Gas embolism Flashcards
(45 cards)
Name 6 procedures that can cause gas embolism in veterinary patients?
- Intravenous injection
- laparoscopy
- bronchoscopy
- hyperbaric therapies
- lung biopsies
- cardiac procedures
These procedures are gaining popularity in veterinary medicine and can introduce air into the venous circulation.
What factors determine the severity of gas embolism pathophysiology?
- Size of bubble
- rate of intravenous gas entry
- physiologic status of the patient
These factors interact to influence how severely a patient is affected by gas embolism.
Where does air lodge in the venous circulation during gas embolism?
RA or PA
Gravity dependent - air weighs less than blood so it “floats” in a direc- tion opposite to gravity
Air floats in a gravity-dependent location, leading to these specific areas.
What can small air emboli cause in the pulmonary vessels?
- Ventilation–perfusion mismatching (high V/Q)
- pulmonary hypertension
These conditions arise due to the obstruction caused by air emboli in the lungs.
Name 2 vulnerable locations for emboli that have severe consequences?
- Cerebral vasculature
- coronary artery
Emboli in these areas can lead to critical issues such as hypoxia.
Explain the term “massive embolism” and its origin
small emboli coalesce into larger air pockets –> massive air embolism –> creates an absolute obstruction to blood flow in the herat.
Compressible envelope of air contracts and expands with the working of the heart, –> no blood can enter into air-filled RV –> CPA
This can lead to massive air embolism, significantly complicating the patient’s condition.
How does the solubility affect the clinical consequences of gas embolism?
type of gas impacts amount of ischemia
extremely insoluble gases (such as nitrous oxide) exacerbates gas emboli –> insoluble gas escapes from the blood supply and diffuses into the air pockets, causing expansion
–> NO should be avoided in laparoscopy and CPB
This process can reduce the volume of the embolus until it is dissolved or moved to a distal tissue bed.
What is the primary function of the lungs in relation to venous air emboli?
The lungs serve as the primary sponge for venous air emboli
This function helps to salvage the lungs from significant damage from smaller air emboli.
What percentage of dogs experience air embolism when infused with 0.35 ml/kg/min of air?
50%
The air is primarily composed of nitrogen, which is an insoluble gas.
Name 6 consequences of lodging air emboli in the lungs?
- Focal injury
- Edema
- Release of vasoactive mediators
- Alveolar collapse
- Atelectasis
- Impaired gas exchange
These effects can lead to significant respiratory issues.
What vascular changes are prevalent with nitrogen emboli?
- Platelet activation
- Complement response
- Leukocyte adhesion
- Endothelial cell damage
These changes appear to be mediated by mitochondrial dysfunction.
What is the air delivery rate associated with bubbles breaking through to the arterial system in pigs and dogs?
pigs: 0.1 ml/kg/min
dogs: up to 0.3 ml/kg/min
What factors increase the risk of air embolism?
- Use of a venous access site higher than the heart
- Jugular catheterization in standing animals
- Use of ear catheters
- Patients in lateral recumbency
What is the primary composition of an embolus that occurs in room air and why is it more danagerous than oxygen or CO2?
Nitrogen gas –> poorly soluble in tissues, taking longer to dissipate
How can collapsible intravenous fluid bags be safer than rigid bottles?
Rigid bottles have unlimited access to air and cause continuous leak
What increased caution is warranted in patients with a right-to-left cardiac shunt? What are sequelae?
Air bubbles may enter the arterial system without being filtered by the lungs –> Focal cerebral or coronary infarcts
What is the primary gas used for inflation during laparoscopy and why?
- carbon dioxide –> highly soluble in tissues –> air bubbles of carbon dioxide rapidly resolve
- CO2 does not produce bronchoconstriction or changes in pulmonary compliance to the same degree as nitrogen
Carbon dioxide is chosen because it is highly soluble in tissues, allowing for rapid resolution of gas bubbles.
What is the incidence range of carbon dioxide emboli in humans?
0.001% to 0.59%
This low incidence is due to the rapid absorption of carbon dioxide into tissues.
When can laparoscopy cause air embolism?
When gas exists at a pressure midway between venous collapse + IV pressure –> free to move into vasculature. Therefore at the pressure used (15 mmHg) veins should hemorrhage when perforated and not entrap air.
This comparison highlights the risks associated with gas embolization.
What percentage of patients undergoing laparoscopic hysterectomy experienced emboli in a study? How many were grade II (occupying one half of the structure)?
100% in RA, RV, RVOT
grade III: 37%
All patients had emboli in the right atrium, right ventricle, and right ventricular outflow tract.
What is the recommended maximum inflation pressure during laparoscopy? What happens at higher pressures to veins?
maximum inflation pressure: 15 mm Hg
20-30 mmHg: veins collaps
Inflation pressures higher than this are not recommended to avoid complications.
What is the fatality rate of massive embolism in human patients during laparoscopy?
28%
This rate may be significantly higher in veterinary patients.
What helps in early detection of air embolism?
- Slowing the rate of abdominal insufflation to less than 1 L/min –> allows more time for pulmonary clearance of air bubbles
A slower insufflation rate allows more time for pulmonary clearance of air bubbles.
What is the insufflation rate capable of causing arrest in 60% of dogs studied?
1.2 ml/kg/min
This rate is very close to the recommended insufflation rate.
