Anesthetic approach toOBESE PATIENTS

From the basic to

UpToDate recommendations

Prof. Alexander Ioscovich

Chair of the obstetric and ambulatory anesthesia department,

Shaare Zedek Medical Center,

Hebrew University, Jerusalem Israel

The Future is BIG!

The Global Obesity Epidemic

2008

2013

What is Obesity?

Metabolic disorder: primarily induced and sustained by an over

consumption or under utilization of caloric substrate.

Quantifying Obesity

•The Broca Index:

➢ IBW (kg): For Female = Height (cm) – 105

For Male = Height (cm) – 100

•BMI:

➢ Body Weight (kg)/ Height2 (m)

Quantifying Obesity

• Overweight: BMI >24 kg/m2

• Obesity: BMI >30 kg/m2

• Extreme obesity ("morbid obesity") : BMI >40 kg/m2

Definitions BMI

(kg.m-2)

18.5-24.9 Ideal Weight

25-29.9 Overweight

30-34.9 Obese

35-49.9 Morbidly Obese

50-59.9 Super Obese

60-69.9 Super Super Obese

>70 Hyper Obese

Incidence

•Worldwide adult population: 7%

•In affluent cultures, the poor have the highest prevalence (27% US and 17% UK population)

•In Developing world, affluent are at the highest risk.

•Obese US school children: 60-85%

Causes

•Genetic predisposition• Sex: 35% (men); 40% (women)• Race •Economic status •Psychological •Environmental•Emotional• Cultural

> 2 milliards people overweight or obese!!!

Anatomy of Obesity

thighs

Obesity

✓Android obesity

✓Truncal distribution of adipose tissue

✓Associated with an increase in oxygen consumption and an increased incidence of cardiovascular disease

✓Intra-Abdominal fat is particularly associated with cardiovascular risk and left ventricular dysfunction

✓Gynecoid obesity

✓Adipose distribution in the hips, buttocks, and thighs

Effects of Obesity

•Cardiovascular Changes:

• Increased blood volume and cardiac output leading to cardiomegaly, left ventricular hypertrophy and a potential for left ventricular failure.

• Hypertension and ischemic heart disease

• Venous access can sometimes be difficult.

•Thromboembolism risk is increased (X2).

Cardiovascular effects

Impaired Cardiac

Contractility

RV Dilatation

LV Hypertrophy

Independent Risk

CAD

Effects of Obesity

•Respiratory changes:•Reduced compliance and reduced FRC will pre-

dispose to atelectasis, increased shunt and hypoxia.

•Pulmonary vasoconstriction, pulmonary hypertension and right ventricular hypertrophy.

• Increased work of breathing.

•Oxygen consumption and carbon dioxide production are increased

Effects of Obesity

•Obstructive sleep apnea- 5% • RISK FACTORS: Large collar size, Evening alcohol

consumption, Pharyngeal abnormalities• PATHOPHYSIOLOGY :Passive collapse of the

pharyngeal airway during deeper planes of sleep. • CLINICAL FEATURES: Snoring and intermittent airway

obstruction

Resultant hypoxemia and hypercapnia Arousal and disruption of sleep: Daytime somnolence.

Effects of Obesity

OBESITY HYPOVENTILATION SYNDROME

• Pickwickian syndrome = OSA (?!)• Loss of the sensitivity to hypercarbia resulting in

a combination of hypoxia, Cor Pulmonale and Polycythemia, •Diagnosis –Polysomnography (Apnea-Hypopnea

index • 5-15 is ‘mild OSA• 15-30 ‘moderate’, • and ‘severe OSA’ is over 30

Effects of Obesity

•Gastrointestinal Changes: • Increased acidity and volume of gastric contents.

• Hiatus hernia and gallstones are common

• Increased intra-abdominal pressure.➢ There is a higher risk of regurgitation and

aspiration requiring rapid sequence induction.

➢ Tracheal extubation should be undertaken with the patient awake.

Effects of Obesity

•Endocrine Changes:•Association with glucose intolerance.

•Hypercholesterolemia

•Hypothyroidism

Effects of Obesity

•Obesity associated with:

•Type II diabetes

•Several forms of cancer diseases

•Almost all forms of CV diseases

•Asthma

•Gallbladder disease

•Osteoarthritis

•Chronic back pain

Drug Handling in Obesity

❖Unpredictable Volumes of distribution

❖Higher fat mass

❖Reduction in total body water

❖Binding

❖Elimination of drugs

❖Higher lean mass

❖ Higher GFR and Increased renal clearance

Effects on Drug Distribution

•Volume of Distribution in Obese patients is affected by:

• Increased total body fat

• Increased lean body mass

•Altered protein binding

• Increased blood volume

• Increased cardiac output

Effects on Drug Distribution

•Hepatic clearance is not usually affected (!!!)

•Renal clearance of drugs is increased in obesity because of increased renal blood flow and glomerular filtration rate

Preoperative Evaluation

•Medical history taking and physical examination:•Standardized scheme: special focus on OSA

•Laboratory testing:• According to pre-existing medical conditions: screen for

metabolic syndrome

•ECG: if cardiac risk factors, clinical signs of CV disease, high or intermediate risk surgery.

•Spirometry: OSA or other respiratory findings

Premedication

•Patient’s usual medications, except oral hypoglycemics, be continue until the time of surgery.

•Antibiotic prophylaxis; increased risk of postoperative wound infection. (> 130kg +50% AB)

•Prophylaxis against aspiration pneumonitis: H2-receptor antagonists (e.g. ranitidine), nonparticulate antacids (e.g., sodium citrate) and proton pump inhibitors (e.g. omeprazole) will reduce gastric volume, acidity, or both, thus reducing the risk and complications of aspiration.

•NO sedatives or narcotics should be given to an Obese, Pickwickian patient as premedication

• Light sedation (?)

•Anxiolysis: Oral benzodiazepines or IV midazolam in immediate preoperative period

•Nonsedative premedication, such as an anticholinergic used to dry the upper airway, and metoclopramide, a prokinetic, is given at this time to increase gastric emptying, because peak effects occur in approximately 45 minutes.

Premedication

Effects of Obesity

•This presents the anesthesiologist with a patient who may be:

• difficult to bag-mask ventilate,

• difficult to intubate

• and will desaturate quickly.

Upper Airway Assessment

•Atlanto-occipital joint extension

• Mallampati classification

•Temporo-mandibular joint (TMJ) assessment with interincisor distance

• Mento-hyoid distance

•Pretracheal adipose thickness

•Neck circumference

•Hypertrophic tonsils and adenoids.

Extension Evaluation

Airway management

•Video laryngoscopy

• Awake fiberoptic intubation (?)

• Consider asking for Assistance

Ramped Position

Ramped Position

Special Considerations

•A typical operating table will support 150 kg, but the tilting/tipping may not function.

•NIBP - The cuff width should be 20% greater than the diameter of the arm

•Invasive blood pressure monitoring may be required.

• Heparin, 5000 IU subcutaneously, administered before surgery and repeated every 12 h until the patient will be fully mobile

• low molecular weight heparins (LMWH) injected subcutaneously 40 mg every 12 h result in a decreased incidence of postoperative DVT complications (ASAP 6-8H)

• TED Stockings

• Pneumatic Stockings

• Early mobilization

Institutional protocol !!!

DVT Prophylaxis

Induction of General Anesthesia

•Adequate preoxygenation •Rapid desaturation because of increased

oxygen consumption and decreased FRC•Positive pressure ventilation during

preoxygenation decreases atelectasis formation and improves oxygenation

Pre-Oxygenation Options

Oxygen Flow 6 l/min

CPAP + PEEP 10 cm H20 High Flow

Oxygen 40 l/min

Patient positionThe head-up (reverse Trendelenburg) position provides the longest safe apnea period during

induction of anesthesia

Fi02=15 L/min

Apneic Oxygenation via standard nasal cannula(SNC) prolongs Safe Apnea Time

(Sp02 = 88-90 %) during laryngoscopy.

Joshua M. Gleason,UC Irvine Health, 2017

Cricoid Pressure Dilemma

•Obesity- Risk Factor #1 for aspiration

• 56 % aspiration

due to induction

•RSI- Standard of Care

Sellick maneuver (1961)

Cricoid Pressure & Laryngoscopy View

0

5

10

15

20

25

0-10N 10-20 N 20-30 N 30-40 N

Improved

Same

Worsened

Haslam N.:Anaesthesia,60(1),2005

N

1 kg = 9,8 N

Cricoid Pressure & Laryngoscopy View

MRI data:

90% esophagus displaced laterally

67% airway displaced laterally

81% airway compressed by 1 mm

In an elective, fasted, obese patient with no other

risk ,the need for RSI and CP is debatable

Thomas Ebert , ASA 2010

Sugammadex for failed intubation

2010

Cannot

intubate

Cannot

oxygenate

Prepare for

surgical

airway

Position & Obesity

IVC compressionreduced preload, CO, SV,

regional blood flow

Gluteal muscles injury

Rhabdomyolysis

Acute Renal Failure

Intraoperative Patient Positioning

•Supine•Causes ventilatory impairment and inferior vena

cava and aortic compression•Trendelenburg

•Further worsens FRC and should be avoided (!?)•Prone

•Detrimental effects on lung compliance, ventilation and arterial oxygenation• Increased intra-abdominal pressure worsens IVC

and aortic compression and further decreases FRC•Reverse Tredelenburg

• Increased compliance results in lower airway pressures

Intraoperative Management

IBP CVP (?)

ABG T0C

PNS BIS TEE

Pharmacokinetics

Anthropometric Dilemma:

IBW- inadequate anesthesia and under dosing

TBW- adverse hemodynamics and overdose

Dosing Scalar: TBW, IBW, BSA, BMI

LBW( lean)

J.Ingrande, Brit J Anaest, 105, 2010

LBW( lean)=TBW- Body Fat

60-90% from the TBW

Intraoperative Fluids Management

• Amount and Timing of Rehydration - Key Factors for perioperative cardiovascular & renal stability

Euvolemia before induction based on IBW

• Fluid maintenance on IBW/h :Crystalloids- 11-13 ml//kg (5-10mL/kg)Colloids (?) - 6 ml/kg Urinary output > 2 mL/kg/h (?)

Brodsky J,Int Anesth Clin 2014

Lung Protective Ventilation

•Pressure- controlled ventilation ( PCV)

•Low tidal volume ( 6-8 ml/kg IBW)

•PEEP 10-15 cm H20

•Mild hypercapnia ( ETC02 40 mm Hg)

•Recruitment maneuvers (!!!) 7-8 sec, plateau pressure ~40-55 cm H20

•Reverse Trendelenburg whenever possible

Cadi, P. Br. J. Anaesth, 2008

Surgical and Mechanical Issues

❖Reduced surgical access

❖Difficult visualization of underlying structures

❖Excess bleeding

❖Longer operating times (CSE versus Spinal)

❖Higher risk of infection

❖Wound dehiscence

Postoperative Complications

• Postanesthetic hypoxemia

• Respiratory depression

• Early ventilatory failure with need for reintubation

• Positional ventilatory collapse

Extubation in OR

• Safe & Rapid Extubation in OR

• CPAP + PEEP OR & PACU & ICU

• Promote shorter Hospital Stay

Extubation in OR

• Increased risk and close monitoring opioid-induced upper airway obstruction

• Lipophilic opioids [fentanyl, alfentanil, sufentanil] more potent, rapid onset, short duration

• Morphine titration used with caution

• Multi-modal analgesic strategy

• RA

Residual neuromuscular blockade is commonly observed in the postanesthesiacare unit (PACU) when neuromuscular blocking drugs (NMBDs) are administered intraoperatively. Despite the application of techniques proven to limit the degree of residual paralysis (i.e., use of intermediate-acting NMBDs and pharmacological reversal), up to 33%– 64% of patients have evidence of inadequate neuromuscular recovery on arrival to the PACU.

Residual Neuromuscular Blockade and Critical Respiratory Events in the Postanesthesia Care Unit

ANESTHESIA & ANALGESIVol. 107, No. 1, July 2008A

•Opioid–free TIVA reduced PONV

•Dexmedetomidine replace Fentanyl

•Reduction volatile and opioids

reduced PONV in 46,4%

Regional Anesthesia

• Obese patients should not be

excluded from RA

• Obese patients RA success

94.3%

Advantages R A

• Stable hemodynamics

Low Opioid &

Inhalation agents

• Minimal Airway

intervention

Early Extubation &

Rapid emergency

• Reduced CR complications

Less PONV

Short PACU &

hospital stay

Disadvantages R A

• Special equipment

• Poor landmarks

• Skin-spinal canal distance

• False positive L of R

• Ultrasound technique

• High block & Breathing

• Decreased ability to cough

• Psychological stress, anxiety

1- st Case for discussion

•You are asked to assess a 42-year old woman who requires an emergency extensor repair to her left hand. There is no neurovascular deficit.

•She is 158 cm tall and weighs 112 kg. She last ate 2 hours ago .

•What factors will you specially need to consider in her pre-assessment?

•BMI = 41

•Not adequately fasting

•Not an emergency

•Delayed for at least another 4 or 6 hours

•Symptoms of: sleep apnea, GE reflux, diabetes, IHD, exercise tolerance?

•Airway!!!

•Lab: glucose, ECG, pulse oximetry, BP

•Option: regional technique !!!

•If GA: intubation

2-nd Case for discussion

•A 55-year old man with a BMI of 37 is having an anterior resection for colon cancer.

•20 minutes into the case you notice his oxygen saturations are falling and are now 88% despite FiO2 0.5.

•What actions can you take to improve his oxygenation?

•Increase the FiO2 to 1.0 immediately

•Appropriate increase in volatile agents

•Check position of the ET Tube, auscultation and capnography

•Recruitment maneuver

•If not already applied, add PEEP

•If surgery allows, reverse Trendelenburg position

3 – rd Case for discussion

•A 65-year old woman with a BMI of 41 is 24hours post an elective total knee replacement. She has been given IV Morphine 2h early. She is hypoxic with a saturation of 87% on room air. Her respiratory rate is 8 breaths per minute.

•What is your diagnosis and action plan?

•Respiratory depression from opioid

•Sleep apnea, sensitive to the effects of opioids

•Imminent danger of respiratory arrest

•100% oxygen, assist ventilation with a bag

•IV Naloxone: 100-200 µg up to 400 µg continuous infusion

•Naloxone: shorter half-life than morphine

•Close monitoring of respiratory rate, sedation score and SaO2

Thank you and Welcome to Israel!