV, 40; b = 0 s/mm2) in a patient with PRES secondary to uremic encephalopathy. Nineteen ROIs were systemically placed in 22 patients with PRES and 18 control subjects, as shown. The images were coregistered to the ADC map, on which measurements were taken. Typical ROI sizes varied with brain region, as follows: cerebellum, 400 mm2; pons, 240 mm2; lenticular nucleus, 250 mm2; corticospinal tract, 60 mm2; posterior temporal lobe, 360 mm2; caudate head, 60 mm2; thalamus, 220 mm2; occipital lobe, 360 mm2; parietal lobe, 400 mm2; frontal lobe, 500 mm2.
A , MR image in a case of uremic encephalopathy shows marked frontal lobe involvement.
Other Tests
Electroencephalogram
An EEG is commonly performed on patients with metabolic encephalopathy.
Findings typically include the following:
(1) slowing and loss of alpha frequency waves,
(2) disorganization,
(3) intermittent bursts of theta and delta waves with slow background activity.
EEG in a 56-year-old man with uremic encephalopathy.
He became increasingly lethargic, requiring intubation.
EEG shows absence of a posterior dominant alpha rhythm and diffuse bilateral slowing with mixed theta- and delta-frequency signal.
A single sharp wave is present in the left occipital region, phase reversing at O1.
From top to bottom: Fp1-F7, F7-T3, T3-T5, T5-O1, O1-O2, O2-T6, T6-T4, T4-F8, F8-Fp2, Fp2-Fp1, F3-C3, C3-P3, P3-O1, F4-C4, C4-P4, P4-O2, Fz-Cz.
Reduction in frequency of EEG waves correlates with the decrease in renal function and the alterations in cerebral function.
After the initial period of dialysis, clinical stabilization may occur while the EEG findings do not improve. Eventually, EEG results move toward normal.
Aside from the routine EEG, evoked potentials (EPs) (ie, EEG signals that occur at a reproducible time after the brain receives a sensory stimulus [eg, visual, auditory, somatosensory]) may be helpful in evaluating uremic encephalopathy.
CRF prolongs latency of the cortical visual-evoked response.
Auditory-evoked responses are generally not altered in uremia, but delays in the cortical potential of the somatosensory-evoked response do occur.
Cognitive function tests
Several cognitive function tests are used to evaluate UE.
Uremia may result in worse performance on
The trail-making test:- which measures psychomotor speed.
The continuous memory test:- which measures short-term recognition.
The choice reaction time test:- which measures simple decision making.
Alterations in choice reaction time appear to correlate best with renal failure.
Histologic Findings
Brain histologic findings include:-
Meningeal fibrosis,
Glial changes,
Edema,
Vascular degeneration,
Focal & diffuse neuronal degeneration, and
Focal demyelination.
Small infarcts are also seen & are probably due to HTN or focal necrosis.
Cerebellar acute granule cell necrosis is observed.
Inflammatory ischemia and fibrosisDevelop.Hematoxylin/eosin staining reveals meningeal fibrosis
and inflammation
( B ) in the spinal cord.
( C ) Inflammation and fibrosis are shown also in the medulla oblongata.
( D ) CNPase immunoreactivity at the perivascular area shows that myelin is largely preserved. Necrotic lesions form around the inflamed perivascular areas
( E , hematoxylin/eosin) and show secondary myelin loss ( F , CNPase immunostaining).
Serial cerebellar brain sections stained with Bielschowsky silver staining
( G ), which stains neurons and axons, and luxol fast blue/periodic acid Schiff
( H ), which stains myelin, show an ischemic lesion where both axons and myelin are damaged.
Procedures
Lumbar puncture
Not routinely performed; however,
it is indicated to find other causes if a patient's mental status does not improve after initiation of dialysis .
No specific CSF finding indicates UE.
Lumbar puncture
Treatment
Medical Care
No medications are specific.
Care includes correcting metabolic disturbance
In ARF or CRF indication for early initiation of :-
Hemodialysis,
Peritoneal dialysis,
Continuous renal replacement therapy.
After beginning dialysis, patient generally improves clinically.
Note: EEG findings may not improve immediately.
In ESRD, EEG improve after several months but may not completely normalize.
Address the following factors,
Adequacy of dialysis
Correction of anemia
Regulation of calcium & phosphate metabolism.
Medical parathyroidectomy.
Infections need to be treated appropriately.
Seizures
May be treated with anticonvulsants.
These drugs should be administered at lower-than-usual doses to accommodate the low albumin levels observed in CRF.
Low albumin levels can lead to higher levels of unbound anticonvulsant.
The unbound drug is therapeutically active fraction.
Consultations your patient needs
Nephrologist
Vascular surgeon for placement of vascular access in patients with ESRD.
Neurologist if symptoms do not improve upon initiation of dialysis therapy.
Dietitian the one familiar with renal diseases.
Specialist in critical care medicine
Neurosurgeon Neurosurgical intervention for intracranial hemorrhage or subdural hematoma.
Infectious disease specialist: Bacterial meningitis remains a high cause of mortality in hemodialyzed patients, often because of delay in treatment.
Diet
To avoid malnutrition,
Maintain adequate protein intake (>1 g/kg/d).
Low-salt, low-protein (ie, renal) diet .
Activity
Instruct pts with significant symptoms to continue bed rest.
Follow-up
Further Inpatient Care:-
Admit for dialysis & further workup.
Patients need close follow-up in acute stage of uremic encephalopathy.
After underlying problem is treated properly, the symptoms should resolve.
Levels of anticonvulsant drugs must be closely monitored to prevent toxicity.
In cases of intracranial hemorrhage, serial head neuroimaging may be necessary.
Further Outpatient Care
Schedule maintenance HD for ESRD.
Carefully monitor mental status.
Inpatient & Outpatient Medications
Administer medications (eg, iron, erythropoietin, phosphate binders, vitamin D analogues) for patients with ESRD to optimize their quality of life.
Avoid sedatives.
Transfer & Deterrence/Prevention
Transfer
Patients may require transfer to a facility that can provide emergent hemodialysis .
Transfer to a facility with staff & equipment for further evaluation & care may be necessary.
As always, trained personnel with appropriate monitoring should perform the transfer.
Deterrence/Prevention
Refer patients with chronic renal insufficiency to a Nephrologist for regular monitoring of CrCl so that dialysis may be initiated before encephalopathy develops.
Complications Prognosis Patient Education
Complications
If untreated
Seizures
Coma
Death
Prognosis
The prognosis is generally favorable if treatment is successful.
With prompt dialytic therapy, the mortality rate is low.
Patient Education
To ensure that treatment is initiated early, instruct patients & their family members & caregivers about the need for prompt medical evaluation when mental status changes occur.
Medicolegal Pitfalls
Failure to recognize RF as the cause of encephalopathy in a patient who presents with altered mental status.
Failure to promptly initiate dialysis in a patient with UE.
Failure to adequately monitor drug levels may lead to toxicity & further complications.
Accidental falls may occur & can lead to litigation.
The slow onset of symptoms may lead to complications that might be grounds for litigation.
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