Neonatal Surgical Emergencies

1

• Neonatal Surgical Emergencies

2
Neonatal Surgical Emergencies

• Review of neonatal physiology
• Review of neonatal pharmacology
• Review of some important diseases
• Whats new about the surgical emergency in the
  neonate?

3
Immature Physiology

• Much of the difference in the premature infant
  relates to immature physiology
• Physiologic differences affect
• Routine anesthetic management
• The effect of pathology on the infant
• Morbidity and mortality

4
Neonatal Cardiovascular Physiology

• Structure and function of the myocardium
• Intracardiac shunts
• Heart rate dependent cardiac output
• Autonomic tone and receptor capacity

5
Neonatal myocardium

• Relative lack of contractile elements
• Large amount of collagen noncontractile
• Neither right nor left ventricle is pressure
  tested in the fetal state
• Frank Starling curve is shifted

6
(No Transcript)
7
(No Transcript)
8
(No Transcript)
9
What does this mean?

• Neonatal ventricle not efficient as a pump
• Neonate responds poorly to rapid volume challenge
• Neonate responds poorly to increase in SVR

10
Shunts

• Placenta, Ductus arteriosus create low pressure
  circuit protects fetus from increased work
• Foramen Ovale protects pulmonary circuit in the
  fetal state
• Elimination of the placenta raises SVR
• Oxygen decreases PVR dramatically and closes the
  ductus

11
(No Transcript)
12
(No Transcript)
13
(No Transcript)
14
(No Transcript)
15
What does this mean?

• Vascular and intracardiac shunts are not
  anatomically closed
• Conditions of stress can reopen these shunts
  allowing flow of deoxygenated blood directly to
  left side of heart
• Emboli in the venous side can flow with relative
  ease to the arterial side

16
Heart rate and cardiac output

• Neonatal heart rate is high 120 to 140 bpm
• Cardiac output is also high response to ongoing
  metabolic work

17
What does this mean?

• Decreased HR reduces CO dramatically
• Increased HR also decreases cardiac output but
  in a variable fashion
• Therefore, HR should remain as close to baseline
  as possible

18
Autonomic tone and receptor capacity

• Sympathetic receptors not well developed in the
  newborn
• Parasympathetic receptors well developed

19
What?

• Response to stress likely to lead to a
  parasympathetic discharge causing a decrease in
  heart rate and cardiac output
• Use of direct acting sympathetic stimulants for
  the support of circulation may not be successful

20
Neonatal respiratory physiology

• Immature response to hypoxia
• Immature response to elevations in carbon dioxide
• Apnea as a response to all stressors
• Immature respiratory muscle mass
• Lung anatomy is not fully formed

21
(No Transcript)
22
(No Transcript)
23
(No Transcript)
24
Other physiological principles of interest

• Total body water content
• Fat and muscle content
• Immature liver enzymatic function
• Reduced GFR and tubular function
• Serum proteins reduced in quantity and quality
• Blood-brain barrier is porous

25
(No Transcript)
26
(No Transcript)
27
(No Transcript)
28
(No Transcript)
29
Congenital Diaphragmatic Hernia
30
(No Transcript)
31
Incidence

• 12200 births, but with 50 stillbirth, appears
  to be 15000
• Polyhydramnios in 76, but associated with 11
  survival
• 80 of lesions are classic left sided, 1 are
  bilateral (and fatal)
• 50 have cardiac or chromosomal lesions highly
  lethal

32
Pathophysiology

• Pulmonary hypoplasia bilaterally
• reduction in size of pulmonary vascular bed is
  greatest problem
• vessels have extensive musculature
• parenchyma reduced of alveoli, small alveolar
  size
• results in hypoxia, hypercarbia, shunting,
  reversion to fetal circulation

33
Outcome Prediction

• Poor outcome
• pH lt 7.2, PaCO2 gt 50 mmHg
• pH lt 7.2, PaO2 lt 60 mmHg postop
• A-aDO2 gt 200 - 300 mmHg
• PaCO2 gt 40, VI (ventilatory rate x mean airway
  pressure) gt 1000

34
Clinical Presentation

• Small defects may not be apparent for 24 - 48
  hours
• Signs cyanosis, dyspnea, and apparent
  dextrocardia
• Physical
• scaphoid abdomen
• barrel shaped chest with bowel sounds or
  decreased breath sounds
• CXR bowel, mediastinal shift

35
Preoperative Care

• Gastric decompression
• Avoid mask ventilation awake intubation?
• Avoid high peak airway pressures
• Treat acidosis perfusion with bicarbonate,
  fluids, pressors
• Evaluate for associated defects
• Surgical emergency?

36
Anesthetic Management

• Avoid hypothermia
• Narcotic / oxygen / relaxant technique is most
  common
• Avoid nitrous oxide
• Avoid reversion to fetal blood flow
• hyperventilation
• alkalosis
• adequate oxygenation

37
Adjunctive Agents

• ECMO for patients with
• hemodynamic instability
• severe barotrauma
• persistent acidosis
• unresponsive pulmonary hypertension
• Nitric oxide to reduce pulmonary hypertension
  and vascular reactivity

38
Surgical Timing

• Classically reduce hernia ASAP
• Problem lung function worse postop due to
  decreased compliance
• increased intraabdominal pressure
• displacement of diaphragm position
• 50 decrease in compliance means 100 mortality
• Surgical delay reduced mortality?

39
Postop Results

• Overall mortality still 50
• Survivors have residual lung disease
• bronchopulmonary dysplasia
• pulmonary hypoperfusion dead space
• decreased FEV1 FVC

40
(No Transcript)
41
Tracheoesophageal Fistula
42
(No Transcript)
43
(No Transcript)
44
Omphalocoele Gastroschisis
45
Omphalocoele

• Incidence 16,000 - 110,000
• 25 - 30 are premature or low birth weight.

46
Differences Omphalocoele

• Herniation of abdominal contents at the base of
  the umbilicus, due to failure of the gut to
  return to abdominal cavity by 10th week of
  gestation.

47
Differences Omphalocoele

• Intestinal contents covered by peritoneal
  membrane.
• Associated defects in 60-70.

48
Anomalies in omphalocoele

• GI malrotation, Meckels, atresias, biliary
  atresia, imperforate anus.
• CV (20) Tetralogy of Fallot, ASD, VSD.
• GU bladder extrophy.
• Craniofacial cleft lip / palate, jaw tongue
  tumors.

49
More anomalies

• Beckwith Wiedemann macrosomia, macroglossia,
  hypoglycemia.
• Pentalogy of Cantrell defects in abdominal
  wall, diaphragm, sternum, heart pericardium.
• Lower midline defects vesicointestinal fistula,
  bladder extrophy, imperforate anus.

50
Gastroschisis

• Incidence 130,000.
• 60 are premature.

51
Differences Gastroschisis

• Defect of abdominal wall to right of umbilicus,
  due to interruption of omphalomesenteric artery
  and infarction of abdominal wall.

52
Differences Gastroschisis

• Intestinal contents not covered by peritoneum.
• Fewer associated anomalies, most of which are GI
  (malrotation, atresias).

53
Preop Considerations

• Heat loss proportional to size of defect. Use
  bowel bag to cover.
• GI decompression limit aspiration distention
  w/ OG tube.
• Fluid loss from peritonitis, 3rd space loss,
  bowel edema ischemia (includes protein loss).

54
Preop Management

• Evaluate associated defects.
• Thermal management.
• Fluid resuscitation
• CVP ? Art line useful. Foley needed.
• Crystalloid plus albumin
• Up to 80 ml/kg acutely.
• May need 3-4x maintenance.
• Follow UOP, acid-base, electrolytes.

55
Intraoperative Care

• Narcotic/air/oxygen technique.
• Adequate relaxation
• Surgical intent closure
• Primary closure if possible.
• Silo closure staged reduction.
• Compression ventilatory distress, caval
  compression, renal compromise (oliguria, HTN)

56
Postoperative Care

• Mechanical ventilation minimally 24-48 hours,
  longer for silo closure.
• Continued fluid resuscitation.
• Monitor for sepsis.
• Consider TPN postop ileus common.

57
Outcome

• Morbidity and mortality associated with
  congenital anomalies (esp. CV) and prematurity.
• Prior to mid 1960s, mortality 70.
• Long term residual problems are minimal,
  dependent on extent of anomalies.

58
(No Transcript)
59
(No Transcript)
60
Myelomeningocoele
61
(No Transcript)
62
(No Transcript)
63

• Necrotizing Enterocolitis

64
(No Transcript)
65
(No Transcript)
66
Sacrococcygeal Teratoma
67
(No Transcript)
68
(No Transcript)
69
(No Transcript)
70
(No Transcript)
71
Pulmonary Disease

• Respiratory anatomy
• Surfactant deposited after 32 - 34 weeks
• alveolae develop mostly after 36 weeks
• Ribs are cartilaginous compliant
• Rib orientation is circular rather than
  elliptical

72
Pulmonary Disease

• Respiratory control
• paradoxic response to hypoxia
• Initial hyperventilation, then respiratory
  depression
• Hypothermia blunts initial hyperventilation
• Response to CO2 develops with gestational age
• Hypoxia blunts the CO2 response further

73
Pulmonary Disease

• Overall pulmonary physiology
• Increased work of breathing (compliant thorax,
  decreased FRC, increased closing volume),
  increased O2 consumption, and tendency to muscle
  fatigue may lead to apnea periodic breathing

74
RDS BPD

• RDS
• Risk inversely proportional to birth weight
• Decreased pulmonary type II cells, decreased
  surfactant
• Characterized by low compliance
  microatalectasis
• Risk barotrauma (pneumothorax, pneumomediastinum,
  PIE)

75
BPD

• BPD
• Secondary to O2 toxicity, barotrauma, intubation
• Obstructive component with air trapping,
  atalectasis, poor compliance
• May lead to cor pulmonale
• Watch fluids (esp. Those on diuretics)

76
Cardiac Physiology

• Fetal circulation
• In utero shunt across PFO PDA
• Elevation of PVR can cause reversion (meconium
  aspiration, sepsis, polycythemia, hypoxia,
  acidosis, hypotension)
• PDA
• Up to 80 incidence in infant lt 1000 g
• Left to right shunt, increased PBF, left heart
  overload

77
Cardiovascular physiology

• Myocardial function
• Poorly compliant myocardium, mostly mitochondria
• Cardiac output related to heart rate, not stroke
  volume
• Immature catechol response baroreceptor
  response

78
Hematology

• Hemoglobin
• Premature infant with Hb lt13 g/dl (term 18-20
  g/dl)
• 75-80 is HbF, shorter lifespan of red cells
• P50 is 18 mmHg (adult 27) greater O2 uptake
  and decreased ability to unload
• Compensation for decreased P50 increased
  cardiac output, Hct, and blood volume. All may
  be limited in premature

79
Pulmonary Disease

• Respiratory anatomy
• Surfactant deposited after 32 - 34 weeks
• alveolae develop mostly after 36 weeks
• Ribs are cartilaginous compliant
• Rib orientation is circular rather than
  elliptical

80
Hematology

• Hemoglobin
• Premature infant with Hb lt13 g/dl (term 18-20
  g/dl)
• 75-80 is HbF, shorter lifespan of red cells
• P50 is 18 mmHg (adult 27) greater O2 uptake
  and decreased ability to unload
• Compensation for decreased P50 increased
  cardiac output, Hct, and blood volume. All may
  be limited in premature

81
Pulmonary Disease

• Respiratory anatomy
• Surfactant deposited after 32 - 34 weeks
• alveolae develop mostly after 36 weeks
• Ribs are cartilaginous compliant
• Rib orientation is circular rather than
  elliptical

82
Pulmonary Disease

• Respiratory control
• paradoxic response to hypoxia
• Initial hyperventilation, then respiratory
  depression
• Hypothermia blunts initial hyperventilation
• Response to CO2 develops with gestational age
• Hypoxia blunts the CO2 response further

83
Pulmonary Disease

• Overall pulmonary physiology
• Increased work of breathing (compliant thorax,
  decreased FRC, increased closing volume),
  increased O2 consumption, and tendency to muscle
  fatigue may lead to apnea periodic breathing

84
RDS BPD

• RDS
• Risk inversely proportional to birth weight
• Decreased pulmonary type II cells, decreased
  surfactant
• Characterized by low compliance
  microatalectasis
• Risk barotrauma (pneumothorax, pneumomediastinum,
  PIE)

85
BPD

• BPD
• Secondary to O2 toxicity, barotrauma, intubation
• Obstructive component with air trapping,
  atalectasis, poor compliance
• May lead to cor pulmonale
• Watch fluids (esp. Those on diuretics)

86
Cardiac Physiology

• Fetal circulation
• In utero shunt across PFO PDA
• Elevation of PVR can cause reversion (meconium
  aspiration, sepsis, polycythemia, hypoxia,
  acidosis, hypotension)
• PDA
• Up to 80 incidence in infant lt 1000 g
• Left to right shunt, increased PBF, left heart
  overload

87
Cardiovascular physiology

• Myocardial function
• Poorly compliant myocardium, mostly mitochondria
• Cardiac output related to heart rate, not stroke
  volume
• Immature catechol response baroreceptor
  response

88
Pulmonary Disease

• Overall pulmonary physiology
• Increased work of breathing (compliant thorax,
  decreased FRC, increased closing volume),
  increased O2 consumption, and tendency to muscle
  fatigue may lead to apnea periodic breathing