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Laparoscopic Surgery 

 

 

Physiologic Effects of Laparoscopy

 

Goal = intraabdominal pressure (IAP)  ≤15 mmHg to minimize physiologic effects

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  • CVS:

    • ​Variable & dynamic

      • generally well tolerated if healthy

      • significant cardiac dysfxn can occur in elderly & comorbid pts (eg. COPD, CHF, pulm HTN, valve dz)

    • ↑MAP, SVR, & CVP

    • ↓CO & SV 

    • ∆s are due to:

      • Pneumoperitoneum/↑ IAP

        • Release of catecholamines & RAS activation: release of vasopressin

        • Vagal stimulation: bradyarrhythmias

        • Dynamic mechanical effects

          • Depend on vol status, insufflation pressure & position

          • Arterial compression: ↑SVR & PVR

        • CVS effects usually resolve rapidly as pneumoperitoneum is maintained

      • Position ∆s

        • Head-up/Reverse Trendelenburg (ex cholecystectomy): venous pooling w/ ↓ venous return

        • Head-down/Trendelenburg (ex pelvic surgery): ↑venous return & cardiac filling pressures

      • Hypercarbia

        • Direct effects: ↓ cardiac contractility, sensitization to arrhythmias, systemic vasodilation

        • Indirect effects: symp stimulation (tachycardia, vasoconstriction, ↑SVR/PVR)

  • Respiratory

    • Mechanical

      • Cephalad displacement of diaphragm & mediastinal structures: ↓FRC & pulm compliance; atelectasis, ↑peak airway P, V/Q mismatch

      • Endobronchial migration of ETT

    • Hypercarbia

      • MV must ↑ to compensate

        • Can lead to ↑intrathoracic P w/ ↑SVR & PVR

  • Regional circulatory changes

    • Splanchnic blood flow: no clinically sig effect

      • ↓ by mechanical & neuroendocrine effects - ↓hepatic blood flow & bowel perfusion

      • ↑ by hypercapnia (direct splanchnic vasodilatation)

    • Renal blood flow: ↓renal perfusion & u/o 

      • renal parenchymal compression, ↓ renal vein flow,  ↑vasopressin

    • Cerebral blood flow: ↑CBF & ICP 

      • ↑IAP, hypercarbia, Trendelenburg

      • May be significant if intracranial mass, sig cerebrovascular dz - important to maintain strict normocapnia

    • Intraocular pressure: ↑

 

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Potential Complications

  • Hemodynamic & pulmonary complications related to physiological changes of pneumoperitoneum

    • Initial insufflation = higher risk time 

  • Occult hemorrhage - may not be visible due to small surgical field

  • Vascular or solid organ injury 

  • Gas embolism 

    • Subclinical embolism very common; sig emboli rare

    • Mechanisms:

      • Direct venous injection of CO2 w/ Veress needle

      • CO2 entrainment via severed/disrupted vein 

  • Subcutaneous emphysema

    • ↑ CO2 absorption ➝ hypercarbia

    • Potential airway compromise if crepitus/swelling in head, neck, or upper chest

    • Risk factors: surgery >200 mins, ≥6 ports, age >65, Nissen fundoplication

  • Capnothorax: suspect of unexplained ↑ airway P, hypoxemia, & hypercapnia

  • Capnomediastinum & capnopericardium  

  • Complications related to positioning

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