HYPERTENSION

 Drug errors (1)
 Awareness or light anaesthesia (2)
 Pre-existing hypertension (3)
 Airway problems (4)
 Surgical factors (5)
 Hypercarbia (6)
 Uncommon/unusual conditions
     Fluid overload
     Raised intracranial pressure
     Hyperthyroidism
     Phaeochromocytoma/carcinoid
     Malignant hyperthermia  
 

Complete COVER ABCD - A SWIFT CHECK   (7)
Confirm the blood pressure change is real (8)
Deepen anaesthesia/assess depth
Cease any vasopressor therapy (9)
Inform the surgeon; cease stimulation
Recheck for drug errors and delivery of anaesthesia
Consider an appropriate dose of opioid (10)
Consider antihypertensive therapy:
BE CAUTIOUS USING HYPOTENSIVE AGENTS IF THE POSSIBILITY OF LIGHT ANAESTHESIA EXISTS
Consider glyceryl trinitrate 50 mg in 500 ml 5% Dextrose and start at 5ml/hr for adults (0.1 ml/kg/hour for children).
If tachycardia is troublesome:
Give atenolol 0.015 mg/kg IV bolus injections (11)
Titrate drugs against effect

FURTHER CARE
          Review and treat probable cause(s)
          See precipitating factors and (1) to (9) below
          Consider invasive blood pressure monitoring
          There is a risk of awareness

NOTES:
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It was judged that correct use of COVER ABCD followed by the hypertension sub-algorithm would have identified the specific cause in 79% of 70 relevant incidents reported to AIMS. In 21% no obvious cause was apparent, but was assumed to be a combination of light anaesthesia and/or excessive surgical stimulation and in all cases was effectively treated by rapidly deepening anaesthesia.
(1) Drug errors, secondary to drugs being given - 4o%, or following drugs unintentionally not being given - 14%.
(2) Presumed light anaesthesia - 21% of reports, due to inter-individual variation, failure to deliver agents: vaporiser, nitrous oxide, syringe driver failure.
(3) Preoperative hypertension - 61% of the 252 reports received by AIMS
(4) Causes included hypoventilation, hypercarbia and hypoxia
(5) Surgical stimulus, water intoxication, aortic cross clamping.
(6) Hypercarbia in 11%. Due to hypoventilation, soda lime exhaustion, sticking valve in circle system, inadequate fresh gas flows in non rebreathing circuits.
(7) Use of the 'COVER ABCD - A' algorithm identified 73% of incidents reported to AIMS.
(8) Use a sphygmomanometer and auscultate the blood pressure.
When using an arterial line, check the zero and calibration. In 4% of cases the hypertension was spurious.
(9) Inadvertent vasopressor administration was the commonest reported cause - 40%.
(10) After reviewing the drugs administered to date, give opioids if judged appropriate,
       eg  fentanyl 0.25 - 0.5 micrograms/kg aliquots, titrated to effect.
(11) Esmolol, a β blocker with rapid onset and short duration of action, in a dose of 0.25 - 0.5 mg/kg may be a better
       choice if available.