a Boston dentist who demonstrated the use of ether during surgery in the famous amphitheater at the Massachusetts General Hospital in Boston. The scripture below the monument honoring William T.G. Morton fittingly reads, “BEFORE WHOM in all time Surgery was Agony…” This remarkable use of inhalational anesthesia propelled a rapid curiosity about “painless surgery”. Three months following William T.G. Morton’s demonstration, recognition of this technique moved north to Canada, and Canadian physicians embraced this new approach for surgical procedures. 4 In the second half of the 19th century, anesthesia was still very much a craft as practitioners worked tirelessly to understand the basic laws of inhalational anesthesia. The specialty of anesthesia emerged from these seminal procedures, and over the past two centuries, there has been a dramatic increase in both its depth and knowledge. In concert with the appreciation of anesthetic principles, there has been an equal explosion and growth in the development of surgical procedures and pain management.
Fig. 2.1 Establishing general anesthesia. LMAD = Laryngeal mask airway device.
Today, modern anesthesia has developed far beyond its rudimentary roots of ether inhalation. Contemporary anesthesia now provides analgesia and/or amnesia to facilitate a multitude of surgical procedures. Three of the most common modalities in the field of anesthesia include general anesthesia, regional anesthesia, and monitored anesthetic care. General anesthesia (GA) can be induced and maintained via a number of different techniques, including the intravenous administration of drugs as well as the administration of an inhaled mixture of anesthetic vapors. Throughout a general anesthetic, the anesthesiologist attempts to achieve both analgesia and amnesia, with or without muscle relaxation, while maintaining the patient’s normal physiological functions.
Fig. 2.2 The Anesthetic - Surgical Balance.
Anesthetic Modalities:
The delivery of regional anesthesia (RA) refers to the application of a local anesthetic agent to the nerves supplying the anatomical area of surgical interest. Broadly speaking, regional anesthesia is divided into central (neuraxial) and peripheral (nerve block) techniques. These techniques involve the application of a local anesthetic to a specified region to prevent the transmission of pain signals. Finally, monitored anesthetic care refers to anesthetic monitoring with or without the administration of intravenous sedation. Procedures under monitored anesthetic care are commonly performed with intravenous sedation and local anesthesia.
Anesthetic Modalities Include:
1 Local anesthesia + monitored anesthetic care
2 Sedation + monitored anesthetic care
3 General anesthesia (GA) Combined intravenous and inhalational anesthesia (e.g., laparotomy
4 Inhalational anesthesia (e.g., myringotomy)
5 Intravenous anesthesia - total intravenous anesthesia (TIVA) (e.g., neurosurgery, malignant hyperthermia)
6 Regional anesthesia (RA)Brachial plexus block (e.g., interscalene, infraclavicular, axillary blocks)Femoral nerve blockPopliteal nerve blockTransversus abdominis plane block (TAP) blockLocal Blocks: Ankle block, Bier blockMajor Regional anesthesia:Neuraxial anesthesia (spinal, epidural, and combined spinal/epidural anesthesia)Spinal anesthesia: (e.g., total hip arthroplasty, Cesarean delivery)Epidural anesthesia: (e.g., epidural analgesia for labour and delivery)Combined spinal/epidural anesthesia: (e.g., femoral popliteal bypass surgery)
7 Combined RA + sedation
8 Combined GA + RA
The challenge in anesthesia is to choose the most appropriate modality for a patient undergoing a surgical intervention while maintaining an equilibrium between the stress of the surgical procedure and the cardiorespiratory depressant effects of the anesthetic. Thus, modern anesthesia uses a combination of medications in an attempt to minimize the adverse effects and maximize potential benefits of each drug. These medications may include opioids to blunt the pain response to surgery, propofol to induce an anesthetic state, and volatile anesthetic agents to maintain anesthesia. Other common anesthetic medications include benzodiazepines, vasoactive medications, antiemetics, and neuromuscular blocking agents.
In order to formulate an anesthetic plan, the anesthesiologist must consider both the patient’s medical condition and the proposed surgical procedure. Patient factors include patient preferences, previous anesthetic experiences, presenting illness, medical history, as well as the patient’s medications and allergies. During a physical examination, particular attention is paid to the patient’s airway and cardiac and respiratory systems. Each surgical procedure has its own set of anesthetic considerations that need to be balanced with the patient’s physiologic status. Procedures may be performed with local anesthesia alone, monitored anesthetic care, regional anesthesia, general anesthesia, or a combination of these choices (e.g., combined epidural and general anesthesia). It is only after considering the patient’s preferences, medical condition and the surgical procedure that a reasonable decision can be made regarding the choice of anesthetic modality best suited to the patient’s operative procedure.
Fig. 2.3 Patient flow to and from a hospital operating room.
The Scope of Anesthetic Practice:
The scope of anesthesia practice has expanded beyond our primary function in the operating room into a broad spectrum of roles both inside and outside the operating room. The uniqueness of the specialty of anesthesia is the fact that anesthesiologists provide care for all surgical specialties and at all ages of a patient’s life twenty-four hours a day.
The scope of anesthesia practice today may include work in the following areas:
Pre-admission unit
Operating room (OR)
Obstetrical suites
Post anesthetic care unit (PACU)
Intensive care units (ICU)
Surgical step down units
Acute pain service
Procedural sedation (endoscopy units,interventional radiology, surgical outpatient clinics)
Chronic pain clinic
Surgical/anesthesia care coordinator/facilitator/scheduler
Teaching
Administration
Research
Simulation centre (instructor, manager, coordinator, research)
Surgical procedures may be performed on an elective, urgent or emergent basis. Elective procedures are scheduled to permit an assessment of the patient’s fitness
