48. Laparoscopic cholecystectomy

Question 1

What are the problems associated with anaesthetising a patient for
laparoscopic cholecystectomy?

Answer 1

The problems associated with laparoscopy are caused by:

Pneumoperitoneum

CO2 used as the insufflation gas

Positioning on the table, i.e. reverse Trendelenberg

Surgical procedure itself, i.e. cholecystectomy.

These can be discussed in terms of their physiological effects on the
cardiovascular and respiratory systems in particular.

Other, less important
changes are also seen in renal, metabolic and neuro-endocrine physiology

Question 2

Effects on the cardiovascular system

Answer 2

Haemodynamic changes are secondary to pneumoperitoneum, reverse
Trendelenberg, hypercarbia and the effects of the GA itself:

1. ↓ Cardiac Index

↓ venous return by compression of IVC and reverse Trendelenberg position

Paradoxically, CVP and PCWP ↑ –
may be a result of central redistribution of blood
or ↑ intrathoracic pressure

2. SVR ↑
   Aortic and splanchnic compression may also be due to
   humoral factors like catecholamines, PGs and vasopressin
3. ↑ MAP
4. Ischaemia Alterations in supply/demand
5. Arrhythmias

Vagally mediated → A-V dissociation
Nodal rhythm
Sinus bradycardia
Asystole
Ventricular – related to high CO2

6. Cardiac failure

Question 3

Effects on the respiratory system

Answer 3

These effects are mainly due to pneumoperitoneum and the use of CO2 as the
insufflation gas.

Reverse Trendelenberg position actually attenuates some of
the adverse effects (cf. Trendelenberg for gynaecological surgery).

1. ↓ FRC
   Diaphragmatic displacement cephalad
   ↓ chest wall dimension and muscular tone

Changes in intrathoracic blood volume

→
Atelectasis
Pulmonary shunting
Hypoxaemia

2. ↑ Airway Pressures
   Peak airway pressure ↑ 6 cmH20
   May result in barotrauma or pneumothorax
3. ↑ Physiological dead space
4. ↓ Total lung compliance
5. CO2 absorption
   ETCO2 rises by 8–10 mmHg then plateaus at
   new level after about 40 minutes

Respiratory acidosis with CVS consequences if
not corrected

Usually need 25% ↑ in minute volume

6. Endobronchial intubation
   The carina moves upwards during insufflation
   May also manifest as bronchospasm

Question 4

Effects on the renal system

Answer 4

As cardiac output reduces so too will renal blood flow and GFR. Renal vascular
resistance will increase with the raised intra-abdominal pressure. These factors
may lead to an overall reduction in urine output particularly with a prolonged
procedure.

Question 5

Additional potential problems

Answer 5

Acid aspiration
Trocar injuries
Venous gas embolism
Bleeding
Burns and explosions
DVT