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 pulse oximeter on a patient's finger gives an unreliable, flickering reading. Which factor is the most likely cause?
ACold hands with poor peripheral circulation
BThe patient having eaten recently
CThe patient sitting upright in a chair
DA regular heart rate of 75 beats per minute
2.Med-surg: cardiovascular & respiratoryHard
A patient on spironolactone and an ACE inhibitor has a potassium of 6.8 mmol/L (6.8 mEq/L) with peaked T waves. What is usually given first to protect the heart?
AA dose of digoxin
BOral potassium supplements
CAn IV furosemide bolus as the only treatment
DIntravenous calcium gluconate or chloride
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?
ANormal diuresis
BSIADH
CAcute kidney injury
DDiabetes insipidus
4.Med-surg: neuro, endocrine & renalHard
An older patient with type 2 diabetes has glucose 48 mmol/L, osmolality 365 mOsm/kg, no significant ketones and confusion. What is the first priority?
ACareful IV fluids with close checks of osmolality, sodium and glucose
BOral glucose to prevent hypoglycaemia during treatment
CA large IV insulin bolus to bring glucose to normal within an hour
DStrict fluid restriction to avoid cerebral oedema
5.Med-surg: GI, perioperative & oncologyMedium
Which practice is correct when giving parenteral nutrition through a central line?
AGive other IV drugs through the same lumen to save time
BDisconnect and reconnect the line without cleaning the hub
CUse a dedicated lumen and strict aseptic technique
DLet the bag hang at room temperature for several days
6.Med-surg: GI, perioperative & oncologyHard
A patient with a toe ulcer says the leg pain is worse at night and eases when they hang the leg over the side of the bed. What does this suggest?
AVenous insufficiency
BNeuropathic itching
CArterial insufficiency
DLymphoedema
7.Clinical nursingMedium
Why is blood pressure monitored closely in a patient with an epidural infusion?
AThe epidural pump uses the blood pressure to set the rate
BEpidurals always cause severe hypertension that needs regular treatment
CThe local anaesthetic can block sympathetic nerves and cause hypotension
DBlood pressure readings show whether the catheter is infected
8.Clinical nursingHard
An older patient has fallen several times since starting a new medicine. Which drug group is most likely to contribute?
ABenzodiazepine sleeping tablets
BVitamin D supplements
CLubricating eye drops
DEmollient creams applied to the legs
9.Lab values & electrolytesMedium
A patient's levothyroxine dose was changed today. When is the TSH usually rechecked?
AAfter about 24 hours
BAfter about 1 year
CAfter about 6–8 weeks
DAfter about 3 days
10.Lab values & electrolytesHard
An 82-year-old woman without a catheter has a urine culture growing bacteria, but no fever, urinary symptoms or change in mental state. What is the best interpretation?
AAsymptomatic bacteriuria, usually not treated with antibiotics
BContamination, so the culture must be repeated every week
CA urinary tract infection that needs urgent IV antibiotics
DPyelonephritis, which needs admission and IV fluids today
11.Arterial blood gas interpretationMedium
A practice gas shows PaCO₂ 64 mmHg (8.5 kPa). Use the rule that in chronic respiratory acidosis HCO₃⁻ rises by 3.5 mmol/L for every 10 mmHg that PaCO₂ is above 40, starting from HCO₃⁻ 24 mmol/L, to find the expected HCO₃⁻.
A practice gas shows pH 7.32, PaCO₂ 28 mmHg (3.7 kPa) and HCO₃⁻ 14 mmol/L, with Na⁺ 133 and Cl⁻ 95 mmol/L. Use the anion gap and the delta ratio to click the best interpretation.
Measure the QT interval and the R–R interval on this regular lead II strip, then calculate the rate-corrected QTc with Bazett’s formula QTc = QT/√RR (both in seconds). Give the answer in seconds to three decimals.
lead II, 25 mm/s, 10 mm/mV1 small box = 0.04 s, 1 large box = 0.20 sstrip length 6 s
QTc = 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
1second-degree AV block type I (Wenckebach)
2junctional rhythm
3third-degree (complete) AV block
4second-degree AV block type II
15.Prioritization & delegationMedium
A parent of a child with influenza talks with the nurse. Which statement shows a need for further teaching?
A“I will give my child aspirin to bring the fever down.”
B“I will call if my child has trouble breathing.”
C“I will give my child plenty of fluids.”
D“I will keep my child home from school and away from others while unwell.”
16.Prioritization & delegationHard
Two days after starting haloperidol, a patient suddenly develops painful neck twisting and the eyes roll upwards. What should the nurse anticipate?
AA higher dose of haloperidol to calm the patient and stop the movements quickly
BPhysical restraint until the spasm passes
CNo action, because the spasm is a sign of improvement
DAn anticholinergic drug, such as benztropine or procyclidine, as prescribed
3Solutions
1.Med-surg: cardiovascular & respiratory
Answer: A · Cold hands with poor peripheral circulation
Why this is the answer
Poor perfusion (cold, shock, vasoconstriction), movement, dark nail varnish or bright ambient light can make readings unreliable. The nurse checks the waveform, warms the hand or uses an ear probe, and compares the reading with the clinical picture.
Answer
A · Cold hands with poor peripheral circulation
2.Med-surg: cardiovascular & respiratory
Answer: D · Intravenous calcium gluconate or chloride
Why this is the answer
Severe hyperkalaemia with ECG changes is an emergency. IV calcium stabilises the myocardium within minutes. Insulin with glucose and nebulised salbutamol shift potassium into cells, and the cause (here spironolactone and the ACE inhibitor) is stopped. Cardiac monitoring is essential.
Answer
D · Intravenous calcium gluconate or chloride
3.Med-surg: neuro, endocrine & renal
Answer: D · 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
D · Diabetes insipidus
4.Med-surg: neuro, endocrine & renal
Answer: A · Careful IV fluids with close checks of osmolality, sodium and glucose
Why this is the answer
HHS is managed first with IV fluids, which alone often lower glucose. Rapid falls in osmolality risk cerebral oedema, so it is lowered gradually. Insulin is added at a low rate if ketones are present or glucose stops falling with fluids. VTE prophylaxis is important because of the high clot risk.
Answer
A · Careful IV fluids with close checks of osmolality, sodium and glucose
5.Med-surg: GI, perioperative & oncology
Answer: C · Use a dedicated lumen and strict aseptic technique
Why this is the answer
PN is rich in nutrients that bacteria can use. A dedicated lumen, aseptic non-touch technique and hanging limits reduce catheter-related bloodstream infection.
Answer
C · Use a dedicated lumen and strict aseptic technique
6.Med-surg: GI, perioperative & oncology
Answer: C · Arterial insufficiency
Why this is the answer
Rest pain eased by dependency is typical of severe peripheral arterial disease. Elevating the leg worsens pain, and compression is avoided. Vascular assessment is needed.
Answer
C · Arterial insufficiency
7.Clinical nursing
Answer: C · The local anaesthetic can block sympathetic nerves and cause hypotension
Why this is the answer
Epidural local anaesthetic can cause vasodilation and hypotension. Nurses also monitor sedation, respiratory rate, block height, motor function and the catheter site.
Answer
C · The local anaesthetic can block sympathetic nerves and cause hypotension
8.Clinical nursing
Answer: A · Benzodiazepine sleeping tablets
Why this is the answer
Sedatives, hypnotics, antipsychotics and drugs that lower blood pressure increase falls risk. A medication review is part of every falls assessment.
Answer
A · Benzodiazepine sleeping tablets
9.Lab values & electrolytes
Answer: C · After about 6–8 weeks
Why this is the answer
Levothyroxine has a half-life of about a week, so a steady state takes about 6 weeks. The TSH is therefore rechecked about 6–8 weeks after a dose change; checking earlier gives a misleading result.Checked against:Hypothyroidism · MedlinePlus (NIH) (2024)
Answer
C · After about 6–8 weeks
10.Lab values & electrolytes
Answer: A · Asymptomatic bacteriuria, usually not treated with antibiotics
Why this is the answer
Asymptomatic bacteriuria is common in older adults and usually should not be treated, because treatment brings adverse effects and resistance without benefit. Exceptions include pregnancy and some urological procedures.Checked against:Asymptomatic Bacteriuria · StatPearls (NCBI Bookshelf) (2023)
Answer
A · Asymptomatic bacteriuria, usually not treated with antibiotics
11.Arterial blood gas interpretation
Answer: HCO₃⁻ = 32.4 mmol/L
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.
Change in PaCO₂
|64 − 40| = 24 mmHg → 2.4 × 10 mmHg
Expected HCO₃⁻
HCO₃⁻ = 24 + 3.5·2.4 = 32.4 mmol/L
Answer
HCO₃⁻ = 32.4 mmol/L
12.Arterial blood gas interpretation
Answer: pure high-gap acidosis
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.
Anion gap
AG = 133 − (95 + 14) = 24
Delta ratio
(24 − 12)/(24 − 14) = 1.2
pure high-gap acidosis
Answer
pure high-gap acidosis
13.ECG rhythm strip interpretation
Answer: QTc = 0.491 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
QT = 9.5 × 0.04 = 0.38 s
RR = 15 × 0.04 = 0.60 s
Bazett’s formula
QTc = 0.38/√0.60 = 0.38/0.7746 = 0.491 s
Answer
QTc = 0.491 s
Above the usual limits for both men (about 0.45 s) and women (about 0.46 s): prolonged. (491 ms)
14.ECG rhythm strip interpretation
Answer: third-degree (complete) AV block
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: R–R = 32 small boxes, 1500 ÷ 32 ≈ 47 per minute.
2. Rhythm: R–R regular (1.28 s) and P–P regular (0.84 s), but the two are independent.
3. P waves: upright and regular at 71 per minute, but not linked to the QRS complexes; some hide in a QRS or a T wave.
4. PR interval: varies from beat to beat; there is no fixed relation.
5. QRS: 0.08 s, narrow (below 0.12 s).
Interpretation
third-degree (complete) AV block
Answer
third-degree (complete) AV block
Type II and third-degree blocks are the ones that can suddenly progress, so textbooks rank them as more serious than type I.
15.Prioritization & delegation
Answer: A · “I will give my child aspirin to bring the fever down.”
Why this is the answer
Aspirin in children with viral illnesses such as influenza or chickenpox is linked to Reye syndrome. Fluids, rest at home and reporting breathing trouble are correct.
Answer
A · “I will give my child aspirin to bring the fever down.”
16.Prioritization & delegation
Answer: D · An anticholinergic drug, such as benztropine or procyclidine, as prescribed
Why this is the answer
Acute dystonia is an early extrapyramidal effect of antipsychotics. It responds quickly to an anticholinergic drug; it can be frightening, and laryngeal spasm can threaten the airway.
Answer
D · An anticholinergic drug, such as benztropine or procyclidine, as prescribed