• Cosmetic surgeries: breast reduction or augmentation, rhinoplasty, liposuction, blepharoplasties
• Orthopedic surgeries such as arthroscopies, carpal tunnel release
• Endoscopic procedures such as colonoscopies
• Minor urological procedures
• Mini-laparoscopic procedures
• Dental procedures
• Ophthalmic procedures: cataracts, strabismus repair
• ENT procedures: tonsillectomy, myringotomy, septoplasty
Advantages and Risks
As mentioned above, ambulatory anesthesia and office-based anesthesia have gained popularity in the recent years because of their low cost, comfort, and convenience to patients. Other advantages include ease of scheduling, maintenance of patient privacy, decreased risk of nosocomial infections, and relatively more personal attention to the patient.
However this subspecialty has also developed its own risk profile. Possible compromise of patient safety in the interest of efficiency is possible. Office-based procedures have an overall complication rate of 0.24 %, and factors that contribute to this problem include limited availability of anesthesia personnel, inadequate availability of anesthesia and resuscitation equipment, and lack of backup personnel and expert consultation. Although the mortality rate of office-based anesthesia is lower (1:400,000) as compared to in-hospital anesthetics (1:250,000), the fact partly contributing to this statistic is that office-based anesthesia usually involves young, healthy patients with no or few comorbidities.
To ensure patient safety, certain prerequisites for the facility where these surgeries are being done have been established. These include regular checkup and maintenance of ventilators and availability of age-appropriate resuscitation equipment, difficult airway and malignant hyperthermia carts, drugs for resuscitation in the event of a cardiac arrest or an emergency, and a defibrillator with a battery backup. To manage these problems, regulations are in place for office-based anesthesia (ASA-SAMBA regulations), as well as the existence of a number of accreditation organizations for ambulatory anesthesia facilities (Accreditation Association for Ambulatory Health Care or AAAHC and American Society for Accreditation of Ambulatory Surgical Facilities or AAASF).
Patient Selection
Patient selection is the key to procedures being safely performed in the ambulatory care center. Most of the patient mix is of ASA I and II patients. Surgery for patients who are > ASA III classification may not be performed in an ambulatory care setting, unless the surgery is minor. These ASA III patients usually have a history of congestive cardiac failure, unstable angina, severe pulmonary disease (COPD, asthma), renal failure, or uncontrolled hypertension or diabetes mellitus.
One should be mindful of the risks factors that increase the complication rate for surgeries performed in the ambulatory care center. These risks factors include extremes of age, morbid obesity, history of smoking, presence of comorbidities, site and duration of the surgery, controllability of postoperative pain, excessive fluid losses, need for general endotracheal anesthesia, distance of the ambulatory center from an emergency service center, and escort availability for the patient.
One of the most important patient-related factors for consideration in ambulatory anesthesia service is the availability of a responsible person who can take the patient home and care for the patient at home. In the pediatric age group, prematurity with post-gestational age <60 weeks is a contraindication for same-day surgery (increased incidence of apnea). Morbidly obese patients with a BMI of >35 kg/m2 may only have procedures done with mild sedation. Patients with pulmonary disease or suspected sleep apnea should have satisfactory oxygen saturation on room air.
Preoperative Evaluation for Ambulatory Procedures
A thorough preoperative evaluation (Table 30.2) along with an informed written consent is a must. Patients are contacted by the surgery center at home preoperatively by telephone or the patient sends in a filled questionnaire. This is done to identify any risk factors and to ensure that the patient is medically optimized before the surgery. Appropriate laboratory results should also be available on the day of the surgery.
Table 30.2
Preoperative evaluation for ambulatory procedures
1. Abnormalities of any organ system, optimization of any medical illness |
2. Current medications |
3. Airway assessment, associated obesity, obstructive sleep apnea |
4. History of previous anesthetics and any adverse events in the patient or family member |
5. Alcohol and substance abuse, current or in the past |
6. Last oral intake, follow appropriate NPO guidelines |
7. Presence of a responsible person to take the patient home and care for him/her at home |
8. Patient education regarding risks, anesthetic plan, and postoperative course |
Anesthesia Techniques in the Ambulatory Care Setting
Monitored Anesthesia Care With or Without Local Anesthesia
Varying levels of sedation with local anesthesia (breast biopsy, inguinal hernia repair, hemorrhoidectomy) or without local anesthesia (colonoscopies, endoscopies) can be used. While performing MAC, one should be aware that the dose of sedatives required to achieve a particular depth of anesthesia is different for each patient and that there is no objective measurement of anesthesia depth. While a light plane of anesthesia may not provide adequate comfort to the patient and decrease cooperation from the patient, a deep plane of anesthesia may render a patient uncooperative. Respiratory depression from oversedation accounts for many complications (hypoxia and brain injury). Backup airway management equipment should be available at all times.
MAC is usually performed by using anxiolytic and sedative drugs (midazolam, fentanyl, propofol), injection of local anesthetics (usually by the surgeon), and providing supplemental oxygen. A deeper plane of anesthesia may be required (bolus of propofol) when the surgeon injects the local anesthetic. Goals of MAC are minimal/adequate depression of consciousness (allowing rapid recovery) and providing anxiolysis, sedation, and analgesia.
Regional Anesthesia
Peripheral nerve blocks, intravenous regional anesthesia (IVRA), or spinal anesthesia may be used for ambulatory surgeries. Peripheral nerve blocks are extremely popular and are performed preoperatively using mild sedation. These blocks are nowadays commonly performed with ultrasound guidance, which has decreased the complication rate. Commonly used local anesthetics for nerve blocks include bupivacaine, ropivacaine, and lidocaine. IVRA is usually performed using 0.5 % preservative-free lidocaine. For spinal anesthesia, lidocaine is avoided due to the increased incidence of transient neurological symptoms. The benefits of regional anesthesia techniques include lower cost, excellent surgical conditions, excellent postoperative analgesia, and low incidence of PONV.
Nerve block catheters can be very effective for postoperative pain relief. Local anesthetic infusion via popliteal, interscalene, or femoral catheters can provide pain relief for about 4 days. Patients can be sent home on a local anesthetic infusion if the patients are appropriately interested and are educated about the pump function and signs of local anesthetic toxicity and have a responsible adult at home to take care of them. Postoperatively, patients receiving upper extremity nerve blocks should have the blocked extremity placed in a sling, while patients receiving lower extremity nerve blocks should receive coaching on using crutches for walking. Additionally, all ambulatory centers should be equipped with intravenous lipid emulsion to counteract the effects of local anesthetic toxicity.
General Anesthesia
For some procedures, such as laparoscopic surgery, general anesthesia is performed. Use of drugs of short duration of action and prophylaxis against PONV are most important.
Preoperative Fasting
Light meals up to 6 h and clear fluids up to 2 h preoperatively are allowed. Carbohydrate-rich clear fluids decrease thirst and hunger sensations and anxiety. Breast milk for 4 h and infant formula for 6 h are allowed preoperatively before surgery.
Premedication
Drugs commonly used for premedication include:
1.
Benzodiazepines: Midazolam is commonly used for anxiolysis and sedation. In adults, midazolam 2–4 mg intravenously may be used preoperatively, or oral diazepam 2–5 mg the night before or on the day of surgery helps to control anxiety. For pediatric patients, oral midazolam in doses of 0.25–0.5 mg/kg (maximum 20 mg) makes the child cooperative and decreases parent separation and stranger anxiety. In appropriate doses these drugs cause minimal cardiorespiratory depression; however, it is recommended that supplemental oxygen be administered with pulse oximetry monitoring when using these drugs.
2.
Beta-blockers: These drugs (metoprolol, atenolol) reduce the sympathetic and catabolic response to surgery. They have also been found to decrease the postoperative requirement of analgesics. Beta-blockers should be continued on the day of surgery.
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