Vacuum extraction - An overview

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Vacuum extraction - An overview POST GRADUATE
LECTURE SERIES Dr.Ketan Gajjar Assistant
Professor Dept of Obstetrics and Gynecology Shri
Krishna Hospital and Pramukh Swami Medical
College, Karamsad.Anand.Gujarat
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HISTORY In the Elements of Physics in 1831, Neil
Arnott , MD, wrote "The simple contrivance now
described, and which may be called a pneumatic
tractor, seems well suited to various purposes of
surgery."
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• Historical Aspects
• Zanzihar fishermen used the suction cups of
  remora (pilot fish) for catching sharks.
• Hildonus (1632) first applied vacuum principle in
  surgery when he treated depressed fracture of
  skull in infants.
• James young (1708) , mayor of plymouth is
  credited for the use of a cupping glass to assist
  delivery.

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• James young Simpson (1848) from Edinburgh devised
  the first practical instrument on record.
• It was known as air tractor.
• He discontinued its use in favor of his own
  forceps.
• Tage Malmstrom of Gothenburg , Sweden in 1953
  described the most successful and widely used
  model. He redesigned it in 1956.
• Pelosi, Apuzzio introduced silastic cups in 1984.

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Vacuum extraction (VE) has deep historical roots.
The origin of vacuum extraction is in
cupping, a therapeutic technique used long
before Hypocrites. In cupping, a metal or glass
cup was heated over an open flame, then applied
to a lesion or skin puncture. As the cup
cooled, a vacuum developed, extracting blood or
other fluids. Cupping also occasionally was used
for a number of surgical procedures, such as
raising depressed skull fractures.
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James Young Simpson invented the first practical
vacuum extractor in 1849 . Simpson experimented
with vacuum devices, producing a working delivery
instrument in the late 1840s that he successfully
employed. However, his interest soon moved to
other obstetric issues and his air tractor fell
from popular attention.
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The immediate antecedent to modern extractors was
the stainless steel cup device, introduced by
Malmström in the late 1950s. This device
entered US practice late in the 1960s however,
because of technical problems with the original
design and case reports of severe fetal
complications, interest promptly waned. Within
the last several years following the introduction
of disposable soft-cup extractors and improved
rigid cup designs, VE has experienced a
revival. This renewed interest also has led to
a more scientific study of vacuum technique,
improving both the success and safety of VE.
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• Synonym Ventouse
• Introduction (Definition)
• Vacuum is an operation for the delivery of the
  fetal head from the mother by use of a vacuum
  extractor applied to the fetal scalp on presence
  of maternal effort (Hughes).

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Indications Conventional Prophylactic to cut
short 2nd stage in conditions where (i) mother
cannot or should not bear stress of 2nd stage due
to maternal condition which may exacerbate e.g..
Hypertension , DM, PIH, severe anemia, Eclampsia.
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Indications (ii) due to presence of obstetric
conditions such as 1.previous LSCS
Instrument used Flexible, or malmstrom. 2.Prolo
nged 2nd stage (failure to progress in 2nd
stage 2 hrs. in c/o primi without analgesic or
3 hrs. with analgesic and 1 hr. in c/o multi
without analgesic or 2 hrs. with
analgesic Frequency of use 49 Instrument -
any can be used
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Indications

• (iii) Maternal distress
• (iv) Fetal distress in 2nd stage of labor (used
  in 15 of cases ).
• In those cases of fetal distress where delivery
  is imminent (reasonable strength) and labor is
  progressing well (not in continuation with late
  1st stage delay).
• i.e. fully dilated or even gt 7 cm dilatation when
  disproportion is not a clinical question.
• Always keep facilities for LSCS ready
• use of forceps by some preferred as faster
• use of silastic / plastic suctions

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Indications
(vi) Occipitoposterior position (POP) Birds
modification cup (vii) To end trial of labor
successfully in borderline CPD Attempted
delivery. In presence of preparation The
instrument of choice is circumstances where fetal
distress is not present and trial of midpelvic
extraction is contemplated
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Non conventional uses in obstetrics 1. To
deliver 2nd of twin if head is presenting part
. Advantage After confirming presentation and
station of the head of 2nd twin , increase
oxytocin infusion. When vacuum extractor is
applied promptly it produces negative pressure
which grasps the fetal head with out loss of
station and when traction is produced with
uterine contractions prompt delivery is
achieved.
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• 2.To deliver head at LSCS in following
  conditions
• Large head
• Thin lower uterine segment in women with narrow
  pelvis predisposes to laceration when manual
  extraction of fetal head is performed so
• ventouse helps to prevent manipulations which may
  endanger integrity of lower uterine segment.

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3. To deliver frank breech cup is applied on
anterior buttock (charmers) . Obsolete. 4.
prolapsed cord in 2nd stage of labor 5. To
arrest brisk hemorrhage in minor degree placenta
praevia with vertex presentation.obsolete.
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(III) Non obstetric uses To manipulate and
deliver large ovarian cysts with out enlarging
abnormal incision cysts cup may be used.
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Forces in vacuum Extraction
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Forces in vacuum Extraction
The purpose of the vacuum extractor is to create
a tractive force on the fetal scalp to assist
the normal forces of labor Negative pressure
hold the vacuum cup in opposition to fetal
scalp. Theoretically force applied to scalp is
transmitted to the attachment of the scalp at the
circumference at the fetal skull, producing
relatively limited compression of cranium
compared with forceps
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Forces in vacuum extraction

• With classic Malmstom instrument maximum possible
  force is approximately 13-14kg.
• But can exceed 20 kg with a firm application .
• Note that during spontaneous labor maximum
  expulsive force acting on the fetal head
  approximates 15 kg.

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Forces in vacuum extraction

• Greater forces will lead to dislodgement of cup
  or leakage .
• Safety mechanism
• Average pulling force for vacuum delivery is 10
  kg which amounts for 75 gm/cm2
• This forces is 20 times greater (1400gm/cm2) in
  forceps delivery even higher between blades.

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Forces in vacuum extraction
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Forces in vacuum extraction

• Note
• During spontaneous vaginal delivery average
  cranial compression varies from 1.9 to 2.9 PSI
• During vacuum extraction it was 4.6 PSI.
• During forceps it was 3.0 to 4.4 PSI (Moolgaokar
  et al)

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Vacuum Devices
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• Vacuum Device
• Instruments
• Metal cups with plates (30,40,50,60mm
  marginal diameter)
• Traction chain
• Traction handle
• Rubber tube with enclosed traction chain
• Vacuum bottle with pressure gauge or manometer
  
• Vacuum pump (manual / electric)

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I.Rigid Mental cups (Also k/a Maelstrom's cup)
Parts Metal cup with plates made up of sterile
cup diameters (30,40,50,60m) marginal
diameters Traction Plate Traction chain
attached to the plate. Traction handle with metal
pin, which is detachable, pressure rubber tube
with enclosed the traction chain vacuum pump.
Which varies with strength of the suction
(machine) which maintain preset pressure vacuum
bottle with a pressure gauze which measures the
negative pressure produced and has a hand / foot
valve to permit operator to rapidly interrupt
suction.
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Rigid Metal cups (Also k/a Malmstrom cup) Parts
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• Advantages
• Selective advantage with big baby
• Difficult delivery anticipated
• Presence of large caput

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Type of cup preferred 50 mm cup is in use as
greater the cup diameter, greater is the traction
force possible and less chances of cup detachment.
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• Disadvantage
• With defective flexion application of cup in
  middle over the occiput-traditional cup is less
  useful
• more chances of scalp disfigurement

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Birds Modification of Malmstroms cup Here
the vacuum tube is attached to the opening near
the periphery of the cup and the traction chain
to the hook in the center of the cup.
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Advantage ? Where these is significant
deflexion prior to application (i.e. only
anterior fontanel is palpable OP cup should be
used allows the head to flex and followed by
occurrence of spontaneous rotation to
occipitoanterior position as the presenting part
encounters the pelvic floor. ? In such cases
where oblique traction in order to correct
deflexion is to be applied less tendency to
slip. ? Easy assembly
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Disadvantage Inadvertent dislodgement of the
vacuum tubing during vaginal insertion.
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• Sjosteat cup cup is deeper at the periphery
• Oneils cup (West Australia)
• Advantage Rotating traction collar which
  maintains the direction and pull through the
  center of the vacuum surface.

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• Advantage cont..
• This principle eliminates the tilt and reduces
  lateral movement because traction in any
  direction always passes through the center of the
  cup.
• Cup maintains optimal traction cup 70o range
• size type
• Available in OA 50mm,
• OP 50mm size

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• II Silastic cup (Flexible vacuum extractor)
• k/a Kobayashi device ,Dow Cornings midland
  9coop.)
• Material soft, translecucent, silicon clashimer
  parts
• Obstetric vacuum cup cone or cup shaped and 65
  mm in diameter
• Length tube is 208mm (entire assembly)
• Shaft has 3 ridges services potential traction
  sites
• Handle which has a chrome plate, brass grip with
  a plunger activated value mechanism to release
  vacuum

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Advantages (i) soft cup which occupies less
space easier vaginal insertion automatic
adjustment to fetal head (ii) less chances of
scalp injury and disfigurement (iii) less
waiting period due to flexibility and slow
incremental increases in vacuum to produce
chignon is not required.
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• Disadvantage
• Increased chances of failure (detaches more
  frequently) due to absence of mushroom flenge.
• Cannot be used in presence of caput
• In c/o difficult vacuum in where more traction is
  required.
• Fails in c/o occipito-posterior positions .
• Darkens considerably with age multiple
  sterilization .
• Expensive and not reusable.

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• Plastic cups
• Disposable Plastic Cup(DPC)(Mityvac device)
• Parts
• one piece disposable molded polyethylene 60mm
  plastic cup (flared one size semi rigid)
• with attached handle (37, 38)
• Suction tube 8
• Hand pump tube handle pressure pressure
  gauge for creating vacuum

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Plastic cups Disposable Plastic Cup(DPC)(Mityvac
device)
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• Plastic cups
• advantages
• assembly not required -faster
• Presterilized and disposable
• Builds pressure quickly (with in 1-2 min.)
• Handy, transportable
• Use in absence of electricity
• disadvantage
• )same as with metal cup

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Bell Vacuum Extractor CupsThe Mityvac Bell
cups have a large diameter mouth to distribute
tractive force across the fetal scalp. These cups
are to be used in the low Occiput Anterior and
Outlet presentations.
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The Mityvac Reusable Bell Vacuum Extractor Cup
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The Mityvac Standard Bell Vacuum Extractor Cup
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The Mityvac MitySoft Bell Vacuum Extractor Cup
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Mushroom Vacuum Extractor CupsThe Mityvac
Mushroom cups are uniquely shaped to provide
greater traction and excellent manipulation
during vacuum assisted deliveries. These cups can
be used in low Occiput Anterior and Outlet
presentations or they can be used in low Occiput
Posterior (OP) and Occiput Transverse (OT)
positions.
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The Mityvac "M" Style Mushroom Vacuum
Extractor Cup is uniquely shaped to provide
greater traction and excellent manipulation
during vacuum assisted deliveries. The cups
softly contoured design allows for a stronger
grip while helping to minimize infant scalp
trauma. The flexible stem bends into a 90-degree
angle without losing vacuum.
The Mityvac "M" Style Mushroom Vacuum
Extractor Cup
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• Reusable Plastic Cup (RPC) (Manipulator cup)
• advantage same as with DPC
• sterilized with 2 gtuleraldehyde or autoclaved
• useful in delivery of deflexed head
• ideal in outlet applicator
• Variant Lager cup for low midcavity application
  available which is k/a traction cup

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Reusable Plastic Cup (RPC) (Manipulator cup)
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• Contraindications
• Absolute
• Moderate to severe (i.e. true CPD/macosomia)
  vaginal delivery is not possible
• Abnormal presentations should not be applied
• due to possibility of fetal injury
• technical problem of achieving proper seal

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• Contraindications-Abnormal presentation
• face
• Brow presentation
• shoulder
• after coming head of breech

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• Relative Contraindications
• Prior scalp sampling of blood for fetal gases
• (studies have found no unstances of neonatal
  exsanguinations in these cases
• Prematurity (lt36 wks)
• except in c/o twins as their delivery requires
  minimal traction due to dilatation of Cx and
  Vagina
• cause due to large concern over intracranial
  injury,ICH, Neonatal jaundice in some studies

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Relative Contraindications

• IUFD
• Cause chignon will not form
• also if maceration has occurred cranium is
  extremely flaccid and is usually not a barrier
• So option of assistance required
• forceps to be used
• Congenital abnormality of fetus (cranium)
  anencephaly, fetal coagulopathy
• Cause Improper chignon

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Relative Contraindications

• High station of head
• It is not desirable to apply except in c/o
  delivery of 2nd twin and rarely fetal distress
• In c/o fetal distress as there are increased
  duration (chances) for assembly of vacuum etc.

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Procedure Definition Outlet vacuum
extraction is the cephalic application of the
vacuum extractor at full cervical dilatation when
the fetal skull has reached the pelvic floor or
fetal head is at or in the perineum and scalp is
visible at the introitus with out spreading the
labia, regardless of the position.
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• Pre-procedure
• Consent Informed and written about indication
  give mother choices
• Fulfilling prerequisites (i) preparation and
  consent
• (ii) confirmed Indication r/o CI
• Proper pediatrician facilities
• concomitant availability of caesarian section

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• Operator /surgeon with proper skill
• Analgesic if required
• Bladder empty / membranes ruptured
• Operator sure of
• position of Head (for proper application)
• Station (ideally O)
• dilatation of cervix ideally full
• Deflection of head
• Proper maternal efforts with uterine contraction

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• Method
• Painting and drapping
• Anesthesia
• Not required in multiparas and low station
• If required
• Pudendal block
• Saddle block
• Uncommonly (epidural)
• Never GA as active maternal participation
  required

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• Device checking and assembly
• No leakage
• Proper seal
• Establishment of proper maternal efforts and
  uterine contractions if necessary with oxytocin
  drip

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• Application
• (i) pelvic examination to confirm
• Occipitoanterior
• Fetal position OP
• Station

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• Occipito anterior
• Regardless of the type vacuum cup should always
  be located in the midline towards the fetal
  Occiput.
• Three checks for correct application

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Occipito anterior
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• 2. Knob towards occiput (or marker or handle)
• Head will be flexed
• Permits observation of rotation as presenting
  part descends
• 3. Maternal tissue should be avoided to avoid a
  poor seal and maternal injury

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• Occipito posterior and Occipito lateral positions
  
• Management is controversial whether by
• forceps
• vacuum

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Occipito posterior and Occipito lateral positions
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• (ii) The cup is lubricated with surgical soap or
  gel, turned sideways and gently pressed through
  the labia into the vaginal canal as the perineal
  body is depressed by the operators finger
• The operator presses the cup gently against the
  head orienting it over the center of the
  posterior fontanel and sweeps his / her finger
  around the cup to be certain that no maternal
  tissues are entrapped.

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(iv) Tight vacuum is applied to seal the cup to
the fetal head (100 mm of Hg) 0.2 Kg/ cm2 force
(tractions applied) after checking the
application
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• Traction
• It is applied in the pelvis curve it is
  continuously maintained the index and The middle
  fingers of the nontraction hand make contact with
  the fetal scalp while the thump pushes the vacuum
  cup against the fetal head with a backward
  pressure during traction (Three fingers grip)

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• Purpose 3rd fingers
• Results in a vector of force which follows the
  pelvic curve.
• During spontaneous vaginal delivery fetal head
  fails to use the part of the hind pelvis and
  using this technique with each pull, this extra
  posterior space can be utilized.
• Counter pressure retains cup
• If detachment starts judges early detachment and
  descent of presenting part

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• Pressure
• Once certain that application is accurate
  increased in pressure by 0.2kg/cm2 at 1-2min
  producing chignon
• Full operative pressure is 0.8 kg/ cm2
• With the silastic instrument, formation of
  chignon is not required and full operative vacuum
  may be applied at once with traction immediately
  following

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• (8) Patient is asked to bear down and augment
  expulsive efforts
• (9) Pull In direction of traction and maternal
  expulsive effort

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• Descent should occur with first traction
• FHS should be monitored transient bradycardia
  due to dural on pulling may be there and may
  revert to normal and this helps to distinguish
  latrogenic bradycardia from true fetal distress
• When the head crowns suction is interrupted and
  vacuum cup detached after the fetal chin grasped
  by Ritgens maneuver. Delivery of the body
  follows in usual fashion

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• Rules for use of vacuum
• Traction is bimanual in the pelvic curve with
  close attention to cup detachment and 3 finger
  grip
• All applications are subject to three checks
  prior to traction
• Traction augments spontaneous or induced
  uterine contractions
• Maximum time for cup application is 25 min

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Rules for use of vacuum

• Max. of five traction pulls
• Max of two cup detachments
• Advancement of fetal head should begin with
  first attempted traction
• Applications to premature infants are to be
  avoided

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• If cup slips
• Second correct application at same place (do not
  apply gt twice)

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• Failed vacuum (1.3 cases)
• causes
• Cephalopelvic disproportion
• Fetal macrosomia
• Pelvic inadequacy or mal-formation

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• Dystocia
• Fetal tumor / maternal tumor
• Conjoined twin / locking twins
• High presenting part
• Undilated cervix
• Deflexed head / OP

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Technical errors Vacuum leakage Incomplete or
defective equipment Oblique traction Poor
maternal effort
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• Complications
• Maternal
• Cervical lacerations (if Cx not fully dilated)
• Vaginal tears, bruises
• Vaginal hematoma
• Rare VVF, Rupture of pubic symphysis

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• Fetal (Phenomenon)
• ? Chignon
• called by Rosa in 1933
• chignon is a French word means a large coil or
  hump of hair drawn into a bun at the back of the
  head
• ? its an artificial caput and does not defer
  from the spontaneous caput except in
• etiology

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• In most cases it is only a cosmetic concern.it
  resolves rapidly during postpartum period
• ? Mother and relative should be explained
  immediately and shown the chignon and
• informed that its a phenomenon and will
  disappear in few hours
• ? Silastic cups are less likely to produce
  chignon then metal cups

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• Incidence of scalp trauma increases if
• operator is inexperienced
• Prolong duration of traction
• Recurrent cup detachment and reapplication
  particularly Popping off at cup
• Early signs of cup detachment are not recognized
  and taken care off
• Early signs at cup detachment are lifting of the
  cup edge and hearing a sucking sound (hissing
  sound) as the suction begins to fall.

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• Too rapid induction of vacuum
• Failure to await caput formation if the rigid
  V.E. is used.
• Continues traction in the absence of certain
  contractions
• Use of excessive vacuum

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• Negative traction is defined as traction-
  insufficient to cause the fetal head to descend
  in the birth canal, but strong enough not to
  detach the suction cup. It is particularly
  dangerous as it causes scalp to descend without
  skull.
• Grossly edematous scalps are more easily injured
  and bald scalp are more prone to abrasion.

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• Cephalic Hematoma
• Definition collection of blood in subperiosteum
• Incidence 10
• limited to single cranial bone usually parietal
  bone
• Jaundice
• Retinal H/rage
• No adverse long term outcome

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Cephalic Hematoma
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• Subgaleal haematoma
• 1.6 / 1000 live births
• also k/a subaponeurotic hematoma
• caused by rupture of diploic vessels (Emissary
  vein) in the loose sub aponeurotic tissue
• large space extends from orbit to nape of neck
• causing large collection of blood

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• Clinical Features
• diffuse pitting edema at scalp with in 1.5 to 48
  hrs.
• Hypovolemic shock
• Fluctuation nt
• ballotable cranial fluid nt
• Hemotocrit falls lt 10
• late Hyperbilirubinemia
• Rx FFP

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• Complication con.
• (5) Intracranial Hemorrhage 0.35 incidence
• (6) Subdural a Subarachnoid Hemorrhage
• (7) Skull fracture
• Scalp abrasion / laceration / Ecchymosis
• (8) Neurological injuries
• Transient neonatal lateral rectus paralysis (due
  to transient sixth nerve palsy)
• (9) Biochemical trauma Intra uterine hypoxia

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• Advantages
• ) Simple to use
• ) Less force applied to fetal head
• ) Done in LA/Block
• ) No increase in diameter of presenting head
• ) Less maternal soft tissue injury
• ) Less fetal injury

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• Disadvantage
• Maternal effort required
• Possible longer delivery time than with forceps
• Small increase in incidence of cephalhematoma

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• Vacuum over forceps
• Can be applied at relatively higher station at
  head
• Can be applied to non rotated head
• Permits autorotation at head along with traction

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Vacuum over forceps

• Compression force is less (1/20th as compared
  to forceps)
• Does not require additional space between tight
  fitting head and pelvis.
• Maternal trauma less

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• Forceps over vacuum
• After coming head of breech
• Dead fetus
• Face presentation

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Key points RCOG audit standard says that
vacuum is the first choice of instrument for
instrumental vaginal delivery.
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• Mnemonic for Vacuum Extraction
• A Ask for help, Address the patient, and is
  Anesthesia needed.
• B Bladder empty.
• C Cervix must be completely dilated.
• D Determine position

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• E Equipment and Extractor ready.
• F Apply the cup over the sagittal suture and in
  relation to the posterior Fontanelle.
• G Gentle traction in the proper axis.

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H Halt traction when the contraction is over
Halt the procedure if you have had
disengagement of the cup three times,have had
no progress in three consecutive pulls or three
"pop- offs.I Evaluate for Incision
(episiotomy) when the head is being
delivered.J Remove the cup after the Jaw is
delivered.
American Academy of Family Physicians. Advanced
life support in obstetrics (ALSO). Leawood, Kan.
105
Vacuum extraction versus forceps for assisted
vaginal delivery (Cochrane Review)

• Reviewers' conclusions
• Use of the vacuum extractor rather than forceps
  for assisted delivery appears to reduce maternal
  morbidity. The reduction in cephalhaematoma and
  retinal hemorrhages seen with forceps may be a
  compensatory benefit.
• Johanson RB, Menon V. Vacuum extraction versus
  forceps for assisted vaginal delivery (Cochran
  Review). In The Cochran Library, Issue 2 2003.
  Oxford Update Software.

106
Soft versus rigid vacuum extractor cups for
assisted vaginal delivery (Cochran Review)

• Reviewers' conclusions Metal cups appear to be
  more suitable for Occipito-posterior', transverse
  and difficult Occipito-anterior' position
  deliveries. The soft cups seem to be appropriate
  for straightforward deliveries.
• Citation Johanson R, Menon V. Soft versus rigid
  vacuum extractor cups for assisted vaginal
  delivery (Cochran Review). In The Cochran
  Library, Issue 2 2003. Oxford Update Software

107
Record keeping of V.E. Indication for the
procedure Anesthesia Personnel patient Instruments
used Cup, Tube, Vacuum Station Position Deflexi
on Complication
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Minimizing medico legal risk O grady and
cowoskers in 1995 concluded that the cases of
malpractice litigation involving instrumental
deliveries devices from 4 broad obstetric
categories Failure to exercise adequate.
Informed medical judgments when assessing what
cases are appropriate for an instrumental
operation and when that intervention should take
place.
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• Failure to understand or accept the limitations
  at the procedure itself and plan in advance for
  possible failure
• Failure to abandon timely a trial of instrumental
  delivery.
• Failure to recognize CPD

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