A presentation about the clinical approach to hypernatremia, particularly in the elderly population, developed for a micro-teaching session as part of the RCP Educator Accreditation.

1. Hypernatremia in
the elderly:
a refresher
Dr. Sharma
IMT1, Care of the Elderly,
Whiston Hospital

2. Learning
objectives
To be to able to recognise and define
hypernatremia.
To be aware of the various causes of
hypovolemic hypernatremia.
To be familiar with the concept of the
‘free water deficit’ and aware of
tools that can be used to calculate
this.
To be aware of treatment options for
this electrolyte disturbance.

3. Case
• A 84-year old lady, with a
history of Alzheimer’s dementia
and osteoporosis, was admitted
to hospital with reduced oral
intake and increased urinary
frequency.
• She was commenced on
nitrofurantoin. Bloods were
otherwise stable, and bladder
scan showed no evidence of
urinary retention.
• She was discharged to an urgent
respite care placement as her
husband had not been coping at
home.

4. Case (cont.)
• She was readmitted 10 days later due to concerns about lethargy, confusion, no
food or fluid intake and no urine output recorded for 3 days.
• She was unable to provide much of a history, but her daughter reiterated that
this was a fairly acute deterioration and 3 weeks prior to this, she was
mobilising around her house with a zimmer.
• Bloods taken 10 days apart were as follows:
• Na 167 (145)
• K 3.2 (3.2)
• Urea 39.7 (5.7)
• Creatinine 342 (48)  consistent with AKI Stage 3
+ Residual volume in the bladder post-catheterisation was approx. 300-400 mL

5. A salty pill to swallow…
• 1 in 5 care home residents are dehydrated. (Hooper at
al, 2016)
• Serum sodium deviations are associated with mortality in
a dose-dependent way. (Thongprayoon et al.,2020).
• A recent, small study of acute general medical
admissions in the U.K. showed that hypernatremia
occurred in exclusively older patients, and was sodium
levels were statistically higher in nursing home
residents. (Brennan et al., 2021)

6. Definition
• This is defined as a serum sodium level of >145 mM.
• Acute hypernatremia occurs within < 48 hours, whereas chronic hypernatremia
occurs over > 48 hours.
• Almost all cases of hypernatremia are associated with hyperosmolality and
hypovolaemia. This is caused by a relative loss of H2O that exceeds the loss of
salt.
+ N.B. You can also develop a HYPOnatremia with fluid loss, but in these cases the relative
loss of SALT exceeds water.
• This occurs due to free water loss or inadequate intake.

7. Risk factors
Risk factors
• High urine/stool output
• Inability to drink
water/limited access to
water/lack of thirst
• Inability to concentrate urine
(e.g. diabetes insipidus,
osmotic diuresis/free water
diuresis, obstructive uropathy,
renal failure)
Full drug history (esp.
lithium, loop diuretics,
Mannitol, laxatives)

9. Clinical approach
• Assess for:
+ Sources of fluid loss
+ Fluid intake
+ Urine output
• Symptoms
+ Acute: lethargy, weakness, irritability 
seizures, stupor, coma and death
+ Chronic: non-specific

10. CLINICAL SIGNS?
• Signs
+ Volume status
• Oliguria
• Weight loss
• Orthostatic
hypotension
• Tachycardia
• Dry mucosa

11. Free water deficit
TBW (total body water) =
patient’s body weight
(kg) x 0.5 (women/older
men) OR x 0.6 (younger
men/children) OR 0.4 in
the dehydrated patient.

12. YOUR TURN!
• Calculate the free water
deficit using:
+ Age = 84
+ TBW = 60 kg

13. Fluid replacement
• Identify and correct
the cause
• The rate is dependent
on acuity of
hypernatremia (over
24 hours if acute OR
≈3 mL/kg/hour, 48-72
hours if chronic
approx. by ≈10 mM/day
OR ≈1.35 mL/kg/hour)

15. What fluids?
Rule-of-thumb is give 50% of the free water deficit over the
first 24 hours, then the other 50% over the following day.
The oral or nasogastric route is preferred, but fluids can
be given IV if this is not possible.
Hypotonic solutions should be selected:
• E.g. Hypotonic saline and dextrose (NaCl 0.18% + 4% dextrose)
• Ensure other electrolyte abnormalities are corrected
• If the patient is haemodynamically compromised, you should start with an
isotonic solution

16. Conclusions
• The most common cause of hypernatremia is dehydration secondary to free water
losses/reduced intake leading to hypovolaemia.
• Treatment is with hypotonic solutions and based on the acuity or chronicity of
the presentation.
• Hypernatremia is associated with mortality and morbidity in the elderly
population.

17. Sources
1. Hypernatremia, BMJ Best Practice
2. Hooper et al, Journals of Gerontology, 2016
3. Thongprayoon et al., Nephrology Dialysis Transplantation, 2020
4. Brennan et. al, Age and Ageing, 2021
5. Adrogue et al., NEJM, 2000

19. Kim, Electrolytes & Blood Pressure, 2006