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Anesthesia for laparoscopic surgery
Authors
Abstract
The description of anesthesia for laparoscopic surgery covers all basic principles.
Operating room set up, position of patient and equipment, instruments used are thoroughly described. Technical key steps are presented in a step by step way: evaluation, preparation/premedication, lung ventilation, monitoring, end of procedure, complications.
Consequently, this operating technique is well standardized for the management of this condition.
Operating room set up, position of patient and equipment, instruments used are thoroughly described. Technical key steps are presented in a step by step way: evaluation, preparation/premedication, lung ventilation, monitoring, end of procedure, complications.
Consequently, this operating technique is well standardized for the management of this condition.
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2001-03
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E-publication
WeBSurg.com, Mar 2001;1(03).
URL: http://www.websurg.com/doi-ot02en237.htm
URL: http://www.websurg.com/doi-ot02en237.htm
Anesthesia for laparoscopic surgery
1. Introduction
• Foreword
This text is to be considered a framework for the compilation of data from the surgical community. The material is based on consensus and a general bibliographic overview is added. Each new contribution must come with references.• Acceptance by anesthesiologists
Laparoscopic surgery has gained rapid acceptance in the anesthesiological community, mainly due to its advantages to patients in the postoperative period. The development of adequate monitoring has made it easier to assess tolerance of physiopathological changes associated with pneumoperitoneum, head-up, or Trendelenburg positions. A better understanding of these changes has allowed the implementation of corrective measures and has helped to determine more accurately when conversion to open surgery becomes mandatory.Good teamwork encourages anesthesiologists to do their best to promote laparoscopic surgery and surgeons to accept conversion in the rare circumstances when a laparoscopic procedure is no longer advisable.
2. Evaluation
• Preoperative evaluation
For all surgery, preoperative evaluation includes:- past medical history, for possible co-existing diseases and contraindications;
- a physical examination;
- accurate and honest information to the patient, mentioning the possibility of conversion to laparotomy.
Excessive advertising messages such as keyhole surgery or woundless surgery should be avoided.
• Contraindications
General contraindications to laparoscopy are as follows:- bullous emphysema: spontaneous pneumothorax;
- peritoneo-jugular derivation: Le Veen shunt;
- coagulation disorders, especially when associated with abdominal collateral circulation;
- acute emergency with shock;
- current or potential intracranial hypertension and related conditions;
- lack of proper surgical equipment or inadequate training for the use of equipment;
- lack of monitoring devices.
Relative contraindications to laparoscopy or situations under evaluation are as follows:
- bullous emphysema: spontaneous pneumothorax;
- pregnant patient;
- laparoscopic procedures of more than 6 hours duration;
- outpatient setting: most laparoscopic surgery is well suited for outpatient surgery. Discussion at present concerns whether laparoscopic cholecystectomies or laparoscopic hysterectomies are advisable for outpatients;
- new indications (eg, pericardiac fenestration).
• Association of risk factors
An association of risk factors must be taken into consideration, for instance the association of sickle cell anemia and chronic obstructive pulmonary disease (COPD).In this type of combination of alterations in lung ventilation and O2 transportation, profound desaturation may occur, requiring prompt conversion to laparotomy.
• Advantages
Evolution of views concerning contraindications to laparoscopic surgery:Contrary to prevailing views a few years ago, it is now well acknowledged that laparoscopic surgery offers the greatest advantages over open surgery to patients in high-risk groups such as:
- patients in intensive care;
- patients with cardiac, respiratory, or renal failure;
- children;
- obese patients;
- older age groups (80 years or older, ASA 3);
- ischemic heart disease patients (ASA 3-4);
These high-risk patients, of course, require proper customized monitoring.
3. Preparation/premedication
• Preparation
Bowel preparation is currently reserved to certain digestive procedures.Emptying the bladder is mandatory, either by asking the patient to urinate before entering the operating room or by means of a Foley catheter during longer procedures. This catheter also allows the surgeon to check for bladder integrity at the end of the operation.
Prevention of thromboembolism is mandatory since laparoscopy is associated with considerable venous stasis during the procedure, despite earlier ambulation. Low molecular weight heparins (LMWH, eg, Enoxaparin) are the standard prophylactic treatment in many institutions.
They are often combined with compression stockings.
• Premedication
Parasympatholytics (eg, atropine/glycopyrrolate) may be useful due to the reflexogenic properties of intraperitoneal maneuvers. Sedative medication is non specific.
H2 antagonist premedication has been advocated given the risks of possible regurgitation. This is mainly the case when the patient has a hiatal hernia.
4. Operating room set-up
• Patient
1. To allow the surgeon better access, one arm is usually secured along the body with the usual positioning precautions. 2. Venous access and monitoring are undertaken on the other arm.
3. Positioning the patient with the legs apart enables sufficient access, even for gynecological procedures.
4. The gynecological position is rarely necessary.
• Equipment
Once popular, shoulder rests are rarely useful at present. If they are used, it is of utmost importance to place them against the bony aspect of the shoulder to avoid brachial plexus compression.A nasogastric tube should be inserted before peritoneal insufflation to avoid puncturing of the stomach, possibly distended by the face mask ventilation preceding intubation.
5. Lung ventilation
Orotracheal intubation and controlled ventilation are needed to enable proper hypercapnia control and to protect the airways.The laryngeal mask airway (LMA) is not appropriate since insufflation pressure often exceeds 20 cm of water and aspiration has been reported during LMA anesthesia for laparoscopy. Properly controlled ventilation depends on an appropriate anesthesia machine offering full control of volume, pressure and gas composition.
6. Monitoring
• Monitoring
Careful monitoring is mandatory since laparoscopy is associated with important cardiovascular and physiological respiratory disturbances, combined with the specific risk of a gas embolism.• Cardiovascular changes
Cardiovascular changes during laparoscopy are as follows:- decrease in venous return to the right ventricle due to the pneumoperitoneum (PNOP). The Trendelenburg position does not sufficiently correct this decrease.
- decrease in cardiac output (CO): the cardiac index drops by 25% to 35% due to the PNOP and the effects of general anesthesia. The decrease in CO can reach 40% 50% in the head-up position. The Trendelenburg position is insufficient to rectify the cardiac output.
- increase in arterial blood pressure despite the fall in CO is due to increased systemic vascular resistance in response to increased intraperitoneal pressure. Humoral factors involved in this response include the catecholamines, prostaglandins and vasopressin. The sympathetic reaction to hypercapnia may also play a role in the observed rise in blood pressure. General anesthesia counteracts this hypertensive response, especially when drugs with significant calcium channel inhibiting power are used (eg, volatile anesthetics, propofol).
- arrhythmia may occur secondarily to vagal stimulation. The classic premature ventricular contractions (PVCs) associated with high CO2 levels and halothane anesthesia should no longer occur.
- despite early ambulation, there is a risk of thromboembolism due to acute venous stasis during the procedure. Therefore, prophylaxis with LMWHs is logical.
• Respiratory changes
Respiratory changes during laparoscopy are as follows:- the diffusion of pneumoperitoneal CO2 leads to a usual increase in PaCO2 and end-tidal CO2 that can be considerable in case of extraperitoneal insufflation. This hypercapnia is generally easy to compensate by increasing the minute ventilation.
- the arterial oxygen saturation (SpO2) is seldom affected. If it drops, the shunt associated with the compression of the basal zones of the lungs is not compensated for and it is mandatory to decrease the pressure level in the pneumoperitoneum. If this is not feasible or successful, conversion is indicated.
• Gas embolism
Gas embolism during laparoscopy is a rare event that may occur at any time. It may follow 2 different patterns: - a massive CO2 embolism is characterized by a sudden drop in end-tidal CO2 (ET CO2);
- exceptionally, a progressive embolization may be detected by an abnormal rise in ET CO2. Continual monitoring ET CO2 is mandatory. Conversely, Doppler gas detection is not useful because it is too sensitive and not specific enough in this context.
The precordial stethoscope is an excellent tool for gas embolism detection but continuous auscultation is time-consuming for an already busy anesthesiologist.
Gas embolism may be severe during laparoscopy because the CO2 in the pneumoperitoneum is polluted by N20 from the anesthesia ventilation system. This makes the gas mixture more dangerous than the pure CO2.
• Monitoring rules
The patient should be constantly monitored.The precordial stethoscope (mill wheel sound) is of value but requires considerable manpower.
PNOP pressure must remain at <20 cm H2O (14 mm Hg).
While placing the patient in Trendelenburg position, an auscultation check is indispensable to make sure that the ventilation remains bilateral and symmetrical since selective right mainstem branch (RMB) intubation may occur in this position.
Capnography and pulse oxymetry are mandatory: precordial Doppler is less useful.
There should always be a nerve stimulator in use and a temperature probe for longer procedures.
Invasive monitoring is indicated according to the medical status of the patient:
- American Society of Anesthesiologists [ASA] class;
- New York Heart Association [NYHA] class.
7. End of procedure
• End of surgery
Bladder integrity can be checked with a blue dye injected in the Foley catheter.Exsufflation should be as complete as possible.
Acid embolism is due to the return of heavily desaturated blood to the central circulation.
Return to the horizontal position must be gentle, keeping in mind that the restoration of hemodynamic stability is delayed (prolonged humoral disturbances).
100% O2 ventilation and full reversal of relaxant are required before the extubation.
• In the recovery room
The patient is closely supervised and re-warmed.Gaseous and metabolic acidosis may be combined at this time.
Uncommon complications such as a vascular injury that went unrecognized during surgery or a CO2 pneumothorax should be identified and treated.
8. Complications
• Intraoperative complications
Laparoscopy involves certain inherent risks. Constant progress is being made in the techniques and indications for preventing these risks. Publication of complications is crucial in order to optimize the statistical definition of the inherent risks.Vascular injuries are the main cause of death. These injuries occur in 3 to 10 out of 10 000 gynecological laparoscopies and in 10 out of 10 000 cholecystectomies.
The major retroperitoneal vessels are involved in half of the cases.
About 10% of vascular injuries are fatal (5 deaths out of 100 000 cases).
The diagnosis is made postoperatively in 1 case out of 3 (complication unrecognized during the procedure).
Hollow viscous perforation may involve the stomach (after gastric dilatation from mask ventilation), the urinary tract (bladder, ureter), the uterus, and the bowel (1.4 out of 10 000 cases). This is often undetectable during the procedure, appearing as postoperative peritonitis.
Newer complications include the following: CO2 pneumothorax (unilateral or bilateral) mainly after gallbladder surgery, vagotomy and Nissen procedures; pneumopericardium; subcutaneous emphysema; cancer dissemination (ports); herniations and strangulation; cholelithoptysis of spilled gallstones.
• Postoperative period
Postoperative morbidity is common and has 2 main aspects: pain and postoperative nausea and vomiting (PONV). Pain is attributed to residual CO2, which may last 72 hours. Several measures have been suggested to handle post-laparoscopic pain:- 6 hours of peritoneal aspiration (poor results);
- topical and/or intraperitoneal local anesthetics;
- pre-emptive analgesia with non-steroidal anti-inflammatory drugs, paracetamol, and opioids.
PONV are frequent after this type of surgery. Proposed treatments include:
- anesthesia without N2O;
- metoclopramide 10 mg: efficacy comparable to placebo in several studies;
- type 3 receptor antagonists of serotonin, dexamethosone (2.5 to 10 mg) and/or droperidol (0.625 to 1.25 mg) are the standard treatments, and the best validated at the present time;
- scopolamine and ephedrine have more side effects and are less effective.
Management of PONV should be considered as important as postoperative pain management.