Blood Gases / Acid-Base

Transcription

1 Blood Gases / Acid-Base Neonatal Ventilation Workshop June 2010 Dr. Julian Eason Consultant Neonatologist

2 Why are blood gases performed? Diagnostic assessment of oxygenation capacity of lungs Therapeutic assessment of oxygen pressure in blood Assess respiratory adequacy Assess acid-base status

3 How are blood gases performed? Aseptic technique Arterial, Capillary, Venous Machine measures ph, PaCO 2, PaO 2 Serum bicarbonate calculated Air bubbles, fluid dilution and pain can alter results

4 Normal Values ph PaCO2 PaO2 Bicarbonate Base Excess

5 Normal Values ph PaCO kpa PaO kpa Bicarbonate Base Excess meq/l Clinical condition must be incorporated into any blood gas analysis

6 Acid-base and buffers ph is a method of measuring small concentrations of acid in solution A buffer resists changes in ph by undergoing a reversible reaction ph stability maintains enzyme function, muscle and metabolic activity Buffering systems Carbonic acid bicarbonate system Haemoglobin Phosphate

7 Base Excess Buffer base is total of all anionic buffer components in the blood Base excess is the amount of deviation of patient s buffer base from normal How much extra basic chemicals the patient has in the blood. Base excess can be a negative value BE of -8 means 8mEq/L of base needs to be added to normalise the ph. More than just bicarbonate

8 Approach to the abnormal blood gas What is wrong? What caused it? What is being done about it?

9 Approach to the abnormal blood gas What is wrong? What caused it? Look at ph Look at PaCO2 Look at bicarbonate value What is being done about it? Acidosis v Alkalosis Respiratory v Metabolic Compensated v not

10 Clinical Scenarios

11 Clinical Scenario 1 32/40, Received steroids. PROM 3/7. NVD. Apgars 6 1, mins of age on CDS. Grunting resps. Gas taken Sample cap ph 7.18 PaCO PaO Bicarb 18 BE -9.6

12 Clinical Scenario 1 32/40, Received steroids. PROM 3/7. NVD. Apgars 6 1, mins of age on CDS. Grunting resps. Gas taken PEEP applied 4cmH 2 O during transfer T 36.6 C. Sats 92% in 35% FiO 2 Rpt gas on admission Sample cap cap ph PaCO PaO Bicarb BE

13 Clinical Scenario 1 32/40, Received steroids. PROM 3/7. NVD. Apgars 6 1, mins of age on CDS. Grunting resps. Gas taken PEEP applied 4cmH 2 O during transfer T 36.6 C. Sats 92% in 35% FiO 2 Rpt gas on admission Sample cap cap cap ph PaCO PaO CPAP driver 5-6cmH2O. Day 1 fluids. Sats 92% in air Bicarb BE

14 Clinical Scenario 2 25/40, Day 3. Ventilated SIMV 22/4, Rate 40, I time 0.34, Sats 90% in FiO 2 35%. Gas taken Sample art ph 7.16 PaCO PaO Bicarb 22 BE -3.9

15 Clinical Scenario 2 25/40, Day 3. Ventilated SIMV 22/4, Rate 40, I time 0.34, Sats 90% in FiO 2 35%. Gas taken Pressure 24/4, Rate 45. Sats 87% in FiO 2 50% Repeat gas taken after 30mins Sample art art ph PaCO PaO Bicarb BE

16 Clinical Scenario 2 25/40, Day 3. Ventilated SIMV 22/4, Rate 40, I time 0.34, Sats 90% in FiO 2 35%. Gas taken Pressure 24/4, Rate 45. Sats 87% in FiO 2 50% Repeat gas taken after 30mins Sample art art ph PaCO Cold light test positive Chest drain inserted. Improves clinically. Remains ventilated PaO 2 Bicarb BE days later, shown gas by nurse

17 Clinical Scenario 2 25/40, Day 3. Ventilated SIMV 22/4, Rate 40, I time 0.34, Sats 90% in FiO 2 35%. Gas taken Pressure 24/4, Rate 45. Sats 87% in FiO 2 50% Repeat gas taken after 30mins Cold light test positive Chest drain inserted. Improves clinically. Remains ventilated Sample art art art ph PaCO PaO Bicarb BE days later, shown gas by nurse

18 Clinical Scenario 3 34/40, PROM 24hrs. NVD. Postnatal ward. Feeds. Grunting resps at 5hrs of age. Moved to SCBU. Gas taken Sample cap ph 7.01 PaCO PaO Bicarb 24.4 BE -10.9

19 Clinical Scenario 3 34/40, PROM 24hrs. NVD. Postnatal ward. Feeds. Grunting resps at 5hrs of age. Moved to SCBU. Gas taken Given 30% oxygen. 10ml/kg fluid bolus. Partial septic screen. IV antibiotics 4hrs later, gas is taken Sample cap cap ph PaCO PaO Bicarb BE

20 Clinical Scenario 3 34/40, PROM 24hrs. NVD. Postnatal ward. Feeds. Grunting resps at 5hrs of age. Moved to SCBU. Gas taken Given 30% oxygen. 10ml/kg fluid bolus. Partial septic screen. IV antibiotics 4hrs later, gas is taken Sample cap cap cap ph Intubated 2.5mm ETT. Surfactant. SIMV 18/4, Rate 50, I 0.32, FiO 2 50%. 10ml/kg fluid bolus. Gas taken. Retrieval team called. PaCO PaO Bicarb BE

21 Clinical Scenario 3 34/40, PROM 24hrs. NVD. Postnatal ward. Feeds. Grunting resps at 5hrs of age. Moved to SCBU. Gas taken Given 30% oxygen. 10ml/kg fluid bolus. Partial septic screen. IV antibiotics 4hrs later, gas is taken Intubated 2.5mm ETT. Surfactant. SIMV 18/4, Rate 50, I 0.32, FiO 2 50%. 10ml/kg fluid bolus. Gas taken. Retrieval team called. Reintubated 3.5mm ETT. Ventilation Central lines. Inotropes. Sample cap cap cap art ph PaCO PaO Bicarb BE

22 Any Questions?