OBGYN Flashcards
(153 cards)
Risk factors for aspiration during pregnancy include:
Risk factors for aspiration during pregnancy include:
* Weakened lower esophageal sphincter tone; increased progesterone levels can weaken lower esophageal sphincter tone and increase the risk of gastroesophageal reflux in pregnant patients.
* Increased incidence of difficult airway due to swelling, airway mucosal friability, and weight gain
* Gastrointestinal system anatomical alterations due to enlarged uterus resulting in increased abdominal pressure and upward displacement
What gastrointestinal changes occur in pregnancy women after 20 weeks gestation?
Stomach and pylorus are moved cephalad, and intraabdominal esophagus becomes intrathoracic (increases gastric pressure and decreases competence of LES)
Decreased LES tone (estrogen, progesterone)
More acidic gastric fluid (placenta secretes gastrin)
All together, these changes lead to a greater propensity for gastric reflux and heartburn in pregnant women with a large, gravid uterus.
According to the current guidelines from the ASA, uncomplicated laboring women may consume..
According to the current guidelines from the ASA, uncomplicated laboring women may consume a moderate amount of clear liquids.
NOTE:
Complicated patients excluded from these restrictions include those with diabetes, morbid obesity, difficult airway, or increased risk of operative delivery.
ASA recommends avoiding solid foods in laboring patients and fasting for 6-8 hours in those undergoing elective CS.
According to the current guidelines from the ASA, uncomplicated patients scheduled for an elective cesarean section may consume..
According to the current guidelines from the ASA, uncomplicated patients scheduled for an elective cesarean section may consume clear liquids up to two hours prior to induction of anesthesia.
NOTE:
Complicated patients excluded from these restrictions include those with diabetes, morbid obesity, difficult airway, or increased risk of operative delivery.
ASA recommends avoiding solid foods in laboring patients and fasting for 6-8 hours in those undergoing elective CS.
Why do pregnant women have decreased oxygen reserve compared to average adults?
Many respiratory changes occur in the obstetric patient due to both anatomic and hormonal alterations.
As the pregnancy progresses, the diaphragm moves more cephalad which causes a decrease in the functional residual capacity.
In order to compensate for this change, the thoracic rib cage increases in anteroposterior and transverse diameter which aids to cause only a slight decrease in the total lung capacity overall.
The functional residual capacity decreases by about 20-30% as does the expiratory reserve volume and residual volume. In addition, there is an increase in the inspiratory reserve volume.
Airway resistance remains unchanged as progesterone relaxes the bronchiolar smooth muscle which combats the increased airway resistance due to upper airway edema.
These changes contribute to a rapid desaturation during apnea and necessitate prompt airway intervention to avoid complications.
Risk factors for preterm labor (<37 week)?
Risk factors for preterm labor (<37 week):
Previous preterm delivery
Extremes of age (<18, >35)
Race (black)
Low BMI
Short cervix
Multiple gestations (eg twins)
Tobacco/substance abuse
Justification for general vs. neuraxial anesthesia?
The choice of which type of anesthesia is administered for cesarean delivery (CD) depends on the urgency and patient factors, but, ultimately, experience and clinical judgment should always be used. When there is currently an epidural in place (whether it be an epidural alone, combined spinal anesthesia and epidural, or a dural puncture epidural), the epidural can be used for the CD.
If the patient does not have an epidural, the following questions must be answered:
* Does the patient require immediate delivery for maternal and/or fetal health?
* Is massive hemorrhage expected?
* Are there any contraindications to neuraxial anesthesia?
If the answer is “yes” to any of these questions, general anesthesia should be performed.
If the answer is “no” to all of these questions, the following questions must be answered:
* Is the duration of CD > 1.5 hours, or are multiple procedures planned?
* Does the patient have abdominal surgeries or previous CD (uterine scar)?
* Does the patient have risk factors that increase the risk of a poor outcome with general anesthesia (severe obesity, difficult airway, or history of malignant hyperthermia)?
If the answer is “yes” to any of these questions, an epidural can be placed and used for the CD. If the answer is “no” to all of these questions, spinal anesthesia can be performed.
Indications for general anesthesia for CS include
Immediate delivery for fetal or maternal concerns WITHOUT an epidural already in place
Severe hypovolemia or coagulopathy
Surgery involving massive hemorrhage
Intracranial or spinal conditions that preclude neuraxial
Patient refusal of neuraxial anesthesia
NOTE:
General anesthesia is generally avoided due to increased difficult airway risk, adverse risks to the fetus, uterine relaxation from volatile anesthetics, and risk of intraoperative awareness.
Factors that can affect the block height during spinal anesthesia include:
Factors that can affect the block height during spinal anesthesia include:
-Baricity (most important factor for the spread of local anesthetic and the level of block)
- Medication (dose and baricity)
- Patient (cerebrospinal fluid volume, older age, and pregnancy),
- Procedure (patient position, epidural injection before or after spinal injection) factors.
Mechanism by which epidurals reduce risk of postoperative ileus?
Epidurals containing a local anesthetic (with or without opioid) for postoperative analgesia reduces risk of postoperative ileus.
The proposed mechanism is increased gastrointestinal peristalsis (Sympatholytic) and reduced overall opioid use.
The increased gastrointestinal motility is thought to come from regional blockade of sympathetic nervous system (sympathectomy) and the epidural leaving the parasympathetic nervous system innervation of the gastrointestinal tract unopposed.
NOTE:
Single dose neuraxial opioids do not offer sympathectomy and are not superior to epidurals in regards to risk of post-op ileus.
Rank the following in terms of analgesic effectiveness:
Nurse administed medication (PRN)
Patient Controlled Epidural Analgesia (PCEA)
Continuous Epidural Infusion (CEI)
Patient Controlled Analgesia (PCA)
Rank the following in terms of analgesic effectiveness:
1 Continuous Epidural Infusion (CEI)
2 Patient Controlled Epidural Analgesia (PCEA)
3 Patient Controlled Analgesia (PCA)
4 Nurse administed medication (PRN)
What is more effective for pain relief, local based or opioid base epidurals?
Local based epidural
Epidural administration of any anesthetic agent including local anesthetics and opioids has been shown to produce superior analgesia to the same medications administered systemically, regardless of the type of surgery being performed. The proposed mechanism for this significantly improved pain control involves the direct effect of administration on nociceptive inputs into the central nervous system.
The use of a local anesthetic based epidural regimen has been shown to provide the best postoperative pain control. Opioid-based epidural analgesics provide superior pain control to systemic opioid-based analgesic regimens, though they are inferior to a local anesthetic based epidural regimen. The hydrophilicity of opioids plays a role in this superior pain control, with epidural administration of hydrophilic opioids generally equating an equianalgesic dosing of systemic hydrophilic opioids. Therefore, some suggest only using lipophilic opioids such as fentanyl in the epidural space for immediate postoperative pain control.
The use of opioids in combination with local anesthetics in epidural analgesia may be beneficial, however, definitive data on this point are lacking.
Furthermore, patient-controlled epidural analgesia (PCEA) has been shown to be inferior to continuous epidural infusions (CEI) of analgesic medications. Proposed mechanisms for this finding include the delayed action of local anesthetics in the epidural space, as well as benefits of a continual bathing of the pertinent nerve roots in CEI when compared to the intermittent coverage provided by PCEA. CEI may have increased incidences of medication-related side effects secondary to the increased amounts of medication administered in CEI compared to PCEA, and the benefits of CEI should be weighed against these possible complications. In clinical practice, many choose an epidural regimen that combines both CEI and PCEA.
The acid-base status of an otherwise healthy parturient is ________________.
The acid-base status of an otherwise healthy parturient is respiratory alkalosis with metabolic compensation.
Due to the effects of progesterone during pregnancy, maternal tidal volume increases by 50%, while respiratory rate remains mostly the same. The increased tidal volume increases minute ventilation with the levels of partial pressure of carbon dioxide in the arterial blood ranging from 27 to 32 mmHg in full-term parturients.
The respiratory alkalosis of pregnancy is compensated for by increased renal excretion of bicarbonate, and these combined physiologic changes result in a pH of approximately 7.44 to 7.46.
The changes in tidal volumes during pregnancy affect ventilation, oxygenation, and anesthesia management. The increased minute ventilation increases maternal oxygenation and causes a high-normal or slightly increased partial pressure of oxygen in the arterial blood. However, the decreased functional residual capacity and residual volume that also occur as the uterus expands during pregnancy render pregnant women more susceptible to hypoxemia in the supine or lithotomy position and during the induction of general anesthesia.
Additionally, the increase in tidal volume with the subsequent decrease in functional residual capacity and residual volume allows quicker equilibration of volatile anesthetics.
Describe the challenges with intubation of pregnant women.
The upper airway in pregnant patients becomes friable due to capillary engorgement. Edema of the oropharynx, larynx, and trachea begins to occur in the first trimester. Thus, when the airway is manipulated, there is an increased risk of bleeding. Because of this edema, mask ventilation, laryngoscopy, and intubation are more difficult. In addition, upon extubation, the edema can compromise the airway, leading to obstruction. Repeated attempts at laryngoscopy should be minimized, and a small diameter endotracheal tube (6-7-mm internal diameter) should be used.
The decreased FRC and RV that also occur as the uterus expands during pregnancy render pregnant women more susceptible to hypoxemia in the supine or lithotomy position and during the induction of general anesthesia.
Describe the changes that occur to minute ventilation in a pregnant woman?
To meet the increased metabolic demands during pregnancy, a woman’s minute ventilation increases throughout pregnancy to approximately 145% of normal nonpregnant minute ventilation. This effect is primarily due to increased tidal volume (from 450 to 600), with a small contribution from increased respiratory rate by 1-2 breaths/min). It is driven by the respiratory stimulant effects of progesterone, which shifts the carbon dioxide–ventilatory response curve to the left. Respiratory alkalosis occurs as the arterial partial pressure of carbon dioxide (PaCO2) is decreased by ∼ 10 mm Hg (from 40 to 30 mm Hg) by the end of the first trimester.
The respiratory rate then remains relatively constant for the remainder of the pregnancy. Despite respiratory alkalosis, the pH remains normal to only slightly elevated (7.40-7.44) due to compensatory metabolic acidosis. Serum bicarbonate (HCO3-) decreases to 20-21 mEq/L, and the serum base excess falls by 2-3 mEq/L. The increased minute ventilation improves alveolar ventilation, leading to an increase in PaO2. This increase is also due to the decrease in PaCO2 and a lower arteriovenous oxygen difference (which decreases the effect of venous admixture on PaO2).
MORE:
The increased progesterone during pregnancy leads to an increase in minute ventilation (as much as 50% at term), tidal volume (30%-50%), and respiratory rate (0%-15%). One to three weeks after pregnancy, ventilation returns to the nonpregnant levels.
Does closing capacity change during pregnancy?
NO, CC remains unchanged. However, FRC can fall below CC resulting in atelectasis and hypoxemia.
How does minute ventilation change during pregnancy?
Minute ventilation increases primarily due to large TVs and to a lesser extent higher RR.
The oxyhemoglobin dissociation curve shifts to the ______ during normal pregnancy.
The oxyhemoglobin dissociation curve shifts to the right during normal pregnancy (increased p50), allowing a greater volume of oxygen to be unloaded to the tissues (fetus) at a given arterial oxygen pressure.
TrueLearn Insight: The P50 of maternal hemoglobin during pregnancy increases from 26.8 mm Hg in the prepregnant state, to 30 mm Hg. This results in a rightward shift of the maternal oxyhemoglobin dissociation curve. The fetal oxyhemoglobin dissociation curve sits to the left of the normal adult and maternal dissociation curves. The P50 of fetal hemoglobin is 19-21 mm Hg. The increase in this gradient between P50 values of the mother and fetus facilitates oxygen unloading from maternal hemoglobin to fetal hemoglobin.
The normal FHR range is _____-______ bpm.
The normal FHR range is 110-160 bpm.
The normal FHR can vary from beat to beat and is referred to as “short-term variability” or “beat-to-beat variability.” The normal variation from one beat to another is 5-25 bpm. Variability in the FHR is a sign of a healthy autonomic nervous system, chemoreceptors, baroreceptors, and cardiac responsiveness. The FHR becomes nonreassuring if the variability is < 5 or > 25 bpm. A decrease in FHR variability can be due to fetal sleep state, fetal acidosis, or maternal sedation from drugs.
* Minimal variability is an amplitude of 5 bpm or less.
* Moderate variability is normal, with an amplitude range is 6 to 25 bpm.
* Marked variability has an amplitude range > 25 bpm.
Tachycardia may be secondary to fetal hypoxia, maternal fever, chorioamnionitis, anticholinergics, beta-agonists, fetal anemia, or tachyarrhythmias.
Bradycardia could be due to congenital heart block, beta-antagonists, hypoglycemia, hypothermia, or fetal hypoxia.
Variability of FHR is primarily influenced by ____________.
Variability of FHR is primarily influenced by the parasympathetic tone, with increasing tone exerting an increased effect on the heart rate, and therefore increasing variability.
This is evidenced by the fact that the maternal administration of atropine, which effectively eliminated the vagal tone in the fetus as it readily crosses the placenta, causes a decrease in FHR variability. Conversely, maternal administration of a beta-blocker which also readily crosses the placenta has minimal effect on the FHR variability.
How is early deceleration differentiated from late deceleration on FHR monitoring?
Early deceleration:
Early decelerations occur simultaneously with uterine contractions. The onset, nadir, and offset of each deceleration coincide with the onset, nadir, and offset of the uterine contraction. Head compression can precipitate early decelerations which are believed to result from reflex vagal activity secondary to mild hypoxia. Early decelerations are not ominous/not associated with fetal distress.
Late deceleration:
**Late deceleration starts after the onset of a uterine contraction with a nadir > 30 seconds after the onset of a contraction. **Late deceleration is most likely due to uteroplacental insufficiency/response to hypoxemia. The severity is determined by the magnitude of the deceleration. The delayed onset of the deceleration reflects the time needed for the chemoreceptors to detect decreased oxygen tension and change FHR via the vagus nerve. Late decelerations may also result due to myocardial failure secondary to decreased coronary blood flow.
VEAL CHOP
Variable - Cord compression
Early - Head compression
Accelerations - Okay
Late - Placental insufficiency
How are sustained variable decelerations treated?
Amnioinfusion (shown to decrease rate of C-Section)
Variable decelerations, as the name suggests, vary in depth, shape, and duration. They often are abrupt in onset and offset without coinciding with uterine contractions. Variable decelerations result from baroreceptor or chemoreceptor-mediated vagal activity. Umbilical cord occlusion, either partial or complete, results in variable decelerations.
A healthy fetus can typically tolerate mild to moderate variable decelerations without decompensation. With sustained, severe variable decelerations or persistent fetal bradycardia, it is difficult for the fetus to maintain cardiac output and umbilical blood flow.
MORE:
A variable deceleration reflects the fetal autonomic reflex response to transient mechanical compression of the umbilical cord. Umbilical vein and umbilical artery compression both occur. Initially, compression of the umbilical cord occludes the thin-walled and compliant umbilical vein. This results in decreased fetal venous return which triggers a baroreceptor-mediated reflex rise in FHR. Further compression occludes the umbilical arteries, causing an abrupt increase in fetal peripheral resistance and blood pressure. Baroreceptors detect the abrupt rise in blood pressure, triggering an increase in parasympathetic outflow and an abrupt decrease in heart rate. The reverse occurs as cord decompression begins. Prompt attention is required because ongoing hypoxic injury cannot be excluded.
In-utero resuscitation is indicated for fetal distress, with the goal of improving fetal oxygenation. Measures of in-utero fetal resuscitation include:
In-utero resuscitation is indicated for fetal distress, with the goal of improving fetal oxygenation. Measures of in-utero fetal resuscitation include:
* Repositioning of the mother to a lateral or “hands and knees” position
* Administration of supplemental oxygen (which is controversial)
* Administration of intravenous fluids
* Administer vasopressors if the patient is hypotensive
* Discontinuation of uterotonic drugs if these have been administered
* Administration of a tocolytic if sustained uterine contraction is suspected.
Fetal hypoxia mnemonic:
SPOILT: Stop oxytocin, Pressure (treat hypotension), Oxygen, Intravenous fluid bolus, Left lateral decubitus (or all fours), Tocolytics
Refractory late decelerations are an indication for emergent cesarean delivery after failure of in-utero resuscitation.
The risk of Meconium Aspiration Syndrome (MAS) is highest in..
The risk of Meconium Aspiration Syndrome (MAS) is highest in post-term deliveries (>41 weeks).