Nursing Management of Head Injury and Intracranial Pressure

To calculate CPP, the nurse must first determine the Mean Arterial Pressure (MAP). The formula for MAP is:

$$MAP = \frac{SBP + (2 \times DBP)}{3}$$

Once the MAP is known, CPP is calculated by subtracting the ICP from the MAP:

$$CPP = MAP - ICP$$

The normal range for CPP is 60 to 100 mmHg. If the ICP rises too high or the MAP drops too low, the CPP will fall, leading to inadequate cerebral perfusion and potential brain death.

Measurement of ICP

ICP monitoring is indicated for patients with a Glasgow Coma Scale (GCS) score of 8 or less, or those with abnormal CT/MRI findings. There are several technologies used to measure this pressure:

Ventriculostomy

The ventriculostomy is a gold-standard method where a catheter is inserted directly into the lateral ventricle. This method is unique because it allows for both the measurement of pressure and the management of it; the nurse can control ICP by intermittently or continuously draining CSF.

Other Monitoring Technologies

• Fiberoptic Catheter: These utilize a sensor transducer located at the very tip of the catheter, which is placed within the ventricle.
• Pneumatic Technology: This involves an air-filled pouch at the catheter tip that senses pressure changes within the cranium.

Assessing ICP Waveforms and Accuracy

ICP should be measured as a mean pressure, but the nurse must also observe the ICP waveform. Changes in the waveform can indicate shifts in intracranial dynamics.

It is critical to recognize when an ICP reading might be inaccurate. Inaccurate readings can be caused by:

• CSF leaks
• Obstructions or kinks in the catheter tubing
• Air bubbles in the tubing
• Incorrect positioning (differences in height between the catheter and the transducer)

Nursing Management and Priorities

Nursing care for a patient with a head injury is centered around preventing secondary injury and maintaining physiological stability.

Nursing Diagnoses

The primary nursing diagnoses for these patients include:

1. Decreased intracranial adaptive capacity
2. Ineffective tissue perfusion
3. Hyperthermia
4. Risk for injury

Acute Care Interventions

• Positioning: Maintain the Head of Bed (HOB) at 30 degrees. Avoid neck or hip flexion, as this can impede venous return and increase ICP.
• Respiratory Support: Maintain a patent airway. For patients with a GCS < 8, intubation is required. Monitor ABGs to ensure $PaO_2 \geq 100$ mmHg and $PaCO_2$ is between 35–45 mmHg.
• Neurological Assessment: Perform frequent assessments of LOC, pupil reaction, and motor function (e.g., checking for palmar drift or posturing).
• Temperature Control: Maintain normothermia, as fever can increase metabolic demand and ICP.
• CSF Leak Precautions: If a leak is suspected, use loose collection pads under the nose or over the ears. Do not use NG tubes or perform nasal suctioning, as this can increase intracranial pressure.

Exam Tip: Recognizing Emergency Signs A fixed, unilateral, dilated pupil (compression of Cranial Nerve III) is considered a neurological emergency and may indicate imminent herniation.

Interprofessional Care

Pharmacological management often includes Mannitol (Osmitrol) to create an osmotic effect that pulls fluid from the brain into the blood, or hypertonic saline to move water from cells into the vascular space. Nurses must closely monitor fluid and electrolyte balance, as these patients are at high risk for Diabetes Insipidus (DI) or SIADH.