acute respiratory distress syndrome the rational selection of rescue methods in 2015 ram e....
TRANSCRIPT
Acute Respiratory Distress SyndromeThe Rational selection of Rescue Methods in 2015
Ram E. Rajagopalan,MBBS, AB (Int Med) AB (Crit Care)
Head, Department of Critical Care MedicineSUNDARAM MEDICAL FOUNDATION
Chennai
Pl. effusion
Homogeneous Disease with Heterogeneous Effects
Maunder et al. JAMA 1986; 255:2463-5.Gattinoni et al. Intensive Care Med. 1986; 12: 137-42.
“Preservation of normallung regions”
Pulmonary edema
Dependent collapse
Evidence for a low VtTidal Volume:Low (6cc / Kg) vs. traditional (12 cc/Kg)
N Engl J Med 2000; 342: 1301-8.
Titrating PEEP to ‘Compliance’
Initiated based on oxygenation;
Titrated based on compliance:Assess Crs by looking at DP for a level of PEEPNote effect on DP with change of PEEPTitrate PEEP to get lowest DPAJRCCM 2001; 163: 69-78
Recruitment May Help!Recruitment, the application of a high Ptp, can make the alveolar distension more homogeneous
1. Opens atelectasis; reduced shunt2. Allows decelerating PEEP titration3. Improves compliance4. Lowers PEEP requirement
If…..Oxygenation remains poor:P/F ratio <100 (e.g. pO2 60 torr on 60% FiO2)
Lung Compliance remains poor?Pplat >30; DP remains high(Despite Vt <6cc/kg; post-PEEP titration/ recruitment)
It’s time to consider
RESCUE
THERAPIES…
Heterogeneous effect of Paw Ptp (not Pairway ) correlates c EELV
A uniform airway pressure causes heterogeneous lung expansion because of pleural pressure D
The range of Ppleura J with lung injury
May result in significant over-distension of the ventral lung (A)
_
Recruitment ManeuversRecruitment Maneuver =Transient / intermittent application of a high trans-pulmonary pressure intended to J End Exp. Lung Volume (& open up unaerated lung)
An intentional over-distension of the lung
The effect on oxygenation is variable & un-sustained
Preferred use in patients with: Early ARDS (~ 24 hours) ; avoid if >7 days Extra-pulmonary ARDS; avoid in pneumonia Low prior Vt and PEEP …
(post intubation, suction, disconnection)
RMs work very selectively
AJRCCM 2002; 165:165-70Anesthesiology 2002; 96: 795-802Crit Care Med 2003; 31: 411-8
Adverse Effects are SeenRecruitment Maneuver
Cardiovascular effects
Cerebral perfusionGI FunctionAlveolar/
Endothelialinjury
High pressures generated may lead to transient or sustained organ dysfunction
Recruited lung is not normal
AJRCCM 2009; 180: 415 - 23Regional heterogeneity may persist even after “opening” the lung
The Prone Position also Homogenizes!
Supine Prone
Deforming Pressures in ARDS
LungSuperimposed
Pressure
But….Superimposed pressureis altered by…..
Deforming Pressures in ARDS
Heart & Mediastinum
Abdominal contents & caudal diaphragm;
“Pincers”
Effect of Heart & Mediastinum
AJRCCM 2000;161:1660-5
The weight of the heart and mediastinum exaggerates the gravitational collapse esp. on the left lung
In the prone position the entire mass is supported on the sternum and chest wall with no intervening lung
Chest Wall Compliance
Mobile anterior chest wall allows preferential ventilation
of ventral lung
Restriction of anterior chest makes wall compliance
homogeneous
Supine Prone
Uniform V/Q matching
Contrary to popular belief, pulmonary blood flow may not be gravity dependent (“C”)
Prone Positioning The Great Equalizer!
Decreases deforming forces (abdominal ‘pincers’ & heart)
Homogenizes chest wall compliance
Homogenizes ventilation & V/Q matching
AJRCCM 2000;161:1660-5AJRCCM1998; 157: 387-93AJRCCM 1998; 157: 1785-90
Recruitment vs. Prone
Recruitment is the “forceful compulsion” of the ARDS lung to become uniformly compliant
While Prone positioning removes deforming forces to allow the lung to normalize; “a permissive process”
Prone Position Improves Oxygenation
Rajagopalan et al; Ind. J. Crit. Care Med. 1999; 3(1): 73-5. 0
5 0
1 0 0
1 5 0
2 0 0
2 5 0
3 0 0
3 5 0
Pre P = 0.0232 Best Prone
83.8 + 27.3 torr 160.9 + 75.6 torr
PaO
2 / F
iO2 R
atio
Gattinoni: Prone Trial 2001n = 152/ 152; 6-hours prone/day; 10 daysP/F <200 on 5 PEEP; <300 on 10 PEEP
No effect of Prone Positioning (?)
SUPINE
PRONE
Gattinoni et alN Engl J Med 2001; 345:568-73
Mancebo; Long ProningRCT of 136 patients76 were in prone position Aimed for 20 hrs/ day (obtained 17 hrs)Average duration of 10 days
Mortality K 58% to 43% (p=0.12)Multivariate analysis:
Higher SAPS II score, Days ventilated before studySupine posture J mortality
AJRCCM 2006; 173: 1233-9.
2013: Prone Works!
N Engl J Med 2013doi: 10.1056/ NEJMoa1214103
n = 466
P/F <150 (avg: 100)
Proned >16 hrs. (averaged 17hrs.)
Mortality:28 days: 16% (v. 32.8%)90 days: 23.6% (v. 41%)
Gas exchange in HFOV
Diffusive & convective changes mediated by oscillation determine CO2 elimination
Oxygenation is determined by mean Paw
Sustaining high mPaw
Conventional ventilation translates into higher and prolonged peak Paw which may be more detrimental to normal alveoli
Paw
Time
mPaw HFO
mPaw PCVRationale for
HFOV
High Frequency Oscillation
N Engl J Med 2013. DOI: 10.1056/NEJMoa1215554
N Engl J Med 2013. DOI: 10.1056/NEJMoa1215716
OSCILLATE
Outcomes with HFOV
OSCAR
OSCILLATE stopped p 548 ptsOSCAR n=795
Canadian CTG
Oxford
Is HFOV ineffective? The patients were sick enough; P/F ratio <200
Delayed inclusion to 1 week confounds HFOV requires skill; adequacy in trial?
OSCAR (no difference) Poor control ventilation (J Paw; J Vt) could have
annulled benefits of conventional Rx
OSCILLATE (HFOV worse) Good conventional vent. may have made it beneficial High Paw in HFOV; assoc. HD D & vasoactive Rx
The Arbitrary Choice of Paw
In both trials the selection of Paw was arbitrary:OSCAR: 5 cm above plateau (no recruitment)
OSCILLATE: 30 cm H2O after 40/40 CPAP RM
Not titrated to individual lung compliance
Subsequent D based on FiO2 Table
Vt: How low… do we go?
Non aeratedPoor aerationNormalHyperinflated
2/3
1/3
AJRCCM 2007; 175: 160–166.
In patients withARDS (Vt 6ml / Kg);
1/3 show significanthyperinflation with Inspiration (tidal)
Tidal Hyperinflation: Predictors
AJRCCM 2007; 175: 160–166.
Tidal NoHyperinflation Hyperinflation
P plat: 28.9+0.9 25.5+0.9 p=0.006
P/F: 102+24 149+34 p=0.0008
Eins L Wt 1912+206 1541+386 p=0.008
% non-aerated 27+14.3 16.1+7.7 p=0.002
% normal 39.1+19.8 68.2+11.3 p=0.003
% hyperinflat 23.3+10.1 3.0+2.2 p=0.01
Tidal hyperinflation is an independent predictor of inflammation and ventilator-free days
Lowest tidal volume?
12 cc / kg
RIP
Mor
talit
y
Tidal volume
4cc/kg 6cc/kg 12cc/kg
If 6 cc/Kg J survival over 12 cc/Kg;would 0 cc/Kg result in immortality!!!
Pump-driven veno-venous ECMO
Lung “rested”:
Peak Paw = 20-25 cm H2OPEEP = 10-15 cm H2ORR = 10FiO2 = 0.3
CESAR trial
ECMO: The CESAR study90 randomized to transfer to ECMO site90 left on conventional Rx
Not ARDS only (~90%)
“Murray score” >3ph <7.20 (J CO2)
Death or severe disability at 6 months
Power adjustments made post-hoc; reduced n from 240 to 180!
Lancet 2009; 374; 1351-63
ECMO: The CESAR study
“ECMO group” “Control”Survival: 82% vs. 59% vs. 54%
63% vs. 47% (p=0.03)
Lancet 2009; 374; 1351-63
CESAR; Other concerns
Lancet 2009; 374; 1351-63
No difference in rescue modalities
Poor conventional care
CESAR; Sensitivity Analysis
Lancet 2010; 375: 550-1
Considering poor baseline care even a small J in survival in the conventionally treated patients would “annul” benefits of ECMO
2 less deaths would make results NS
Conclusion: The benefits of ECMO not clearThe benefits of expert care is obvious
My Take on ECMOProbably a very effective rescue method if performed with low complicationsHigh-cost is a limitationBest if performed in selected large-volume referral centres (unlikely in India??)
Criteria for initiation:The Murray score is ineffectiveP/F ratio based (Berlin ARDS severity) or? In patients with non-reducible DP
PECLA; A Caution
A lot of abuse of “pumpless” systems is on the rise
They are effective for CO2 removal, not oxygenation
“Pumpless Extra-corporeal Lung Assist”
Thank you for your patient
listening!