Nota Perubatan

Category: Public: Survival kit

  • Haemoglobin (Hb) Cutoffs

    Haemoglobin cutoffs to define anaemia in individuals and populations

    📌 Children

    • 6 – 23 months: Hb <10.5 g/dL
    • 24–59 months: <11.0 g/dL
    • 5 – 11 years: <11.5 g/dL
    • 12–14 years, nonpregnant girls: <12.0 g/dL
    • 12–14 years, boys: <12.0 g/dL

    📌 Adults

    • 15–65 years, nonpregnant women: <12.0 g/dL
    • 15–65 years, men: <13.0 g/dL

    📌 Pregnancy

    • First trimester: <11.0 g/dL
    • Second trimester: <10.5 g/dL
    • Third trimester: <11.0 g/dL

    Haemoglobin cutoffs for severity of anaemia

    Population Normal (g/dL) Mild anaemia (g/dL) Moderate anaemia (g/dL) Severe anaemia (g/dL)
    Children
    6 – 23 months ≥10.5 9.5–10.4 7.0–9.4 <7.0
    24–59 months ≥11.0 10.0–10.9 7.0–9.9 <7.0
    5–11 years ≥11.5 11.0–11.4 8.0–10.9 <8.0
    12–14 years, non-pregnant girls ≥12.0 11.0–11.9 8.0–10.9 <8.0
    12–14 years, boys ≥12.0 11.0–11.9 8.0–10.9 <8.0
    Adults
    15–65 years, non-pregnant women ≥12.0 11.0–11.9 8.0–10.9 <8.0
    15–65 years, men ≥13.0 11.0–12.9 8.0–10.9 <8.0
    Pregnant
    First trimester ≥11.0 10.0–10.9 7.0–9.9 <7.0
    Second trimester ≥10.5 9.5–10.4 7.0–9.4 <7.0
    Third trimester ≥11.0 10.0–10.9 7.0–9.9 <7.0
    No matches found.

    Haemodilution in pregnancy

    • Maternal physiological adaptation to pregnancy: plasma volume expansion exceeds the increase in red blood cell mass, resulting in functional hemodilution. There is a drop in the concentration of red blood cells, hemoglobin, and hematocrit.
    • Hemodilution is most pronounced during second trimester. Hence, WHO sets a lower hemoglobin threshold for second trimester compared to the first and third.
    • In third trimester, plasma volume continues to increase, but at a slower rate. The discrepancy between plasma and RBC mass narrows, and hemoglobin levels stabilize

    Reference

    1. WHO Guideline on haemoglobin cutoffs to define anaemia in individuals and populations https://www.who.int/publications/i/item/9789240088542

  • Thyroid Function Test (TFT) Interpretation

    Imagine this is a thyroid function test (TFT) result that you trace from the lab information system (LIS):
    – TSH 100 mIU/L (normal range 0.350 – 0.490)
    – Free T4 <5.41 pmol/L (normal range 9.0 – 19.1)
    What is the diagnosis based on the TFT result? [answer]

    Interpretation

    🔼TSH 🔽FT4: hypothyroidism
    🔼TSH ↔️FT4: subclinical hypothyroidism
    🔼TSH 🔼FT4: TSH secreting tumour / thyroid hormone resistance

    🔽TSH 🔼FT4 or FT3: Hyperthyroidism
    🔽TSH ↔️FT4: subclinical hyperthyroidism
    🔽TSH 🔽FT4: central hypothyroidism (i.e. due to pituitary / hypothalamic disorders) / ‘sick euthyroid’ syndrome

    ↔️TSH 🔼/🔽FT4: amiodarone treatment / non-thyroidal Illness / pituitary or hypothalamic dysfunction / assay interference

    Keys:
    🔼: high
    🔽: low
    ↔️: normal

  • Arterial Blood Gas (ABG) Interpretation

    Interpreting arterial blood gas (ABG) could be initially challenging for medical students / House Officers. It is important to master ABG interpretation for management of patients’ acute conditions.

    Remember the normal range for ABG parameters

    • pH: 7.35-7.45
    • PaO2: 80-100 mmHg
    • PaCO2: 35-45 mmHg
    • HCO3-: 22-26 mmol/L
    • Base Excess (BE): -2 to +2
    • SaO2: 95-100%

    Examples of what base excess (BE) tells us:

    • BE +4: Metabolic alkalosis // compensated respiratory acidosis
    • BE -4: Metabolic acidosis // compensated respiratory alkalosis

    Step 1: Evaluate pH

    • Acidaemia: Acidosis is present
    • Alkalaemia: Alkalosis is present
    • Normal pH: Either no acid-base issue or full compensation

    Step 2: Assess respiratory (PaCO2) & metabolic (HCO3-) components

    • ↑ PaCO2: Respiratory acidosis
    • ↓ PaCO2: Respiratory alkalosis
    • ↓ HCO3-: Metabolic acidosis
    • ↑ HCO3- : Metabolic alkalosis

    Step 3: Check for Compensation – Is the body trying to correct the imbalance?

    • Uncompensated: pH abnormal + no compensatory change in PaCO2/HCO3
    • Partially compensated: pH still abnormal but compensatory mechanism is active
    • Fully compensated: pH normal + PaCO2/HCO3 altered to compensate
    Some equations related to compensation:
    ☘️ Winter's Formula – Expected PaCO2 in metabolic acidosis = (1.5 x HCO3-) + (8±2) 

    ☘️ Point Seven Plus Twenty Rule – Expected PaCO2 in metabolic alkalosis = (0.7 x HCO3-) + (20±5) 

    ☘️ 1-2-4-5 Rule – Expected HCO3- changes based on acute vs. chronic respiratory acidosis/alkalosis

    Step 4: Evaluate PaO2 for oxygenation status

    • Type 1 respiratory failure: PaO2 <60 mmHg + normal/low PaCO2
    • Type 2 respiratory failure: hypoxaemia + hypercapnia (PaCO2 >45 mmHg)

    Step 5: Final impression

    • Once all elements are assessed, define the overall disorder (e.g., partially compensated metabolic acidosis).

  • ECG Interpretation

    Imagine this: It’s 2 AM, you’re the on-call Medical Officer or night shift House Officer, and the nurse hands you an ECG. The patient complained of sudden onset of chest pain and palpitations. Worst Case Scenario: You hesitate, unsure of what you’re seeing. The delay leads to missed intervention, and suddenly, your patient crashes.

    (1) Check ECG details

    • Confirm patient name & date to ensure is the right ECG
    • Check calibration. Standard settings: 25 mm/s, 10 mm/mV

    (2) Rhythm – Is it sinus rhythm or something else?

    • P waves before every QRS?
      • If Yes = Sinus rhythm
    • No P waves or irregular rhythm?
      • Consider atrial fibrillation, atrial flutter, or junctional rhythms
    • PR interval: 0.12-0.20 sec

    (3) Calculate the heart rate (based on rhythm regularity)

    • Regular rhythm: Use the 300 Rule: 300 ÷ number of large squares between two R waves.
    • Irregular rhythm: Count R waves in 6 seconds (30 big boxes) and multiply by 10.
    • Normal range: 60-100 beats per minute

    (4) Determine axis

    Lead I & aVF QUADRANT approach:

    • Normal axis: both positive
    • Left axis deviation: Lead I positive, aVF negative
    • Right axis deviation: Lead I negative, aVF positive

    (5) ST Segment & T Waves — look for ischaemic changes

    • Any ST Elevation?
      • Consider STEMI (especially if it occurs at contiguous leads). Look for reciprocal changes.
    • Any ST Depression?
    • Any T wave inversion?

    (6) Look for heart block

    Bundle branch block

    • Left Bundle Branch Block (LBBB): “WiLLiaM”
      • V1: W-shaped (deep S wave)
      • V6: M-shaped (broad, notched R wave)
    • Right Bundle Branch Block (RBBB): “MaRRoW”
      • V1: M-shaped (rSR’ pattern, “rabbit ears”)
      • V6: W-shaped (deep S wave)

    Atrioventricular block

    • First degree heart block: PR interval >200 ms (5 small boxes), but all P waves are followed by QRS complexes; regular ventricular rate
    • Second-degree heart block
      • Mobitz Type I: Progressive lengthening of PR interval, followed by a non-conducted P wave (a QRS complex is dropped), i.e., a beat is skipped
      • Mobitz Type II: Sudden dropped QRS complexes without prior PR prolongation. (PR interval is constant, with intermittent non-conducted P waves)
    • Third-Degree Heart Block (Complete heart block): No relationship between P waves and QRS complexes

  • Commonly Used Formula

    Corrected calcium

    • Corrected calcium = 0.02 x (40- albumin level) + calcium level
      • Units: calcium in mmol/L; albumin in g/L
    Example:
    Serum calcium 1.98 mmol/L
    Serum albumin 23 g/L

    1⃣ 
    Normal albumin - current albumin
    40 - 23 = 17

    2⃣ 
    1⃣ x 2 ÷ 100 
    17 x 2 ÷ 100 = 0.34

    3⃣ 
    2⃣ + serum calcium level
    0.34 + 1.98

    Answer: Corrected serum calcium = 2.32 mmol/L

    Calculation of potassium deficit

    • Potassium deficit (g) = [(4 – current potassium level) × 0.4 × bodyweight]/13.4]
      • Unit: potassium in mmol/L
    • Clinical significance: for fast correction of potassium in hypokalaemia cases

    Anion gap

    • Anion Gap = (Na+ + K+) – (Cl –+ HCO3)
      • Units: all in mmol/L
      • Normal range: 8 – 16
    • Clinical significance: to differentiate between high anion gap metabolic acidosis (HAGMA) and normal anion gap metabolic acidosis (NAGMA)

    Calculated plasma osmolality

    • Calculated plasma osmolality = (2 x Na+ ) + Urea + Glucose
      • Units: all in mmol/L
    • Clinical significance: part of the diagnostic criteria for Hyperglycaemic hyperosmolar state (HHS)
      • Severe dehydration
      • Marked hyperglycaemia (plasma glucose >30 mmol/L)
      • Serum osmolality >320 mOsm/kg

  • Normal Range of Common Lab Tests (Adults)

    Disclaimer: Normal ranges may vary between laboratories; the values provided here are for reference only.

    Full blood count (FBC)

    Parameter Normal Range
    White blood cell, x10^9 4 – 10
    Haemoglobin concentration (Hb), g/dL Men: 13.0 – 17.0 Women: 12.0 – 15.0
    Haematocrit (HCT), % Men: 40 – 50 Women: 36 – 46
    Platelet (PLT), x10^9 150 – 400
    Reticulocytes 50 – 100 x10^9/L (0.5 – 2.5%)
    Mean corpuscular volume (MCV), fl 80 – 100
    Mean cell haemoglobin (MCH), pg 27 – 30
    No matches found.

    Renal profile (RP)

    Parameter Normal Range
    Urea, mmol/L 2.5 – 6.7
    Creatinine, μmol/L 70 – 100
    Sodium, mmol/L 136 – 145
    Potassium, mmol/L 3.5 – 5.1
    Chloride, mmol/L 97 – 108
    No matches found.

    Electrolytes – calcium, magnesium, phosphate

    Parameter Normal Range
    Calcium (Ca), mmol/L 2.1 – 2.65
    Magnesium (Mg), mmol/L 0.7 – 0.9
    Phosphate (PO4), mmol/L 0.8 – 1.45
    No matches found.

    Liver function test (LFT)

    Parameter Normal Range
    Bilirubin, μmol/L 3 – 20
    Alanine aminotransferase (ALT), IU/L 5 – 35
    Aspartate transaminase (AST), IU/L 5 – 35
    Alkaline phosphatase (ALP), IU/L 30 – 130 (non-pregnant adults)
    Albumin, g/L 35 – 50
    No matches found.

    Arterial blood gas (ABG)

    Parameter Normal Range
    pH 7.35 – 7.45
    pCO2, mmHg 35 – 45
    pO2, mmHg 80 – 100
    Bicarbonate (HCO3), mmol/L 22 – 26
    Base excess (BE) -2 to +2
    SaO2, % 95 – 100
    No matches found.

  • Hypomagnesaemia

    Introduction

    • Normal range: 0.7 – 0.9 mmol/L

    Fast correction

    • IV MgSO4 2.47 g in 100 mL NS over 1 hour
    • Repeat Mg 1 hour post correction (not a fixed rule)

  • Hypokalaemia

    “Dr., this patient X has hypokalaemia, potassium 2.5. Can I fast correct with IV KCl 2g stat?”

    Introduction

    • Normal range of serum potassium: 3.5 – 5.1 mmol/L
    • Severity of hypokalaemia:
      • Mild: 3.1 – 3.5 mmol/L -> oral potassium supplement, then repeat RP tomorrow
      • Moderate: 2.5 – 3 mmol/L -> ECG + consider fast correction with IV KCl, then repeat serum potassium after 1 hour
        • ±IV KCl maintenance in drip / oral supplementation
      • Severe: <2.5 mmol/L -> ECG + fast correction with IV KCl, then repeat serum potassium after 1 hour
        • ±IV KCl maintenance in drip / oral supplementation

    *There is no fixed rule on the treatment. Treatment must be aligned with clinical judgement.

    Calculation of potassium deficit & requirement

    (i) Potassium deficit

    Potassium deficit (g) = [(4 – current potassium level) × 0.4 × bodyweight]/13.4]

    • 1 g KCl contains 13.4 mmol potassium & 13.4 mmol chloride (as shown in the picture above)
    • 1 vial = 10 mL KCl = 1 g KCl

    (ii) Potassium requirement

    Potassium daily requirement (g) = 1 mmol/kg/day

    Example

    Patient X, weight 60kg, serum potassium 2.5 mmol/L

    • Deficit: [(4 – 2.5) x 0.4 x 60] / 13.4 = 2.68 g
    • Daily requirement: 1 x 60 / 13.4 g = 4.47 g
    • Correction of deficit: fast correct with IV KCl 2g in 200 mL NS over 2 hours
      • Repeat serum potassium post correction
    • Daily requirement:
      • If the patient is on IV drip maintenance e.g. 4 pints NS / 24 hours, may add 1g KCl in each pint NS (the calculated requirement is 4.47 g per day. Hence 1g in each pint is applicable.)
      • If the patient is not on IV drip and having good oral intake, add oral potassium supplement (e.g. Tab Slow K 1.2 g TDS for 3 days), and encourage oral intake

    Medications for hypokalaemia

    • Intravenous – IV KCl, examples of administration:
      • IV KCl 1g in 100 mL NS over 1 hour
      • IV KCl 2g in 200 mL NS over 2 hours
    • Oral:
      • Tab Slow K e.g. 1.2 g TDS
      • Mist KCl e.g. 15 mL TDS

  • Hyperkalaemia

    Introduction

    • Normal range of serum potassium: 3.5 – 5.1 mmol/L
    • Severity of hyperkalaemia:
      • Mild: 5.5 – 5.9 mmol/L
      • Moderate: 6 – 6.4 mmol/L
      • Severe: ≥6.5 mmol/L
    • One very common cause of ‘hyperkalaemia’ is lysed sample. Remeber to check lab formal report whether there is any documentation regarding lysed sample. In that case, it is better to repeat RP / potassium first before starting treatment for the ‘hyperkalaemia’.
    • Not all hyperkalaemia cases require fast correction with lytic cocktail!
    • Moderate / Severe hyperkalaemia warrants fast correction, but also depends on clinical condition

    Lytic cocktail regime

    • IV Calcium gluconate 10% over 10 minutes (ideally attach with cardiac monitor during administration), then
    • IV Dextrose 50% 50 mL , then
    • IV Actrapid 10 units (1 mL)

    Repeat serum potassium 1 hour post lytic cocktail, may require repeated lytic cocktail / urgent haemodialysis if persistent severe hyperkalaemia

    Oral Kalimate

    • Dose example: PO Kalimate 15 g TDS for 3 days
    • Do not give oral Kalimate for long term due to risk of bowel necrosis

    Flowchart of emergency management of hyperkalaemia

    Source: Malaysian Consensus on the Management of Acute and Persistent Hyperkalaemia: A Multidisciplinary Approach 2024

  • Hypercalcaemia

    “49 years old man, no known medical illness, presented with lethargy for 3 weeks, loss of appetite for 2 weeks, and constipation for 3 days. At ED, noted corrected serum calcium 3.98 mmol/L”

    Introduction

    • Normal range of serum calcium: 2.1 – 2.65 mmol/L
    • Severe hypercalcaemia = Serum calcium >3.5 mmol/L
    • Acute therapy is warranted if serum calcium >3 mmol/L or severe symptoms
    • Patients with severe hy[ercalcaemia are usually dehydrated during initial presentation

    Investigations

    (i) Initial investigations

    • FBC, RP, Ca, Mg, PO4
    • LFT (look for ALP level)
    • Thyroid function test
    • iPTH (intact parathyroid hormone)

    (ii) Other investigations to be considered

    • If suspect PTB / TB related hypercalcaemia: CXR, Sputum AFP x1, x2, x3; Sputum MTB GeneXpert
    • If suspect malignancy (e.g. multiple myeloma): urine protein electrophoresis, serum protein electrophoresis, skeletal survey, full blood picture,
    • KUB X-rays, KUB USG e.g. if AKI not resolving despite on hydration — TRO obstructive uropathy

    Acute therapy of severe hypercalcaemia

    1) Hyperhydration

    • Initially 300 – 500 mL normal saline over 1 hour, sometimes up to 10 – 20 mL/kg over 1 hour
    • Followed by 3 – 4L (=6 – 8 pints) normal saline over 24 hours
    • Correct electrolyte abnormality e.g. IV KCl maintenance / fast correction for hypokalaemia; IV MgSO4 for hypomagnesaemia
    • Hyperhydration with 3 – 4L normal saline over 24 hours can be given for 2 – 3 days, depending on clinical response and assessment
      • The patient must be reassessed (e.g. after 24 hours of fluid) to determine whether fluid can be titrated down or maintained. Check input/output balance, RP, and electrolytes.
      • How much fluid to be given depends on patient’s hydration status (e.g. from IVC diameter & collapsibility; presence of GI loss, amount of oral intake, urine output; CVP monitoring if available), haemodynamic status (BP, HR), and whether patient having fluid restriction (e.g. CCF, ESRF)
    • Normal saline helps to restore extracellular fluid (i.e. rehydrate the patient) and to promote calcium excretion (Na competitively inhibits renal tubular absorption of Ca)

    2) Diuretics

    • IV Frusemide 20 – 40 mg TDS
    • DO NOT use thiazides which can reduce calcium excretion
    • IV Frusemide helps to prevent fluid overload and to further promote calcium excretion

    3) Bisphosphonates

    Examples:

    • Zoledronate (Zometa®): IV Zoledronate 4 mg over at least 15 minutes (agent of choice for malignancy-associated hypercalcaemia because it’s more potent and effective than pamidronate)
    • Pamidronate: IV Pamidronate 30 mg / 60 mg / 90 mg in 1L normal saline over 4 – 6 hours.
      • Action starts after several days and lasts for weeks to months
      • Example dose: 30 mg for Ca <3 mmol/L, 60 mg for Ca 3 – 3.4 mmol/L, 90 mg for Ca >3.4 mmol/L)
    • Useful especially if suspect hypercalcaemia due to malignancy. Bisphosphonates work by inhibiting bone resorption.
    • Prescriber category: A* (must be discussed with specialist for initiation and dosage)
    • Treatment can be repeated if hypercalcaemia recurs (usually after 2 – 3 weeks)

    4) Treatment of underlying disease / cause

    Further reading

    • Sarawak Handbook of Medical Emergencies (4th edition)
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