Transcript tutorial 7

EVALUATION
Clinical – History & Physical
 Laboratory
 Hemodynamic
- All parameters are indirect, nonspecific
measures of volume
- Serial evaluations necessary ≈ fluid therapy
- Modalities should complement one another
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PHYSICAL
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Most reliable preoperatively
 Skin turgor, hydration of mucous
membranes, fullness of peripheral pulse,
capillary refill, resting HR & BP and
changes from the supine to sitting or
standing position, urinary excretion and
fontanels in babies.
LABORATORY
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Serial hematocrits
 Arterial blood pH
 Urinary specific gravity/osmolality >1.01/450
mOsm/kg
 Serum blood urea nitrogen (BUN)-to-creatinine
ratio > 10:1
Indirect indices of volume, esp intraoperatively
 Only X-ray signs reliable measures of volume
overload – Kerly B lines or intestitial markings
HEMODYNAMIC
CENTRAL VENOUS PRESSURE (CVP)
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Cardiac output is based on the Frank starling
mechanism where force of contraction is
determined by the initial fiber length and the
contractility of cardiac muscle to determine stroke
volume
 We do not measure stroke volume, so pressure is
used as a surrogate
 The placement of a central venous catheter with its
tip at junction SVC & RA provides measurable
parameter of volume status or preload of patient
PULMONARY ARTERY PRESSURE
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In the normal individual CVP measurement
provides a reasonably accurate estimate of the
filling pressures of both R & L atria. In some
situations not, and infusion of fluids or inotropic
agents titrated against CVP may not result in
optimum cardiac function
LV failure with pulmonary oedema
Interstitial pulmonary oedema of any cause
Chronic pulmonary disease
Valvular heart disease
PULSE PRESSURE VARIATION
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Ventilation causes changes in intrathorasic
pressure, influences cardiac filling
Responsible variation in BP during ventilation
Identify highest and lowest BP
Subtract highest DBP from highest SBP and
lowest DBP from lowest SBP
Render pulse pressure variation
Divide diff btw HPP & LPP by mean X 100
Highest SBP = 100 mmHg
Highest DBP = 60 mmHg
Lowest SBP = 90 mmHg
Lowest DBP = 55 mmHg
HPP = 100 – 60 = 40 mmHg
LPP = 90 - 55 = 35 mmHg
Difference btw HPP & LPP = 40 – 35 = 5 mmHg
Mean PP = (40+35) / 2 = 37.5 mmHg
therefore the PPV = (5/37.5) x 100 = 13.3%
> 12% indication of hypovolaemia ~ respond fluid
volume, < 8% non-responders, 8-12 grey area
INTRAVENOUS FLUIDS
Crystalloids, Colloids or both
 Crystalloids ~ aqueous sol low-molecular-weight
ions (salts) ± glucose
 Colloids ~ high-molecular-weight sub
:- Protein colloids – Albumin
:- Non protein colloids –
gelatins (haemaccel, gelofusin)
hydroxyethylstarchs (voluven, venofundin)
sugars (dextrans)
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Replacing intravascular volume deficit with
crystalloids ~ 3X volume needed using colloids
Intravascular fluid deficits ~ more rapidly
corrected using colloid solutions
Surgical patients ~ extracellular fluid deficit >
intravascular deficit
Rapid administration of large amounts of
crystalloids (>4-51) more frequently associated
with significant tissue oedema
Intravascular ½ life crystalloids 20-30 min,
colloids ½ life 3-6 hours
PERIOPERATIVE
FLUID THERAPY
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Replacement: pre-existing deficits, maintenance
requirements and surgical wound losses
 Maintenance fluid requirements
Weight
Rate
For the firs 10 kg
4ml/kg/h
For the next 10-20 kg
Add 2ml/kg/h
For each kg above 20 kg
Add 1mi/kg/h
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70 kg person fasting for 8h amounts to:
(40 + 20 + 50) ml/h X 8h = 880 ml
BLOOD
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Volume
 Oxygenation
 Clotting
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Prem 95ml / kg
 Neonate 90ml / kg
 > 3month 80ml / kg
 > 1y 70ml / kg
 MABL = EBV × ( I Hct – F Hct) /
Mean Hct
Mean Hct = ( I Hct + F Hct ) / 2
Whole blood = ( F Hct – I Hct) × Kg × 2.5
Packed RBC = (F Hct – I Hct) × Kg × 1,5
DO2 = CO × CaO2
= (70 × 72) × [ (Hb × 1,34 × SaO2 ) +
(0,031 × PaO2) ]
= 5 × 200ml
= 1000ml/min
 Extraction ~ 200ml/min
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COMPLICATIONS OF
BLOOD TRANSFUSIONS
HEMOLYTIC REACTIONS
Involves specific destruction of transfused RBC by
recipient’s antibodies, less common – hemolysis
recipient’s RBC due to transfusion of antibodies
ACUTE HEMOLYTIC REACTIONS
Fatal 1:100000
In awake patients – chills, fever, nausea, chest and flank pain.
In anaesthetized pts -↑ temp, ↑HR, hypotension,
hemoglobinuria and diffuse oozing in surgical field.
Disseminated intravascular coagulation & renal shutdown
Severe with as little as 10-15ml ABO-incompatibility
MANAGEMENT OF
REACTION
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Hemolytic reaction suspected ~ stop transfusion
 Recheck identity bracelet against blood slip
 Draw blood for Hb, compatibility, platelet count
& coagulation studies
 Urinary catheter inserted & urine checked for Hb
 Osmotic diuresis initiated with mannitol & iv
fluids
 Presence of rapid blood loss – Platelets & FFP
DELAYED HEMOLYTIC REACTIONS
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Following ABO & Rh-compatible
transfusion, 1 – 1.6% chance antibodies
against Kell, Duffy, Kidd etc antigens
 Extravascular hemolysis
 Mild – malaise, jaundice & fever 2-21 days
after
 Treatment primarily supportive
NONHEMOLYTIC REACTIONS
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Sensitization of the recipient to donor white cells,
platelets or plasma proteins
Febrile reactions
Urticarial reactions
Anaphylactic reactions
Noncardiogenic pulmonary oedema
Graft-Versus-Host disease
Posttransfusion purpura
Immune suppression
ANAPHYLAXIS
Definition: Allergic condition which results
from an antibody-antigen reaction rapidly
after the antigen entered the systemic
circulation.
Signs:
Resp: Bronchospasm, laryngeal oedema
CVS: Circulatory collapse – hypotension
Skin: Wheel & flare
Management
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Initial Therapy
- Stop drug
- Call for help
- Airway management
- Feet elevation
- Drug Rx Adrenaline:
0.5 – 1mg IMI/10min
50 – 100μg IVI/ 1min (hypotension)
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Secondary Therapy
- Antihistamines
- Corticosteroids
- Catecholamine infusion
Adrenaline 0.05 – 0.1 μg/kg/min
- Blood gas acidosis consider
Bicarbonate 0.5-1 mmol/kg
- Airway evaluation before extubation
- Bronchodilators in persistent
bronchospasm
Investigations:
-Only after emergency treatment has been
completed
- Dx on clinical grounds
- Bloods: Serum tryptase concentration
1 hour after reaction 10ml red top
centrifuge and store @ -20ºC until send to
Lab
- Patient and GP must be alerted toward the
reaction and drug causing it.
Potentially 
OBESITY
BMI – Body Mass Index is the weight (kg) divided
by the square of the height (m)
Normal range 18-25
Overweight >27
Obese >30
Morbid obesity >35
Massive morbid obesity >40
? modeling not <18
Broca Index - normal weight (kg) = height (cm)
minus 100 for males or 105 for females
- children weight (kg) = 10 + 2  age
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Distribution – truncal, buttocks
Respiratory - Difficult intubation
-  FRC
-  work of breathing,  chest compliance
-  risk of aspiration:  gastric volume,
: Hiatus hernia
:intra- abdominal pressure
- Obstructive sleep apnea esp after GA or
opioids, PCA ~ safer
Nocturnal CPAP nasal oxygen mask
Apnea monitor
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Cardiovascular -  blood volume and CO
Difficult: IV access
: BP measurement (cuff size –20% > arm
diameter ) arterial line
PCA better than IM opiods
Tromboprophylaxis & mobilization post-op
Medical conditions – Diabetes mellitus, Cushing’s
syndrome, hypothyroidism, syndromes (PraderWilli or Lawrence-Moon-Biedl)
Table max 150kg
LARYNGOSPASM
Definition – Acute glottic closure by the vocal
cords
Presentation – Crowing or absent inspiratory
sounds and marked tracheal tug
Differential diagnosis - Bronchospasm
- Laryngeal trauma / airway oedema
- Recurrent laryngeal nerve damage
- Tracheomalacia
- Inhaled foreign body
- Epiglottitis or croup
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Management
Avoid painful stimuli
Remove irritants from airway
100% oxygen
CPAP mask, jaw thrust
? Deepen anaesthesia
Intractable: Muscle relaxation and intubation
PACEMAKERS
Indications – Third degree heart block
Mobitz type II block
Trifassicular block: RBBB
: Left ant/post hemiblock
: First degree heart block
Sick sinus syndrome
Symptomatic bradycardia
Post MI, HOCM, torsade de pointes
Pacemaker code
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Position 1- chamber(s) paced
Position 2- chamber(s) sensed
Position 3-response to a sensed elect. Signal
Position 4- rate modulation
Position 5- multi-site pacing
Pacemaker code
1
2
3
4
5
Chamber
paced
Chamber
sensed
Response
Rate modu Antilation
tachycardi
a
A=atrium
V=ventricle
D=dual
0=none
A=atrium
V=ventricle
D=Dual
0=none
I=inhibit
T=trigger
D=dual
0=none
R=rate mod
P=pacing
S=shock
D=dual
ICD code
1
2
3
4
Shock
chamber
Chamber
anti-tachy
pacing
How tachy Pacemaker
is sensed
code
0=none
A=atrium
V=ventricle
D=dual
0=none
A=atrium
V=ventricle
D=dual
E=intracardiac
electrogram
H=haemodyna
means
above
Anaesthetic implications
- Follow up clinic, function
- Pre-op ECG : Absence of all spikes may represent
appropriate sensing or total failure!
- Loss of capture : Hypokalaemia
After defibrillation
MI over lead
Toxic levels of local anaesthetic
Lead dislodgement
- Bipolar diathermy safe
- MRI