ANAESTHESIA FOR PREMATURE AND EX-PREMATURE BABIES

MODERATOR: DR. PRASANNA

DR. SANTHALAKSHMI DR. KANCHAN

DEFINITION

Preterm: Born before 37 weeks GA

INCIDENCE

• 10-12 % of Indian Babies

• 5-7 % in the West

CAUSES OF PRETERM DELIVERY

SpontaneousPoor socio-economic status

Systemic maternal disease

APH

Cervical incompetence

Infection

Past history

Smoking

Threatened Abortion

Stress

Sexual activity

Trauma

Uterine malformations

Multiple pregnancy

InducedMaternal DM

Placental dysfunction

Eclampsia

Fetal hypoxia

APH

Iso-immunization

HOW TO RECOGNISE A PRETERM BABY?Head circumference < 33cm

>3cm greater than chest circumference

Poor activity, sluggish reflexes

Extended posture due to poor tone

Sutures widely separated, fontanel large

Shallow orbit, absent buccal fat

Ear catilage- poor recoil

Hair- fuzzy, separate strands

Skin- thin, gelatenous, shiny, abundant lanugo, very less vernix caseosa

Edema +/-

Deficient Subcutaeous fat

Breast nodule small/ absent

Sole creases ill-defined

Testes undescended

Labia majora widely separated

PHYSIOLOGICAL HANDICAPS

CNS

• Lethargy

• Poor cough reflex

• Incoordinated sucking and swallowing in babies <35 weeks GA

More resistant to toxic effects of hypoxia compared to term babies

Intraventricular-periventricular hemorrhage, leucomalacia

↓ Vit K

Capillary fragility

RESPIRATORY SYSTEM

28-36 weeks: Terminal air sacs and capillaries

36 weeks GA to 18 months of age: Alveolar phase

Type II pneumocytes identifies after 22-26 weeks GA

but the osmophilic lamellar bodies (surfactant) prominent only after 34 weeks

< 26 Weeks Cuboidal alveolar lining

Resuscitation difficulties at birth

Large Deadspace/ tidal volume ratio

Diaphragmatic breathing (more fatiguable)

Periodic

Intercostal-recessions

RESPIRATORY SYSTEM

Response to Hypoxia

The sensitivity of an infant's ventilatory response to carbon dioxide increases with postnatal and gestational age

Hyaline Membrane Disease/ RDS

Onset < 6hours

Tachypnea

Retractions

Grunting

Oxygen desaturation

RDS Chest X ray

Diffuse reticulonodular pattern with air bronchogram

Uncomplicated clinical course

Peak by 2-3 days

Resolution begins at ~72 hours

Surfactant Administration

Intra-tracheal

<28 weeks

2nd Dose 12 hours later

3rd Dose if required in mechanically ventilated patients

Chronic Lung Disease

RDS Repair process• Parenchymal fibrosis

• Chronic inflammation

• Airway epithelial metaplasia

• Smooth muscle hypertrophy

Bronchopulmonary Dysplasia

Mechanical ventilation during >3 days during the 1st week of life

Persistence of O2 dependence after 28 days

Radiographic abnormalities characterized by patchy density with areas of hyperlucency

Non-homogenous lung parenchyma Densities secondary to volume loss due to fibrosis Cystic emphysema, Hyperinflation

Chronic Lung Disease

BPD and Chorioamnionitis

Yoon and others (1999) noted that chorioamnionitis was easily detected in 92% of the placentas from preterm infants who developed BPD and 62% of those who did not

IL-1β, IL-6, and IL-8 were in the amniotic fluid within 5 days of preterm delivery

BPD and Mechanical Ventilation

The influx of granulocytes into the alveoli of preterm infants after mechanical ventilation has been measured as soon as 1 hour of age; these infants have a higher incidence of BPD ( Ferreira et al., 2000 )

New BPD

Causes:

Premature stage of lung development

Artificial surfactant and prenatal steroid less severe RDS

Later oxygen dependance, CLD

Abnormal growth of alveoli and vasculature

Characteristic firbroproliferative BPD pattern NOT seen

NEW BPD•Fine, hazy, uniform parenchymal pattern

•Modest hyperinflation

•Arrested development

CVSDelayed DA closure

• 1/3 of patients <34 weeks GA +/- CHF• ↑ in patients with HMD, Protracted Hypoxia

Thrombo-embolic complications due to indwelling venous and arterial catheters

Iatrogenic anemia due to repeated blood sampling

GASTROINTESTINAL SYSTEM

Poor, incoordinated suckling

Regurgitation, Aspiration

Small Stomach

Incompetent cardioesophageal junction

Necrotising enterocolitis

NEC• Preterm baby weighing less than 2500 g• Infants with NEC may be acidotic, hypoxic, hypothermic, and in shock• Bowel perforation surgery

THERMOREGULATION

Reduced or absent subcutaneous fat

Reduced or absent BROWN fat

Greater body surface area for heat loss

Immature thermostat

FLUID AND ELECTROLYTES

Impaired urine concentrating ability: hypotonicity of the renal medulla

Dehydration

Hyponatremia: prolonged glomerulotubular imbalance

GFR is high relative to tubular capacity to reabsorb Na+

Hypocalcemia: related to decreased PTH secretion

PERINATAL PROBLEMS ACCORDING TO INFANTS’

GESTATIONAL AGE

Near-Term Infants (35 to 37 weeks gestation)

Delay in establishing full feeds

Hyperbilirubineamia

IDM- Pulmonary immaturity

30 to 34 Weeks Gestation

RDS/ HMDPneumothoraxIntestitial emphysemaChronic Lung Disease Iatrogenic blood loss (sampling)

New BPDVariations of CLD

Temperature instability

Hypoglycemia

Hypocalcemia

NEC (esp. with co-existing PDA)

PDA (20-30%)

Intracerebral bleed

Apnea

27 to 29 Weeks Gestation

Fragile skin

Absent subcutaneous fat

Transcutaneous fluid loss

Perioperative Apnea

Less Than 26 Weeks Gestation

“on the edge of survivability”

Intracranial haemorrhage

Pulmonary insufficiency, Apnea

THANK YOU!