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Pathophys II > Pediatric & Neonatal anesthesia pathophysiology Part 2 > Flashcards

Pediatric & Neonatal anesthesia pathophysiology Part 2 Flashcards

1
Q

Fetal circulation is characterized by

A

high PVR secondary to fluid filled lungs

- low systemic vascular resistance secondary to the large surface area of the low resistance utero-placental bed

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2
Q

The most oxygenated blood from the umbilical vein perfuses the

A

brain and heart by shunting across the liver via the ductus venosus and shunting across the right heart via the foramen ovale***

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3
Q

The umbilical vein PaO2 is

A

30-35 mmHg

-oxygen transport exists in relatively hypoxic environment

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4
Q

Fetal hemoglobin maintains the oxygen content of blood (CaO2) via two mechanism:

A

hgb F is left shifted and is more saturated than adult Hgb
hemoglobin levels in utero are elevated which also raises the CaO2
- the effect of left shifted hgb F** and polycythemia produce an oxygen carrying capacity in the fetus that nearly equal to adults

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5
Q

Transition from fetal to adult circulation occurs with

A

clamping of the umbilical cord and inflation of the lungs

-cord clamping removes the low resistance placenta and raises SVR

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6
Q

Lung inflation and increased PaO2 dramatically lowers

A

the PVR
- when the lungs expand and fill with gas pulmonary vascular resistance (PVR) decreases***** as a result of mechanical effects on the vessels and relaxation of vasomotor tone

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7
Q

As PVR decreases, blood flow increases to the lungs, then blood flows into the left atrium increases via the pulmonary veins,

A

increasing LA pressure over RA pressure closes the atrial septum over the foramen ovale***

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8
Q

Placenta clamp ceases flow from this large, low-resistance vascular bed. This results in an

A

increase in SVR and a decrease in inferior vena cava blood flow and right atrium pressure

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9
Q

This increase in SVR and aortic pressure above the pulmonary artery pressure results in

A

reverse flow through the ductus arteriosus*****

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10
Q

The increase in oxygen concentration leads to a __________ causing closure of the ductus arteriosus

A

decrease in prostaglandins**

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11
Q

_______ closes the flap of tissue covering the patent foramen ovale

A

when left atrial pressure rises above right atrial pressure

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12
Q

Describe functional and anatomic closure of the foramen ovale.

A

functional- closure occurs quickly
anatomic- closure usually requires weeks
A PFO that is probe patent persists in 20-25% of adults

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13
Q

The ductus arteriosus remains patent in utero due to

A

hypoxia, mild acidosis, and placental prostaglandins

  • removal of these factors after delivery causes functional closure
  • the reverse flow pressure and increase in local PaO2 (>50-60 mmHg) causes the muscular wall of the ductus arteriosus to constrict
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14
Q

Permanent anatomic closure of the ductus arteriosus, is usually complete in

A

5-7 days*** but may persist until 3 weeks

delayed closure is common in premature infants (esp. <34 weeks)

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15
Q

A PDA often occurs in premature infants with

A

lung disease
- during the period before anatomic closure certain physiologic stressors (hypothermia, hypercarbia, acidosis, hypoxia, sepsis, raised PVR) can cause the newborn to revert to fetal circulation

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16
Q

Changes in systemic or pulmonary vascular resistance alter the direction of blood flow in patent ductus arteriosus, lead to

A

increase in PVR –> right to left shunting (bad)

can lead to congestive heart failure and low diastolic pressure

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17
Q

pulmonary edema from increased blood flow promotes (in patent ductus arteriosus)

A

pulmonary hypertension

-worsened with hypoxia, hypercarbia, acidosis, and hypothermia

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18
Q

Describe Pre ad post-ductal saturation monitoring:

A

preductal- pulse ox on the right hand
postductal- pulse ox on the lower limb
cerebral oximetry

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19
Q

Myelination of nerve fibers and cerebral cortex is

A

less incomplete and developed in premature infants

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20
Q

The blood brain barrier in the premature infant is

A

immature, rendering the developing brain more vulnerable to drugs or toxins

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21
Q

Neural pathways allowing for pain perception develop during

A

the first, second, and third trimesters

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22
Q

Developing cerebral vessels appear to be

A

more fragile than in the adult

cerebral auto-regulation is impaired in sick neonates and therefore blood flow is pressure dependent

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23
Q

Preterm infants have very fragile cerebral vessels- rupture leads to

A

intra-cerebral hemorrhage & intraventricular hemorrhage (IVH)***

24
Q

Predisposing factors for IVH include:

A

hypoxia, hypercarbia, hypernatremia, fluctuations in pressure, low HCT, over transfusion, rapid administration of hypertonic fluids (i.e. NaBicarb or dextrose)

25
Q

Intraventricular hemorrhage results in

A

spontaneous bleeding into and around the lateral ventricles of the brain

26
Q

Intraventricular hemorrhage may result from

A

RDS, hypoxia, acute BP alterations, trauma, acidosis, distress

27
Q

Symptoms of intraventricular hemorrhage include

A

hypotonia, apnea, seizures, loss of sucking reflex, bulging anterior fontanelle

28
Q

IVH can progress to

A

hydrocephalus, parenchymal infarction, periventricular matter injury

29
Q

_____ are high risk for IVH

A

small birth weight and preterm (as many as 1/3rd of micropremie infants)

30
Q

Retinopathy of prematurity is the

A

arrest of normal retinal vascular development in exchange for neovascularization and fibrous tissue formation in the retina

31
Q

Retinopathy of prematurity can lead to

A

retinal detachment and fibrosis

32
Q

The anesthesia saturation goal to prevent retinopathy of prematurity is

A

90-94%****

33
Q

ROP is associated with

A

low birth weight (<1000g), prematurity, oxygen exposure, apnea, blood transfusions, sepsis, CO2

34
Q

The infant retina continues to mature until

A

42-44 weeks

35
Q

________ may be more damaging than high oxygen tensions for patients with retinopathy of prematurity

A

fluctuating oxygen levels

36
Q

Pediatric patients have an increased risk for heat loss due to

A

large surface area per kg than adults, thin skin, lower fat content, and higher surface area

37
Q

The four routes of heat loss include

A

radiation>convection>evaporation>conduction***

38
Q

Heat producing mechanisms include

A
  • non-shivering thermogenesis during the first 3 months of life
  • metabolism of brown fat- shivering is severely limited in premature infants; thermogenesis is inhibited by volatile anesthetics
  • crying
  • movement
39
Q

What can be done to combat temperature loss for peds patients:

A

transport the child in an incubator or on a heating pad
warm the OR (78-80 degrees) & fluids
limit skin exposure
cover the child’s head
use of forced air devices & warmers at all times
heat lamps

40
Q

Hypothermia of pediatric patients can result in:

A 
delayed awakening from volatile anesthetics
cardiac instability
respiratory depression
increased pulmonary vascular resistance
altered drug response
41
Q

Volatiles & effect on temperature include

A

cutaneous vasodilation

- depress hypothalamus= reduction in already reduced ability to warm themselves

42
Q

Neonates have very low _______

A

glycogen & body fat stores

  • predisposed to hypoglycemia during stress (surgery)
  • however decreased insulin production with infusion of dextrose predisposes to hyperglycemia
43
Q

________ by the kidneys can work to offset low glycogen

A

impaired glucose excretion

44
Q

Neonates should be maintained on IV ____ when NPO and close monitoring of blood glucose is vital

A

dextrose

normoglycemia is 45-90 mg/dL

45
Q

In the premature infant, the renal system is

A

reduced
reduced ability to compensate for large swings in volume
renal clearance of drugs is reduced
reduced proximal tubular reabsorption of sodium and water

46
Q

Describe the the important factors related to reduced proximal tubular reabsorption of salt and water.

A

monitoring of sodium and free water requirements is important during critical illness

47
Q

Describe renal clearance of drugs being reduced.

A

ability to handle free water and solute loads may be impaired in neonates
half-life of medications excreted by GFR will be prolonged (i.e. antibiotics)

48
Q

At term, functional maturity of the liver is

A

somewhat incomplete

49
Q

The cytochrome P450 (phase 1 drug metabolism of liphophilic drugs) reaches

A

~50% adult values at birth

50
Q

Phase II are

A

impaired until ~1 year of age

51
Q

The hepatic system of the newborn has limited

A

glycogen stores
limited ability to handle large protein loads
& reduced albumin synthesis- greater levels of unbound drugs

52
Q

In utero, ____ is actively transported across the placenta

A

calcium

53
Q

After birth the infant relies on ________ for calcium

A

extracellular calcium & calcium reserves
however parathyroid function is not fully established, vitamin D stores may be inadequate, albumin and protein reserves are lower

54
Q

Anticipate hypocalcemia especially in preterm due to

A

severe neonatal illness and following blood transfusion

55
Q

Symptomatic hypocalcemia requires treatment with a slow infusion of either

A

calcium chloride or calcium gluconate

a central line is preferred as skin damage and sloughing may occur with calcium containing solutions administration

Pathophys II (43 decks)

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