Chapter 18-1 - Hyperbaric O2

Question 1

List indications for hyperbaric oxygenation.

Answer 1

Air gas emboli

Decompression sickness

CO Poisoning

Crush injury/traumatic ischemia

Severe blood loss without transfusion ability

Delayed radiation injury

Skin graft

Thermal burn

Arterial insufficiency

Necrotizing infection

Gas gangrene

Osteomyelitis

Intracranial abscess

Question 2

What are the mechanisms by which HBO exerts its benefits?

Answer 2

1. Increased PO2 - hyperoxygenation including to areas inaccessible to RBCs, vasocontriction, improved wound healing, antimicrobial synergyism, toxic radial suppression.
2. Pressure - decreased size of air bubbles and displacement of nitrogen.

Question 3

What are important considerations when using HBO for CO poisoning?

Answer 3

100% O2 @ 3 ATM will decrease half life of carboxyhemaglobin from 300 min (21% @ 1 atm) to 30 minutes.

If CN was a coexposure note that nitrites in the CN kit will reduce O2 carrying capacity by forming metHb, and also that hyperbaric O2 will decrease efficacy of antidote as it reduced formation of metHb.

Question 4

What bacterial species cause gas gangrene?

Answer 4

Clostridium septicum - spontaneous gas gangrene, especially in colon cancer.

Clostridium perfringens - 80-90% of cases. Trauma and wounds.

Question 5

What investigations are required before starting HBO treatment for DCS?

Answer 5

Chest xray to rule out pneumothorax.

Question 6

How much air can be filtered by the pulmonary vasculature if introduced in the venous side of circulation?

Answer 6

Approx 30mL/min

Larger volumes by cause obstruction and cardiac arrest.

Question 7

Outline the acute management of an air/gas embolus?

Answer 7

Left lateral decubitus positioning to trap air in right ventricle

Supportive measures

Lidocaine 1.5mg/kg IV bolus followed by infusion at 2-4mg/min

HBO is definative.

Question 8

What are the complications of HBO?

Answer 8

CNS - paresthesias, seizures

Resp - decrease mucous velocity, decrease VC/DLCO, compliance. Generally short (90-120min) sessions are not associated with these effects.

Optho - myopia, cataracts

Barotrauma - ears, sinus, teeth. Usually resolves spontaneously.

Question 9

List the absolute contraindications for HBO.

Answer 9

Untreated pneumothorax

Bleomycin within 3 months

Cisplatin/Carboplatin (only if used for wounds)

Doxorubicin within 7 days

Disulfram use

*There are many relative CI’s