Obstetric Anesthesia Flashcards
Maternal weight gain is how many percent or how much kg?
17%
12 kg
The expected weight increase in the 1st trimester is?
How about each in the last two trimesters?
1-2 kg
5-6 kg
The hypertrophy results from?
Increase in size of cardiac myocytes rather than the size
How long will the hemodynamic changes return to prepregnancy values?
24 weeks
Compression of the IVC occur as early as?
13 to 16 weeks
During uterine contractions 300 to 500 mL of blood is displaced from the intervillous space through the relatively unimpeded ovarian venous outflow system. This term is referred to as?
Autotransfusion
Heart rate returns to prepregnancy levels after how long?
2 weeks postpartum
Capillary engorgement of the larynx and mucosa begins as early as?
1st trimester
FRC begins to decrease by what AOG?
5th AOG
Caused by elevation of the diaphragm
Maternal plasma volume increases as early as how many weeks AOG?
6
Until it reaches by 50% by 34 weeks
Clotting factors that are increased during pregnancy (6)
1 (fibrinogen) 7 (proconvertin) 8 (antihemophilic factor) 9 (Christmas factor) 10 (Stuart-power factor) 12 (hageman factor)
Unchanged factor concentrations (2)
2
5
Decreased factor concentrations (2)
11
13
The hgb concentration decrease during the first 3 postpartum days and increase during the next __ days?
3
Albumin returns to normal after how many weeks postpartum?
6
The coagulation profile returns to normal for how many weeks postpartum?
2 weeks
Stomach is rotated to the?
45 degrees to the R
Risk factors for GERD (3)
- Gestational age
- Prepregnancy GERD
- Multiparity
Prepregnancy BMI, gravidity, do not correlate
Maternal age has inverse correlation
Read
Gastric emptying is not changed during pregnancy
But esophageal peristalsis and intestinal transit are slowed
The GFR does not return to prepregnancy levels by how long postpartum?
3 months
What are among the earliest and most dramatic changes in pregnancy?
Renal hemodynamics
The protein to creatinine ratio of what value has been estimated as indicating significant proteinuria
0.18
Endocrine
Increase TBG, T3 & T4
Free T3 & free T4 is not increased
TSH decreases but returns to nonpregnant level
Fetal thyroid gland start to produce thyroid hormones until end of 1st trimester
Corticosteroid binding globulin doubles during pregnancy
Betamethasone clearance is greater since the drug is metabolized by placental enzymes
A paresthesia or sensory loss on the anterolateral thigh
Meralgia paresthetica
Cerebral flow increases in pregnancy due to? (2)
- Inc cerebrovascular resistance
2. Inc internal carotid artery diameter
Other 2 cerebral changes
- Inc BBB permeability inc hydrostatic P
2. Inc capillary permeability
Vertebral column changes
- Epidural fat & veins enlarge
2. Spinal csf vol reduced
Pregnant and postpartum exhibit enhanced sensitivity to what muscle relaxants? (2)
- Vecuronium
2. Rocuronium
Onset and duration of this drug is shorter in women immediately after delivery?
Cisatracurium
Magnesium sulfate side effects
10 meq/L?
15 meq/L
25 meq/L
Loss of DTR
Respiratory paralysis
Cardiac arrest
The oculocardiac reflex is triggered by pressure on the globe and by traction on the extraocular muscles as well as on the conjunctiva or on the orbital structures. This reflex, whose afferent limb is _______ and efferent limb is _______ .
Trigeminal
Vagal
Walls of orbit are composed of these Bones (7)
- Frontal
- Zygomatic
- Greater wing of sphenoid
- Maxilla
- Palatine
- Lacrimal
- Ethmoid
3 layers of the eye
Sclera
Uveal tract
Retina
What composes the uveal tract?
- Iris
- Ciliary body
- Choroid
The lacrimal duct drains to which turbinate?
Below the inferior turbinate
Average production of aqueous humor?
2 uL/min
IOP normal range
10 to 20 mmHg
Straining, vomiting or coughing increases IOP to what value?
40 mmHg
How much increase in IOP does succinylcholine make?
9 mmHg within 1 to 4 minutes
How long does the IOP return to baseline after giving succinylcholine?
7 minutes
Serious adverse cardiopulmonary responses (by melphalan drug) to cannulation of the ophthalmic artery or injection of the agent have been described.These responses are characterized by?
abrupt drop in end-tidal CO2
followed by markedly reduced lung compliance akin to acute bronchospasm, profound hypoxia, systemic hypotension, and bradycardia.
It has been postulated that superselective ophthalmic artery chemotherapy may trigger a trigeminal- afferent autonomic reflex response akin to the oculocardiac reflex. It has been referred to as?
trigeminocardiac reflex (TCR)
Analogous to the oculocardiac reflex, the TCR is often self-limited and is suppressed by removal of the stimulus, in this case, withdrawal of the catheter from the ophthalmic artery.
Also known as phospholine iodide, is a long-acting anticholinesterase miotic that lowers IOP by decreasing resistance to the outflow of aqueous humor.
Echothiophate
Any of the long-acting anticholinesterases may prolong the action of succinylcholine because, after at least 1 month of therapy, plasma pseudocholinesterase activity may be below 5% of normal. It is said, moreover, that normal enzyme activity does not return until 4 to 6 weeks after discontinuation of the drug.
The only local anesthetic that inherently produces vasoconstriction and shrinkage of mucous membranes, cocaine has been used in nasal packs during dacryocystorhinostomy. The drug is so well absorbed from mucosal surfaces that plasma concentrations are achieved that are comparable to those after direct intravenous injection.
What is the lethal dose?
Cocaine
1 g
If serious cardiovascular effects occur, what should be used to counteract them
Labetalol
a β1-blocker, is said to be more oculospecific and have minimal systemic effects.
Betaxolol
Propofol sedation for eye block is associated with?
Sneezing
Either of this 3 drugs given prior to propofol abate the sneeze reflex.
Midazolam
Fentanyl
Alfentanil
Has traditionally been the most popular regional
anesthetic technique for eye surgery.
Retrobulbar block
In this block, the needle tip is situated behind (retro) the globe (bulbar).
Retrobulbar block
Retrobulbar blocks are accomplished by directing a needle through the eyelid or via the conjunctiva toward the orbital apex with sufficient depth and angulation such that the needle passes through the muscle cone.
In this block, needle tip is placed around (peri) the globe (bulbar).
Peribulbar block
Thus, the peribulbar or, more properly termed, extraconal block is executed by directing a needle through the eyelid or via the conjunctiva to less depth and with minimal angulation, parallel to the globe, toward the greater wing of the sphenoid bone.
The four rectus muscles, along with connective tissue septae, create a defined compartment known as the, which extends from the rectus muscle origins around the optic foramen at the apex of the orbit to the attachment of the muscles onto the globe anteriorly?
Orbital cone
Read
This is important because intramuscular injection of anesthetics has been postulated as a potential cause of postoperative strabismus.
Supplementation of anesthesia with an injection above the globe may not be prudent because the preponderance of vessels lie in the superior orbit.
In addition, the belly of the superior oblique muscle and the trochlear muscle can be encountered superonasally.
Read
Katsev et al.84 demonstrated that the tips of commonly used 1.5-in (38- mm) needles can reach critical structures in the densely packed apex of the orbit in almost 20% of classic retrobulbar blocks. Consequently, needles 1.25 inches (31-mm) or shorter are appropriate.
Read dull or sharp needles?
Dull needles may require more force to penetrate the globe. However, sharp needles are less painful to insert and may cause less damage in the face of inadvertent globe puncture.
Akinesia of the eyelids is obtained by blocking the branches of the what nerve supplying the orbicularis muscle.
Facial
Lid akinesia is often a direct consequence of the larger volume of local anesthetic used for extraconal blocks. Intraconal blocks, in contrast, often leave the orbicularis oculi fully functional.
What facial nerve block technique approach can potentially produce the most serious systemic consequences
Nadbath– Rehman approach
With this approach, a 27-gauge, 12-mm needle is inserted between the mastoid process and the posterior border of the mandibular ramus.
The Nadbath-Rheman approach, because of the proximity of the jugular foramen (10 mm medial to the stylomastoid foramen) to the injection site, ipsilateral paralysis of cranial nerves _, _, _ can occur, producing hoarseness, dysphagia, pooling of secretions, agitation, respiratory distress, or laryngospasm.
9
10
11
the Nadbath–Rehman block produces complete hemifacial akinesia, which interferes with oral intake, this approach is not recommended for outpatients.
Read
Globe puncture is defined as a single entry into the eye, whereas perforation is caused by two full-thickness wounds—an entry and a subsequent exit.
Where is the most commonly penetrated area?
Globe’s posterior pole
An axial length greater than how much (mm) confers greater risk of penetration or perforation.
26 mm
This enzyme has been the most popular ancillary agent used to modify ocular local anesthetic actions. It increases tissue permeability, serves to promote dispersion of local anesthetics through tissues within the orbit, reduces the increase in orbital pressure associated with the volume of injected anesthetics, and enhances the quality of orbital blockade.
Hyaluronidase
Vitrectomy is generally considered to be a low-risk procedure; however, in
recent years, both the anesthesiology and ophthalmology literature have reported cases of sudden death during retina surgery. The presumed etiology is?
Venous air embolism
From air introduced into the choroid blood flow via a malpositioned infusion cannula.
In addition to the well-known propensity of strabismus surgery to trigger the oculocardiac reflex (previously discussed), strabismus or ptosis patients are thought to have an increased incidence of?
Malignant hyperthermia
This laser emits blue-green light with a wavelength of approximately 488 to 515 nm (approximately 0.5 μm). This laser has low maximum power and is easily transmitted by fiberoptic bundles. Light from the this laser is strongly absorbed by hemoglobin, melanin, and other pigments, rendering it useful in retinal detachment surgery to photocoagulate or cauterize pigment epithelium and the adjacent neurosensory retina.
What color of goggles should be worn?
Argon laser
Orange
This laser emits light in the infrared range (wavelength 1,064 nm [1.06 μm]) and is useful in posterior lens capsule surgery. The Nd:YAG laser has high-power density and is efficacious in creating an opening in opacified posterior capsule membranes.
What color of goggles should be worn?
Nd:YAG
Green
Is a form of high-power, ultraviolet chemical laser frequently used in the delicate refractive surgery commonly referred to as laser corrective surgery or LASIK. This laser generally uses a combination of inert gas (argon, krypton, or xenon) and a reactive gas (fluorine or chlorine). This property allows removal of exceptionally fine layers of surface material with almost no heating or change to neighboring tissue.
excimer laser (sometimes, and more correctly, called an exciplex laser) short for excited complex
What is the most common ocular complication of general anesthesia?
Corneal abrasion
Retinal hemorrhages that occur in otherwise healthy people secondary to hemodynamic changes associated with turbulent emergence from anesthesia or protracted vomiting are termed?
Valsalva retinopathy
Funduscopic examination shows cotton–wool exudates, and this condition is known as?
Purtscher retinopathy
If external pressure is applied to the globe from improper head support, perfusion pressure to the eye is likely to be reduced. An episode of systemic hypotension in this setting could further decrease perfusion pressure and thereby decrease intraocular blood flow, resulting in?
Retinal ischemia
This condition, in the nonsurgical setting is the most common cause of sudden visual loss in patients older than 50 years.
Ischemic optic meuropathy
Conditions that augment oculocardiac reflex (2)
- Hypercarbia
2. Hypoxemia
In order for preventive analgesia to be successful, three critical principles must be adhered to:
- The depth of analgesia must be adequate enough to block all nociceptive input during surgery
- The analgesic technique must be extensive enough to include the entire surgical field
- The duration of analgesia must include both the surgical and postsurgical periods.
Is the normal, predicted, physiologic response to an adverse chemical, thermal, or mechanical stimulus.
Acute pain
Generally, acute pain resolves within 1 month.
Acute pain–induced change in the central nervous system is known as?
Neural plasticity
This can cause sensitization of the nervous system, resulting in ALLODYNIA and HYPERALGESIA.
Are free nerve endings located in skin, muscle, bone, and connective tissue with cell bodies located in the dorsal root ganglia.
Nociceptors
The first-order neurons that make up the dual ascending system have their origins in the periphery as A-δ and polymodal C fibers.
These fibers transmit “first pain,” which is described as sharp or stinging in nature and is well localized.
These fibers transmit “second pain,” which is more diffuse in nature and is associated with the affective and motivational aspects of pain.
A-δ fibers
Polymodal C fibers
These are located primarily in lamina I, respond only to noxious stimuli, and are thought to be involved in the sensory-discriminative aspects of pain.
Nociceptive-specific neurons
These are predominately located in laminae IV, V, and VI, respond to both nonnoxious and noxious input, and are involved with the affective– motivational component of pain.
wide dynamic-range (WDR) neurons
Axons of both nociceptive-specific and WDR neurons ascend the spinal cord via 2 structures
- dorsal column–medial lemniscus
2. anterior lateral spinothalamic tract
Tissue injury tends to fuel neuroplastic changes within the nervous system, which results in both peripheral and central sensitization. Clinically this can manifest as (2)
- hyperalgesia, which is defined as an exaggerated pain response to a normally painful stimulus, and
- allodynia, which is defined as a painful response to a typically nonpainful stimulus
The four elements of pain processing include?
(1) transduction
(2) transmission
(3) modulation
(4) perception
Is the event whereby noxious thermal, chemical, or mechanical stimuli are converted into an action potential.
Transduction
Modulation of pain transmission involves altering afferent neural transmission along the pain pathway.
Is the most common site for modulation of the pain pathway, and modulation can involve either inhibition or augmentation of the pain signals.
Dorsal horn
Inhibitory neurotransmitters (2)
- GABA
2. Glycine
Three classes of transmitter compounds integral to pain transmission include
- the excitatory amino acids glutamate and aspartate
- the excitatory neuropeptides substance P and neurokinin A
- inhibitory amino acids glycine and GABA
These 2 receptors which are sodium channel dependent, are essential for fast synaptic afferent input.
AMPA
Kainate
This receptor is only activated following prolonged depolarization of the cell membrane. Release of substance P into the spinal cord will remove the magnesium block on the channel of the NMDA receptor, giving glutamate free access to the NMDA receptor.
NMDA
The goal of preventive analgesia is?
To block the development of sustained pain.
Surgical procedures that are a relatively high risk for neuropathic pain include limb amputations, breast surgery, gallbladder surgery, thoracic surgery, and inguinal hernia repair.
NOCICEPTIVE pain responds best to opioids, nonsteroidal anti- inflammatory drugs (NSAIDs), para-aminophenol agents, and regional anesthesia techniques.
Neuropathic pain, on the other hand, may benefit from the addition of the nonopioid analgesic adjuvants such as the NMDA receptor antagonists, α2-agonists, and the α2–δ subunit calcium channel ligands, which will be discussed in detail.
This drug is the most widely prescribed opioid analgesic in the United States. It has weak affinity for the μ receptor; however, demethylation by the CYP2D6 enzyme converts hydrocodone into hydromorphone, which has stronger μ receptor
Hydrocodone
Is another commonly prescribed semisynthetic opioid analgesic that is used for the treatment of both acute and chronic pain. The drug is predominantly metabolized by CYP3A4
Oxycodone
Pain that is persistent but may vary over time
Background pain
This is are the mainstay for the treatment of acute postoperative pain, while this other drug is the gold standard.
Opioid
Morphine
Of all of the adverse effects what has the greates effect on postoperative length of hospital stay.
Opioid-induced constipation
Of all the side effects the most serious is?
Respiratory deoression
Is an active metabolite of morphine and is thought to be responsible for most of the analgesia associated with chronic dosing of the drug.
Morphine-6-glucuronide
This drug is a prodrug that is devoid of analgesic activity and requires metabolic conversion by the CYP2D6 enzyme into morphine, which has a 200-fold greater affinity for the μ-opioid receptor than the parent drug codeine.
Codeine
In poor metabolizers and ultrarapid metabolizers codeine is contraindicated because of lack of efficacy in the former and the potential for toxicity in the latter
