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Selective
Decontamination of the Digestive Tract (SDD)
Sarah
Ramsay
Background
-
ICU
patients at high risk of acquiring nosocomial infections causing increased
mortality, morbidity, length of stay and costs
-
European
survey 45% of patients infected of which 21% acquired in ICU
-
Most
common are pneumonias, other lower respiratory tract infections, urinary
tract infections and blood-stream infections
-
Attributable
mortality for VAP: 24-30%
-
Attributable
mortality for blood-stream infections 28-35%
-
High
risk is the result of multiple factors
-
Severity
of underlying disease
-
Frequent
and prolonged use of invasive devices
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Increased
exposure to potentially pathogenic organisms
-
From
environment
- From
within host
-
In
healthy patients indigenous gut and oropharyngeal flora remain very static
over time. Overgrowth of potentially pathogenic organisms is prevented by
-
In
critically ill patients these mechanisms are compromised by the underlying
disease process, instrumentation and drugs resulting in
-
Impaired
salivary flow
-
Gastric
alkalization
-
Cholestasis
-
Intestinal
ileus
Broad
spectrum bacteria eradicates indigenous flora and loss of colonization
resistance
Within
a few days of ICU admission normal flora replaced by potentially pathogenic
organisms (in >2/3 of patients) in oropharynx then stomach and gut.
Micro-aspiration of contaminated upper GI tract fluid most plausible and
demonstrable cause of infection. Translocation through the gut wall is a
theoretical possibility which has been demonstrated in animal studies but not
convincingly in humans.
Regimes
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Eradication
of potentially pathogenic organisms from the mouth and GIT by local
administration of non-absorbable antibiotics
-
± short course of systemic
antibiotics for early / incubating respiratory infections
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Usually
cefotaxime, ceftriaxone
-
Given
until surveillance cultures show GIT decontamination (usually 4 days)
-
Targets
early established infection by community acquired pathogens (e.g.
Streptococcus pneumoniae, haemophilus influenzae) which may be aspirated
during intubation
-
Temporizes
until enteral drugs have decontaminated the GIT
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Start
ASAP on admission, continue enteral drugs until extubated or leave ICU
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Regular
cultures to monitor effectiveness of SSD
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Optimal
hygiene to prevent cross-infection
-
SDD
is also used for the prevention of gut-derived infections in acute
necrotizing pancreatitis and liver transplantation.
SDD – for and against
-
Many
studies with conflicting results.
-
SDD
appears to reduce infection rates, especially in critically ill surgical
patients (who have a higher rate of nosocomial pneumonia and a higher
attributable mortality compared to medical patients)
-
SDD is well accepted in Europe but uptake of the technique
has been slow in other countries especially USA despite evidence
of improved infection rates and possible improved mortality rates with
absence of harm and little increased cost from trials with good design.
-
But
…
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Effect
on mortality is less clear – most studies are underpowered and cannot
exclude a treatment benefit
-
Select
group of patients likely to benefit from SDD not well defined
-
Exact
nature of best SDD not well defined: topical alone versus topical plus
systemic
-
Concerns about resistance: although good studies have showed
little change in resistance patterns, increased colonization (but not
infection) with Gram-positive organisms is noted. In some of these
studies the incidence of MRSA, and resistant entercocci is very low, and
the safety of SDD is questionable in centres where incidence of these
potentially more pathogenic organisms is high. Nasal mupirocin may be
helpful. Some argue that SDD will add to add to resistance problems,
others that it will reduce then by preventing infection and subsequent
use of antibiotic.
-
If effect is more marked with systemic antibiotics than
topical alone is this simply akin to the peri-operative antibiotics that
most surgical patients already receive?
-
Inconvenience of additional drugs and surveillance culturing
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Possible increased drug costs
The Evidence:
Meta-analyses:
D'Amico
R et al
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5727
patients from 33 trials
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Combination
of systemic and topical Rx reduced respiratory infection rates and overall
mortality
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VAP:
odds ratio 0.35 (0.29-0.41)
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Mortality:
odds ratio 0.8 (0.69-0.93)
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Reduction
in mortality = 6% (30 to 24%)
Nathens
AB and Marshall JC
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Analysed
predominantly surgical or medical patients separately
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Mortality
was reduced for surgical patients (odds ratio 0.7 [0.52-0.93]) while no such
affect was demonstrated for medical patients (odds ratio 0.91 [0.71-1.18])
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Greatest
effect was seen in topical and systemic therapy combined.
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Pneumonia
was reduced in both subsets, although bacteraemia was only reduced in
surgical patients.
van
Nieuwenhoven CA et al
Investigated
the methodological quality of SDD trials and found an inverse relationship
between trial quality and benefit of SDD on incidence of pneumonia, and no
relationship between trial quality and mortality rates. May have resulted in
over optimistic estimates of the effect of SDD in meta-analyses.
Recent trials
Kruerger
WA et al 2002
Well-designed
trial showed in 527 mainly surgical and trauma patients showing reduced
infection rates and reduced organ failures but not ICU mortality in patients
given combined topical and systemic SDD. In a predefined subgroup of patients
with mid-range APACHE scores (20-29) ICU, hospital and one year mortality was
significantly reduced. Surveillance cultures showed no change in resistance
patterns although there was increased colonization (but not infection) by
Gram-positive organisms.
Sánchez García M et al 1998
271
mainly medical patients reduced pneumonia rates but not ICU mortality in
patients given combined topical and systemic SDD.
Bergmans
DCJJ et al 2001
Oropharyngeal
decontamination without GIT decontamination or systemic therapy reduced rates of
VAP in 227 critically ill patients, underpowered to show a survival benefit.
Additional
reading
D'Amico
R, Pifferi S, Leonetti C, Torri V, Tinazzi A, Liberati A. Effectiveness of
antibiotic prophylaxis in critically ill adult patients: a systematic review of
randomised controlled trials. BMJ 1998;316:1275–1285.
Nathens
AB, Marshall JC. Selective decontamination of the digestive tract in surgical
patients. Arch Surg 1999;134:170–176.
Bergmans
DCJJ, Bonten MJM, Gaillard CA, Paling JC, Van der Geest S, Van Tiel FH, Beysens
AJ, de Leeuw PW, Stobberingh EE. Prevention of ventilator-associated pneumonia
by oral decontamination. Am J Respir Crit Care Med 2001;164:382–388.
Wolfgang
A. Krueger, Franz-Peter Lenhart, Gertraud Neeser, Gotthart Ruckdeschel, Heidi
Schreckhase, Hans-Joachim Eissner, Helmuth Forst, Joachim Eckart, Klaus Peter,
and Klaus E. Unertl. Influence of
Combined Intravenous and Topical Antibiotic Prophylaxis on the Incidence of
Infections, Organ Dysfunctions, and Mortality in Critically Ill Surgical
Patients: A Prospective, Stratified, Randomized, Double-Blind,
Placebo-controlled Clinical Trial Am. J. Respir. Crit. Care Med.
2002 166: 1029-1037.
Miguel Sánchez
García, José A. Cambronero Galache, Julia López Diaz, Enrique Cerdá
Cerdá, José Rubio Blasco, Miguel A. Gómez Aguinaga, Antonio Núñez
Reiz, Santiago Rogero Marín, Juan J. Oñoro Cañaveral, And José A.
Sacristán Del Castillo. Effectiveness
and Cost of Selective Decontamination of the Digestive Tract in Critically Ill
Intubated Patients . A
Randomized, Double-blind, Placebo-controlled, Multicenter Trial.
Am. J. Respir. Crit. Care Med. 1998 158: 908-916.
Christianne
A. van Nieuwenhoven; Erik Buskens; Frank H. van Tiel; Marc J. M. Bonten
Relationship Between Methodological Trial Quality and the Effects of Selective
Digestive Decontamination on Pneumonia and Mortality in Critically Ill Patients.
JAMA. 2001;286:335-340
© Sarah Ramsay February 2003
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