1. BY: DR. HUNNY NARULA
MODERATOR: DR. CHANDRAKANTA
SACHDEVA

2.  Shivering is known to be a frequent
complication, reported in 40-70% of patients
undergoing surgery under regional
anaesthesia.
 Shivering is very unpleasant, physiologically
stressful for the patient undergoing surgery,
and some patients even find the
accompanying cold “sensation to be worse
than surgical pain.”

3.  The aim of this prospective double-blind
randomized clinically controlled study was to
compare the efficacy, potency,
haemodynamic effects, complications and
side effects of clonidine with those of
tramadol for control of shivering.

4.  Increased metabolic rate;
 Increased oxygen consumption(upto100-
600%) along with increased CO2 production;
 Ventilation and C.O.;
 Adverse post operative outcomes such as
wound infection;
Increased surgical bleeding; and
Morbid cardiac events.

5.  Arterial hypoxemia,
 Lactic acidosis,
 Increased IOP, ICT
 Interferes with pulse rate, BP, and ECG
monitoring.
 Shivering per se may aggravate postoperative
pain, simply by stretching of surgical
incision.

6. Neuraxial anaesthesia induced inhibition of autonomic
thermoregulatory responses below the level of block
Peripheral vasodilatation(sympathetic blockade)
Increased blood flow to the skin
Heat loss l/t decreased core body temprature
Cold temp. Rapid infusion of
Cutaneous vasoconstriction cold iv fluids
of OT
SHIVERING THRESHOLD
Increased muscle activity

7. However, in the postoperative period,
muscle activity may be increased even with
normothermia, suggesting that mechanisms
other than heat loss with subsequent
decrease in the core temperature contribute
to the origin of shivering. These may be
uninhibited spinal reflexes, sympathetic
over-activity, postoperative pain, adrenal
suppression, pyrogen release and
respiratory alkalosis.

8.  Approval from ethical committee & written
informed consent,
 80 ASA grade1 patients, of either sex
 Age 18-40yrs,
 Scheduled for elective abd., orthopaedic,
and gynaecological surgeries e.g. inguinal
herniorraphy, abd. or vaginal hysterectomy, K
nailing, dynamic hip screw under spinal
anaesthesia without any prior pre-medication

9.  Patients with known history of alcohol or
substance abuse, hyperthyroidism,
cardiovascular diseases, psychological
disorder, severe diabetes or autonomic
neuropathies and urinary tract infection.
 Patients with KNOWN HYPERSENSITIVITY TO
CLONIDINE and TRAMADOL.

10. Patients who developed post-spinal
anaesthesia shivering were randomly
allocated to two groups:
Group C Group T
(n=40) (n=40)
iv iv
Clonidine(0.5mcg/kg) tramadol(0.5mg/kg)

11.  Subarachnoid block was given with inj.
Bupivacaine 0.5% (10-15 mg) at L 3-4 or L 4-
5 interspace using 25 gauge Quincke's needle,
and blockage up to T 9-10 dermatome was
achieved.
 All operation theatres in which the operations
were performed maintained constant humidity
(70%) and an ambient temperature of around
21°C to 23°C.
 Oxygen was administered to all the patients of
both groups at a rate of 5 L/min with face mask,
and patients were covered with drapes but not
actively warmed. No means of active re-warming
were used.

12.  Intravenous fluids and anaesthetic drugs were
administered at room temperature.
 Preloading was not done in both the groups as
they did not want intravenous fluid to influence
the onset of shivering mechanism.
 Before beginning of spinal anaesthesia, standard
monitoring procedures were established.
Standard monitoring of pulse rate was done, and
non-invasive blood pressure (NIBP), oxygen
saturation (SPO 2 ), body temperature (axillary)
were recorded before the commencement of
surgery and thereafter at every 5 minutes from
the baseline ie subarachnoid block (SAB), for 1
hour; and every 15 minutes, for the rest of the
observation period.

13. GRADING OF SHIVERING was done as per Wrench, [6]
which is as follows:
Grade 0: No shivering
Grade 1: One or more of the following: Piloerection,
Peripheral vasoconstriction, peripheral cyanosis with,
but without visible muscle activity
Grade 2: Visible muscle activity confined to one
muscle group
Grade 3: Visible muscle activity in more than one
muscle group
Grade 4: Gross muscle activity involving the whole
body
 Patients who developed either grade 3 or grade 4 of
shivering were included in the study.

14.  The attending anaesthetist recorded the time in
minutes at which shivering started after spinal
anaesthesia (onset of shivering), severity of the
shivering, time to disappearance of shivering (in
minutes) and response rate (shivering ceased
after treatment in 15 minutes).
 If the shivering did not subside by 15 minutes,
the treatment was considered to be not
effective.
 Recurrence of shivering was also noticed until
the patient left the operation theatre. Patients
who did not respond or in whom recurrence of
shivering occurred were treated with additional
dose of clonidine (0.5 μg/kg IV) or tramadol (0.5
mg/kg IV) in the respective groups, if required.

15.  Duration of surgery was noted, and duration
of spinal anaesthesia was recorded by
assessing spontaneous recovery of sensory
block using pin-prick method and
observing spontaneous movements of limbs
in the postoperative period.
 Side effects like nausea, vomiting,
bradycardia (<50/min), hypotension (>20% of
baseline), dizziness; and sedation score were
recorded.

16. SEDATION SCORE was assessed with a four-
point scale as per Filos:
1. Awake and alert
2. Drowsy, responsive to verbal stimuli
3. Drowsy, arousable to physical stimuli
4. Unarousable

17.  STATISTICAL ANALYSIS was done using
suitable statistical software, and
Student t test and Chi-square test were
applied for the interpretation of results.
A P value <.05 was considered statistically
significant.

18. RESULTS:

20. Shivering disappeared in:
 39(97.5%) patients in group C, and
 in 37(92.5%) pts in group T(out of 40 in each
group.)
 BOTH THE GROUPS WERE FOUND TO BE EEFECTIVE IN
REDUCING SHIVERING
One patient in group C (severity of shivering
unchanged) and 5 patients (3- severity of
shivering unchanged; 2- recurrence of shivering)
in group T were given rescue doses of clonidine
or tramadol, respectively.
 Six (7.5%) patients out of a total of 80 patients
received rescue doses.

21. 

22.  The mean interval between the injection of
drug (clonidine and tramadol) and the
complete cessation of shivering was
2.54±0.76 and 5.01±1.02 minutes,
respectively (P=.0000001).
 Time for onset of shivering and severity of
shivering were not statistically significantly
different between the two groups. However,
the time interval between administration of
drug after onset of shivering and
disappearance of shivering was significantly
shorter in the clonidine group(P=.0000001).

24.  There was no statistically significant difference
with respect to heart rate, mean blood pressure,
axillary temperature and oxygen saturation
between the two groups.
 Complication rates were significantly higher in
group T than in group C. Nausea, vomiting and
dizziness were higher in group T [nausea - 31;
vomiting - 8; and dizziness - 22) than in group C.
More patients of group C (10 patients) were
sedated than of group T (5 patients).
 Complications in both groups:
Bradycardia occurred in 2 patients of group C
and 1 patient of group T. In group C, 3 patients
suffered from hypotension, and 1 patient
complained of dry mouth, both of which were
not present in group T.

25. A limitation of this study is that the core
body temperature could not be measured.
For measurement of core body temperature,
the probe needs to be put in the oesophagus
or near the tympanic membrane. Both these
are uncomfortable and unacceptable who has
been given spinal anaesthesia. Rectal
temperature monitoring was a possibility but
was not tried.

26.  Centrally acting selective α2 agonist.
 It exerts anti-shivering effects at three
levels: Hypothalamus, locus coeruleus and
spinal cord.
 At the hypothalamic level, it decreases
thermoregulatory threshold for
vasoconstriction and shivering, because
hypothalamus has high density of α2
adrenoceptors and hence is effective in
treating the established post-anaesthetic
shivering.

27.  Also reduces spontaneous firing in locus
coeruleus - a pro-shivering centre in Pons.
 At the spinal cord level, it activates the a2
adrenoreceptors and release of dynorphine,
nor epinephrine and acetylcholine. The
depressor effects of these neurotransmitters
at the dorsal horn modulate cutaneous
thermal inputs.
 Clonidine is highly lipid-soluble and easily
crosses the blood-brain barrier..

28.  Tramadol is an opioid analgesic with opioid
action preferably mediated via μ (mu)
receptor with minimal effect on kappa and
delta binding sites.
 Tramadol also activates the mononergic
receptors of the descending neuraxial
inhibiting pain pathway.
 The anti-shivering action of tramadol is
probably mediated via its opioid or
serotonergic and noradrenergic activity or
both.

29.  Both clonidine (0.5 μg/kg) and tramadol (0.5
mg/kg) effectively treated patients with
post-spinal anaesthesia shivering, but
tramadol took longer time to achieve
complete cessation of shivering than
clonidine.
 So they concluded that clonidine offers
better thermodynamics than tramadol, with
fewer side effects. The more frequent
incidence of side effects of tramadol, like
nausea, vomiting and dizziness, may limit it's
use as an anti-shivering drug.

30.  Prospective randomized data suggest that
high risk patients assigned to only 1.3 degree
Celsius core hypothermia were three times
more likely to experience adverse myocardial
outcomes. Marked increase in plasma
catecholamine level is perhaps associated
with high-risk cardiac complications.
 Zavaherforoush et al. compared clonidine
with pethedine and fentanyl for treating
post-spinal anaesthesia shivering in elective
Lower Segment Caesarean Section (LSCS) and
also found it to be offering better
thermodynamics than pethedine.

31. NORMAL
THERMOREGULATION

32. CENTRAL
AFFERENT CONTROL EFFERENT
INPUT RESPONSES
(Hypothalamus)

33.  Information on temprature is obtained from
thermally sensitive cells throughout the
body.
 Warm receptors their firing rates when
temp. increases, whereas cold receptors do
so when temp. .
 Cutaneous receptors rarely depolarise at
normal skin temp.
 The hypothalamus, other parts of the brain,
spinal cord, deep abd. & thoracic tissues and
the skin surface each contribute roughly 20%
input to the central regulatory system.

34. Cold signals Warm signals
Via A delta FIBRES Via unmyelinated C
fibres
SPINAL
CORD C-fibres also carry
pain sensation,which
is why sometimes
intense heat cannot
MOST OF THE be distinguished from
INF. Via Ant. sharp pain.
Spinothalamic
tract
No single spinal tract is critical for conveying
thermal inf, consequently entire cord must be
destroyed to ablate thermoregulatory responses.

35. The hypothalamus,
other parts of the
brain, spinal cord,
deep abd. &
Preoptic region of the thoracic tissues and
anterior hypothalamus the skin surface
is the each contribute
dominant autonomic roughly 20% input to
thermoregulatory controller in the central
mammals. regulatory system.
Much of the excitatory input to warm
sensitive
neurons comes from hippocampus,
which links the limbic
system (emotion, memory, and
behaviour) to
thermoregulatory responses

36.  Both sweating and vasoconstriction
thresholds are 0.3 – 0.5 degree higher in
women than in men, even during the
follicular phase of the menstrual cycle(first
10 days). These differences are even greater
during the luteal phase.
 Central thermoregulatory control is
apparently intact even somewhat in
premature infants. In contrast this control is
sometimes impaired in elderly.

37. A core temp below the threshold for
response to cold provokes vasoconstriction,
non shivering thermogenesis, and shivering. A
core temp exceeding the hyperthermic
threshold produces active vasodil. and
sweating.
 No thermoregulatory responses are
initiated when the core temp is between
these thresholds which is identified as
interthreshold range, and is about 0.2
degrees centigrade in humans.

38.  In general, energy efficient effectors such
as vasoconstriction are maximised before
metabolically costly responses such as
shivering are initiated.
 Quantitatively, behavioural regulation is
most imp. effector mech which includes
dressing appropriately, modifying
environmental temp, voluntary movements
and acquiring positions that oppose skin
surfaces.

39. 1. Cutaneous vasoconstriction
 Most consistent
 Reduces the heat loss via convection and
radiation from the skin surface
 Total digital skin blood flow
NUTRITIONAL THERMOREGULATORY
(most capillary) (arterio venous shunt)
thus vasoconstriction do not compromise the needs of
peripheral tissue.

40.  Local α-adrenergic sympathetic nerves
mediate constriction in the thermoregulatory
arteriovenous shunts, and flow is minimally
affected by circulating catecholamines.
 Roughly 10% of the cardiac output traverses the
arteriovenous shunts; consequently shunt
vasoconstriction increases mean arterial pressure
approx. 15mmHg.

41. 2. NON SHIVERING THERMOGENESIS:
 INC. metabolic heat production without
increasing mechanical work
 Х2 heat production in infants but increase is
only slight in adults.
 Skeletal muscle and brown fat tissues are the
major sources of non shivering heat in adults
 Controlled primarily by norepinephrine from
adrenergic nerve terminals in these tissues.

42. 3. SUSTAINED SHIVERING:
 Augments metabolic heat production by 50-
100% in adults.
 Shivering does not occur in newborns and
infants
4. SWEATING:
 mediated by post ganglionic, cholinergic
nerves, thus an active process.
 Prevented by nerve block or administration
of atropine.
 Only mechanism by which body can dissipate
heat in an environment exceeding core
temprature.

43. 5. ACTIVE VASODILATATION:
 Apparently mediated by nitric oxide
 Requires intact sweat gland functions,
 So largely inhibited by nerve blockade.

44. THERMOREGULATION
UNDER GENERAL
ANAESTHESIA

45. VASOCONSTRICTION SWEATING
NON SHIVERING
THERMOGENESI VASODILATATION
S
SHIVERING
33 35 39 41
37
THERMOREGULATORY THRESHOLD IN UNANAESTHETISED
PATIENT (normal interthreshold range is near
0.3degrees)

46. VASOCONSTRICTION
NONSHIVERING
THERMOGENESIS SWEATING
SHIVERING VASODILATATION
33 35 41
37 39
THERMOREGULATORY RESPONSE UNDER ANAESTHESIA
(INCREASE FROM ITS NORMAL VALUE TO ABOUT 2-4 DEGREES)

47.  Allgeneral anaesthetics tested so far
markedly impair normal autonomic
thermoregulatory control and cause:
markedly reduced cold response
thresholds, and
slightly elevated warm response
thresholds
and thus increasing the intrethreshold range
about 20 folds to approx. 2-4 degrees C.
 Temp. within this range do not trigger
thermoregulatory defenses, and patients are
thus by definition poikilotheric within this
temp range.

48.  Sweatingis the best preserved major
thermoregulatory defense during
anaesthesia.
 The drugs that are effective for post
anaesthetic tremor and also for shivering
during regional anaesthesia are:
MEPERIDINE(25mg iv), CLONIDINE(75mcg iv),
DEXMEDETOMIDINE, TRAMADOL,
KETANSERINE(10mg iv), MAGNESIUM
SULFATE(30mg/kg iv),
PHYSOSTIGMINE(0.4mg/kg
iv),NEFOPAM(0.15mg/kg).