Page 10 - Textbook of Practical Laparoscopic Surgery by Dr. R. K. Mishra

CHAPTER 6: Abdominal Access Techniques 9

A B
Figs. 21A and B: Quadromanometric indicators.

3. Gas flow rate Actual pressures of >20–25 mm Hg has following
4. Volume of gas consumed. disadvantage over hemodynamic status of patient.
■ ■Decrease venous return due to vena caval compression
Preset pressure: This is the pressure adjusted by surgeon
before starting insufflation. This is the command given by leading to:
z ■ Increased chance of deep vein thrombosis (DVT)
surgeon to insufflator to keep intra-abdominal pressure at
this level. of calf
z ■ Hidden cardiac ischemia can precipitate due to
The preset pressure ideally should be 12 mm Hg. In any
circumstance, it should not be >18 mm Hg. Good quality ■ decrease cardiac output
insufflator always keeps intra-abdominal pressure at preset ■ ■Decrease tidal volume due to diaphragmatic excursion
pressure. Whenever intra-abdominal pressure decreases ■Increase risk of air embolism due to venous
due to leak of gas outside, insufflator eject some gas inside ■ intravasation
to maintain the pressure, equal to preset pressure. If intra- ■Increased risk of surgical emphysema.
abdominal pressure increases due to external pressure; Flow rate: This reflects the rate of flow of CO through
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insufflator sucks some gas from abdominal cavity, to the tubing of insufflator. When Veress needle is attached,
maintain the pressure to preset pressure. When surgeon the flow rate should be adjusted to 1 L/min. Studies were
or gynecologist wants to perform diagnostic laparoscopy performed over animal in which direct intravenous (IV)
under local anesthesia, the preset pressure should be set CO were administered, and it was found that risk of air
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to 8 mm Hg. In some special situation of axilloscopy or embolism is less if rate is within 1 L/min. At the time of
arthroscopy, we need to have pressure > 19 mm Hg. access using Veress needle technique, sometime Veress
needle may inadvertently enter inside a vessel but if the flow
Actual pressure: This is the actual intra-abdominal pressure
sensed by insufflator. When Veress needle is attached, rate is 1 L/min there is a less chance of serious complication.
there is some errors in actual pressure reading because When initial pneumoperitoneum is achieved and cannula
of resistance of flow of gas through small caliber of Veress is inside abdominal cavity, the insufflators flow rate may be
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needle. Since continuous flow of insufflating gas through set at maximum, to compensate loss of CO due to use of
Veress needle usually gives extra 4–8 mm Hg of measured suction irrigation instrument. This should be remembered
pressure by insufflator, the true intra-abdominal pressure that if insufflator is set to its maximum flow rate then also
can be determined by switching the flow from insufflator it will allow flow only if the actual pressure is less than
off for a moment. Many microprocessors controlled good preset pressure otherwise it will not pump any gas. Most
quality insufflator deliver pulsatile flow of gas when Veress of the surgeons keep initial flow rate with Veress needle
needle is connected, in which the low reading of actual to 1 L/min and as soon as they confirm that gas is going
pressure measures the true intra-abdominal pressure. If satisfactorily inside the abdominal cavity by percussion
examination and seeing obliteration of liver dullness (Fig.
there is any major gas leak, actual pressure will be less, and
insufflator will try to maintain the pressure by ejecting gas 22), then they increase flow rate to 3 L/min. No matter how
through its full capacity. much flow rate you set for Veress needle, the eye of normal