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.
Nursing math & unit conversions
Metric steps
1 kg = 1000 g, 1 g = 1000 mg, 1 mg = 1000 mcg, 1 L = 1000 mL
Weight and length
1 kg = 2.2 lb, 1 lb = 16 oz, 1 in = 2.54 cm, 1 ft = 12 in
Household measures
1 tsp = 5 mL, 1 tbsp = 15 mL, 1 fl oz = 30 mL, 1 cup = 8 fl oz = 240 mL
Write the given quantity with its unit and the unit you want.
Pick the equivalent: 1000 between kg, g, mg and mcg or L and mL; 1 kg = 2.2 lb; 1 tsp = 5 mL, 1 tbsp = 15 mL, 1 fl oz = 30 mL, 1 cup = 240 mL.
Write it as a fraction so that the unwanted unit cancels; for a rate, use one fraction per unit that changes.
Check the direction: a smaller unit gives a bigger number.
Round only the final answer, to the precision the question names.
2Practice problems
1.Clinical assessment scoresMedium
Practice exercise (made-up values, not clinical guidance). A practice patient is assessed with the Braden scale: sensory perception: no impairment; moisture: very moist; activity: walks frequently; mobility: slightly limited; nutrition: adequate; friction and shear: no apparent problem. Find the Braden total B.
6–23
B =
2.Clinical assessment scoresHard
Practice exercise (made-up values, not clinical guidance). An adult weighs 115 kg and is 164 cm tall. Calculate the BMI and click the WHO weight category.
115 kg164 cm
1underweight
2healthy weight
3overweight
4obesity class I
5obesity class II
6obesity class III
3.Arterial blood gas interpretationMedium
Practice values: Na⁺ 148 mmol/L, glucose 4.2 mmol/L and urea 24 mmol/L. Calculate the serum osmolality Osm = 2·Na⁺ + glucose + urea to the nearest whole number.
Na⁺ 148 mmol/Lglucose 4.2 mmol/Lurea 24 mmol/L
Osm = mOsm/kg
4.Arterial blood gas interpretationHard
A practice gas shows pH 7.22, PaCO₂ 20 mmHg (2.7 kPa) and HCO₃⁻ 8 mmol/L, with Na⁺ 143 and Cl⁻ 112 mmol/L. Use the anion gap and the delta ratio to click the best interpretation.
A patient shouts at the nurse that nobody has told them when their operation will be. What is the best first response?
AArgue back that the staff are very busy
BWalk away until the patient calms down by themselves
CStay calm, listen and acknowledge their frustration
DTell the patient to stop shouting or leave the ward
6.Nursing fundamentalsHard
Which pair of details is best for confirming a patient's identity before giving a medicine?
AThe name on the door and the patient's face
BFull name and date of birth, checked against the wristband
CBed number and the patient's first name, checked against the ward list
DRoom number and diagnosis
7.Nursing math & unit conversionsMedium
Practice exercise (made-up values, not clinical guidance). A dose calculation for a small injection gives 0.50627 mL. The rule in this exercise is that volumes below 1 mL are rounded to the nearest hundredth of a mL. What value x do you record?
0.50627 mL
x = mL
8.Nursing math & unit conversionsHard
Practice exercise (made-up values, not clinical guidance). A prescription reads 2 tsp of an oral suspension four times a day for 14 days. The suspension comes in 50 mL bottles. Using 1 tsp = 5 mL, how many whole bottles N must be supplied so the course is complete?
2 tspfour times a day14 days50 mL1 tsp = 5 mL
N =
3Solutions
1.Clinical assessment scores
Answer: B = 19
Braden scale: six subscales for pressure-injury risk. Sensory perception, moisture, activity, mobility and nutrition score 1 to 4, from the worst level (1) to no problem (4); friction and shear scores 1 to 3. The total runs from 6 to 23, and a lower total means a higher risk. Common bands: 19–23 not at risk, 15–18 mild risk, 13–14 moderate risk, 10–12 high risk and 9 or below very high risk.
Score each subscale
sensory perception: no impairment → 4
moisture: very moist → 2
activity: walks frequently → 4
mobility: slightly limited → 3
nutrition: adequate → 3
friction and shear: no apparent problem → 3
Add
Braden total = 4 + 2 + 4 + 3 + 3 + 3 = 19
Answer
B = 19
2.Clinical assessment scores
Answer: obesity class III
Body mass index: BMI = weight (kg)/height (m)², with the height converted to metres first. With pounds and inches, BMI = 703 × weight (lb)/height (in)². WHO adult categories: below 18.5 underweight, 18.5–24.9 healthy weight, 25.0–29.9 overweight, 30.0–34.9 obesity class I, 35.0–39.9 obesity class II and 40 or more obesity class III.
BMI
BMI = 115/1.64² = 42.76
Category
obesity class III
Answer
obesity class III
3.Arterial blood gas interpretation
Answer: Osm = 324 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 = 2·148 + 4.2 + 24 = 324.2 ≈ 324 mOsm/kg
Answer
Osm = 324 mOsm/kg
4.Arterial blood gas interpretation
Answer: added normal-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 = 143 − (112 + 8) = 23
Delta ratio
(23 − 12)/(24 − 8) = 0.6875
added normal-gap acidosis
Answer
added normal-gap acidosis
5.Nursing fundamentals
Answer: C · Stay calm, listen and acknowledge their frustration
Why this is the answer
Listening calmly and acknowledging feelings often de-escalates anger. The nurse then finds out the answer or explains what will happen next. Staff safety is maintained throughout.
Answer
C · Stay calm, listen and acknowledge their frustration
6.Nursing fundamentals
Answer: B · Full name and date of birth, checked against the wristband
Why this is the answer
At least two personal identifiers, such as name, date of birth and hospital number, are checked with the patient and the wristband. Bed and room numbers change and are not identifiers.
Answer
B · Full name and date of birth, checked against the wristband
7.Nursing math & unit conversions
Answer: x = 0.51 mL
Rounding: look at the digit just after the place you round to: 5 or more rounds up, 4 or less leaves the digit as it is. Round only the final answer, never the steps. Typical exam rules: volumes of 1 mL or more to the nearest tenth, volumes below 1 mL to the nearest hundredth, drip rates to whole drops and weights to one decimal place; always follow the rule the question states.
Digit in the hundredths place
0.50627 → 0
Only the next digit decides
0.50627 → 6
6 is 5 or more, so round 0 up.
The digits after it (27) are ignored: round once, never step by step.
Round
x = 0.51 mL
Answer
x = 0.51 mL
8.Nursing math & unit conversions
Answer: N = 12
Dimensional analysis: write the given quantity, then multiply by conversion factors written as fractions (for example 60 min/1 h or 1 mg/1000 mcg) so that each unwanted unit appears once on top and once underneath and cancels. When only the wanted unit is left, calculate. Use the equivalents the question gives and round only the final answer.