Chapter 10

1. Chapter 10 Invasive Blood Gas Analysis and Cardiovascular Monitoring

2. Indications • Similar to that of an adult • Acid base balance, ventilation, oxygenation status • Oxyhemoglobin, intrapulmonary shunting • Response changes to therapy • Severity of diseases…. • Respiratory distress • Baby on oxygen • Shock • Sepsis • Suspected metabolic disorder • Failure to thrive (weight loss or no wt gain)

3. Pain Control Pain control during draw • Infants most likely have higher pain sensitivity • Groups older than 4 months anesthetic cream may be used • Premature newborns/neonates not intubated may use a pacifier dipped in 24% sucrose, intubated may give as drops on the tongue

4. Pain Control • The synergistic effect of the combination of sucrose and non-nutritive sucking has shown clinically effective and safe in relieving the pain of simple procedures such as venipuncture or heel stick in preterm and term infants, but further research is needed on these interventions alone and in combination with other behavioral interventions in neonates.

5. Blood Gas Sampling

6. ABG sampling sites • Brachial and femoral sites are avoided because both feed large distal networks and neither has collateral circulation • Brachial sites are hard to palpate due to large fat pad in arm, high risk in damaging nerve • Femoral site puncture never done in neonates due to proximity to vein, nerves and hip joint • Preferred site for ABG in both neonatal and pediatric populations is radial (easy to manipulate wrist and collateral circulation)

7. ABG sampling sites • Dorsalis pedis or posterior tibial artery considered if radial artery shows poor collateral circulation • Temporal artery provides an alternative site

8. ABG Sampling Sites • Umbilical artery catheter (UAC) • Clots may form on the end • Remember, it is post-ductal blood so the PaO2 may be lower than pre-ductal PaO2

9. ABG Sampling Sites: Punctures • Radial artery and temporal artery • Can be hard to hit • Brachial should not be used • NEVER use the femoral artery in an infant!

10. ABG Sampling Sites: Capillary • Easier to puncture than radial or temporal artery • PO2 may not correlate well to PaO2 • Heel has to be warmed prior to puncture to “arterialize” the site

11. Puncture Sites

12. Allen’s test • Can be modified depending on age of child • For patients who cannot follow order • For foot (dorsalis pedis and posterior tibial arteries) • a. Elevate infant’s hand. • b. Occlude both radial and ulnar arteries at wrist. • c. Massage palm toward wrist. • d. Release occlusion of the ulnar artery only. • e. Look for color to return to the hand in 6 seconds or less indicating adequate collateral supply. Do not puncture radial artery if color returns take more than 6 seconds. • f. Document inadequate collateral circulation

13. Arterial Puncture Procedure • Often more difficult and therefore less frequently done • Requires more skill, time and patience • On pediatrics, have two people, one to console the child and one to puncture • For neonates, may use a transillumination light to visulize the artery • May be performed in cases of low perfusion where a CBG is not appropriate

14. Arterial Puncture Procedure • Equipment required • 1 ml preheparinzed tuberculin syringe • 25 Gauge needle or 25 Gauge butterfly • Gloves • Alcohol wipes/ Iodine • Gauze • Needle cap • Label

18. Arterial Puncture Procedure • Position needle for arterial puncture against direction of blood flow. • Keep angle of entry shallow for superficial vessels: • a. 35 to 45 degrees for superficial artery, advance slowly/gently. May insert through artery, may have to pull back slowly if flash disappears. If resistance occurs withdraw, most likely hitting bone • b. Palpate artery using index finger and middle finger of the non dominate hand to stabilize artery • C. If using a butterfly only require enough to fill tubing, otherwise roughly 0.4-0.6 ml is required for adequate sampling. Get enough blood and run it quickly to avoid having to do it again.

19. Arterial Puncture Procedure • Contraindications are similar to adults as are hazards. • Just remember that ABG’s are not done if a less invasive means can achieve the same results; such as a CBG

20. Factors affecting arterial blood gas values • Clotting – heparin is utilized to prevent clotting of the blood sample. • The sample must be rotated/agitated to ensure adequate mixing of heparin and blood to prevent clotting. • Excessive heparin – changes the pH of the specimen. • Air contact – no air must come into contact with the blood sample. Air contact can increase the PO2 and decrease the PCO2 since there is usually more oxygen and less carbon dioxide in the air than in the • blood as measured by partial pressures. • Temperature – red cell metabolism must be minimal. The sample must be placed immediately in ice slush to slow metabolism. Red cells that are warm will continue to metabolize, giving off CO2 and consuming O2, thus affecting the blood gas values. • Steady rate – the blood should be drawn when the patient is in an equilibrated state, that is, when at least 20 minutes have elapse since any change has occurred or been made that might affect the blood gas • Significant changes are respiratory rate, tidal volume • , minute volume, Fi02, and suctioning before sampling time.

21. Capillary Blood Gas Samples Less blood required Less invasive Correlates best with pH and PaCO2

22. Capillary Blood Gas Samples Conditions of decreased venous return (right heart failure) can lead to venous congestion and higher capillary CO2 levels, increased cardiac output may lead to decreased capillary CO2 levels CBG should be correlated with an initial ABG if possible Accuracy of CBG affected by hypotension, hypothermia, hypovolemia PcO2 values are not utilized and do not correlate with arterial (unless patient has hypoxia), but may be used to trend PaO2 values

23. Procedure for CBG

25. Procedure for CBG (cont.)

26. Procedure for CBG (cont.) • Select puncture site and warm area for 5-10 minutes, use a heel warmer 42-45 C • Give a 12% to 24% sucrose solution pacifier 2 minutes before procedure • Wash hands/gloves • Remove heel warmer, clean site with alcohol or iodine, wipe dry with gauze, alcohol will hemolyze the blood • Immobolize the area by grasping the hand or foot and stabilize the area by anchoring the hand or foot on a hard surface, swaddle newborns/infants • Hold heel gently/firmly, wrap forefinger around infants upper heel and ankle while holding the arch of the foot with the thumb

27. Procedure for CBG (cont.) • Position lancet and depress – depth around 1-2 mm, only puncture once without slicing • Ease thumb pressure after the lancet is removed • Wipe away the first drop of blood which may be contaminated with intracellular, interstitial or lymphatic fluids with a dry gauze • Apply moderate pressure to the heel or digit without massaging or squeezing, until a free flowing drop of blood appears • Squeezing or “milking” the sample may cause hemolysis (more fragile RBC’s in neonates); also may cause brusing and contamination

28. Procedure for CBG (cont.) • Place tip of capillary into the droplet without touching the puncture wound • Hold the tube angled horizontally or slightly downward but avoid getting air into tube. • Fill tube as much as possible to avoid air contamination • Do not scrap the skin, may contaminate the sample with skin cells • If sample can not be analyzed immediately insert a metal mixing “flea” into the capillary tube and seal it, mix the sample by running a magnet gently back and forth (if available) or simply roll in your fingers

29. Contraindications • Need accurate assessment of oxygenation • Neonates less than 24 hours old • Decreased peripheral blood flow • Polycythemia • Avoid areas that are: • Edematous • Inflamed • Infected • Callused

30. Complications • May not accurately reflect patient’s condition • Mismanagement • Burns • Infection • Scarring/bruising • Inflammatory changes • Nerve damage • Artery damage • Bruising • Hematoma • Bleeding

31. Arterial Catheter • Indications: Need for continuous measurement, • Sites • Umbilical arteries • Neonates • Peripheral arteries • Radial artery • Posterior tibial • Dorsalis pedis

32. Arterial Catheter (cont.) • Direct measurement of BP (MAP) • Waveform • Patency of arterial line • Quality of pulse pressure • Calculation of MAP

33. Continuous Invasive Blood Gas Monitoring • Closed loop • Frequent ABGs • Low volume

35. UAC procedure • Umbilical artery lines are entered for removal of blood for monitoring of laboratory work and arterial blood gases. • Umbilical arterial lines are entered for the administration of intravenous fluids and medications. • Any time an arterial line is entered, sterile technique should be maintained. • Care should be taken to prevent blood clots or air emboli from entering the patient. • The umbilical artery line should be maintained as a closed circuit to prevent the loss of blood or intravenous fluids.

36. UAC procedure Contraindications • Signs of complications (i.e.: leg blanching, discoloration, decreased peripheral pulses, improper position of catheter) indicating that infusion or withdrawal through the catheter may cause or further decrease circulation to an extremity. • An infant with an already depleted blood volume.

37. UAC procedure Equipment required • 3 cc sterile dry syringe for clearing line • 1 cc sterile syringe with dead space filled with 1000 units per cc of heparin • 1 cc syringe for drawing lab work • 1 cc syringe of normal saline for flush (This syringe is placed on the stopcock at the beginning of each shift).

40. UAC Care • The umbilical arterial catheter should be maintained as a sterile infusion line. Good hand washing technique is IMPERATIVE. • The arterial line should be observed at all times to maintain a closed system to: • Prevent loss of blood • Prevent loss of I.V. fluids • Prevent air embolisms. • Maintain patency of line.

41. Central Venous Catheters • Sites vary with patient age and condition • Measures • Right atrial pressure • Mixed venous blood gases/saturations • CVP • Volume status

42. Pulmonary Artery Catheters Less frequently used with children

43. Pulmonary Artery Catheters

44. Cardiac Output

45. Noninvasive Measurement of Cardiac Output • Fick equation • Rebreathing CO2 • Pulse oximetry • Perfusion Index

46. Normal values of arterial O2 tension • Oxygen tension in term neonates is 50-70 mm of Hg and in children 70-100 mm of Hg. • PaO2 monitoring has recognized shortcoming. • Validity of values are optimal when blood gas samples are obtained from indwelling catheters under quiet, resting conditions. In a crying neonate due to pain of percutaneous puncture values obtained may not reflect steady state conditions. • paO2 values vary considerably throughout the day in sick neonates. • Intermittent sampling produces only a limited view of a single point in time.

47. Normal values of arterial O2 tension • Transcutaneous (TcPO2) monitors are useful for judging trends in oxygenation during management of acute lung disease. These monitors measure skin surface pO2 (not paO2), which under proper conditions is closely correlated with arterial pO2 • The TcPO2 sensor combines a miniature blood gas electrode with a servo controlled probe. The sensor is applied to the skin in a way that excludes any effects of environmental air on values measured. The technique depends on heating the skin at the sensor site to 43.5C to 44C.

48. Normal values of arterial O2 tension • Correlation is poor and TcPO2may underestimate paO2 • Such conditions include circulatory insufficiency, inadequate electrode temperature, improper calibration and lack of user expertise, patient age greater than 10 weeks (skin thickness factor), and use of vasodilator agents. • Maturation and thickening of skin with increasing postnatal age limits the use of transcutaneous monitoring to neonates. • All of these artifacts of measurement result in underestimation of arterial pO2 • Under usual circumstances TcPO2should be in the 40 to 80 mm Hg range.

49. Normal values of arterial O2 tension • There is a time lag between measured TcPO2 • and paO2 values. As a result, oxygen concentration • should not be continuously raised and lowered in attempts to “chase” fluctuating TcPO2

50. pH: >7.20 PaCO2: 45-55 Depends on pH PaO2: 45-65 HCO3: 15-18 ABG Values: ELBW/Premature <28 wk