HYPOVENTILATION

Desaturation
Rising ETCO2
Change in heart rate
 

Coughing/breath holding/light anaesthesia (1)
Airway obstruction
Distended abdomen
Lithotomy, Trendelenberg position
CNS depression (2)
Loss of integrity of chest wall or diaphragm
Muscle weakness
Pre-existing conditions (3)
Drugs
     Relaxants (4)
     "High spinal" blockade
Equipment related problems (5)
 

Complete COVER ABCD A SWIFT CHECK

The primary cause may be obvious if so, treat it
If laryngospasm - see Laryngospasm
If airway obstruction - see Airway Obstruction
If inadequate depth of anaesthesia is causing coughing, bucking or breath holding; rapidly deepen anaesthesia with an IV agent (1)
Consider other precipitating factors listed above.

The guidance here is based on an analysis of  the first 4000 AIMS anaesthesia incidents.
(1) This was a common cause of desaturation, secondary to hypoventilation. Rapid control of the situation may be gained by deepening anaesthesia with 10-20% of the initial induction dose.
(2) All anaesthetic induction and maintenance drugs, opioids and sedatives, depress ventilation in the spontaneously breathing patient.
(3) Numerous conditions cause muscle weakness. Broadly speaking they consist of:
         Primary muscle conditions (myopathies)
         Secondary muscle weakness (electrolyte disturbances/drugs etc.)
         Conditions affecting innervation (trauma/neuropathy/CVA, myasthenia gravis etc)
(4) Several drug related causes of hypoventilation were reported to AIMS, including:
         Relaxant anaesthesia without commencing IPPV
         Residual or recurrent paralysis in the recovery phase
         Paralysis/weakness associated with high spinal blockade
(5) Any problem resulting in a lack of circuit continuity
         Disconnections
         Misconnections
         Leaks
         Obstructions

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