General Anesthesia pt.1 Flashcards
How is general anesthesia induced and maintained?
- Several different types of drugs are given together during general anasthesia
- Induced with either a volatile drug given by inhalation or with an intravenously administered drug
- Maintained with an inhalational or intravenous anaesthetic
- Analgesics, usually short acting opioids are also used
- ## The use of neuromuscular blocking agents if endotracheal intubation isplanned, necessitates intermittent positive-pressure ventilation
Following surgery, what drugs can be given to reverse effects of general anasthesia?
- Anticholinesterases can be given to reverse the ffects of neuromuscular blocking drugs
- Specific antagonists can be used to reverse central and respiratory depression caused by some drugs used in surgery
What can be given to reduce pain from injection?
Local topical anaesthetic
Dosing consideration in anesthesia
- Individual requirements vary considerably and the recommended doses are only a guide
- Agents are adjusted based on age, frailty, and comorbid medical conditions
Smaller doses are indicated in ill, shocked, or debilitated patients and in significant hepatic impairment, while robust individuals may require larger doses
The required dose of induction agent may be less if the patient has been premedicated with a sedative agent or if an opioid analgesic has been used
What are the phases of general anasthesisa?
GA has three distinct phases: induction, maintenance, and emergence
Anesthetic agent dose response
- Anesthetic agents demonstrate a dose-response effect, with progressively higher doses providing progressively deeper levels of sedation and anesthesia
- Notably, sedation progresses to GA as a continuum of effect during induction, rather than as a consecutive series of distinct states with clear transitions
- As the patient progresses from Stage I to stage III surgical anesthesia, airway reflexes and patency,spontaneous ventilation, cardiovascular function, and muscle tone become increasingly depressed
What is used to facilitate tracehal intubation in GA?
Induction is usually followed by a neuromuscular blocking agent or a short acting opioid
What is it called when only intravenous anaesthesia is used in a surgery?
Total intravenous anaesthesia
Drugs used for intravenous anesthesia
They include:
- Propofol (most widely used)
- Thiopental sodium
- Etomidate
- Ketamine (used rarely)
What is general anesthesia?
a reversible state that includes:
- Hypnosis
- Amnesia
- Analgesia
- Akinesia
- Autonomic and sensory block
What is the goal of induction in GA?
The goals for induction of general anesthesia are to rapidly, safely, and pleasantly produce a state of general anaesthesia while maintaining adequate oxygenation, ventilation, and hemodynamic stability.
What can sedation be divided into?
- Light/minimal sedation with anxiolysis and analgesia is a level in which responsiveness to voice,airway patency, spontaneous ventilation, and cardiovascular function are preserved.
- Moderate sedation, also termed conscious sedation, represents a deeper level of sedation and analgesia,in which the patient remains responsive to voice, has intact airway patency and spontaneous ventilation, but may have reduced blood pressure
- Deep sedation is a state in which the patient no longer responds to voice, and may have compromised airway patency, ventilation, and cardiovascular function. - However, movement in response to a noxious surgical stimulus still occurs
- General anesthesia is an anesthetic depth at which the patient will not respond to voice or to noxious surgical stimuli
Drugs that should be prepared for anesthetic induction
Routinely administered anesthetic drugs should be prepared. Drugs for treatment of common complications and emergencies should be immediately available. These include but are not limited to:
- A sedative/hypnotic
- A neuromuscular blocking agent (NMBA)
- A vasopressor, most commonly
phenylephrine. alternatives include
ephedrine or dilute norepinephrine
as appropriate
- An anticholinergic (atropine or glycopyrrolate)
What is the ideal induction agent for GA?
- The ideal induction agent has a rapid onset of action, minimal cardiopulmonary or other side effects, and is cleared from the bloodstream quickly so that recovery is rapid.
- However, none of the available induction agents is ideal for all patients, and all have side effects. We typically administer combinations of agents from different pharmacologic classes during induction and/or maintenance of general anesthesia.
- This strategy minimizes the total dose of any one anesthetic agent, thereby reducing the incidence of undesirable side effects.
- Age and coexisting diseases affect selection and dosing of anesthetic induction and adjuvant agents
IV vs inhalation for induction in GA
- Most adults prefer induction primarily with IV agents
- Notably, adults may be less satisfied with a primary inhalation induction technique compared with IV induction due to the unpleasant odor of anesthetic gases, as well as a higher incidence of postoperative nausea and vomiting compared with use of IV agents such as
propofol - Furthermore, inhalation induction time is longer compared with IV induction. Several minutes of ventilation may be required. Thus, this technique is unsuitable for rapid sequence inductionand intubation (RSII).
