Lecture 30: Ax for Cesarean Sections, Neonates, & Geriatrics (Exam 4) Flashcards
What increases during Pregnancy
- CO (b/c Increased HR & SV)
- Blood & plasma vol
- Minute ventilation (b/c of increased RR)
- Oxygen consumption by 20%
- Intragastric pressure
- Renal plasma flow & GFR
What decreases in pregnancy
- HB & PCV
- Plasma protein
- PaCO2
- Tidal volume
- Function residual/total lung capacity
- Total pulmonary resistance & peripheral vascular resistance
- GI motility/gastric emptying/ pH
- BUN & Creatinine
What are potential complications w/ venous return in the dam
Venous return may be decreased when placed dorsally due to compression of vena cava by gravid uterus resulting in decreased cardiac output & hypotension (not a concern unless less than 25 kg)
Describe relative anemia as a potential complication
- Maternal blood vol increases ~20%
- PCV w/in the norm range may mean the dam is actually dehydrated
What is a potential complications in small breed dogs, large litters, or w/ uterine inertia
Hypocalcemia
What are some other complications
- Increased myocardial work & reduced cardiac reserve
- Increases in alveolar ventilation & reduced FRC results in reduced MAC req
- Prone to hypoxemia
- Elevated renal values can indicate dehydration or underlying kidney dx
What is necessary during ax to maintain kidney perfusion
- Pre op fluid resuscitation
- Tailored fluid plan +/- use of vasopressors
Describe an emergency C-section
- Px has been in active labor for > 1 H w/ no fetus delivered
- May be in a compromised metabolic state
- Viability of puppies is a concern (b/c of increased mortality for the dam & fetuses)
What is the most common cause of dystocia
If the fetuses are to big or to large of a litter
What fetal heart rate is considered healthy
150 - 200 bpm
What fetal HR is seen if there is fetal stress
100 - 150 bpm
What is the goal amount of time it should take to get the fetuses out
Have them out w/ 5 - 10 mins of induction
What may increase the risk of esophageal reflux
- Increased gastric acid
- Decreased lower esophageal tone b/c of increased abdominal pressure
What drugs can be given to help w/ reflux
- Cerenia
- Metoclopramide
Why is pre oxygenation be done pre op
Prone to hypoxemia in late-preg due to decreased functional reserve capacity
What should be considered when discussing premeds for C section
- Can us noncompliant px
- Avoid drugs that cause vomiting
- Most cross the placenta (short acting that can be antagonized preferred)
- Drugs highly protein bound don’t readily cross the placenta
Describe opioid as a pre med
- Sedation & analgesia
- Dose dep respiratory depression & bradycardia in the dam & fetuses
- Can reverse w/ naloxone
Describe anticholinergics as a pre med
- Atropine: controversial b/c crosses placenta & increases O2 consumption by the fetuses
- Glycopyrrolate doesn’t cross the placenta
Describe benzodiazepines as a pre med
- Mild sedation & skeletal muscle relaxation
- Prefer midazolam b/c water soluble & therefore shorter duration than diazepam
- Can cause respiratory depression
- Fetal livers do no metabolize so there is prolonged sedation
- Antagonize w/ flumazenil after delivery
Describe a2 agonist as a pre med
This & phenothiazines (ace) are not recommended for c sections
T/F: If you want viable babies give a pre med
False; don’t give a pre med if you want viable babies
What reduces the risk of aspiration during induction
- Swiftly securing the airway via intubation
- Cuff inflation during induction
- Have suction ava
- Keep px in sternal w/ head above the stomach
Is “Masking down” recommended
NO!
Describe the use of propofol as an injectable induction agent
- Metabolized in the liver & crosses the placenta
- Causes hypotension due to vasodilation
- Respiratory depression may necessitate IPPV
- Provides no analgesia
- Not cumulative
Describe the use of Alfaxalone as an injectable induction agent
Given IV for a C section in dogs had similar puppy survival rates to propofol & was assoc w/ better neonatal vitality during first 60 mins of birth
Describe using injectable ketamine + diazepam for a C section
- Ketamine causes less CV depression in dams but has significant depressant effects in neonates
- Decreased likelihood of puppies breathing spontaneously @ birth w/ use of ketamine
Describe using injectable etomidate for a C section
- Used for dams w/ pre existing cardia dx
- Rapid induction & short duration w/ min CV & respiratory depressant effect
Describe using inhalant ax for maintenance
- All cross the placenta b/c of lipid solubility & low molecular wgt
- Cause CV & respiratory depression
- Keep as low as possible to avoid neonatal respiratory depression
When is mechanical ventilation used?
When there is pressure won the diaphragm from uterus
Why should hyperventilation be avoided
B/c maternal hypocapnia is assoc w/ decreased uterine & umbilical BF & increased maternal affinity for hemoglobin (can cause fetal hypoxemia)
What LAs can be considered for a Csection
- Line block w/ lidocaine
- Bupivacaine before sx & epidural
- TAP Block
Why can LAs be used in c-section
To improve relaxation of ovarian pedicles & facilitate exteriorization of the uterus
Describe the use of epidural ax in c-sections
- Decrease vol by 25% (b/c of decreased epidural space)
- Epidural lidocaine provides good regional ax & muscle relaxation
- Use lidocaine & not bupivacaine b/c of shorter onset & duration
- Can use morphine to add analgesia
What is a major complication during c section ax
- Hypotension
- Treat if MAP is below 60 mmHg or systolic is below 80 mmHg
What can be give if experiencing hypotension during c-section
- Positive inotropes like ephedrine, dobutamine, or dopamine
- To improve maternal BP
What management should be done once the babies are out
- Deliver as quickly as poss
- Rub vigorously to stimulate breathing & movement
- Supplement w/ O2 using a face mask or in the oxygen chamber
- Analeptics can be used to stimulate respiration but should be given w/ supplemental O2
- Give naloxone if dam was given opioids before the removal of fetus
What can be done if the babies are bradycardic (HR of < 180)
- Supplement O2
- Consider atropine
Define neonate
Up to 4 to 6 Wks
Define pediatric
6 to 12 W
What are some considerations of ax for neonatal/pediatric pxs
- CO is HR dep (avoid bradycardia)
- Airway obstruction, hypoventilation, & hypoxemia can occur
- Tissue oxygen demand is 2 to 3 times greater
- Hepatic renal systems are not fully fxnal until 8 Wks (avoid drugs w/ extensive metabolism or reduce the dose)
- Hypoglycemia can occur from fasting & min glycogen stores (add dextrose to IV)
- High fluid rates are not tolerated
- Highly protein bound drugs will have a greater effect (b/c more free drug circulation)
- Poor thermoregulatory ability (have a warming device ready)
What are some premed considerations of ax for neonatal/pediatric pxs
- Avoid acepromazine & a2 in pediatric px
- Midazolam has short duration & better uptake
- Opioids may cause respiratory depression & bradycardia (provide IPPV w/ anticholinergic)
- Glycopyrrolate lasts longer & less likely to produce sinus tachycardia
What are some considerations of ax for geriatric pxs
- Lower drug dosages & use of short acting drugs that can be antagonized
- Plan for oxygen supplementation & IPPV
- Careful titration of IV fluids before, during, & after ax
- Hypothermia & prolonged recovery are common
- Hypotension should be swiftly treated w/ a positive inotrope
