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Nursing Field Notes / Renal + Fluid · Fundamentals of Nursing

Magnesium, Calcium & Phosphate 🧲

Fluid & Electrolyte Basics II — the mellow one, the contracting one, and the mirror

NG-134 RENAL + FLUID ADHD-friendly visual edition

Three electrolytes, three one-word jobs: Magnesium MELLOWS the muscles 🧲 · Calcium CONTRACTS the muscles 💪 · Phosphate is calcium's MIRROR 🔁. Learn the verb and the signs write themselves — because low mellow means excited, and high mellow means depressed.

📄 Simple Nursing original — opens in Drive →

🧲 Mg MELLOWS1.3–2.1 mEq/L · Low Mg = excited (Torsades!) · High Mg = depressed (no reflexes).
🦴 Ca CONTRACTS9.0–10.5 mg/dL · Keeps the 3 B's strong: Bones, Blood clotting, Beats.
🔁 PO₄ is the MIRROR3.0–4.5 mg/dL · Calcium up = phosphate down. Always inverse.
🚨 Mag toxicity antidoteIV CALCIUM GLUCONATE — and STOP the magnesium infusion first.
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THE GROUND RULES

STEP 1 · THREE VERBS

One verb per electrolyte. Get the verb and you can rebuild every symptom list from scratch.

🧪 The 5-band scale you will use three times on this page

Read the number → name the band → the band names the plan. Outside NORMAL = nursing action; inside a CRITICAL band = provider call + cardiac monitor.

🧪 THE 5-BAND VALUE SCALE Mg²⁺ in mEq/L · Ca²⁺ and PO₄³⁻ in mg/dL — always read the units CRITICAL LOW LOW · hypo- NORMAL RANGE HIGH · hyper- CRITICAL HIGH 🚨 provider + monitor ⚠️ replace it ✅ keep it there ⚠️ remove / bind it 🚨 antidote + monitor Critical ("panic") thresholds vary by lab and some texts use different units (mEq/L). Always read the units on YOUR lab slip.
🧠 “BAND then PLAN.” Same scale, three electrolytes. The only thing that changes is the numbers printed under it.

🧲 M = Magnesium MELLOWS the muscles

Magnesium is the body's sedative. It calms nerve & muscle firing and steadies the heart's rhythm.

  • 📉 LOW mellow = EXCITED! hyperreflexia · diarrhea · Torsades de Pointes
  • 📈 HIGH mellow = SEDATED. hyporeflexia · hypoactive bowel · depressed respirations · heart block
🧠 “Mag is the chill pill.” Not enough chill → the body is jumpy. Too much chill → the body falls asleep, including the diaphragm.

🦴 C = Calcium CONTRACTS the muscles

Calcium keeps the 3 B's STRONG:

  • 🦴 B — BONE
  • 🩸 B — BLOOD (clotting)
  • 🫀 B — BEATS (heart)

Calcium and magnesium are opposites at the muscle: calcium contracts, magnesium relaxes.

🧠 “Low CALM = EXCITED!” Low calcium leaves nerves twitchy → Trousseau's, Chvostek's, tetany. High calcium = “high & calm” → sluggish, constipated, weak.

🔁 Phosphate is calcium's mirror — always INVERSE

  • ⬆️ Ca HIGH = PHOSPHATE LOW — so hypophosphatemia looks like high calcium
  • ⬇️ Ca LOW = PHOSPHATE HIGH — so hyperphosphatemia looks like low calcium
  • 🫘 Renal failure / CKD is the classic driver: the failing kidney cannot excrete phosphate → PO₄ climbs, Ca falls TEST TIP
  • 🦋 PTH (parathyroid hormone) is the switch: high PTH = high calcium (and low phosphate) · low PTH = low calcium (and high phosphate)
🧠 “Ca and PO₄ are on a seesaw; PTH sits on calcium's end.” Push PTH up, calcium rides up and phosphate drops.
🧲

MAGNESIUM · Mg²⁺

STEP 2 · MELLOWS THE MUSCLES

Low mellow = excited (and the excited heart rhythm is Torsades). High mellow = sedated (and the antidote is calcium).

🧪 Magnesium value scale

NORMAL 1.3 – 2.1 mEq/LCRITICAL <1.0 or >4.0
🧲 MAGNESIUM (Mg²⁺) units: mEq/L — some texts report mg/dL (about 1.6–2.6 mg/dL) 1.3–2.1 <1.0 CRIT LOW 1.0–1.2 HYPOmagnesemia 1.3–2.1 NORMAL 2.2–4.0 HYPERmagnesemia >4.0 CRIT HIGH Low band 🚨 Torsades de Pointes · High band 🚨 no reflexes, depressed breathing. Critical cutoffs vary by lab.
🧠 “1.3 to 2.1 — mag is a small number.” Anything with a 3 or higher in front of the decimal is already toxic territory.

⭐ What magnesium actually does

  • 😌 Calms nerve impulses & muscle contraction (a natural calcium blocker)
  • 🫀 Stabilizes the cardiac rhythm — it is the drug for Torsades de Pointes
  • 🔑 Unlocks potassium — potassium will NOT correct until magnesium is corrected
  • 🦴 Helps build bone and activates vitamin D & PTH

TEST TIP A client with refractory hypokalemia — the K⁺ keeps coming back low no matter how much you replace — check the magnesium.

🧠 “Mag is the key to the potassium door.” No mag, no matter how much potassium you pour in, it walks right back out the kidney.

📉 HYPOmagnesemia — below 1.3 · LOW MELLOW = EXCITED!

Causes — mostly “can't absorb it” or “washed it out”

  • 🌀 Crohn's disease — malabsorption
  • 🌾 Celiac disease — malabsorption
  • 🍺 Alcoholism — the classic exam client
  • 🍽️ Malnourishment, prolonged NPO, TPN without supplementation
  • 💩 Chronic diarrhea, NG suction, vomiting
  • 💊 Loop & thiazide diuretics, long-term PPIs

Manifestations (S/S) — everything is excited

  • 🔨 DTR = HYPERreflexia (increased DTR), tremors, twitching, tetany, positive Trousseau's & Chvostek's (because calcium falls with it)
  • 🚽 GI = excited: diarrhea & hyperactive bowel sounds
  • 🫀 Heart = excited: TORSADES DE POINTES — TOP TESTED and V-fib; hypertension; prolonged QT
  • 🧠 Seizures, confusion, agitation, insomnia
🧠 “No mag = no brakes.” Take away the body's sedative and everything revs: reflexes up, bowels up, heart twisting into Torsades. Torsades = the “twisting” rhythm = give magnesium.

📈 HYPERmagnesemia — over 2.1 · HIGH MELLOW = SEDATED

Causes

  • 🫘 RENAL FAILURE — the #1 cause (magnesium exits through the kidney)
  • 🧴 Magnesium-containing antacids & laxatives — milk of magnesia, magnesium citrate, magnesium hydroxide
  • 💉 Magnesium sulfate infusions — preeclampsia / preterm labor
  • 🩹 Adrenal insufficiency, DKA, excess supplementation

Manifestations (S/S) — everything is depressed

  • 🔨 DTR = HYPOreflexia (decreased DTR) — the FIRST warning sign, checked at the patellar reflex
  • 🫁 LUNGS = depressed respirations — STOP the infusion if RR is below 12
  • 🚽 GI = hypoactive bowel sounds, nausea, constipation
  • 🫀 HEART: heart block, hypotension & bradycardia → cardiac arrest
  • 🥵 Flushing, feeling warm, lethargy, slurred speech, drowsiness
🧠 “Too mellow to move, too mellow to breathe.” Reflexes fade first, then the respirations, then the heart blocks. Check the DTRs before you ever hear a bad breath sound.

🔨 The DTR check — one reflex hammer answers both directions

📉 LOW Mg — HYPERreflexia DTR 3+ to 4+ · brisk BIG kick ⬆ + tremors · tetany · seizures 🚨 Torsades de Pointes ✅ NORMAL Mg DTR 2+ · expected normal kick Calm muscles, steady rhythm this is what you are protecting 📈 HIGH Mg — HYPOreflexia DTR 1+ → 0 · absent no kick ❌ FIRST sign of mag toxicity 🚨 then RR < 12 → STOP infusion
🧠 “Reflexes are the mag gauge.” Brisk = too little mag. Gone = too much mag. The reflex hammer is cheaper and faster than the lab.

🚨 EMERGENCY ORDER — MAGNESIUM TOXICITY (calcium gluconate is the antidote)

🚨 STOP the magnesium infusion → give IV CALCIUM GLUCONATE Calcium is magnesium's direct opposite at the nerve and muscle, so calcium gluconate reverses magnesium toxicity. Keep it at the bedside for any client on a magnesium sulfate drip.
1
🛑 STOP the magnesium — the infusion, the mag antacids, the mag laxatives. Stop the source first, always.
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2
💉 IV CALCIUM GLUCONATE — the ANTIDOTE. Give slowly with continuous cardiac monitoring.
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3
🫁 Support the airway & breathing — O₂, bag-valve-mask and intubation equipment ready; the diaphragm is what fails.
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4
🚽 Increase excretion — IV fluids + a loop diuretic if kidney function allows.
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5
🩺 DIALYSIS — the definitive removal in renal failure or a severe level.

The order toxicity announces itself in — memorize this sequence:

🌡️ AS THE MAGNESIUM LEVEL CLIMBS → NORMAL ARREST 1️⃣ Flushed warm · lethargic nausea 2️⃣ DTR fades patellar reflex EARLIEST alarm 3️⃣ RR < 12 depressed STOP INFUSION 4️⃣ Heart block bradycardia hypotension 5️⃣ Arrest respiratory then cardiac Assess in this order every hour on a mag drip: LOC → deep tendon reflexes → respiratory rate → urine output (at least 30 mL/hr) → cardiac rhythm. Serum thresholds differ between mg/dL and mEq/L reporting — trust the assessment findings, not a memorized number.
🧠 “Reflex, Respirations, Rhythm — then Rescue with calcium.” Four R's, in that order. If the DTRs are gone or the RR is under 12, you stop the mag and get the calcium gluconate.

💊 EMERGENCY ORDER — HYPOmagnesemia (and the Torsades answer)

1
🫀 Cardiac monitor + seizure precautions. The danger is Torsades de Pointes and seizures.
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2
💉 Torsades de Pointes → IV MAGNESIUM SULFATE — this is the drug for that rhythm. NCLEX TIP
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3
💧 Replace magnesium: IV magnesium sulfate on a pump for severe/symptomatic; oral magnesium for mild — oral mag causes diarrhea, which loses more magnesium.
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4
🧪 Check K⁺ and Ca²⁺ with it — they fall together and will not correct until the magnesium does.
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5
🔨 While replacing, monitor for the opposite problem — check DTRs and respiratory rate; you can push a client straight into mag toxicity.
🥬Dark leafy greensspinach
🥜Nuts & seeds
🫘Legumes
🌾Whole grains
🍫Dark chocolate
🥑Avocado
🐟Fish
🍌Banana
🧠 “Torsades TWISTS — magnesium UNTWISTS.” The rhythm that twists around the baseline gets magnesium every single time.

⚖️ Hypo vs hyper magnesium — tell them apart

System📉 HYPOmagnesemia < 1.3📈 HYPERmagnesemia > 2.1
One wordEXCITED (low mellow)SEDATED (high mellow)
DTRHYPERreflexia ⬆, tremors, tetanyHYPOreflexia ⬇ → absent — first sign
GIDiarrhea, hyperactive bowel soundsHypoactive bowel sounds, constipation
RespiratoryBronchospasm, laryngospasm, stridorDepressed respirations — hold if RR < 12
HeartTorsades de Pointes, V-fib, prolonged QT, ↑ BPHeart block, bradycardia, hypotension
Top causesCrohn's, celiac, alcoholism, malnourishmentRenal failure, mag antacids/laxatives, mag drips
TreatmentGive magnesium sulfateSTOP mag + IV calcium gluconate
🧠 Everything about magnesium is a mirror. Whatever low mag does, high mag does the opposite — and the treatments are opposites too.
🦴

CALCIUM · Ca²⁺

STEP 3 · CONTRACTS THE MUSCLES

Low calcium = twitchy and excited (two named signs). High calcium = sluggish, stony and constipated.

🧪 Calcium value scale

NORMAL 9.0 – 10.5 mg/dLCRITICAL <7.0 or >13.0
🦴 CALCIUM (Ca²⁺) — total units: mg/dL · ionized calcium ≈ 4.5–5.6 mg/dL 9.0–10.5 <7.0 CRIT LOW 7.0–8.9 HYPOcalcemia 9.0–10.5 NORMAL 10.6–13.0 HYPERcalcemia >13.0 CRIT HIGH Low albumin lowers TOTAL calcium without lowering the active ionized calcium — check ionized Ca in low-albumin clients.
🧠 “Nine to ten-and-a-half — bones, blood, beats.” Three B's, one narrow range.

⭐ Calcium keeps the 3 B's STRONG

  • 🦴 B — BONE. No calcium = weak bones = fractures
  • 🩸 B — BLOOD (clotting). No calcium = weak clotting = risk for bleeding
  • 🫀 B — BEATS (heart). No calcium = weak beats = cardiac dysrhythmias

The PTH switch: LOW PTH = LOW calcium · HIGH PTH = HIGH calcium. Vitamin D is required to absorb calcium from the gut.

🧠 “Bones, Blood, Beats — the 3 B's break without calcium.” Every hypocalcemia symptom is one of the three B's going weak.

📉 HYPOcalcemia — below 9.0 · LOW CALM = EXCITED!

Causes

  • 🦋 HYPOparathyroidism → LOW PTH = LOW CALCIUM — including accidental parathyroid injury during a thyroidectomy
  • 🫘 Renal failure TEST TIP Chronic kidney disease (CKD) — phosphate climbs, calcium falls
  • ☀️ Low vitamin D, poor intake, malabsorption (Crohn's, celiac, gastric bypass)
  • 🩸 Massive blood transfusion (citrate binds calcium), acute pancreatitis, low magnesium, alkalosis

Manifestations (S/S)

  • 1️⃣ T — TROUSSEAU'S SIGN: “twerking arm when the BP cuff is on” — tetany: muscle spasms all over
  • 2️⃣ C — CHVOSTEK'S SIGN: “cheek smile when stroking the face”
  • 3️⃣ DIARRHEA & hyperactive bowel sounds, abdominal cramping
  • 4️⃣ WEAK B's — weak bones = fractures · weak blood clotting = risk for bleeding · weak beats = cardiac dysrhythmias (prolonged QT)
  • 🫁 LARYNGOSPASM & stridor — airway emergency; numbness/tingling around the mouth & fingertips; seizures
🧠 “T then C — Trousseau's Twerks, Chvostek's smiles at the Cheek.” T comes before C in the alphabet and Tourniquet (BP cuff) is the T sign. Both mean: this client is short on calcium and heading toward tetany.

📈 HYPERcalcemia — over 10.5 · HIGH CALM = SLUGGISH

Causes

  • 🦋 HYPERparathyroidism → HIGH PTH = HIGH CALCIUM
  • 🎗️ Cancer — bone metastasis and tumors that release a PTH-like hormone
  • 🛏️ Immobility — bed rest pulls calcium out of the bone into the blood
  • 💊 Thiazide diuretics, excess calcium or vitamin D supplements

Manifestations (S/S)

  • 1️⃣ KIDNEY STONES — “moans & groans” (renal calculi), flank pain, polyuria & thirst
  • 2️⃣ CONSTIPATION, hypoactive bowel sounds, nausea, anorexia
  • 3️⃣ BONE PAIN, pathologic fractures
  • 4️⃣ SEVERE MUSCLE WEAKNESS & LETHARGY, decreased DTR, confusion, stupor
  • 🫀 Short QT, bradycardia, heart block, digoxin toxicity risk
🧠 “Stones, Bones, Groans & psychiatric Moans.” Kidney stones · bone pain · abdominal groans (constipation) · confused moans. Four words = the entire hypercalcemia list.

👀 The two named signs of low calcium — draw them once, keep them forever

1️⃣ TROUSSEAU'S SIGN “twerking arm when the BP cuff goes on” BP CUFF CARPAL SPASM hand claws up ✋ Inflate the cuff above systolic 1–4 min → TETANY: muscle spasms all over 2️⃣ CHVOSTEK'S SIGN “cheek smile when stroking the face” tap here facial nerve, in front of the ear → cheek & lip TWITCH upward 😬

Both signs positive = hypocalcemia until proven otherwise — and after a thyroidectomy they are the signs you assess for every shift, because the parathyroids sit right there.

🧠 “CHeek = CHvostek · Cuff = Trousseau.” Match the first letters and you will never swap them on an exam again.

🚨 EMERGENCY ORDER — calcium, both directions

📉 HYPOcalcemia

1
🫁 AIRWAY FIRST — laryngospasm is the emergency. Keep emergency airway equipment (and a tracheostomy tray after thyroidectomy) at the bedside; seizure precautions.
2
💉 IV CALCIUM GLUCONATE for severe/symptomatic — give slowly, on a pump, with continuous cardiac monitoring. Watch the IV site: calcium is a vesicant.
3
💊 Oral calcium + vitamin D for chronic replacement (vitamin D is required for absorption).
4
🧲 Check the magnesium — low Mg causes stubborn low Ca.
5
⚠️ Digoxin caution — IV calcium plus digoxin increases the risk of toxicity and dysrhythmias.

📈 HYPERcalcemia

1
💧 IV 0.9% normal saline FIRST — rehydrate and dilute; it also flushes calcium out through the kidney.
2
💊 Loop diuretic (furosemide) after volume is restored — it wastes calcium. Never a thiazide — thiazides RAISE calcium.
3
💉 Calcitonin for a fast drop; bisphosphonates for the sustained drop (especially cancer-related).
4
🚶 MOBILIZE the client — weight-bearing pulls calcium back into bone. Stop calcium & vitamin D supplements.
5
🩺 Dialysis for severe or refractory levels. Strain urine & push fluids — kidney stone risk.
🧠 “Low Ca? Give it. High Ca? Flush it and walk it off.” Saline + furosemide + movement, and never a thiazide.
🔁

PHOSPHATE · PO₄³⁻

STEP 4 · CALCIUM'S MIRROR

You already know phosphate — it is whatever calcium is NOT.

🧪 Phosphate value scale

NORMAL 3.0 – 4.5 mg/dLCRITICAL <1.0 or >8.0
🔁 PHOSPHATE (PO₄³⁻) units: mg/dL · inverse to calcium 3.0–4.5 <1.0 CRIT LOW 1.0–2.9 HYPOphosphatemia 3.0–4.5 NORMAL 4.6–8.0 HYPERphosphatemia >8.0 CRIT HIGH Read the calcium on the same lab panel — they should be pointing in opposite directions. Critical cutoffs vary by lab.
🧠 “3 to 4-and-a-half.” Phosphate lives in the low single digits — right next door to magnesium's numbers, so label them carefully.

🔁 The inverse rule — the whole section in two lines

  • Ca HIGH ⬆ = PHOSPHATE LOW ⬇
  • Ca LOW ⬇ = PHOSPHATE HIGH ⬆

So to read a phosphate level, flip it and read the calcium symptoms. Phosphate also builds bone/teeth, makes ATP energy, and is part of every cell membrane.

🧠 “Ca and PO₄ never party together.” One goes up, the other leaves. If both are high on your lab sheet, look for a lab error or a very sick kidney.

📉 HYPOphosphatemia — below 3.0 · THINK HIGH-CALCIUM SIGNS

Manifestations — because calcium rises when phosphate falls:

  • 1️⃣ Kidney stones, moans & groans (renal calculi)
  • 2️⃣ CONSTIPATION
  • 3️⃣ BONE PAIN
  • 4️⃣ Severe muscle weakness & lethargy
  • ➕ Phosphate's own signs: respiratory muscle weakness (no ATP to breathe with), confusion, irritability, rhabdomyolysis, easy bleeding

Causes

  • 🦋 Hyperparathyroidism → HIGH PTH = HIGH CALCIUM (so phosphate is dumped)
  • 🧬 Genetics — inherited phosphate-wasting disorders
  • 🎗️ Cancer
  • 🍽️ Refeeding syndrome after starvation, alcoholism, malabsorption, phosphate-binding antacids, DKA treatment
🧠 “Low phos = high Ca costume.” Same four symptoms as hypercalcemia — stones, bones, groans, moans — just wearing a phosphate name tag.

📈 HYPERphosphatemia — over 4.5 · THINK LOW-CALCIUM SIGNS

Manifestations — because calcium falls when phosphate rises:

  • 1️⃣ Trousseau's sign & TETANY
  • 2️⃣ Chvostek's sign
  • 3️⃣ Weak B's — weak bones, weak blood clotting, weak beats
  • ➕ Numbness/tingling around the mouth & fingertips, muscle cramps, itching from calcium-phosphate deposits in the skin

Causes

  • 🫘 RENAL FAILURE TEST TIP Chronic kidney disease (CKD) — the classic cause
  • 🦋 Hypoparathyroidism → LOW PTH = LOW CALCIUM
  • 💥 Tumor lysis syndrome, rhabdomyolysis, excessive phosphate laxatives/enemas or vitamin D
🧠 “High phos = low Ca costume.” Tetany, Trousseau's, Chvostek's, weak B's — the hypocalcemia list under a different name.

⚖️ The calcium–phosphate seesaw (with PTH sitting on calcium's end)

⚖️ Ca²⁺ and PO₄³⁻ ALWAYS move opposite 🦋 HIGH PTH — hyperparathyroidism also: cancer · immobility Ca²⁺ HIGH PO₄³⁻ LOW Stones · Bones · Groans · Moans 🫘 RENAL FAILURE / LOW PTH CKD · hypoparathyroidism · thyroidectomy Ca²⁺ LOW PO₄³⁻ HIGH Trousseau's · Chvostek's · Tetany
🧠 “The kidney is the phosphate drain.” Plug the drain (renal failure) → phosphate backs up → calcium goes down → the client twitches. One sentence covers the whole CKD electrolyte picture.

🩺 EMERGENCY ORDER — phosphate, both directions

📉 HYPOphosphatemia

1
🫁 Watch the breathing — phosphate makes ATP; without it the respiratory muscles tire. Monitor RR, depth and O₂ sat.
2
🍖 Oral replacement + high-phosphate foods: dairy, meat, fish, eggs, nuts, whole grains, cola-type beverages.
3
💉 IV phosphate for severe/symptomatic — give slowly; it can crash the calcium and cause tetany.
4
🛑 Stop phosphate-binding antacids; watch closely for refeeding syndrome when restarting nutrition after starvation.
5
🩸 Monitor for bleeding & infection — low phosphate impairs platelets and white cells. Fall precautions for weakness.

📈 HYPERphosphatemia

1
💊 PHOSPHATE BINDERS WITH MEALS — calcium acetate, calcium carbonate, sevelamer. Timing is the test question: give them WITH food, not between meals.
2
🥛 Low-phosphate diet — limit dairy, processed foods, organ meats, nuts, colas.
3
🧪 Treat the low calcium that comes with it — assess for Trousseau's, Chvostek's and tetany; seizure & airway precautions.
4
🫧 Manage the itching — cool cloths, moisturizer, short nails; it comes from calcium-phosphate deposits.
5
🩺 DIALYSIS — the definitive answer in renal failure. Never give phosphate-containing laxatives or enemas to a client in renal failure.
🧠 “Binders eat the phosphate on the plate.” A binder only works if it is in the stomach with the food — that is why it is given with meals.
⚡

QUICK RECALL

SAY IT OUT LOUD
🚨 Mag toxicitySTOP the drip → IV CALCIUM GLUCONATE. Triggers: DTR gone, RR < 12, urine < 30 mL/hr.
🧲 Low Mg = TorsadesExcited body: hyperreflexia, diarrhea, Torsades de Pointes → give magnesium sulfate.
🦴 Low Ca = T then CTrousseau's (cuff/claw) & Chvostek's (cheek) + tetany + weak Bones/Blood/Beats.
🔁 Phosphate = flip itLow PO₄ → read high calcium signs · High PO₄ → read low calcium signs. Binders with meals.

🧾 One-screen number sheet

ElectrolyteNormal (adult)LOW looks likeHIGH looks like
Magnesium Mg²⁺1.3 – 2.1 mEq/LExcited: ↑DTR, diarrhea, Torsades, seizuresSedated: ↓DTR, ↓RR, hypoactive gut, heart block
Calcium Ca²⁺9.0 – 10.5 mg/dLExcited: Trousseau's, Chvostek's, tetany, weak B's, diarrheaSluggish: stones, constipation, bone pain, weakness
Phosphate PO₄³⁻3.0 – 4.5 mg/dL= HIGH calcium picture= LOW calcium picture

REMEMBER Magnesium Mellows the muscles · Calcium Contracts the muscles · Phosphate is calcium's oPposite.

🎯 Cover & check — 8 rapid-fire questions
Q1: A client on a magnesium sulfate infusion has absent patellar reflexes and a respiratory rate of 10. What do you do FIRST, and what is the antidote?
STOP the magnesium infusion first, then give IV calcium gluconate — the antidote — with continuous cardiac monitoring and airway support ready.
Q2: What is the EARLIEST sign of magnesium toxicity?
Loss of deep tendon reflexes (hyporeflexia) — it shows up before the respiratory depression and long before the heart block.
Q3: The monitor shows Torsades de Pointes. Which electrolyte and which drug?
Magnesium — low magnesium causes it, and IV magnesium sulfate treats it. TOP TESTED.
Q4: Name the two classic signs of hypocalcemia and how you elicit each.
Trousseau's — inflate a BP cuff above systolic for 1–4 minutes and the hand claws into carpal spasm. Chvostek's — tap the facial nerve in front of the ear and the cheek and lip twitch.
Q5: Why does chronic kidney disease cause low calcium?
The failing kidney cannot excrete phosphate, so phosphate rises — and because calcium and phosphate are inverse, calcium falls. The kidney also can't activate vitamin D.
Q6: A client has hypercalcemia at 12.8. Which diuretic is correct and which is contraindicated?
Give a loop diuretic (furosemide) after IV normal saline rehydration. Never a thiazide — thiazides RAISE calcium.
Q7: When are phosphate binders given?
WITH meals. They bind the phosphate in the food so it never gets absorbed — between meals they do nothing.
Q8: A client's potassium keeps returning low despite replacement. What do you check?
The magnesium. Potassium will not correct until the magnesium is corrected.