Intravenous Anesthetic Agents Overview

Intravenous Anesthetic Agents

• Intravenous anesthetic agents can be used to induce and maintain general anesthesia.
• IV agents include barbiturates, benzodiazepines, etomidate, ketamine, and propofol.

Barbiturates

• These drugs depress the central nervous system (CNS).
• They suppress the reticular activating system (RAS) in the brainstem, which is responsible for regulating consciousness.
• Barbiturates bind to GABA-A receptors, enhancing the inhibitory action of GABA.
• Their effects include sedation, hypnosis, and anesthesia.
• Barbiturates can cause a drop in blood pressure due to peripheral vasodilation.
• A slow induction rate allows for baroreceptor reflex compensation which helps maintain cardiac output.
• Barbiturates can cause apnea (temporary stop in breathing).
• Following induction, tidal volume and respiratory rate are decreased.

Benzodiazepines

• Benzodiazepines bind to GABA-A receptors but at a different site than barbiturates.
• Midazolam is water soluble at low pH.
• Diazepam and lorazepam are insoluble in water and may cause venous irritation.
• Benzodiazepines have no direct analgesic properties.
• Their effects progress from antianxiety to stupor and unconsciousness with increasing doses.
• Coadministration with opioids can produce myocardial depression and hypotension.
• Patient ventilation must be monitored when using intravenous benzodiazepines.

Ketamine

• Ketamine produces a unique form of dissociative anesthesia, leading to a disconnect between sensory perception and conscious awareness.
• This disconnect is due to ketamine's action on NMDA receptors in the brain.
• Patients may appear conscious but are unaware of their surroundings.
• Ketamine increases arterial blood pressure, heart rate, and cardiac output.
• Large doses should be administered cautiously in patients with heart conditions or uncontrolled hypertension.

Etomidate

• Etomidate depresses the reticular activating system and mimics the inhibitory effects of GABA.
• It often causes myoclonus (muscle twitching) during induction of anesthesia.
• Etomidate contains a carboxylated imidazole ring, making it soluble in acidic solutions and lipid soluble at physiological pH.
• It is mixed with propylene glycol for injection, which may cause pain.
• Induction doses transiently inhibit cortisol and aldosterone synthesis.
• Long-term infusion can lead to adrenocortical suppression.

Propofol

• It facilitates inhibitory neurotransmission, likely by binding to GABA-A receptors.
• Propofol is not water soluble but is available as a 1% aqueous solution.
• The solution contains soybean oil, glycerol, and egg lecithin, which may cause injection pain.
• Mixing lidocaine with propofol can reduce injection pain.
• Propofol formulations can support bacterial growth, so sterile technique is crucial.
• Propofol can cause hypotension, especially with large doses or rapid injection.
• It depresses upper airway reflexes more than thiopental.
• It has antiemetic effects.
• Induction is sometimes accompanied by excitatory phenomena like muscle twitching or hiccupping.

Intravenous Anesthetic Agents

• General anesthesia can be induced and maintained with drugs administered through a variety of routes, including intravenous, oral, rectal, transdermal, transmucosal and intramuscular
• Intravenous anesthetic agents include barbiturates, benzodiazepines, ketamine, etomidate and propofol.

Barbiturates

• Barbiturates are a class of drugs that depress the central nervous system (CNS) and primarily work to calm the body and mind
• Barbiturates suppress the reticular activating system (RAS) in the brainstem, a part of the brain responsible for regulating consciousness, alertness, and wakefulness, which leads to drowsiness and relaxation. At higher doses, it can cause unconsciousness
• Barbiturates affect synaptic functions, rather than directly altering the excitability of neurons
• Barbiturates are used in medicine as sedatives, hypnotics, and, in higher doses, anesthetics
• Barbiturates, can cause a drop in blood pressure due to peripheral vasodilation
• The body has the chance to gradually adapt through a compensatory mechanism known as the baroreceptor reflex
• The baroreceptor reflex works by increasing heart rate, enhancing myocardial contractility, and increasing blood pressure.

Benzodiazepines

• Benzodiazepines bind the same set of receptors in the central nervous system as barbiturates but bind to a different site on the receptors (GABAA)
• Midazolam is water soluble at low pH.
• Diazepam and lorazepam are insoluble in water, so parenteral preparations contain propylene glycol, which can produce venous irritation
• Coadministration with opioids produce myocardial depression and arterial hypotension
• Benzodiazepines have no direct analgesic properties.
• The antianxiety, amnestic, and sedative effects seen at lower doses progress to stupor and unconsciousness at induction doses.

Ketamine

• Ketamine produces a unique form of dissociative anesthesia where patients may seem conscious, showing signs like eye opening, swallowing, or muscle movements, but they are unable to process or respond meaningfully to sensory input.
• This effect results from ketamine’s action on NMDA receptors in the brain, leading to a disconnect between sensory perception and conscious awareness, making patients appear awake but unaware or unresponsive to their surroundings.
• Ketamine has multiple effects throughout the central nervous system, inhibiting polysynaptic reflexes in the spinal cord as well as excitatory neurotransmitter effects in selected areas of the brain.
• ketamine functionally “dissociates” the thalamus (which relays sensory impulses from the reticular activating system to the cerebral cortex) from the limbic cortex (which is involved with the awareness of sensation)
• In contrast to other anesthetic agents, ketamine increases arterial blood pressure, heart rate, and cardiac output
• Large bolus injections of ketamine should be administered cautiously in patients with coronary artery disease, uncontrolled hypertension, congestive heart failure, or arterial aneurysms.

Etomidate

• Etomidate depresses the reticular activating system and mimics the inhibitory effects of GABA.
• There is a 30-60% incidence of myoclonus with etomidate induction of anesthesia.
• Etomidate contains a carboxylated imidazole. The imidazole ring provides water solubility in acidic solutions and lipid solubility at physiological pH.
• Etomidate is dissolved in propylene glycol for injection. This solution often causes pain on injection that can be lessened by a prior intravenous injection of lidocaine.
• Induction doses of etomidate transiently inhibit enzymes involved in cortisol and aldosterone synthesis.
• Long-term infusion and adrenocortical suppression were associated with an increased mortality rate in critically ill (particularly septicemia) patients.

Propofol

• Propofol induction of general anesthesia may involve facilitation of inhibitory neurotransmission mediated by GABA A receptor binding
• Propofol is not water soluble, but a 1% aqueous solution (10 mg/mL) is available for intravenous administration as an oil-in-water emulsion containing soybean oil, glycerol, and egg lecithin.
• A history of egg allergy does not necessarily contraindicate the use of propofol.
• This formulation will often cause pain during injection that can be decreased by prior injection of lidocaine or less effectively by mixing lidocaine with propofol prior to injection.
• Propofol formulations can support the growth of bacteria, so sterile technique must be observed in preparation and handling.
• Propofol should be administered within 6 h of opening the ampule. Sepsis and death have been linked to contaminated propofol preparations.
• Factors associated with propofol-induced hypotension include large doses, rapid injection, and old age.
• Propofol-induced depression of upper airway reflexes exceeds that of thiopental, allowing intubation, endoscopy, or laryngeal mask placement in the absence of neuromuscular blockade.
• Its antiemetic effects provide another reason for it to be a preferred drug for outpatient anesthesia.
• Induction is occasionally accompanied by excitatory phenomena such as muscle twitching, spontaneous movement, opisthotonus, or hiccupping.

Intravenous Anesthetic Agents

• General anesthesia can be achieved by administering drugs intravenously.
• Intravenous anesthetics include barbiturates, benzodiazepines, ketamine, etomidate, and propofol.

Barbiturates

• Barbiturates are CNS depressants that calm the body and mind.
• They suppress the reticular activating system (RAS), which regulates wakefulness.
• Barbiturates bind to GABA-A receptors, which respond to GABA, increasing the inhibitory action of GABA.
• Barbiturates primarily affect synaptic transmission.
• Barbiturates are used as sedatives, hypnotics, and, in higher doses, anesthetics.
• Barbiturates can cause a drop in blood pressure due to peripheral vasodilation.
• Slow administration rate can mitigate the effects of vasodilation through baroreceptor reflexes.
• Baroreceptors monitor blood pressure and trigger compensatory responses, such as increasing heart rate and enhancing myocardial contractility, to maintain blood pressure.
• Barbiturates can cause apnea after induction, and decrease tidal volume and respiratory rate during awakening.

Benzodiazepines

• Benzodiazepines bind to the same GABA-A receptors as barbiturates, but to a different site.
• Midazolam is water-soluble at low pH, while diazepam and lorazepam are insoluble and require propylene glycol, which can cause venous irritation.
• Co-administration with opioids can cause myocardial depression and arterial hypotension.
• Benzodiazepines do not have analgesic properties.
• Benzodiazepines cause antianxiety, amnestic, and sedative effects at lower doses and progress to stupor and unconsciousness at higher doses.

Ketamine

• Ketamine is a dissociative anesthetic that causes a unique form of anesthesia, leaving patients seemingly awake, but unable to process or respond meaningfully to sensory input.
• Ketamine inhibits polysynaptic reflexes in the spinal cord and excitatory neurotransmitter effects in the brain.
• Ketamine functionally “dissociates” the thalamus from the limbic cortex.
• Ketamine increases arterial blood pressure, heart rate, and cardiac output.
• Ketamine should be administered cautiously in patients with coronary artery disease, uncontrolled hypertension, congestive heart failure, or arterial aneurysms.

Etomidate

• Etomidate depresses the reticular activating system and mimics the inhibitory effects of GABA.
• Etomidate can cause myoclonus or muscle spasms.
• Etomidate contains a carboxylated imidazole, which makes it soluble in acidic solutions and lipid-soluble at physiological pH.
• Etomidate is dissolved in propylene glycol, which may cause pain on injection.
• Etomidate transiently inhibits cortisol and aldosterone synthesis.
• Long-term infusion of etomidate in patients with sepsis can increase mortality.

Propofol

• Propofol induction of general anesthesia may involve facilitation of inhibitory neurotransmission mediated by GABA-A receptor binding.
• Propofol is not water-soluble and is administered as a 1% aqueous solution containing soybean oil, glycerol, and egg lecithin.
• Propofol can cause pain during injection, which can be mitigated by administering lidocaine prior or mixing with propofol.
• Propofol formulations can support bacterial growth, therefore sterile technique is crucial.
• Propofol preparations should be administered within 6 hours of opening.
• Large doses, rapid injection, and old age are associated with propofol-induced hypotension.
• Propofol depresses upper airway reflexes more than thiopental.
• Propofol has antiemetic effects.
• Propofol induction can be accompanied by excitement and muscle twitching.

Intravenous Anesthetic Agents

• General anesthesia can be induced and maintained using various routes of administration.
• Intravenous anesthetic agents include:
  • Barbiturates
  • Benzodiazepines
  • Ketamine
  • Etomidate
  • Propofol

Barbiturates

• Barbiturates are central nervous system (CNS) depressants.
• They suppress the reticular activating system (RAS) in the brainstem, which regulates consciousness, alertness, and wakefulness.
• Barbiturates bind to GABA-A receptors, enhancing the inhibitory action of GABA, leading to sedation and relaxation.
• Barbiturates can cause a drop in blood pressure due to peripheral vasodilation.
• Slower rates of barbiturate induction reduce hemodynamic responses.
• Apnea often follows an induction dose.

Benzodiazepines

• Benzodiazepines bind to the same set of receptors in the CNS as barbiturates, but to a different site on the GABA-A receptor.
• Midazolam is water-soluble at low pH.
• Diazepam and lorazepam are insoluble in water and require propylene glycol for parenteral preparations, which can cause venous irritation.
• Co-administration of benzodiazepines with opioids can produce myocardial depression and arterial hypotension.
• Benzodiazepines do not possess direct analgesic properties.

Ketamine

• Ketamine produces dissociative anesthesia, where patients may appear conscious but are unresponsive to sensory input.
• Ketamine affects NMDA receptors in the brain, leading to a disconnect between sensory perception and conscious awareness.
• Ketamine inhibits polysynaptic reflexes in the spinal cord and excitatory neurotransmitter effects in selected brain areas.
• Ketamine functionally "dissociates" the thalamus from the limbic cortex.
• Unlike other anesthetic agents, ketamine increases arterial blood pressure, heart rate, and cardiac output.
• Large bolus injections of ketamine should be administered cautiously in patients with coronary artery disease, uncontrolled hypertension, congestive heart failure, or arterial aneurysms.

Etomidate

• Etomidate depresses the reticular activating system and mimics the inhibitory effects of GABA.
• Etomidate induction often causes myoclonus (muscle twitching).
• Etomidate contains a carboxylated imidazole that provides water solubility in acidic solutions and lipid solubility at physiological pH.
• Etomidate is dissolved in propylene glycol for injection, which can cause pain and may be lessened with a prior lidocaine injection.
• Induction doses of etomidate transiently inhibit enzymes involved in cortisol and aldosterone synthesis.
• Long-term infusion of etomidate can lead to adrenocortical suppression, which can increase mortality in critically ill patients.

Propofol

• Propofol induction of general anesthesia may involve facilitation of inhibitory neurotransmission through GABA-A receptor binding.
• Propofol is not water-soluble, a 1% aqueous solution is available as an oil-in-water emulsion containing soybean oil, glycerol, and egg lecithin.
• Propofol injection can cause pain that can be minimized with prior lidocaine injection or mixing lidocaine with propofol.
• Propofol formulations can support bacterial growth, so sterile technique is necessary for preparation and handling.
• Propofol-induced hypotension can be exacerbated by large doses, rapid injection, and old age.
• Propofol depresses upper airway reflexes more than thiopental, allowing intubation, endoscopy, or laryngeal mask placement without neuromuscular blockade.
• Propofol has antiemetic effects.
• Propofol induction can be accompanied by excitatory phenomena like muscle twitching, spontaneous movement, opisthotonus, or hiccupping.

Intravenous Anesthetic Agents

• Intravenous anesthetic agents are used to induce and maintain anesthesia.
• Administration routes include oral, rectal, transdermal, transmucosal, intramuscular, and intravenous

Barbiturates

• Barbiturates depress the CNS and are used as sedatives, hypnotics, and anesthetics.
• They primarily work by suppressing the reticular activating system (RAS) in the brainstem.
• Barbiturates also bind to GABA-A receptors, enhancing the inhibitory action of GABA.
• They decrease neurotransmitter release and reduce synaptic transmission.
• Hemodynamic responses are reduced by slower rates of induction.
• Cardiac output is often maintained by an increased heart rate and increased myocardial contractility from compensatory baroreceptor reflexes.
• Barbiturates can cause a drop in blood pressure due to peripheral vasodilation.
• Slow administration allows the body to gradually adapt through the baroreceptor reflex.
• Apnea often follows an induction dose.
• During awakening, tidal volume and respiratory rate are decreased following barbiturate induction

Benzodiazepines

• Benzodiazepines bind to the same receptors as barbiturates, but at a different site (GABAA).
• Midazolam is water-soluble at low pH.
• Diazepam and lorazepam are insoluble in water and require propylene glycol, which can cause venous irritation.
• Coadministration with opioids can produce myocardial depression and arterial hypotension.
• Ventilation must be monitored in all patients receiving intravenous benzodiazepines with resuscitation equipment readily available.
• Benzodiazepines do not have direct analgesic properties.
• Antianxiety, amnestic, and sedative effects seen at lower doses progress to stupor and unconsciousness at induction doses.

Ketamine

• Ketamine produces dissociative anesthesia, characterized by apparent consciousness but inability to process sensory input.
• It acts on NMDA receptors in the brain, disconnecting sensory perception from conscious awareness.
• Ketamine inhibits polysynaptic reflexes in the spinal cord and excitatory neurotransmitter effects in selected areas of the brain.
• It functionally "dissociates" the thalamus from the limbic cortex.

Ketamine: Effects on Organ Systems

• In contrast to other anesthetic agents, ketamine increases arterial blood pressure, heart rate, and cardiac output.
• Increases in pulmonary artery pressure and myocardial work also occur.
• Large bolus injections should be administered cautiously in patients with coronary artery disease, uncontrolled hypertension, congestive heart failure or arterial aneurysms

Etomidate

• Etomidate depresses the reticular activating system and mimics the inhibitory effects of GABA.
• It contains a carboxylated imidazole ring, providing water solubility in acidic solutions and lipid solubility at physiological pH.
• It is dissolved in propylene glycol for injection, which can cause pain that can be reduced by prior intravenous injection of lidocaine.
• Induction doses of etomidate transiently inhibit enzymes involved in cortisol and aldosterone synthesis.

Propofol

• Propofol induction of general anesthesia may involve facilitation of inhibitory neurotransmission mediated by GABA A receptor binding
• It is not water soluble but is available as a 1% aqueous solution (10 mg/mL) in an oil-in-water emulsion.
• A history of egg allergy does not necessarily contraindicate the use of propofol.
• This formulation often causes pain during injection, lessened by prior injection of lidocaine or mixing lidocaine with propofol before injection.
• Propofol formulations can support bacterial growth, requiring sterile technique in preparation and handling.
• It should be administered within 6 hours of opening the ampule.
• Factors associated with propofol-induced hypotension include large doses, rapid injection, and old age.
• Propofol-induced depression of upper airway reflexes exceeds that of thiopental.
• Its antiemetic effects make it a preferred drug for outpatient anesthesia.
• Induction is occasionally accompanied by excitatory phenomena such as muscle twitching, spontaneous movement, opisthotonus, or hiccupping.

Introduction to Intravenous Anesthetic Agents

• Intravenous anesthetic agents are used to induce and maintain general anesthesia.
• Intravenous anesthetic agents are administered through a wide range of routes including oral, rectal, transdermal, transmucosal, intramuscular, and intravenous.
• Intravenous anesthetic agents include barbiturates, benzodiazepines, ketamine, etomidate, and propofol.

Barbiturates

• Barbiturates are a class of drugs that depress the central nervous system (CNS).
• Barbiturates suppress the reticular activating system (RAS) in the brainstem.
• Barbiturates bind to GABA-A receptors.
• Barbiturates reduce neural activity in the brain by enhancing the inhibitory action of GABA.
• Barbiturates can cause a drop in blood pressure due to peripheral vasodilation.
• Barbiturates can lead to apnea (temporary stop in breathing).
• Barbiturates decrease tidal volume and respiratory rate.

Benzodiazepines

• Benzodiazepines bind to the same set of receptors in the central nervous system as barbiturates but bind to a different site on the receptors (GABAA).
• Midazolam is water soluble at low pH.
• Diazepam and lorazepam are insoluble in water.
• Coadministration with opioids produces myocardial depression and arterial hypotension.
• Benzodiazepines have no direct analgesic properties.

Ketamine

• Ketamine produces a unique form of dissociative anesthesia.
• Ketamine inhibits polysynaptic reflexes in the spinal cord.
• Ketamine "dissociates" the thalamus from the limbic cortex.
• Ketamine increases arterial blood pressure, heart rate, and cardiac output.
• Large bolus injections of ketamine should be cautiously administered in patients with coronary artery disease, uncontrolled hypertension, congestive heart failure, or arterial aneurysms.

Etomidate

• Etomidate depresses the reticular activating system.
• Etomidate mimics the inhibitory effects of GABA.
• Etomidate contains a carboxylated imidazole.
• Etomidate is dissolved in propylene glycol for injection, which can cause pain on injection.
• Etomidate transiently inhibits enzymes involved in cortisol and aldosterone synthesis.

Propofol

• Propofol may involve facilitation of inhibitory neurotransmission mediated by GABA A receptor binding.
• Propofol is not water soluble but is available as a 1% aqueous emulsion for intravenous administration.
• Propofol formulations can support the growth of bacteria, so sterile technique must be observed in preparation and handling.
• Propofol-induced hypotension is associated with large doses, rapid injection, and old age.
• Propofol-induced depression of upper airway reflexes exceeds that of thiopental.
• Propofol has antiemetic effects.
• Propofol induction is occasionally accompanied by excitatory phenomena such as muscle twitching, spontaneous movement, opisthotonus, or hiccupping.

Intravenous Anesthetic Agents

• General anesthesia can now be induced and maintained with drugs administered through various routes, including intravenously.
• Intravenous anesthetic agents include barbiturates, benzodiazepines, ketamine, etomidate, and propofol.

Barbiturates

• Barbiturates are CNS depressants that calm the body and mind.
• They suppress the reticular activating system (RAS) in the brainstem, which regulates consciousness.
• Barbiturates bind to GABA-A receptors and enhance the inhibitory action of GABA, leading to sedation.
• Barbiturates can cause a drop in blood pressure due to peripheral vasodilation, but this effect can be reduced by slow administration.
• The baroreceptor reflex helps maintain cardiac output by increasing heart rate and myocardial contractility in response to a drop in blood pressure.
• Barbiturate induction often leads to apnea, followed by decreased tidal volume and respiratory rate during awakening.

Benzodiazepines

• Benzodiazepines bind to GABAA receptors, but at a different site than barbiturates.
• Midazolam is water-soluble at low pH, while diazepam and lorazepam are insoluble and require propylene glycol for injection, which can cause venous irritation.
• Coadministration of benzodiazepines with opioids can cause myocardial depression and arterial hypotension.
• Intravenous benzodiazepines require close monitoring of ventilation and immediate resuscitation equipment.
• Benzodiazepines lack analgesic properties but produce antianxiety, amnestic, and sedative effects that progress to stupor and unconsciousness at induction doses.

Ketamine

• Ketamine produces dissociative anesthesia, where patients appear conscious but are unresponsive to sensory input.
• It acts on NMDA receptors, disconnecting sensory perception from conscious awareness.
• Ketamine increases arterial blood pressure, heart rate, and cardiac output, unlike other anesthetics.
• It also increases pulmonary artery pressure and myocardial work.
• Large bolus injections of ketamine should be administered cautiously in patients with coronary artery disease, uncontrolled hypertension, congestive heart failure, or arterial aneurysms.

Etomidate

• Etomidate depresses the reticular activating system and mimics the inhibitory effects of GABA.
• 30-60% of patients experience myoclonus during etomidate-induced anesthesia.
• Etomidate contains a carboxylated imidazole that provides water solubility in acidic solutions and lipid solubility at physiological pH.
• It is dissolved in propylene glycol for injection, which can cause pain that can be lessened by a prior intravenous injection of lidocaine.
• Induction doses of etomidate transiently inhibit enzymes involved in cortisol and aldosterone synthesis.
• Long-term etomidate infusion and adrenocortical suppression were associated with increased mortality in critically ill patients, particularly those with sepsis.

Propofol

• Propofol induction of anesthesia may involve facilitation of inhibitory neurotransmission mediated by GABA-A receptor binding.
• Propofol is not water-soluble but is available as a 1% aqueous solution (10 mg/mL) as an oil-in-water emulsion.
• It can cause pain during injection that can be decreased by prior injection of lidocaine or by mixing lidocaine with propofol.
• Propofol formulations support bacterial growth, so sterile technique is crucial in preparation and handling.
• Propofol-induced hypotension can be influenced by factors like large doses, rapid injection, and old age.
• Propofol depresses upper airway reflexes more than thiopental, allowing intubation, endoscopy, or laryngeal mask placement without neuromuscular blockade.
• Propofol's antiemetic effects make it a preferred drug for outpatient anesthesia.
• Propofol induction is occasionally accompanied by excitatory phenomena like muscle twitching, spontaneous movement, opisthotonus, or hiccupping.

Intravenous Anesthetic Agents

• General anesthesia historically relied on inhaled agents, but administering anesthetic drugs through a wide range of routes, including oral, rectal, transdermal, transmucosal, intramuscular, or intravenous, is now common.
• Intravenous anesthetic agents include:
  • Barbiturates
  • Benzodiazepines
  • Ketamine
  • Etomidate
  • Propofol

Barbiturates

• Barbiturates are a class of drugs that depress the central nervous system (CNS) and primarily work to calm the body and mind.
• Barbiturates suppress the reticular activating system (RAS) in the brainstem, responsible for regulating consciousness, alertness, and wakefulness.
• Barbiturates bind to GABA-A receptors, which are receptors for GABA, a natural inhibitory neurotransmitter that calms neural signals in the brain.
• Barbiturates enhance the inhibitory action of GABA, resulting in sedation and relaxation.
• Barbiturates can cause a drop in blood pressure due to peripheral vasodilation.
• Slow administration of barbiturates allows the body to adapt through the baroreceptor reflex, which helps maintain cardiac output.
• Barbiturates often cause apnea, which can be followed by decreased tidal volume and respiratory rate upon awakening.

Benzodiazepines

• Benzodiazepines bind to the same receptors as barbiturates in the central nervous system, but bind to a different site.
• Midazolam is water soluble at low pH.
• Diazepam and lorazepam are insoluble in water and require propylene glycol, which can cause venous irritation.
• Combining benzodiazepines with opioids can lead to myocardial depression and arterial hypotension.
• Benzodiazepines lack direct analgesic properties.
• Benzodiazepines have antianxiety, amnestic, and sedative effects at lower doses, which progress to stupor and unconsciousness at induction doses.

Ketamine

• Ketamine produces a unique form of dissociative anesthesia, where patients appear awake but are unresponsive to their surroundings.
• Ketamine has multiple effects on the central nervous system, including inhibiting polysynaptic reflexes in the spinal cord and excitatory neurotransmitter effects in specific brain areas.
• Ketamine functionally "dissociates" the thalamus from the limbic cortex, resulting in the disconnect between sensory perception and conscious awareness.
• Ketamine increases arterial blood pressure, heart rate, and cardiac output in contrast to other anesthetic agents.
• Large bolus injections of ketamine should be administered cautiously in patients with coronary artery disease, uncontrolled hypertension, congestive heart failure, or arterial aneurysms.

Etomidate

• Etomidate depresses the reticular activating system and mimics the inhibitory effects of GABA.
• Myoclonus (involuntary muscle twitches) occurs in 30-60% of patients during etomidate induction of anesthesia.
• Etomidate contains a carboxylated imidazole ring that makes it water soluble in acidic solutions and lipid soluble at physiological pH.
• Etomidate is dissolved in propylene glycol for injection, which often causes pain that can be lessened by pre-treating with lidocaine.
• Etomidate transiently inhibits enzymes involved in cortisol and aldosterone synthesis.
• Long-term infusions and adrenocortical suppression have been associated with increased mortality in critically ill patients, especially those with sepsis.

Propofol

• Propofol induces anesthesia by facilitating inhibitory neurotransmission mediated by GABA A receptor binding.
• Propofol is not water soluble but is formulated as a 1% aqueous solution (10 mg/mL) as an oil-in-water emulsion containing soybean oil, glycerol, and egg lecithin.
• A history of egg allergy does not necessarily contraindicate the use of propofol.
• Propofol formulations often cause pain during injection, which can be reduced by pre-treating with lidocaine or mixing lidocaine with propofol before injection.
• Propofol formulations can support bacterial growth, necessitating sterile technique in preparation and handling.
• Propofol should be administered within 6 hours of opening the ampule.
• Factors associated with propofol-induced hypotension include large doses, rapid injection, and old age.
• Propofol causes greater depression of upper airway reflexes than thiopental, which enables intubation, endoscopy, or laryngeal mask placement without neuromuscular blockade.
• Propofol's antiemetic effects make it a preferred drug for outpatient anesthesia.
• Induction with propofol can be accompanied by excitatory phenomena such as muscle twitching, spontaneous movement, opisthotonus, or hiccupping.

Intravenous Anesthetic Agents

• General anesthesia can be induced using intravenous drugs, in addition to inhaled agents.
• Intravenous anesthetic agents include: Barbiturates, Benzodiazepines, Ketamine, Etomidate, Propofol.

Barbiturates

• Barbiturates are CNS depressants that reduce brain and body activity.
• Barbiturates bind to GABA-A receptors, increasing chloride ion flow into nerve cells, and reducing neuron activity.
• Barbiturates primarily affect synaptic functions by decreasing neurotransmitter release and limiting communication between neurons.
• Barbiturates can cause a drop in blood pressure due to peripheral vasodilation.
• Slow administration of barbiturates allows compensatory mechanisms (like the baroreceptor reflex) to respond effectively, minimizing hemodynamic changes.
• Barbiturates can cause apnea and decrease tidal volume and respiratory rate.

Benzodiazepines

• Benzodiazepines bind to the same receptors as barbiturates but at a different site.
• Midazolam is water soluble at low pH, while Diazepam and Lorazepam are insoluble.
• Benzodiazepines combined with opioids can cause myocardial depression and hypotension.
• All patients receiving IV benzodiazepines require careful monitoring for respiratory depression, with resuscitation equipment readily available.
• Benzodiazepines lack analgesic properties.

Ketamine

• Ketamine produces a unique dissociative anesthesia, where patients appear conscious but are unresponsive to sensory input.
• This effect results from ketamine’s action on NMDA receptors in the brain.
• Ketamine inhibits polysynaptic reflexes and excitatory neurotransmitter effects in the brain.
• Ketamine functionally “dissociates” the thalamus from the limbic cortex.
• Ketamine increases arterial blood pressure, heart rate, cardiac output, pulmonary artery pressure, and myocardial work.
• Ketamine should be used cautiously in patients with cardiovascular issues like coronary artery disease, uncontrolled hypertension, or congestive heart failure.

Etomidate

• Etomidate depresses the reticular activating system and mimics GABA’s effects.
• Etomidate can cause myoclonus.
• Etomidate is dissolved in propylene glycol for injection, which often causes pain.
• Etomidate can transiently inhibit enzymes involved in cortisol and aldosterone synthesis.
• Long-term etomidate infusion can lead to adrenocortical suppression, which may be associated with increased mortality in critically ill patients (particularly those with sepsis).

Propofol

• Propofol acts by possibly facilitating inhibitory neurotransmission by binding to GABA-A receptors.
• Propofol is not water soluble and is administered as an oil-in-water emulsion.
• A history of egg allergy does not necessarily contraindicate the use of propofol.
• Propofol can cause pain during injection, often minimized by prior injection of lidocaine.
• Propofol formulations can support bacterial growth, requiring sterile technique and quick administration after opening.
• Factors like large doses, rapid injection, and old age are associated with propofol-induced hypotension.
• Propofol depresses upper airway reflexes more than thiopental, facilitating intubation, endoscopy, or laryngeal mask placement.
• Propofol has antiemetic effects.
• Induction with propofol can sometimes cause excitatory phenomena such as muscle twitching or hiccupping.

This quiz explores various intravenous anesthetic agents, including barbiturates and benzodiazepines. It covers their mechanisms of action, effects on the central nervous system, and implications for anesthesia practices. Test your knowledge on these critical components of anesthesia management.