Anaesthesia and BMI

Recovery Complications in Patients with higher BMI

Origins of Anaesthesia

an ~ without

aesthesis ~ sensation

Origins of Anaesthesia

First Anaesthesia

Opium poppy capsules

(herbal remedy)

4200 BC Sumerian Empire

General Anaesthesia

The Common Forms of General Anaesthesia

• Analgesia

• Hypnosis

• Amnesia

• Relaxation

Modern Anaesthesia

Morpheus The Greek God of dreams

Morphine (Purified Alkaloid)

Potent opiate analgesic drug.

Also a natural endocrine product found in humans and other animals.

Morphine acts on the central nervous system (CNS) to relieve pain,

The efficacy of opioids have indicated that, in the management of severe pain, no other narcotic analgesic, other than Fentanyl (which has a higher potency, but is shorter

acting), is more effective or superior to morphine.

Analgesic Agents

Non Opioid

• BarbituratesThiopental

• BenzodiazpinesMidazolamLarazepamDiazepam

• Propofol The most common IV drug to induce and maintain analgesia

Analgesic Agents

Non-Opioid Based

Midazolam

Lorazepam

Used to induce general anaesthesia but

NOT pain relieving!!

Analgesic Agents

Opioid Based

Fentanyl

Remifentanil

Used for the relief of pain in anaesthesia

Obesity Defined

• A condition in which the natural energy reserve, stored in the fatty (adipose) tissue of humans, exceeds healthy limits.

• Definition:-

Body Mass Index

(weight divided by height squared)

30 kg/m2 upwards in Obesity

Obesity and Anaesthesia

Complications in Recovery

Fellow Travellers . . .• Hypertension• Cellulitis• Delayed Wound Healing• Fatty Liver• Type 2 Diabetes• Delayed Gastric Emptying• Sleep Apnea• Gall Bladder Disease

Obesity Risks

• Obesity has been identified as a significant risk factor in anaesthesia

• BMI is only a guideline: Does not account for wide variations in body fat distribution and may not correspond to same degree of fatness in different people

• Any extra fat deposited in the body demands its share of cardiac output. Every 100g of fat deposited increases cardiac output by 50 ml per minute (or roughly quarter of a cup of water)

Airway Problems in Recovery

Normal Airway – Low BMI Restricted Airway – High BMI

Airway Problems in Recovery

Adipose Tissue Problems

• Anaesthetics are “Lipophilic”

• Lipophilic means “absorption in fats”

• Anaesthetics stored in adipose tissue!

Airway Problems in Recovery

Adipose Tissue Problems

• Anaesthetics released back into blood

• Effect: Resedation!

• Be prepared! (Know your A.B.C’s!!)

•Perform head-tilt / jaw thrust

• Nasal / Oral airways nearby

Airway Problems in Recovery

Adipose Tissue Problems

• Anaesthetics and Patient Posture reduce vital capacity and diaphragmatic excursion

• Effect: Hypoventilation and atelectasis (partial lung collapse!)

• Solution: Address pulmonary function!

Posture Problems in Recovery

Attention to Posture

Adopt: Semi recumbent Positioning

Encourage: Coughing, deep breathing, early ambulation

Nausea risk: Pulmonary aspiration of gastric contents because of increased abdominal pressure, reflux and increased gastric volume

The Unexpected

Drug dynamics

Obesity affects drug performance and effectiveness

Excess Fats and Cholesterol block action of drugs

Greater kidney mass increases renal elimination diminishing drug effectiveness

Conclusion

• Beware of abnormal patient recovery

• Anaesthesia affects people differently, especially higher BMI rated people

• Anaesthesia is held in adipose tissues and can be released back into the blood stream, causing more sedation and slower recovery times.

• Prepare for emergencies, especially cardio and pulmonary complications – Know your ABC’s!

• Consider Posture in high BMI patients ~ Semi Recumbent Position if possible

• Appreciate the physiology of high BMI patients and the effects on drug dynamics

Thank you for your attention

~ A teaching session ~

Mark G. Hopewell: Under Graduate Adult

Student Nurse ~ Cohort Sept 05

Venue Kidderminster Intervention Suite

June 2008