2019B11 Describe the respiratory and cardiovascular changes associated with a
carbon dioxide pneumoperitoneum for laparoscopic surgery.



·         Intro

·         Effects of intra-abdominal hypertension

·         Effects of hypercapnoea

·         Effects of position change

·         Miscellaneous complications




·      Steady state insufflation rate 200-400mL/min

·      Pressure 10-20mmHg

Cause of derangements

·      Raised intra-abdominal pressure (↑IAP)

·      Hypercapnoea

·      Positioning

Summary of effects

·      Respiratory:

o  Dose-dependent embarrassment

o  Worse if obese or Trendelenburg)

o  Can be offset by recruitment manoeuvres and PEEP, but at expense of CVS system

·      Cardiovascular:

o  Variable

o  Significantly worse if hypovolaemic


Intra-abdominal hypertension:


·      Cephalad diaphragm displacement -> ↓lung volumes

o  ↓FRC ± closing capacity

o  Small airway closure

o  Atelectasis

o  Shunt

o  Hypoxaemia

·      ↓Lung compliance

o  Restrictive deficit

o  ↑Peak airway pressure

o  ↑Risk of barotrauma

o  Hypoventilation

·      Changes worse if obese, pregnant, Trendelenburg


·      Biphasic effects on venous return

o  At first: autotransfusion of splanchnic blood -> ↑VR -> ↑CO (± initial ↑mAP)

o  Then: compression of IVC -> ↓VR -> ↓CO (more pronounced if hypovolaemic)

·      ↑SVR due to

o  ↑IAP

o  ↑PaCO2 -> ↑catecholamine release

·      Dose-dependent effects on steady-state blood pressure

o  IAP <~20mmHg -> ↑mAP (↑SVR outweighs ↓venous return/cardiac output)

o  IAP >~20mmHg -> ↓mAP (↓venous return/cardiac output outweighs ↑SVR)

·      Effect on myocardial oxygen supply and demand

o  ↑Demand: ↑HR, ↑contractility, ↑stroke work

o  ↑Supply: metabolic autoregulation (but impaired if coronary artery disease)

·      Oliguria

o  ↑IAP ->? renal venous obstruction -> ↓GFR





·      CO2 is rapidly absorbed into systemic circulation (30-50mL/min)

·      Diffuses into rapidly and slowly equilibrating compartments down partial pressure gradient (note large body stores ~120L)

·      CO2 + H2O <-> H2CO3 <-> HCO3- + H+

·      Hence ↑PaCO2 -> ↓pH (whole body including CNS)

·      Prolonged laparoscopy with ↑PaCO2 -> ↑accumulation -> ↑minute ventilation requirement

Respiratory effects

·      Respiratory acidosis

·      Potentiation of HPV

·      Distribution of blood away from poorly-ventilated dependent lung

·      ↑V/Q matching

·      ↑PaO2

·      Hence offsets V/Q inequality caused by small airway closure


·      If pH >7.2: ↑SNS output -> ↑inotropy

·      If pH <7.2: ↓pH -> ↓inotropy

·      ↓pH -> sensitisation of myocardium to arrhythmogenic effects of catecholamines

·      Pulmonary vasoconstriction

·      Systemic vasodilatation (offsets ↑IAP -> ↑SVR)

·      ↑Myocardial O2 demand (↑HR)

·      ↑Myocardial O2 supply (metabolic autoregulation – but impaired if coronary artery disease)




·      Respiratory

o  ± Endobronchial intubation -> massive shunt -> ↓PaO2

o  ↑Diaphragm compression

·      Cardiovascular

o  ↑Venous return: offsets venous compression

Reverse Trend.

·      Respiratory

o  ↓Diaphragm compression

·      Cardiovascular

o  ↓Venous return: compounds venous compression


Miscellaneous complications:

Gas in wrong place

·      Pneumomediastinum

·      Pneumothorax

·      Subcutaneous emphysema

·      Venous gas embolism -> cardiovascular collapse:

o  Either intravascular insufflation directly into vessel

o  Or Venturi effect

CVS collapse at insufflation

·      Peritoneal stretch -> vagal response

o  Sinus bradycardia, nodal rhythm, asystole)

·      Empty ventricle -> Bezold-Jarisch reflex

o  Contraction of underfilled LV

o  Stimulation of unmyelinated PSNS C fibres

o  ↑↑PSNS output -> ↓HR, ↓BP, coronary vasodilatation

Surgical misadventure

·      Damage to vessel by trochar

·      Difficult to control bleeding

·      Difficult to estimate blood loss