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Cardiovascular and Respiratory Systems

Cord Blood Gases

 

Overview

            Definitions

            Normal Values

            Physiology

            Cases

            Interventions

            Review

 

What is a blood gas?

            pH

            pCO2

            pO2

            Bicarb

            Base

 

            pH, pCO2, pO2 are analyzed, other values are calculated

            Indications: fetal distress, low Apgar

 

Anatomy - what goes where

            oo                                          (photo)

            Technique: cord or placenta     (photo)

 

Normal values

            for you

            for a healthy term baby

            (for a premature baby)

            for a fetus

 

    mean (± 2SD)         pH          pCO2        pO2            HCO3            BE

    V:                 7.35 (±0.05)    38 (±6)        29 (±6)        20 (±2)        -4 (±2)
    A:                 7.28 (±0.05)    49 (±8)        18 (±6)        22 (±3)        -4 (±2)
 

Acidosis

            pH

            pCO2

            Respiratory verus Metabolic

 

Hypoxia

 

Cases
 
Case 1

UV: 7.04 55 14 -5

UA: 7.06 53 13 -5

pH<0.04; 18% are <0.02

Case 2

UV: 7.05 65 30

UA: 7.15 55 35

Case 3

UV: 7.50 20 92 -4

UA: 7.26 50 11 -5

Case 4

UV: 6.83 100 10 16 -23

UA: 6.79 110 6 16 -25

What do you see?

What is the differential diagnosis?

                        19 y/o mother G2P1 Ab1, ~32 weeks by poor dates with preterm labor & diffuse abdominal pain x 4 hours

                        Hx: Cocaine use, last taken day of admission

                        Uterine contractions, q 1min, associated with repetitive late decels

                        Delivery by emergent C/S with 50% abruption—thick mec, 2500g baby

                        Apgars 1/2/4

 

                        What is the diagnosis?

                        UPI; Hallmark: equal arterial and venous derangements of pH, pCO2, pO2

 

            Case 5. UV: 7.20/54/35/-7

                        UA: 6.96/104/35/-13

                        What do you see?

                        Ddx?

 

                        39 y/o Mother G1P1 Ab0 at 38 weeks EGA

                        SROM, clear fluid-mild ctrx

                        FHR ~140 bpm, good variability; Pitocin for FTP

                        severe variable decels, pit D/C’d

                        severe variables recurred

                        Terb with good recovery; variables recurred

                        FHR suddenly fell into 60’s

                        stat C/S

                        single tight loop, clamped, cut, removed.

                        Resuscitation: suctioning, stim, and very brief bag-mask PPV with 100% O2

                        Apgars 3/9; BW 2951g

 

                        What's the diagnosis?

                        Venous occlusion; Hallmark: wide difference in pH (over 0.10) and pCO2

 

            Case 6. 20 y/o mother G3P1 Ab 1, 38 weeks in active labor

                        Delivery: Breech, non-pulsatile cord protruding from vagina

                        emergent vaginal delivery with forceps.

                        Male infant, Apgars 0/0/0

                        On further questioning, mother felt a gush of water and

                        “something funny near her leg” while in transit to the hospital

                        exact time from cord prolapse to arrival unknown (~20min)

                        baby UVC gas: 6.68/120/6/-30

 

                        Diagnosis?

                        UV: 7.24/55/20/-5

                        UA: 7.10/71/8/-10

                        What is going on?

 

                        Cord prolapse may result in occlusion of the UV or occlusion of both UV and UA’s

                        Occluded vessel only reflects status prior to occlusion

 

            Case 7. UV: 7.35/48/21/-1

                        UA: 7.31/52/14/-1

 

                        What do you see?

                        Apgars 3 and 6

 

                        What's the Ddx?

                        HIE; Hallmark: decreased extraction, hypoxia

 

 

            Case 8. 22 y/o mother G3P2 Ab0, Rh isoimmunization, early in preg, serum Rh titer 1:64

                        at 25 wks, developed ascites and pericardial effusion; 25mL PRBC’s Tx’d, cordocentesis

                        Cordocentesis at 27 and 29 weeks

                        At 31 wks, fetal Hct 26%

                                    got 55mL PRBC’s through UV

                                    brief brady, after recovery got another 20mL PRBCs

                                    then needle became dislodged; final Hct not obtained

                                    1 hr later: fetal tachycardia, poor variability, followed by a sudden decel to 50bpm

                                    Emergent C/S

                                    Apgars 2/6/7

                                   

                                    -UV: 7.04/51/36/-18

                                    -UA: 7.26/47/61/-6

 

                                    What's going on?

 

                                    Follow-up CBG: 7.33/42/41/-4

Interventions

            ABC:    Support maternal oxygenation and perfusion to optimize placental performance

                        May need to deliver the baby

                        Resuscitation

                                    Ventilation

                                    Increasing oxygen carrying capacity

                        Addressing underlying causes of acidosis

            D: Cooling

Review

            Operator Errors

                        Same vessel

                        Switched labels

                        Air Bubble

            Pathology

                        Uretoplacental Insufficiency

                        Cord Flow Problems

                        Stretching

                        Cord Prolapse

                        HIE

                        Cordocentesis

Questions

References
    Pomerance, Jeffrey, 2012 Interpreting Umbilical Cord Blood Gases: For Clinicians Caring for the Fetus Or Newborn
    ACOG
    NRP
 
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NOTES

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Case 1,2,3: Same, Switched, Bubble
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Case 4 UPI

19 y/o mother G2P1 Ab1, ~32 weeks by poor dates with preterm labor & diffuse abd pain x 4 hours

Hx: Cocaine use, last taken day of admission

Uterine contractions, q 1min, associated with repetitive late decels

Delivery by emergent C/S with 50% abruption—thick mec, 2500g baby

Apgars 1/2/4

 

V: 6.83/100/10/16/-23

A: 6.79/110/6/16/-25

 

Uretoplacental insufficiency

BE better reflects metabolic acidosis or alkalosis than bicarb

            in the face of either high or low pCO2

                        CO2 + H20 <-> HCO3 + H

Hallmark: abnl UV values & approx equal derangements of both UV and UA

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Case 5 UVO

 
Impaired Cord Blood Flow

            -Stretch (S)

                        >>short cord

                        >>relatively short cord-fundal implantation

                        >>nuchal cord or cord around another

                            structure (functionally short)

                        >>True knot (S & Compression)

                        >>Descent of fetus

                        >>Shoulder dystocia (possible)

                        >>Breech, trapped head (S & Compression)

Impaired Cord Blood Flow

            -Compression (C) 

                        Kinking                          Torsion

                        True Knot (S &C)            Cysts

                        Entwining (Mo/Mo)          Shoulder dystocia

                        Hematoma                      Stricture

                        Prolapsed cord (overt or occult)

                        Breech, trapped head

 

39 y/o Mother G1P1 Ab0 at 38 weeks EGA

SROM, clear fluid-mild ctrx-FHR ~140 bpm, good variability-Pit for FTP-severe variable decels, pit D/C’d-severe variables recurred-Terb with good recovery-variables recurred-FHR suddenly fell into 60’s-stat C/S-BW 2951g-CAN, single tight loop-clamped, cut, removed.

Resuscitation: suctioning, stim, and very brief bag-mask PPV with 100% O2

Apgars 3/9

Umbilical Vein Occlusion (UVO)

            -UV: 7.20/54/35/-7

            -UA: 6.96/104/35/-13 (why UA & UV needed)

                        >>Vein much easier to occlude then artery

                                    -thinner muscle wall

                                    -mean blood pressure –V:A 5/50mmHG

                        >>V-A pH diff- How wide is too wide?

                        >>Venoarterial pHs>0.10-susp UV occlusion

Hallmark of UVO: widened V-A pH and pCO2 diff

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Case 6 total occlusion
 

20 y/o mother G3P1 Ab 1, 38 weeks in active labor

Delivery: Breech, non-pulsatile cord protruding from vagina-emergent vaginal delivery with Piper forceps.

Male infant, Apgars 0/0/0

On further questioning, mother felt a gush of water and “something funny near her leg” while in transit to the hospital-exact time from cord prolapse to arrival unknown (~20min)

 

Cord Prolapse

            -UV: 7.24/55/20/-5

            -UA: 7.10/71/8/-10

            -Apgars=0/0/0

            -UVC: 6.68/120/6/-30

            >>Cord prolapse may result in occlusion of the UV or occlusion of both UV and UA’s

            >>Occluded vessel only reflects status prior to occlusion

 

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Case 7 HIE

 

Low Apgar Scores w/o Current Asphyxia

            -UV: 7.35/48/21/-1

            -UA: 7.31/52/14/-1

            -Apgars=3/6

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Case 8 = 2

22 y/o mother G3P2 Ab0- 31 w 3d, Rh isoimmunization-early in preg, serum Rh titer 1:64- 23 wks, change OD, mid-zone II- 25 wks, ascites and pericardial effusion-25mL PRBC’s Tx’d, cordocentesis

Txs, cordocentesis at 27 and 29 week- 31 wks, cordocentesis- fetal Hct 26%- after 55mL PRBC’s infused through UV, brief brady- after recovery, another 20mL PRBC’s infused- needle became dislodged, final Hct not obtained- 1 hr later, fetal tachycardia with poor variability, followed by sudden decel to 50bpm- EMERGENT C/S

Apgars 2/6/7

            -Follow-up CBG: 7.33/42/41/-4

 

Fetal Deterioration During Cordocentesis

            -UV: 7.04/51/36/-18

            -UA: 7.26/47/61/-6

 

            “Corrected”

                        -UV: 7.26/47/61/-6

                        -UA: 7.04/51/36/-18

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The End

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