Chui, PT, Gin, T and Oh, TE
Cunningham et al - Anaesth Analg (1993); 76: 1120
APPLICATION OF LAPAROSCOPIC TECHNIQUES:
- general surgery - cholecystectomy (technique of choice),
- pelvic LN dissection,
- thoracic surgery.
Advantages - smaller surgical wounds,
- less postop pain,
- shorter hospital stay and convalescence.
Operative mortality ~ 4-8/100,000.
Patients often older than gynae. population +/- intercurrent changes.
1. SURGICAL REQUIREMENTS
Cannulae and trocars through the ant. abdominal wall.
Endovideo camera and monitors.
Complex two-handed dissection and manipulation while viewing the TV monitor.
Patient positioned to enhance gravitational displacement of organs away from surgical site.
Insufflation with CO2 -> pneumoperitoneum improves field of view.
Flows of 4-6 l.min-1 required at times to maintain IAP ~ 15 mmHg.
Air, O2 and N2O have also been used.
Disadvantages of CO2 include peritoneal irritation and hypercarbia.
N2O similar solubility characteristics but supports combustion - H2, methane may be present in the peritoneal cavity -> explosion risk with diathermy.
2. INTRAOPERATIVE PROBLEMS
(a) EFFECTS OF TENSION PNEUMOPERITONEUM
Elevation of IAP -> deleterious effects on CVS, renal, respiratory and metabolic function.
(i) Cephalad displacement of diaphragm:
- decrease in lung volumes, including FRC with CC encroached upon -> shunt;
- reduced compliance;
- increased RAW -> increased peak PAW for any VT -> increased haemodynamic disturbance and risk of barotrauma;
- increased V/Q mismatch -> hypoxaemia;
- displacement of ETT tip with endobronchial intubation.
Respiratory effects all worsened by intercurrent lung disease.
(ii) Increases risk of gastric regurgitation and aspiration.
(iii) Haemodynamic changes:
IAP <= 10 mmHg -> enhances VR and CO (assuming normovolaemia).
IAP >= 20 mmHg -> IVC compression and decreased VR and CO.
increased SVR -> further impairment of LV function and CO.
Decrease in CO seen at ~ 20-30 mmHg IAP in humans.
Lap. chole. reduced CO seen at ~ 15 mmHg due in part to reverse Trendelenberg position.
High Pip during ventilation (+/- PEEP) further reduces CO.
IAP >= 20 mmHg -> decreased RBF and GFR -> oliguria.
Massive elevation of IAP -> lactic acidosis.
(b) GAS INSUFFLATION
(i) Arrhythmias - AV dissociation, junctional rhythm, sinus bradycardia, asystole.
Probably vagal response to peritoneal stretching.
(increased incidence with halothane and hypercarbia).
(ii) Subcutaneous emphysema, pneumomediastinum and pneumothorax.
(iii) Venous gas embolism - via direct IV gas injection or via open vessels.
Consequences depend on amount, rate and nature of the gas introduced.
CO2 - 6.5 times less physiologically damaging than air (increased sol.).
3-8 ml.kg-1 -> "air lock" with total RV outflow obstruction -> increased RV afterload, arrhythmias, coronary ischaemia, elevated CVP and hypotension..
Slow infusion of air (<= 0.3 ml.kg-1) gradually absorbed with minimal effects.
WBC activation by air in pulmonary circulation -> mediator release and bronchospasm, pulmonary oedema and occasionally delayed pulmonary haemorrhage.
(c) HYPERCARBIA AND SYSTEMIC CO2 ABSORPTION
Solubility of gas, duration of surgery and IAP influence degree of systemic CO2 absorption.
Requires aggressive hyperventilation in many circumstances.
Direct action on CVS and indirect via activation of the sympathoadrenal axis.
(d) PATIENT POSITIONING
Lower abdominal cases -> Trendelenberg:
-aggravates effects of high IAP -> atelectasis and worsening of gas exchange;
- reducedVD plus reducedCO (and \ shunt fraction) partially offset these deleterious effects.
Upper abdo cases -> reverse Trendelenberg:
- improvement of pulmonary function at the expense of CVS impairment.
- obese patients require more extreme positioning & more prone to hypoxaemia.
(e) ACCIDENTAL INJURY OF ABDOMINAL VISCERA
Trocars -> liver, spleen, stomach, aorta, IVC, intestine etc.
(f) MISCELLANEOUS PROBLEMS
Equipment problems common - insufflator, video, irrigation systems etc.
View of patient often compromised by presence of equipment.
(g) ADDITIONAL PROBLEMS ASSOCIATED WITH
One lung isolation required, with all the problems associated with that technique.
Suction in the thorax -> re-expansion of the lung and mediastinal displacement, \ air entry vent should be provided.
3. ANAESTHETIC MANAGEMENT
(a) Preanaesthetic assessment
Contraindications to laparoscopic surgery are relative.
CVS and pulmonary disease requires careful assessment and optimisation.
Conversion to laparotomy always exists as a possibility, and must be considered in any assessment.
Adequate resuscitation in emergency setting - eg appendicectomy.
Premedication - often not necessary unless very anxious.
Opioids can be used intraoperatively.
Atropine likewise to decrease the incidence and severity of bradyarrhythmias.
(b) Anaesthetic techniques
GA, ETT, paralysis and IPPV preferred.
(i) decreases max. increasedIAP and permits IPPV & hyperventilation.
(ii) surgical exposure improved whilst minimising effects of pneumoperitoneum.
(i) Induction - avoid gastric distension -> reduces risk of trocar injury;
- rapid sequence in emergency;
- ETT for airway protection and for IPPV;
- NG tube for gastric emptying during lap chole.
(ii) Ventilation - Vmin increased from baseline of 40 ml.kg.min-1 to 70 ml.kg.min-1.
- 12-15 ml.kg-1 VT;
- PEEP decreases CO significantly in the presence of increased IAP;
- N2O -> increases postop vomiting by 32% in gynae. laparoscopy.
- humidification in longer cases recommended.
Attention to nerve compression, eye protection.
LA and IV sedation used for day-stay lap, as has ED anaesthesia.
N2O recommended as the gas of choice for insufflation.
XS sedation avoided to ensure airway protection.
Epidural anaesthesia - problems:
- high block required to prevent discomfort in upper GIT cases - (potentiates CVS impairment and bradyarrhythmias),
- shivering and shoulder-tip irritation still problematical;
- excess IV sedation can impair airway reflexes.
ECG, NIBP, PAW, ETCO2, SpO2, PNS and temperature should be standard.
IDC decreases bladder distension and minimises risk of damage.
Severe CVS/RSP change may merit an arterial line.
CAD -> PA pressure monitoring.
PETCO2 - mandatory monitoring.
- adjustment of VA;
- VGE diagnosis.
Gradient P(a-ET)CO2 - normally 2-9 mmHg, affected by factors altering VD(alv).
- essentially unchanged in gynae. laparoscopy and lap. chole., but often grossly increased in CAL and CVS change at laparoscopy \ ABG may be required to determine actual PaCO2.
Airway pressure monitoring - mandatory,
- early detection of excess IAP.
Nerve stimulator - minimises gas pressure required by ensuring adequate levels of muscle paralysis.
4. POSTOPERATIVE COURSE
Recovery is rapid.
Many patients in some institutions discharged following day even after lap. chole.
Minor complications - sore throat, muscle pain 2deg. to sux., dizziness, N and V.
N & V problematical after lap. chole. - delay discharge in 7% patients.
Antiemetics \ used routinely.
Shoulder tip pain generally diffuse abdo. pain and minor local wound pain common.
Local surgical trauma can produce a severe deep-seated pain requiring narcotics, although NSAIDs often sufficient.
Infiltration of puncture sites with bupivacaine useful.
Postop lung function
Better preserved cf open surgery.
FVC - decreases 27% versus 48% in lap. vs open cholecystectomy.
Return to preop levels by 24 hours versus 72 hours after open surgery.
Persistent pulm. dysfunction when present is not improved by continuous ED analgesia.
Major source of morbidity in conventional cholecystectomy is abdominal incision.
Significant impairment of ventilation and pulmonary mechanics, due 1deg.ly to pain and disruption of diaphragmatic movement:
- FVC - 40-50% reduction, recovering over 5-7 days.
- FRC - 70-80% reduction from preop values,
- coughing and mucocilliary clearance reduced,
- gradual restoration of lung function beginning after 2-3 days.
Respiratory changes, open vs laparoscopic:
% PREOPERATIVE VALUES OPEN LAPAROSCOPIC FVC 52 73 FEV1 53 72 FEF 53 81
POTENTIAL ADVANTAGES WITH LAPAROSCOPIC CHOLECYSTECTOMY
Minimises abdominal incision,
Preserves diaphragmatic function,
Reduces adverse effects,
Better preservation of pulmonary function,
Less postop ileus,
Economic benefits - shorter hospital stay,
- less time off work.
COMPLICATIONS AND CONTRAINDICATIONS
Same as for open procedure.
Gradually becoming more liberal:
- acute cholecystitis,
- large stones or stones in CBD,
Procedure of choice in patients with high operative risks associated with CVS and respiratory disease.
Relative (and controversial) contraindications
- acute inflammation,
- previous abdominal surgery,
- morbid obesity,
- severe cardiopulmonary disease.
Severe RSP change -> preop ABGs, and PFTs to assess
suitability, bearing in mind that this procedure far better preserves
postop lung function.
Not suitable for day of surgery admission.
COMPLICATIONS AND PHYSIOLOGICAL CHANGES
(i) Trocar insertion
Bleeding from abdominal wall, major vessels,
Hepatic and splenic tears,
Avulsion of adhesions
Herniation at trocar insertion site.
(ii) Trendelenburg position
Initially at 15-20deg. T'burg to displace bowel from pelvis.
Once trocar inserted and insufflation commenced, reverse T'burg.
Effects of head-down position
(a) CVS increasedvenous return -> increasedCO.
Magnitude of change depends on volume status, associated cardiac disease, age, anaesthetic drugs administered, ventilation techniques.
CVP, PCWP do not rise in healthy CVS, but DO rise in CAD during head-down position.
(b) Respiratory - reduction of FVC, FRC due to displacement of abdominal contents.
More marked in elderly and respiratory disease.
Worsened by surgical packs.
NB potential for endobronchial intubation increased by Trendelenburg position as diaphragm pushes abdominal contents and bronchial tree upward.
Most common complications related to this phase:
- sub-cutaneous emphysema,
- respiratory acidosis,
- CO2 embolism,
- CVS collapse,
- cardiac arrhythmias.
Intraperitoneal insufflation via Veress needle to 15-25 cmH2O CO2 pressure, with patient in 15-20deg. T'burg.
(a) CVS - minor haemodynamic changes when IA pressure <= 25 cmH2O.
Modern insufflators maintain 12-15 cmH2O pressure.
Extent of CVS compromise depends upon:
- volume CO2 absorbed,
- CVS change,
- IV volume,
- anaesthetic agents employed,
- surgical conditions.
CVS effects vary with absolute IA pressure - <= 25 cmH2O -> translocation of blood volume to central compartment and augmentation of CO.
IA pressure >= 40 cmH2O peripheral pooling, fall in VR and reduction in CO.
IAP of 15 cmH2O, and 30deg. head-down tilt reduce CI to similar extent, accompanied by increases in SVR.
(b) RESPIRATORY FUNCTION
In the absence of significant CVS/RSP change, increased PaCO2, reducedpHa of no significance (statistically).
Intercurrent cardio-respiratory diseases -> significant increases in PaCO2, and resp. acidosis.
Effects vary with IPPV or spontaneous ventilation.
reduced FRC -> shunting.
CAUSES OF HYPOXAEMIA IN LAP CHOLE
1. Pre-existing disease - RSP/CVS, morbid obesity,
2. Hypoventilation - position,
- ETT obstruction,
- inadequate ventilation - SV vs controlled,
3. Intra-pulmonary shunting - reduced FRC,
- endobronchial intubation,
- bowel distension,
- pulmonary aspiration syndrome,
4. Reduced CO - haemorrhage,
- IVC compression,
- arrhythmia, ischaemia,
- venous CO2 embolism,
5. Technical/equipment - circuit disconnect, delivery of hypoxic mixture.
(c) EXOGENOUS CO2
Diffuses across peritoneal surfaces, and is carried via systemic and portal circulations eventually to RA.
Hypercarbia - arrhythmias potentially with volatile agents.
- hypertension, tachycardia,
- increased bleeding potentially,
- alveolar hypoxia.
Acute hypotension, hypoxaemia and CVS collapse reported with lap chole:
- hypercarbia -> arrhythmias,
- reduced VR due to compression of IVC (2deg. to high IAP) -> release pneumoperitoneum should fix,
- vagal hypertonus from peritoneal irritation,
- venous gas embolism.
(d) Reverse Trendelenburg
Change from head down to head up positions.
Accompanied by respiratory advantages and CVS disadvantages.
GA with IPPV recommended optimal technique.
Monitor ETCO2 mandatory. Increased risk of gastric regurgitation/aspiration 2deg. to high IAP \ cuffed ETT required.
IDC -> reduces risk of bladder perforation.
NG tube similarly reduces risk of gastric perforation.
Narcotics in premed risk sphincter spasm and should probably be avoided - can be antagonised using naloxone, nalbuphine and glucagon.
42% incidence of PONV, reduced significantly using droperidol.
Due in large part to N2O use.
No conclusive evidence contraindicating N2O.