10 Mar 25 Inhaled anesthetics Pt 2 Flashcards
What are the three types of gas delivery systems used in anesthesia?
- Bag-Valve-Mask
- Vein Circuit
- Circle System
These systems are used for delivering oxygen and volatile anesthetics during procedures.
What is the primary function of the bag-valve-mask system?
To deliver oxygen and air, especially in emergency situations
It is not ideal for delivering volatile anesthetics.
What is a key advantage of the circle system in anesthesia?
- Fresh gas inlet
- Unidirectional valve
- CO2 absorbent
- Reservoir
These features help prevent gas backflow and maintain patient ventilation.
What is the difference between high flow and low flow anesthesia?
High flow is used to build up oxygen reserves; low flow is less costly and causes slower changes in anesthetic levels
High flow is typically used during induction.
What volatile anesthetic is noted for its bronchodilating effects?
Sevoflurane
It is particularly beneficial for patients with bronchospasm.
What is the significance of the MAC value in anesthesia?
It indicates the concentration of anesthetic needed to prevent movement in 50% of patients
It is crucial for determining anesthetic dosage.
What effect do volatile anesthetics have on cerebral blood flow?
They cause a dose-dependent increase in cerebral blood flow
Sevoflurane has the least effect on cerebral blood flow among volatile agents.
What is the potential consequence of using nitrous oxide in neonates?
Increased pulmonary vascular resistance
This makes nitrous oxide unsuitable for use in neonates.
What is compound A and its relevance in anesthesia?
A metabolite associated with nephrotoxicity from volatile anesthetics
Its formation is influenced by low flow anesthesia with sevoflurane.
What is malignant hyperthermia and its trigger?
A genetic predisposition condition triggered by volatile anesthetics and succinylcholine
It can be treated with dantrolene.
What does the term ‘second gas effect’ refer to?
The phenomenon where nitrous oxide increases the concentration of other gases
It is beneficial but can also lead to side effects like nausea.
Fill in the blank: Volatile anesthetics can decrease _______ and _______ response.
hypoxic; hypercapnic
This blunting can affect patient ventilation and oxygenation.
True or False: Sevoflurane is associated with significant cerebral vasodilation.
False
Sevoflurane is noted for minimal cerebral vasodilation, making it suitable for neuro patients.
What is the impact of volatile anesthetics on renal blood flow?
They decrease renal blood flow and glomerular filtration rate (GFR)
This necessitates maintaining adequate hydration during anesthesia.
What should be avoided to reduce the pro-emetic effects of nitrous oxide?
Using nitrous oxide above half a MAC
This can help manage post-operative nausea and vomiting.
Explain the concept of ischemic preconditioning.
Exposure to small amounts of ischemia can mitigate damage from larger exposures
This principle can influence anesthetic strategies in certain patients.
What effect do volatile anesthetics have on heart rate?
They cause a dose-dependent increase in heart rate
Higher rates are observed at higher MAC levels.
What is a common complaint regarding mask fit in the OR?
Gas leakage
This can lead to inadequate anesthesia delivery.
What is the relationship between volatile anesthetics and bone marrow suppression?
Volatile anesthetics can cause B12 deficiency, inhibiting DNA synthesis
This can lead to bone marrow suppression in some patients.
What is the difference between high flow and low flow in inhalation anesthesia?
High flow is when fresh gas flow exceeds minute ventilation, while low flow is when it is less than minute ventilation.
What is the purpose of using high flow oxygen during patient induction?
To build up oxygen reserves and to denitrogenate the patient.
What are the potential benefits of high flow oxygen during anesthesia?
- Rapid changes in anesthetic concentration
- Prevents re-breathing
- Maintains fresh gas flow
- Cools and humidifies the gas
What is a downside of using high flow oxygen in anesthesia?
It can be wasteful, leading to increased costs due to higher usage of fresh gas and volatile anesthetics.
What are the advantages of low flow anesthesia?
- Cost-effective
- Reduces drying and cooling of secretions
- Allows for slow changes in anesthetic concentration
True or False: Low flow anesthesia is more expensive than high flow anesthesia.
False
What is compound A and its relevance to low flow anesthetics?
It was a concern with Sevoflurane that has since been determined not to be a significant issue.
What factors influence the cost of anesthetic gases?
- Purchase volume
- Potency of the anesthetic
- Fresh gas flow rates
What is a common volatile anesthetic used for pediatric patients?
Sevoflurane
What is the mechanism by which volatile anesthetics induce bronchodilation?
They relax airway smooth muscle by blocking calcium.
Fill in the blank: The process by which exposure to ischemia in small amounts can protect the myocardium from later ischemic events is called _______.
ischemic preconditioning
What is the definition of one MAC in anesthesia?
The concentration of anesthetic at which 50% of patients do not move in response to a supramaximal stimulus.
What physiological effect do volatile anesthetics have on cerebral metabolic requirements?
They cause a dose-dependent decrease in cerebral metabolic requirements for oxygen.
What is a potential negative effect of volatile anesthetics on consciousness?
They depress awareness and can lead to unconsciousness at low doses.
What is the significance of maintaining intact epithelium for bronchodilation with volatile anesthetics?
Bronchodilation is most effective when the airway epithelium is intact and not inflamed or damaged.
What role does the flow rate of oxygen play in the delivery of anesthetic gases?
Higher flow rates increase the delivery rate and concentration of anesthetic gases to the patient.
How can the use of volatile anesthetics affect pediatric patients during induction?
They can provide a smoother induction and better bronchodilation, especially in patients with bronchospasm.
True or False: Nitrous oxide is included in the category of volatile anesthetics.
False
What is the recommended practice for using Sevoflurane in pediatric patients?
It is preferred due to its low irritability and effective bronchodilation.
What is one way to mitigate the effects of ischemia using volatile anesthetics?
By administrating small amounts of volatile anesthetic before a significant ischemic event.
What happens to a patient at 1.5 MAC?
Burst suppression occurs in EEG readings
Burst suppression means periods of electrical activity are depressed.
What is the effect of 2 MAC on EEG?
Electrical silence
2 MAC is not typically used as an anesthetic level.
Is there a preference among volatile anesthetics regarding CNS activity?
No, Isoflurane, Sevoflurane, and Desflurane have similar CNS activity at high concentrations.
What is a pro-convulsant volatile anesthetic?
Influrane
It is less commonly used in the US today.
What are somatosensory evoked potentials?
Responses from sensory stimulation that travel to the brain
Example: A poke to the toe results in a sensation registered in the brain.
What happens to somatosensory and motor evoked potentials under volatile anesthetics?
Amplitude decreases and latency increases.
What is the maximum MAC of volatile anesthetic recommended during SSEPs and MEPs?
Half a MAC
This helps maintain adequate amplitude and latency for evaluation.
What is the effect of volatile anesthetics on cerebral blood flow?
Cerebral blood flow increases due to vasodilation.
At what MAC does cerebral blood flow increase begin?
Around 0.6 MAC.
Which volatile anesthetic is preferred for neuro patients with head injuries?
Sevoflurane
It causes less vasodilation and therefore less increase in cerebral blood flow.
What is autoregulation in relation to blood pressure?
The ability of blood vessels to maintain constant blood flow despite changes in blood pressure.
What is the typical autoregulation range for blood pressure?
50 to 150 mmHg.
What can cause the resetting of autoregulation in hypertensive patients?
Chronic hypertension.
What is the consequence of losing autoregulation with volatile anesthetics?
Increased risk of inadequate cerebral perfusion at extremes of blood pressure.
Which volatile anesthetic has the least effect on increasing intracranial pressure (ICP)?
Sevoflurane.
What is the typical increase in ICP at about 0.8 MAC?
About 7 mmHg.
What happens to respiratory rate and tidal volume with increasing doses of volatile anesthetics?
Respiratory rate increases and tidal volume decreases.
At what MAC do respiratory center depression effects become significant?
Around 1.5 to 2 MAC.
What is the recommended approach for maintaining anesthesia with volatile agents?
Use a combination of half MAC of volatile and other agents like nitrous or narcotics.
What is the significance of maintaining a steady state in anesthesia?
To avoid fluctuations in consciousness during surgery.
What is the primary reason for not using a mask for anesthesia in cases?
It requires effort to maintain the mask on the face and manage ventilation
This limits the anesthesiologist’s ability to perform other tasks such as charting or administering medications.
What is the effect of volatile anesthetics on the hypoxic response?
They blunt the hypoxic response, reducing the body’s drive to breathe when oxygen levels are low
At 1.1 MAC, there is 100% depression of the hypoxic response.
What is hypoxic pulmonary vasoconstriction (HPV)?
A compensatory mechanism that optimizes ventilation-perfusion (V/Q) matching by directing blood flow away from poorly ventilated areas
Volatile anesthetics decrease the effectiveness of this response.
How do volatile anesthetics affect mean arterial pressure?
They cause vasodilation, leading to decreased mean arterial pressure
They also depress the myocardium in a dose-dependent manner.
What is the relationship between heart rate and volatile anesthetics?
There is a dose-dependent increase in heart rate with increased volatile anesthetic use
This occurs even at low concentrations for isoflurane and desflurane.
What is the MAC of desflurane?
6.6
This is important for determining the appropriate concentration during induction.
What can obscure tachycardia during anesthesia induction?
- Administration of opioids
- Use of beta blockers
- Patient anxiety
These factors can mask the expected increase in heart rate from volatile anesthetics.
What happens to cardiac output with increasing volatile anesthetics?
Cardiac output decreases due to a drop in systemic vascular resistance (SVR)
This is a result of both increased volatile concentration and vasodilation.
What is a common effect of volatile anesthetics on the QT interval?
Prolongation of the QT interval
This is particularly concerning when combined with other medications that also prolong the QT interval.
What effect do volatile anesthetics have on the immune system?
They suppress monocytes, macrophages, and T cells
This suppression may lead to increased recurrence of cancers post-general anesthesia.
How do volatile anesthetics affect liver blood flow?
They maintain or increase liver blood flow
This is in contrast to halothane, which significantly decreases hepatic flow.
What are the two types of hepatotoxicity associated with halothane?
- Type One: Mild, flu-like symptoms
- Type Two: Immune-mediated, severe illness with enzyme elevation
Type Two occurs about a month after exposure.
What is a key reason halothane is no longer used in the United States?
It caused significant hepatotoxicity
Modern anesthetics like isoflurane and desflurane do not have this issue.
What renal effects are observed with volatile anesthetics?
- Decreased renal blood flow
- Decreased GFR
- Decreased urine output
These effects are more pronounced in longer surgical cases.
What is the renal effect of volatile anesthetics like isoflurane?
Decreased renal blood flow, decreased GFR, decreased urine output
When is a Foley catheter typically placed during surgery?
After two hours of surgery
What factors contribute to decreased urine output during surgery?
- Decreased renal blood flow
- Decreased GFR
- Patient positioning
True or False: Urine output in the operating room is always expected to be 30 cc’s per hour.
False
What is the primary concern regarding urine output in patients undergoing surgery?
Adequate hydration
What is a common reason for not administering Lasix during surgery?
No significant reason to worry about urine output
What is compound A in relation to sevoflurane?
A nephrotoxin created under low flow anesthesia conditions
What components of absorbent were traditionally used with sevoflurane?
- Potassium hydroxide
- Sodium hydroxide
What change has been made to absorbent materials to reduce nephrotoxicity?
Transition to calcium hydroxide
What is the significant threshold of compound A that could cause acute tubular necrosis in rats?
100 parts per million
What is the current belief regarding the clinical significance of compound A in adults under low flow anesthesia?
Not clinically significant
What is a potential risk when sevoflurane reacts with desiccated absorbent?
Spontaneous combustion
What is malignant hyperthermia?
An inherited genetic condition triggered by volatiles and succinylcholine causing hypermetabolic state
What is the treatment for malignant hyperthermia?
Dantrolene
What does dantrolene do?
It is a calcium channel blocker
What are common triggers for postoperative nausea and vomiting?
- Female gender
- Prior history of nausea
- Family history of nausea
Fill in the blank: Nitrous oxide above _____ MAC is very pro emetic.
half
What can volatile anesthetics cause in relation to B12?
Deficiency that inhibits DNA synthesis
What is a potential effect of volatile anesthetics on plasma homocysteine levels?
Increased levels associated with ischemic events
What is the effect of volatile anesthetics on uterine smooth muscle contractility?
Decreased contractility
What is halothane known for in the context of volatile anesthetics?
It is the historical benchmark for comparison
What is a significant downside of halothane as an anesthetic?
Higher solubility leading to slower induction and wake-up
What is isoflurane known for in patient experience?
Very pungent, causing coughing and gasping
True or False: Isoflurane is inexpensive to produce.
False
What is ISOFLURANE?
An isoflurane volatile anesthetic that is pungent and can cause coughing and gasping when inhaled.
ISOFLURANE is known for being expensive and resistant to metabolism.
What are the advantages of ISOFLURANE over Halothane?
It does not cause hepatic and renal toxicity, and it is very stable over time.
Halothane was known to have significant organ toxicity.
What is a notable characteristic of Dust Fluorine?
It has very low solubility, allowing it to quickly move from blood to brain or fat.
This characteristic is beneficial for rapid anesthetic effects.
What type of vaporizer is required for Dust Fluorine?
A special heated vaporizer due to its vapor pressure being close to atmospheric pressure.
This was necessary to maintain proper delivery of the anesthetic.
What is a common issue when using volatile anesthetics?
Coughing, choking, and laryngeal spasms can occur due to their pungency.
This can lead to loss of airway if not managed properly.
What can happen if absorbent material in anesthesia equipment is dehydrated?
It can lead to the formation of carbon monoxide.
This is a dangerous situation that can arise from improper management of equipment.
What is SEMO fluorine known for?
It has low solubility and is less pungent than other volatile anesthetics.
This makes it a safer option for patients during anesthesia.
Why is SEVOFLURANE preferred for neuro patients?
It causes the least cerebral vasodilation.
This is crucial for patients with increased intracranial pressure.
What is the MAC of nitrous oxide?
104.
MAC stands for Minimum Alveolar Concentration, which indicates the potency of an anesthetic.
Why can nitrous oxide not be used as the sole anesthetic?
Because it cannot exceed a 100% total of partial pressures, limiting its effectiveness alone.
It is always used as a supplement to other anesthetics.
What is the second gas effect in relation to nitrous oxide?
It enhances the inhalation of other anesthetics by increasing their concentration in the pulmonary capillaries.
This effect speeds up the induction of anesthesia.
What are negative effects associated with nitrous oxide?
Nausea and vomiting, especially in pediatric patients.
It also increases pulmonary vascular resistance, making it unsuitable for neonates.
What should students do according to the lecture?
Start looking at videos and review the syllabus for guidance on study materials.
The syllabus provides valuable resources for exam preparation.
What are the positive effects of nitrous oxide?
Good analgesia, 2nd gas effect
Nitrous oxide is often used for its analgesic properties and in combination with other anesthetics.
What are the negative effects of nitrous oxide?
Nausea/vomiting > 50%, ↑ PVR, may increase right-to-left shunt in neonates, jeopardize arterial oxygenation
These effects can complicate its use, especially in vulnerable populations.
What is the solubility and potency of nitrous oxide?
Low solubility, low potency
Nitrous oxide cannot produce skeletal muscle relaxation and cannot deliver 1 MAC.
What is the cardiovascular effect of nitrous oxide?
No cardiac depression
Nitrous oxide has minimal effects on heart rate and contractility compared to other anesthetics.
What happens to cardiac output with volatiles?
Dose dependent decrease in CO, offset by mild increase in HR
This is particularly relevant for modern volatile anesthetics.
What is the impact of nitrous oxide on the immune system?
Suppression of monocytes, macrophages, and T-cells
There is some evidence that general anesthesia may increase metastasis and mortality.
What is hypoxic pulmonary vasoconstriction?
Normal contraction of pulmonary artery smooth muscle to divert blood flow
This mechanism is vital during one-lung ventilation.
How does nitrous oxide affect the carbon dioxide response curve?
Blunts hypoxic response and hypercarbic response
This occurs at various MAC levels and can affect postoperative ventilation.
What is the renal effect of inhalational anesthetics?
Dose dependent decrease in RBF, GFR, and U/O
Preoperative hydration can mitigate these effects.
What are the metabolic effects of nitrous oxide?
B12 deficiency, inhibits methionine synthase
This can lead to megaloblastic anemia and increased plasma homocysteine levels.
What are the obstetric effects of inhalational anesthetics?
Dose-dependent decrease in uterine smooth muscle contractility
This can be useful in certain obstetric situations but may worsen uterine atony.
What is the main concern with halothane?
Catecholamine-induced arrhythmias and hepatic necrosis
Halothane has significant risks, particularly in pediatric patients.
What is sevoflurane known for?
Low solubility, least airway irritation of modern volatiles
It is commonly used due to its favorable properties.
What is the characteristic of desflurane?
Most pungent, requires special vaporizer
Desflurane can cause coughing and laryngospasm at higher concentrations.
True or False: Nitrous oxide has a skeletal muscle relaxant effect.
False
Nitrous oxide does not produce relaxation of skeletal muscles.
What is the effect of volatile anesthetics on cerebral blood flow?
Dose-dependent increase in CBF due to decreased cerebral vascular resistance
This can lead to increased ICP in certain patients.
What are the symptoms of malignant hyperthermia?
Muscle rigidity, ↑ body temperature, ↑ CO2 production
It can be triggered by all volatile agents and succinylcholine.
What is the effect of inhalation anesthesia on CMRO2?
Dose dependent decrease in CMRO2 and cerebral activity
Begins around 0.4 MAC, leading to unconsciousness.
What are the risks associated with sevoflurane?
Formation of Compound A, reacts with desiccated absorbent
This reaction can lead to nephrotoxicity and spontaneous combustion.
What is the role of adenosine in ischemic preconditioning?
Mediates increased protein kinase C activity
This helps to better regulate vascular tone and prevent reperfusion injury.
Fill in the blank: Nitrous oxide oxidizes the cobalt ion in _______.
B12
This action inhibits methionine synthase and DNA synthesis.
What is the most common metabolic consequence of nitrous oxide?
Megaloblastic bone marrow suppression
This can occur after 24 hours of exposure to nitrous oxide.
