Chapter 7 Flashcards
Who gave the first public demonstration of general anesthesia at Mass Gen?
William T.G. Morton on October 16, 1846
What are the “A”s of anesthesia?
Amnesia Anesthesia Analgesia Akinesia Areflexia Anxiolysis
Amnesia
Inability to form memories
Anesthesia
Lack of sensation
Analgesia
Relief/lack of perception of pain
Akinesia
Lack of movement in response to surgical stimulus
Areflexia
Blunting of autonomic reflexes- attenuation of reflexic hemodynamic responses to surgical stimulus
Anxiolysis
Decrease in procedure-related anxiety
What does the preoperative assessment include?
Detailed hx
PE
Review of pertinent data and studies
What are the advantages of a preoperative assessment?
Allows further studies to be performed, if indicated
Allows interventions to take place so that the pt may be “optimized”
What is the goal of the preoperative assessment?
Summarize the pt’s status to formulate an anesthetic plan
Which active cardiac conditions should be evaluated and treated before noncardiac surgery?
Decompensated heart failure
Severe valvular disease
Significant arrhythmias
Unstable coronary syndromes
What procedures are considered to have elevated cardiac risk?
Aortic and other major vascular Peripheral vascular Anticipated prolonged surgical procedures associated with large fluid shifts and/or blood loss Carotid endarterectomy Head and neck Intraperitoneal and intrathoracic Orthopedic Prostate
What procedures have a low cardiac risk?
Cataract
Plastic surgery
What are five clinical predictors of cardiac risk independent of the surgical procedure?
Ischemic heart dz Hx of heart failure Cerebrovascular dz Diabetes mellitus Renal insufficiency
When is perioperative cardiac morbidity increased?
In those unable to achieve four METs
What is more predictive of perioperative outcomes than spirometry?
Clinical findings and pt exercise capability
In evaluation of the pulmonary system, what diseases should be inquired about?
Reactive airway dz COPD Tobacco use Oxygen requirement Obstructive sleep apnea sx Recent upper respiratory tract infections
Who is at increased risk of pulmonary complications?
FEV1 <70%
When is the highest likelihood of gastric aspiration?
Induction
Emergence
When is aspiration more likely during the maintenance phase of anesthesia?
If the airway is not protected intraoperatively with an ET tube
What must be in place during heavy sedation?
ET tube
What are specific risk factors for aspiration during surgery and anesthesia?
Recent ingestion of food (<8 hrs for heavy meals, <6 h for light solid food, <2 h for clear liquids) Trauma Gi dysfunction Increased intra-abdominal pressure Use of opioids
When does the ACC/AHA recommend continuing beta blockers?
HTN
Angina
Symptomatic arrhythmias
When does the ACC/AHA recommend starting beta blockers?
Those undergoing vascular surgery who were found to have ischemia on preoperative testing
What does LEMON stand for?
Look externally Evaluate the 3-3-2 rule Mallampati Obstruction Neck mobility
What in the look externally part of LEMON would make for a more difficult intubation?
Known face or neck pathology Abnormal face shape Sunken cheeks Receding mandible Narrow mouth
In the 3-3-2 rule, what would make for a more difficult intubation?
Mouth opening <3 fingers
Hyoid-chin distance <3 fingers
Thyroid cartilage-mouth floor distance <2 fingers
What obstruction can cause a difficult airway?
Pathology within and/or around the upper airways (e.g., epiglottis, abscess, etc.)
What are predictors of difficulty with ventilation?
Obesity Presence of beard Edentulousness Presence of OSA sx Advanced age
Possible effects of diuretics on anesthetic course during surgery
Hypovolemia and hypotension
Electrolyte abnormalities and ECG changes
Possible effects of ACE inhibitors, certain aniarrhythmics on anesthetic course during surgery
Refractory vasodilation and hypotension
Possible effects of antiplatelet agents, anticoagulant agents on anesthetic course during surgery
Possible increased blood loss
Increased risk of epidural hematoma formation on epidural catheter placement or removal
Possible effects of insulin, oral hypoglycemics on anesthetic course during surgery
Hypoglycemia, altered level of consciousness
What are the possible effects of MAO inhibitors on anesthetic course during surgery?
Life-threatening HTN or hyperthermia when used with sympathomimetics or meperidine
Clinical indicators for ordering an EKG
Age 50 or older Significant cardiocirculatory dz, current or past DM (age 40 or older) Renal dz Other major metabolic dz Procedure level 5
Clinical indicators for CXR
Asthma or COPD that is debilitating or with change of sx or acute episode within past 6 mos
Cardiothoracic procedure
Procedure level 5
Clinical indicators for serum chemistries
Renal dz Adrenal or thyroid disorders Diuretic therapy Chemo Procedure level 5
Clinical indicators for UA
DM Renal dz Genitourologic procedure Recent GU infection Metabolic d/o involving renal function Procedure level 5
Clinical indicators for CBC
Hematologic d/o
Vascular procedure
Chemo
Procedure level 4
Clinical indicators for coagulation studies
Anticoagulation therapy
Vascular procedure
Procedure level 5
Clinical indicators for pregnancy test
Pts for whom pregnancy might complicate the surgery
Pts of uncertain status by hx
Definition of procedure 4
Highly invasive procedure with blood loss >1500 mL
Includes major ortho surgery, reconstruction of the GI tract, and vascular repair without an ICU stay
Definition of procedure 5
Similar to procedure 4 except with ICU stay with invasive monitoring
What are the standard intraoperative monitors for virtually all anesthetics?
Pulse oximeter Noninvasive BP monitoring ECG Temp monitor A means of assessing adequacy of ventilation, usually with an end-tidal CO2 monitor
What is the gold standard to monitor endotracheal intubation?
EtCO2
EtCO2 is how much below arterial CO2?
5-6 mm Hg
An increase in the gap of CO2 between the lungs and arteries in the extreme occurs during what two events?
PE
Cardiac arrest
What can be detected by a delayed upstroke of the EtCO2 tracing?
An obstruction to expiration, such as bronchospasm
Which nerve is usually tested in peripheral nerve stimulation when paralytic agents are used?
Ulnar
What is the purpose of the intra-arterial catheter?
Helpful for frequent blood gas and electrolyte monitoring
What is the purpose of the central venous pressure monitor?
Surrogate of the Left Ventricular End Diastolic Pressure to monitor intravascular volume
What is the purpose of the pulmonary artery catheter
More accurate measurement of LVED volume
In addition to anesthesia, what else occurs during the induction phase?
Pt is prexoygenated, or denitrogenated, with 100% oxygen delivered from a face mask with as tight of a seal as possible
What is the goal of preoxygenation?
Bring the end-tidal concentration of oxygen >80% with an SaO2 of 100%
What is the MOA of most IV agents?
Facilitate GABA pathways in the brain?
What are some examples of IV agents?
Barbiturates Propofol Etomidate Ketamine Benzos
What is the most common induction agent currently used in the US?
Propofol
When should propofol be used with caution?
Pts with low cardiac reserve
What is an additional benefit of propofol?
Antiemetic properties
When should etomidate be used?
In pts with compromised hemodynamics
What is a side effect of etomidate?
Can suppress adrenal hormone synthesis for up to 5-6 hrs
What are benzos usually combined with?
Opiods
Why do benzos need to be used in combination with something else?
They have no analgesic properties
What is the predominant benzodiazepine used?
Midazolam
How can overdose of benzos be treated?
Flumazenil
MOA of ketamine
Inhibits thalamocortical pathways and activation of the limbic system
When should ketamine be used?
Induction of anesthesia in pts who must maintain spontaneous breathing, pts with reactive airway dz
Can be used as an adjunct in pts with chronic pain
When is ketamine undesirable?
Relatively contraindicated?
Head injury and/or elevations in ICP
Coronary artery dz or uncontrolled HTN
What can be used to decrease the complications of dysphoria and hallucinations in ketamine?
Benzos
When are opioids ideal adjuncts?
For pts with compromised cardiac function undergoing cardiac surgery
MOA of opioids
Interact with opioid receptors in the CNS and mediate effects on pain, mood, respiration, circulation and bowel and bladder function
What are the side effects of opioids?
Direct dose-dependent depression of ventilation
Slowed peristalsis and delayed gastric emptying
N/V
Constipation
Urinary retention
Morphine and meperidine- histamine release, causing flushing and hypotension
What is the standard measure of potency for inhaled anesthetics?
The minimum alveolar concentration (MAC) of a given gas at 1 atmosphere that produces immobility in 50% of subjects exposed to a noxious stimulus
What are the inhalational agents commonly used today?
Isoflurane
Sevoflurane
Desflurane
Which inhalational agent is the most insoluble agent in the blood, thereby allowing a very quick onset and offset of anesthesia?
Desflurane
However, it is relatively unsuitable for mask inductions
What do volatile anesthetics cause?
Dose-dependent cardiac depression Decreases in systemic, pulmonary, and venous vascular resistance Respiratory depression Bronchodilation Decreases in CMRO2 Increases in ICP
When is sevoflurane use ideal?
Mask induction, especially in peds or in pts without IV agents
Use of nitrous oxide
Used only as an adjuvant anesthetic at relatively high inspired concentrations
When is nitrous oxide contraindicated?
Pneumo
Small bowel obstruction
Air embolism
Middle ear surgery
What are the two major classes of NMB agents?
Depolarizing and
Nondepolarizing agents
What is the only depolarizing agent used in the US?
Succinylcholine
What are the major advantages of succinylcholine?
Rapid onset
provisiono f reliable intubating conditions in 60 secs
Duration of action of 3-5 mins
What are the adverse effects of succinylcholine?
Release of potassium from muscle- could lead to life-threatening hyperkalemia
Malignant hyperthermia
What pts are susceptible to life-threatening hyperkalemia d/t succinylcholine use?
Pts with extensive burns
Massive tissue injuries
Neurologic injuries
Neuromuscular d/os
What are relative contraindications to succinylcholine?
Pts with intracranial HTN or open orbital injuries
Children
What is used to maintain fluids?
Isotonic crystalloids administered at approximately 2 mL/kg/hr
How is blood loss replaced?
Crystalloid or colloids until transfusion is necessary
How should nondepolarizing NMB agents be reversed?
Acetylcholinesterase inhibitors
What else should be given to reverse nondepolarizng NMB agents?
Anticholinergics, otherwise reversal will result in severe bradycardia and possible asystole
What must a pt be able to do before extubation?
Breathe on their own
Follow commands
Demonstrate purposeful movements
Protect their airway
What are objective criteria for extubation?
Resonable RR (>8 and <30)
Adequate tidal volume (<5 mL/kg)
PaCO2 <50 mm Hg
Hemodynamic stability
When does neuraxial anesthesia result in higher rates of graft viability?
Peripheral revascularization
Decreased intraoperative blood loss
Lower rate of DVT for hip surgery
What are some systemic implications of neuraxial anesthesia?
Bradycardia Hypotension Mental status changes Postdural HA Epidural hematoma, more likely in pts with increased ICP
How to treat hypotension as a result of neuraxial anesthesia
Fluid administration
Vasoconstrictors
Inotropic agents
How to treat bradycardia as a result of neuraxial anesthesia
Anticholinergics
How to treat postdural puncture HA
Bed rest
IV hydration
Caffeine
If conservative measures fail, epidural blood patch
What are two infectious complications of neuraxial anesthesia?
Epidural abscess
Meningitis
Sx of epidural hematoma
Backache
LE weakness or numbness
What must be continued prior to neuraxial anesthesia?
How long?
Why?
Ticlopidine- 2 wks prior
Clopidogrel- 1 wk prior
Increased risk of hematoma
Advantages of peripheral nerve blocks over neuraxial blocks
Greater neuraxial stability
Less risk of neurologic injury
Complications of peripheral nerve block
Hematoma
Block failure
Intravascular injection
Nerve damage
Possible complication of intercostal, interscalen, supra-or infraclavicular nerve block
Pneumo
Complication of interscalene block
Phrenic nerve paralysis
Relative contraindications to regional nerve blocks
Sepsis
Skin infection in area of proposed needle placement
Pre-existent neurologic deficit/neuropathy
