Transcript OBESITY AND ICU

OBESITY
AND ICU
HAMIDREZA JAMAATI
MD, FCCP, FCCM
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CARDIOVASCULAR PHYSIOLOGY IN
OBESITY
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PULMONARY PHYSIOLOGY IN
OBESITY
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IMMUNOLOGIC CHANGES IN
OBESITY
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CARDIOVASCULAR PHYSIOLOGY IN
OBESITY
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PULMONARY PHYSIOLOGY IN
OBESITY
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IMMUNOLOGIC CHANGES IN
OBESITY
IMMUNOLOGIC CHANGES IN
OBESITY
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Adipocytes are now known to produce signaling
molecules, called adipokines, that can
significantly alter inflammatory cell and immune
function. (Honiden & McArdle Clin Chest Med 2009)
The percentage of macrophages is substantially
higher in obese persons. (Dixit VD. J Leukoc Biol 2008)
Pre-adipocytes produce macrophage colony
stimulating factor (M-CSF) and peroxisome
proliferation activated receptor gamma
(PPARg), both of which promote macrophage
activation. (Karagiannides. Curr Opin Gastroenterol 2007)
IMMUNOLOGIC CHANGES IN
OBESITY
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Increased monocyte and
granulocyte oxidative burst, have
been found in obese subjects. (Lamas
O, Eur J Clin Nutr 2002)
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One such adipokine is leptin, which
acts to decrease food intake and
increase energy consumption by
promoting production of
anorexigenic factors. (Marti A,Obes Rev2001)
Leptin involvement in
immunoregulation
COMMON DISORDERS IN
CRITICALL ILL OBESE
PATIENTS
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Thromboembolic Disease
Aspiration
Abdominal Compartment Syndrome
CHALLENGES IN THE CARE OF CRITICALLY ILL
OBESE PATIENTS
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Airway Management
Central Venous Access
Surgical Airways
Hemodynamic Monitoring
Imaging and Tests
Nutritional Support
DRUG DOSING
NURSING CARE
Thromboembolic Disease
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The incidence of thromboembolic disease (TED)
varies:10% to 20% in general ward to 40% in pts
with major trauma and as high as 80% in critical care
patients.
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(Geerts WH. Chest 2004)
Stein and colleagues found an increased risk for VTE
in obese men and women compared with nonobese
patients. (Stein PD. Am J Med 2005)
Alterations in PAI-1 and fibrinolytic activity in obese
patients may contribute to their increased risk for
VTE. (Loskutoff DJ.Thromb Vasc Biol 1998)
Abdominal obesity may predispose obese patients to
atelectasis and arterial hypoxemia,particularly when
immobile and in the supine position. PE may be a
concern in these situations,but diagnosis of PE is a
challenge in patients with morbid obesity.
Thromboembolic Disease
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Compression ultrasonography with venous
imaging is not as sensitive in patients with
severe obesity and/or significant leg
edema.
Morbid obesity may limit CT angiography.
Ventilation-perfusion scanning or
perfusion scanning alone is a potential
alternative, but neither modality can give
a definitive diagnosis. (Tapson VF. Am J Respir Crit
Care Med 1999)
Aspiration
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Obesity, especially central adiposity, is a
significant risk factor for
gastroesophageal reflux disease (GERD).
(Corley DA.Gut 2007)
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Proposed mechanisms include increased
intra-abdominal pressure, decreased
lower esophageal sphincter
pressure,increased frequency of hiatal
hernia, and perhaps alterations in
esophageal motility and gastric emptying
in the obese. (Friedenberg FK. Am J Gastroenterol 2008)
Aspiration
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Histamine H2 antagonists and proton pump
inhibitors might minimize the deleterious
effects of gastric acid aspiration on the lung,
but the loss of the antimicrobial effects of
gastric acid has been suggested as a potential
risk factor for pneumonia. (Nishina K. Anesth Analg 1996)
Elevation of the patient’s head and the use of
special endotracheal tubes that allow for
continuous suctioning of subglottic secretions
may also decrease the risk for aspiration and
VAP , although the use of these devices has
not been studied in obese patients. (Valles J. Ann
Intern Med 1995)
Abdominal Compartment Syndrome
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Obese patients have higher IAP than nonobese control
subjects.
The incidence of clinically significant abdominal
compartment syndrome in critically ill obese patients is
unknown.
The abdominal compartment syndrome should be
suspected in the setting of increased IAP with
attendant poor urine output, respiratory acidosis, or
metabolic acidosis.
In these settings, abdominal decompression should be
considered, with treatment of ileus, large volume
paracentesis, or laparotomy.
CHALLENGES
IN THE CARE
OF
CRITICALLY
ILL
OBESE
PATIENTS
Airway Management
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Morbidly obese patients often have anatomic
changes that make intubation difficult, such as
a short and thick neck, redundant soft tissue
in the oropharynx, and limited mouth opening,
and the availability of two experienced
intubators is preferable.
Several studies have established an
association between increasing BMI and
difficulties with intubation. (Grant P. Emerg Med Australas
2004)
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Proper positioning,with the head elevated
above the shoulders in the ‘‘sniffing position,’’
is important. (Rao SL. Anesth Analg 2008)
Airway Management
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Bilevel positive airway pressure (BiPAP) has been used
to oxygenate patients before rapid sequence
intubation when conventional methods of
preoxygenation have failed to bring the saturation
above 90%. (El-Khatib MF.Can Anesth 2007)
Ultimately,when other advanced airway techniques
fail,skilled operators may need to intubate under fiberoptic guidance or with the aid of newer devices (for
example, LMA CTrach, Airtraq, Glidescope) that allow
for video-assisted intubation without the need to align
the oral and pharyngeal axes.
If such methods are not successful, an emergent
tracheostomy should be considered. (Dhonneur G. Obes Surg
2008)
Central Venous Access
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Because of the distortion of normal anatomic landmarks in obese
patients, establishing central venous access can be timeconsuming and challenging.
In a randomized, crossover study in obese or anticoagulated
patients, real-time ultrasound guidance improved success rates
at cannulation and led to fewer complications. (Gilbert TB. Crit Care Med
1995)
Central Venous Access
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Longer needles (for example, spinal needles) may be required in
obese patients because standard needles may be too short to
clear excessive soft tissue.
Vigilance for infection and catheter-related phlebitis and
thrombosis is important as well because intertriginous folds
predispose these patients to local skin infections.
Surgical Airways
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Longer tubes with sharper angles may be required for
tracheostomy in obese patients because of their increased soft
tissue, but such tubes carry a higher risk of becoming dislodged
or occluded.
Higher complication rates have also been reported with tube
placement itself (whether via a surgical77 or percutaneous
route), although the magnitude of excess risk in experienced
hands is not clear. (Byhahn C.
Anaesthesia 2005)
Hemodynamic Monitoring
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Noninvasive blood pressure monitoring
by cuff sphygmomanometer has
unpredictable accuracy because of
difficulties with cuff size selection.
Inaccuracies may persist, even when an
appropriately sized cuff is available.
(Maxwell MHf.Lancet 1982)
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Hemodynamic parameters are often
adjusted according to body surface
area.
Hemodynamic Monitoring
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Beutler and colleagues highlight the potential
variations in calculated indexed values depending on
weight chosen (actual, adjusted, or ideal), which
could lead to different conclusions regarding a
patient’s status, and, ultimately, treatment.
Ideal body weight is not optimal because oxygen
demand and cardiac output are higher in obese
patients than in nonobese patients.
As a compromise, a 40% adjustment for weight
above ideal body weight is commonly used as in
drug dosing, but no study has rigorously validated
this adjustment.
Imaging and Tests
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Variable lead positioning owing to indistinct landmarks and
excessive soft tissue can lead to low voltages and make accurate
interpretation of electrocardiograms (ECG) difficult.
Specifically,application of ECG-based criteria for the assessment
of left ventricular hypertrophy and chamber enlargements is
limited.
Similarly, image acquisition using an echocardiogram is poor.
Inadequate soft tissue penetration makes interpretation of
portable radiographs difficult.
Imaging and Tests
Confluence of shadows from overlying
soft tissue can mimic abnormalities
such as pleural thickening.
 Distinguishing the nature of parenchymal
opacities (infiltrate versus edema,
for example)
can be difficult.
 Computed tomography (CT) is limited
by load limits of the scanning tables as well as the
diameter of the aperture.
 Some veterinary hospitals have
specialized CT equipment to
accommodate large animals
may be willing to perform scans in morbidly
obese patients who cannot fit into
conventional human scanners.
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Nutritional Support
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Obesity and malnutrition can coexist,
particularly in the setting of critical illness,
and appropriate nutritional support of obese
patients is essential.
Accelerated protein breakdown can lead to a
rapid reduction in lean body mass.
Hypocaloric,high-protein feeding theoretically
prevents overfeeding (and its consequences,
such as hyperglycemia) and allows for net
protein anabolism and secondary fat weight
loss. (Malone AM. Curr Gastroenterol Rep 2007)
Nutritional Support
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Although small studies have suggested
improved morbidity end points with this
approach, including shorter ICU stay and
ventilator days, it remains controversial.
Estimation of the metabolic need of the
critically ill obese patient is difficult.
Some investigators have advocated the use of
an obesity-adjusted weight with a 25%
correction for excess weight above ideal body
weight as follows: adjusted body weight
=(actual weight- IBW) 0.25 + IBW
This approach has not been validated for
standard practice.
DRUG DOSING
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The physiologic changes in obesity markedly affect
distribution, binding, and elimination of medications
commonly prescribed in the ICU.
Although systemic absorption of oral drugs is not
significantly altered in obese patients, the increase in fat
body mass and relative decrease in percentage
contribution of lean mass and water can cause dramatic
changes in the volume of distribution.
Other important changes include increases in total blood
volume and cardiac output, alterations in plasma protein
binding, and obesity-induced changes in liver and
kidney function that may affect drug elimination. (Casati A. J
Clin Anesth 2005)
DRUG DOSING
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For many lipophilic medications, such as aminoglycosides, with
a large volume of distribution, the use of adjusted body weight
is recommended.
The distribution is presumed to be approximately 20% to 50%
of the weight above ideal body weight. A typical calculation
using 40% of excess weight is as follows: adjusted body weight
= (Actual body-weight IBW) 0.41+ IBW
However in the ICU,measurement of weight itself can be
affected by temporary changes in body water from third
spacing, which may or may not influence the distribution of
medications.
Dr. Who’s
Dr. Who’s Adipose
monsters
Shyoko Hoinden.Clin Chest Med
2009
Nursing Care
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All staff caring for the obese ICU patient should be aware of the
potential effect of personal prejudices toward the obese, who
may have insecurities about body image. (Charlebois D.Crit Care Nurse
2004)
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Skin integrity can be particularly problematic in obese patients.
(Winkelman C. Clin Nurs Res 2005)
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Multiple skinfolds can lead to the buildup of moisture, posing a
threat to skin integrity. Limited mobility, difficulty in nurseassisted turning, decreased vascularity within adipose tissue,
and excessive weight all contribute to pressure ulcer risk. (El-Solh
AA.Am J Respir Crit Care Med 2004)
Nursing Care
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Pressure ulcers that begin in skin folds may go undetected during
their early stages unless all such regions are examined carefully
during routine turning.
Patients with a BMI greater than
40 generally require at least four staff
members to assist with
repositioning.
(Hurst S. Dimens Crit Care Nurs 2004)
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Mobilization and rehabilitation in
obese patients may require increased
personnel andequipment.
SUMMARY
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Obesity poses unique challenges for the ICU team.
Important changes in cardiovascular, pulmonary, and
immunologic physiology predispose such patients to respiratory
failure, thromboembolic disease, abdominal compartment
syndrome, and aspiration.
Special attention is required when performing routine ICU
procedures, such as intubation and insertion of central venous
catheters, and limitations in testing capabilities may lead the
astute ICU clinician to rely solely on clinical suspicion when
making therapeutic decisions.
Daily management can be further hampered by uncertainties
regarding drug metabolism and pharmacokinetics, nutritional
needs, and challenges in bedside nursing care.
Dedicated research is much needed in obese patients to allow
for formulation of evidence-based guidelines that would further
enhance delivery of ICU care for this challenging population.
Thank you