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.
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.
2Practice problems
1.Med-surg: cardiovascular & respiratoryMedium
A patient is starting doxazosin, an alpha-blocker, for hypertension. Which advice is most important?
ATake the first dose at bedtime, as dizziness and fainting can occur
BStop it suddenly if the heart rate rises after the first few doses
CAvoid all potassium-containing foods
DTake it with a large glass of grapefruit juice to improve absorption
2.Med-surg: cardiovascular & respiratoryHard
Which task for a stable patient with heart failure can the registered nurse most appropriately delegate to a healthcare assistant (unlicensed assistive personnel)?
ADeciding whether to give the furosemide dose
BMeasuring and recording the morning weight
CAssessing lung sounds for new crackles
DTeaching the patient about a low-salt diet
3.Med-surg: neuro, endocrine & renalMedium
After pituitary surgery, a patient passes 400 mL of urine per hour for three hours with a low specific gravity. What should the nurse suspect?
ADiabetes insipidus
BNormal diuresis
CSIADH
DAcute kidney injury
4.Med-surg: neuro, endocrine & renalHard
A patient with CKD has a high phosphate, a low calcium and a high PTH. What does this show?
AHypoparathyroidism after neck surgery
BSecondary hyperparathyroidism from CKD
CPrimary hyperparathyroidism from a tumour
DToo much vitamin D from supplements
5.Med-surg: GI, perioperative & oncologyMedium
Why is the "whoosh" test no longer used to check nasogastric tube position?
AThe air always makes the tube block
BIt needs an X-ray machine at the bedside
CAir can be heard even when the tube is in the lung
DThe test is far too painful for most patients to tolerate
6.Med-surg: GI, perioperative & oncologyHard
A patient has an implanted port for chemotherapy. Which needle is used to access it?
AA standard hollow needle used for venepuncture
BA non-coring (Huber) needle
CAn intramuscular injection needle
DA wide-bore cannula with a steel stylet
7.Clinical nursingMedium
A patient is receiving IV fluids for several days. Which monitoring is essential?
AFluid balance, regular weights and urea, creatinine and electrolytes
BMonthly HbA1c
CWeekly temperature and a single blood glucose reading
DPeak flow readings
8.Clinical nursingHard
A dying patient has noisy, rattling breathing caused by secretions in the throat and is unconscious. Which approach is appropriate?
AStart deep oropharyngeal suctioning every 10 minutes through the night
BReposition, consider prescribed antisecretory drugs and support the family
CTell the family that the patient is suffocating and needs ventilation
DBegin rapid intravenous fluids to thin and clear the secretions
9.Lab values & electrolytesMedium
A patient’s white cell count is 16 × 10³/µL with a high proportion of immature neutrophils (bands). What does this most likely indicate?
AA normal result
BIron-deficiency anemia
CA chronic viral illness only
DAn acute bacterial infection
10.Lab values & electrolytesHard
A patient with a sodium of 132 mEq/L and blood glucose of 600 mg/dL (33.3 mmol/L) is admitted. Why is the sodium value interpreted with care?
AThe sodium result must be a laboratory error
BHigh glucose raises the measured sodium falsely, so it is really lower
CGlucose has no effect on the measured sodium
DHigh glucose draws water into the blood, diluting the sodium
11.Arterial blood gas interpretationMedium
Practice values: Na⁺ 137 mmol/L, glucose 32.5 mmol/L and urea 24.3 mmol/L. Calculate the serum osmolality Osm = 2·Na⁺ + glucose + urea to the nearest whole number.
Na⁺ 137 mmol/Lglucose 32.5 mmol/Lurea 24.3 mmol/L
Osm = mOsm/kg
12.Arterial blood gas interpretationHard
A practice gas shows a respiratory acidosis: pH 7.22, PaCO₂ 85 mmHg (11.3 kPa), HCO₃⁻ 34 mmol/L. Use the rules ‘HCO₃⁻ rises 1 mmol/L per 10 mmHg (acute) or 3.5 mmol/L per 10 mmHg (chronic)’ to classify it. Click your answer.
pH 7.22PaCO₂ 85 mmHg (11.3 kPa)HCO₃⁻ 34 mmol/L
1acute
2chronic
3acute on chronic
13.ECG rhythm strip interpretationMedium
Measure the QT interval on this lead II strip, in seconds.
lead II, 25 mm/s, 10 mm/mV1 small box = 0.04 s, 1 large box = 0.20 sstrip length 6 s
QT = s
14.ECG rhythm strip interpretationHard
This lead II strip shows a conduction problem between the atria and the ventricles. 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
1atrial fibrillation
2third-degree (complete) AV block
3first-degree AV block
4second-degree AV block type I (Wenckebach)
15.Prioritization & delegationMedium
A patient asks the nursing assistant about the side effects of a new medication. What should the assistant do?
AReassure the patient that side effects are rare
BExplain the side effects listed in the drug’s patient leaflet
CLook the drug up online and read out what it says
DSay the nurse will come to answer, and tell the nurse
16.Prioritization & delegationHard
Which patient on a renal unit should the nurse see first?
AA patient on peritoneal dialysis whose drained fluid is clear
BA patient on hemodialysis who missed yesterday’s session and now has muscle weakness and an irregular pulse
CA patient asking for advice about a low-phosphate diet
DA patient whose arteriovenous fistula has a strong thrill and bruit
3Solutions
1.Med-surg: cardiovascular & respiratory
Answer: A · Take the first dose at bedtime, as dizziness and fainting can occur
Why this is the answer
Alpha-blockers can cause marked first-dose postural hypotension. Taking the first dose at bedtime and rising slowly reduces the risk of falls. They are also used for symptoms of an enlarged prostate.
Answer
A · Take the first dose at bedtime, as dizziness and fainting can occur
2.Med-surg: cardiovascular & respiratory
Answer: B · Measuring and recording the morning weight
Why this is the answer
Weighing a stable patient is a routine, measurable task that can be delegated, with the result reported to the nurse. Assessment, patient teaching and clinical decisions about medicines require the registered nurse's judgement and cannot be delegated.
Answer
B · Measuring and recording the morning weight
3.Med-surg: neuro, endocrine & renal
Answer: A · Diabetes insipidus
Why this is the answer
Damage to the posterior pituitary or hypothalamus can stop ADH release, causing cranial DI with large volumes of dilute urine. The nurse reports it, monitors fluid balance and serum sodium closely and anticipates treatment with desmopressin.
Answer
A · Diabetes insipidus
4.Med-surg: neuro, endocrine & renal
Answer: B · Secondary hyperparathyroidism from CKD
Why this is the answer
In CKD, phosphate retention and low active vitamin D lower calcium, so the parathyroid glands release more PTH. This secondary hyperparathyroidism weakens bone. Treatment includes phosphate control, vitamin D and sometimes calcimimetics.
Answer
B · Secondary hyperparathyroidism from CKD
5.Med-surg: GI, perioperative & oncology
Answer: C · Air can be heard even when the tube is in the lung
Why this is the answer
Auscultation of injected air cannot distinguish the stomach from the lungs or oesophagus, and misplaced tubes have caused deaths. pH testing of aspirate or X-ray is used instead.
Answer
C · Air can be heard even when the tube is in the lung
6.Med-surg: GI, perioperative & oncology
Answer: B · A non-coring (Huber) needle
Why this is the answer
Implanted ports have a silicone septum that reseals after access with a non-coring needle. Aseptic technique, checking blood return before use and flushing according to policy keep the device working safely.
Answer
B · A non-coring (Huber) needle
7.Clinical nursing
Answer: A · Fluid balance, regular weights and urea, creatinine and electrolytes
Why this is the answer
IV fluids can cause overload or electrolyte imbalance. Fluid balance charts, weight, clinical assessment and blood tests guide the prescription.
Answer
A · Fluid balance, regular weights and urea, creatinine and electrolytes
8.Clinical nursing
Answer: B · Reposition, consider prescribed antisecretory drugs and support the family
Why this is the answer
The "death rattle" is managed by repositioning, mouth care and sometimes drugs that reduce secretions. Explaining it to relatives eases their distress.
Answer
B · Reposition, consider prescribed antisecretory drugs and support the family
9.Lab values & electrolytes
Answer: D · An acute bacterial infection
Why this is the answer
A raised white count with more bands (a “left shift”) suggests that the marrow is responding to an acute bacterial infection or severe inflammation. The result is read together with the patient’s signs, such as fever.Checked against:Blood Differential · MedlinePlus (NIH) (2024)
Answer
D · An acute bacterial infection
10.Lab values & electrolytes
Answer: D · High glucose draws water into the blood, diluting the sodium
Why this is the answer
High glucose draws water from the cells into the blood, lowering the measured sodium. As the glucose is treated, the sodium usually rises. A common correction adds about 1.6–2.4 mEq/L of sodium for every 100 mg/dL of glucose above 100 mg/dL.Checked against:Sodium blood test · MedlinePlus (NIH) (2025)
Answer
D · High glucose draws water into the blood, diluting the sodium
11.Arterial blood gas interpretation
Answer: Osm = 331 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 = 2·137 + 32.5 + 24.3 = 330.8 ≈ 331 mOsm/kg
Answer
Osm = 331 mOsm/kg
12.Arterial blood gas interpretation
Answer: acute on chronic
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 HCO₃⁻
acute: 24 + 1·4.5 = 28.5 mmol/L
chronic: 24 + 3.5·4.5 = 39.75 mmol/L
Compare
measured: 34 mmol/L → acute on chronic
Answer
acute on chronic
13.ECG rhythm strip interpretation
Answer: QT = 0.42 s
QT and QTc: the QT interval runs from the start of the QRS complex to the end of the T wave. It shortens as the heart rate rises, so it is corrected for rate with the R–R interval in seconds: Bazett QTc = QT/√RR and Fridericia QTc = QT/∛RR. Bazett is the formula most textbooks use; it over-corrects at fast rates, where Fridericia is preferred. Limits differ between references: a QTc above about 0.45 s in men or 0.46 s in women is usually called prolonged, and above 0.50 s markedly prolonged.
Measure
10.5 small boxes from the start of the QRS to the end of the T wave
Convert
QT = 10.5 × 0.04 s = 0.42 s
Answer
QT = 0.42 s
A rough rule: at normal rates the QT should be less than half the R–R interval (here R–R = 0.76 s).
14.ECG rhythm strip interpretation
Answer: second-degree AV block type I (Wenckebach)
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.
Five steps
1. Rate: 5 QRS complexes in 6 s, × 10 = 50 per minute.
2. Rhythm: regularly irregular, the QRS complexes come in groups separated by a pause (group beating).
3. P waves: upright and regular (P–P 0.88 s, 68 per minute); one P in every 4 is not followed by a QRS.
4. PR interval: lengthens 0.16 → 0.30 → 0.38 s, then a P wave is not conducted.
5. QRS: 0.10 s, narrow (below 0.12 s).
Interpretation
second-degree AV block type I (Wenckebach)
Answer
second-degree AV block type I (Wenckebach)
15.Prioritization & delegation
Answer: D · Say the nurse will come to answer, and tell the nurse
Why this is the answer
Patient teaching about medicines is a nursing responsibility. The assistant passes the question on to the nurse, so the patient gets accurate information that fits their situation.
Answer
D · Say the nurse will come to answer, and tell the nurse
16.Prioritization & delegation
Answer: B · A patient on hemodialysis who missed yesterday’s session and now has muscle weakness and an irregular pulse
Why this is the answer
A missed dialysis session lets potassium build up. Muscle weakness and an irregular pulse suggest hyperkalemia, which can cause fatal arrhythmias, so the nurse assesses at once, arranges cardiac monitoring and escalates. A thrill and bruit and clear effluent are expected findings, and diet advice can wait.
Answer
B · A patient on hemodialysis who missed yesterday’s session and now has muscle weakness and an irregular pulse