Increased Intracranial pressure and nursing care.

Intracranial pressure (ICP)

Increased Intracranial pressure (ICP) can have dire consequences if the patient is not managed carefully. Sadly it can be often seen in both first opinion and referral settings and even with excellent interventions can still have a poor outcome.

What is Intracranial pressure?

 Brain tissue, cerebrospinal fluid (CSF) and blood are the three components within the cranial cavity surrounded by the rigid bony skull. Intracranial pressure (ICP) is the pressure inside the skull, which is influenced by the equilibrium between these components (Platt and Olby, 2013). In the healthy patient, compensatory mechanisms maintain a constant ICP, meaning that an increase in volume of any of the three intracranial compartments will result in an equivalent decrease in the other two. These compensatory mechanisms may fail and vary in presence of different intracranial diseases (for example tumour, head trauma, inflammation).

How does it increase?

In a patient with acute head trauma, the compensatory changes may not happen fast enough to cope with the increase in CNS volume due to oedema, haemorrhage or CSF accumulation, therefore an increase in ICP is more likely. The ability to compensate is instead more effective if the increase in volume occurs slowly, like in presence of brain tumours. In these cases, the compensatory mechanisms may be able to prevent a rise in ICP initially, but will eventually fail and progressive increase in intracranial volume will dramatically increase ICP (Platt and Olby, 2013). High ICP may be life threatening therefore, any patient with intracranial disease should be recognised promptly and managed appropriately to prevent any further increase in ICP.

ICP is measured in millimetres of mercury(mmHg). Normal ICP is between 5-12mmHg (Platt and Olby, 2013).

Clinical and neurological signs of increased ICP:

 Evaluation of the mental status, ability to move, pupil size and responsiveness, position and movement of the eyes and breathing pattern is critical in the identification of patients with increased ICP. Lack of coordination, loss of balance, inability to walk, seizures, anisocoria are all clinical signs that can be present in these patients.

Establishing a patient’s demeanor and level of consciousness is an essential part of the neurological examination that provides information regarding brain function, the level of injury and signs of raised ICP (Platt, 2015). Mental status can be described as normal, depressed, obtunded, stuporous, or comatose. Pupil size, shape and reactivity are an important aspect of the patient’s physical examination and should be assessed at frequent intervals to be able to monitor any deterioration or improvement if the patient has started treatment. Pupillary abnormalities can be unilateral or bilateral (Platt, 2015). The pupillary light reflex provides important information with regards to the possible level of cerebral injury and the patients prognosis (Platt, 2015).

Aniscoria ICP

Often referred to as the Cushing reflex, this consists of an increase in systolic blood pressure, bradycardia and irregular respiration. If a patient is displaying both bradycardia and hypertension, this is a warning sign of raised ICP and immediate care is essential to prevent further cerebral damage and neurological deterioration.

Modified Glasgow coma scale (MGCS):

This is a useful tool in veterinary medicine when treating patients with or at risk of raised ICP. It consists of a scoring system to grade the neurological status of the patient and is divided into 3 sections; motor activity, brainstem reflexes and level of consciousness. Each section is scored from 1 – 6, 1 being the most severe and 6 being the mildest clinical sign. The total score can then help estimate the severity of the patient’s condition, which in turn determines the prognosis (e.g. MGSC < 14 associated with guarded prognosis; MGCS < 8 associated with grave prognosis) and the requirement of specific treatment (Platt, 2015).

Fluid therapy:

Fluid therapy is a very important management tool for patients with raised ICP.

Crystalloids: patients suffering from head trauma or those with intracranial tumours require a normovolaemic state to ensure adequate cerebral perfusion pressure.

Hypertonic salineremoves fluid from the interstitial and intracellular spaces into the intravascular space and therefore decreases ICP. This in turn restores the blood volume improving systemic blood pressure, cerebral blood pressure and flow.

Mannitol: is an osmotic diuretic, it has an immediate plasma expanding effect which reduces blood viscosity, leading to improved oxygen delivery, stimulating cerebral vasoconstriction and causing a decrease in ICP. It is administered as a bolus over 15-20 minutes in order to obtain the plasma expanding effect. It lasts between 2-8 hours.

The author prefers to use a giving set with a filter due to the crystals that can form.

If an increase in ICP is suspected, after adequate patient stabilisation, it is preferable to administer mannitol or hypertonic saline before the patient undergoes further investigations (e.g. MRI/CT). The fluid dehydrates the brain cells therefore reducing oedema. Both hypertonic saline and mannitol, require concurrent administration of crystalloids solution to prevent dehydration.

Nursing Care of a patient with increased ICP:

There are a number of simple precautions that can be taken when nursing patients with raised ICP:

Pressure around the neck can cause obstruction of the jugular veins and therefore contribute to increased ICP. Jugular venepuncture and neck leads should be avoided; blood sampling from peripheral veins or harnesses for walks should be used as an alternative.

In the recumbent patient, the head should be elevated at a 30-degree angle (Platt and Olby, 2013); head down positioning increases cerebral venous blood volume and as a result increased ICP.

The respiratory system can be affected following traumatic injuries not only due to thoracic compromise but also to cerebral impairment. Oxygen supplementation should therefore be considered in all patients with acute brain injury (Platt and Olby, 2015). This can be provided via flow by or via nasal prongs, the method of oxygen delivery should provide minimal stress to the patient which can further increase ICP (Platt and Olby, 2013). Respiratory parameters include respiration rate and effort, mucous membrane colour and thoracic auscultation. Pulse oximetry can also help determine the patient’s oxygenation status.

Monitoring HR and RR

Regular heart rate and blood pressure checks are recommended for patients at risk of raised ICP in order to help prevent clinical deterioration as early as possible.

Coughing can increase ICP. So it is important to prevent this during both intubation and extubation for those patients undergoing anaesthesia. Minimising laryngeal stimulation during intubation can be achieved by ensuring the patient has reached an adequate level of anaesthesia during the induction process before attempting to intubate.

Bladder management is an important aspect to consider. These patients will often pass a large volume of urine during administration of the fluids discussed, so it is important to ensure they are comfortable. Walk patients that are able to ambulate and perform manual bladder expression and regular bed checks for those who are recumbent.

Conclusion:

Nursing a patient with, or at risk of raised ICP can be challenging but also very rewarding especially if they make a full recovery. There are many nursing considerations to be taken into account. All of which contribute in some way to a patient’s recovery, highlighting the importance of a veterinary nurse.

  

References:

  • Platt, S and Olby, N., 2013. Neurological emergencies In: Platt and N.Olby, eds. 2013. BSAVA manual of canine and feline neurology, 4thedition. Gloucester: BSAVA. Ch.20.
  • Platt, S and Garosi, L., 2012. Small animal neurological emergencies Manson.
  • Platt, S., 2015. Coma scales In: D.C.Silverstein and K.Hopper, 2015. Small animal critical care medicine, 2nd Elsevier. Ch.81.

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