Nota Perubatan

Author: notaperubatan

  • Commonly Used Fluids in the Hospital

    IV Fluid Composition

    Intravenous Fluid Composition

    Reference table for common IV solutions. All concentrations are in mmol/L unless otherwise noted.

    Solution mOsm/L Glucose (g/L) Caloric value (kcal/L) NaCl Na⁺ Cl⁻ K⁺ Ca²⁺ Mg²⁺ Lactate ion Acetate ion Maleate ion Others
    Normal Saline (0.9%) 308 9 154 154 pH ≈ 5.5
    NaCl 3% 1026 513 513 pH ≈ 5
    Half saline (0.45%) 154 4.5 77 77
    Hartmann’s solution OR Ringer’s lactate 278 6 131 111 5 2 29 pH ≈ 6.5
    Dextrose 5% (D5%) 278 50 pH ≈ 4.3
    Dextrose 10% (D10%) 555 100 400 pH ≈ 4.3
    Dextrose 50% (D50%) 2523 500 pH ≈ 4.2
    NSD5% 585 50 200 9 154 (150) 154 (150) pH ≈ 4
    HSD5% 430 50 200 77 77 77 pH ≈ 4
    QSD1 OR 1/5 Saline D4.23% OR NaCl 0.18% D4.23% 296 42.3 170 31 (30.8) 31 (30.8)
    QSD10% OR 1/5 Saline D10% OR NaCl 0.18% D10% 615 100 400 1.8 31 (30) 31 (30)
    Sterofundin (1/1 E ISO) 304 (309) 6.8 140 127 4 2.5 1.0 24 5 pH 5.1 – 5.9
    Succinylated Gelatin 4% 274 154 120 Succinylated gelatin 40 g/L
    Mannitol 20% 1100 Mannitol 200 g/L
    pH 6.3
    Mannitol 10% 550 Mannitol 100 g/L
    pH 6.3

  • Mentzer Index

    Mentzer Index Calculator

    Mentzer Index Calculator

    Differentiate between Iron Deficiency Anemia (IDA) and Beta Thalassemia Trait.

    Mentzer Index = MCV / RBC

    Diagnostic Performance

    Based on various studies using a cutoff value of 13, the Mentzer Index is typically associated with high diagnostic accuracy:

    • Sensitivity for IDA: ~91% to 98%
    • Specificity for IDA: ~83% to 93%
    • Sensitivity for Beta Thalassemia Trait: ~83% to 93%
    • Specificity for Beta Thalassemia Trait: ~91% to 98%

    Reference Example: Role of Mentzer index for differentiating iron deficiency anemia and beta thalassemia trait in pregnant women (Note: Performance metrics may vary based on study population and cutoff value used.)

  • 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

  • Answer: Thyroid Function Test (TFT) Interpretation

    Hypothyroidism

  • 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)
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