Bradycardia in neurosurgery.

Cushing reflex' is characterized by the occurrence of hypertension, bradycardia and apnoea secondary to raised increased intracranial pressure (ICP), leading to pressure on and or stretch, or both, of the brainstem. With the wide availability of monitoring facilities and advancements in investigation techniques, observation of increased intracranial pressure resulting in haemodynamic instability and bradycardia has been increasingly recognized in relation to many neurosurgical conditions and procedures. The causes of bradycardia include space occupying lesion involving or compressing the brain parenchyma (subdural haematoma, tumours, hydrocephalus), neurosurgical procedures (neuroendoscopy, placement of extradural drains), epileptic and non-epileptic seizures, trigemino-cardiac reflex, cerebellar lesions, spinal lesions (neurogenic shock, autonomic dysreflexia) and many other rare causes (Ventricular catheter obstruction in cases of hydrocephalus, colloid cysts related acute neurogenic cardiac dysfunction, Ondine's curse syndrome, etc.). This highlights that bradycardia can be a warning sign in many neurosurgical conditions and Cushing's reflex is a protective and effective action of the brain for preserving an adequate cerebral perfusion pressure despite an increased intracranial pressure. Management of these patients include identification and treatment of the underlying cause of bradycardia, anti-cholinergics and if necessary cardiac pacing, nevertheless, other causes of haemodynamic changes (i.e. anesthetic drugs, tumor manipulation) should also be considered and managed accordingly. We believe that this knowledge and understanding will help to identify the patients' at risk and will also help in the management of neurosurgical patients with bradycardia.