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Unit 11 - Across the Lifespan
Terms in this set (195)
How does pregnancy affect minute ventilation?
Progesterone is a respiratory stimulant, it increases minute ventilation by up to 50%
-Vt increases by 40%
-RR increases by 10%
How does pregnancy affect the mother's arterial blood gas?
-The increase in minute ventilation results in a respiratory alkalosis with renal compensation
-Arterial pH = no change
-PaO2 = Increased (104-108 mmHg)
-PaCO2 = Decreased (28-32 mmHg)
-HCO3- = Decreased (20 mmol/L)
How does pregnancy affect the oxyhemoglobin dissociation curve?
-Right shift (Increased p450) → facilitates O2 unloading to the fetus
How does pregnancy affect the lung volumes and capacities?
-FRC is reduces as a function of a decrease in ERV and RV (ERV > RV)
-An increased O2 consumption paired with a decreased FRC hastens the onset of hypoxemia
How does cardiac output change during pregnancy and delivery?
How do blood pressure and systemic vascular resistance change during pregnancy?
Who is at risk for aortocaval compression and how do you treat it?
In the supine position, the gravid uterus compresses both the vena cava and the aorta → decreased venous return and CO
-Displace the mothers uterus away from the vena cava and aorta
-Left lateral displacement 15 degrees should be used for anyone in their 2nd or 3rd trimester
How does the intravascular fluid volume change during pregnancy?
What hematologic changes accompany pregnancy?
How does MAC change during pregnancy?
MAC is decreased by 30-40% due to increased progesterone
How does pregnancy affect gastric pH and volume?
Pregnancy increases gastric volume and decreases gastric pH → due to increased gastrin
How does pregnancy affect gastric emptying?
-Before onset of labor = no change
-After onset of labor = slowed
How does pregnancy affect uterine blood flow?
At term, uterine blood flow increases to 500-700 mL/min (10% of CO)
What conditions can reduce uterine blood flow?
-Uterine blood flow does not autoregulate → dependent on MAP, CO, and uterine vascular resistance
-Decreased perfusion → maternal hypotension
-Increased resistance → uterine contraction, hypertensive conditions
Discuss the use of phenylephrine and ephedrine in the laboring patient.
-Classic teaching states that phenylephrine increases uterine vascular resistance and reduces placental perfusion
-More recent evidence suggests that phenylephrine is as efficacious as ephedrine for fetal pH in healthy mothers
Which law determines which drugs will pass through the placenta?
-The Fick principle
Drug characteristics that favor transfer
-Low molecular weight (, 500 daltons)
-High lipid solubility
Define the 3 stages of labor.
-Stage 1: Beginning of regular contractions to full cervical dilation (10 cm)
-Stage 2: Full cervical dilation to delivery of the fetus
-Stage 3: Delivery of the placenta
How does uncontrolled labor pain affect the fetus?
Uncontrolled pain can result in:
-Increased maternal catecholamines → HTN → reduced uterine blood flow
-Maternal hyperventilation → leftward shift of oxyHgb curve → reduced delivery of O2 to the fetus
Compare and contrast the pain that results from the first and second stages of labor.
First stage: Pain begins in the lower uterine segment of the cervix → origin T10-L1 posterior nerve roots
Second stage: Adds in pain impulses form the vagina, perineum, and pelvic floor → origin S2-S4 posterior nerve roots
Compare and contrast the regional anesthetic techniques that can be used for first and second stage labor pain.
Describe the "needle through needle" technique for CSE.
-Most common approach
-The epidural space is identified with the epidural needle.
-A spinal needle is placed through the epidural needle and the LA and/or opioid is injected into the intrathecal space
-The spinal needle is removed
-An epidural catheter is threaded through the epidural needle
Compare and contrast bupivacaine and ropivacaine for labor.
Discuss the use of 2-chloroprocaine for labor.
-Useful for emergency C/S when epidural is already in place
-Metabolized by pseudocholinesterase in the plasma - minimal placental transfer
-Antagonizes opioid receptors (mu & kappa) and reduces the efficacy of epidural morphine
-Risk of arachnoiditis when used for spinal
Discuss the consequences of an epidural that is placed in the subdural space.
-Neither catheter aspiration or test dose will rule out subdural placement
-Within 10-25 minutes after the epidural is dosed, the patient will experience symptoms of an excessive cephalic spread of LA
-It will resemble a high spinal
What is the treatment for a total spinal?
A total spinal may result from:
-An epidural dose injected into the SA space
-An epidural dose injected into the SD space
-A single shot spinal after a failed epidural block
Treatment: Vasopressors, IVF, left uterine displacement, elevation of legs, intubation if LOC
Discuss the fetal heart rate.
Which type of fetal decelerations are unremarkable?
-Early decelerations do not present a risk of fetal hypoxia
Which type of fetal decelerations cause concern?
-Late and variable decelerations require urgent assessment of fetal status
What are the common causes of fetal deceleration patterns?
*Pneumonic: VEAL CHOP
-Variable decels → Cord compression
-Early decels → Head compression
-Accelerations → Ok or give oxygen
-Late decels → Placental insufficiency
Define premature delivery and list the potential complications from its occurrence.
-Premature delivery is defined as delivery before 37 weeks gestation
-It is the leading cause of perinatal morbidity and mortality, risk is even higher for newborns weighing < 1500g
-Incidence of prematurity rises with multiple gestations and premature ROM
Complications of premature delivery
-Respiratory distress syndrome
Discuss the use of steroids and tocolytic agents in the prevention of premature delivery.
-Corticosteroids (betamethasone) hasten fetal lung maturity. These drugs begin to take effect within 18 hours, with peak benefit at 48 hours
-Tocolytic agents stop labor for about 24-48 hours. They provide a bridge that allows the corticosteroids time to work. Antibiotic prophylaxis for chorioamnionititis is also given at this time
-Tocolytic agents or corticosteroids are seldom given after 33 weeks
What are the side effects of beta-2 agonists when used for tocolysis?
-Beta-2 agonists: Terbutaline, Ritodrine
-Hypokalemia from intracellular K+ shift
-May increase FHR (cross placenta)
-Hyperglycemia from glycogenolysis in the liver
*The newborn of a hyperglycemic mother is at risk of post-delivery hypoglycemia. The mother's glucose supply is gone, but the insulin in the neonatal circulation remains
How does the serum magnesium level correspond with its clinical effects?
What are the side effects of magnesium?
-Skeletal muscle weakness
-Reduced responsiveness to ephedrine and phenylephrine
What is the treatment for hypermagnesemia?
How can oxytocin be administered?
-What are the potential side effects?
-Can be given IV or the OB can inject it directly into the uterus
How can methergine be administered?
-It can be given 0.2 mg IM (not IV)
-IV administration can cause significant vasoconstriction, hypertension, and cerebral hemorrhage
What are the pros and cons of general anesthesia for cesarean section?
-Mortality is 17x higher with a general anesthetic
-Most common cause of maternal death is failure to successfully manage the airway
Describe aspiration prophylaxis for the patient scheduled for a cesarean section.
Triple prophylaxis against aspiration
-Sodium citrate to neutralize gastric acid
-H2 receptor antagonist (ranitidine) to reduce gastric acid secretion
-Gastrokinetic agent (metoclopramide) to hasten gastric emptying and increase LES tone
When is the pregnant patient who presents for non-obstetric surgery at risk for aspiration?
-Consider aspiration prophylaxis if mom is beyond 14 weeks gestation
-Administer an antacid (sodium citrate 15-30 mL) within 30 minutes of induction, ranitidine 1 hour prior to induction, and consider metoclopramide to facilitate gastric emptying
-If mom is beyond 14 weeks gestation, secure the airway with a RSI and a 6.0-7.0 ETT
What is the risk of NSAIDs when used in the pregnant patient?
Avoid NSAIDs after the first trimester as they may close the ductus arteriosus
Compare and contrast the diagnostic criteria for gestational HTN, preeclampsia, and eclampsia.
Classic triad of preeclampsia → hypertension after 20 weeks gestation, proteinuria, and generalized edema
Discuss the balance of prostacyclin and thromboxane in the patient with preeclampsia.
-The healthy placenta produces thromboxane and prostacyclin in equal amounts
-The patient with preeclampsia produces up to 7x more thromboxane than prostacyclin
-TXA2 favors vasoconstriction, platelet aggregation, and reduced placental blood flow
Compare and contrast mild and severe preeclampsia.
Discuss the use of magnesium for preeclampsia.
-The presence of seizures differentiates between preeclampsia and eclampsia
Seizure prophylaxis with mag sulfate
-Loading dose → 4 g over 10 minutes
-Infusion → 1-2 g/hr
Treatment for Mg. toxicity
-10 mL of 10% calcium gluconate IV
Detail the anesthetic management for the patient with preeclampsia.
-Fluid management is balanced between a volume contracted patient and a "leaky" vasculature from endothelial dysfunction
-Neuraxial anesthesia assists with BP control and also provides better uteroplacental perfusion
-Be sure to rule out thrombocytopenia (< 100,000) before performing a neuraxial block
-Due to airway swelling, these patients have a higher incidence of difficult intubation
-These patients have an exaggerated response to sympathomimetics and methergine
-If they are receiving magnesium therapy, they will exhibit an increased sensitivity to neuromuscular blockers
-Magnesium relaxes the uterus and increases the risk of postpartum hemorrhage
What is HELLP syndrome?
-What is the definitive treatment?
-HELLP → Hemolysis, Elevated liver enzymes, low platelets
-HELLP develops in 5-10% of preeclamptic mothers. These patients experience epigastric pain and upper abdominal tenderness
-Definitive treatment for HELLP syndrome (and preeclampsia) is delivery of the fetus
Discuss the anesthetic considerations for maternal cocaine abuse.
-Flooding the synaptic cleft with NE increases the SNS tone
-CV risks → tachycardia, dysrhythmias, myocardial ischemia
-Acute intoxication increases MAC/Chronic use decreases MAC
-OB risks → spontaneous abortion, premature labor, placental abruption, low APGAR scores
-HTN is best treated with vasodilators, beta blockers can use HF is the SVR is significantly elevated
-Hypotension may not respond to ephedrine in chronic cocaine users
-Chronic cocaine abuse is associated with thrombocytopenia
What is the difference between placenta accreta, increta, and percreta?
-What is the major risk that these complications present?
-Placenta accreta → attaches to the surface of the myometrium
-Placenta increta → invades the myometrium
-Placenta percreta → extends beyond the uterus
-Uterine contractility is impaired and there is a potential for tremendous blood loss. Neuraxial is safe, but GA is preferred
What conditions increase the risk of abnormal placental implantation?
The risk of abnormal implantation is closely associated with placenta previa and previous cesarean sections
What is placenta previa?
-How does it present?
-Placenta previa occurs when the placenta attaches to the lower uterine segment
-It partially or completely covers the cervical os
-Associated with painless vaginal bleeding
-Potential for hemorrhage
What are the risk factors for placental abruption?
-How does it present?
-Partial or complete separation of the placenta from the uterine wall prior to delivery. It results in hemorrhage and fetal hypoxia
-Excessive alcohol use
*Painful vaginal bleeding
What is the most common cause of postpartum hemorrhage?
-What are the risk factors?
-Uterine atony is the most common cause of postpartum hemorrhage
-Prolonged oxytocin infusion prior to surgery
A patient suffers from retained placental fragments.
-What IV medication can you give to help with the extraction?
IV nitroglycerine provides uterine relaxation for placental extraction
What are the treatment options for uterine atony?
What does the APGAR score mean?
-Used to assess the newborn and guide resuscitation efforts
-Parameters are evaluated at 1 and 5 minutes after delivery
-Normal → 8-10
-Moderate distress → 4-7
-Impending demise → 0-3
Know how to calculate the APGAR score.
What is the best indicator of ventilation during neonatal resuscitation?
Resolution of bradycardia is the best indicator of adequate ventilation
How do you dose epinephrine and fluids during neonatal resuscitation?
What are the normal vital signs for a newborn?
-How do they trend as the child ages?
Why is the neonate's minute ventilation higher than the adult?
-Oxygen consumption and CO2 production are twice those of the adult → therefore the neonate must increase alveolar ventilation accordingly
-It is metabolically more efficient to increase RR than it is to increase Vt, this is why newborns have a high RR
What is the primary determinant of blood pressure in the neonate?
-Heart rate is the primary determinant of cardiac output and systolic BP
-The neonatal myocardium lacks the contractile elements to significantly adjust contractility or stoke volume; the ventricle is noncompliant. Furthermore, the Frank-Starling relationship is underdeveloped in the newborn
-The HR must be maintained to ensure adequate tissue perfusion and O2 delivery
Describe the autonomic influence on the newborns heart.
-Autonomic regulation of the heart is immature at birth, with the SNS being less mature than the PNS. Stressful situations such as laryngoscopy and suction of the airway may cause bradycardia. Atropine may be administered prior to induction to mitigate this response
-Additionally, the baroreceptor reflex is poorly developed, so the reflex fails to increase HR in the setting of hypovolemia
Contrast the breathing pattern in adults and infants.
-Adult = mouth or nose
-Infant = Preferential nose breather for up to 5 moms of age
-Infants convert to oral breathing if nasal passages are obstructed
-Bilateral china atresia may require emergency airway management if the infant is unable to mouth breathe
Contrast the relative size of the tongue in adults and infants.
-Adult = Small relative to oral volume
-Infant = Large relative to oral volume
-Tongue is closer to the soft palate in infants, which makes it more likely to obstruct the upper airway and more difficult to displace during laryngoscopy
Contrast the relative neck length in adults and infants.
-Adults = Longer
-Infant = Shorter
Contrast the epiglottis shape in adults and infants.
-Adult = Leaf (C shape), floppier, shorter
-Infant = U (omega shape), stiffer, longer
Contrast the vocal cord position in adults and infants.
-Adults = Perpendicular to trachea
-Infant = Anterior slant - passage of ETT may be more difficult
Contrast the laryngeal position in adults and infants.
-Adult = C5-C6
-Infant = C3-C4
-Larynx is more superior/cephalad, but NOT anterior. The only time the infant's airway is more "anterior" is during neck flexion
-Same position as adult at age 5-6 years
Contrast the narrowest point of the airway in adults and infants.
-Adult = Glottis (vocal cords)
-Infant = Cricoid or glottis*
*Resistance to ETT insertion beyond the vocal cords is at the cricoid ring. Cricoid tissue is prone to inflammation and edema formation
Why did we include an asterisk on the narrowest region of the infant airway?
-Infant = Narrowest at the cricoid ring & funnel shaped airway
-Adult = Narrowest at the vocal cords & cylinder shaped airway
*The narrowest non-displacible portion of the pediatric airway is the cricoid cartilage, the glottis is actually more narrow, but it can be easily displaced
Contrast the orientation of the right mainstream bronchus in adults and infants.
-Adult = More vertical
-Infant = Less vertical
-Up to age 3, both bronchi take off at 55 degrees
-In the adult, the right bronchus takes off at 25 degrees, and the left at 45 degrees
Contrast the optimal intubation position for adults and infants.
-Adult = Sniffing position
-Infant = Head on bed with shoulder roll (large occiput)
Contrast the oxygen consumption, alveolar ventilation, respiratory rate, and tidal volume in neonates and adults.
Why do neonates desaturate faster than adults?
Neonates have a/an:
-Increased oxygen consumption to support metabolic demand
-Increased alveolar ventilation to increase oxygen supply
-Slightly decreased FRC reflects a reduced oxygen reserve
-The net result is that the neonate has an increased ratio of alveolar ventilation relative to the size of its FRC.
Why is an inhalation induction faster with a neonate than with an adult?
-The increased ratio of ventilation relative to the size of the FRC explains the quicker induction.
-A faster turnover of FRC allowed for a speedier development of anesthetic partial pressure inside the alveoli.
What is the difference between fast and slow twitch muscle fibers?
-How does this relate to neonatal pulmonary mechanics?
-Type I = slow twitch muscle fibers that are built for endurance - resistant to fatigue
-Type II = fast twitch muscle fibers that are built for short bursts of heavy work - they tire easily
-The neonatal diaphragm has 25% type I fibers (adults have 55%) → neonates tire easily
Compare and contrast neonates to adults in terms of: FRC, VC, TLC, RV, CC, and Vt
How does the newborn's ABG change from delivery to the first 24 hours of life?
How does hypoxemia affect ventilation in the newborn?
-Respiratory control don't mature until 42-44 weeks
-Before maturation → hypoxemia depresses ventilation
-After maturation → hypoxemia stimulates ventilation
What is the P50 of fetal hemoglobin?
-Why is this important?
-HgbF has a P50 of 19 mmHg, this shifts the curve to the left, creating an O2 partial pressure that facilitates passage of O2 from the mother to the fetus
Why does HgbF have a higher affinity for O2?
-Adult Hgb consist of 2 alpha and 2 beta chains
-Fetal Hgb consist of 2 alpha and 2 gamma chains
-The beta chains are the binding site for 2,3 DPG → Infants don't have these beta chains so they can't bind 2,3 DPG
Discuss the physiologic anemia of the infant.
What is the dose for PRBC transfusion in the neonate?
-How much will this increase Hgb?
Dose = 10-15 mL/kg
-10 mL/kg will raise Hgb by 1-2 g/dL
What are the indications for FFP transfusion in the neonate?
-Emergency reversal of warfarin
-Correction of coagulopathic bleeding with increase PT > 1.5 or increased PTT
-Correction of coagulopathic bleeding if > 1 blood volume has been replaced and coagulation studies are not easily obtained
What is the dose for FFP transfusion in the neonate?
Dose = 10-20 mL/kg
When is platelet transfusion indicated in the neonate?
-What is the dose?
-Invasive procedures to maintain platelet count above 50,000
-Dose if obtained form aphaeresis = 5 mL/kg
-Dose if pooled platelet concentrate = 1 pack/10 kg
Describe the physiologic changes that occur as a result of massive transfusion in the neonate/infant.
-Acidosis from inadequate oxygenation and increased serum lactate
-Alkalosis from citrate metabolism to bicarbonate in the liver
-Hypothermia from transfusion of cold blood
-Hyperglycemia from dextrose additive in stored blood
-Hypocalcemia from binding of calcium by citrate
-Hyperkalemia from administration of older blood → The risk is reduced by administering washed or fresh cells that are less than 7 days old
What is the normal H&H at birth, 3 months, 6-12 months?
What is the estimated blood volume in the premature neonate, term neonate, infant, child > 1 year?
A 3 kg term neonate requires emergency exploratory laparotomy for necrotizing enterocolitis. Her preoperative hematocrit is 50%. What is the maximum allowable blood loss to maintain a hematocrit of 40%?
-MABL = 80 mL x [(50-40)/50] = 48 mL
When do GFR and renal tubular function achieve full maturity?
-Normal GFR is reached at 8-24 months of age
-Normal tubular function is reached at 2 years of age
Compare and contrast the distribution of body water in the premature neonate, neonate, child, and adult.
What signs suggest dehydration in the neonate?
-Sunken anterior fontanel
-Weight loss (a 10% reduction the first week is normal)
-Irritability or lethargy
-Dry mucus membranes
-Absence of tears
-Decreased skin turgor
-Increased hematocrit in the absence of transfusion
Describe the 4:2:1 rule of fluid management.
-Step 1: 0-10 kg → Begin with 4 mL/kg/hr
-Step 2: 10-20 kg → Add 2 mL/kg/hr to the previous total
-Step 3: > 20 kg → Add 1 mL/kg/hr to the previous total
-If the patient is > 20 kg → patient's weight in kg + 40
How should the NPO fluid deficit be replaced?
Multiply the patient's hourly fluid maintenance rate by the number of hours of NPO time → replace this over three hours
-1st hour → 50%
-2nd hour → 25%
-3rd hour → 25%
How should third space losses be replaced in the neonate?
-Minimal surgical trauma = 3-4 mL/kg/hr
-Moderate surgical trauma = 5-6 mL/kg/hr
-Major surgical trauma = 7-10 mL/kg/hr
-Third-space loss is not included in the first hour of anesthesia
What ratio should be used to replace blood loss with crystalloid, colloid, and blood?
-Replace with crystalloid at 3:1 ratio
-Replace with colloid at 1:1 ratio
-Replace with blood at 1:1 ratio
Which pediatric patient populations should receive an IVF that contains glucose?
-Routine use of glucose-containing solutions is generally not recommended
-These fluids should be reserved for infants and children at risk of developing hypoglycemia
-Newborns of diabetic mothers
-Children with diabetes who received insulin on the day of surgery
-Children who receive glucose-based parenteral nutrition
What is the cardiac output in the newborn?
-How does this affect pharmacokinetics?
In the newborn, cardiac output is 200 mL/kg/min, which means that drugs are delivered to and removed from the rest of the body at a faster rate than the adult
Discuss plasma protein binding in the neonate.
-Before 6 months of age there are lower concentrations of albumin and alpha-1 acid glycoprotein
-Highly protein bound drugs will display higher free drug levels, which increases the risk of toxicity.
Discuss MAC in children. Does this rule apply to all volatile anesthetics?
-Infant → 2-3 months → MAC peaks at its highest level
-Neonate → 0-30 days → MAC is lower than the infant
-Premature → MAC is lower than the neonate
How do you dose Sch in the neonate?
-2 mg/kg due to relatively higher ECF
How do you dose nondepolarizing neuromuscular blockers in the neonate?
Dose = same as adults on a mg/kg basis
-ECF is larger, but the NMJ is more sensitive to the effects of nondepolarizers
What is the dose for IM succinylcholine?
-Which IM site has the fastest onset of action?
-Neonates and infants → 5 mg/kg
-Older children → 4 mg/kg
-Intralingual administration via the submental approach has the fastest onset
What is the primary hemodynamic concern when a small child receives a second dose of Sch?
-In children < 5 years, Sch may cause bradycardia or asystole
-More likely after repeat administration, atropine (.02 mg/kg) will mitigate this response
An infant that is susceptible to malignant hyperthermia develops a laryngospasm during induction of anesthesia. There is no IV in place.
-What is the best drug to give at this time?
Rocuronium is the only nondepolarizer that can be given via the IM route
-If < 1 year = 1 mg/kg
-If > 1 year = 1.8 mg/kg
Describe the 5 types of tracheoesophageal atresia.
-Which one is the most common?
-Type C accounts for 90% of all TEFs
-Type C → upper esophagus ends in a blind pouch and the lower esophagus communicates with the distal trachea
What prenatal finding suggests esophageal atresia?
-How is the diagnosis confirmed after birth?
-Maternal polyhydramnios is a key diagnostic indicator for TEF → EA prevents the fetus from swallowing amniotic fluid
-Diagnosis is confirmed by the inability to pass a gastric tube into the stomach
-Other S/Sx → choking, coughing, and cyanosis during oral feeding
What is the VACTERL association?
-25-50% of patients with TEF suffer from other congenital anomalies
A patient has a type C TEF. Where should the tip of the ETT be positioned?
-Below the fistula, but above the carina
How should you induce anesthesia in a patient undergoing a type C TEF repair?
-Head up position and frequent suctioning to minimize the risk of gastric aspiration
-Awake intubation or inhalation induction with spontaneous ventilation
-PPV → gastric distention → decreased thoracic compliance → downward spiral
-Placement of g-tube allows for gastric decompression, open it to atmosphere before induction if patient already has one
-Place the ETT below the fistula, but above the carina
Discuss the pathophysiology of respiratory distress syndrome.
-In the absence of adequate surfactant, the alveoli remain stiff and non-compliant
-Small alveoli tend to collapse
-Larger alveoli become over distended
-This promotes atelectasis, reduces the surface area where gas exchange can take place → V/Q mismatch
-Hypoxemia leads to acidosis and the possibly the return to fetal circulation
What test can be done to assess fetal lung maturity in utero?
-What value suggests adequate lung development?
-Amniocentesis can assist in the determination of fetal lung development
-Lecithin to sphingomyelin (L/S ratio) > 2 suggests adequate lung development
Discuss the use of pre and postductal Spo2 monitoring in the newborn.
-A preductal pulse oximeter is placed on the right upper extremity, while the postductal monitor is usually placed on a lower extremity
A difference between the readings indicates
-Right to left cardiac shunt
-Return to fetal circulation via the PDA
A patient has a hernia at the foramen of Bochdalek. Which congenital condition does this patient have?
-Congenital diaphragmatic hernia → allows the abdominal contents to enter the thoracic cavity
-Foramen of Bochdalek is the most common side of herniation (left side)
-Diagram is from the abdomen looking up towards the thorax
What signs and symptoms suggest a congenital diaphragmatic hernia?
-Scaphoid abdomen (sunken in), respiratory distress, barrel chest, cardiac displacement
Describe the ventilatory management of the patient with a congenital diaphragmatic hernia.
-Pulmonary hypoplasia will be present, keep PIP < 25-30 cmH20 to minimize barotrauma
-This may require permissive hypercapnia, this is the lesser of two evils
-Abdominal closure may increase PIP, a pulse oximeter placed on the lower extremity can warn you of increased intra-abdominal pressure
Compare and contrast omphalocele and gastroschisis.
Describe the anesthetic concerns for a patient with omphalocele or gastroschisis.
-If gastroschisis, abdominal contents are placed in a bag after delivery, this minimizes water and heat loss
-Monitor peak airway pressure, if PIP > 25-30 cmH20 the surgical closure may require staging
-Measure SpO2 on the lower extremity to monitor for impaired venous return
-Major fluid/electrolyte shifts
How and when does pyloric stenosis present?
-Hypertrophy of the pyloric muscle creates a mechanical obstruction at the gastric outlet (between the stomach and duodenum)
-An olive shaped mass can be palpated just below the xiphoid process
-Non-bilious projectile vomiting
-Occurs in the first 2-12 weeks of life, more common in males
Describe the pathophysiology of pyloric stenosis.
Vomiting depletes water → hyponatremic, hypokalemic, hypochloremic metabolic alkalosis
*Metabolic acidosis is a late complication!
Describe the anesthetic management of the patient with pyloric stenosis.
-Medical (not surgical) emergency, surgery should be postponed until the fluid, electrolyte, and acid-base status are optimized
-Anticipate a full stomach, empty the stomach before induction
-Liberal hydration to correct dehydration
-Postoperative apnea is common → CSF pH remains alkalotic even after serum acid-base status is normalized
What is necrotizing enterocolitis and who is at risk?
NEC is necrosis of the bowel; usually the terminal ilium and proximal colon.
-Likely the result of early feeding, impaired absorption by the gut leads to states, bacterial overgrowth, and infection
At risk babies
-Prematurity (< 32 weeks)
-Low birth weight (< 1500 g)
Discuss the management of patients with NEC.
-These babies are managed medically, however, bowel perforation necessitates bowel resection and usual colostomy. These patients often have a metabolic acidosis and require substantial fluid replacement
-Bowel resection early in life can lead to short gut syndrome
What is retinopathy of prematurity?
-ROM causes abnormal vascular development in the retina.
-The immature retinal blood vessels are at risk of vasoconstriction and hemorrhage → retinal detachment and blindness
What are the risk factors for ROP?
-Low birth weight
Discuss the relationship between FiO2 and ROP.
-Until retinal maturation is complete (44 weeks post-conception) FiO2 should be titrated to SpO2 of 85-93%
What is apoptosis?
Process of programmed cell death. This is the main concern related to anesthesia and children
Which anesthetic agents have been implicated in apoptosis?
Give the name, location, and function of the 3 fetal shunts.
-Function - Allows umbilical blood to bypass the liver
-Location - Umbilical vein → inferior vena cava
-Function - Shunts blood from RA to LA to bypass lungs to perfuse the upper body
-Location - Right atrium → left atrium
-Function - Shunts blood from the pulmonary trunk to the aorta
-Location - Pulmonary artery → proximal descending aorta
When does each fetal shunt close?
-What is the adult remnant of each?
-Closes - Clamping of the umbilical cord
-Remnant - Ligamentum venosus
-Closes - 3 days
-Remnant - Fossa ovalis
-Closes - Several weeks after birth
-Remnant - Ligamentum arteriosum
List 5 ways the fetal circulation is different than the adult circulation.
1. The placenta is the organ of respiration (adult = lungs)
2. The circulation is arranged in parallel (adult = series)
3. Right-to-left shunting occurs across the foramen oval and ductus arteriosus
4. PVR is high - the lungs are collapsed and filled with fluid, so there is very little pulmonary flow
5. SVR is low - the placenta provides a large, low resistance vascular bed
Describe the circulatory changes that occur during the transition to extrauterine life.
-First breath → lung expansion → decreased PVR
-Placenta separates from uterine wall → increased SVR
-PVR and SVR switch → LA pressure > RA pressure → the flap of the foramen ovale closes
-Decreased PVR → reversal of blood flow through the ductus arteriosus → closure of DA
-Decresed circulating PGE1 → closure of DA
What is the risk of a patent foramen ovale?
-The PFO increases the risk of paradoxical embolism → embolus goes to the brain instead of the lungs
-30% of adults have a patent foramen ovale
What drugs can be used to close the ductus arteriosus?
-Which can be used to open it?
-Closed with indomethacin
-Opened with PGE1
What is an intracardiac shunt?
What conditions affect PVR and SVR?
What is a cyanotic shunt?
-List 5 examples.
-A cyanotic shunt is also called a right-to-left shunt. Venous blood bypasses the lungs
Examples (5 T's)
-Tetralogy of Fallot
-Transposition of the great arteries
-Tricuspid valve abnormality (Epstein's anomaly)
-Total anomalous pulmonary venous connection
What are the hemodynamic goals of the patient with a right-to-left shunt?
What is an acyanotic shunt?
-List 4 examples.
-An acyanotic shunt is also called a left-to-right shunt. Blood in the left side of the heart recirculates through the lungs
-VSD (most common)
-Coarctation of the aorta
What are the hemodynamic goals for the patient with a left-to-right shunt?
How do intracardiac shunts affect an inhalation or IV induction?
-Right-to-left shunt = slower induction
-Left-to-right shunt = minimal effect
-Right-to-left shunt = faster induction
-Left-to-right shunt = slower induction
What is Eisenmenger syndrome?
-When a patient with a left-to-right shunt develops pulmonary HTN, which reverses the flow through the shunt → right-to-left shunt
What are the 4 defects associated with tetralogy of Fallot?
1. Right ventricular outflow obstruction
2. Right ventricular hypertrophy due to high venous pressure load from RV obstruction
3. Ventricular septal defect due to septal malalignment
4. Overriding aorta that receives blood from both ventricles
How does a "tet spell" present?
-What situations increases the risk of "tet spells?"
-Hypoxemai and cyanosis
-Classically the child presents with a history of squatting during activity → this increases SVR and reduces the right-to-left shunt
-Stress increases myocardial contractility and can cause a spasm of the infravalvular region of the RVOT
-"tet spells" occur during stressful circumstances → exercise, crying, defamation, IV placement, during induction
What is the treatment for a "tet spell" that occurs during the perioperative period?
-Intravascular volume expansion
-Increase SVR with phenylephrine
-Reduce SNS (deepen anesthesia, beta-blockade)
-Avoid inotropes (worsened RVOT obstruction)
-Avoid excessive airway pressure
*An infant may be placed in knee-chest position to mimic squatting
What are the hemodynamic goals for tetralogy of Fallot?
What is the best IV induction agent for the patient with tetralogy of Fallot?
-Ketamine is the best induction agent, it increases SVR and reduces shunting
What is the most common congenital cardiac anomaly in infants and children?
-How about adults?
-Infants and children = VSD
-Adults = Bicuspid aortic valve
What is coarctation of the aorta?
-Which syndrome is highly associated with this anomaly?
-Narrowing of the thoracic aorta, in the vicinity of the ductus arteriosus. It typically occur just before or after the ductus arteriosus, but in rare instances it occurs proximal to the left subclavian artery
*Turner's syndrome has a high association with coarctation of the aorta
How is blood pressure affected in the patient with coarctation of the aorta?
As a general rule:
-SBP is elevated in the upper extremities
-SBP is reduced in the lower extremities
Discuss Epstein's anomaly.
-Most common congenital defect of the tricuspid valve, usually an ASD or PFO
-Characterized by a downward displacement of the tricuspid valve and atrialization of the right ventricle
-Tricuspid regurgitation can be severe
-SVT is common
-RV failure is common in the postoperative period
Discuss the anesthetic management of the patient who has previously undergoing Fontan completion.
-This patient has a single ventricle that pumps blood into the systemic circulation - no ventricle to pump blood into the pulmonary circulation
-Blood flow into the lungs is completely dependent on negative intrathoraci pressure during spontaneous breathing
-PPV disrupts this arrangement
-These patient's are preload dependent, don't let them get dry
What is truncus arteriosus?
-Characterized by a single artery that gives rise to the pulmonary, systemic, and coronary circulations.
-With only one artery, there is no specific pathway for blood to enter the pulmonary circulation
-Usually a VSD as well
-Decreasing PVR or increasing pulmonary flow steals blood from systemic and coronary circulations
Discuss the typical ages affected and speed of onset for epiglottitis and croup.
Contrast the regions affected by epiglottitis and croup.
-How do these present on a lateral neck x-ray?
-Region affected → supraglottic structures
-Lateral neck x-ray → swollen epiglottitis (Thumb sign)
-Region affected → laryngeal structures
-Lateral neck x-ray → subglottic narrowing (Steeple sign)
Discuss the clinical presentation and treatment of epiglottis.
-Tripod position helps breathing
-4 D's: Drooling, dysphonia, dyspnea, dysphagia
-Urgent airway management → intubation or tracheostomy
-Abx (if bacterial)
-Induction with spontaneous ventilation (CPAP 10-15 cmH2O)
-ENT surgeon must be present
-Post-op ICU care
Discuss the clinical presentation and treatment of croup.
-Intubation rarely required
Discuss the pathophysiology and presentation of postintubation laryngeal edema.
-AKA post-intubation croup
-Complication of endotracheal intubation or rigid bronchoscopy
-The tracheal mucosa perfusion pressure is 25 cmH2O, using an ETT that is too large or injecting excessive air into the cuff reduces tracheal perfusion → edema → subglottic stenosis → increased work of breathing
-The patient presents with hoarseness, a balky cough, and/or stridor. It typically occurs within 30-60 minutes following extubation
What are the risk factors for postintubation laryngeal edema?
-Age < 4 years
-ETT too large
-ETT cuff volume to high
-Traumatic or multiple intubation attempts
-Head or neck surgery
-Head repositioning during surgery
-History of infectious or post-intubation croup
-Upper respiratory tract infection
What is the best way to minimize the risk of postintubation laryngeal edema?
*Best treatment is prevention
-Post-intubation laryngeal edema can occur with cuffed or uncuffed tubes
-Maintain an air leak < 25 cmH2O
What is the treatment for postintubation laryngeal edema?
-Cool and humidified O2
-Nebulized racemic epinephrine → 0.5 of 2.25% solution in 2.5 mL of 0.9% NaCl
-Dexamethasone 0.25 - 0.5 mg/kg IV
-Heliox is a helium + oxygen mixture that improves laminar airflow by reducing Reynold's number
-Patient should be observed for a minimum of 4 hours after the racemic epinephrine treatment is complete
A patient with a respiratory infection presents for a tonsillectomy.
-Which S/Sx favor postponing the procedure?
How can you reduce the risk of airway complications while anesthetizing a child with an upper respiratory infection?
-Avoid mechanical irrigation of the airway: Facemask > LMA >> ETT
-ETT use increases the risk of bronchospasm 10-fold
-If an ETT must be used, use a smaller size
-Dexamethasone 0.25-0.5 mg/kg
-Ensure a deep plane of anesthesia before instrumenting the airway
-Propofol may reduce the risk of bronchospasm
-Sevoflurane is the best volatile agent
*Pretreatment with a bronchodilator or glycopyrrolate does not provide a clear benefit
Describe the presentation of the child who presents with foreign body aspiration.
-Triad of cough, wheezing, and decreased breath sounds on the affected side
-Supraglottic obstruction → Stridor
-Infraglottic obstruction → Wheezing
What are complications of rigid bronchoscopy?
*Rigid bronchoscopy is the "gold standard" procedure to retrieve the foreign body
-Bradycardia during scope insertion
Which pediatric syndromes are associated with difficult airway management?
Describe the airway in the patient with Trisomy 21.
-Risk for difficult ventilation and intubation
-Palate is narrow with a high arch
-Atlantoaxial instability (C1&C2 subluxation)
-Chronic pulmonary infection
What is CHARGE Association?
-Coloboma (a hole in one of the eye structures)
-(A) -Choanal atresia
-Retardation of growth and development
What is CATCH 22?
-Also called DiGeorge syndrome
-22q11.2 gene deletion
What are the unique anesthetic considerations for the patient with DiGeorge syndrome?
-Hypocalcemia is common
-If the thymus is absent, the child is at high risk for infection
-Thymus transplant of mature T cell infusion
*Use leukocyte-depleted irradiated blood
What activities correspond with 1, 4, and 10 metabolic equivalents?
How does minute ventilation change in the elderly?
-Minute ventilation increases
-Increased Vd necessitate an increased Ve to maintain a normal PaO2
How does lung elasticity change in the elderly?
-Lung elasticity decreases. This collapses the small airways and causes the lung to become overfilled with gas
-Decreased alveolar surface area
-Increased A-a gradient
How does chest wall compliance change in the elderly?
Chest wall compliance decreases. The chest is stiffer and more difficult to expand.
-Increased A:P diameter
-Increased intercostal muscle mass
-Loss of intervertebral disc height
Why does RV increase in the elderly?
-What are the consequences of this?
The aged lung has a reduced elastic recoil, which causes it to become over filled with gas → increased RV and subsequent increased FRC
-CC surpass FRC at 45 years in the supine position and 65 years when standing
-When CC > FRC the small airways collapse during tidal breathing
How does arterial compliance change in the elderly?
-Arterial compliance decreases as a function of loss of elastin and increased collagen.
-Increased SVR → increased BP
-Increased pulse pressure
-Increased Myocardial wall tension to overcome high after load
How does myocardial compliance change in the elderly?
-Myocardial compliance decreases
-Impaired relaxation may cause diastolic dysfunction
-Atrial kick becomes more important for ventricular priming and maintenance of cardiac output
How does the cardiac conduction system change in the elderly?
-There is fibrosis of the conduction system and loss of SA node tissue
-Increased chance of dysthrythmias
How does the blood pressure and pulse pressure change in the elderly?
-BP increases as a function of reduced arterial compliance → increased SVR
-Pulse pressure is also increased
How does systolic and diastolic function change in the elderly?
-Systolic function → no change
-Diastolic function decreases as a function of reduced compliance and increased wall stiffness that impairs myocardial relaxation
How do HR, SV, and CO change in the elderly?
-HR, SV, and CO decrease
Describe the autonomic changes that occur in the elderly.
-Decreased adrenergic receptor density
-Decreased response to catecholamines
-Increased circulating catecholamines as partial compensation
-Reduced ability to increase HR during hypotension (decreased baroreceptor function)
-Impaired thermoregulation increases the risk of hypothermia
How does MAC change in the elderly?
MAC decreases by 6% each decade of life after age 40
Contrast the onset of postoperative delirium and postoperative cognitive dysfunction.
-Postop delirium: Early post period
-POCD: Weeks to months after surgery
Contrast the treatment of postoperative delirium and postoperative cognitive dysfunction.
-Postop delirium → treat underlying cause, antipsychotics, minimize polypharmacy
-POCD → no specific treatment, most cases tend to resolve after 3 months
*To minimize the risk of either condition, use rapidly metabolized drugs
How does sensitivity to LA's change in the elderly?
Sensitivity to LA's increases
-Decreased number of myelinated nerves
-Decreased diameter of myelinated nerves
-Decreased conduction velocity
Do the elderly require a dose adjustment for intrathecal or epidural anesthesia? Why?
-The require a dosage adjustment to both
-Intrathecal - CSF volume is reduced → greater spread of LA
-Epidural - volume of epidural space is reduced → greater spread of LA
Why is it more difficult to place a neuraxial block in the elderly?
-Less space between the posterior spinous processes
-Decreased intravertebral disc height
-Narrow intervertebral foramen
-Calcification of joints
How does the glomerular filtration rate change in the elderly?
-The GFR decreases
-Normal GFR 125 mL/min, this decreases 1 mL/min/year after age 40
-Risk of fluid overload
-Impaired drug elimination
How do serum creatinine and creatinine clearance change in the elderly?
-Serum creatinine does not change
-Even though GFR is reduced, muscle mass also declines with age, so less creatinine is produced
-Creatinine clearance however, is decreased
How does the production of plasma proteins change in the elderly?
-Alpha-1-acid glycoprotein increase
-Albumin production decreases
-Pseudocholinesterase production decreases
How does circulation time change in the elderly?
-Circulation time increases, reduced CO prolongs the time of drug delivery
-Slower IV induction, faster inhalation induction
How does lean body mass change in the elderly?
-Why is this important?
Lean body mass decreases as a function of reduced muscle mass
-Decreased blood volume
-Decreased plasma volume
-Decreased neuromuscular reserve
*Hypothermia sets in faster
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