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Anaesthesia for laparoscopic surgery

Peter Dzendrowski, MBBS, FRCA

Intraoperative problems

Anaesthetic management

Post-operative care

Further reading

Laparoscopic surgery requires the creation of a pneumoperitoneum. CO2 is used for gas insufflation via a Veress needle, at a rate of 1-6 litre/min, to a pressure of 14-20mmHg. Constant CO2 flow of about 200-400mls/min maintains pneumoperitoneum perioperatively, thus creating the "tension pneumoperitoneum".

Intraoperative problems

Most important:

Cardiovascular

Haemodynamic

  • Creation of tension pneumoperitoneum causes initial increase, followed by decrease, in venous return, due to rise in intra-abdominal pressure (IAP).
  • Leads to fall in SV and CO, however this is offset by increase in SVR due to raised IAP.
  • May lead to reflex tachycardia
  • BP generally remains relatively constant

Arryhthmias

  • Gas insufflation – may cause arrhythmias.
  • Include AV dissociation, nodal rhythm, sinus bradycardia and asystole.
  • Response more pronounced with rapid stretching of peritoneum at the beginning of
  • insufflation. Probably vagally mediated reflex initiated by stretching of peritoneum. Incidence
  • increased by hypercarbia and use of halothane

HINT: always have anticholinergic drug readily available

Gas embolus has been reported as cause of cardiac arrest during laparoscopy.

Respiratory

Pneumoperitoneum increases pressure on diaphragm, leading to cephalad displacement of diaphragm

This leads to:

  • reduction in lung volumes, including:
    - Tidal volume
    - Minute volume
    - Functional residual capacity
  • decreased pulmonary compliance, increased airway resistance and increase in pulmonary vascular resisistance, resulting in increased airway pressure for any given tidal volume. Leads to increased haemodynamic changes and risk of barotrauma during IPPV.
  • restriction in diaphragmatic mobility promotes uneven distribution of ventilation to the non-dependent part of the lung. Results in ventilation perfusion mismatch with hypoxaemia and hypercarbia (CO2 absorption form pneumoperitoneum may also cause hypercarbia).
  • ventilatory impairment is more severe if there is associated airway and alveolar collapse, predisposing to post-op chest infections.
  • increased intra-abdominal pressure may predispose to regurgitation and aspiration in those susceptible patients – however much research has suggested that SV via LMA is acceptable in properly assessed patients
  • cephalad movement of diaphragm, combined with Trendelenberg position may cause displacement of ETT tip and endobronchial intubation

Gastrointestinal

  • Pneumoperitoenum leads to increase in IAP, but also increase in barrier pressure as well.
    Barrier pressure = lower oesophageal pressure – intra-gastric pressure.
    Therefore previous risks of aspiration and regurgitation may have been overestimated and are now being re-assessed.
  • Increased incidence of nausea and vomiting associated with laparoscopic surgery, so regular antiemetic prescription is vital
  • Trochar insertion can damage viscera, particularly a stomach distended by hand ventilation. Therefore N-G aspiration may occasionally be necessary prior to trochar insertion.

Renal and metabolic

  • IAP > 20 mmHg adversely affects renal function and urine output.
    RBF and GFR decrease because of increase in renal vascular resistance, reduction in glomerular filtration gradient and decrease in cardiac output
  • massive elevation in IAP produces lactic acidosis, probably by severely lowering cardiac output and by impairing hepatic clearance of blood lactate
  • as with all surgery, there is an associated stress response with elevated cortisol and circulating catecholamines

Complications of gas insufflation

- arrhythmias, as mentioned above.

- subcutaneous emphysema

- pneumomediastinum

- pneumopericardium

- pneumothorax 

- venous gas embolus:

  • potentially fatal
  • gas may enter circulation if Verres needle or trochar directly punctures blood vessel. However, in some cases of gas embolus no evidence of vascular injury is found
  • consequences depend on rate, amount and nature of gas
  • magnitude of physiological disturbances caused by CO2 is 6.5 times less than that of air because of its higher blood solubility
    • slow infusion of gas is absorbed across pulmonary capillary-alveolar membrane without causing any clinical effect. At higher infusion rates, gas bubbles lodge in peripheral pulmonary circulation. Provoke neutrophil clumping, activation of coagulation cascade and platelet aggregation. Release of chemical mediators produces pulmonary vasoconstriction, bronchospasm, pulmonary oedema and occasionally delayed pulmonary haemorrhage
    • gas bubbles attached to fibrin deposits and platelet aggregates also mechanically obstruct the pulmonary vasculature, further increasing pulmonary vascular resistance
  • increase in right heart afterload leads to right ventricular failure
  • large bolus of gas leads to complete mechanical obstruction of right atrium and ventricle
    • paradoxical emboli can occur
    • portal venous gas embolism causes an initial trapping of gas in hepatic portal circulation. This can subsequently lead to delayed manifestations in the post-operative period

Hypercarbia

  • due mainly to absorption of peritoneal CO2 from pnemumoperitoneum, but also to surgical positioning
  • In spontaneously ventilating patients, may promote tachypnoea, in IPPV, may need to increase minute volume

Patient positioning

  • head down, or lithotomy, for lower abdominal procedures.
    Exacerbates pulmonary effects of pneumoperitoneum. However alveolar deadspace is reduced because of the decrease in hydrostatic gradient in the lung and the increase in cardiac output resultant on increased venous return. Venous congestion of head and neck may compromise cerebral perfusion and produce intracerebral and intraocular hypertension
  • head up for upper abdominal surgery.
    Improved pulmonary function occurs at expense of decreased cardiac function

Accidental injuries of intra-abdominal structures

  • laceration of viscera and vessels – massive haemorrhage
  • injuries may not be noticed during surgery and present as GI sepsis after

Laparoscopic Equipment

  • restricts access to patient
  • electrical hazards
  • burns from end of light cable

Additional problems during thoracoscopic procedures

  • complete isolation of one lung mandatory to provide surgical access
  • application of CPAP to isolated lung not practicable as it causes partial expansion of lung
  • pneumothorax best created by opening the taps of the cannulae to atmosphere and allowing lung to collapse under own elastic recoil
  • pressure in pneumothorax must be carefully regulated to prevent excessive mediastinal displacement and cardiovascular collapse
  • suctioning within enclosed thoracic cavity can lead to negative pressure within the hemithorax and mediastinal displacement. Air entry vent should be inserted
  • damage to heart potential complication

Anaesthetic management

Pre-anaesthetic assessment

  • medical contraindications are relative. Successful laparoscopic surgery has been performed in anticoagulated, pregnant and morbidly obese patients
  • assess cardiac and respiratory function carefully. If ASA I or II with no contraindiactions, then may be reasonable to allow spontaneous ventilation via LMA
  • resuscitate if necessary

Anaesthetic technique

General anaesthesia

  • If appropropriate, GA with SV via LMA, otherwise, GA with muscle paralysis, intubation and IPPV
  • adjust ventilatory pattern to respiratory and haemodynamic response of patient
  • large tidal volumes (12-15 ml/kg) prevents progressive micro-atelectasis and hypoxaemia and allows for more effective alveolar ventilation and CO2 elimination. However may cause excessive increase in intrathoracic pressure and thus deleterious cardiovascular effects which will result in an increased alveolar dead-space
  • N2O does not adversely affect surgical conditions during laparoscopic cholecystectomy by causing bowel distension and does not increase the incidence of post-operative nausea and vomiting. However does increase incidence of PONV in by 32% in gynaecological procedures
  • isoflurane volatile of choice because it is less arrhythmogenic and causes less myocardial depression

Epidural anaesthesia

  • - has been used for outpatient gynaecologic laparoscopy to reduce complications and shorten recovery after anaesthesia
  • also has been used for laparoscopic cholecystectomy in a patient with severe cystic fibrosis
    - problems:
    • shoulder tip pain
    • shivering
    • block as high as T2 required to abolish discomfort of surgical stimulation of upper GI structures but this causes myocardial depression and reduced venous return which aggravates the effects of tension pneumoperitoneum. Vagally mediated arrhythmias are also exacerbated

Local anaesthesia

  • can be used for diagnostic laparoscopic procedures
  • supplemented with IV sedation

Monitoring

  • ECG
  • indirect BP
  • pulse oximeter
  • peripheral nerve stimulator
  • end-tidal CO2. In patients undergoing gynaecologic laparoscopy and in most patients undergoing laparoscopic cholecystectomy Paco2 and PE'co2 are closely correlated. However in patients with impaired cardiopulmonary function gradient between the two may become large and unpredictable during laparoscopic surgery and direct estimation of Paco2 may be necessary. PE'co2 monitor also useful for early detection of gas embolus
  • airway pressure monitor

Post-operative

  • recovery usually very rapid
  • minor complications (eg suxamethonium muscle pains, PONV) may produce considerable morbidity and delay discharge
  • PONV particularly troublesome after laparoscopic cholecystectomy and gynaecological procedures
  • pain consists of an early transient vague abdominal and shoulder discomfort. Also experience a deep-seated pain relating to trauma at the surgical site; this can be severe and may require opioids. Pain from trochar puncture wounds usually mild.
  • pulmonary function better preserved following laparoscopic surgery than open surgery in patients with normal lungs. However there is some evidence to suggest that patients with underlying pulmonary dysfunction develop more severe ventilatory impairment that lasts longer after laparoscopic as opposed to open cholecystectomy
  • use of NSAIDS, opioids, PCA or epidural should all be accompanied by an antiemetic

Further reading

Chui PT, Gin T and Oh TE, Anaesthesia for laparoscopic general surgery. Anaesthesia and Intensive Care, 1993; 21:163-171

Verghese C, Brimacombe JR. Anaesth. Analg. 1996; 82: 129-33

 


© Peter Dzendrowski and Charles Gomersall September 1999

 

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©Charles Gomersall, March, 2007 unless otherwise stated. The author, editor and The Chinese University of Hong Kong take no responsibility for any adverse event resulting from the use of this webpage.
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