Effective Management of Anaesthetic Crises

Aetiology of Perioperative Hypertension

* Sympathetic response
* Pre-existing hypertension
* Hypoxaemia/hypercarbia
* Drug effects
* Cerebral ischaemia
* Preload (Volume overload)
* Afterload

Sympathetic response

* “Light” anaesthesia
* Painful stimulus
* Emergence
* Bladder distention
* Tourniquet

Pre-existing hypertension

* Essential hypertension
* Renovascular
* Pre-eclampsia
* Autonomic dysreflexia
* Other endocrine-e.g. phaeo, hyperthyroid
* Drugs

Drug Effects

* Vasopressors
* Withdrawl E.g.
Clonidine
Beta blockers.
Methyldopa.
* Interactions-e.g.MAOIs.
With pethidine
Metaraminol
Ephedrine
Cocaine

Cerebral Ischaemia

* Raised ICP
* Carotid/Vertebral occlusion, e.g. from neck positioning

High Afterload

* Aortic crossclamp
* Pneumoperitoneum
* Hypothermia

Exclude Artefact

* NIBP
* Repeat measurement
Check system, verify correct cuff & application
Measure manually
* Intra-arterial
Check transducer position and zeroing
>Check system. Flush line
Confirm with NIBP (manual or automatic)

Assess Severity

* Mean BP >120mmhg or > 30% above baseline
* ST depression present
* Patient Factors
E.g. known ischaemic heart disease
Cerebrovascular disease
o Aneurysm
o Associated bleeding
* Any of above = severe
* Urgent treatment required.

Assess Aetiology

* Assess anaesthetic depth
* Check anaesthetic delivery
* Check vasoactive drug administration
* Check ventilation and oxygenation
* Consider surgical factors

Anaesthetic Depth

* Is the depth appropriate for the level of stimulus?
* Check:
Respiratory effort/rate & patient movement.
Tachycardia.
Sweating & tearing.
>Eye signs.
BIS may be useful if available.

Anaesthetic Delivery

* Inhalational agents:
Confirm end tidal anaesthetic level
Check fresh gas flow
Check vaporiser:
o Correct setting
o Correct seating, locked & leak free
o Adequately filled
* Intravenous anaesthesia
Visually check infusion of anaesthetic and carrier fluid, including I.V. site
Check infusion rate and proper running of infusion
Recheck dosage/concentration calculations
Consider converting to or adding volatile agents (whose end tidal concentration can be confirmed)
B.I.S. may be useful if available

Drug administration

* Vasoactive agents:
Check infusion rate and dosage calculations
Confirm that the correct drug is being used
* Are there other drugs being used?
E.g. adrenaline containing local anaesthetic
Desflurane

Ventilation and Oxygenation

* SpO2 and EtCO2.
* Clinically assess ventilation and airway
* ABG’s if problems suspected

Surgical Factors

* Anticipate high levels of surgical stimulation and increase depth accordingly
* Remember other factors such as:
Tourniquet, pneumoperitoneum, cross clamp

Treatment for isolated Hypertension

* Vasodilators
* Alpha-blockers
* Beta blockers
Especially if associated with tachycardia
Beware contraindications

Dilators

* Hydralazine:
5-10 mg I.V. repeat every 20’
* GTN:
15mg in 25 mls = 600 mcg/ml
Start @ 20 mcg/min (2ml/hr) & titrate
Or 0.5-20 mcg/kg/min
* Na Nitroprusside
Start @ 20 mcg/min & titrate
Or 0.5-8.0 mcg/kg/min

Alpha-blockers

* Clonidine:
150mcg I.V. in divided doses
* Phentolamine:
0.5-1mg increments

Beta Blockers

* Atenolol
1-2mg I.V. up to 10 mg
* Esmolol
5-10 mg increments
Or Infusion- 50-300 mcg/kg/min
* Indicated with associated tachycardia, evidence of cardiac ischaemia, or known C.A.D
* Consider contraindications:
Significant broncospasm
Suspected phaeochromocytoma

Raised I.C.P.

* Mannitol
0.5-2 g/kg I.V.
* Moderate hyperventilation
Down to arterial pCO2 30mmHg
* Frusemide
5-10 mg I.V.
* The aim is to preserve cerebral perfusion pressure
* Followed by urgent neurosurgical intervention