basic blood gas interpretation

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Basic Blood Gas Interpretation . 205b. Values Measured. P a O 2 – amount of oxygen in the arterial blood S a O 2 – percent saturation of the hemoglobin as measured by a CO-oximeter. Values Measured. - PowerPoint PPT Presentation

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Basic Blood Gas Interpretation

205bValues MeasuredPaO2 amount of oxygen in the arterial bloodSaO2 percent saturation of the hemoglobin as measured by a CO-oximeterValues MeasuredSpO2 percent saturation of the hemoglobin as measured by a pulse oximeterHb amount of hemoglobin present

Values MeasuredHct (Hematocrit) percent of the blood that is composed of cellspH concentration of hydrogen ions (H+) in the arterial blood

Values MeasuredPaCO2 amount of carbon dioxide in the arterial bloodHCO3 amount of bicarbonate in the arterial bloodValues MeasuredB.E. (base excess/base deficit) the total of all buffering systems in the arterial bloodCO amount of carbon monoxide present in the arterial blood

Determination of Oxygenation Normal ValuesPaO2 80 100 mmHgMild hypoxemia 60 79 mmHgModerate hypoxemia 40 59 mmHgSevere hypoxemia < 40 mmHgSaO2 93% 97%88-92% COPD/lung diseaseHb Males: 13.5 16.5 g/dlFemales: 12 15 g/dlHct Males: 42 54%Females: 38 47%

Determination of OxygenationNormal ValuesCaO2 Males: 17.1 21.7 ml/dlFemales: 14.9 19.7 ml/dlCOHb 100 mmHg: hyperoxygenation60 79 mmHg: mild hypoxemiaMethod of Determining OxygenationEvaluate the PaO240 59 mmHg: moderate hypoxemia< 40 mmHg: severe hypoxemiaMethod of Determining OxygenationEvaluate the SaO2> 93%: normal oxygenation< 93%: may be hypoxemic; examine the hemoglobinMethod of Determining OxygenationEvaluate the Hb12 16 g/dl: normal< 12 g/dl: anemic> 16 g/dl: polycythemicMethod of Determining OxygenationEvaluate the CaO217 20 ml/dl: normal15 17 ml/dl: mild hypoxia12 14.9 ml/dl: moderate hypoxia< 12 ml/dl: severe hypoxiaMethod of Determining OxygenationOther factors in oxygenationAbnormal forms of hemoglobin: Detectable by CO-oximeter, not pulse oximeter

Estimate PaO2Predicated PaO2 based on age= Estimated value of what there PaO2 might bePaO2= 110 half the persons ageexample: 20 year old. 110 10= PaO2 100(PaO2 of 60 will equal approximately 90% saturation based on the oxyhemoglobin curve)

Determination of Acid Base Balance

pH is equal to the log of the hydrogen ion pH = Log [H+]

Determination of Acid Base Balance

Henderson-Hasselbalch equationpH = pK + Log HCO3 H2CO3pH = pK + Log HCO3 (Renal) Paco2 x0.03 (Lungs)

Determination of Acid Base Balance

pH measures the bloods acidity or alkalinityMust always be determined first when assessing acid- base balance

Determination of Acid Base Balance

PaCO2 is our stimulus to breatheA high PaCO2 indicates that not enough carbon dioxide is being exhaledA low PaCO2 indicates that too much carbon dioxide is being eliminated

Determination of Acid Base Balance

Evaluate base excess or bicarbonate (metabolic parameter) Is it acidic or alkaline22- 26 mEq/L is normal > 26 Indicates metabolic alkalosis < 22 Indicates metabolic acidosis

Determination of Acid Base Balance

Bicarbonate is the base or buffer that neutralizes hydrogen ions (HCO3) Bicarbonate is made in the red blood cells, liver, and kidney

Determination of Acid Base Balance

When bicarbonate levels are elevated, an excess of alkalinity exists in the metabolic systemsWhen bicarbonate levels are low, an excess of acidity exists in the metabolic systems

Determination of Acid Base Balance

If the pH is not normal, identify whether it is acidic or alkaline

Determination of Acid Base Balance

Identify whether the PaCO2 or bicarbonate disturbance (acidosis or alkalosis) matches The pH change (acidosis or alkalosis) This is the cause of the problem and represents where treatment should be directed. (e.g. if pH is acidic, PaCO2 is alkaline and bicarbonate is acidic, the problem is a metabolic acidosis)

Determination of Acid Base Balance

If the pH is not 7.40 but within the normal range (7.35 - 7.45), the disturbance is fully compensated If both the respiratory and metabolic parameters match the pH, the problem is a combined disturbance

Determination of Acid Base Balance

A change in the opposite direction (acidosis or alkalosis) by the parameter (PaCO2 or bicarbonate) that does not match the pH is an attempt to restore the pH (referred to as partial compensation)Evaluation of CompensationArterial Punctures Indications1Need to evaluate ventilation, acid-base balance, and oxygenation of bloodAssess the patients response to therapyMonitor and assess the severity and progression of a disease process1 Excerpt from the AARC Clinical Practice Guideline for Sampling for Arterial Blood Gas AnalysisArterial Punctures Contraindications1Negative Allen testPresence of a surgical shunt proximal to the sample site

http://www.youtube.com/watch?v=HRcVVGBb9fg

1 Excerpt from the AARC Clinical Practice Guideline for Sampling for Arterial Blood Gas AnalysisDialysis shunt

Arterial Punctures Contraindications1Presence of a lesion at the sample siteCoagulopathy or medium to high dose anticoagulation therapy (relative contraindication)

1 Excerpt from the AARC Clinical Practice Guideline for Sampling for Arterial Blood Gas AnalysisHematoma

Arterial Punctures Hazards and complications1ArteriospasmAir or clotted blood emboliHematoma

1 Excerpt from the AARC Clinical Practice Guideline for Sampling for Arterial Blood Gas Analysis

Arterial Punctures Hazards and complications1HemorrhagePainArterial occlusion

1 Excerpt from the AARC Clinical Practice Guideline for Sampling for Arterial Blood Gas Analysis

Arterial Punctures Hazards and complications1Trauma to the vesselVasovagal responsePatient or sample contaminationAnaphylaxis (if local anesthetic used, Xylocain)

1 Excerpt from the AARC Clinical Practice Guideline for Sampling for Arterial Blood Gas Analysis

Arterial Punctures Assessment of need for arterial sample1Initiation, change, or discontinuation of therapy (oxygen or ventilatory support)History and physical indicators

1 Excerpt from the AARC Clinical Practice Guideline for Sampling for Arterial Blood Gas Analysis

Arterial Punctures Assessment of need for arterial sample1Presence of other abnormal diagnostic tests or findingsBaseline study for pulmonary rehabilitation program

1 Excerpt from the AARC Clinical Practice Guideline for Sampling for Arterial Blood Gas Analysis

Arterial Punctures Frequency of monitoring1Dependent upon clinical status of the patient and presence of indicationsIf frequent monitoring required, use alternating sites or indwelling arterial catheter

1 Excerpt from the AARC Clinical Practice Guideline for Sampling for Arterial Blood Gas Analysis

Arterial Punctures Allen TestPerformed to determine presence of adequate collateral circulation in the handCannot be used with uncooperative or unconscious patientsArterial Punctures Allen TestProcedureHave patient clench hand into a tight fistApply pressure to occlude flow through the radial and ulnar arteriesOpen hand; observe to ensure that the palm and fingers are blanchedArterial Punctures Allen TestProcedureRemove pressure from the ulnar arteryObserve time necessary for flushing of handTest is negative for collateral circulation if flushing does not occur within 20 seconds; an alternative site is chosenThe Modified Allen Test

The modified Allen test. A, The hand is clenched into a tight fist and pressure is applied to the radial and ulnar arteries. B, The hand is opened (but not fully extended); the palm and fingers are blanched. C, Removal of pressure on the ulnar artery should result in flushing of the entire hand.

Which Artery to Choose?The radial artery is superficial, has collaterals and is easily compressed. It should almost always be the first choice.Other arteries (femoral, dorsalis pedis, brachial) can be used in emergencies.

Preparing to perform the Procedure:Make sure you and the patient are comfortable.Assess the patency of the radial and ulnar arteries.Procedure For Obtaining an Arterial Sample (Radius) Confirm the order in the patients chartNote any contraindications and notify physician if any existProcedure For Obtaining an Arterial Sample (Radius)Ensure that patient is in a steady state (no changes in oxygen status for at least twenty minutes)Obtain and assemble necessary equipmentProcedure For Obtaining an Arterial Sample (Radius)Wash hands, don protective equipment, explain the procedure to the patientPosition the patient correctly

Procedure For Obtaining an Arterial Sample (Radius)Perform an Allen test and confirm collateral circulationCleanse the site with 70% isopropyl alcohol or other antisepticProcedure For Obtaining an Arterial Sample (Radius)Inject local anesthetic, if hospital protocolHeparinize the syringe, if not already heparinized

Procedure For Obtaining an Arterial Sample (Radius)Palpate and secure the arteryInsert the needle, bevel up, at a 45 angle through the skin until blood pulsates into the syringe

Procedure For Obtaining an Arterial Sample (Radius)Withdraw the needle when sufficient sample is obtainedApply firm pressure to the puncture site using a gauze padProcedure For Obtaining an Arterial Sample (Radius)Maintain pressure for a minimum of five minutes, longer if patient is on anticoagulant therapyExpel any air bubbles from the syringe

Procedure For Obtaining an Arterial Sample (Radius)Mix the sample and label itPlace the sample in an icy slush (only if a delay in running the sample is expected)

Procedure For Obtaining an Arterial Sample (Radius)Dispose of any waste material in the appropriate containerDocument the procedure

Arterial Puncture

http://www.youtube.com/watch?v=KbszTXeg71gThe Kit

Air bubblesGas equilibration