arterial blood gases- the other parameters that we can measure. Important clinical Cases with respect to Arterial Blood Gases

1. UNCONVENTIONAL AND ALARMING
ArTERIAL BLOOD GAS PARAMETERS

2. OVERVIEW
• Unconventional parameters
• Methemoglobinemia
• Organic acidemias
• Co-oximetry

3. Normal Values
• pH
• pO2
• pCO2
• HCO3
• sO2

4. OTHER PARAMETERS
• SODIUM
Na+-136–146 mmol/L
• POTASSIUM
K+ -3.4–4.5 mmol/L
• CHLORIDE
Cl-98–106 mmol/L
• CALCIUM
Ca2+ -1.15–1.29 mmol/L

5. OTHER PARAMETERS
• FRACTION OF METHEMOGLOBIN
FMetHb -0–1.5% (0–0.015)
• FRACTION OF CARBOXYHEMOGLOBIN
FCOHb(a) -0.5–1.5% (0.005–0.015)
• GLUCOSE
• Glucose-3.89–5.83 mmol/L (70–105 mg/dL)
• Lactate
• Bilirubin

7. Case 1
• 4-year-old unconscious boy brought to the
EMS
• History- was playing Holi with his friends
• Examination reveals shallow and irregular
respiration and central cyanosis

8. CASE 2
BLUE BABY SYNDROME

9. CAUSES
• Hereditary/ Congenital: Hemoglobin M,
cytochrome b5 reductase deficiency , NADPH
deficiency of the HMP shunt
• Acquired: multiple drugs and toxins including
aniline dyes, benzene, chloroquine, dapsone,
local anesthetic agents, naphthalene, nitrites
(including NTG and NO), primaquine,
phenazopyridine, and sulfonamides

10. Pathophysiology of
Methemoglobinemia
• Methemoglobin is an altered state of hemoglobin
in which the ferrous (Fe++) irons of heme are
oxidized to the ferric (Fe+++) state
• The ferric heme of methemoglobin are unable to
bind oxygen
• In addition, the oxygen affinity of any
accompanying ferrous heme in the hemoglobin
tetramer is increased as a result, the oxygen
dissociation curve is "left-shifted" and oxygen
delivery to the tissues is impaired

11. Pointers for early identification of
Methemoglobinemia
• High pO2 levels in the presence of Central
Cyanosis
• As levels rise above 15%, neurologic and cardiac
symptoms arise as a consequence of hypoxia
• Levels higher than 70% are usually fatal
• Treatment
• iv methylene blue
• Exchange transfusion

12. ORGANIC ACIDEMIAS
• group of rare autosomal recessive inherited
disorders
• affect both males and females
• caused by enzymes that are deficient causing an
error in protein metabolism
• causes harmful metabolites to accumulate in
blood and excreted in urine
• These affect health, growth and learning of child
• The symptoms and treatment vary between
different organic acid disorders

13. Common lab findings
• ketones in the urine
• • high levels of acidic substances in the blood,
causing metabolic acidosis
• • high blood ammonia levels
• • high levels of certain organic acids
• • low platelets
• • low white blood cells

14. CASE….
• 1 year girl child with developmental delay, came to the
EMS in critical state
• Respiratory intercurrent illness before admission which
rapidly progressed to respiratory failure
• Born at 44 weeks of gestation, with normal birth
weight- 3700g and Apgar score of 8
• Facial features- high forehead
• broad nasal bridge
• epicanthal folds
• a long smooth filtrum
• triangular mouth

15. • Laboratory studies
• Metabolic acidosis- pH 7.03
• High anion gap- 28.2
• Normal glycemic levels
• Normal blood lactate
• Recurrent episodes of metabolic acidosis with poor
response to treatment
• Intoxication ruled out and no sign of kidney disease
• Elevated levels of methylmalonic acid in urine and
Elevated levels of propyonilcarnitine in blood and urine
Maria Gica; A Rare Case of High Anion Gap
Metabolic Acidosis

16. Take home message
• Methemoglobinemia is a medical emergency,
requiring prompt management
• Inborn errors of metabolism

17. CO-OXIMETER
• It also measures concentrations of
oxygenated hemoglobin (oxyHb)
deoxygenated hemoglobin (deoxyHb or reduced Hb)
carboxyhemoglobin (COHb)
methemoglobin (MetHb)
Focus on Diagnosis: Co-oximetry; Pediatrics in Review
2007

18. CO-OXIMETER
• Absorbance of Hb derivatives by multiple
wavelengths of light
• ABG analyzers calculate, rather than measure,
saturation, and will not differentiate or identify
the contribution of dyshemoglobinemias to total
saturation. As a result, the oxygen saturation may
appear artificially high in routine blood gas
analysis.
• Rapid detection and management of CO poisoned
patients in the emergency department

19. CASE…..
• Five young mess workers aged between 20years
to 30 years after cooking food slept in a room at
around 9:00pm and they arrange a furnace and
burn coal to keep their room warm. They closed
the doors and windows.
• At 11:00pm one of them woke to go toilet but as
soon as he stood he felt dizzy and fell down.
Noise produced by his fall awakened all the
persons, they tried to open the door but could
not do so due to dizziness and some sort of
diminution of vision.
Accidental carbon monoxide Poisoning; Rama Univ. J. Med Sci 2015

20. • CO has 200 to 300 times greater affinity for
hemoglobin than that of oxygen.
• It displaces oxygen from its combination with Hb
and forms a relatively stable compound known as
carboxyhemoglobin. CO is a potent cellular toxin.
• It effectively and firmly binds to hemoglobin and
myoglobin.
• It inhibits the electron transport by blocking
cytochrome a3 oxidase and cytochrome P-450
and therefore intracellular respiration

21. CRITICAL VALUES
Test Value
• pH ≤ 7.25 or ≥ 7.6
• PCO2 ≤ 20 or ≥ 60 mmHg
• PO2 ≤ 40 mmHg
• If Pt.’s temp < 37C
• Subtract 5 mmHg Po2, 2 mmHg Pco2 and
Add 0.012 pH per 1C decrease of temperature

22. QUALITY MANAGEMENT
• Standardize procedures
• Know your instrument
• Provide written instructions
• Enforce compliance
• Educate yourself and educate others
• Monitor the quality
• Continuous improvement
lab responsibility!

23. TAKE HOME MESSAGE
• Have a look at other parameters
• Methemoglobinemia is a medical emergency,
requiring prompt management
• Inborn errors of metabolism
• Co-oximetry helps in detection of CO
poisoning
• Quality management is our responsiblity

24. THANK YOU
• me@drrittuchandel.com
• www.drrittuchandel.com