Chp 36 Neonatal Anesthesia

Question 1

Definition of a neonate

Answer 1

Newborn animal up to 6-8wks old
Up to 3mo generally considered neo/ped
Higher risk –> require special attention to needs of immature patient

Question 2

What special about 3mo of age?

Answer 2

By 12wks, the major systems (CV, pulmonary, thermoregulatory, renal, hepatic) well developed
-Gradually mature with majority of systems developed by 6-8wks

Question 3

Different about CV in neonate?

Answer 3

• More dependent on HR for CO than adults
• Less functional contractile tissue –> changes in CO mediated by changes in rate rather than contractility
• Resting cardiac index of neonates higher than adults so very little cardiac reserve
• Immature SNS –> decreased baroreceptor reflex –> poor vasomotor regulation

Question 4

Different about rest system in neonate?

Answer 4

• High resting RR, MV secondary to increased oxygen demand
• Small airways more prone to obstruction
• Closing volume much smaller vs adults
• Increased potential for hypoxia during apnea/obstruction
• Pliable rib cage –> increased work of breathing –> earlier resp fatigue, esp in cases of resp disease

Question 5

Are other systems immature in the neonate?

Answer 5

• Immature SNS
• Decreased ability to respond to stress of ax
• Renal function not fully developed
• Deficient hepatic microsomal enzymes –> prolonged elimination, effect of drugs

Question 6

What is closing volume?

Answer 6

Volume where alveoli close

Question 7

Are neonates more susceptible to hypothermia?

Answer 7

• Typically have less body fat compared to the adult
• Immature thermoregulatory control
• Large ratio of surface to area mass

Question 8

Ways to maintain body temp in the neonate

Answer 8

Warm-water circulating blankets
Increased room temp
Expeditious surgical, anesthesia times
Warmed fluids

Question 9

Do neonates feel pain?

Answer 9

YES!

• pathologic pain detrimental to development
• Local anesthetic, opioids indicated for procedures considered to be painful in the adult

Question 10

What are common premeds for neonates?

Answer 10

Benzos +/- opioids
Opioids have very little effect on contractility but may reduce HR so should have atropine, glyco on standby
Very young patient, benzo with opioid = very good sdation

Question 11

How do neonates react to preanesthetic, anesthetic drugs?

Answer 11

• BBB typically more permeable –> exaggerated responses to medications may be seen if adult doses are given
• High volume of distribution bc of large EC vol vs adults
• Decreased protein binding of drugs, decreased metabolism –> exaggerated responses
• Prudent to reduce dose of sedatives, tranquilizers and to administer anesthetics to effect in the neonatal patient

Question 12

Acepromazine in neonates

Answer 12

• Significant hypotension
• Heat loss due to vasodilation
• Nonreversible
• Require extensive hepatic metabolism, renal clearance
• Prolonged and exaggerated effects

Question 13

alpha 2s in neonates

Answer 13

• Can cause significant bradyarrhythmias, dramatic after load increases
• Require extensive hepatic metabolism, renal clearance
• Prolonged and exaggerated effects

Question 14

Induction of neonates

Answer 14

• Most common method = induction via mask, chamber
• Foals can be induced with inhalant via NTT
• Iso, sevo
• Maintenance of anesthesia usually gas via mask or connection to a circuit after ET intubation

Question 15

Venous access in a neonate?

Answer 15

Standard over the needle IVC
Typical sites - saphenous, jugular, cephalic
IO cats in which veins are too small or otherwise inaccessible

Question 16

How do I intubate a neonate?

Answer 16

• Large tongues, wide flat mouth
• Tend to be nasal breathers –> palate therefore may block glottis from view
• Laryngoscope w small blade, ETT 2.0 or 2.5
• Stylet should not extend past tip of tube
• Large IVC with needle removed may be useful if tubes are too big
• Important to minimize/reduce mechanical dead space as much as possible
• Foals = relatively easy to NTT intubate - can swap to OTT if desired when induced

Question 17

Can I use the same anesthesia circuit for neonates that I use for adults?

Answer 17

• Non-rebreathing circuit (Bain circuit, Jackson-Reese circuit) should be used on neonates to reduce work of breathing
• Circuits not as good at maintaining body heat so extra care has to be taken to preserve body heat
• High flow rates (200-300mL/kg/min) also put animal at risk for barotrauma more quickly if APL valve closed
• Foals <110kg usually placed on SA circuit

Question 18

Are injectable anesthetics used in neonates?

Answer 18

• Extensive metabolism required to excrete drugs
• Redistribution typically results in termination of anesthetic effects
• Prolonged recoveries +/- sedation may result
• Propofol used with success in foals

Question 19

Fluids?

Answer 19

• Care must be taken to avoid volume overload

- Typically 5-10mL/kg/hr of LRS or 0.9% NaCl with dextrose (2.5-5.0%) administered IV or IO