Respiratory insufficiency in bariatric patients

Special considerations or just

more of the same? Weaning and rehabilation conference 6th November 2015

Definition of obesity

Underweight BMI< 18

  Normal weight BMI 18-25

Overweight BMI > 25

Obesity BMI > 30

  Morbid obesity BMI > 40 or comorbidities

Perspective

Globally 1,9 billion are overweight (BMI>25)

  600 mio are obese (BMI>30)

  Compared to 800 mio starving

  20-30% of ICU patients have a BMI > 30

  WHO 2015

Physiology in the obese

Increased abdominal pressure and thoracic weight

Reduced compliance – worsened in suppine position and during sedation   Changes in diaphragma

Weight of heart

Increased thoracic blood volume

Increased FiO2

Loss of muscle tone/power

Physiology in the obese

Reduction in end expiratory lung volumes

Reduction in functional residual volume – FRC: – 2 liters at BMI 25; 1 liter at BMI 35

Reduction of EELV below closing capacity causes collapse of bronchioli

Atelectasis – impaired gas exchange, ie shunt and hypoxemia

  Compliance reduced: - 75 cmH2O at BMI 25; 50 at BMI 35

Complications to mechanical ventilation

  Expiratory flow limitation: airway collapse (PEEPi)

Prolonged expiration

Increased incidence of asthma and bronchospasm

  VILI – ventilator induced lung injury caused by repetetive opening and closing of og collapsed alveoli

Complications to anesthesia – not ICU

  Postoperative complications 5 % in Morbidly obese are not increased (except 1 study)

When Intubation is needed postoperatively, increased risk of ARDS (not mortality)

Ventilator strategy

  No evidence for particular ventilator mode

  KEEP THE LUNG OPEN

Lowest FiO2 to mantain physiologic oxygenation

  PEEP (10-15) after RM (up to 55-60 cmH2O 6-8 secs)

  Sighs

Vt? IBW 6-8 ml/kg   The lung does not grow with increased Body Mass

Date of download: 10/25/2015 Copyright © 2015 American Society of Anesthesiologists. All rights reserved.

Fig. 3. Representative computerized tomography (CT). A CT scan 1 cm above the diaphragm in the three different groups at all four time points. Note the sustained effect of RM + PEEP and the transient effect of RM + ZEEP. PEEP = positive end-expiratory pressure; RM = recruitment maneuver; ZEEP = zero end-expiratory pressure.

Figure Legend:

From: Prevention of Atelectasis in Morbidly Obese Patients during General Anesthesia and Paralysis:A Computerized Tomography Study Anesthesiology. 2009;111(5):979-987. doi:10.1097/ALN.0b013e3181b87edb

To PEEP or not to PEEP

Beware of hyperinflation

Zimbabwe 2008

Co morbidities

Obesity is correlated to a wide range of other diseases

Anxiety – depression

Ischemic heart disease, hypertension

  COPD

  Diabetes mellitus

Chronic inflammatory state

Increased risk of acute kidney injury – oedema

Special considerations

Obesity hypoventilation Syndrome – OHS   PaCO2> 5,9 kPa (45

mmHg) + BMI > 30

Exclusion of other reasons for hypercapnia

Malignant OHS •  When BMI > 40

Obesity supine death syndrome

Prepare for extubation

  Minimal sedation

Protocolized sedation and weaning

Prevent neuromuscular weakness because of prolonged ventilation

Treat prolonged expiration to avoid increased WOB and fatigue

Optimize fluid status

Positioning

Position in sitting or half-sitting

Obesity supine death syndrome

McKenzie Anesth Analg 1980 Jan;59(1):81

Postextubation

  NIV could reduce respiratory insufficiency in terms of reduced LOS in ICU and hospital. Mortality reduction in patients with hypercapnia

  El Sohl; Eur Respir J 2006; 28.588-595

Common reintubation – what rate is acceptable

Outcomes

Overweight is not related to increased mortality but

  Longer length of stay (LOS) 1,5 day and

  Ventilator 1 day

  Low BMI increases mortality!

Moderately overweight (BMI 30-40) might have a lower mortality RR 0,86 (CI 0,81-0,91; p < 0,001)

Akkinusi et al CCM 2008. Metaanalysis

Special considerations

Prevent or treat overt pain and anxiety

  A priori higher PEEP. Allow for longer expiration

Prepare before mobilization and exercise Optimize blood pressure and cardiac output. Increase oxygen supply and ventilation if needed. Treat bronchospasm as needed.

Evaluate thoroughly before weaning and extubation

Consider NIV for postextubation profylaxis Especially with hypercapnia or for exercise

Key Points

  Generally same challenges in obese patients as those with normal weight.

  The obese patient with respiratory insufficiency has an increased risk of a more difficult weaning from the ventilator and thus longer time on mechanical ventilation

We need to take precautions in order to avoid further complications. These are the same measures as in any other patient with difficult weaning

Though a longer stay in the ICU the bariatric patient does not have an excess mortality (overweight might even be protective).

Thank you