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 patient has a pulse of 86/min and a blood pressure of 154/92 mmHg. Find the shock index SI = HR/SBP. Round to two decimal places.
HR 86/minBP 154/92 mmHg
SI =
2.Clinical assessment scoresHard
Practice exercise (made-up values, not clinical guidance). Use the NEWS2 chart (SpO₂ scale 1) for these observations: respiration rate 12/min, SpO₂ 96% on room air, blood pressure 142/86 mmHg, pulse 82/min, alert, temperature 36.1 °C. Which clinical risk group does the patient fall into? Click it.
RR 12SpO₂ 96%airSBP 142HR 82AT 36.1 °C
1low
2low–medium
3medium
4high
3.Arterial blood gas interpretationMedium
A practice gas shows PaCO₂ 62 mmHg (8.3 kPa). Use the rule that in acute respiratory acidosis HCO₃⁻ rises by 1 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 a metabolic alkalosis with HCO₃⁻ 40 mmol/L. Use expected PaCO₂ = 0.7·HCO₃⁻ + 21 to find the expected PaCO₂.
HCO₃⁻ 40 mmol/L
PaCO₂ = mmHg
5.Nursing fundamentalsMedium
Which approach suits teaching an older adult with poor eyesight and mild memory problems?
ATeaching only the family and not the patient
BShort sessions, large-print materials and repeating key points
CA detailed leaflet in small print for them to read later at home
DOne long session with all the information at once
6.Nursing fundamentalsHard
A patient has been taught to walk with underarm crutches. Which statement shows a need for further teaching?
A"I'll check the rubber tips regularly for wear."
B"I'll rest my weight on the tops of the crutches under my arms."
C"I'll keep the crutch tips about a step out to the side and front."
D"I'll take my weight through my hands on the hand grips."
7.Nursing math & unit conversionsMedium
Practice exercise (made-up values, not clinical guidance). A patient’s temperature is 99.8 °F. Convert it to degrees Celsius T with °C = (°F − 32) × 5/9. Round to one decimal place.
99.8 °F
T = °C
8.Nursing math & unit conversionsHard
Practice exercise (made-up values, not clinical guidance). An infusion starts at 21:45 and finishes at 07:10 the next morning (24-hour clock). How many hours t did it run? Give the answer in hours as a decimal, rounded to two decimal places.
21:4507:10
t = h
3Solutions
1.Clinical assessment scores
Answer: SI = 0.56
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 = 86/154 = 0.5584 ≈ 0.56
Answer
SI = 0.56
Within or below the usual 0.5–0.7.
2.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 12/min → 0
SpO₂ 96% → 0
on air → 0
SBP 142 mmHg → 0
HR 82/min → 0
alert (A) → 0
T 36.1 °C → 0
Total and red scores
NEWS2 = 0 + 0 + 0 + 0 + 0 + 0 + 0 = 0
No parameter scores 3.
Risk group
low
Answer
low
3.Arterial blood gas interpretation
Answer: HCO₃⁻ = 26.2 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
|62 − 40| = 22 mmHg → 2.2 × 10 mmHg
Expected HCO₃⁻
HCO₃⁻ = 24 + 1·2.2 = 26.2 mmol/L
Answer
HCO₃⁻ = 26.2 mmol/L
4.Arterial blood gas interpretation
Answer: PaCO₂ = 49 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.
Expected PaCO₂
0.7·40 + 21 = 49 mmHg
Answer
PaCO₂ = 49 mmHg
The rise has a limit: PaCO₂ rarely goes above about 55 mmHg from compensation alone.
5.Nursing fundamentals
Answer: B · Short sessions, large-print materials and repeating key points
Why this is the answer
Older learners benefit from short, focused sessions, clear large print, good lighting, repetition and teach-back. Involving family can help but should not replace teaching the patient.
Answer
B · Short sessions, large-print materials and repeating key points
6.Nursing fundamentals
Answer: B · "I'll rest my weight on the tops of the crutches under my arms."
Why this is the answer
Leaning on the armpits can damage the brachial plexus and cause crutch palsy. Weight is taken through the hands, with a gap of a few finger-widths between the crutch top and the armpit.
Answer
B · "I'll rest my weight on the tops of the crutches under my arms."
7.Nursing math & unit conversions
Answer: T = 37.7 °C
Temperature: °C = (°F − 32) × 5/9 and °F = °C × 9/5 + 32. Subtract 32 before you multiply when going from °F, and add 32 after you multiply when going from °C. A quick check: 37 °C is 98.6 °F, and every 1 °C is 1.8 °F.
Subtract 32
99.8 − 32 = 67.8
Multiply by 5/9
T = 67.8·5/9 = 37.67 ≈ 37.7 °C
Answer
T = 37.7 °C
8.Nursing math & unit conversions
Answer: t = 9.42 h
24-hour clock: from 1 PM onwards add 12 to the hour (3:45 PM = 15:45). Midnight to 12:59 AM is 00:00–00:59, and 12:00–12:59 PM stays 12:00–12:59. Going back, subtract 12 from hours 13–23 and add PM; hours 00 become 12 AM. Count time across midnight in two parts: up to 24:00 (00:00), then from 00:00 on.