Preterm infant
anesthetic implications
Dr. Varun kumar varshney
 Premature babies - born before 37 weeks
 Gestational Age determines the extent of
physiological immaturity.
Respiratory system
• ALVEOLI develop 17-28 WKS
• Pulmonary capillaries 28-36 wks
• Before 32-34 wks surfactant deficeint
m...
CONTROL OF RESPIRATION /APNOEA
• Chemoreceptor blunted response
• Normal biphasic response to hypoxaemia
replaced by apnoe...
• Preterm - 10% type 1 fibre diaphragm and intercostal muscles
(25% term)
apnoea at time of physiological stress.
• After ...
Anatomical differences
 Large occiput
 Large sized tongue
 Larynx : more cephalic, funnel shape
 Epiglottis : short, s...
Anaesthetic considerations
• No doughnut is required
• Straight blades preferred
 Tube that easily passes the vocal cords
may be tight in the subglottic region
 Uncuffed tubes preferred
 Cuffed tubes ...
• Airway
Highly compliant
• Chest wall
 Lungs : non compliant
 Alveoli thick walled at birth
 Dead space ventilation si...
 Weaker intercostal muscles,diaphragm
 Horizontal , pliable ribs
 Protruberant abdomen
 Diaphragmatic and intercostal ...
Anaesthetic considerations
 Limited respiratory reserve
 Horizontal ribs prevent ‘bucket handle’ action
seen in adult br...
 Chest wall more compliant : low FRC
 FRC decreases with apnoea , anaesthesia causing lung
collapse
 Closing volume lar...
 CPAP during spontaneous ventilation improves
oxygenation and decreases work of breathing
 Apnoea common post op in prem...
Cardiovascular system
 Stroke volume - fixed by noncompliant and immature LV
 CO sensitive to HR changes
 Activation of...
 Sympathetic nervous system
 Baroreceptor reflexes
Blunted response to exogenous catecholamines
Immature heart -- more...
• DUCTUS ARTERIOSUS- remain patent
• Flip flop circulation.
• Left---rt circulation.
increased pulmonary flow.
congestive ...
Anaesthetic Implications
 Bradycardia associated with hypoxia : treat with oxygen
and ventilation initially
 Patent duct...
 Neonatal pulmonary vasculature reacts to rise in Pa02 and
pH and fall in PaCO2 at birth
 Alterations in pressure and wi...
A term baby has 18–20 g /dl of haemoglobin (Hb);
in prematurity, this can be 13–15 g/ dl,
70–80% of which is HbF.
•Fetal H...
•This compensation is much less in the preterm baby.
A target haematocrit of 40–45% facilitates oxygen delivery; this
may ...
Metabolism and temperature
regulation
 Vulnerable to hypothermia
 Large body surface area to weight ratio
 thin skin (n...
Low body temperature
 Respiratory depression
 Acidosis
 Decreased cardiac output
 Increased duration of action of drug...
Anaesthetic considerations
 Heat lost during anaesthesia mostly via radiation
 Also by conduction, convection and evapor...
Peri-operative heat loss is vital
 Placing baby on warming mattress and warming the surgical
unit (80° F or warmer) : con...
 Hot air blankets : most
effective means of
warming children
 Anesthetics alter many
thermoregulatory
mechanisms, partic...
Kidneys
 Renal function diminished due to
-Small perfusion pressures
-Immature glomerular Fxn
-Immature tubular function
...
• Preterm infants impaired ability to concentrate urine, so
cannot tolerate under and over hydration.
• They are unable to...
Liver
 Functional maturity of the liver- incomplete
 Metabolic enzyme developed but not inducible.
 With growth of infa...
 CYP3A : present at adult values at birth
 Other cytochromes absent or reduced
 Phase II reactions : involve conjugatio...
 Preterm infant’s liver - minimal glycogen stores
 Unable to manage large protein loads
 Thus increased tendency :
 hy...
GIT
 Birth -- gastric pH is alkalotic
 Day 2 -- pH in normal physiologic range
 Coordination of swallowing with respira...
Glucose metabolism
 Hypoglycaemia : common in preterm
less glycogen store
underdeveloped glucogenic pathway.
 May lead t...
 Neonates - appreciate pain
(increased HR , BP , neuro-endocrine response)
 Narcotics depress the ventilation response t...
• Intraventricular haemorrhage
occurs in 25% of very low birth weight infants
within the first 72 hours of life.
Intrav...
• Recently anaesthetic agents effect on the developing
brain leading to later memory and learning impairment.
• SO, only e...
 Cerebral vessels in preterm infant : thin walled, fragile--
intraventricular haemorrhages
Risk increased
 Hypoxia
 Hyp...
Retinopathy of prematurity
More common in preterm infants
• cause vasoconstriction of retinal vessels
high concentrations ...
Total body water -- preterm infants > term infant
Water soluble drug - large Vd - requires large loading dose
(antibioti...
Inhaled anaesthetics
 Small safety margin between anaesthetic overdose
and inadequate depth of anaesthesia
 Anaesthetic ...
Non volatile anaesthetics
Larger doses of Propofol –
large Vd
Shorter elimination t1/2
Higher plasma clearance
“Propo...
 Thiopental : larger dose in children
- Shorter elimination t1/2
- Greater plasma clearance
 Neonate ( 3-4mg/kg)
- Less ...
Opioids
More potent in preterm
 Easier entry across BBB
 Decreased metabolic capability
 Increased sensitivity of respi...
PRE-OP ASSESSMENT
Detailed history from both the parents .
Points to be asked-
• Gestational age at birth and the current ...
Preoperative fasting
 Greater risk for aspiration –
 Low gastric pH
 High residual volumes
Type Fasting time (hrs)
Clea...
• ADVANTAGES OF THESE LIBERAL GUIDELINES-
- Prevent dehydration and hypoglycemia
- Reduce the risk of aspiration
.
Cont….
Recent investigations
• haemoglobin,
• haematocrit,
• platelets count,
• electrolytes
• coagulation profile
Cont….
A crossmatch should be taken where blood loss
is anticipated to be greater than 10% of blood volume.
All premature babies ...
-
Premedication is not required
However, atropine should be considered to pre-empt
transient bradycardia
INTRA-OPERATIVE MANAGEMENT
• The PRETERM may already be intubated and
ventilated prior to arrival in the operating theatre...
• An orogastric tube is useful after intubation
to decompress the stomach and to minimise
splinting of the diaphragm and f...
• For pain, Paracetamol is commonly used.
• NSAIDs for analgesia are C/I due to renal
immaturity.
• NSAIDs may cause prema...
• Where opiates are necessary, short acting such as fentanyl.
• The use of local anaesthetic techniques is encouraged
 lo...
Theatre/equipment
• Should have all the necessary equipment and staff for this.
• Ideally 2 oxygen saturation probes
• one...
• The theatre pre-warmed to achieve a temperature 25°C.
Active warming by such as overhead heaters should be used
as well ...
• Blood glucose closely monitored.
• a widely accepted cut off is a blood sugar of <2.6mmol/L.
• Glucose can be given as a...
Extubation
 Plan for awake intubation
 Return of gag reflex
 Responsive and purposeful
 Regular respiration
FLUID MANAGEMENT
• Ideally, fluid
acid–base, electrolyte corrected before reaching ot
Hb deficits should be
• The estimate...
• Preterm infants often receive a glucose-containing solution
to maintain normoglycaemia continue during surgery.
• Estima...
• As a transfusion guideline, the volume of packed cells
required(ml)=desired increment in Hb (g dl21)*weight (kg)*3
• Pla...
• Third-space losses 1–2 ml/ kg/hfor superficial surgery,
4–7 ml /kg/ hfor thoracotomy, and
5–10 ml/ kg /hfor abdominal su...
• Hypotension, diminished heart sounds, tachycardia,
increased core-peripheral temperature gradient, and
delayed capillary...
• If an arterial line is in situ, the position of
the dicrotic notch and the area under
the arterial waveform can give val...
PRBC
MABL = EBV * Starting haematocrit – Target haematocrit
Starting haematocrit
Blood volume
Preterm : 120ml/kg
Term :...
POST-OPERATIVE CARE
 A decision whether to extubate or not????
 consider the preoperative state of the baby
type of surg...
 period. apnoea-major concern
 Premature babies under 60 weeks gestational age
need high dependency unit for at least 12...
 Continuous apnoea alarm monitoring must be available
 IV caffeine at 10mg/kg
 CPAP may well be useful at this stage
THANK YOU…..
Preterm anesthetic consideration
of 68

Preterm anesthetic consideration

anesthetic implications in preterm
Published on: Mar 4, 2016
Published in: Health & Medicine      
Source: www.slideshare.net


Transcripts - Preterm anesthetic consideration

  • 1. Preterm infant anesthetic implications Dr. Varun kumar varshney
  • 2.  Premature babies - born before 37 weeks  Gestational Age determines the extent of physiological immaturity.
  • 3. Respiratory system • ALVEOLI develop 17-28 WKS • Pulmonary capillaries 28-36 wks • Before 32-34 wks surfactant deficeint more prone to RDS • mechanical ventilation • more than 28 days of oxygen supplementation BPD
  • 4. CONTROL OF RESPIRATION /APNOEA • Chemoreceptor blunted response • Normal biphasic response to hypoxaemia replaced by apnoea. • incidence higher in preterm. • Apnoea pause more than 20 sec alone or less than 20 sec + bradycardia
  • 5. • Preterm - 10% type 1 fibre diaphragm and intercostal muscles (25% term) apnoea at time of physiological stress. • After operation, apnoeas are frequent in the first 12 h and can continue until 48–72 h.
  • 6. Anatomical differences  Large occiput  Large sized tongue  Larynx : more cephalic, funnel shape  Epiglottis : short, stubby, omega shaped, angled over laryngeal inlet  Vocal cords angled Cricoid cartilage : Narrowest portion
  • 7. Anaesthetic considerations • No doughnut is required • Straight blades preferred
  • 8.  Tube that easily passes the vocal cords may be tight in the subglottic region  Uncuffed tubes preferred  Cuffed tubes : leak maintained around cuff (with or without inflation) to prevent trauma resulting in subglottic oedema and subsequent post-extubation stridor.
  • 9. • Airway Highly compliant • Chest wall  Lungs : non compliant  Alveoli thick walled at birth  Dead space ventilation similar to adults  Oxygen consumption 2-3 times higher  Work of breathing 3 times that in adults ---- increased by cold stress / airway obstruction  Hypoxic and hypercapnic drives not well developed Depress respiration in these patients
  • 10.  Weaker intercostal muscles,diaphragm  Horizontal , pliable ribs  Protruberant abdomen  Diaphragmatic and intercostal muscles Low type 1 muscle fibres – ability to perform repeated exercise • Early fatigue • Desaturation
  • 11. Anaesthetic considerations  Limited respiratory reserve  Horizontal ribs prevent ‘bucket handle’ action seen in adult breathing : limit increase in VT  Ventilation primarily diaphragmatic  Bulky abdominal organs , stomach filled with gases from poor bag mask ventilation – impinge on contents of the chest , splint diaphragm reducing adequate ventilation
  • 12.  Chest wall more compliant : low FRC  FRC decreases with apnoea , anaesthesia causing lung collapse  Closing volume larger than FRC until 6-8 years Causes an increased tendency for airway closure at end expiration. Thus, neonates generally need IPPV during anaesthesia and would benefit from a higher respiratory rate and the use of PEEP.
  • 13.  CPAP during spontaneous ventilation improves oxygenation and decreases work of breathing  Apnoea common post op in premature infants
  • 14. Cardiovascular system  Stroke volume - fixed by noncompliant and immature LV  CO sensitive to HR changes  Activation of parasympathetic nervous system, anesthetic overdose, or hypoxia -- trigger bradycardia -- profound reductions in CO
  • 15.  Sympathetic nervous system  Baroreceptor reflexes Blunted response to exogenous catecholamines Immature heart -- more sensitive to depression by volatile anesthetics and opioid-induced bradycardia Not fully mature
  • 16. • DUCTUS ARTERIOSUS- remain patent • Flip flop circulation. • Left---rt circulation. increased pulmonary flow. congestive cardiac failure.
  • 17. Anaesthetic Implications  Bradycardia associated with hypoxia : treat with oxygen and ventilation initially  Patent ductus contracts in 1st few days of life fibrose within 2-4 weeks  Closure of foramen ovale is pressure dependent closes in the first day of life
  • 18.  Neonatal pulmonary vasculature reacts to rise in Pa02 and pH and fall in PaCO2 at birth  Alterations in pressure and with response to hypoxia and acidosis : reversion to transitional circulation may occur in the first few weeks after birth.
  • 19. A term baby has 18–20 g /dl of haemoglobin (Hb); in prematurity, this can be 13–15 g/ dl, 70–80% of which is HbF. •Fetal Hb has a reduced ability to release oxygen; •Compensation the relatively high blood volume, Hb concentration, and cardiac output . Haematology
  • 20. •This compensation is much less in the preterm baby. A target haematocrit of 40–45% facilitates oxygen delivery; this may necessitate earlier perioperative blood transfusion EARLY BLOOD TRANSFUSION TARGET HAEMOCRIT 40-45%
  • 21. Metabolism and temperature regulation  Vulnerable to hypothermia  Large body surface area to weight ratio  thin skin (non keratinized)  decrease brown fat (nonshivering thermogenesis) PREVENT HYPOTHERMIA
  • 22. Low body temperature  Respiratory depression  Acidosis  Decreased cardiac output  Increased duration of action of drugs  Decrease in platelet function  Increase in the risk of infection
  • 23. Anaesthetic considerations  Heat lost during anaesthesia mostly via radiation  Also by conduction, convection and evaporation  Optimal ambient temperature to prevent heat loss 34ºC for premature infant 32ºC for neonates 28ºC in adolescents and adults.
  • 24. Peri-operative heat loss is vital  Placing baby on warming mattress and warming the surgical unit (80° F or warmer) : conduction  Keeping infant in incubator and covered with blankets : convection. Cover head too.  Evaporation : humidification of inspired gases, use of plastic wrap to decrease water loss through skin, warming of skin disinfectant solutions.
  • 25.  Hot air blankets : most effective means of warming children  Anesthetics alter many thermoregulatory mechanisms, particularly nonshivering thermogenesis in neonates. AVOID OVERHEATING!
  • 26. Kidneys  Renal function diminished due to -Small perfusion pressures -Immature glomerular Fxn -Immature tubular function  Nearly complete maturation -- ≈ 20 weeks after birth  Complete maturation -- 2 years of age  Free water and solute clearance impaired in PRETERM  More prone to dehydration  T1/2 of medications -prolonged (antibiotics)
  • 27. • Preterm infants impaired ability to concentrate urine, so cannot tolerate under and over hydration. • They are unable to retain sodium prone to hyponatraemia. • Water loss is common in preterm infants due to the large body surface area and thin skin, particularly in the first few days of life. prone to hyponatraemia.
  • 28. Liver  Functional maturity of the liver- incomplete  Metabolic enzyme developed but not inducible.  With growth of infant ability to metabolize medications ↑ (1) Hepatic blood flow ↑, more drug delivered (2) Enzyme systems develop , induced  Cytochrome P450 system ≈ 50% adult values at birth.
  • 29.  CYP3A : present at adult values at birth  Other cytochromes absent or reduced  Phase II reactions : involve conjugation to facilitate renal excretion  Often impaired in neonates(preterm)  Jaundice (decreased bilirubin breakdown)  long drug t1/2 the half-life of morphine and benzodiazepines is several days
  • 30.  Preterm infant’s liver - minimal glycogen stores  Unable to manage large protein loads  Thus increased tendency :  hypoglycemia  acidemia  failure to gain weight when diet contains too much protein
  • 31. GIT  Birth -- gastric pH is alkalotic  Day 2 -- pH in normal physiologic range  Coordination of swallowing with respiration under developed in preterm  High incidence of gastroesophageal reflux
  • 32. Glucose metabolism  Hypoglycaemia : common in preterm less glycogen store underdeveloped glucogenic pathway.  May lead to neurological damage  Glucose levels : monitored regularly .  Infusion of 10% glucose may be used.
  • 33.  Neonates - appreciate pain (increased HR , BP , neuro-endocrine response)  Narcotics depress the ventilation response to a rise in PaC02.  BBB poorly formed : barbiturates, opioids, antibiotics and bilirubin cross --- prolonged duration of action Central nervous system
  • 34. • Intraventricular haemorrhage occurs in 25% of very low birth weight infants within the first 72 hours of life. Intraventricular haemorrhage complicated by ventricular dilation, progress to hydrocephalus.
  • 35. • Recently anaesthetic agents effect on the developing brain leading to later memory and learning impairment. • SO, only essential surgery should be performed in early life. Ketamine should probably be avoided in premature babies
  • 36.  Cerebral vessels in preterm infant : thin walled, fragile-- intraventricular haemorrhages Risk increased  Hypoxia  Hypercarbia  Hypernatraemia  Low haematocrit  Awake airway manipulations
  • 37. Retinopathy of prematurity More common in preterm infants • cause vasoconstriction of retinal vessels high concentrations of supplemental oxygen, • lead to retinal detachment, fibrosis blindness in children, • prevented avoiding exposure to high concentration of 02.
  • 38. Total body water -- preterm infants > term infant Water soluble drug - large Vd - requires large loading dose (antibiotics, succinylcholine) Fat , muscle content ↑ with age  Drug redistributing into fat have long clinical effect  Drug redistributing into muscle
  • 39. Inhaled anaesthetics  Small safety margin between anaesthetic overdose and inadequate depth of anaesthesia  Anaesthetic requirement preterm < term neonates .  Infants : higher MAC than older children or adults  Uptake more rapid : increased RR , CI
  • 40. Non volatile anaesthetics Larger doses of Propofol – large Vd Shorter elimination t1/2 Higher plasma clearance “Propofol infusion syndrome” (>48hrs duration , >5mg/kg/h)
  • 41.  Thiopental : larger dose in children - Shorter elimination t1/2 - Greater plasma clearance  Neonate ( 3-4mg/kg) - Less protein binding -Longer t1/2 -Impaired clearance
  • 42. Opioids More potent in preterm  Easier entry across BBB  Decreased metabolic capability  Increased sensitivity of respiratory centers
  • 43. PRE-OP ASSESSMENT Detailed history from both the parents . Points to be asked- • Gestational age at birth and the current gestational age • Weight • Periods and duration of mechanical ventilation, oxygen therapy. • Apnoeas – frequency, duration, possible triggers • Co-morbidities, particularly cardiac
  • 44. Preoperative fasting  Greater risk for aspiration –  Low gastric pH  High residual volumes Type Fasting time (hrs) Clear liquids 2 Breast milk 4 Infant formula 6 Solid (fatty or fried) foods 8
  • 45. • ADVANTAGES OF THESE LIBERAL GUIDELINES- - Prevent dehydration and hypoglycemia - Reduce the risk of aspiration . Cont….
  • 46. Recent investigations • haemoglobin, • haematocrit, • platelets count, • electrolytes • coagulation profile Cont….
  • 47. A crossmatch should be taken where blood loss is anticipated to be greater than 10% of blood volume. All premature babies should have an echocardiogram performed before surgery
  • 48. - Premedication is not required However, atropine should be considered to pre-empt transient bradycardia
  • 49. INTRA-OPERATIVE MANAGEMENT • The PRETERM may already be intubated and ventilated prior to arrival in the operating theatre. • A range of uncuffed tubes should be available. • If the infant has undergone prolonged ventilation, there is a possibility of subglottic stenosis.
  • 50. • An orogastric tube is useful after intubation to decompress the stomach and to minimise splinting of the diaphragm and facilitate ventilation. • AVOID excessive oxygen concentrations predispose to retinopathy of prematurity. • A balanced anaesthetic technique should be used Cont….
  • 51. • For pain, Paracetamol is commonly used. • NSAIDs for analgesia are C/I due to renal immaturity. • NSAIDs may cause premature closure of a PDA. Cont….
  • 52. • Where opiates are necessary, short acting such as fentanyl. • The use of local anaesthetic techniques is encouraged  local infiltration by the surgeon or  caudal, epidural or spinal.
  • 53. Theatre/equipment • Should have all the necessary equipment and staff for this. • Ideally 2 oxygen saturation probes • one on the right hand and • one on the lower limb to compare pre ductal and post ductal levels. • ECG via neonatal electrodes, non-invasive blood pressure, capnography and temperature monitoring are mandatory.
  • 54. • The theatre pre-warmed to achieve a temperature 25°C. Active warming by such as overhead heaters should be used as well as a paediatric heat moisture exchange. • All fluid and blood products warmed prior • irrigation fluid is warmed prior to use. • prevent unnecessary exposure. • Surgical drapes lightweight, preferably plastic allow the baby to be clearly seen. Cont….
  • 55. • Blood glucose closely monitored. • a widely accepted cut off is a blood sugar of <2.6mmol/L. • Glucose can be given as a bolus of 1-2ml/kg of 10% glucose. • Regular blood sugars should be checked in order to confirm nomal glucose level Cont….
  • 56. Extubation  Plan for awake intubation  Return of gag reflex  Responsive and purposeful  Regular respiration
  • 57. FLUID MANAGEMENT • Ideally, fluid acid–base, electrolyte corrected before reaching ot Hb deficits should be • The estimated maintenance fluid requirement of a preterm infant is 100 ml /kg/24 h21. • During surgery, the maintenance fluid should be isotonic (e.g. Hartmann’s solution, 0.9% sodium chloride).9
  • 58. • Preterm infants often receive a glucose-containing solution to maintain normoglycaemia continue during surgery. • Estimation of blood loss can be difficult • replacement can be guided by capillary Hb and haematocrit perceived ongoing and anticipated losses, and cardiorespiratory status. • The extremely premature and those with cyanotic heart disease need a haematocrit of 35–40% to maintain oxygenation.
  • 59. • As a transfusion guideline, the volume of packed cells required(ml)=desired increment in Hb (g dl21)*weight (kg)*3 • Platelets and fresh frozen plasma is given as 10–20 ml /kg21, and cryoprecipitate as 5–10 ml /kg21.
  • 60. • Third-space losses 1–2 ml/ kg/hfor superficial surgery, 4–7 ml /kg/ hfor thoracotomy, and 5–10 ml/ kg /hfor abdominal surgery.9
  • 61. • Hypotension, diminished heart sounds, tachycardia, increased core-peripheral temperature gradient, and delayed capillary refill suggest fluid depletion. • Urine output is a good indicator of fluid status and perfusion; an output of 0.5–2 ml/kg /h is the norm. • However, monitoring such small volumes is difficult.
  • 62. • If an arterial line is in situ, the position of the dicrotic notch and the area under the arterial waveform can give valuable information to guide fluids. • Care must be taken during drug injections not to introduce air bubbles into the circulation Which may traverse right-to-left shunts. As little as 0.2–0.4 ml kg can BE DANGEROUS
  • 63. PRBC MABL = EBV * Starting haematocrit – Target haematocrit Starting haematocrit Blood volume Preterm : 120ml/kg Term : 90ml/kg Child(3-12mths) : 70-80ml/kg Child (›1yr) : 70ml/kg
  • 64. POST-OPERATIVE CARE  A decision whether to extubate or not????  consider the preoperative state of the baby type of surgery performed.  If plans extubate, fully awake and managing adequate tidal volumes without support.
  • 65.  period. apnoea-major concern  Premature babies under 60 weeks gestational age need high dependency unit for at least 12 hours and for a further 12 hours following any apnoeic Cont….
  • 66.  Continuous apnoea alarm monitoring must be available  IV caffeine at 10mg/kg  CPAP may well be useful at this stage
  • 67. THANK YOU…..

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