Presentation on theme: "What Pam Learned At the CSRT Conference Quebec City June 9-12, 2011."— Presentation transcript:
What Pam Learned At the CSRT Conference Quebec City June 9-12, 2011
Objectives Sleep During Mechanical Ventilation ABG Challenge: Classification vs. Interpretation And I learned a lot more than that…
Sleeping During Mechanical Ventilation Altered sleep patterns in ventilated patients can delay their weaning The average sleep time of a ventilated patient is the same as you or I, but the quality of sleep is reduced Stage 1 and 2 of sleep is a light sleep leading into Stage 3 and 4 which is deep non-REM sleep vital for psychological recovery REM sleep is vital for physical recovery Sleep at each stage for a healthy person is: 20% in Stages 1 and 2, 30% in Stages 3 and 4, 50% in REM sleep Ventilated patients will spend 45% of their sleep time in Stages 1 and 2 of sleep and 25% of their sleep is in REM sleep Less REM sleep means less physical recovery
Sleep During Mechanical Ventilation There are many reasons for sleeplessness in the ICU including: Noise (Surprise! Increases in decibels bother people) Lighting (Our lights are always on somewhere) Stress and Pain Bad Sedation ICU Psychosis Interventions in the middle of the night (bathing, shaving or suctioning) In Ventilated patients: Ventilator asynchrony
Vent Asynchrony Affecting Sleep If your patient is not comfortable on the ventilator they will rouse ¼ of patients suffer from asynchrony Studies have proven, though, that patients rested at night on PSV, roused more often than patients on AC, although there is no change to the amount of time spent in the different stages of sleep WHY?! Apnea, of course! Patients on AC ventilation still roused due to ventilator asynchrony – they were unable to trigger the vent
So what mode do I put my patient on so he can rest? Studies have shown that it is not necessary to control a patients ventilation for them to rest at night AND increasing PSV at night can increase Central Apneas by over-ventilating causing more arousals What we need is a ventilator mode that can adjust to the patients needs while they are sleeping such as NAVA NAVA: Neurally Adjusted Ventilatory Assist Involves a nasogastric catheter with electrodes buried to the level of the diaphragm that picks up electrical activity to the diaphragm and causes the ventilator to respond appropriately according to the patients needs ** Of course, if you don’t have access to NAVA, use PSV or PAV with an optimal support to ensure tidal volume of 6ml/kg IBW **
NAVA Having NAVA in our hospital would require the purchase of a Servo-i ventilator But just to prove a point, here’s how effective using NAVA was compared to PSV NAVA patients received less Stage 1 and 2 sleep compared to PSV NAVA patients received more Stage 3, 4 and REM sleep compared to PSV NAVA eliminates ventilator asynchrony and prevents overventilation NAVA allows for the variability in ventilation of the human body from wakefulness to sleep
ABG Challenge: Classification vs. Interpretation We were all taught in school that interpreting ABG’s was a lot deeper than uncompensated, compensated, metabolic, respiratory, acidosis, alkalosis We have forgotten it all!
Problem pH 7.12 pCO 2 42 HCO 3 - 13 PaO 2 60 Interpretation?
Answer Uncompensated Metabolic Acidosis (Lungs are not compensating) Mild Hypoxemia You’re not wrong, but you haven’t interpreted the ABG, only classified it
Classifying does NOT equal Interpretation TTTThere are 3 steps involved in interpreting an ABG Don’t worry it’s not that scary
Steps to Interpreting an ABG 1.Classification (check, got that down) 2.Calculations Determines whether or not the body is compensating and if there are other existing disorders 3.Confirmation Does it match the patient assessment and baseline. Check for accuracy
I Hate to Tell You… Problem: pH 7.12/CO 2 42/HCO 3 - 13 That’s not just an Uncompensated Metabolic Acidosis Remember the calculations we were taught in school? For every 1 point bicarbonate drop, pH should drop 0.015
Problem: Focus on bicarbonate Bicarb has dropped 11 points (24 – 13 = 11) pH should drop to maximum 7.23 (11 x 0.015 = 0.165; 7.40 – 0.165 = 7.235) CO2 should drop to 27 But our values are 7.12 with a CO2 of 42 What gives?! Calculations
Here’s a Quick Reference Chart for people who don’t want to do the math
The CO2 should be lower as the patient blows off CO2 to try to compensate for the metabolic acidosis CO2 should be 27 and the pH 7.23 In this case, our patient is not hyperventilating as he should He has tired out from hyperventilating and is now in Ventilatory Failure We have a DOUBLE DISORDER *cue dramatic music* Not only is the patient in a metabolic acidosis, but his lungs are adding to the problem – respiratory acidosis The CO2 value was probably lower at one point, but as the patient begins to fail, the CO2 rises and we happened to collect this gas at a time when the CO2 was in the normal range
BUT WAIT, We’re Not Done There are other calculations we can do to indicate a THIRD DISORDER from a blood gas. Anion Gap (remember that?) Anion gap helps to identify the presence of Metabolic acidosis and the type of metabolic acidosis When we know the type (Anion gap or non- anion gap) we can determine the cause
Anion Gap We all know how to calculate anion gap Na + - (Cl - + HCO 3 - ) A normal anion gap is 12mEq/L (thereabouts) If this value is <12, you have a non-anion gap acidosis If this value is >12, you have an anion gap acidosis There are numerous reasons to have an anion gap acidosis
Quick example 58 yo female presents with pneumonia, hypotension, nausea and vomiting x3 days pH 7.25/CO2 15/HCO3- 10 PaO2 76 Na+ 130 Cl- 90 Classification: Partially compensated (Chronic) Metabolic Acidosis Based on the quick reference chart with bicarb of 10, pH should be 7.19 with CO2 23 We know now that this is a mixed Metabolic Acidosis with Respiratory Alkalosis
Add the anion gap calculation in: 130 – (90 + 10) = 30 We’ve proven that this patient has an anion gap metabolic acidosis Some Triple Disorders can have a Metabolic Alkalosis mixed with an Anion Gap Metabolic Acidosis
Confirmation: Check your interpretation against the patient assessment and history Check for accuracy Anion Gap Met. Acid explained by the Pneumonia and consequent Sepsis Respiratory Alkalosis explained by hyperventilation due to hypoxemia Metabolic Alkalosis explained by the vomiting
Other Things I Learned Lung Expansion and Airway Clearance (MetaNeb system) Clinical Use of Transpulmonary Pressures (kind of like beating a dead horse, but really quite interesting) How to Manage Ventilator Asynchrony
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