48. Laparoscopic cholecystectomy Flashcards
What are the problems associated with anaesthetising a patient for
laparoscopic cholecystectomy?
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
Effects on the cardiovascular system
Haemodynamic changes are secondary to pneumoperitoneum, reverse
Trendelenberg, hypercarbia and the effects of the GA itself:
- ↓ 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
- SVR ↑
Aortic and splanchnic compression may also be due to
humoral factors like catecholamines, PGs and vasopressin - ↑ MAP
- Ischaemia Alterations in supply/demand
- Arrhythmias
Vagally mediated → A-V dissociation
Nodal rhythm
Sinus bradycardia
Asystole
Ventricular – related to high CO2
- Cardiac failure
Effects on the respiratory system
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).
- ↓ FRC
Diaphragmatic displacement cephalad
↓ chest wall dimension and muscular tone
Changes in intrathoracic blood volume
→
Atelectasis
Pulmonary shunting
Hypoxaemia
- ↑ Airway Pressures
Peak airway pressure ↑ 6 cmH20
May result in barotrauma or pneumothorax - ↑ Physiological dead space
- ↓ Total lung compliance
- 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
- Endobronchial intubation
The carina moves upwards during insufflation
May also manifest as bronchospasm
Effects on the renal system
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.
Additional potential problems
Acid aspiration
Trocar injuries
Venous gas embolism
Bleeding
Burns and explosions
DVT