Anesthesia for General Surgery Abdominal Procedures Study Notes

Anesthetic Considerations for Laparotomy

  • Technique: Utilize GETA with a balanced anesthetic and neuromuscular blockade to minimize diaphragmatic movement during abdominal manipulation.

  • Fluid and Access: Significant blood loss is expected; established IV access is critical, especially when arms are tucked. An arterial line may be necessary for large anticipated losses.

  • Physiological Response: Monitor for vagal responses during bowel manipulation.

  • Decompression: Decompress the stomach with an OGT at the start of the case. Use a Foley catheter for extensive procedures.

  • Airway Management: Treat gastric procedures as "full stomach" cases using RSI due to the high risk of aspiration.

Specific Abdominal and Intestinal Procedures

  • Gastric Surgery: Includes gastrectomy (partial Billroth II or total Roux limb). Procedures carry risk for hemodynamic instability if bleeding and large third-space fluid losses.

  • Open Appendectomy: Often presents acutely with dehydration due to emesis and fever; IV hydration is required before induction. RSI is standard for this acute presentation.

  • Small Bowel and Colorectal: Treat as full stomach/RSI if obstruction is present. Emergency colectomy on unprepared bowel involves high risk for peritonitis and requires significant fluid management for third-space losses.

  • Rectal and Anorectal: Brief but highly stimulating procedures. Deep planes of anesthesia or muscle relaxants are required for sphincter relaxation if GA is used.

Laparoscopic Surgery and Pneumoperitoneum

  • Technique: Perform GETA with neuromuscular blockade. CO2 is insufflated via a Veress needle to a pressure of 12−15 mmHg12-15\,\text{mmHg} (maximum allowable is 20 mmHg20\,\text{mmHg}).

  • Physiologic Effects:

    • Mechanical: Increased SVR, CVP, MAP, and HR; decreased stroke volume.

    • Ventilatory: Thoracopulmonary compliance decreases by 30−50%30-50\%\n * FRC: Decreased functional residual capacity, often requiring PEEP to treat atelectasis.

    • Humoral: Release of catecholamines and vasopressin (a significant hemodynamic mediator) increases MAP and afterload.

Complications and Monitoring of Laparoscopy

  • Gas Embolism: Identified by a sudden drop in ETCO2ETCO_2, hypotension, and a "mill wheel" murmur. Management includes discontinuing insufflation, administering 100% O2100\%\,O_2, and placing the patient in the left lateral decubitus position.

  • Referred Pain: Stretching of the diaphragm and CO2 retention irritates the phrenic nerve, causing referred pain in the C4C4 dermatome (shoulder) in 35%−80%35\% - 80\% of patients.

  • Respiratory Risks: CO2 subcutaneous emphysema, pneumothorax, and endobronchial intubation due to cephalad displacement of the diaphragm.

  • Positioning: Brachial plexus or ulnar nerve injuries are risks in Trendelenburg or lithotomy positions. ETT position must be verified after movement.

Robotic-Assisted Surgery and ERAS

  • Robotic Procedures: Involve longer case lengths and extreme positions like steep Trendelenburg, which can cause facial edema. Undocking the robot in emergencies takes several minutes.

  • ERAS (Enhanced Recovery After Surgery): Employs evidence-based interventions to minimize post-operative complications and shorten hospital stays, particularly in colorectal surgery.