Pneumoperitoneum in Laparoscopic Surgery Matt Wagaman CA1

Advantages of Laparoscopic Surgery Reduced postoperative pain Improved post operative mobilization  return to activity quicker Small scar  less chance of hernia/cosmetic Reduced wound infections Reduced hospital stay BUT…….

Expansion of laparoscopic general surgery has shifted patient demographics so that more elderly, debilitated patients w/ significant comorbidities undergo laparoscopic surgery. – Report from 35 Connecticut hospitals, more than one third of patients undergoing laparoscopic cholecystectomy were more than 55 years of age, almost one quarter were more than 65 years of age, and 8% were more than 75 years of age. (Orlando et al.) These patients are more susceptible to perioperative complications due to the hemodynamic and cardio- respiratory changes caused by pneumoperitoneum. Thus, it is important that anesthesiologists and surgeons understand these potential complications so that appropriate measures can be taken to ensure optimal perioperative support.

Pneumoperitoneum Abdominal insufflation w/ CO2, helium, nitrous oxide, or oxygen to ~ 15 mmHg – Normal Intra-abdominal pressure (IAP) < 5 mmHg CO2 most commonly used gas. – Noncombustible = safe to use with electrosurgical devices – Solubility in blood and reactivity w/ soluble buffering systems minimize the risk of gas emboli ( ) Systemic absorption thought to be facilitated by CO2 specific widening of inter-cellular junctions in peritoneum  buffering of CO2 as above  Systemic Acidification

Systemic acidification (pCO2 ~55) and increased intraperitoneal pressure (>15 mmHg) can cause cardiac arrhythmias, constriction of pulmonary vasculature, and alterations in cardiac function

Cardiovascular Effects of ↑ IAP ↑ IAP  ↓ Venous Return  ↓ Preload  ↓CO  ↑ HR, MAP, SVR, and PVR These effects amplified by IAP > 15 mmHg and reverse Trendelenberg positioning. Pneumoperitoneum can produce significant hemodynamic stress. An awareness of potential complications, especially in patients with significant cardiac disease (i.e severe CAD) is essential.

Respiratory Effects of ↑ IAP Increased intra-abdominal pressure displaces the diaphragm cephalad causing: – ↑PIP  Consider pressure mode ventilation – ↑ IP volume  Compression basilar lung segments  ↓ FRC  ↑ alveolar dead space  V/Q mismatch – ↓ Vital Capacity – ↓ FRC – ↑ Intra-thoracic pressure  May worsen w/ Trendelenberg position and may exacerbate GERD Protect airway in patients at risk of aspiration Usually only clinically significant in patients w/ pre-existing pulmonary comorbidities – WATCH OUT if your patient has COPD w/ impaired compensatory mechanisms  High risk of hypoxemia and significant hypercapnia!

Renal Effects of ↑ IAP Studies have shown 35-60% decrease in RBF with ↑ IAP during pneumoperitneum ↓ RBF  ↑ ADH, plasma rennin activity, and serum aldosterone  OLIGURIA Extent of oliguria directly related to ↑ IAP and studies have shown improvement w/ desufflation Anticipate potential complications in patients w/ pre-existing renal impairment especially if high IAP used. May need to ask surgeon use minimal insufflation pressure

Hepatic Effects of ↑ IAP Pneumoperitoneum decreases Hepatic blood flow in manner similar to renal blood flow. Can lead to acute hepatocellular injury w/ transient ↑ LFT w/ normalization within 72h Decrease injury by keeping IAP < 15 mmHg, minimizing traumatic liver retraction, and avoid anesthetics that could worsen liver function.

Intraoperative Management “Proper Prior Planning Prevents Poor Performance” Preoperative planning and vigilant intra-operative control of detrimental effects of CO2 pneumoperitoneum are key to a safe and successful outcome!

Monitors Based on the patient’s comorbidities ensure you have the ability to adequately monitor how CO2 pneumoperitoneum and ↑ IAP are effecting your patient. ASA standard monitors ± – Foley – Arterial line (Useful to monitor ABGs to detect arterial and ETCO2 difference  changes to ventilation.) – CVP (May be helpful in extreme cases where volume status is a concern; otherwise unreliable and usually not worth the risk)

Fluids Status After placing IV  Can counterbalance expected hemodynamic effects of ↑ IAP w/ moderate fluid hydration (500cc-1L NS/LR vs. Hespan) Fluid hydration w/ pneumoperitoneum: – Preserves CO, SV, and RBF while increasing UOP. – Improves hemodynamic function in all patient positions – Avoid aggressive hydration in patients at risk of potential complications of fluid overload (CHF, CRF, ICU patients) Pre-operative hydration can be helpful to minimizing the negative effects of pneumoperitoneum

Positioning Trendelenberg: – Advantage: ↑ Venous return  Less hemodynamic stress – Disadvantages: ↑ ITP  Decrease lung compliance Increased venous pressure and stasis in the head maybe cause falsly decreased SpO2 reading and poor wave form. Debatable risk of ↑ ICP ↑ ICP from steep trendelenberg has been shown to cause choroidal vasodilation  ↑ ICP and ↑ intraocular pressure  blindness. (Awad et al) Reverse Trendelenberg: – Advantage: Improved lung compliance – Disadvantage: ↓ Venous return  HD stress and blood pooling ↑ DVT risk Collaborate with the surgeon to place patient in the position that is best for your patient’s needs

Ventilation Most patients tolerate mild increases in PaCO2 Patient with high metabolic and cellular respiratory rates (septic patients), impaired regional blood flow, large dead space (COPD), or poor CO may have poor homeostatic reserve and be at risk for developing more severe acidosis. (Safran) ↑ Minute Ventilation to prevent respiratory acidosis by ↑ RR – Increasing RR and keeping TV low can minimize already ↑ PIP from ↑ ITP yet still eliminate increased CO2 from peritoneal absorption – Adjust based on patient specific concerns i.e. COPD, volume status, or obesity (risk of intrinsic PEEP) Use PEEP cautiously! – PEEP will improve gas exchange BUT…. – PEEP will also ↑ ITP  ↓ CO – Rarely beneficial at levels > 5 mmHg

Gas Embolism Extremely rare but has been reported during laparoscopy. Suspect if patient has acute cardiovascular collapse or otherwise unexplained dysrrhythmia. Mill-wheel murmur may help make diagnosis of gas embolism – A temporary loud, machinery-like, churning or splashing sound due to blood mixing with air in the right ventricle, best heard over the precordium. If suspected place patient in left lateral decubitus position and support hemodynamics/ventilation.

Abbreviations Abbreviations: IAP: Intra-abdominal pressure PIP: Peak inspiratory pressure IP: Intra-peritoneal RBF: Renal blood flow ITP: Intra-thoracic pressure ICP: Intra-cranial pressure HD: Hemodynamic

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