Anaesthesia for Laparoscopic Surgery

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Introduction to Laparoscopy Initially for gynecology (1970s), now widespread in GI, gynecologic, urologic surgery. Benefits: Reduced trauma, morbidity, mortality, hospital stay. Anesthetic considerations: Pathophysiological changes due to pneumoperitoneum and patient positioning. Duration of surgery, risk of visceral injury, difficulty in blood loss evaluation. Older patients with comorbidities are increasingly undergoing laparoscopic procedures. Ventilatory and Respiratory Changes Intraperitoneal CO$_2$ insufflation causes significant changes. Ventilatory Changes Thoracopulmonary Compliance: Decreases by 30-50% (healthy, obese, ASA III-IV patients). Functional Residual Capacity (FRC): Reduced due to diaphragm elevation. Physiologic Dead Space/Shunt: Not significantly modified with IAP $\le 14$ mmHg and $\pm 20^\circ$ tilt in healthy patients. PaCO$_2$ Increase: Progressively increases, plateaus in 15-30 min. Main mechanism: Absorption of CO$_2$ from peritoneal cavity. Also contributed by V/Q mismatch (patient position, increased airway pressures). Increased VcO$_2$ (20-30%) without significant changes in physiologic dead space in healthy patients. In sick patients (cardiorespiratory problems), ventilatory changes contribute more to PaCO$_2$ increase. PaO$_2$ and intrapulmonary shunt do not change significantly. Hypercapnia: Well tolerated by young, healthy patients. Acceptable levels depend on patient status. Maintain PaCO$_2$ within physiologic range. Correction: 10-25% increase in alveolar ventilation. Monitoring: Capnography and pulse oximetry are reliable. Aa-ETCO$_2$ gradient may increase, so PETCO$_2$ should be used cautiously as an estimate of PaCO$_2$. Respiratory Complications Increased PETCO$_2$? Yes Decreased PETCO$_2$? Yes No Massive CO$_2$ Embolism Subcutaneous Emphysema Yes Desaturation? Yes No Pneumothorax Endobronchial Intubation Yes Increased Paw? Yes No Bronchospasm Changes in Muscle Relaxation CO$_2$ Subcutaneous Emphysema: Accidental extraperitoneal insufflation or intentional extraperitoneal procedures. Increased VcO$_2$, PaCO$_2$, PETCO$_2$. If PETCO$_2$ plateaus and then increases, suspect emphysema. Management: Reduce IAP, temporarily interrupt laparoscopy, increase alveolar ventilation. Resolves spontaneously. Pneumothorax, Pneumomediastinum, Pneumopericardium: Gas movement through embryonic remnants, diaphragm defects, or pleural tears. Capnothorax: Reduces compliance, increases airway pressure, VcO$_2$, PETCO$_2$. Tension Pneumothorax: Decreased PETCO$_2$ (due to decreased cardiac output), hemodynamic instability, desaturation. Management: Stop N$_2$O, adjust ventilator settings for hypoxia, apply PEEP (if no bullae), avoid thoracocentesis unless necessary. Endobronchial Intubation: Cephalad diaphragm displacement moves carina. Decreased SpO$_2$, increased plateau airway pressure. Gas Embolism (most feared): Direct needle/trocar into vessel, or gas insufflation into an abdominal organ. Occurs mainly during pneumoperitoneum induction. Start CO$_2$ insufflation slowly ($\le 1$ L/min). CO$_2$ is highly soluble, rapidly eliminated, five times less lethal than air embolism. Pathophysiology: Bubble size, rate of entry. Rapid insufflation can cause gas lock in vena cava/right atrium, obstructing venous return. Paradoxical embolism through patent foramen ovale possible. Diagnosis: Doppler changes, increased pulmonary artery pressure (early). Tachycardia, hypotension, increased CVP, millwheel murmur, cyanosis (later). PETCO$_2$ decreases (fall in cardiac output, increased dead space), preceded by initial increase (pulmonary CO$_2$ excretion). Treatment: Immediate cessation of insufflation, release pneumoperitoneum, steep head-down and left lateral decubitus (Durant) position, stop N$_2$O, 100% O$_2$. Aspirate gas from CVC if needed. Risk of Aspiration: Increased IAP may maintain pressure gradient across gastro-esophageal junction, potentially reducing risk. Head-down position also helps. Hemodynamic Problems Combined effects of pneumoperitoneum, patient position, anesthesia, and hypercapnia. Hemodynamic Repercussions of Pneumoperitoneum in Healthy Patients IAP > 10 mmHg: Decreased cardiac output (10-30%), increased arterial pressure, increased SVR and PVR. Heart rate unchanged or slightly increased. Cardiac Output (CO) Decrease: Multifactorial (see diagram below). Increased Intra-abdominal Pressure Caval Compression Pooling of blood in the legs Increased Intrathoracic Pressure Decreased Venous Return Increased Vascular Resistance of Intra-abdominal Organs Stimulation of Peritoneal Receptors? Increased Systemic Vascular Resistance Release of Neurohumoral Factor(s) (Vasopressin, Catecholamines) Decreased Cardiac Output Increased Arterial Pressure Inotropism?? Increased SVR: Due to mechanical and neurohumoral factors (catecholamines, renin-angiotensin, vasopressin). Attenuated by Trendelenburg, aggravated by head-up position. Correct with vasodilators (isoflurane, nitroglycerin, nicardipine). Management: Attenuate CO reduction by fluid loading and/or slight head-down position before insufflation. Effect of Pneumoperitoneum on Regional Hemodynamics Lower Limbs: Increased IAP and head-up position lead to venous stasis, predisposing to thromboembolism. Renal Function: Urine output, renal plasma flow, GFR decrease significantly during laparoscopic cholecystectomy. Splanchnic Blood Flow: Controversial; some studies show reduction, others no significant change. Cerebral Blood Flow: Velocity increases due to increased PaCO$_2$. If normocarbia maintained, no harmful intracranial dynamics changes. Intracranial pressure increases independently of PaCO$_2$. Intraocular Pressure: Not affected in women without pre-existing eye disease. Hemodynamic Repercussions in High-Risk Cardiac Patients Cardiac patients (ASA III-IV) experience more marked hemodynamic changes (decreased SvO$_2$, severe cardiac output fall). Patients with low preload, high SVR, and depleted intravascular volume are most vulnerable. Management: Preload augmentation, vasodilating agents (nicardipine, nitroglycerin). Nicardipine may be preferred for its selective arterial vasodilation and benefit in CHF. Congestive heart failure can develop postoperatively. Minor consequences in heart transplant recipients with good ventricular function. Cardiac Arrhythmias During Laparoscopy Causes: Hypercapnia, vagal stimulation (sudden stretch of peritoneum, electrocoagulation of fallopian tubes), level of anesthesia, pre-existing cardiac disease, gas embolism. Vagal reflex: Bradycardia, arrhythmias, even asystole. Treatment: Interrupt insufflation, atropine, deepen anesthesia, recovery of heart rate. Problems Related to Patient Position Head-Down (Trendelenburg): Cardiovascular: Increased CVP, CO in normotensive subjects. In CAD patients, increased myocardial oxygen demand. Cerebral: May affect cerebral circulation, elevate intraocular venous pressure. Respiratory: Facilitates atelectasis, decreases FRC, total lung volume, pulmonary compliance (more marked in obese, elderly, debilitated). Head-Up: Cardiovascular: Decreased CO and MAP due to reduced venous return. Compounded by pneumoperitoneum. Venous stasis in legs, aggravated by lithotomy. Nerve Injury: Overextension of arm, shoulder braces impinging on brachial plexus. Peroneal, meralgia paresthetica, femoral neuropathies. Common peroneal nerve particularly vulnerable in lithotomy. Postoperative Benefits and Consequences Stress Response Laparoscopy reduces acute phase reaction (C-reactive protein, IL-6), metabolic response (hyperglycemia, leukocytosis) compared to laparotomy. Nitrogen balance and immune function better preserved. Reduced intestinal exposure, peritoneal trauma. Reduced postoperative ileus, fasting, IV infusion duration, hospital stay. Endocrine response (cortisol, catecholamines) does not differ significantly from open surgery. Stress response can be reduced by preoperative $\alpha_2$-agonists. Postoperative Pain Significantly reduced pain and analgesic consumption compared to laparotomy. Pain types: Perietal (laparotomy), visceral (laparoscopy), shoulder-tip pain (diaphragmatic irritation). CO$_2$ insufflation causes more discomfort than N$_2$O. Pain relief: Topical anesthetics, intraperitoneal local anesthetic, careful evacuation of residual CO$_2$, thoracic epidural analgesia, bilateral rectus sheath block. Preoperative NSAIDs reduce pain and analgesic consumption. Preoperative multimodal analgesia is effective. Pulmonary Dysfunction Respiratory dysfunction is less severe and recovery quicker after laparoscopy than laparotomy. Greater reductions in expiratory volumes in older, obese, smokers, COPD patients. Pulmonary function still impaired, but improved compared to laparotomy. Thoracic epidural analgesia can improve lung function. Postoperative Nausea and Vomiting (PONV) High incidence (40-75%), major factor for delayed discharge. Intraoperative opioids increase incidence. Propofol anesthesia can markedly reduce PONV. Drainage of gastric contents reduces PONV. Dropeidol, ondansetron, transdermal scopolamine are helpful. Analgesic techniques reducing opioid consumption also help. Alternatives to CO$_2$ Pneumoperitoneum Inert Gases (Helium, Argon): Avoids CO$_2$ absorption, no hypercapnia. Ventilatory consequences of increased IAP still persist. Hemodynamic changes (decreased CO, attenuated arterial pressure increase) similar to CO$_2$. Low blood solubility raises safety concerns for gas embolism. Gasless Laparoscopy: Abdominal wall lift with a retractor, avoids pneumoperitoneum. Avoids hemodynamic and respiratory repercussions of increased IAP and CO$_2$. Renal and splanchnic perfusion not altered. Reduced postoperative pain, nausea, vomiting for cholecystectomy. Reduces port-site metastases for cancer surgery. Appeal for severe cardiac/pulmonary disease. Compromises surgical exposure, increases technical difficulty. Combining with low-pressure CO$_2$ pneumoperitoneum (5 mmHg) may improve conditions. Laparoscopy During Pregnancy and in Children Pregnancy Non-obstetric procedures: Appendectomy, cholecystectomy. Concerns: Miscarriage/preterm labor, gravid uterus damage, fetal acidosis from hypercarbia. Recommendations: Second trimester (ideally before 23rd week). Tocolytics debated prophylactically. Open laparoscopy for abdominal access. Fetal monitoring (transvaginal US). Adjust mechanical ventilation for physiologic maternal alkalosis (maintain normocarbia). Children Hemodynamic changes similar to adults. CO$_2$ absorption may be more intense/faster due to larger peritoneal surface area/body weight ratio. Marked acidemia, hypercapnia, decreased oxygenation in young swine. Good cardiorespiratory tolerance if hypovolemia prevented. Complications of Laparoscopy Absolute Contraindications: Increased intracranial pressure (tumor, hydrocephalus, head trauma), hypovolemia, ventriculoperitoneal shunt (unless clamped), peritoneojugular shunt (unless clamped). Incidence: Gynecologic laparoscopy: Mortality 0.001-0.0001%, serious complications 0.2-1%. Vascular/intestinal injuries 30-50%. Laparoscopic cholecystectomy: Mortality 0.01-0.1%. Conversion to laparotomy ~5%. Bowel perforation ~0.2%, bile duct injury 0.2-0.4%, hemorrhage 0.2-0.9%. Unrecognized Injuries: Gastrointestinal tract injury and subhepatic abscess formation can lead to lethal septic complications. Anesthesiologist must be aware of complications and timing, ready to respond. Anesthesia for Laparoscopy Preoperative Evaluation and Premedication Cardiac Patients: Evaluate cardiac function, especially if compromised ventricular function. Preload augmentation, vasodilators. Gasless laparoscopy may be an alternative. Renal Patients: Optimize hemodynamics, avoid nephrotoxic drugs. Respiratory Patients: Laparoscopy preferable to laparotomy due to reduced postoperative dysfunction. DVT Prophylaxis: Initiate before surgery. Premedication: Adapt to duration, need for quick recovery. NSAIDs, $\alpha_2$-agonists (clonidine, dexmedetomidine) for stress reduction and hemodynamic stability. Patient Positioning and Monitoring Positioning: Pad nerves, shoulder braces on coracoid process, limit tilt to 15-20 degrees. Slow, progressive tilting. Check ETT position after changes. Pneumoperitoneum: Smooth, progressive induction and release. Aspirate gastric gas before trocar placement. Empty bladder before pelvic laparoscopy. Monitoring: Continuous BP, HR, ECG, capnometry, pulse oximetry. Invasive Monitoring: May be needed for cardiac patients (intra-arterial line, PAC, TEE, ST segment analysis). Increased intrathoracic pressure complicates CVP/PAP interpretation. Arterial Blood Gas: Radial artery cannulation for direct PaCO$_2$ measurement in patients with cardiac/pulmonary disease. Anesthetic Techniques General Anesthesia: Recommended for inpatients and long procedures. Endotracheal intubation with controlled ventilation. Adjust ventilation to maintain PETCO$_2$ at $\approx 35$ mmHg (15-25% increase in minute ventilation). Increase respiratory rate rather than tidal volume for COPD, pneumothorax history. Avoid cardiac depressants in compromised patients; prefer vasodilators (isoflurane). Vasodilating agents (nicardipine) reduce hemodynamic repercussions. N$_2$O: Controversy regarding oocyte function, PONV. May improve surgical conditions for intestinal/colonic surgery. Propofol results in fewer postoperative side effects. Atropine available for vagal reflexes. Laryngeal Mask Airway (LMA): Alternative to ETT for healthy, non-obese patients, for short procedures with low IAP and minimal tilt. Avoids tracheal irritation. Local and Regional Anesthesia: Advantages: Quicker recovery, decreased PONV, early complication diagnosis, fewer hemodynamic changes. Avoids general anesthesia sequelae. Requires precise, gentle surgical technique, co-operative patient, supportive OR staff, skilled surgeon. Supplement with IV sedation. Can lead to hypoventilation and desaturation. IAP should be as low as possible ($\le 20$ mmHg). Not suitable for procedures with multiple puncture sites, considerable organ manipulation, steep tilt, or voluminous pneumoperitoneum. Epidural and spinal techniques: Reduce opioid needs, provide better muscle relaxation. Can be used for short procedures like sterilization. Shoulder-tip pain and abdominal distention may not be fully relieved. Adequate analgesia with opiates/clonidine. Hemodynamic effects under epidural: Sympathetic block might facilitate vagal reflexes, but vasodilation and avoiding positive pressure ventilation might reduce cardiovascular changes. Gasless laparoscopy with regional anesthesia avoids most CO$_2$-pneumoperitoneum side effects. Recovery and Postoperative Monitoring Continue hemodynamic monitoring in PACU. Increased SVR can outlast pneumoperitoneum release, leading to precarious hemodynamics in cardiac patients. PaO$_2$ may decrease, increased O$_2$ demand post-laparoscopy. Administer O$_2$ even to healthy patients. Prevention and treatment of PONV and pain are crucial, especially for outpatients.