1. PRESENTOR: Dr.Kumar MODERATOR : Dr.chaitanya kumar
2. Introduction Conjoined twins are identical twins whose
bodies are joined in utero. It is a rare phenomenon; it is
estimated to range from 1 in 50,000 births to 1 in 2,00,000 births.
Higher incidence in southwest asia and africa. They are always the
same sex and race. Approximately 75% of conjoined twin pairs are
females.
3. Introduction They are identical twins(monozygotic and
monochorionic) who develop with a single placenta from a single
fertilized ovum. They are at a ratio of female to male 3:1. Of
these, about 40% were stillborn, and 60% live born. About 25% of
those are called miracle babies.
4. Embryology Two contradicting theories exist to explain the
origins of conjoined twins. The older and most generally accepted
theory is fission, in which the fertilized egg splits partially.
The second theory is fusion, in which a fertilized egg completely
separates, but stem cells(which search for similar cells) find
like-stem cells on the other twin and fuse the twins together.
However, rather than 'fission' or 'fusion', the defect leading to
conjoined twins may well be a coalescence by overlapping of closely
contiguous twin embryonic axis formative fields within a single
embryonic disc.
5. Embryology Zimmerman classic theory results when the inner
cell mass incompletely divides between 13-16 days of fertilization.
Incomplete division seems to be associated with inhibition of
complete differentation of various organ systems. Exact reason of
complex fusion is unknown.
6. Siamese Twins Famed twins, Chang and Bunker, were born in
Siam (now Thailand) in the early 1800's, although they eventually
settled in the United States. While they were the first conjoined
twins whose medical history was documented, they were not the first
conjoined twins. As they traveled the world, later they were known
as "the Siamese twins."
7. Siamese Twins Records reference a set of conjoined boys
living in Constantinople in 945 A.D. Another well-known set, Mary
and Eliza Chulkhurst, lived in England in the twelth century.
8. Classification Conjoined twins are usually classified by the
point at which they are joined (the Greek word pagus, meaning "that
which is fixed.") There have been as many as three dozen separate
types identified in the last century.
9. Conjoined twins are further classified by the number of
limbs present and the internal organs that are involved in the
conjunction 1. Two arms: dibrachius 2. Three arms: tribrachius 3.
Four arms: tertrabrachius 4. Two legs: bipus 5. Three legs: tripus
6. Four legs: tetrapus
10. The degree of cardiac fusion, or degree of cardiopagus, can
be considered as follows (Andrews et al., 2006): A: Separate hearts
and pericardium B: Separate hearts and a common/shared pericardium
C: Fused atria and separate ventricles D: Fused atria and
ventricle
11. Classification TYPES OF CONJOINED TWINS: Those three dozen
separate types are: 1. Conjunction never involving heart or
umbilicus, 2. Conjunctions always involving the Umbilicus (Midline
Conjunctions) , 3. Rare forms of conjoined twins, having different
patterns..
12. Conjunction never involving heart or umbilicus: I-
Craniopagus. - Cranial union only. - 2% of all conjoined twins. II-
Pygopagus. - Posterior union of the rump. - 19% of all conjoined
twins.
14. Craniopagus There is cranial union only; it has an
incidence of about 2% of all conjoined twins. Various forms and
orientations of fusion may be seen, with both neural and major
vascular connections. Craniopagus parasiticus: A second bodiless
head attached to the head.
15. Craniopagus Separation is possible; depending on how much
of the brain is shared. There is high risk of brain damage. Winston
(1987) described a classification based on the deepest structures
shared 1. Type A: Share only scalp and subcutaneous structures 2.
Type B: Share dura mater 3. Type C: Share dura mater and arachnoid
and pia mater 4. Type D: Share brain structures as well as
structures from types A, B, and C
16. Pygopagus Joined at the sacrum, Incidence is about 19% of
all conjoined twins. Separation is possible. The survival rate is
high.
17. Thoracopagus Anterior union of the upper half of the trunk.
This is the most common form constituting approximately 35 -40 % .
Babies face one another and have major junction at the level of
chest, with conjoined hearts and livers as well as upper
gastrointestinal (G.I) tract. Separation surgery depends on cardiac
anatomy.
18. Omphalopagus Joined at the chest or abdomen. Similar to
thoracopagus twins, but in this case the twins do not share a
heart. This is the second most common representing 30-35%. Highest
rate of separation survival . Usually, only the liver is involved.
Because the liver can regenerate itself, this scenario is
preferred. Cephalothoracopagus or Janus.
19. Parapagus Lateral union of the lower half, extending
variable distances upward, Fused side-by-side with a shared pelvis
Dithoracic: fused abdomen pelvis, not thorax Diprosopic: one trunk,
one head, two faces with varying fusion Dicephalic: one trunk, two
heads, two, three, or four arms
20. Ischiopagus Anterior union of the lower half of the body,
about 6% of all conjoined twins. Heart is not involved. They are
joined at the pelvis. Separation is physically possible; however,
excretion and sexual organs' impairment might present.
21. Parasitic Twins Rare forms of conjoined twins, having
different patterns. 1. Parasitic twins: Asymmetrical conjoined
twins, one twin being small, less formed and dependent upon the
other. 2. Fetus in fetus: Situation in which an imperfect fetus is
contained completely within the body of its sibling.
22. Anaesthetic Management Conjoined twinning is one of the
most fascinating human malformations. Treating conjoined twins can
be a challenge for the surgeon as well as anaesthesiologist. There
are numerous conjoined twins in today's society. Most cases of
separation are extremely risky and life threatening.
23. Anaesthetic Management It is a multidisciplinary team
approach involving a. extensive medical work-up b. multiple
meetings and discussions with all the involved specialties and
supporting staff. c. involvement of parents, psychosocial
counselling of parents. d. rehearsal of the planned surgical
procedure, media contact prior to surgery.
24. Anaesthetic Management There is at best a fifty-fifty shot
of survival when it comes to separation. If at all possible ,
surgery seems like the best option for Conjoined Twins. Parents
should make the final and informed decision on separation. The
rationale for deferring surgery should include single heart, major
communicating hearts or major anomalies.
25. Anaesthetic Management Elective separation for simple
conjunctions can be performed in the neonatal period with minimal
problems Surgery can be best delayed until such infants are
relatively mature (4-11months of age). Operative survival was 50%
in those operated on in the neonatal period, but 90% in those over
4 months of age.
26. Indications for emergency separation Where there is damage
to a connecting bridge (e.g., omphalopagus). This may occur at the
time of delivery. When the condition of one twin threatens the
survival of the other (e.g., complex congenital heart disease,
cardiomyopathy, sepsis). Deterioration of both twins because of
hemodynamic and respiratory compromise. This occurs typically in
thoracopagus twins. When the condition of one twin is incompatible
with life (e.g., anencephalic, acardiac, stillborn, or complex
congenital anomalies) but the other twin has a good chance of
survival.
27. Concerns Conjoined Twins' physiology like crossed
circulation, distribution of blood volume and organ sharing with
their anaesthetic implications. Massive fluid shifts and loss of
blood & blood components and their rapid replenishment.
Meticulous planning for organized management of long hours of
anaesthetic administration in two paediatric subjects
simultaneously.
28. Airway problems due to - paediatric age, repositioning
during surgery, relative facing of twins nasotracheal intubation is
usually carried out. Difficult acquiring vascular access with the
guide of ultrasound, can be achieved. Thermoregulation - Fluids and
blood were pre warmed before transfusion; even irrigation fluid was
also pre-warmed; twins were draped .
29. Anaesthetic Management Goals of the anaesthesia care are 1.
to pay meticulous attention to detail 2. monitoring 3. vigilance,
& planning for the postoperative care in the intensive care
unit(ICU), 4. a dedicated team of anaesthesiologists and
intensivists for each child with duplication of all monitoring and
equipment in one operating room.
30. Anaesthetic Management Crossed circulation problems
Pharmacokinetics and Pharmacodynamics are in-consistent in various
types of twins. Estimation of circulatory mixing is useful to help
calculate drug dosage and fluid replacement during surgery. Drugs
administered to one twin may have unexpected effects on the other,
especially for i.v administration when circulatory admixing is
present.
31. Anaesthetic Management Usually there is more
cross-circulation in the thoracopagus and craniopagus twins than in
other types, So one can expect altered and unpredictable drug
responses.
32. Anaesthetic Management Crossed circulation estimation The
routine evaluation of cross circulation is performed using many
methods like tc-99m microcolloidal human serum albumin (HSA).
Injection of indigo carmine and the examination of its excretion in
urine of the other twin. Testing by administering drugs such as
glycopyrrolate to one twin and detecting the effect on the other
twin.
33. Anaesthetic Management if surgery for separation is planed,
careful angiographic or radio isotopic imaging of the
cross-circulation is necessary for estimation of the cardiac output
percentage which is exchanged, as one of the twins might be
dependent on the other's circulation for survival. It should also
be recognized that the degree of cross- circulation is dynamic,
highly dependent on both twins' relative systemic vascular
resistance.
34. Anaesthetic Management Szmuk P, Rabb MF, curry B described
the first use of bispectral index monitor for detection of
cross-circulation in conjoint twins, Synchronous ventilation is
necessary to improve quality. These authors decided to use the
carlens (y) adaptor to achieve synchronous ventilation.
35. Anaesthetic Management Drug dosages: Recommended i.v doses
of anaesthetic agents for the combined body weight of the twins are
usually halved and then divided into two equal doses to be
administered to each twin. Reduced incremental doses are titrated
against response and help minimize the dangers of compounding drug
effects in one twin.
36. Importance must be given to assessing the following The
Airway: Problems with the airway in conjoined twins include 1.
Access to the mouth and larynx is difficult. 2. Visualization of
the vocal cords may be impossible. Close faces leave little room to
move to insert instruments in the airway. 3. Placement of the ETT
through the cords is challenging, because it tends to get caught on
the subglottis.
37. Mechanisms of Ventilation: It is important to ascertain
whether or not the diaphragm is involved in the junction, or
whether its function will be affected by surgery. Lung compliance
is affected, areas of atelectasis develop because of the limited
space between the two infants and the abnormal anatomy of thoracic
structures, the hearts are usually abnormal. As one twin develops
cardiorespiratory compromise with tachycardia, tachypnea, and
coughing, the other is also affected
38. Cardiovascular System: Assessment of the heart and major
vascular anatomy is crucial, because this impacts anesthesia and
vice versa. Craniopagus twins may, as with thoracopagus twins, have
cardiac failure. Because many of these infants will have spent
considerable time in the hospital, venous access may be a
challenging
39. Disability: 1. In craniopagus twins or any of the types
where the spinal cord may be involved in surgery. 2. a full
neurologic examination is required.- if any neuroaxial intervention
or procedure is planned as part of the anesthetic. 3. Bowel and
bladder function must be documented. 4. It may not always be
possible to place a urinary catheter, and urine output may not
always come from the kidneys of that infant.
40. Gastroesophageal Reflux: Gastroesophageal reflux is most
common in thoracopagus twins. Nursing the infants with their heads
up is helpful, and the use of antireflux medication should be
considered. While they are waiting for separation, good nutrition
is crucial to the infants growth. The body composition differs
between the two twins, as does their resting energy expenditure and
caloric intake.
41. Skin Cover: Tissue Expanders Tissue expanders are inserted
to facilitate skin closure when surgery will leave a significant
area uncovered. Anesthetic implications of the use of tissue
expanders include preoperative assessment of the pressure effects
of the expanders on the different organ systems. This includes the
effects on the skin and the cardiovascular system
42. Anaesthetic Management Requirements: Two sets of
anaesthesiologists, 2 work stations, 2 operating tables, 2
monitors, 2 suction apparatus, 2 sets of airway equipment & 2
sets of resuscitative equipment, one for each infant, are
essential, as each infant has to be separately monitored throughout
the procedure.
43. MONITORING Standard monitoring consists of SpO2, ECG, NIBP,
capnography, temperature and urinary output is necessary. Arterial
BP, CVP along with respiratory variables like RR, TV, Paw, and ABG
are to be monitored , Urinary bladder to be catheterized for urine
output measurement , naso pharyngeal temperature probe for
temperature monitoring, neuromuscular monitoring also to be
placed.
44. Premedication Sedative or anxiolytic premedication is
generally not required. In older sets of twins, sedation options
include midazolam, chloral hydrateeach of these has been used
successfully in some twins over 6 months of age . Atropine has been
used for neonatal twins, but this is only necessary when vagal
stimulation is likely to occur (e.g., with laryngoscopy or
bronchoscopy) or when the use of ketamine is planned. If an
intravenous induction is planned, the use of a topical local
anesthetic cream before venipuncture.
45. Induction Techniques for induction of anesthesia are
determined by the airway, the availability of intravenous access at
induction, the state of health of each infant. In those twins with
potentially difficult airways, spontaneous respiration with
inhalational induction with sevoflurane or the intravenous use of
ketamine is helpful. In infants with cyanotic congenital heart
disease or in those with complex anatomy, intravenous ketamine is a
safe option.
46. Muscle relaxation must not be used until airway access is
assured. Rapid sequence induction is often not possible in
ventrally conjoined twins. Inhalational induction may be followed
by the use of topical local anesthetic spray (2% lidocaine) to the
vocal cords to facilitate intubation. The type of ETT and the route
used (oral or nasal) are determined by the type of conjunction
(nasal is not suitable for craniopagus twins surgery, and this
route is often very difficult in thoracopagus twins).
47. Color coding
48. Intraoperative Management aim to provide ideal surgical
conditions in a safe and appropriate way for the type of conjoined
twins undergoing the procedure. Analgesia, amnesia, and muscle
relaxation should be provided, with control of the airway,
ventilation, hemodynamic stability, and temperature regulation.
Challenges with cardiovascular depression, difficult ventilation in
thoracopagus twins and unpredictable drug absorption and responses
with uncertain degrees of cross circulation all necessitate regular
adjustments in anesthetic agents and muscle relaxation
49. During anesthesia, vasodilation in one infant may result in
blood being diverted to this infant, causing a significant drop in
the blood pressure of the other twin. Fluid and blood loss may be
anything from half to more than five times each infants estimated
blood volume. Blood loss may be massive in craniopagus or
cardiopagus twins, in those whose livers are extensively fused, and
in those where a significant bony fusion is to be separated.
50. Temperature monitoring should aim at normothermia, and all
techniques available should be used to ensure proper temperature
control. The use of plastic drapes, padded bandages around the
limbs, and waterproof plastic bandages makes a significant
difference to temperature control during the surgery. After each
surgical group has operated and the positions have changed, these
measures also need to be moved. To facilitate postoperative
ventilation, oral tubes may be changed to nasal tubes at the end of
the procedure.
51. Postoperative Care Problems in the immediate postoperative
period relate to the consequences of 1. massive blood transfusion,
2. tight closure, 3. prolonged surgery, and 4. alterations in
preoperative anatomy. Monitoring for bleeding, hypoxia,
hypercarbia, acidosis, hypothermia, hypotension, and electrolyte
imbalance is mandatory. Ongoing volume losses, cardiac instability,
and respiratory impairment are common at this time.
52. When weaning the infants from mechanical ventilation,
attention must be paid to sternal insufficiency, diaphragmatic
dysfunction, and to the mechanics of breathing. Good pain relief is
obligatory and may include the use of intravenous acetaminophen
(paracetamol), which can be given orally or rectally. If chronic
pain syndromes are anticipated, the early use of gabapentin should
be considered.
53. Prognosis Immediate and long-term survival of conjoined
twins is extremely variable. Hidden long-term morbidity and
mortality occur with unresolved aspiration after thoracopagus
separation; bronchopneumonia, arrhythmias, and embolic
cerebrovascular pathology. Some survivors will be disabled and
require lifelong follow-up care