pediatrics skills

Pediatrics Skills

Pediatrics Review Notes

Lumbar puncture

http://sprojects.mmi.mcgill.ca/lumbar/introduction.htm

Lumbar Puncture – Indications

• Inidcated primarily for evaluation &

diagnosis of patients who present with

symptoms consistent with

– Meningitis

– Meningoencephalitis

– Subarachnoid haemorrhage


• Other neurologic indications:

– Malignancy

– Seizures

– Metabolic or degenerative Diseases

Lumbar Puncture - Indications

• Diagnostic

– Meningitis

– Meningoencephalitis

– Subarachnoid

haemorrhage

– Malignancy

– Seizures

– Metabolic /

degenerative disorders

• Neonates:

– Sepsis evaluation

– Febrile child with suspected

bacteraemia

– Children too young for

accurate clinical evaluation

of meningitis

– Apparent febrile seizure

– Mental status change with

no identifiable cause


• Therapeutic

– Management of pseudotumour cerebri

– Administration of intrathecal antibiotic therapy

– Instillation of chemotherapeutic agents

Lumbar Puncture –

Contraindications • Signs of raised intracranial pressure or a midline

shift

– Headache, papilledema

– Risk of herniation

• Severely ill patients

– Haemodynamic or pulmonary instability

– Wait until stable & not at risk of herniation

• Soft tissue infection over the lumbar spine area

• Severe, unresponsive coagulopathy / severe thrombocytopaenia

Lumbar Puncture – Equipment

• LP tray

• Spinal needle – 22 gauge

< 1 year 1.5” needle

(3.75 cm)

1 year – middle childhood 2.5” needle

(6.25 cm)

Older children; adolescents 3.5” needle

(8.75 cm)

Lumbar Puncture – Equipment

• Povidone-iodine solution

• 1% lignocaine & 25 gauge needle for local anaesthesia

• Sterile gauze

• 3-4 sterile specimen tubes

• For viral cultures

– Additional tube + cup of ice to place specimen in before the lab culture

Lumbar Puncture – Procedure

• Consent

• Locate puncture site

– Spinal cord ends at L1-L2 vertebral bodies

– Desired LP sites:

• Interspaces between L3-L4 or L4-L5

– Follow an imaginary line from the iliac crest to the spine

• Encounter L4-L5

• Use it or space cranial to it


• After locating the site of intended puncture

– Mark it by indentation of the skin with a

fingernail


• Sterile technique

– Wash hands; sterile gloves

– Cleanse skin with povidine-iodine solution

– Begin at the intended puncture site, & sponge in

widening circles

• Until an area of 10 cm in diameter has been cleanse

– Drape the child beneath their flank & over the back

• With the spine accessible to view


• Apply local anaesthetic

– Used in children > 1year age

– Raise a wheal with 1% lidocaine intradermal

– Then advance the needle into the desired

interspace, injecting anaesthetic

• Being careful not to inject it into a blood vessel / the

spinal canal


• Alternative:

– Use of EMLA applied to puncture site with occlusive dressing 60-90 minutes prior to puncture

– (EMLA = Eutectic mixture of local anaesthetics – lignocaine + prilocaine )

– http://archpedi.ama-assn.org/cgi/content/abstract/157/11/1065

– http://pediatrics.aappublications.org/cgi/content/full/114/5/1348/T2

http://archpedi.ama-assn.org/cgi/content/abstract/157/11/1065



http://pediatrics.aappublications.org/cgi/content/full/114/5/1348/T2

http://pediatrics.aappublications.org/cgi/content/full/114/5/1348/T2


• Prepare the spinal needle

– Check to ensure that the stylet is firmly in

position

• To prevent implantation of epidermoid tissue

• Have the stylet in place before advancing the needle


• Support the needle between your index

fingers

– & stabilize the hub of the needle with your

thumbs

• Grasp the spinal needle firmly with the

bevel facing up toward the ceiling


• With the needle perpendicular to the

vertical plane, but with the bevel pointed,

but the bevel pointed slightly cephalad • “towards the umbilicus”

– Advance through the skin


• Advance slowly into the deeper structures

– Until you detect a slight resistance on penetration of the

spinous ligaments

• The resistance continues until the needle

penetrates the dura

– At which time you will typically feel a “pop” sensation

• Caused by the change in resistance

• Indicates that you are in the subarachnoid space


• Remove the stylet

• Check for flow of spinal fluid

– If no CSF, rotate the spinal needle a few

millimeters forward, then re-check

– Repeat


• If the needle meets resistance

– Withdraw the needle with the stylet in place

– Reattempt the procedure

– Verify that the puncture site is in the correct

location

– If it is, attempt a paramedian approach

• Just a few millimeters later to the midline

Lumbar Puncture – Samples

• Note character of CSF

– If bloodly fluid flows originally

• Observe fluid for clearing with subsequent

collection

• If it does not clear this may indicate the presence of

a subarachnoid haemorrhage

Lumbar Puncture – Samples

• Replace the stylet & remove the needle

• Place a bandage over the site & encourage

the patient to lie prone for 3-4 hours

– To prevent leakage

Lumbar Puncture – CSF Analysis

• Send CSF for analysis for

– Cell count & differential

– Protein & glucose determinations

– Gram stain

– Routine culture

• Obtain a peripheral serum glucose level

immediately before the LP

– To determine the CSF serum ratio of glucose

Lumbar Puncture –

Complications

• Local pain or

backache

• Post-tap headache

• Vomiting

• Paralysis (low risk)

• Epidermoid tumours

• Subarachnoid

epidermal cyst

• Epidural haematomas

• Subdural or subarachnoid haemorrhage

• Spinal cord bleeding

• Acute neurologic / respiratory deterioration

• Hypoxaemia or apnoea

• Cerebral herniation

• Introduction of infection (low risk)

• Ocular muscle palsy (transient)

Lumbar Puncture – Treatment

• Do not delay antiobiotic therapy after obtaining

blood & urine culture as well as culture of any

apparent focal site of infeciton

• Begin age-appropriate empiric antibiotic therapy

• Repeat LP may be indicated with unsatisfactory

response after 48-72 hours of therapy

Lumbar Puncture – Treatment

Arterial Blood Gas

Arterial Blood Gas – Equipment

• Alcohol & betadine swabs

• Gloves

• 25 gauge needle / butterfly

• TB / 3 ml syringe

• Heparin

Arterial Blood Gas – Indications

• The need to evaluate the adequacy of

– Ventilatory

• PaCO2

– Acid-base

• pH and PaCO2

– And oxygenation (PaO2 and SaO2) status

– and the oxygen-carrying capacity of blood

(PaO2, HbO2, Hbtotal, and dyshemoglobins)

Arterial Blood Gas – Indications

• The need to quantitate the patient's response to

– Therapeutic intervention

– and/or Diagnostic evaluation (eg, oxygen therapy,

exercise testing

• The need to monitor severity and progression of a

documented disease process

Arterial Blood Gas –

Contraindications • Anticoagulant therapy

• History of a clotting disorder

– Haemophilia

• History of arterial spasms following previous punctures

• Severe peripheral vascular disease

• Abnormal or infectious skin processes at or near the puncture sites

• Arterial grafts

Arterial Blood Gas – Procedure

• Explain the procedure & obtain consent

• If using the radial artery

– An Allen test should be performed prior to

puncture

• Heparinize syringe

– Draw up 0.5 ml of heparin

– Rotate syringe & work plunger to distribute

heparin

– Minimal heparin should remain

• Expel remaining heparin

• Do not draw air back into the syringe

• Identify radial artery with gentle pressure

• Clean radial entry site

– Alcohol swab

– Povidone-Iodine solution (Betadine®)

• (Consider use of local anaesthetic at entry site

– (small skin wheal of Lignocaine 1%)


• Dorsiflexion of the wrist

– But not too much – makes the procedure more difficult

– May place a rolled towel under the wrist to help stabilize the site

• Have the patient make a fist

• Hold the needle in the dominant hand, as you would hold a dart

• Needle inserted

– Bevel up

– 25° for a superficial artery, 45° for a deep artery

– Against the flow of the artery


• Blood should flow spontaneously

– Or with gentle suction


• After the needle is removed

– Continuous pressure should be applied for 5 minutes

– (with care not to squeeze with the fingertips)

• If haematoma formation is prevented

– The artery may be used multiple times

• Observe the extremity for 15-20 minutes after the procedure

– For arterial spasm


• Express any air bubbles from syringe

• Cork needle / remove needle & cap syringe

• Roll syringe between fingers to mix heparinize the sample

• Immediately place sample on ice

• Label sample

– Patient identification data

– Sample acquisition time

– FiO2 at time of sample draw

– Patient’s body temperature

• Transport sample quickly to lab

Arterial Blood Gas –

Complications • Discomfort

• Infection

– Inadequate cleansing

• Haematoma

• Arteriospasm

• Thrombus formation

• Distal ischaemia

– No collateral circulation

• Numbness of the hand

– Nerve damage

Arterial Blood Gas – Erroneous

Results • Air bubbles

– Oxygen in the bubbles can diffuse into sample & CO2 can escape

• Changing the results

• Delay in cooling

– Blood cells at room temperature continue to

• Consume oxygen & nutrients

• & produce acids & CO2

– Thus, pH, blood gases & glucose values will change if specimen remains at room temperature for > 5-10 mins


Results

• Venous blood mixed in ABG sample

– Arterial blood = bright red

– Venous blood slightly darker

– Difficult to distinguish with poor oxygenation

– Best distinguishing feature: pulsation into

syringe


Results

• Improper anticoagulant

– Heparin accepted

– Oxalates, EDTA & citrates may alter pH

– Too much heparin

• Can cause erroneous results due to acidosis

– Too little

• Can result in clotting

Arterial Blood Gas – Specimen

Rejection

• Inadequate volume of specimen for the test

• Clotted

• Incorrect / no identification

• Wrong syring used

• Delay in delivering the sample for analysis

• Not placed in ice

• Air bubbles

Arterial Blood Gas – Conditions

diagnosed:

• Respirtory acidosis

• Respiratory alkalosis

• Metabolic alkalosis

• Metabolic acidosis

Arterial Blood Gas – Normal

Values

pH 7.35 – 7.45

PO2 75 – 100 mmHg

PCO2 35 – 45 mmHg

HCO3 22 – 26 mmol/L

SaO2 97-100%

Suprapubic Aspiration


• Gold standard for obtaining urine specimens

or culture

• Any growth of pathogenic bacteria in an

SPA specimen

– Is felt to be significant


• Technique is

– Simple

– Safe

– Rapid

– & Effective

Suprapubic Aspiration –

Indications

• Any child (regardless of age) who is unable

to void on request, who requires a urine

specimen for the diagnosis / exclusion of

UTI


Contraindications

• Bleeding diathesis

• Abdominal distension

• Massive organomegaly

Suprapubic Aspiration -

Complications • Uncommon

• Macroscopic haematuria

• Bladder haematoma (rare)

• Bladder haemorrhage (very rare)

• Intestinal perforation (rare, not usually clinically significant)

• Anaerobic bacteraemia or abscess formation (very rare)

Suprapubic Aspiration -

Equipment

• One assistant to hold the infant (not parent)

• Specimen jar for urine


Procedure

• Topical anaesthetic cream should be used

– Except where specimens are required urgently

• E.g. prior to starting antibiotic treatment in a septic

infant


Procedure

• Never undo the nappy until you have a

urine jar handy & someone ready to catch

• Do SPA first in a septic workup

– As the child may void while having

venepuncture / lumbar puncture


Procedure – Blind SPA has ~ 50% chance of obtaining urine

– Use of ultrasound increases the change of success to

80-90%

• Increased chance of successful chance in absence

of ultrasound:

– History of no voiding in the past 30 minutes; dry nappy

– Prehydration

– Bladder dull to percussion


Procedure

• Ask assistant to hold infant supine with legs

extended

• Ask parent to be ready to catch urine if the

patient voids

• Wipe the skin with an alcohol swab


Procedure • Identify insertion point

– Midline

– Lower abdominal crease

• Insert needle perpendicular to the skin

– Aspirating gently as you advance the needle

– If unsuccessful, withdraw the needle to just under the skin

• & advance at an angle with the needle aimed more away from the pelvis


Procedure

• If urine obtained

– Remove needle

– Squirt urine into sterile urine jar

Suprapubic Aspiration – Post-

procedure care

• Place a bandaid over the puncture site (optional)

• Warn parents that there may be a small amount of blood in the urine next day

– But they should re-present if there are large amounts

– Or if they are concerned

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