co2 changes are very serious and affect the neurodevelopmental state of neonates.

1. CO2 THE OTHER FACE OF THE COIN
(FLACTUATING CO2 LEVELS AND
NEURODEVELOMENTAL OUTCOME OF
NICU GRADUATE)
• BY
• PROF :
• OSAMA ABOUELFOTOH ELFIKY.
• BENHA FACULTY OF MEDICINE

2. TWO ARTERIAL BLOOD GASES SHOWED ABNORMAL
CO2 AND O2 LEVELS
DO YOU THINK WHICH ARE MORE SERIOUS CO2 OR O2
ABNORMALITIES?
B
A

3. • O2 and CO2 are the two gases involved in the
• Process of respiration.
• On reading blood gases all of us are interested
• in O2 level monitoring and interpretation
• All of us know the hazards of hypoxia as well
• As O2 toxicity
• Few of us are aware by such changes
• Of CO2 levels and their hazards

4. • Many of us think that fluctuating CO2 levels
• Are not harmful because we may use various
• CO2 levels in therapeutic intervention of some
• Neonatal disorders as:
a) Permissive hypercarbia as a protective
• measure against ventilator induced lung
• injuries

5. • b) Hypocapnea is used as one of the
measures to lower intracranial tension

6. ULTRASONGRAPHY AND BRAIN
IMAGING STUDIES

8. Transverse T2 weighted FSE image of an
infant at 27 weeks GA showing bilateral
germinal layer haemorrhages (arrows).

10. CHILREN WITH CEREBRAL PALSY

13. severe intraventricular hemorrhage and white
matter injury, both of which are contributory
factors in the development of cerebral palsy.

14. CEREBRAL BLOOD FLOW AND THE
EFFECT OF CO2 LEVELS

17. Factors affecting cerebral blood flow :
• Arterial CO2 and O2 tensions are major
determinants of CBF .
• The most potent acute regulator of cerebral
blood flow is PaCO2, and it can have more
impact than increases in mean blood
pressure.10,23
In healthy adult normocapnic volunteers, 10 mmhg
increase in arterial CO2 tension induces a
concomitant 30% change in CBF

18. • hypocapnia can lead to vasoconstriction and
significantly decreased cerebral blood flow.8–
10
• Hypercapnia can increase cerebral
vasodilation and cerebral blood flow
• .
• Progressive increases in the PaCO2 level can
also impair the auto regulation of cerebral
blood flow and may lead to ischemic damage
of the neonatal brain.2,8,9
•

19. CO2 LEVEL AND CEREBRAL BLOOD
FLOW

21. CO2 LEVEL THAT OFFER OPTIMUM
NEUROPROTECTION

22. Vannucci et al postulated a significant
neuroprotective effect of CO2 in preterm rats
at a level PaCO2 of 45–55 mm
There are two studies by Mariani et al and
Carlo et al postulated possible neurologic
safety of permissive hypercapnia of 45–50 mm
Hg but not 50 –55 mm Hg in the first 7
postnatal days

23. Resulting in increased delivery of O2 and
increased cerebral blood flow preventing
cerebral ischemia.
Possible explanations include a shift of the
oxygen– hemoglobin dissociation curve to
the right.

24. HYPOCAPNEA AND ITS HAZARDS

25. Hypocapnia in premature infants is associated
with poor neurodevelopmental outcome,
including PVL, IVH, and cerebral palsy .
possibly due to cerebral vasoconstriction,
decreased cerebral blood flow (CBF), and
decreased cerebral oxygen delivery.
Therefore, prevention of hypocapnia must also
be a primary objective in the management of
these infants

26. WHITE MATER LESIONS AND DURATION
AND SEVERITY OF HYPOCAPNEA

27. • Preterm infants exposed to severe (arterial
Pco2 < 15 mm Hg) hypocapnia, even if only
for a brief period, may develop considerable
long-term neurologic abnormalities
compared with matched, non exposed
controls

28. 1-Babies with chronic lung disease with a
high compensatory PaCO2 but whose
PaCO2 drops rapidly when they require
reventilation.
A rapid fall in PaCO2 even to normal levels
may cause considerable cerebral under
perfusion
. 2-With changing lung compliance after
artificial surfactant administration .
• Take care that hypocapnea can occur rapidly in:

29. Abrupt termination of hyperventilation
results in reactive hyperemia, which may
cause intracranial hemorrhage, particularly
in premature infants

31. HYPERCAPNEA AND ITS HAZARDS

32. Normocapnic (PaCO2 35– 45 mm Hg),
Mild hypercapnia (PaCO2 45–55 mm Hg),
Moderate hypercapnia (PaCO2 55– 65 mm Hg),
Severe hypercapnia (PaCO2 > 65 mm Hg).
RESPIRATORY CARE Paper in Press. Published on April 03, 2018 as
DOI: 10.4187/respcare.05801
Although mild hypercapnia appears safe,
moderate hypercapnia may increase neurologic
risk and provide little pulmonary benefit.

33. • Permissive hypercapnia is a ventilation
strategy widely used to minimize the
iatrogenic lung injury that can occur with
mechanical ventilation.

34. • Hypercapnic cerebral vasodilation can also
cause an increase in cerebral blood flow that
may contribute to the development of IVH.8
• Obvious PaCO2 elevation leads to:
• an increase in blood brain barrier permeability.
cerebral interstitial edema.
• an increase in CBF.

35. If the PaCO2 elevation is associated by tissue
ischemia as in cases of hypoxic ischemic insults,
intracellular acidosis can enhance brain cell
metabolism and worsen tissue and cell damage
• CBF autoregulation loss
• intracranial hypertension
• sometimes even intracraninal
hemorrhage

36. FLACTUATING CO2 LEVELS IS IT
HAZARDOUS?

37. • Hypercapnia, hypocapnia, fluctuations in
PaCO2, and acidosis have all been positively
associated with intraventricular hemorrhage
(IVH), periventricular leukomalacia, and poor
neurodevelopmental outcomes in preterm
neonates.10–13

38. Infants evaluated as a secondary analysis
of the SUPPORT trial26 :
demonstrated that greater fluctuation in
PaCO2 was significantly associated with
IVH and neurodevelopmental impairment
at 18–22 months corrected .

39. TAKE AWAY MESSAGE

40. Both extreme hypercapnia (PCO2>60
mmHg) and hypocapnia (PCO2 <35
mmHg) appear to cause brain injury and
should be avoided [64][65].
The Canadian Paediatric Society gives permission to print single copies of this document from our website. For
permission to reprint or reproduce multiple copies, please see our copyright policy.
Principal author(s)
Michelle Ryan, Thierry Lacaze-Masmonteil, Khorshid Mohammad; Canadian Paediatric Society, Fetus and
Newborn Committee
Paediatr Child Health 2019 24(4):276–282.

41. Monitoring PCO2 via blood gases or
transcutaneous or end-tidal CO2 is
recommended for infants born at
≤32+6weeks GA, with a goal of achieving
PCO2 levels of 45 mmHg to 55 mmHg in
the first 72 hours postdelivery (level of
evidence: 1b).
The Canadian Paediatric Society gives permission to print single copies of this document from our website.
For permission to reprint or reproduce multiple copies, please see our copyright policy.
Principal author(s)
Michelle Ryan, Thierry Lacaze-Masmonteil, Khorshid Mohammad; Canadian Paediatric Society, Fetus and
Newborn Committee
Paediatr Child Health 2019 24(4):276–282.

42. REFERENCES