abnormal sodium
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Abnormal Sodium. National Pediatric Nighttime Curriculum Written by Julia Aquino, MD Floating Hospital for Children at Tufts Medical Center. Learning objectives. After this module learners will be able to: - PowerPoint PPT PresentationTRANSCRIPT
Abnormal Sodium
National Pediatric Nighttime Curriculum
Written by Julia Aquino, MD
Floating Hospital for Children at Tufts Medical Center
Learning objectives
After this module learners will be able to:
Describe principles of acute fluid management in the correction of hypernatremia and hyponatremia
Recognize the signs and symptoms that require immediate attention in patients with disordered sodium
Consider the level of care appropriate for patients requiring correction of hypernatremia and hyponatremia
Case #1 (intern)
You have just finished sign out and you are reviewing your patient list to prioritize the most ill patients when your pager goes off:
“Lab called with critical value for patient in 735: sodium 160. Please advise.
–Kevin”
You review your sign out…
7 month old otherwise healthy male admitted directly from clinic in the late afternoon with gastroenteritis and dehydration. He has had minimal PO intake and decreased urine output.
Tachycardic and febrile when the admitting team saw him but otherwise stable.
Overnight plan: floor staff is placing an IV, giving a 20cc/kg NS bolus and will call night team to reassess when complete.
You head to room 735
As you go to the bedside to assess the
patient, you review some questions:
What are possible etiologies of hypernatremia? What about in this patient specifically? What do I need to worry about immediately? Should I call my senior? Can I take care of this patient on the floor or
does he need a higher level of care?
At the bedside
VS: T 38.5, HR 120, RR 30, BP 90/60, O2 sat 99% RA
His nurse, Kevin, tells you that the NS bolus is almost complete and that the patient has been irritable since arriving to the floor
Physical exam: General: irritable infant; HEENT: mucous membranes dry, anterior fontanelle slightly sunken; Chest: clear; CV: tachycardic, regular rhythm, II/VI systolic ejection murmur; Abdomen: soft, hyperactive bowel sounds; Extremities: normal skin turgor, cap refill 3 seconds
What is your overall assessment of this patient?
What is your next step?
A) Stop the bolus—this patient is hypernatremic and NS is an inappropriate fluid choice
B) Give another 20cc/kg bolus of NS
C) Call a renal consult
Next steps
You give another normal saline bolus and the patient’s perfusion, heart rate and mental status start to normalize
Kevin asks you what fluids you want to hang now….
What do you need to consider when correcting the sodium in hypernatremic dehydration?
What do you need to worry about if correcting too fast?
Calculating free water deficit
Free water deficit is the minimum amount of fluid necessary to correct serum sodium
Estimate of free water deficit: 4mL x body weight x desired change in sodium
Goal is to correct sodium at a rate no faster than 0.5 mEq/L/hour
Add maintenance fluid needs and account for any ongoing losses
Ongoing management
What fluid should you choose?
When should you recheck a sodium?
Hypernatremia Defined as serum sodium >/= 145mEq/L
Causes:
Excess sodium intake Concentrated formula, salt ingestion (seawater, accidental, Munchausen-by-proxy), hypertonic IV fluids, sodium bicarbonate, blood products
Increased free water losses 1) Renal: diabetes insipidus, diuretics, tubular disorder
2) GI: diarrhea, vomiting, colostomy/ileostomy output, malabsorption
3) Insensible: fever, tachypnea, burns
Decreased free water intake Ineffective breastfeeding, poor access to water, blunted thirst mechanisms, fluid restriction
Clinical Manifestations and Evaluation of Hypernatremia Early neurologic signs include agitation and
irritabilitycan progress to seizure and coma
Neurologic exam can reveal increased tone, brisk reflexes and nuchal rigidity
Lab evaluation can include: Serum osmolarity Serum glucose Urine osmolarity and specific gravity
Neurologic Sequelae
In acute phase: Intracellular fluid moves to extracellular space-
volume loss in brain separation from meninges
If hypernatremia has existed for >2-3 days: Neurons protect themselves by making osmolytes to
maintain gradient With rapid correction, neurons can swell leading to
cerebral edema
Mortality estimated at 10-16% despite correct rate of rehydration
Case #2 (senior)
You are doing your late evening rounds on the ward when one of the nurses pulls you aside:
“One of the post-op orthopedic patients has a sodium of 115 and I can’t reach the primary team. Can you help me?”
His nurse gives you more info…
Patient is a 16yo with cerebral palsy and global developmental delay who is post-operative day #2 from posterior spinal fusion.
He has been wretching and not tolerating g-tube feeds so has been on maintenance IV fluids of D5 ½NS + 20mEq/L KCl all day.
His mother is at the bedside and feels he is not himself.
At the bedside
VS: T 38.0, HR 90, BP 100/75, RR 20, O2 98%RA
General: neurologically impaired child moaning in bed, less responsive to voice/touch per mother; HEENT: lips dry, mucous membranes slightly dry; Chest: CTAB; CV: RRR, nl S1, S2; Abdomen: g-tube intact, hypoactive bowel sounds; Extremities: well perfused; Neuro: increased tone and spasticity in extremities, responds to voice with a moan, responsive to painful stimuli
Next steps
You initiate a rapid response and transfer to the PICU should happen shortly. Your immediate next step should be:
A)Prompt administration of hypertonic saline (3%)
B)Emergent head CT
C)Fluid restriction due concern for SIADH
Your patient stabilizes…
Your patient is returning to baseline mental status and you stop the hypertonic saline.
What general guidelines do you use to think about ongoing fluid management?
Why are you worried about the rate of correction?
Hyponatremia
Defined as serum sodium </=135
Occurs in 3% of hospitalized patients
Kidney protects against hyponatremia by excreting free water as dilute urineHyponatremia is an increase in total body
water rather than a decrease in serum sodium
Causes of hyponatremiaDecreased total body water
GI losses (diarrhea, emesis), diuretics, RTA, 3rd spacing
Increased total body water CHF, acute renal failure, SIADH, water intoxication (dilute formula feeding)
Normal total body water Hypoglycemia
Pseudohyponatremia Severe hyperlipidemia or hypoproteinemia
•Hyperglycemia leads to hyperosmolarity with translocation of fluids from intracellular to extracellular space
•Pseudohyponatremia: displacement of plasma water resulting in falsely low serum by laboratory measurement
Clinical manifestations of hyponatremia
Neurologic symptoms related to edema caused by hypo-osmolarity Children at higher risk due to higher brain-to-skull ratio
Symptoms include headache, nausea, emesis, weakness
Severity worsens as edema increases leading to signs of cerebral herniation Respiratory changes, posturing, pupillary changes, seizure
Lab evaluation of hyponatremia
Serum osmolarity if concerned for pseudohyponatremia
Urine osmolarity to evaluate for impaired ability to excrete free water
Urine sodium <25 mEq/L consistent with volume depletion >25Meq/L consistent with renal tubular dysfunction, SIADH,
diuretic use Must be interpreted with caution since affected by IV fluids, fluid
restriction, diuretic use
Fluid management goals Hyponatremia with neurologic symptoms is a
medical emergency
Clinical picture Fluid Rate
Seizure 3% hypertonic saline raise serum sodium by 4-8 mEq/L/hour until seizure activity stops
No seizure activity but not at neurologic baseline
3% hypertonic saline raise serum sodium by 1mEq/L/hour until: -patient at baseline-plasma sodium increases by 20-25mEq/L OR -serum sodium increases to 125-130mEq/L
Asymptomatic 0.9% normal saline raise sodium no faster than 0.5 mEq/L/hour
Why are we concerned about the rate of correction? Excessive changes in serum sodium can lead to cerebral
demyelination (central pontine myelinolysis) Usually occurs several days after correction Presents with confusion, quadriplegia, confusion or pseudocoma
Recent data shows rate of correction may have little affect on development of demyelination Magnitude of correction and underlying illness more important
contributing factors
Risk of untreated hyponatremia far exceeds that of rapid correction so do not hesitate to use hypertonic saline for symptomatic patients
Key learning points
Always prioritize hemodynamic stability over sodium correction
Correction calculations for both hypernatremia and hyponatremia are general guidelines—sodium should be monitored frequently to ensure safe rate of correction
Symptomatic hyponatremia is a medical emergency and should be managed in a closely monitored setting with 3% hypertonic saline
References Chung C, Zimmerman D. Hypernatremia and
hyponatremia: current understanding and management. Clin Ped Emerg Med. 2009; 10: 272-278.
Moritz M and Ayus JC. Disorders of water metabolism in children: hyponatremia and hypernatremia. Pediatr Rev. 2002; 23: 371-380.
Schwaderer AL, Schwartz GJ. Treating hypernatremic dehydration. Pediatr Rev. 2005; 26: 148-150.
Waseem M, Hussain A. Index of suspicion. Pediatr Rev. 2004; 25: 397-399.
Questions:1) A 1 month old patient with RSV bronchiolitis and
dehydration develops vomiting and altered mental status leading to generalized a tonic-clonic seizure. Her serum sodium is 118 mEq/L. The most likely mechanism for her clinical deterioration is:
A) Demyelination
B) Cerebral edema
C) Brainstem herniation
D) Intracranial hemorrhage
Questions:A) Incorrect. Demyelination can occur as result of hyponatremia, but it usually presents several days following the change in sodium with confusion, pseudocoma or a “locked-in” state. Recent data suggests that it is not the rate of correction that leads to demyelination, rather the magnitude of correction necessary and the underlying illness.B) Correct. Hyponatremia leads to an influx of fluid from the extracellular space to the intracellular space cause cerebral edema. Early neurologic manifestations including headache, vomiting, seizure and altered mental status are a direct result.C) Incorrect. Cerebral edema from hyponatremia can lead to brainstem herniation, but this would present with respiratory arrest, asymmetric pupillary changes or decorticate posturing.D) Incorrect. Hyponatremia rarely leads to intracranial hemorrhage. Hypernatremia can cause this due to acute loss of brain volume from loss of fluid from the intracellular space leading to rupture of cerebral veins.
Questions:2) The goal rate of correction for a patient with a
serum sodium of 165 mEq/L who is hemodynamically stable is:
A) As quickly as possible
B) 0.01 mEq/hour
C) 0.5 mEq/hour
D) 2 mEq/hour
Questions:The correct answer is C. This is a straight forward knowledge question, requiring the learner to recall the goal rate of sodium correction in a patient with hypernatremia who is hemodynamically stable.
Questions:3) A 3 year old is admitted with gastroenteritis and
dehydration. His serum sodium is 167 mEq/L. Once he is hemodynamically stable, fluid management should be focused on providing:
A) Glucose
B) Free water
C) Sodium
D) Potassium
E) Chloride
Questions:B is the correct answer. Hypernatremia is a total body free water deficit rather than an excess of sodium.
Questions:4) All of the following are possible etiologies for
hyponatremia EXCEPT:
A) Dilute formula feeding
B) SIADH
C) Diabetes insipidus
D) Non-osmotic release of ADH secondary to acute illness
Questions:C is the correct answer. Diabetes insipidus leads to hypernatremia.
Questions:5) A 2 year old patient with central diabetes
insipidus is admitted with a sodium of 170 mEq/L. The labs findings most consistent with his diagnosis are:
A) Elevated serum osmolarity and concentrated urine
B) Decreased serum osmolarity and dilute urine
C) Decreased serum osmolarity and concentrated urine
D) Elevated serum osmolarity and dilute urine
Questions:D is the correct answer. Central diabetes insipidus leads to decreased ADH production. This leads to an inability to concentrate urine and an increase in serum osmolarity, hypernatremia and dilute urine.
Questions:6) A 4 month old has been receiving improperly
mixed formula with 1 scoop per 4 oz of water. She presents with generalized tonic-clonic seizure and a serum sodium of 118 mEq/L. The appropriate fluid to use for immediate management of her hyponatremia is:
A) Normal saline
B) 1/2 Normal saline
C) 3% Hypertonic saline
D) None-fluid restrict due to concern for SIADH
Questions:C is the correct answer. This is a straightforward knowledge question requiring learners to recall that symptomatic hyponatremia is an emergency requiring prompt treatment with hypertonic saline.