🏠 Study Hub 🖼️ Infographics
Nursing Field Notes / Renal & Fluid · Assessment & Monitoring
💧 FLUID BALANCE SET I · NG-054 Compartments & controls II · NG-055 Losses & shifts III · NG-059 Measure & monitor

Fluid Balance III ⚖️

Measure it, monitor it, and know the number that means CALL

NG-059 RENAL + FLUID · ASSESSMENT ADHD-friendly visual edition

What this page covers, and what it doesn't. NG-054 is the compartments and the hormones. NG-055 is why fluid is lost and where it shifts. This page is the toolkit — the seven measurements you actually take at the bedside, what each number means, and the exact threshold that turns a finding into a phone call. For the head-to-toe symptom picture of each disorder go to NG-207 · FVO vs FVD, NG-169 · Overload and NG-191 · Deficit.

📄 Simple Nursing original — opens in Drive →

⚖️ 1 L = 1 kg = 2.2 lbReport 2–3 lb in a day or 5 lb in a week.
🚽 30 mL/hrOr 0.5 mL/kg/hr. Below that for 2 hours → report it.
🧪 Dilute LOW, dry HIGHHct · BUN · osmolality · specific gravity all move with the concentration.
📈 Trend beats snapshotOne odd number is data. Three moving together is a trend — escalate that.
⚖️

THE SCALE — YOUR BEST INSTRUMENT

STEP 1

Daily weight beats every other measure, because it catches the fluid the I&O sheet never sees.

⭐ Weight IS water — the one conversion you need

THE SCALE IS THE BEST FLUID MONITOR YOU HAVEWeight change over 24 hours is almost entirely WATER. Muscle and fat do not move that fast.72.4 kgSAME scale · SAME time of daySAME clothing · after voidingTHE ONLY CONVERSION YOU NEED1 liter of fluid↓= 1 kilogram↓= 2.2 poundsSo a 2 kg overnight gain = about 2 liters retained.HOW MUCH CHANGE MATTERSunder 1 lb / daynormal day-to-dayvariation2–3 lb in ONE dayREPORT IT · about1–1.5 L5 lb in ONE weekREPORT IT · about2.3 L2 lb/day for 3 daysescalate — atrend beats one number⚠ Weight UP while blood pressure DOWN = third spacing, not overload.
🧠 “A liter is a kilo is 2.2 pounds.” Say it once. It converts every fluid question you will ever get.

✅ How to weigh so the number means something

1
Same scale every time — scales disagree with each other by more than the change you are looking for.
2
Same time of day, ideally early morning.
3
After voiding, before breakfast.
4
Same clothing — no shoes, no heavy blankets, no equipment on the bed scale.
5
Document immediately and compare with yesterday, not with admission.
🧠 “Same scale, same time, same clothes, empty bladder.” Four sames.

🚨 The numbers that get reported

CHANGEMEANS ABOUTACTION
Under 1 lb in a day<0.5 LNormal variation — document
2–3 lb in ONE day≈1–1.5 LReport it
5 lb in ONE week≈2.3 LReport it
2 lb/day for 3 days≈3 L accumulatingEscalate — this is a trend

A gain is retained fluid until proven otherwise. A loss is lost fluid until proven otherwise. Real tissue does not change that fast.

🧠 “Two-to-three in a day, five in a week.” Those two numbers get you the exam point.

⚠️ When the scale and the I&O disagree

They disagree constantly, and the scale usually wins. Reasons:

  • Insensible losses are never charted — lungs, skin, sweat, fever.
  • Missed intake — the ice chips, the sips with medications, the family's soda.
  • Missed output — the incontinence pad, the emesis in the sink, the soaked dressing.
  • Third spacing — the fluid stays in the body, so the weight goes up even with a negative balance.
🧠 “The sheet can lie. The scale can't.” Fluid has mass, whichever compartment it is hiding in.

🧮 Worked example — do this once and it sticks

Yesterday 70.0 kg. This morning 72.2 kg. Intake and output charted as roughly even. Blood pressure has drifted from 128/76 to 104/62, pulse from 78 to 106, urine output 22 mL/hr.

  • Gain = 2.2 kg ≈ 2.2 L ≈ 4.8 lb. Definitely reportable.
  • But the BP is down and the pulse is up — the circulation is underfilled.
  • Weight up + circulation down = third spacing, not simple overload.

Never reach for a diuretic on the weight gain alone — you would pull volume out of an already-empty vascular space. Report the full picture.

🧠 Weight tells you HOW MUCH. Vital signs tell you WHERE it is. You need both.
📋

INTAKE & OUTPUT — DOING IT PROPERLY

STEP 2

The I&O sheet is only as good as the least careful person who touched it this shift.

📋 What counts on each side

THE I&O SHEET · what actually countsIf it is liquid at room temperature, it counts. Ice chips count as about HALF their volume.INTAKE → IN🥤Oral fluidswater, juice, coffee, soup, jelly, ice cream💉IV fluidsmaintenance, boluses, blood products💊IV medicationsevery piggyback and every flush🍽️Tube feeds + flushesthe flushes add up fast🚿Irrigationcount only what does NOT come back outOUTPUT → OUT🚽Urinethe biggest and most useful number🤮Emesis / NG suctionmeasure it, do not estimate💩Liquid stoolformed stool is not measured🩹Drains & tubeschest tubes, JP, wound vac, ostomy🩸Blood lossweigh dressings if you have toNEVER ON THE SHEET — insensible lossesWater vapor from the lungs · evaporation from the skin · sweat you did not see · fever · tachypnoea · open wounds and burns★ THIS is why the I&O sheet and the scale disagree — and why the SCALE wins.A patient can run an “even” I&O and still be liters behind.
🧠 “Liquid at room temperature counts.” Jelly, ice cream and popsicles are fluids. Ice chips count as roughly half their volume.

✅ Reading the balance

POSITIVE balanceIn > Out. Fluid is accumulating. Expect the weight to rise.
NEGATIVE balanceOut > In. Fluid is being lost. Expect the weight to fall.

Then check whether the weight actually did what you predicted. If it did not, something is missing from the sheet — or fluid is third spacing.

🧠 Predict, then check. The mismatch is the finding, not the error.

⚠️ The five most commonly missed entries

  • IV medication volumes — every piggyback bag and every flush.
  • Tube-feed flushes — small, frequent, and they add up to hundreds of milliliters a day.
  • Incontinence — weigh the pad if your unit does that (1 g ≈ 1 mL).
  • Bowel prep and diarrhea — huge volumes, rarely measured.
  • Irrigation — only the amount that does not return counts as intake.
🧠 “Flushes are fluids.” The one nobody charts.

📏 Totals, shifts and the 24-hour picture

  • Total at the end of every shift, not at the end of the day — a running total catches problems earlier.
  • Report the 24-hour balance alongside the weight change, so they can be compared.
  • A patient on strict I&O needs every container measured, not eyeballed. Use a graduate.
  • Communicate the running total at handover — the next nurse cannot recreate it.
🧠 “Total at the end of every shift.” Eight hours of drift is easier to fix than 24.

🧾 A normal adult day, for comparison

IN≈ mLOUT≈ mL
Drinks1200–1500Urine1500
Water in food700–1000Skin (insensible + sweat)500–600
Metabolic water200–300Lungs (vapor)300–400
Faeces100–200
TOTAL≈2500TOTAL≈2500

Figures are typical adult approximations and vary with body size, diet, activity and climate.

🧠 “2500 in, 2500 out.” Roughly half the output is urine you can actually measure.
🚽

WHAT THE URINE IS TELLING YOU

STEP 3

Volume answers “are the kidneys being perfused?”. Concentration answers “is the body holding on?”.

🚽 Output — the numbers that trigger a call

URINE OUTPUT · the fastest perfusion check at the bedsideIf the kidneys are making urine, they are being perfused. It is that direct.kidney → ureterhourly urine meter≥ 30 mL/houror ≥ 0.5 mL/kg/hourADEQUATE — the kidneys are perfused< 30 mL/hourfor 2 hours in a rowREPORT IT — investigate volume, BP and the catheter< 400 mL/dayoliguria⚠ kidney injury or serious volume depletion< 100 mL/dayanuria⚠ emergency — escalate immediately★ DO THE MATH: 0.5 mL/kg/hr on a 70 kg adult = 35 mL/hour = about 840 mL/day. On a 50 kg adult it is only 25 mL/hour.⚠ No urine at all? Check the CATHETER for kinks or clots before you call it anuria.
🧠 “Thirty an hour, half a mil a kilo.” Two ways of saying the same threshold — and the per-kilogram one is the safer answer on an exam.

🔬 Concentration — specific gravity and color

URINE TELLS YOU IN TEN SECONDSSpecific gravity = how concentrated the urine is compared with plain water (1.000).urinometer float1.000 · plain water1.005 · low end of normal1.0101.0201.030 · high end of normalover 1.030 · very concentratedSPECIFIC GRAVITYWHICH WAY DOES IT MOVE?LOW gravity (dilute) → too much waterHIGH gravity (concentrated) → DRYCOLOR LADDERalmost clearover-hydrated / diuresingpale strawwell hydratedyellownormaldark yellowstart drinkingamberdehydratedbrown-ambervery dry · assess now⚠ Specific gravity is falsely HIGH with glucose, protein or contrast dye in the urine, and falsely LOW in kidney disease,diabetes insipidus and after diuretics — the kidney has lost the ability to concentrate at all. Never read it alone.
🧠 “Low when Liquidy, High when Dry.” Dilute urine = too much water. Concentrated urine = not enough.

🧪 What specific gravity actually is

The weight of the urine compared with the weight of plain water. Water is 1.000; typical urine runs 1.005–1.030.

  • Above 1.030 — very concentrated. The kidney is conserving water hard. Think deficit.
  • Below 1.005 — very dilute. Too much water on board, or the kidney has lost the ability to concentrate.
  • Stuck around 1.010 regardless of hydration — “fixed” specific gravity, a red flag for kidney disease.
GO DEEPER NG-269 · Urinalysis
🧠 Water is 1.000, so anything above it is “stuff dissolved in it”.

⚠️ When specific gravity lies to you

FALSELY HIGHFALSELY LOW / UNRELIABLE
Glucose in the urineChronic kidney disease (cannot concentrate)
Protein in the urineDiabetes insipidus
IV contrast dyeRecent diuretic dose
Some IV colloid solutionsVery high fluid intake just before the sample

Never diagnose fluid status from a single specific gravity.

🧠 Anything dissolved makes it heavier. Sugar and protein fake dehydration.

🚨 Oliguria — think in three buckets

Low urine output has three possible causes and you check them in this order:

1
Mechanical. Is the catheter kinked, clamped, obstructed or lying under the patient? Is the patient in retention? Bladder scan.
2
Pre-renal. Is there enough volume and pressure reaching the kidney? Check BP, pulse, weight, recent losses.
3
Renal / post-renal. Is the kidney itself injured, or is there obstruction above the bladder? Check creatinine, BUN, nephrotoxic drugs.
GO DEEPER NG-047 · Acute vs chronic renal failure
🧠 “Tube, tank, tissue.” Check the tube, then the tank, then the tissue.

🎨 Color is a screening tool, not a diagnosis

  • Very pale / clear — dilute. Overload, diuresis, or DI.
  • Dark amber — concentrated. Deficit, unless something is coloring it.
  • Cloudy with odor — think infection, not fluid status.
  • Tea/cola colored — think blood, myoglobin or bile. Escalate.

B vitamins turn urine bright yellow; some drugs and beetroot turn it orange or red. Ask before you panic.

🧠 “Color screens, gravity measures, volume decides.”
🧪

THE LAB PANEL — DILUTE OR CONCENTRATED?

STEP 4

One rule runs this whole section: the values move with the WATER, not with the substance.

📊 Every value, both directions

THE LAB PANEL · dilute reads LOW, concentrated reads HIGHMost of these values do not change because the substance changed — they change because the WATER did.← FLUID OVERLOAD · DILUTENORMALFLUID DEFICIT · CONCENTRATED →Hematocrittypical M 42–52% · F 37–47%LOWNORMALHIGHFVO → LOWFVD → HIGHBUNtypical 10–20 mg/dLLOWNORMALHIGHFVO → LOWFVD → HIGHSerum osmolalitytypical 275–295 mOsm/kgLOWNORMALHIGHFVO → LOWFVD → HIGHUrine specific gravity1.005–1.030LOWNORMALHIGHFVO → LOW · diluteFVD → HIGH · concentratedSerum sodium135–145 mEq/LLOWNORMALHIGHFVO → LOW if water excessFVD → HIGH if water lossAlbumin3.5–5.0 g/dLLOWNORMALHIGHFVO → LOW · and often the CAUSEFVD → may read high if very dry★ ONE EXCEPTION: in HEMORRHAGE red cells are lost too, so hematocrit and hemoglobin FALL instead of rising.
🧠 “LOW when Liquidy · HIGH when Dry.” Say it out loud once for each row of the table.

🧪 BUN and the BUN : creatinine ratio

BUN (typical 10–20 mg/dL) rises when the kidney is under-perfused, because slow-moving filtrate lets more urea be reabsorbed. Creatinine (typical 0.6–1.2 mg/dL) is much steadier.

  • BUN up, creatinine normal, ratio above roughly 20:1 → pre-renal: dehydration, low output, GI bleed, high protein load.
  • Both up together, ratio near 10:1 → intrinsic kidney damage.

Ranges vary by laboratory — always read the range printed on the report.

🧠 “BUN runs ahead when the tank is low.” A lonely high BUN is usually a fluid problem.

🩸 Hematocrit — the exception you will be tested on

Hematocrit is the percentage of blood that is red cells. It rises when the plasma shrinks even though no new red cells were made.

DehydrationPlasma down, cells the same → Hct HIGH (hemoconcentration).
OverloadPlasma up, cells the same → Hct LOW (hemodilution).

But in HEMORRHAGE the patient loses plasma AND cells — so Hct and hemoglobin FALL. That is why a normal Hct early in a bleed is falsely reassuring.

🧠 “Dry blood looks rich. Bleeding blood looks poor.”

🧂 Sodium — the trickiest one on the panel

Sodium (typical 135–145 mEq/L) is a concentration, not an amount. It tells you the ratio of sodium to water, so it can be abnormal from either side.

  • Low sodium can mean too little sodium or too much water.
  • High sodium can mean too much sodium or too little water — and water loss is far more common.
  • Normal sodium does not rule out a large isotonic fluid deficit.

Both directions put the brain at risk, because brain cells swell or shrink with the shift.

LINK NG-088 · Potassium, sodium & chloride
🧠 “Sodium is a ratio, not a total.” Always ask what the WATER is doing.

📈 Read three results, not one

A single lab value is a photograph. Fluid status is a film.

  • Pull up the last three of every value and look at the direction.
  • Line the labs up against the weights and the I&O for the same days.
  • If Hct, BUN, osmolality and specific gravity are all rising together, the patient is drying out — no single value needed to be dramatic.
🧠 Three numbers moving the same way is a trend. Trends are what you hand over and escalate.

🧾 Which labs to expect ordered

  • Basic metabolic panel — sodium, potassium, chloride, bicarbonate, BUN, creatinine, glucose.
  • Serum osmolality — the direct measure of concentration.
  • Urine specific gravity and urine osmolality — what the kidney is doing about it.
  • Hematocrit and hemoglobin — concentration, plus a bleeding check.
  • Albumin — the oncotic pull; low albumin explains a lot of edema.
LINK NG-227 · Vitamins & electrolytes · NG-134 · Mag, calcium, phosphate
🧠 Magnesium 1.3–2.1 mEq/L · calcium 9.0–10.5 mg/dL · albumin 3.5–5.0 g/dL. Ranges vary by lab.
🖐️

HANDS-ON ASSESSMENT

STEP 5

Everything in this section is free, takes under a minute, and gets tested in clinical.

🫀 Neck veins and CVP

NECK VEINS · a free look at the right atrial pressureHead of bed at 30–45°, head turned slightly AWAY, tangential light. Same position every time.DISTENDED → FLUID OVERLOADsternal angle = zerocolumnrises HIGH30–45°head of bedVein visibly full and pulsating well above the sternal angle.FLAT · COLLAPSED → FLUID DEFICITsternal angle = zerobarelyvisible30–45°head of bedVeins flat even lying down — the tank is empty.CVP — the same information, measured with a central lineTypical adult CVP is about 2–6 mmHg (varies by reference). LOW → underfilled. HIGH → overloaded or a failing right heart.⚠ JVD is not always overload — it also appears in right heart failure, cardiac tamponade and tension pneumothorax.
🧠 “Full veins, full tank. Flat veins, flat tank.” Just remember to position the bed the same way every single time, or you are comparing two different tests.

📉 Orthostatic vital signs

ORTHOSTATIC VITAL SIGNS · the bedside volume testMeasure lying, then sitting, then standing — waiting 1–3 minutes after each change of position.1 · LYINGBP126/78HR762 · SITTINGBP112/70HR943 · STANDINGBP98/60HR112POSITIVE if SYSTOLIC drops ≥20 mmHg, or DIASTOLIC drops ≥10 mmHg, within 3 minutes of standingA pulse rise of about 20 beats/min, or dizziness on standing, supports the finding.⚠ FALL RISK — stay with the patient throughout, and sit them straight back down if they feel faint.
🧠 “Twenty over ten.” Systolic down 20, or diastolic down 10 — that is a positive test.

🖐️ Turgor, membranes and capillary refill

THREE THINGS YOUR HANDS CAN MEASURENo equipment, ten seconds, and they are on every skills check-off you will ever take.1 · SKIN TURGOR — pinch and let goNORMALstays upTENTING → DRYTest over the STERNUM, forehead or under the clavicle in older adults —the back of the hand tents in everyone over about 60 and tells you nothing.Normal: skin snaps back immediately. Dry: it stays tented for seconds.2 · MUCOUS MEMBRANES — look in the mouthMOIST · normalDRY & STICKYCheck between cheek and gum, and look for a dry furrowed tongue.3 · CAPILLARY REFILL — press and countunder 3 secover 3 sec → poor perfusionSome references use 2 seconds. Cold hands read falsely slow.★ None of these is reliable on its own. Put them together with the weight, the urine output and the vital sign trend.Poor turgor is especially unreliable in older adults, in very thin patients, and in anyone who has lost weight quickly.⚠ Turgor tells you about the INTERSTITIAL space. A patient can have good turgor and still be intravascularly dry.
🧠 “Sternum, not the hand.” The back of an older adult's hand always tents.

🫁 Lung sounds — the measurement that catches overload first

  • Listen to the bases first and posteriorly — fluid settles with gravity.
  • New fine crackles that do not clear with coughing are the earliest lung sign of overload.
  • Add respiratory rate, work of breathing and oxygen saturation to the picture.
  • Pink frothy sputum with severe breathlessness is pulmonary edema — an emergency.

Never leave a patient flat when they are developing crackles — sit them up.

🧠 “Crackles at the bases = the tide is coming in.”

🧠 Mental status — an early sign in BOTH directions

OVERLOADSodium falls as blood is diluted → brain cells swell → headache, confusion, seizures.
DEFICITPoor cerebral perfusion, sodium rises → restlessness, then confusion and lethargy.

Compare with the previous shift, not with your idea of normal. Family saying “that's not like her” is assessment data.

🧠 Restless comes before unresponsive. New agitation is a perfusion problem until proven otherwise.

🖐️ Edema — quick recap

Press firmly over a bony prominence for several seconds; the depth and duration of the pit is the grade, commonly recorded as 1+ to 4+.

  • Dependent edema collects wherever gravity takes it — ankles when up, sacrum when in bed. Check the sacrum on every bedbound patient.
  • Periorbital puffiness is often the earliest visible site, especially in the morning.
  • Edema is a late sign — several liters are usually retained before pitting appears.
FULL GRADING SCALE NG-169 · Fluid overload has the 0+ to 4+ chart in detail.
🧠 “Gravity picks the puddle.” Up and walking → ankles. Lying in bed → sacrum.
🚨

WHEN THE NUMBERS SAY ACT

STEP 6

Measuring is only useful if you know which number picks up the phone.

🎛️ The dashboard — six tiles, every shift

THE MONITORING DASHBOARD · six numbers, every shiftOne glance. If any tile is in the red column, you are picking up the phone.⚖️DAILY WEIGHTsame scale, same timeCALL IF2–3 lb in a day · 5lb in a week🚽URINE OUTPUThourly if catheterizedCALL IFunder 30 mL/hr for 2 hours🫀BP & PULSEtrend, not a snapshotCALL IFHR climbing · SBP falling· orthostatic drop🫁LUNG SOUNDSlisten to the basesCALL IFnew crackles · newshortness of breath🧠MENTAL STATUScompare with last shiftCALL IFnew confusion, restlessness orlethargy🧪LAB TRENDread the last three, not oneCALL IFNa, Hct, BUN, osmolality allmoving together★ A single abnormal number is data. THREE moving the same way is a trend — and a trend is what you escalate.
🧠 Photograph this one. It is the whole page compressed into six boxes.

🚨 Escalate NOW for any of these

  • Urine output under 30 mL/hr for two consecutive hours, with a patent catheter.
  • New crackles, new breathlessness, or a falling oxygen saturation.
  • Systolic BP falling with a rising pulse — compensation is running out.
  • New confusion, restlessness or a drop in level of consciousness.
  • Weight change of 2–3 lb in a day or 5 lb in a week.
  • Sodium outside 135–145 mEq/L with any neurological change.
🧠 Breathing · pressure · pee · brain. Four things that make you call.

📞 How to hand it over — SBAR in fluid language

S
Situation. “Mrs L in 412 has gained 2.2 kg overnight and her urine output is 22 mL/hr.”
B
Background. “Day 3 post-op, on IV fluids at 125 mL/hr, history of heart failure.”
A
Assessment. “BP down from 128/76 to 104/62, pulse up from 78 to 106, new crackles at both bases.”
R
Recommendation. “I think she is third spacing. Can you review the fluid order and would you like labs?”
🧠 Give the trend, not the snapshot. “Up from” and “down from” are the words that get action.

⭐ The one-line summary of all three pages

NG-054 — WHERE the water lives and what controls it
▼
NG-055 — WHY it leaves and where it shifts to
▼
NG-059 — HOW you measure it and when you call

Then apply it to a patient using NG-207 · FVO vs FVD.

🧠 Three pages, three verbs: WHERE · WHY · HOW.

🎓 Quick-fire self test

Q. A patient gains 2 kg overnight. About how much fluid is that?
▸ About 2 liters. 1 kg = 1 L = 2.2 lb.
Q. Minimum acceptable adult urine output?
▸ 30 mL/hr, or 0.5 mL/kg/hr.
Q. Urine specific gravity is 1.032. Fluid overload or deficit?
▸ Deficit — the urine is concentrated, so the body is conserving water. (Rule out glucose, protein and contrast first.)
Q. Which lab moves the OPPOSITE way to the others in hemorrhage?
▸ Hematocrit and hemoglobin FALL, because red cells are lost along with the plasma.
Q. BP drops from 124/74 lying to 100/66 standing. Positive orthostatic test?
▸ Yes — systolic fell 24 mmHg, which is ≥20. Keep the patient safe; this is a fall risk.
Q. Where do you test skin turgor in an 84-year-old?
▸ Over the sternum, forehead or below the clavicle — never the back of the hand.
Q. Weight is UP 2 kg but BP is down and pulse is up. What is happening?
▸ Third spacing. The fluid is in the body but not in the vessels. Report the whole picture; do not assume a diuretic is the answer.
Q. Which measurement catches fluid change that the I&O sheet misses entirely?
▸ The daily weight — because insensible losses are never charted.
🧠 Eight right without looking = you can monitor fluid balance on any unit.
⚖️ The scale1 L = 1 kg = 2.2 lb. Report 2–3 lb/day or 5 lb/week. Same scale, same time, same clothes, empty bladder.
🚽 The urine30 mL/hr or 0.5 mL/kg/hr. Specific gravity 1.005–1.030: low = liquidy, high = dry.
🧪 The labsHct · BUN · osmolality · specific gravity all read HIGH when dry, LOW when diluted — except in hemorrhage.
🖐️ The handsNeck veins · orthostatics (20/10) · turgor at the sternum · crackles at the bases · mental status vs last shift.