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). Use the NEWS2 chart (SpO₂ scale 1) for these observations: respiration rate 12/min, SpO₂ 97% on supplemental oxygen, blood pressure 118/70 mmHg, pulse 76/min, unresponsive, temperature 35.5 °C. What is the NEWS2 total score?
RR 12SpO₂ 97%O₂SBP 118HR 76UT 35.5 °C
NEWS2 =
2.Clinical assessment scoresHard
Practice exercise (made-up values, not clinical guidance). An adult weighs 111 kg and is 177 cm tall. Calculate the BMI and click the WHO weight category.
111 kg177 cm
1underweight
2healthy weight
3overweight
4obesity class I
5obesity class II
6obesity class III
3.Arterial blood gas interpretationMedium
A practice gas shows a metabolic acidosis with HCO₃⁻ 10 mmol/L. Use Winter’s formula to find the expected PaCO₂ (the centre of the range) in mmHg.
HCO₃⁻ 10 mmol/L
PaCO₂ = mmHg
4.Arterial blood gas interpretationHard
Practice values: Na⁺ 140, Cl⁻ 112 and HCO₃⁻ 11 mmol/L. Calculate the delta ratio (AG − 12)/(24 − HCO₃⁻), using AG = Na⁺ − (Cl⁻ + HCO₃⁻). Give two decimals.
Na⁺ 140 mmol/LCl⁻ 112 mmol/LHCO₃⁻ 11 mmol/L
delta ratio =
5.Nursing fundamentalsMedium
An older patient is found to be mildly hypothermic. Which care is most appropriate?
APlacing hot water bottles directly on the skin
BPutting the patient in a very hot bath straight away
CGradual rewarming with blankets and warm surroundings
DGiving an alcoholic drink to warm them up
6.Nursing fundamentalsHard
According to the gate control theory, why can rubbing a bumped elbow ease the pain?
ARubbing increases the release of pain chemicals so the nerves tire out
BTouch signals reduce pain signals passing up the spinal cord
CRubbing removes the damaged tissue from the elbow
DRubbing makes the elbow numb by stopping its blood supply
7.Nursing math & unit conversionsMedium
Practice exercise (made-up values, not clinical guidance). A newborn weighs 10 lb 6 oz. Using 1 lb = 16 oz and 1 kg = 2.2 lb, find the weight m in kilograms. Round to two decimal places.
10 lb 6 oz1 lb = 16 oz1 kg = 2.2 lb
m = kg
8.Nursing math & unit conversionsHard
Practice exercise (made-up values, not clinical guidance). An order reads 3 mcg/kg/min for a patient who weighs 53 kg. Express the dose rate D in mg/h. Round to two decimal places.
3 mcg/kg/min53 kg
D = mg/h
3Solutions
1.Clinical assessment scores
Answer: NEWS2 = 6
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 97% → 0
on oxygen → 2
SBP 118 mmHg → 0
HR 76/min → 0
unresponsive (U) → 3
T 35.5 °C → 1
Add
NEWS2 = 0 + 0 + 2 + 0 + 0 + 3 + 1 = 6
Answer
NEWS2 = 6
2.Clinical assessment scores
Answer: obesity class II
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 = 111/1.77² = 35.43
Category
obesity class II
Answer
obesity class II
3.Arterial blood gas interpretation
Answer: PaCO₂ = 23 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 = 1.5·10 + 8 = 23 mmHg
range: 21–25 mmHg
Answer
PaCO₂ = 23 mmHg
4.Arterial blood gas interpretation
Answer: delta ratio = 0.3846
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 = 140 − (112 + 11) = 17
Delta ratio
(17 − 12)/(24 − 11) = 5/13 = 0.3846
Answer
delta ratio = 0.3846
Below 1: an added normal anion gap acidosis.
5.Nursing fundamentals
Answer: C · Gradual rewarming with blankets and warm surroundings
Why this is the answer
Gradual passive rewarming with blankets, a warm room and warm drinks if they can swallow is safe for mild hypothermia. Direct heat can burn and rapid rewarming can be dangerous.
Answer
C · Gradual rewarming with blankets and warm surroundings
6.Nursing fundamentals
Answer: B · Touch signals reduce pain signals passing up the spinal cord
Why this is the answer
The gate control theory proposes that input from touch fibres "closes the gate" in the dorsal horn of the spinal cord, reducing pain transmission. This underlies massage and TENS.
Answer
B · Touch signals reduce pain signals passing up the spinal cord
7.Nursing math & unit conversions
Answer: m = 4.72 kg
Household measures and weight: nursing exams use rounded equivalents: 1 teaspoon (tsp) = 5 mL, 1 tablespoon (tbsp) = 15 mL = 3 tsp, 1 fluid ounce (fl oz) = 30 mL = 2 tbsp, and 1 cup = 8 fl oz = 240 mL. For weight, 1 kg = 2.2 lb and 1 lb = 16 oz; for length, 1 inch = 2.54 cm. Set the conversion up so that the unit you do not want cancels out.
Ounces to pounds
6 oz/16 = 0.375 lb
10 + 0.375 = 10.38 lb
Pounds to kilograms
m = 10.38/2.2 = 4.716 ≈ 4.72 kg
Answer
m = 4.72 kg
8.Nursing math & unit conversions
Answer: D = 9.54 mg/h
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.
Set up the chain
D = 3 mcg/kg/min × 53 kg × (60 min/1 h) × (1 mg/1000 mcg)