ANAESTHESIA A (38)

Question 1

KIDS ETT SIZES & DEPTHS

Answer 1

At birth, a N kid weighs 3.0kg and takes a 3.0 ETT, then:

• At 6/52: 3.5
• At 6/12: 4.0
• from 1y: (age/4 +4)
• (go down a size if cuffed)
• ET Depth = 10 cm at birth, then : 1/2 age + 12cm (+15cm if nasal)

Question 2

3 CONSIDERATIONS FOR SAFE USE OF CUFFED ETT IN CHILDREN

Answer 2

1. correct size: go down a size
2. correct depth: must be below cricoid
3. correct pressure: not >25 cm H2O, pref <15

Question 3

KIDS WEIGHT FORMULA

Answer 3

• At birth, the typical kid weighs: 3kg
• At 1yr: 10kg
• From 1-10yr: ‘twice age + 8kg’

Question 4

KIDS MAINTAINENCE FLUID FORMULA

Answer 4

Maint =

• 4ml/kg/h for first 10kg
• 2ml/kg/h for next 10kg
• 1ml/kg/h then on

Ie, a 30 kg kids needs 70ml/hr

Question 5

KIDS CVS PARAMETERS

Answer 5

• Neonates: HR = 160, BP = 70/
• Infants: HR = 120, BP = 90/
• Small children: HR = 100, BP = 100/
• Adolescents: HR = 80, BP = 120/

Question 6

KIDS RESPIRATORY RATES

Answer 6

• Neonates/infants = 40
• Small children = 30
• Adolescents = 20
• Adults = 15

All breathe with a tidal volume of 7ml/kg, of which 3ml/kg is anatomical deadspace. We ventilate at 10 ml/kg to allow for circuit dead space

Question 7

ADULT, INFANT & CHILD, AND NEONATAL ALS* RATIOS

Answer 7

• ADULT ALS: begin with 30 compressions at 2/sec, then 2 breaths, and repeat
• INFANT & CHILD ALS: begin with 15 compressions at 2/sec, then 2 breaths and repeat
• NEONATES: begin with 15 breaths over 30s, then 3 compressions and one breath every 2s

* BLS, however, uses the same 30:2 ratio for all ages

Question 8

FASTING KIDS

Answer 8

• <6/12: 4h for milk and solids, & 2h for clear fluids
• >6/12: 6h for milk and solids, & 2h for clear fluids
• Adults: 6h for solids, & 4h for clear fluids

Question 9

NG vs NJ FEEDING TUBES AND FASTING

Answer 9

as a general rule, GASTRIC feeds (NG, OG and PEGS) need to be stopped 6h before surgery whereas JEJUNAL feeds do not

Question 10

CLASSIC LMA SIZES

Answer 10

• 1 = <6kg
• 2 = 6-20kg
• 2.5 = 20-30kg
• 3 = adult female
• 4 = adult male
• 5 = Shrek

Question 11

OPA AND NPA SIZING

Answer 11

• OPAs are “ANGLE to ANGLE” *
• NPAs are “NOSTRIL to EAR’” **
• * angle of the mouth to angle of the jaw*
• ** nostril to EAM*

Question 12

MINIMUM AGE AND WEIGHT LIMITS FOR AED*s USING ADULT PADS

Answer 12

• not <8y
• not <12kg

* realising few collapsed children will have defibrillatable rhythms anyway

Question 13

FIRST AID FOR THE CHOKING CHILD OR ADULT

Answer 13

1. if coughing effectively, leave alone to cough
2. if not, give 5x (single*) back blows, pausing after each to check effect
3. if still obstructed, give 5x chest thrusts**, again pausing after each to check effect
4. if loses consciousness, commence CPR and attempt larngoscopic clearance ASAP

• * the aim being to clr the obstruction with each one*
• ** each like a CPR chest compression*

Question 14

LARYNGOSPASM

Answer 14

• is caused by spasm of the false cords, not the true cords, so it’s a powerful deep obstruction that cannot be overcome by forced intubation without risking severe damage
• can often be broken by applying painful pressure with the fingertips holding the mask around the angle of the jaw

Question 15

DESIRABLE TEMPERATURE FOR A TRAUMA THEATRE?

Answer 15

• HOT, at least 30 C! …. KAF was 33C

Question 16

ANGIOEDEMA

Answer 16

• Angioedema = localised swelling of the mucosa of the lips and upper airway, most commonly due to HISTAMINE mediated allergic reactions to food or drugs, and thus responsive to normal anaphylaxis treatment (esp neb Adrenaline)
• Less commonly, PERIODIC ANGIOEDEMA may be caused by a Hereditary defect in the ‘C1 ESTERASE INHIBITOR’ enzyme, leading to excess BRADYKININ activity. Such cases do not respond to usual anaphylaxis treatment* and instead require
  
  • airway support (but rarely intubation, however swollen)
  • C1 Esterase Inhibitor replacement with donor concentrates or FFP
  • Bradykinin receptor blockers eg ICATIBANT
• ACE Inhibitor associated Angioedema is increasingly seen and may also be Bradykinin related

* Teubner still thinks neb Adrenaline is useful

Question 17

4 Causes of PPH

Answer 17

1. TONE (uterine atony)
2. TEARS
3. TISSUE (retained placenta)
4. THROMBUS (coagulation defect)

Question 18

THE HAEMATOLOGY OF PPH

Answer 18

• Pro-thrombotic changes occur in preparation for delivery, with a doubling of clotting factor levels, and concommitant reductions in APTT & INR.
• In consequence:
  
  • Coagulopathy develops late in PPH (although still early in abruption & AFE)
  • [FIBRINOGEN] targets in PPH have now doubled to 2.0g/l

Question 19

OXYTOCIN, SYNTOCINON, ERGOMETRINE and SYNTOMETRINE

Answer 19

These are all uterotonic agents:

• OXYTOCIN is a Posterior Pituitary Hormone responsible for milk ejection during lactation, and uterine contraction.
• Synthetic Oxytocin (SYNTOCINON) may be administered to drive labour or reduce PPH, typically in a dose of 5-10u IV at delivery, +/- an infusion of 40u in 1000mls @ 250 mls/h
• ERGOMETRINE is a uterotonic agent derived from the toxin of the ERGOT fungus, which caused epidemics of gangrene and miscarriage in the middle ages. In addition to its uterotonic effect, it’s also a powerful VENOCONSTRICTOR (!) so its usually given IMI, in a dose of 500mcg, but can be given slow IV in emergency
• SYNTOMETRINE combines the 2 agents, with 5u of Synthetic Oxytocin and 500mcg of Ergometrine

Question 20

WHATS CARBETOCIN?

Answer 20

• CARBETOCIN is a single shot long acting synthetic Oxytocic now replacing SYNTOCINON at delivery in FMC, although its not approved for GA sections (? why)
• DOSE : 100 mcg slow IV x1

Question 21

POST PARTUM PULMONARY OEDEMA

Answer 21

• following a natural delivery, the placenta detaches and the uterus contracts in a relatively slow process which returns ~ 1000 mls of blood to the maternal circulation over ~ 1/2 an hour
• artificially accelerating this process with bolus oxytocics can precipitate failure in a mother with a cardiac Hx

Question 22

DURAL TAP PROTOCOL

Answer 22

PDPHA can be much reduced by:

1. feed catheter to +2cm (prox hole is at +1.5)
2. label “Anaesthetist top up only”
3. topup 1/24 prn with 1-2mls R2F4
4. remove at +24h and culture tip

(the catheter reduces initial CSF loss, and initiates the inflammation which will subsequently seal the hole)

Question 23

WHAT IS AFE?

Answer 23

AFE is thought to be an ANAPHYLACTOID response to the entry of AMNIOTIC FLUID into the maternal circulation, with:

• bronchospasm
• hypotension
• coagulopathy
• seizures

treatment is supportive

Question 24

WHICH LSCS DRUGS CROSS THE PLACENTA?

Answer 24

• Lipid soluble drugs, like Propofol, opiods and Vapors easily cross the placenta, but muscle relaxants do not
• so infants born by GA SECTION may be anaesthetised but they will not be paralysed

Question 25

MATERNAL HAEMODYNAMIC CHANGES IN PREGNANCY

Answer 25

1. modest rises in HR & CO
2. modest falls in BP
3. blood volume rises by 40%, but red cell mass by only 30%, producing a relative anaemia

Question 26

HOW MUCH BLOOD IS NORMALLY LOST AT NVD AND CAESARIAN?

Answer 26

• up to 500mls at NVD
• up to 750 mls at caesarian

healthy parturients can accomodate up to 1000mls loss without significant clinical symptoms

Question 27

ROLE OF UTERINE MASSAGE IN PPH?

Answer 27

• Uterine massage is an important first aid measure in PPH, producing uterine contraction, ? via local PG release.

Question 28

WHAT IS HELLP SYNDROME?

Answer 28

HELLP SYNDROME = the combination of

• Haemolysis
• Elevated LFT
• Low platelets

sometimes seen in pregnancy (cause?)

Question 29

MATERNAL RESPIRATORY CHANGES IN LATE PREGNANCY

Answer 29

• pCO2 falls to ~30mmHg in late pregnancy due to increased minute volume:
• ‘normal’ pCO2 can indicate incipient respiratory failure!

Question 30

SUGAMMADEX

Answer 30

REVIEW:

• conventional reversal of NM Blockade uses ACETYLCHOLINESTERASE inhibitors like NEOSTIGMINE to increase ACHO concentrations in the synaptic cleft, where it competes with the blocker molecules for access to the Nicotinic receptors of the NMJ.
• this sort of COMPETITIVE REVERSAL is only effective at modest depths of blockade
• SUGAMMADEX is a direct acting reversal agent which binds and inactivates Aminosteroid relaxants (Roc>Vec>>Panc, but not Atrac) and so can reverse even profound block. DOSE:
  
  • Normal reversal: 200mg (4mg/kg)
  • Emergency : 16mg/kg (both are effective in 1-2 mins)

Question 31

SCOLINE APNOEA

Answer 31

• SUCCINYL CHOLINE mimics ACHO, binding to the NMJ and triggering contraction (then exhaustion). It occupies the receptor for 1-2 minutes before being metabolised by circulating PSEUDOCHOLINESTERASE, and muscle function returns.
• 1 person in 33 has one defective copy of the pseudocholinesterase gene, prolonging the action of scoline to 5-10m, although this is rarely evident clinically, & 1/1000 have 2, prolonging duration to many hours.
• DIAGNOSIS:
  
  • failure to regain muscle power after administration of Scoline (and despite Reversal - given for co-administered NONDEPOL relaxants)
  • no twitches
  • subsequent low activity on Pseudocholinesterase assay
• TREATMENT: supportive: ventilate until resolves

Question 32

THYROID HORMONES, TFTs AND THYROID REPLACEMENT THERAPY

Answer 32

• Anterior Pituitary TSH drives the thyroid to produce its 2 main* hormones:
  
  • T3 - TRI-IODOTHYRONINE
  • T4 - THYROXINE
• Production is predominantly the long lasting T4, and this is converted peripherally to the short lived active form, T3, which drives metabolic rate.
• THYROID FUNCTION is principally assessed by measuring TSH & T4 levels.
  
  • normal TSH levels indicate N thyroid function (or adequate replacement) whereas raised levels indicate Thyroid failure (or occasionally Pituitary Tumour)
  • normal T4 levels indicate adequate thyroid hormone production (or replacement)
• THYROID REPLACEMENT therapy is usually solely (synthetic) T4, with subsequent peripheral conversion to T3 in the usual manner.

* the thyroid also produces the minor Calcium regulating hormone CALCITONIN, but this is secondary in importance to PARATHYROID hormone and Ca metabolism remains normal after thyroidectomy.

Question 33

ADRENAL CORTEX FUNCTION AND ADDISONS DISEASE

Answer 33

Anterior Pituitary ACTH drives the Adrenal Cortex to produce 2 steroid hormones:

• CORTISOL, which regulates BSL & metabolism
• ALDOSTERONE, which regulates salt and water balance

ADDISONS DISEASE occurs when the Adrenal cortex stops producing these hormones, due to either:

• Loss of central drive
• Adreno-cortical failure, eg due to autoimmune attack or severe illness

It results in

• Hypoglycaemia
• Hypovolaemia, hyponatrema and hyperkalemia → may present with circulatory collapse, an ‘ADDISONIAN CRISIS’
• Skin hyperpigmentation
• Nausea and vomiting
• Muscle pain and weakness

Rx

• Address hypoglycaemia and dehydration
• Replace CORTISOL with HYDROCORTISONE*
• (consider) ALDOSTERONE replacment with FLUDROCORTISONE (often unneccesary)
• Address the cause if able

*Cortisol = Hydrocortisone,

Question 34

HOW TO INSERT DOUBLE LUMEN TUBES

Answer 34

1. chose the correct tube, a LEFT* 39 French for the typical M, and 37 for F
2. put stylet into ENDOBRONCHIAL Lumen and bend Left
3. rotate tip anteriorly, place thru cords & remove stylet
4. holding well proximally, corkscrew L 90 degrees whilst pushing firmly home to ~ 29cm at the teeth
5. inflate TRACHEAL cuff (5-10ml) & check bilat AE**
6. inflate BRONCHIAL cuff (1-2ml) & check bilat AE**
7. isolate and check each side - if wrong sided, insert fibrescope to tip of Bronchial lumen and pull back to carina under direct vision then direct into opposite side (if lost: recall that the cartilage arch is deficient posteriorly)

• * Left sided tubes are generally suitable for procedures on either lung, R sided tubes are only for surgery on the L main bronchus*
• ** loss of one side, as per normal ETT, usually = too far in*

Question 35

DEALING WITH HYPOXIA DURING ONE LUNG ANAESTHESIA

Answer 35

assuming the DLT is correctly sided and not too deep, (the usual cause) hypoxia likely represents ongoing shunting through the collapsed upper lung: manage via

• start with no lower lung PEEP (reduces blood diversion to upper)
• add 5 cm lower lung PEEP
• add 5 cm upper lung CPAP
• discuss with the surgeon clamping the upper lung vessels or returning to 2 lung ventilation

Question 36

MINUTE AND TIDAL VOLUMES DURING ONE LUNG ANAESTHESIA

Answer 36

• normal minute volumes can generally be achieved with only modest decreases in TV and increases in rate, so NORMOCAPNOEA can usually be maintained

Question 37

2012 FIBREOPTICS WITH DEVILBISS

Answer 37

1. DRY UP FIRST
   
   • Atropine 1.2mg O with a sip 1/24 prior
   • Glyco 200 IV on arrival
2. SEDATE AS NEEDED
   
   • Fentanyl 75-100 mcg, not Midaz (Currie)
3. TOPICALISE ORAL
   
   1. Gargle 4% Lignocaine
   2. consider cricoid puncture
   3. Load DeVilbiss with 10mls 4% Lignocaine and 5 lpm
      
      • spray 2m back of throat (til gag lost)
      • spray 2m around corner (till voice change)
      • use reversed guedel between molars as bite block and proceed
4. IF NASAL
   
   1. as above, plus topicalise nose with atomizer or buds
   2. use 6.0 and just feed scope to start
   3. stand in front, keep tight, advance under constant vision

Question 38

TYPE 1 VS TYPE 2 RESPIRATORY FAILURE, DEF AND MECH

Answer 38

• TYPE 1 Respiratory Failure = HYPOXIC, and is generally due to:
  
  • Shunt/V/Q mismatch
  • Hypoventilation*
• TYPE 2 Respiratory Failure = HYPERCAPNOEIC, and is generally due to:
  
  • hypoventilation.

* hypoventilation increases alveolar CO2, ‘crowding out’ oxygen