2.6 Pneumoperitoneum Flashcards
What are the causes of increased co2 intra-operatively?
- Hypoventilation
- Rebreathing
- Sepsis
- Malignant hyperpyrexia (MH)
- Skeletal muscle activity/hypermetabolism
- CO2 insufflation
How would you manage this?
- Increase ventilation
- Change soda lime or increase flows
- Increase depth of anaesthesia, muscle relaxants
- Specific treatment of MH
What are the causes of raised co2 during a laparoscopic procedure?
- Hypoventilation
- CO2 insufflation
- CO2 embolism
Are there any contraindications for laparoscopic procedure?
Medical contraindications to laparoscopic surgery are always relative.
Successful laparoscopic surgery has been performed on
anticoagulated,
pregnant,
morbidly obese patients.
What are the specific anaesthetic issues for laparoscopic procedures?
- Pneumoperitoneum and its effects
- Positioning: extreme head up or head down
- Surgical issues: trauma of a viscus, vascular trauma
What are the problems with gas insufflation?
CVS
- Cardiovascular
- ° ↓ cardiac index:
↓venous return due
to compression of IVC
and Trendelenburg position - ° ↑ SVR:
Aortic and splanchnic compression - ° ↑ MAP
- ° Ischaemia:
alteration in supply and demand - ° Arrhythmia:
Vagally mediated and ventricular due to high Co2 - Cardiac failure
What are the problems with gas insufflation?
Respiratory
- ° ↓ FRC
- Diaphragmatic splinting and cephalad displacement
- Atelectasis
- Pulmonary shunting
- Hypoxaemia - ° ↑ Airway pressures: barotrauma or pneumothorax
- ° ↑ Co2: Rises by 1 kPa—needs 25% increase in minute volume
- ° Endobronchial intubation
- ° Gas embolism: Rare and Co2 is safe
What are the problems with gas insufflation?
Renal
GI
- Renal effect:
↓ Renal blood flow and GFR
GI
* Acid aspiration
At what pressures is a healthy patient at risk of cardiovascular compromise?
> 20 mmHg
> 30 mmHg, Cardiac index might fall by 50%
What are the issues with positioning?
- Head up: Hypotension and cerebral hypoperfusion
- Head down: Cerebral oedema, retinal detachment (long operations)
- Soft tissue damage due to pressure;
e.g. Brachial plexus injury with
pressure on the shoulder and
neck if used with harness to prevent the
patient from slipping down with extreme head down.
What are advantages of laparoscopic surgery?
Pros:
- Pulmonary function better preserved following laparoscopic surgery;
FVC‚ 27% after laparoscopic surgery and by 48% after open surgery
- Less painful, earlier discharge from hospital
- Cosmetic appealing surgical scars
What are disadvantages of laparoscopic surgery?
Cons:
- Postoperative nausea and vomiting—
50% of patients require antiemetics,
so prophylactic antiemetics may be given routinely - Pain following laparoscopic surgery
consists of early transient vagal abdominal
and shoulder discomfort
due to peritoneal irritation by residual carbon dioxide
What are the factors that determine the morbidity in gas/air embolism? x 3
- Volume of gas entrainment:
The closer the vein of entrainment is to the
right heart, the smaller the lethal volume.
- Volume of gas entrainment:
As little as 0.5 mL in Lt anterior descending artery or
2 mL in cerebral circulation is fatal.
Traditional estimation is 5 mL/kg
- Rate of accumulation: > 0.30 mL/kg/min
- Patient’s position at the time of the event
What is the pathophysiology of gas embolism?
- Pressure effect:
- Inflammatory effect:
- V/Q mismatch:
Pressure effect:
Air entering the systemic venous circulation
puts a substantial strain on the right ventricle,
and rise in pulmonary artery pressures.
____
This increase in PA pressure can lead to
right ventricular outflow obstruction
and decrease pulmonary venous return to the left heart,
which in turn would lead to resultant
decreased cardiac output and
eventual systemic cardiovascular collapse.
