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 on warfarin has started eating large spinach and kale salads every day. What is the main concern?
AGreen vegetables damage the liver on warfarin
BThe extra vitamin K may lower the INR
CThere is no interaction between food and warfarin
DThe extra vitamin K may raise the INR
2.Med-surg: cardiovascular & respiratoryHard
Which approach to chest drain removal is commonly taught?
ARemove it slowly while the patient takes a long, deep breath in
BRemove it with the suction still running at full power
CRemove it during a held breath or expiration, then seal the site
DRemove it and leave the site open to drain for a day
3.Med-surg: neuro, endocrine & renalMedium
A patient with gout has recurrent uric acid kidney stones. Which treatment helps prevent them?
ACalcium tablets and a low-fluid diet
BAllopurinol and making the urine less acidic
CVitamin C supplements and a high-meat diet
DRestricting fluids in the evening only
4.Med-surg: neuro, endocrine & renalHard
Three days after a stroke, a patient with dysphagia on a modified diet has a temperature of 38.2 °C (100.8 °F), a respiratory rate of 24/min and crackles at the right lung base. What should the nurse do?
ARecord the findings and recheck them at the next routine observation
BEncourage more fluids by mouth to treat the fever
CSuspect aspiration pneumonia, stop oral intake and escalate for review
DGive paracetamol (acetaminophen) and continue the modified diet as before
5.Med-surg: GI, perioperative & oncologyMedium
Why is the time a surgical limb tourniquet is inflated carefully recorded?
AThe tourniquet slowly loses all its air after one minute
BIt shows how long the anaesthetic gas was used
CThe surgeon is paid per minute of use
DLong inflation can cause nerve and muscle damage
6.Med-surg: GI, perioperative & oncologyHard
After two days of large volumes of IV 5% glucose, a postoperative patient becomes confused with a headache. Sodium is 124 mmol/L. What is the likely cause?
ANormal confusion after any anaesthetic
BHypernatraemia from too much salt
CHypoglycaemia from the glucose
DHyponatraemia from hypotonic fluids
7.Clinical nursingMedium
A rising serum creatinine most often indicates:
AIncreased muscle strength
BReduced kidney function
CImproved liver function
DDehydration of the skin only
8.Clinical nursingHard
A patient on a heparin infusion develops a sudden fall in platelet count five days after starting it. What should you suspect?
AIron deficiency anaemia
BHeparin-induced thrombocytopenia
CNormal response to heparin
DVitamin K deficiency from poor intake
9.Lab values & electrolytesMedium
A patient taking a statin reports new, unexplained muscle pain and weakness. Which laboratory test would the nurse expect to be ordered?
ACreatine kinase (CK)
BCardiac troponin
CSerum ammonia
DSerum lipase
10.Lab values & electrolytesHard
A patient receiving IV magnesium sulfate has a respiratory rate of 9/min and absent patellar reflexes. After stopping the infusion, which medication should the nurse expect to give?
AProtamine sulfate
BSodium bicarbonate
CPotassium chloride
DCalcium gluconate
11.Arterial blood gas interpretationMedium
A practice gas shows a metabolic acidosis with HCO₃⁻ 18 mmol/L. Use Winter’s formula to find the expected PaCO₂ (the centre of the range) in mmHg.
HCO₃⁻ 18 mmol/L
PaCO₂ = mmHg
12.Arterial blood gas interpretationHard
A practice gas shows a respiratory acidosis: pH 7.24, PaCO₂ 77 mmHg (10.3 kPa), HCO₃⁻ 32 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 7.24PaCO₂ 77 mmHg (10.3 kPa)HCO₃⁻ 32 mmol/L
1acute
2chronic
3acute on chronic
13.ECG rhythm strip interpretationMedium
This lead II strip shows sinus rhythm with one pause. Measure the pause, the R–R interval across it, in seconds.
lead II, 25 mm/s, 10 mm/mV1 small box = 0.04 s, 1 large box = 0.20 sstrip length 6 s
pause = s
14.ECG rhythm strip interpretationHard
This patient has a pacemaker. Interpret the lead II strip. 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
1third-degree (complete) AV block
2sinus rhythm with wide QRS
3dual-chamber (AV) paced rhythm
4paced rhythm, failure to capture
15.Prioritization & delegationMedium
A charge nurse needs to free a bed. Which patient is most appropriate for discharge or transfer to a lower level of care?
AAdmitted two hours ago with chest pain; troponin result still pending
BDay 1 after bowel surgery with a new temperature of 38.5 °C
CPneumonia, with an oxygen need that rose overnight from 2 to 4 L/min
DDay 3 after uncomplicated appendectomy, eating, on oral analgesia
16.Prioritization & delegationHard
A patient with anorexia nervosa is admitted. Which finding is the priority?
ARefuses to eat in front of other people
BSays she feels fat although she is very thin
CHas fine, downy hair on her arms
DHeart rate 38/min and potassium 2.8 mEq/L
3Solutions
1.Med-surg: cardiovascular & respiratory
Answer: B · The extra vitamin K may lower the INR
Why this is the answer
A sudden increase in vitamin K intake can reduce the INR and increase clot risk. Patients do not have to avoid these foods but should keep their intake consistent and tell the anticoagulation service about big dietary changes.
Answer
B · The extra vitamin K may lower the INR
2.Med-surg: cardiovascular & respiratory
Answer: C · Remove it during a held breath or expiration, then seal the site
Why this is the answer
Many guidelines suggest removing the tube at the end of a deep breath held (Valsalva) or during expiration, so that the pressure in the chest is positive. The wound is closed with a suture or occlusive dressing, the patient monitored for recurrent pneumothorax and a chest X-ray done if indicated. Analgesia beforehand is good practice.
Answer
C · Remove it during a held breath or expiration, then seal the site
3.Med-surg: neuro, endocrine & renal
Answer: B · Allopurinol and making the urine less acidic
Why this is the answer
Uric acid stones form when urine is acidic and rich in uric acid. High fluid intake, alkalinising the urine (for example with potassium citrate) and allopurinol reduce the risk. Purine-rich foods are limited.
Answer
B · Allopurinol and making the urine less acidic
4.Med-surg: neuro, endocrine & renal
Answer: C · Suspect aspiration pneumonia, stop oral intake and escalate for review
Why this is the answer
These signs suggest aspiration pneumonia, which is a common and serious complication of dysphagia. The patient needs medical review, chest assessment, oxygen if needed, and reassessment of their swallow before eating again.
Answer
C · Suspect aspiration pneumonia, stop oral intake and escalate for review
5.Med-surg: GI, perioperative & oncology
Answer: D · Long inflation can cause nerve and muscle damage
Why this is the answer
A tourniquet creates a bloodless field but causes limb ischaemia. Inflation time and pressure are recorded and the surgeon is told at set intervals, as long inflation can damage nerves and muscle.
Answer
D · Long inflation can cause nerve and muscle damage
6.Med-surg: GI, perioperative & oncology
Answer: D · Hyponatraemia from hypotonic fluids
Why this is the answer
Once the glucose is metabolised, 5% glucose acts as free water. Surgical stress increases ADH, so sodium falls, which can cause cerebral oedema. The team reviews fluids and corrects sodium carefully.
Answer
D · Hyponatraemia from hypotonic fluids
7.Clinical nursing
Answer: B · Reduced kidney function
Why this is the answer
Creatinine is a muscle waste product filtered by the kidneys. A rise shows the glomerular filtration rate is falling, as in acute kidney injury.
Answer
B · Reduced kidney function
8.Clinical nursing
Answer: B · Heparin-induced thrombocytopenia
Why this is the answer
HIT typically appears 5–10 days after starting heparin, with a platelet drop of more than 50% and a risk of thrombosis. Heparin is stopped and a non-heparin anticoagulant used.
Answer
B · Heparin-induced thrombocytopenia
9.Lab values & electrolytes
Answer: A · Creatine kinase (CK)
Why this is the answer
Statins can cause myopathy and, rarely, rhabdomyolysis. A raised CK confirms muscle injury, and the provider may stop the statin. The nurse also asks about dark urine, which can signal myoglobin in the urine.Checked against:Creatine Kinase · MedlinePlus (NIH) (2023)
Answer
A · Creatine kinase (CK)
10.Lab values & electrolytes
Answer: D · Calcium gluconate
Why this is the answer
Absent reflexes and slow breathing indicate magnesium toxicity. The infusion is stopped, the provider is called, the airway and breathing are supported, and IV calcium gluconate is given as prescribed to counteract magnesium.
Answer
D · Calcium gluconate
11.Arterial blood gas interpretation
Answer: PaCO₂ = 35 mmHg
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.
Winter’s formula
PaCO₂ = 1.5·18 + 8 = 35 mmHg
range: 33–37 mmHg
Answer
PaCO₂ = 35 mmHg
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 + 1·3.7 = 27.7 mmol/L
chronic: 24 + 3.5·3.7 = 36.95 mmol/L
Compare
measured: 32 mmol/L → acute on chronic
Answer
acute on chronic
13.ECG rhythm strip interpretation
Answer: pause = 2.04 s
Narrow-complex tachycardia and pauses: supraventricular tachycardia (SVT) is a regular tachycardia at about 150–250/min with narrow QRS complexes; the P waves are usually not visible because they are hidden in the QRS complex or the T wave. Sinus tachycardia in an adult at rest is usually below about 150/min and has a visible P wave before every QRS; atrial flutter with 2:1 conduction often runs at about 150/min and shows sawtooth waves. In sinus arrest the sinus node stops firing for a moment: a pause with no P wave and no QRS whose length is not a whole number of P–P cycles (a pause of exactly two or three cycles points to sinus exit block instead).
Measure
51 small boxes from R to R across the pause
Convert
pause = 51 × 0.04 s = 2.04 s
Compare with P–P
2.04 ÷ 0.84 ≈ 2.4 P–P cycles, not a whole number
Answer
pause = 2.04 s
No P wave appears in the pause, and the pause is not a whole number of P–P cycles: sinus arrest. A pause of exactly two or three cycles would point to sinus exit block.
14.ECG rhythm strip interpretation
Answer: dual-chamber (AV) paced rhythm
Paced rhythms: a pacemaker impulse shows as a narrow vertical pacing spike. After a ventricular spike the QRS is wide (0.12 s or more), because the impulse spreads from the lead through the muscle instead of the conduction system; with right-ventricular pacing it is often mostly negative in lead II. A spike before each P wave means atrial pacing, and a dual-chamber (AV) pacemaker shows an atrial spike and a P wave, then, after the programmed AV delay, a ventricular spike and a wide QRS. Capture means every spike is followed by a depolarisation. Failure to capture is a spike without a P wave or QRS after it; failure to sense (spikes that ignore the patient’s own beats) and failure to pace (no spike when one is due) are the other classic malfunctions.
Five steps
1. Rate: R–R = 25 small boxes, 1500 ÷ 25 ≈ 60 per minute.
2. Rhythm: regular, every R–R is 1.00 s.
3. P waves: each P wave follows its own pacing spike (atrial pacing).
4. AV interval: the second spike comes 0.16 s after the first one (the programmed AV delay).
5. QRS: 0.14 s, wide, right after the second spike (ventricular pacing).
Interpretation
dual-chamber (AV) paced rhythm
Answer
dual-chamber (AV) paced rhythm
The paced QRS is wide by nature; do not call it a bundle branch block or a ventricular rhythm.
15.Prioritization & delegation
Answer: D · Day 3 after uncomplicated appendectomy, eating, on oral analgesia
Why this is the answer
The appendectomy patient is stable, eating and managing with oral pain relief. A pending troponin, rising oxygen needs and a new fever all mean the patient’s course is not yet clear.
Answer
D · Day 3 after uncomplicated appendectomy, eating, on oral analgesia
16.Prioritization & delegation
Answer: D · Heart rate 38/min and potassium 2.8 mEq/L
Why this is the answer
Severe bradycardia and low potassium can cause fatal arrhythmias. The body-image beliefs and eating behaviors matter, but physiological safety comes first.