Transcript CONTROLLED HYPOTENSIVE ANAESTHESIA

CONTROLLED HYPOTENSIVE
ANAESTHESIA
…what is safe ?
Dr Hussain Almejadi
AL RAZI Hospital
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Definition.
History and evolution.
Physiology.
Blood pressure goal.
Contraindications.
Techniques.
Anaesthetic management.
Our experience in Al RAZI hospital.
• why should we be bothered with
hypotensive anaesthesia ?
– Decrease blood loss.
– Improve operative field.
– Decrease duration of surgery.
Decrease in blood loss by 55 % and
shorten the operating time by one
hour .
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Sum DC, Chung PC, Chen WC: Deliberate hypotensive anesthesia with
labetalol in reconstructive surgery for
scoliosis. Acta Anaesthesiol Sin 1996 Dec;34(4):203-207
Significant less blood loss and
improving of the surgical field.
Precious DS, Splinter W, Bosco D: Induced hypotensive anesthesia for
adolescent orthognathic surgery
J Oral Maxillofac Surg 1996 Jun;54(6):680-683
Intraoperative blood loss is 40% less.
Nelson CL, Fontenot HJ: Ten strategies to reduce blood loss in
orthopedic surgery Am J Surg 1995, N°6A (Suppl.), 170:64-68
Deliberate hypotension in orthopedic surgery
reduces blood loss, a meta analysis of RCT.
CANADAIN JOURNAL OF ANESTHESIA 2007
McMaster ,Hamilton,Ontario.
17 ARTICLES.
CONCLUSION : Deliberate hypotension does
reduce blood loss.
Definition
• It is a State of induced hypotension during
anaesthesia to reduce bleeding and
improve the surgical field adjusted to the
patient’s age ,pre-operative blood
pressure and past medical history.
Definition
• Effect VS Safety .
• Reduction in systolic blood pressure to
80 -90 mmHg.
• Decrease in MAP to 50-60 mmHg in
normotensive patients.
• Reduction in MAP by 30% of the baseline
values.
History
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1917
1943
1946
1948
1951
1951
1960
1962
1967
1978
1981
1982
Harvey Cushing for neurosurgery.
Kolhstaedt and Page on dogs arterial bleeding.
Gardner arteriotomy.
High spinal.
High epidural.
Enderby ganlion blockade .
Murtagh halothane.
Moraca sodium nitroprusside.
Dimant pacemaker.
Fahmy nitroglycerin.
Zimpfer verapamil.
Fukunaga adenosine .
Physiology
• Cerebral circulation.
• Coronary circulation.
• Renal circulation.
Cerebral Autoregulation
Cerebral Circulation
• PaCO2 .
• PaO2.
• Temperature.
• Volatile agents.
• Vasodilators.
Coronary Circulation
• Dependent on aortic diastolic blood
pressure.
• Myocardium extracts most of the oxygen
delivered.
• Circulation is autoregulated .
Renal Circulation
• Autoregulation over the range 80-180
mmHg ( Miles and Venton 1954 )
• MAP less than 75 mmHg leads to decrease
in GFR ( Larson et al, 1974 )
• Opioids and inhalational agents stimulate
ADH release (Stunn 1974 )
Respiratory System
• Increase in blood flow to the dependent
areas.
• Vasodilators inhibits hypoxic pulmonary
vasoconstriction.
• PaCO2 and EtCO2 gradient increase.
Blood Pressure Goal
• Reduce blood loss.
• Improve the surgical field .
Contraindications
• Anaethetist factors.
• Patients factors.
Anaesthetist factors
• Lack of understanding of the technique.
• Lack of technical experience.
• Inability to monitor the patient adequately.
Patient factors
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Cardiac disease .
Diabetes .
Anemia.
Hepatic disease.
Ischaemic cerebrovascular disease.
Renal disease.
Respiratory insufficiency.
Severe systemic hypertension.
Intolerance to drugs used for hypotensive
anaesthesia.
Absolute contraindications
• Known drug allergy.
• Inability to monitor the patient adequately.
• Unfamiliarity with the technique.
Morbidity and Mortality
1954 little et al
– mortality 1 in 291
– morbidity 1 in 31.
– Systolic pressure below 80 mmHg.
2008 karol et al Anaesthes and Anlgesia.
– NO DIFFERENCE.
Techniques
MAP = CO x SYSTEMIC VASCULAR
RESISTANCE
Decrease cardiac output
• Reduce blood volume.
• Dilate capacitance vessels.
• Decrease cardiac contractility .
• Decrease of heart rate.
Peripheral vascular resistance
• Blockade of alpha adrenergic receptors.
• Blockade of autonomic ganglion.
• Ralaxation of vascular smooth muscle.
Mechanical manoeuvers
• Positioning .
• Positive airway pressure.
• Spinal anesthesia.
• Epidural anesthesia.
Pharmacologic technique
• Ideal agent
- Ease of administration
- Predictable & dose-dependent effect
- Rapid onset/offset
- Quick elimination without the
production of toxic metabolites
- Minimal effects on blood flow to vital
organs
Inhalational anesthetics
negative inotropic effect
vasodilation
Advantage
Disadvantage
• Provides surgical
• Decreases CO
• Cerebral vasodilation
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anesthesia
Rapid onset/offset
Easy to titrate
Cerebral protection
Sodium nitroprusside
Direct vasodilator (nitric oxide release)
Advantage
• Rapid onset/offset
• East to titrate
• Increases CO
Disadvantage
• Cyanide/thiocyanate
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toxicity
Increased ICP
Increased pulm. shunt
Sympathetic
stimulation
Rebound hypertension
Coronary steal
Nitroglycerin
Direct vasodilator
(nitric oxide release)
Advantage
• Rapid onset/offset
• East to titrate
• Limited increase in
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heart rate
No coronary steal
Disadvantage
• Lack of efficacy•
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depending on
anesthetic technique
Increased ICP
Increased pulm. shunt
Methemoglobinemia
Inhibition of plt.
aggregation
Beta adrenergic antagonist
Beta adrenergic blockade
myocardial contractility)
(decreased
Disadvantage
Advantage
• Rapid onset/offset
• Decreased
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myocardial O2
consumption
No increase in ICP
No increase in pulm.
shunt
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Decreased CO
Heart block
Bronchospasm
Limited efficacy
when used alone
Calcium channel blocker
- vasodilation
Advantage
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Rapid onset
Limited increase in HR
Increase CO
No effect on airway
reactivity
Increased GFR/urine
output
Disadvantage
• Prolonged duration of
action
• Increased ICP
• Increased pulm. shunt
Remifentanil
• Remifentanil is an OPIOID
• Pure m agonist
– little binding at k, s, and d receptors
 Rapid onset/offset
 Decreases blood pressure & heart rate
 No need for additional use of a potent
hypotensive or adjunct agents
Remifentanil Key Concepts
• Remifentanil is an ESTER
. Metabolized by nonspecific esterases in blood
and tissue
• Anesthesia maintained with high-dose
remifentanil will be associated with rapid
recovery.
 Within 5-10 minutes of turning off an infusion there is
virtually no residual remifentanil drug effect
Dosing and Administration
• Dex. should be administered using a controlled
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infusion device.
Dex. dosing should be individualized and titrated
to the desired clinical effect
For adult patients Dex. is generally initiated with
a infusion of 1mcg/kg over 10 minutes, followed
by a maintenance infusion of 0.2 to 0.7
mcg/kg/hr
It is not necessary to discontinue Dex. prior to
extubation
• Comparison between dexmedetomidine and remifentanil
for controlled hypotension during tympanoplasty.
• CONCLUSIONS: Infusion of dexmedetomidine, at the
doses used in this study, was less effective than
remifentanil in achieving controlled hypotension, good
surgical field exposure condition and surgeons'
satisfaction during tympanoplasty.
2008-05, Eur J Anaesthesiol., 25(5):369-74. Epub 2008 Feb 25.
Preoperative management
• Thorough knowledge by the anaesthetist.
• Proper patient evaluation and selection.
• HB of 10 g/dl.
• Arterial blood gas analysis sampling.
• Good level of anxiolytics ,analgesics .
• Vagolytic drugs should be avoided.
Intraoperative management
• Stress free induction.
• Nasal intubation ?.
• Enough peripheral venous access.
• Pressure points.
Monitoring
• Invasive blood pressure .
• Invasive blood pressure.
• ECG V5 lead with ST segment analysis.
• Central venous pressure.
• Urine output.
• Temperature.
• Blood loss.
Fluid therapy
• Deficit replacement.
• Maintenance.
• Blood loss.
• Induced hypotension should start at the
time of mucosal incision .
• Only to the level needed to reduce
bleeding.
• Only during specific surgical phase.
Postoperative management
• Rebound hypertension.
• Reactionary hemorrhage.
Our experience in AL RAZI hospital
• Strong points.
• Area of improvement.
Strong points
• One OT is allocated for hypotensive
anaesthesia/TIVA.
• Propofol – remifentenyl.
• Invasive monitoring is a must.
Area of improvement
• Patients selection.
• Reduction in blood transfusion.
Future studies
• Prospective.
• Control of age and physical status.
• Bigger sample size.
• Type of surgery.
• Controlled studies.
• Same technique.
• Doppler technique.
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