Read the pH: below 7.35 is acidosis, above 7.45 alkalosis.
Find the value that explains it: PaCO₂ moving opposite to the pH is respiratory, HCO₃⁻ moving with the pH is metabolic.
Look at the other value: normal means uncompensated, abnormal in the compensating direction means partial compensation, and a normal pH with both abnormal means full compensation.
In a metabolic acidosis, compare PaCO₂ with Winter’s formula, 1.5·HCO₃⁻ + 8 ± 2, and calculate the anion gap Na⁺ − (Cl⁻ + HCO₃⁻).
Check a high anion gap with the delta ratio and, when albumin is low, with the corrected gap.
Write down what is asked: a pump rate, a volume, kilocalories, grams of protein or water.
Turn energy into volume with mL = kcal/(kcal/mL), and volume into protein with litres × g/L.
Divide by the hours the feed actually runs for a rate, or by the number of feeds for a bolus.
For needs, multiply kcal/kg or g/kg by the weight the rule names; find the ideal body weight with Devine: 50 or 45.5 + 2.3 × (inches − 60).
For PN, find grams as % × mL/100, then use 3.4 kcal/g for dextrose, 4 kcal/g for amino acids and the stated kcal/mL for lipid.
ECG rhythm strip interpretation
Paper (25 mm/s, 10 mm/mV)
1 small box = 0.04 s, 1 large box = 0.20 s, 10 mm = 1 mV
Heart rate, regular rhythm
300 ÷ large boxes = 1500 ÷ small boxes = 60 ÷ RR (s)
Heart rate, irregular rhythm
QRS complexes in 6 s × 10
Normal PR interval
0.12–0.20 s
Normal QRS duration
< 0.12 s
QTc (Bazett)
QT/√RR
QTc (Fridericia)
QT/∛RR
QTc (Framingham)
QT + 154·(1 − RR)
Sinus rates
bradycardia < 60, normal 60–100, tachycardia > 100 /min
Escape rates
junctional 40–60, ventricular 20–40 /min
Fast rhythms
SVT 150–250 /min (narrow), VT > 100 /min (wide)
Method
Rate: for a regular rhythm divide 300 by the large boxes or 1500 by the small boxes between two R waves; for an irregular rhythm count the QRS complexes in 6 seconds and multiply by 10.
Rhythm: compare the R–R intervals. Equal is regular; a repeating pattern is regularly irregular; no pattern at all is irregularly irregular.
P waves: is there an upright P wave in lead II before every QRS, all alike? Look for fibrillatory or sawtooth waves, inverted P waves and P waves without a QRS.
PR interval: from the start of P to the start of the QRS, normally 0.12–0.20 s and constant. Watch whether it lengthens, stays fixed before a dropped beat, or varies at random.
QRS duration: below 0.12 s is narrow; 0.12 s or more is wide. Then name the rhythm, and for the QT use QTc = QT/√RR (Bazett) with times in seconds.
Prioritization & delegation
Method
Ask what will harm the patient soonest if nothing is done.
Apply ABC (C-A-B in cardiac arrest), then Maslow: physiological needs before safety, safety before psychological needs.
Compare the options: acute before chronic, unstable before stable, unexpected before expected, systemic before local, and check each finding against the patient’s baseline.
Assess before you act unless it is an emergency; then choose the step the others depend on.
For delegation, check the five rights: task, circumstance, person, directions and supervision. Assessment, teaching and evaluation stay with the RN.
Infection control & patient safety
Method
Start with standard precautions for every patient: hand hygiene, PPE for the expected exposure, safe sharps.
Keep sterile items sterile: if in doubt, it is not sterile; replace, never wipe.
Prevent harm in the environment: fall measures, restraints only as a last resort, RACE and PASS for fire.
Check the rights of medication administration, two identifiers and extra safeguards for high-alert drugs; report errors and near misses.
Lab values & electrolytes
Method
Compare the value with the laboratory’s own reference range, then with the patient’s baseline and trend.
Check the sample: hemolysis, a delay, or blood drawn near an IV can give false results.
Link the value to its typical signs and to the drugs and conditions that cause it.
Look for interactions: low potassium or magnesium increases digoxin toxicity; dehydration raises lithium.
Act on the patient: assess, hold a drug if the level is unsafe, read back critical values and inform the prescriber.
2Practice problems
1.Nursing fundamentalsMedium
How should the ear be positioned when taking a tympanic temperature in an adult?
ALeave the ear alone and insert the probe deeply
BPush the outer ear forward against the cheek
CGently pull the outer ear up and back
DGently pull the outer ear down and back
2.Nursing fundamentalsHard
An older patient with diarrhoea for three days is dizzy on standing and passing small amounts of dark urine. What is the most likely problem?
ADehydration from fluid loss
BUrinary retention caused by a full bladder
CNormal ageing that needs no action
DFluid overload from drinking too much
3.Clinical nursingMedium
An arterial blood gas shows a low pH, a high PaCO2 and a normal bicarbonate. What does this show?
AMetabolic acidosis
BRespiratory acidosis
CMetabolic alkalosis
DRespiratory alkalosis
4.Clinical nursingHard
Why is morphine more likely to cause toxicity in a patient with severe kidney impairment?
AKidney disease makes the opioid receptors disappear
BThe kidneys normally activate morphine, so more of it becomes active
CKidney failure makes the stomach absorb more morphine
DIts active metabolites build up because the kidneys excrete them
5.Arterial blood gas interpretationMedium
Practice values: Na⁺ 140 mmol/L, glucose 6.9 mmol/L and urea 23.3 mmol/L. Calculate the serum osmolality Osm = 2·Na⁺ + glucose + urea to the nearest whole number.
Na⁺ 140 mmol/Lglucose 6.9 mmol/Lurea 23.3 mmol/L
Osm = mOsm/kg
6.Arterial blood gas interpretationHard
A practice gas shows a metabolic acidosis: pH 7.32, PaCO₂ 32 mmHg (4.3 kPa), HCO₃⁻ 16 mmol/L. Compare the measured PaCO₂ with Winter’s formula. Click your interpretation.
pH 7.32PaCO₂ 32 mmHg (4.3 kPa)HCO₃⁻ 16 mmol/L
1appropriate compensation
2added respiratory acidosis
3added respiratory alkalosis
7.Clinical assessment scoresMedium
Practice exercise (made-up values, not clinical guidance). A patient has a pulse of 71/min and a blood pressure of 107/64 mmHg. Find the shock index SI = HR/SBP. Round to two decimal places.
HR 71/minBP 107/64 mmHg
SI =
8.Clinical assessment scoresHard
Practice exercise (made-up values, not clinical guidance). Use the NEWS2 chart (SpO₂ scale 1) for these observations: respiration rate 16/min, SpO₂ 98% on room air, blood pressure 150/90 mmHg, pulse 58/min, alert, temperature 37.1 °C. Which clinical risk group does the patient fall into? Click it.
Practice exercise (made-up values, not clinical guidance). A woman is 176 cm tall and weighs 76 kg. Find the actual weight as a percentage of the ideal body weight, %IBW, using the Devine formula (1 in = 2.54 cm). Round to the nearest whole number.
Practice exercise (made-up values, not clinical guidance). Over 24 hours a patient receives 2000 mL of parenteral nutrition with final concentrations of 20% dextrose and 3.5% amino acids, plus 500 mL of 20% lipid emulsion (2 kcal/mL). Find the non-protein kilocalorie to nitrogen ratio NPC : N (the number x in x : 1). Round to the nearest whole number.
2000 mLdextrose 20%amino acids 3.5%lipid 500 mL · 2 kcal/mL
NPC : N =
11.ECG rhythm strip interpretationMedium
Interpret this lead II rhythm strip. Which rhythm is it? Click your answer.
lead II, 25 mm/s, 10 mm/mV1 small box = 0.04 s, 1 large box = 0.20 sstrip length 6 s
1junctional rhythm
2sinus bradycardia
3first-degree AV block
4sinus tachycardia
12.ECG rhythm strip interpretationHard
This lead II strip shows an AV block, so the atria and the ventricles beat at different rates. The QRS complexes are regular: find the ventricular rate in beats per minute (1500 method, whole number).
lead II, 25 mm/s, 10 mm/mV1 small box = 0.04 s, 1 large box = 0.20 sstrip length 6 s
ventricular rate = bpm
13.Prioritization & delegationMedium
A drowsy patient who has just returned from surgery starts to vomit. What should the nurse do first?
ATurn the patient onto their side
BGive an oral anti-sickness tablet
CGive a drink of water
DRaise the legs above the heart
14.Prioritization & delegationHard
An infant with pyloric stenosis has repeated projectile vomiting. Which acid-base imbalance is most likely?
AMetabolic alkalosis
BRespiratory alkalosis
CMetabolic acidosis
DRespiratory acidosis
15.Infection control & patient safetyMedium
A confused patient keeps pulling at an IV line. Which is a less restrictive option to consider before wrist restraints?
ATying both arms to the bed frame
BCovering the site with a sleeve or using hand mitts with supervision
CGiving a sedative every few hours
DUsing a vest restraint in the chair so that the patient’s hands stay down
16.Infection control & patient safetyHard
A patient has had MRSA in a wound and now needs a dressing change. Which PPE is appropriate?
AGown and gloves, plus eye protection and mask if splashes are likely
BSterile gloves only, with no gown or other protection
CNo PPE, if the hands are cleaned afterwards
DAn N95 respirator only, because MRSA is a resistant organism
17.Lab values & electrolytesMedium
Which instruction is correct for a patient taking an oral potassium chloride supplement?
ACrush the extended-release tablets and mix them with a little water if needed
BUse a salt substitute as well, so less of the tablet is needed each day
CTake it on an empty stomach with only a small sip of water to speed absorption
DTake it with food and a full glass of water, and do not crush extended-release tablets
18.Lab values & electrolytesHard
A patient with a long-standing lung condition has a serum bicarbonate of 32 mEq/L, an arterial PaCO₂ that is always high and a pH of 7.36. Which condition fits best?
ACOPD with chronic CO₂ retention and metabolic compensation
BAcute aspirin overdose with rapid breathing
CAcute diabetic ketoacidosis with severe dehydration and vomiting
DAcute severe diarrhea with large bicarbonate losses
3Solutions
1.Nursing fundamentals
Answer: C · Gently pull the outer ear up and back
Why this is the answer
Pulling the pinna up and back straightens the adult ear canal so the probe points at the eardrum. In young children the pinna is pulled down and back instead.
Answer
C · Gently pull the outer ear up and back
2.Nursing fundamentals
Answer: A · Dehydration from fluid loss
Why this is the answer
Diarrhoea causes loss of water and electrolytes. Postural dizziness and concentrated low-volume urine show dehydration, which needs fluid replacement, electrolyte checks and close monitoring.
Answer
A · Dehydration from fluid loss
3.Clinical nursing
Answer: B · Respiratory acidosis
Why this is the answer
A raised PaCO2 with a low pH means the lungs are not removing enough CO2, for example from hypoventilation. A normal bicarbonate suggests it is acute.
Answer
B · Respiratory acidosis
4.Clinical nursing
Answer: D · Its active metabolites build up because the kidneys excrete them
Why this is the answer
Morphine metabolites, including morphine-6-glucuronide, are cleared by the kidneys and accumulate in renal impairment, causing sedation and respiratory depression. Alternative opioids or lower doses are often chosen.
Answer
D · Its active metabolites build up because the kidneys excrete them
5.Arterial blood gas interpretation
Answer: Osm = 310 mOsm/kg
Derived values: calculated serum osmolality is 2·Na⁺ + glucose + urea with all values in mmol/L (2·Na⁺ + glucose/18 + BUN/2.8 with glucose and BUN in mg/dL); normal is about 275–295 mOsm/kg. The P/F ratio is PaO₂ divided by FiO₂ as a fraction. The alveolar oxygen pressure is PAO₂ = FiO₂·(760 − 47) − PaCO₂/0.8 mmHg at sea level, and the A–a gradient is PAO₂ − PaO₂.
Calculated osmolality
Osm = 2·140 + 6.9 + 23.3 = 310.2 ≈ 310 mOsm/kg
Answer
Osm = 310 mOsm/kg
6.Arterial blood gas interpretation
Answer: appropriate compensation
Expected compensation: in metabolic acidosis Winter’s formula predicts PaCO₂ = 1.5·HCO₃⁻ + 8 ± 2 mmHg; a measured value above that range points to an additional respiratory acidosis, below it to an additional respiratory alkalosis. The anion gap AG = Na⁺ − (Cl⁻ + HCO₃⁻), normally about 8–12 mmol/L, separates high-gap from normal-gap metabolic acidosis; low albumin hides a high gap (add 2.5 per g/dL that albumin is below 4.0). The delta ratio (AG − 12)/(24 − HCO₃⁻) between about 0.8 and 2 fits a pure high-gap acidosis (some texts use 1 instead of 0.8), below that an added normal-gap acidosis, and above 2 an added metabolic alkalosis.
Expected PaCO₂
1.5·16 + 8 = 32 → 30–34 mmHg
Compare
measured: 32 mmHg → appropriate compensation
Answer
appropriate compensation
7.Clinical assessment scores
Answer: SI = 0.66
Blood pressure values: pulse pressure PP = SBP − DBP. Mean arterial pressure MAP ≈ (SBP + 2·DBP)/3 = DBP + PP/3, an estimate based on the heart spending about two thirds of each beat in diastole at a normal heart rate (less accurate when the heart rate is fast); a MAP of at least about 65 mmHg is a common target for organ perfusion. The shock index SI = heart rate/SBP is normally about 0.5–0.7; a value above about 1 is a warning sign of shock.
Shock index
SI = 71/107 = 0.6636 ≈ 0.66
Answer
SI = 0.66
Within or below the usual 0.5–0.7.
8.Clinical assessment scores
Answer: low
NEWS2 (National Early Warning Score 2, Royal College of Physicians 2017): score each of the seven parameters with the chart (respiration rate, SpO₂ on scale 1, air or supplemental oxygen, systolic blood pressure, pulse, consciousness on the ACVPU scale and temperature) and add the scores. Clinical risk: 0–4 low; a score of 3 in any single parameter low–medium; 5–6 medium; 7 or more high. A total of 5 or more needs an urgent response.
Score each parameter
RR 16/min → 0
SpO₂ 98% → 0
on air → 0
SBP 150 mmHg → 0
HR 58/min → 0
alert (A) → 0
T 37.1 °C → 0
Total and red scores
NEWS2 = 0 + 0 + 0 + 0 + 0 + 0 + 0 = 0
No parameter scores 3.
Risk group
low
Answer
low
9.Enteral & parenteral nutrition calculations
Answer: %IBW = 114 %
Needs and free water: energy needs are often estimated as kcal/kg/day × weight and protein needs as g/kg/day × weight. A formula is only partly water, so its free water = volume × water fraction; water flushes make up the rest of the daily fluid goal. Ideal body weight (Devine): IBW = 50 kg + 2.3 kg for every inch over 5 feet (60 in) for men, and 45.5 kg + 2.3 kg per inch over 60 in for women; 1 in = 2.54 cm. The formula is meant for adults at least 152.4 cm (5 ft) tall. The numbers are for practice only; at the bedside always follow local protocols and have high-risk doses double-checked.
Ideal body weight (Devine)
176 cm/2.54 = 69.29 in
IBW = 45.5 + 2.3·(69.29 − 60) = 66.87 kg
Percentage of ideal body weight
%IBW = 76/66.87·100 = 113.7 ≈ 114%
Answer
%IBW = 114%
10.Enteral & parenteral nutrition calculations
Answer: NPC : N = 211
Parenteral nutrition: dextrose provides 3.4 kcal/g, amino acids 4 kcal/g and lipid emulsion the kcal/mL stated (2 kcal/mL for 20%, 1.1 kcal/mL for 10%). Grams = % × mL/100. Non-protein kcal (NPC) = dextrose + lipid kcal; nitrogen = protein/6.25. The glucose infusion rate (GIR) in mg/kg/min = dextrose mg/(kg × minutes). The numbers are for practice only; at the bedside always follow local protocols and have high-risk doses double-checked.
Grams of dextrose and amino acids
dextrose: 20·2000/100 = 400 g
amino acids: 3.5·2000/100 = 70 g
Kilocalories per component
dextrose: 400·3.4 = 1360 kcal
amino acids: 70·4 = 280 kcal
lipid: 500·2 = 1000 kcal
Non-protein kcal and nitrogen
NPC = 1360 + 1000 = 2360 kcal
N = 70/6.25 = 11.2 g
Ratio
NPC : N = 2360/11.2 = 210.7 ≈ 211 : 1
Answer
NPC : N = 211
Ratios of about 150 : 1 are typical for stable patients; lower ratios give relatively more protein.
11.ECG rhythm strip interpretation
Answer: sinus bradycardia
Rhythm criteria (lead II): sinus rhythm has an upright P wave before every QRS, a constant PR of 0.12–0.20 s and a narrow QRS: normal sinus rhythm at 60–100/min, sinus bradycardia below 60, sinus tachycardia above 100. Atrial fibrillation: no P waves, a fibrillatory baseline and an irregularly irregular R–R. Atrial flutter: sawtooth flutter waves at about 250–350/min with a fixed conduction ratio such as 2:1 or 4:1. First-degree AV block: sinus rhythm with a constant PR above 0.20 s. Junctional rhythm: narrow QRS at 40–60/min with absent or inverted P waves (PR below 0.12 s, or P after the QRS). A PVC is an early, wide (0.12 s or more), bizarre QRS without a P wave, with the T wave in the opposite direction and usually a full compensatory pause; in bigeminy every second beat is a PVC.
Five steps
1. Rate: R–R = 28 small boxes, 1500 ÷ 28 ≈ 54 per minute.
2. Rhythm: regular, every R–R is 1.12 s.
3. P waves: upright, one before every QRS, all alike.
4. PR interval: 0.14 s, constant, within 0.12–0.20 s.
5. QRS: 0.08 s, narrow (below 0.12 s).
Interpretation
sinus bradycardia
Answer
sinus bradycardia
12.ECG rhythm strip interpretation
Answer: ventricular rate = 48 bpm
AV blocks: march out the P waves and check which ones are followed by a QRS. First-degree: every P conducted, PR constant and above 0.20 s. Second-degree type I (Mobitz I, Wenckebach): the PR lengthens from beat to beat until one P wave is not conducted, then the cycle starts again (group beating). Second-degree type II (Mobitz II): the PR of the conducted beats stays constant, and P waves are suddenly not conducted; the QRS is often wide. Third-degree (complete) block: P waves and QRS complexes are each regular but independent, the PR varies at random and the atrial rate is faster than the escape rate (junctional 40–60/min with a narrow QRS, ventricular 20–40/min with a wide QRS). A 2:1 block cannot be called type I or type II from one strip.
Atrial rate
P–P = 20 small boxes = 0.80 s → 1500 ÷ 20 = 75 ≈ 75 per minute
Ventricular rate
R–R = 31 small boxes = 1.24 s → 1500 ÷ 31 = 48.39 ≈ 48 per minute
Answer
ventricular rate = 48 bpm
Answer
ventricular rate = 48 bpm
Third-degree block with a narrow-complex junctional escape (usually 40–60 per minute).
13.Prioritization & delegation
Answer: A · Turn the patient onto their side
Why this is the answer
A drowsy patient who vomits can aspirate. Turning them to the side lets vomit drain from the mouth; suction and a prescribed antiemetic follow.
Answer
A · Turn the patient onto their side
14.Prioritization & delegation
Answer: A · Metabolic alkalosis
Why this is the answer
Repeated vomiting of stomach contents loses hydrochloric acid, causing metabolic alkalosis, often with low chloride and potassium. Fluids and electrolytes are corrected before surgery.
Answer
A · Metabolic alkalosis
15.Infection control & patient safety
Answer: B · Covering the site with a sleeve or using hand mitts with supervision
Why this is the answer
Covering the line, keeping it out of view and using mitts while observing the patient can stop pulling without fully restricting movement. Restraints and sedation are used only if these fail.
Answer
B · Covering the site with a sleeve or using hand mitts with supervision
16.Infection control & patient safety
Answer: A · Gown and gloves, plus eye protection and mask if splashes are likely
Why this is the answer
MRSA spreads by contact, so a gown and gloves are worn. Standard precautions add eye and face protection when splashes of wound fluid are possible. A respirator is not needed for wound MRSA.
Answer
A · Gown and gloves, plus eye protection and mask if splashes are likely
17.Lab values & electrolytes
Answer: D · Take it with food and a full glass of water, and do not crush extended-release tablets
Why this is the answer
Oral potassium can irritate the esophagus and stomach, so it is taken with food and plenty of fluid, and extended-release forms are swallowed whole. Most salt substitutes contain potassium chloride and can add to the risk of hyperkalemia.Checked against:Potassium (drug information) · MedlinePlus (NIH) (2024)
Answer
D · Take it with food and a full glass of water, and do not crush extended-release tablets
18.Lab values & electrolytes
Answer: A · COPD with chronic CO₂ retention and metabolic compensation
Why this is the answer
In chronic CO₂ retention, as in severe COPD, the kidneys retain bicarbonate over days and bring the pH back towards normal, often to the low end of the range. DKA and diarrhea lower bicarbonate, and aspirin overdose causes rapid breathing that lowers the PaCO₂.Checked against:Respiratory Acidosis · StatPearls (NCBI Bookshelf)
Answer
A · COPD with chronic CO₂ retention and metabolic compensation