Management of Anesthesia for Outpatient Laparoscopy - I |
| INTRODUCTION |
In the early 1980’s, laparoscopy in our hospital was largely diagnostic. It was performed by gynecologists on young healthy patients and occasionally by gastroenterologists, except they called it peritonoscopy. The high speed insufflator did not yet exist and the surgeon’s eye rather than a camera was applied to the laparoscope. In 1976, in my training hospital (Los Angeles County General) the ECG monitor was hung from the ceiling, behind the anesthesiologist. Pulse oximetry did not exist and capnography was a curiosity. We had a few mechanical ventilators, but their use was discouraged. Times have changed.
| OVERVIEW |
Today, the advantages of laparoscopy have extended the technique to include a wide range of ages and physical condition. Pediatric appendectomies are common, as are procedures in elderly patients with both chronic and acute medical problems.
Hospital stay and postoperative disability may be significantly reduced after laparoscopy as compared to laparotomy, resulting in important economic benefits. Decreased surgical trauma, especially in upper abdominal surgery results in quicker return of pulmonary function and lowered requirements for postoperative pain medication.
In a now diverse patient population, the anesthetic considerations are as involved as for any open surgical procedure. In addition, the physiological effects of the pneumoperitoneum and exaggerated patient positioning must be well understood. This chapter will include a discussion of preoperative evaluation, anesthetic management and postoperative recovery. In addition, management of complications and relevant physiology will be discussed.
| PREOPERATIVE EVALUATION |
The preoperative evaluation of the laparoscopic patient should encompass the same elements as for an open procedure.
Many patients scheduled for laparoscopic surgery will be admitted a few hours before the scheduled time for surgery. We have found that a telephone call made the night before surgery is an effective means of gathering information as well as establishing a relationship with the patient. Most topics can be covered in a telephone conversation as easily as in the preoperative visit made to an inpatient.
As laparoscopy has moved from the young, healthy patient (i.e. the gynecological laparoscopies of the 1970’s), to a more diverse population, the presence of chronic medical conditions has increased. In patients with increased intracranial pressure, ventricular or peritoneal shunts, pneumoperitoneum and laparoscopy are contraindicated. Patients with congestive heart failure may not be candidates.
In patients with cardiac disease, the advantages of a more benign post-operative course must be weighed against the hemodynamic changes induced by laparoscopy. Cardiac consultation should be obtained where appropriate, as well as echocardiography. In patients with reduced left ventricular ejection fraction, invasive monitoring should be considered. These patients will probably not be candidates for same day discharge.
Laparoscopy is occasionally indicated for pregnant patients. The likelihood of first trimester miscarriage increases from 5.1 percent to 8 percent with surgery. Also the incidence of premature delivery increases from 5.13 percent to 7.47 percent with surgery. These risks should be fully explained to the patient and the discussion documented in the medical record.
| PREMEDICATION |
Pre-op medication should be selected with rapid emergence and discharge in mind.
Midazolam (Versed, Roche) is an ideal anxiolytic agent. If narcotics are used, smaller doses will aid in the prevention of nausea and prolonged emergence. Long acting sedatives (e.g. Phenergan) should be avoided to prevent prolonged emergence and dysphoria. A drying agent (antisialagogue) if often helpful, if not contraindicated. Atropine and scopolamine should be avoided because they cross the blood-brain barrier and can cause postoperative delirium; Glycopyrrolate (Robinul, A.H. Robins) is a better choice. Of course, atropine should be immediately available for the treatment of severe intraoperative bradycardia.
In patients with an increased risk of regurgitation, consider the preoperative administration of antacids, H2 receptor antagonists such as famotidine (Pepcid, Merck) and gastroprokinetic drugs such as metoclopramide (Reglan, A.H. Robins). Of course, every patient should come to surgery NPO, with the exception of routine morning medications taken with sips of water.
Patients who are steroid dependent should receive hydrocortisone as part of the pre-op regimen.
The use of midazolam in pregnant patients should be avoided. Glycopyrrolate does not cross the placenta.
| PATIENT POSITIONING |
Great care should be taken in positioning patients in order to prevent nerve injuries. Adequate padding, especially of arms tucked at the patient’s side, is needed to prevent ulnar nerve injury, and care must be taken in raising the foot of the operating room table at the conclusion of surgery to avoid entrapment of the fingers. If shoulder braces are used, they should be placed facing the coracoid process. Patients placed in the lithotomy position should not have their legs placed in exaggerated attitudes. The peroneal nerve must be adequately protected from injury.
| MONITORING |
ECG, pulse oximeter, capnometer and non-invasive blood pressure device are essential. Frequent evaluation of neuromuscular blockade is also a requirement. In patients with cardiac disease, more invasive monitoring may be necessary. It should be remembered that interpretation of central venous pressure and pulmonary artery pressure may be difficult due to increased intrathoracic pressures.
| MANAGEMENT OF ANESTHESIA |
Induction of anesthesia should be done with an appropriate dose of propofol (Diprivan, Zeneca). Pain on injection can be alleviated by injecting a small dose (25-50 mg.) of lidocaine first. Some practitioners mix the lidocaine with the Diprivan immediately before injection. Diprivan is an ideal induction agent for outpatient laparoscopy because it allows rapid emergence and has a reduced incidence of postoperative nausea compared to barbiturates. Ondansetron (Zofran, Glaxo Wellcome) administered before induction of anesthesia, should be considered in patients with a history of postoperative nausea and vomiting. Whereas a small dose of a short acting narcotic, e.g. fentanyl 50 mg, may smooth the induction, large doses should be avoided, once again to decrease the incidence of prolonged emergence and postoperative nausea.
General anesthesia with endotracheal intubation provides the best airway control and the greatest prophylaxis against gastric aspiration. One study revealed that approximately one third of deaths associated with laparoscopy were related to anesthetic complications during general anesthesia without intubation.
Every patient should be evaluated for the possibility of a difficult intubation prior to induction. Our operating room has a difficult intubation cart stocked with the necessities for managing this problem. Clearly, planning ahead for the difficult intubation is easier than dealing with an emergency. The Bullard laryngoscope has been especially helpful in this regard. The choice of neuromuscular blocking agent should be made based on the anticipated length of the case and the potential for difficult intubation. When a difficult intubation is anticipated, and intubation is to be done after induction, succinylcholine (Anectine, Glaxo Wellcome) should be chosen, unless contraindicated. The use of a defasciculating agent (e.g. curare) remains controversial. The difficult airway algorithm (American Society of Anesthesiologists), should be familiar to every practitioner. If the procedure requires gastric aspiration or if gastric distention occurs due to mask ventilation during induction, a suitable sump tube should be placed after intubation. Unless a nasogastric tube is required postoperatively, gastric intubation should be done orally, to avoid nasal trauma.
If a non-depolarizing agent is to be used for intubation, the length of the case may be the determining factor. For many cases, a single dose of rocuronium (Zemuron, Organon) may be adequate. For a short procedure with a very fast surgeon, mivacurium (Mivacron, Glaxo Wellcome) has the advantage of generally not requiring reversal at the end of the case.
The increased risks of pulmonary aspiration in pregnant patients and those immediately postpartum indicate a rapid sequence induction with cricoid pressure, if the airway is anatomically normal.
Anesthesia may be maintained with a volatile agent of low blood gas coefficient (e.g. isoflurane). The decision to use one of the newer agents with lower blood gas coefficient must be based on a comparison of cost vs. marginally faster time to awakening. The contribution of nitrous oxide to postoperative nausea is still being debated.
Use of opioids should be based on the intraoperative requirements of the patient vs. the possibility of increased postoperative nausea. Some practitioners feel that the administration of ketorolac (Toradol, Roche) toward the end of the case will decrease postoperative opioid requirements.
The degree of muscle relaxation required will depend on the procedure and specific surgeon. Regardless, adequate reversal of neuromuscular blockade is essential before sending the patient to the postanesthesia care unit.
During the case, ventilation should be adjusted to maintain an end tidal CO2 at about 35 mmHg. In patients with a history of spontaneous pneumothorax or bullous emphysema, increasing respiratory rate rather than tidal volume may be preferable.
Changes in patient position should be made gradually with attention to hemodynamic changes. Also, care must be taken in the usually darkened room to ensure that operating room furniture does not impinge on the patient’s body when position changes are made.
The anesthesiologist should be able to see the insufflator, in order to assure that reasonable intraperitoneal pressures are maintained. Close attention to vital signs is essential as high pressures may result in hypotension and bradycardia. Asking the surgeon to lower the pressure will usually reverse the problem more quickly than pharmacologic intervention. Nonetheless, atropine and a vasopressor must be available at all times. Inadequate muscle relaxation and depth of anesthesia should also be considered as a cause of increased intraabdominal pressure.