Pocket Medicine: The Massachusetts General Hospital Handbook of Internal Medicine (35 page)

• Daily awakening trial (d/c all sedation;
Lancet
2008;371:126): open eyes & w/o: agitation, RR >35, S
_a
O
₂
<88%, resp distress or arrhythmias (if fail, restart sedation at 1
/
2 prior dose).

• SBT = CPAP or T piece × 30–120 min

failure if: deteriorating ABGs, ↑ RR, ↑ or ↓ HR, ↑ or ↓ BP, diaphoresis, anxiety

• Tolerate SBT → extubation. Fail SBT → ? cause → work to correct → retry SBT qd

Complications

• Oxygen toxicity (theoretical); proportional to duration + degree of ↑ oxygen (F
_i
O
₂
>0.6)

• Ventilator-associated pneumonia (~1%/day, mortality rate ~30%)

typical pathogens: MRSA,
Pseudomonas
,
Acinetobacter
and
Enterobacter
species

preventive strategies (
AJRCCM
2005;171:388): wash hands, HOB elevated, non-nasal intub., enteral nutrition rather than TPN, routine suction of subglottic secretions, avoid unnecessary abx & transfusions, routine oral antiseptic, stress-ulcer prophylaxis w/ ? sucralfate (↓ VAP, ↑ GIB) vs. H
₂
RA/PPI, ? silver-coated tubes (
  JAMA
2008;300:805)

• Laryngeal

edema: for Pts vent >36 h; ? predicted by
cuff leak test. Methylprednisolone 20 mg IV q4h starting 12 h pre-extub. → ↓↓ edema and 50% ↓ in reintubation (
Lancet
2007;369:1003)

ulceration: consider
tracheostomy
for patients in whom expect >14 d of mech vent → ↓ duration mech vent, ↓ # ICU days (
BMJ
2005;330:1243); no benefit to performing at ~1 wk vs. waiting until ~2 wk (
  JAMA
2010;303:1483)

• Malnutrition (for all critically ill Pts):
enteral nutrition
initiated early is safe but not necessary (
  JAMA
2012;307:795), but bolus may ↑ risk of VAP & C diff. (
  JPEN
2002;26:174); no clear benefit to ✓ing gastric residuals (
  JAMA
2013;309:249);
parenteral nutrition
should be delayed until after day 8 to ↓ risk of infections, cholestasis, RRT, ventilator days (
NEJM
2011;365:506)

• Oversedation/delirium: BDZs and polypharmacy are risk factors

propofol: HoTN in ~25%;
propofol infusion syndrome
(PRIS) ? esp. w/ high (>5 mg/kg/h) & prolonged (>48 h) infusions & concom vasopressors → ↑ AG, cardiac dysfxn, rhabdomyolysis, ↑ triglycerides, & renal failure (
Crit Care
2009;13:R169)

dexmedetomidine: ↑ vent-free days, but brady & HoTN c/w BDZ (
  JAMA
2012;307:1151)

ACUTE RESPIRATORY DISTRESS SYNDROME

New “Berlin” definition
(
  JAMA
2012;307:2526)

•
Acute onset
within 1 wk of clinical insult or worsening respiratory status

•
Bilateral infiltrates
without alternative explanation (eg, effusion, atelectasis, nodules)

•
Edema not fully explained
by fluid overload or congestive heart failure

•
Hypoxemia
: P
_a
O
₂
/F
_i
O
₂
determined with 5 cm H
₂
O of PEEP

P
_a
O
₂
/F
_i
O
₂
200–300 = mild ARDS (may be on NIPPV), 100–200 = mod, <100 = severe

• Chest CT: heterogeneous lung with densities greater in dependent areas

• Lung bx: diffuse alveolar damage (DAD); Ø req, may give useful dx info (
Chest
2004;125:197)

Pathophysiology

• ↑ intrapulmonary shunt → hypoxemia (∴ Rx w/ PEEP to prevent derecruitment)

• ↑ increased dead space fraction (see Appendix), predicts ↑ mort. (
NEJM
2002;346:1281)

• ↓ compliance: V
_T
/(P
_plat
– PEEP) <50 mL/cm H
₂
O

Treatment
(primarily supportive)
(
Lancet
2007;369:1553;
NEJM
2007;357:1113)

• Goal is to maintain gas exchange, sustain life, & avoid ventilator-induced lung injury (VILI)

•
Fluid balance
: target CVP 4–6 cm H
₂
O (if nonoliguric & normotensive) → ↑ vent/ICU-free days, but no Δ mortality (
NEJM
2006;354:2564); PA catheter unproven (
NEJM
2006;354:2213); using BNP >200 to trigger diuresis (UOP goal 4.5–9 mL/kg/h × 3 h) ↓ time to extubation (
AJRCCM
2012;186:1256)

•
Steroids
: debate continues. Adverse effects include neuromuscular weakness, poor glc control, ? infection. Benefit may vary by time since ARDS onset:

<72 h: older studies w/o benefit (
NEJM
1987;317:1565); ? ↓ mortality, ↑ vent/ICU-free days in more recent, controversial study (
Chest
2007;131:954)

7–13 d: ? benefit → ↑ vent/ICU-free days, no mortality difference (
NEJM
2006;354:1671)

≥14 d: ↑ mortality (
NEJM
2006;354:1671)

•
Paralysis
: if P
_a
O
₂
/F
_i
O
₂
<150, cisatracurium × 48 h ↓ mortality (
NEJM
2010;363:1107)

•
Experimental
(
  JAMA
2010;304:2521)

Inhaled NO or prostacyclins:
↑ P
_a
O
₂
/F
_i
O
₂
, no ↓ mort. or vent-free days (
BMJ
2007;334:779)

Prone
: ↑ P
_a
O
₂
, but ↑ complications and no ↓ mortality (
  JAMA
2009;302:1977); ? ↓ mortality if P
_a
O
₂
/F
_i
O
₂
<100 (
Intens Care Med
2010;36:585)

High-freq oscillatory vent:
no benefit and possible harm (
NEJM
2013;368:795, 806, & 863)

Lung recruitment
: apply CPAP 40–45 cm H
₂
O × 2 min to recruit lung and then ↑ PEEP to maintain; sicker Pts had ↑ recruitable lung (
NEJM
2006;354:1775, 1839)

ECMO:
may be useful in refractory ARDS, but no good trial data (
NEJM
2011;365:1905)

Esoph manometry:
adjust PEEP according to esoph pressure (
pleural pressure) to maintain positive transpulm pressure → ↑ P
_a
O
₂
/F
_i
O
₂
, ↑ compliance and possible outcome benefit (
NEJM
2008;359:2095); helpful in obese Pts or w/ ↑ abdominal pressure

Prognosis

• Mortality ~40% overall in clinical trials; 9–15% resp. causes, 85–91% extrapulm (MODS)

• ↑ BNP & troponin a/w ↑ mortality (
Chest
2007;131:964;
PLoS One
2012;7:e40515)

• Survivors: PFTs ~normal, ↓ D
_L
CO, muscle wasting, weakness persists (
NEJM
2003;348:683), ↓ exercise tolerance, ↓ QoL, ↑ psych morbidity (
NEJM
2011;364:1293)

SEPSIS