Compare conditions

Put any two — or three — conditions side by side, adult or pediatric, to spot the look-alike differences fast, row by row.

Hypernatremia

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In one line

·Sodium level is high because the body has too little water compared to salt.

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Normal physiology

·Your body keeps the balance between water and sodium in a narrow range by using thirst and a hormone called ADH (antidiuretic hormone). The hypothalamus (a control center at the base of your brain) senses when sodium is rising, triggers thirst so you drink, and makes ADH. ADH is stored and released by the pituitary gland (a pea-sized gland just below the hypothalamus) and travels through your blood to your kidneys. There, ADH tells the collecting ducts (the final tubes in each kidney that decide how much water leaves in urine) to open tiny water gates called aquaporin-2 channels, so water is pulled back into your blood instead of leaving as pee. This keeps sodium from climbing. Healthy people with access to water rarely develop high sodium because these systems work automatically and powerfully.

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What goes wrong

·High sodium (Hypernatremia) happens when water leaves your body faster than it comes in, or when you cannot drink enough to keep up with normal losses, or rarely when too much sodium is added. The most common causes are losing water (through diarrhea, vomiting, sweating, burns, or kidneys that cannot hold onto water) and not being able to replace it (because of broken thirst, no access to water, or being too sick or confused to drink). In older adults and people with dementia, the thirst signal is often blunted or ignored. In babies, thirst cannot be communicated. In diabetes insipidus—either central (the hypothalamus or pituitary stops making or releasing ADH) or nephrogenic (the kidneys ignore ADH)—the kidneys flush out huge volumes of dilute urine no matter how high the sodium climbs, and unless the person drinks enormous amounts of water constantly, sodium rises. Burns and severe diarrhea cause large water losses through the skin or stool. Rarely, someone drinks seawater, is given a wrongly concentrated sodium IV solution, or takes in baking soda or salt tablets in huge amounts, directly adding sodium. Once water is lost or sodium is added, the concentration of sodium in the blood climbs above 145 mEq/L.

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Hallmark signs

·Thirst
·Confusion or trouble thinking clearly
·Muscle weakness or twitching
·Irritability or restlessness
·Seizures
·Extreme drowsiness or coma
·Very little urine output (in some causes)
·Very large amounts of urine (in diabetes insipidus)

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Red flags · escalate now

·Seizure or sudden collapse—means the brain is in immediate danger from severe cell shrinkage.
·Cannot wake the person or they are deeply confused—sign of life-threatening brain dysfunction.
·Sodium above 160 mEq/L or rising faster than 0.5 mEq/L per hour—rapid or extreme rises can tear small blood vessels in the brain.
·No urine for many hours despite drinking, or urine output suddenly stops—may mean the kidneys are failing.

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Workup

·Serum sodium (part of basic metabolic panel)
·Serum glucose
·Urine osmolality
·Urine sodium
·Serum osmolality
·Water deprivation test (if diabetes insipidus suspected)
·Medication review

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Treatment

·Give free water by mouth, or give D5W (5% dextrose in water) IV if patient cannot drink
·Correct sodium slowly — drop sodium by no more than 10 mEq/L per 24 hours (goal 0.5 mEq/L per hour maximum)
·For central diabetes insipidus, give desmopressin (DDAVP) — synthetic ADH
·For nephrogenic diabetes insipidus, give thiazide diuretic (hydrochlorothiazide or amiloride) plus low-sodium, low-protein diet
·Find and fix the root cause — stop medications causing water loss (lithium, diuretics), treat fever, cover burns, restore access to water, or treat the brain injury affecting thirst
·Replace ongoing insensible water losses (breathing, sweating, fever) with scheduled water intake or IV fluids
·Monitor sodium every 2–4 hours during correction to avoid overcorrection

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NCLEX trap

·Normal saline has 154 mEq/L of sodium in every liter. In high sodium (hypernatremia), sodium is already too high. Giving normal saline will push sodium even higher and shrink the brain more. Give free water (by mouth if the patient can swallow, or D5W — sugar water with no sodium — IV) slowly instead. The goal is to lower sodium, not raise it. If blood pressure is truly low, give a smaller volume of saline first to stabilize the circulation, then switch to free water.
·Lower sodium slowly: no more than 10 mEq/L in 24 hours (about 0.5 mEq/L per hour). If you fix it too fast, water rushes into brain cells, the brain swells (cerebral swelling (edema)), and the patient can seize or even die. Slow correction lets brain cells gently release the extra particles (osmolytes) they made to protect themselves. Speed kills in high sodium (hypernatremia) — the harm comes from fixing it wrong, not from the high sodium itself.
·High sodium (Hypernatremia) almost always means water loss is bigger than water intake, not that salt intake is too high. The upstream breaks are: diabetes insipidus (kidneys cannot hold onto water), fever or sweating (insensible loss — water evaporating from skin and lungs), vomiting or diarrhea (water loss from the gut), or broken thirst drive (patient cannot feel thirsty or cannot get water, common in the elderly or after a stroke). True salt poisoning is rare — it takes drinking seawater or eating handfuls of salt to cause high sodium from intake alone.
·Diabetes insipidus has nothing to do with blood sugar or insulin. It means the kidneys are dumping huge amounts of dilute (watery) urine because either the brain is not making ADH (antidiuretic hormone, also called vasopressin — the hormone that tells kidneys to hold water), or the kidneys cannot respond to ADH. Insulin will not help. For central diabetes insipidus (brain not making ADH), give desmopressin (DDAVP — a synthetic copy of ADH). For nephrogenic diabetes insipidus (kidneys ignoring ADH), give a thiazide diuretic plus a low-salt diet (the diuretic makes the kidney hold a little water by a back door). The upstream break tells you which medicine to use.
·Seizures in high sodium (hypernatremia) happen because you fixed it too fast, not because it is still too high. When you drop sodium quickly, water rushes into brain cells, the brain swells (osmotic demyelination is the opposite problem — that is from fixing low sodium (hyponatremia) too fast, but cerebral swelling (edema) is the risk here), and the patient seizes. Slower correction and head-of-bed elevation are the answers, not faster correction. Do not make the mistake twice — stop the fluids, recheck sodium, and slow the rate.
·Confusion in high sodium (hypernatremia) is real and dangerous — the brain is shrinking because water is being pulled out of brain cells into the bloodstream. It is not dementia; it is the high sodium itself. Fix the high sodium slowly, and the confusion will improve. Do not miss this reversible cause. Elderly patients are at highest risk because their thirst drive fades with age and they forget to drink.

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