Transcript 1 MB - temperature monitoring

WARM ANAESTHESIA
GREETINGS
Dr . S.PARTHASARATHY
MD., DA., DNB
Dip. Diab. DCA, Dip. Software statistics
PhD (physio)
Mahatma Gandhi medical college and
research institute , puducherry – India
Why temperature??
Start with some tempo?
 No
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Temperature is a vital sign!!
History
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1776 – John hunter first measured
temperature
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1895 – Harvey cushing measured
temperature in anaesthesia
Skin and core
Skin temperature
– surface of the skin
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Core temperature
– temperature of blood in Main pulmonary
artery.
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Skin usually less than core
Normal 37*C± 0.2
Core – naso pharygeal,
 distal esophagus,
 tympanic,
 Rectal
 bladder , axillay and oral also
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All other skin surface – skin temperature
Normal regulation
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Sensors: Cells through out the body
,abdomen and thoracic tissues,
↓
Anterior hypothalamus:
↓
Posterior hypothalamus
↓
Effector organs
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Cold – A delta fibres
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Warm – C fibres
Vasoconstriction – AV shunts
Nutrition?
BP ?
Cold
warm
Behavioural
 Vasoconstriction
 Shivering
 Nonshivering.Th.
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anaest.
Normal
behavioural
vasodilation
sweating
anaest
-----------I-----------I-------I------------I-------------33
37
39
Heat loss
Radiation – infra red
 Convection – movement of air
 Conduction –contact loss
 Evaporation – as water vapour
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Nonshivering thermogenesis
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Non-shivering thermogenesis usually occurs in
brown adipose tissue (brown fat) that is present
in human infants (between scapulae)
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uncouples oxidative phosphorylation, and the
energy is dissipated as heat rather than
producing ATP from ADP
Hypothermia
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Anything below 36.7 !!
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But -- clinically below 35
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Severe -- when below 32
Feel of the cold
Hypo – what does it do??
↓ liver blood flow
 ↓ renal blood flow
 ↑ blood viscosity
 Shift of ODC
 Adrenergic surge
 Drug metabolism altered
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Hypo – what does it do??
↓ Cerebral blood flow
 ↓ heart rate.
 ↑ contractility
 ↓ Cardiac output
 Defib – ineffective
 ↓ ADH – cold diuresis
 pH measurement ?? Corrected.
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Periop Hypo – what does it do??
Wound infection is more
 Bleeding more
 Recovery delayed- Anaesth. and
Relaxants more action
 Mortality and cardiac events more.
 Shivering and its problems
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Some advantages
But it does give better outcomes in neuro
protection
 Intracranial aneurysm surgery
 It is useful in cardiac anaesthesia
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Operating room – what does it
do??
Cold environment, IV fluids
 Laminar flow
 Regional anaes. - vasodilation
 Body cavities washed with NS.
 Anaesthesia widens gap and relaxants
inhibit shivering
 With the exception of Ketamine all general
anaesthetics impair thermoregulation
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I unit blood
or
 1 litre crystalloid administered at room
temp.
 ↓ core temp by 0.25* C
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Hypothermia during GA develops
with a characteristic pattern
An initial rapid decrease in core
temperature core-to-peripheral
redistribution of body heat.
 Then - slow, linear reduction in core
temperature that results simply from heat
loss exceeding heat production.
 core temperature stabilizes and
subsequently remains virtually unchanged.
This plateau phase
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Regional
Prevents vosoconstriction and shiverring
 Cold receptors – concentrated in the legs
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Hypothermic patient feeling warm
sometimes – clinical paradox.
Incidence of hypo-- 60% ??
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Prevention
Radiant heat lamps.
Warm blankets.
Warm OR
Closed circuit.
Warm IV fluids.
Forced air circulation –the best
Humidifiers
 Heat and Moisture Exchangers ( HMEs)
 Oesophageal Rewarmers
These devices consist of a double
lumen esophageal tube through which
water is circulated at upto 42°C
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Blankets- IV warmer- warmed IVF
shivering
involuntary contractions of muscles, in
response to the chilling effect of low
temperatures.
 Shivering may also occur at the onset of a
fever when the body's heat balance is
disturbed.
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Tonic phase 4-8 cycles/min.
 Clonic phase. 5-7 Hz
 Clonic phase may resemble fits.
 Incidence 40%
 Clonic more common after inh. Agents
 Nonthermoregulatory tremors in labour.
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shivering
↑ IOT
 ↑ ICT
 ↑ O2 consumption
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Hence a big no in IHD patients.
Shivering – treatment
Clonidine 75 µg
 Pethidine 25 mg
 Tramadol 50 mg
 Ondansetron 4 mg IV
 Others like doxapram,
ketanserin,physostigmine,magsulf used.
 Hence the mechanism of shivering!!
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After cold, we move to hot
Hyperthermia
Atropine,ether, allergy, mismatched blood
 infection, inflammation
 Blood in 4th ventricle.
Atropine and sweating!!
To cool,
 Refrigerated IV fluids.
 Endovascular cooling with heat exchange
catheters
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Malignant hyperthermia!!
is a rare life-threatening condition
 triggered by exposure to IAS
 skeletal muscle oxidative metabolism,
which overwhelms the body's capacity to
supply oxygen, remove carbon dioxide,
and regulate body temperature, eventually
leading to circulatory collapse and death if
not treated quickly.
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Symptoms
Autosomal dominant
 Males more
 1:20,000
 Masseter spasm and ↑ ETCO2
 Tachycardia, tachypnoea, arrythmias,
unstable BP, hyperkalemia ,myoglobinuria
renal failure
 coma
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C O D S C U P- pneumonic
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Circuit
Oxygen
Dantrolene 3 mg/kg , Azumolene is a 30-fold
more water-soluble analogue of dantrolene
Supportive measures,Soda bicarb
Cold washes
Urine – mannitol, frusemide.
Potassium disturbance
Preop check up
Family history.
 ↑ CPK
 Positive muscle biopsy
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Avoid IAS
Probes
Thermistors are made from certain metal
oxides whose resistance decreases with
increasing temperature.
 resistance falls off with increasing
temperature
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Thermocouples are based on the effect
that the junction between two different
metals produces a voltage which
increases with temperature.
 clear advantage of a higher upper
temperature limit, up to several thousand
degrees Celsius.
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Indications of temp. monitoring
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Adults – surgery more than 30 minutes
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All children.
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Major iv shifts
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Nasopharygeal or axillary is ok
Carry home message
Temperature is a vital sign.
 Hypo and hyperthermia has significant
dangerous repercussions in anaesthesia
 Are we monitoring?
 Are we taking precautions?
 Are we noting morbidity??
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Thank you