EMS Neurological Emergencies - The Monro-Kellie Doctrine

The Monro-Kellie Doctrine is a fundamental concept in neurology and emergency medicine that EMS providers should be familiar with.

Essentially, it states that the skull is a rigid container that houses the brain, blood, and cerebrospinal fluid (CSF), and that the total volume inside the skull must remain relatively constant to maintain normal intracranial pressure (ICP).

Here are some key points that EMS providers should know about the Monro-Kellie Doctrine:

Components of Intracranial Contents: The doctrine describes the three main components inside the skull - brain tissue, blood, and cerebrospinal fluid.

Any increase in the volume of one of these components must be compensated by a decrease in the volume of another to maintain a relatively constant intracranial pressure.

Implications for Traumatic Brain Injury (TBI): In cases of TBI, such as intracranial hemorrhage or cerebral edema (swelling of the brain tissue), the Monro-Kellie Doctrine helps EMS providers understand the potential consequences.

An increase in the volume of blood or swelling of the brain tissue can lead to increased intracranial pressure, which can compromise cerebral perfusion and cause further damage.

Clinical Assessment: EMS providers should be vigilant for signs and symptoms of increased intracranial pressure in patients with head injuries, such as altered level of consciousness, headache, vomiting, pupillary changes, and changes in vital signs.

These indicators may prompt the need for urgent intervention and transport to a higher level of care.

Treatment Implications: Understanding the Monro-Kellie Doctrine guides treatment strategies for patients with traumatic brain injury.

Interventions aimed at reducing intracranial pressure may include elevating the head of the bed, administering hyperosmolar therapy (such as mannitol or hypertonic saline) to reduce cerebral edema, ensuring adequate oxygenation and ventilation, and potentially performing interventions to control bleeding or relieve pressure, such as craniotomy or burr hole evacuation.

Importance of Monitoring: Continuously monitoring vital signs, neurologic status, and intracranial pressure in patients with head injuries is crucial for early detection of deteriorating conditions and timely intervention.

EMS providers should be trained in the use of appropriate monitoring devices and interpretation of data.

Overall, a solid understanding of the Monro-Kellie Doctrine is essential for EMS providers caring for patients with traumatic brain injury or other intracranial pathology.

It helps guide clinical assessment, treatment decisions, and ongoing management to optimize outcomes for these patients.

Further Reading:

Cowburn, R. & Cadogan, M (2020) Monro-Kellie Doctrine. Life in the Fast Lane https://litfl.com/monro-kellie-doctrine/ Accessed April 14, 2024

Mokri B (2001) The Monro-Kellie Hypothesis: Applications in CSF Volume Depletion. Neurology 56 (12): 1746-8

EMS Medical Terminology - Cushing's Triad

Cushing's Triad is named after Dr. Harvey Cushing, an American neurosurgeon who made significant contributions to the field of neurosurgery. This is an example of eponymous medical terminology.

Dr. Cushing described a set of clinical signs and symptoms associated with increased intracranial pressure in his work "Intracranial Tumours: Notes upon a Series of Two Thousand Verified Cases with Surgical Mortality Percentages Pertaining Thereto." 

This work was published in 1901, and it was one of the earliest descriptions of the physiological changes associated with intracranial pressure.

Recognizing Cushing's Triad is crucial for EMS Providers, as it is suggestive of a potentially life-threatening situation due to various adverse conditions, including head injuries and brain pathologies. 

As such, the need for urgent medical intervention is paramount.

Cushing's Triad consists of the following three key signs:

Hypertension (High Blood Pressure):

A significant increase in systolic blood pressure is a common feature of Cushing's Triad. This is a response to the body's attempt to maintain cerebral perfusion (blood flow to the brain) in the face of elevated intracranial pressure.

Bradycardia (Slow Heart Rate):

Cushing's Triad often includes a slow heart rate (bradycardia), particularly as a result of increased ICP. This is a compensatory mechanism intended to decrease the heart's pumping strength, reducing blood flow to the brain and thereby minimizing the risk of further brain damage.

Irregular or Abnormal Respiratory Patterns:

The third component of Cushing's Triad is abnormal breathing patterns, typically characterized by irregular or irregularly deep respirations. This is often referred to as "agonal" or "Cheyne-Stokes" breathing.

These respiratory changes are a response to the brain's attempt to restore oxygen levels and eliminate excess carbon dioxide, which can occur due to impaired blood flow or brainstem compression.

Recognizing Cushing's Triad in a patient is a critical finding for EMS providers, as it may indicate an impending brain herniation, which is a life-threatening condition. 

Patients displaying Cushing's Triad should be managed promptly and transported to a specialized facility for further evaluation and potential surgical intervention.

Here are some key points for EMS Providers:

- Perform a detailed neurological assessment, including monitoring vital signs, level of consciousness, and pupillary response.

- Administer supplemental oxygen to ensure adequate oxygenation.

- Maintain cervical spine immobilization to prevent further spinal cord injury, if applicable.

- Communicate with the receiving medical facility to ensure they are prepared for the patient's arrival and can provide neurosurgical expertise if necessary.

- Avoid hyperventilation, as it may worsen cerebral ischemia.

- Cushing's Triad is a critical clinical finding that requires immediate attention and transport to a higher level of care. 

- EMS providers should follow their local protocols and seek medical direction when managing patients with Cushing's Triad.

Further Reading:

Alexander, M. & Belle, R. (2017) Advanced EMT: A Clinical Reasoning Approach (2nd Ed). Hoboken, New Jersey: Pearson Education

Bledsoe, B. E., Cherry, R. A. & Porter, R. S (2023) Paramedic Care: Principles and Practice (6th Ed) Boston, Massachusetts: Pearson

Ebright, C. (2024) Unique Patient Signs: A Case Study. EMS1. https://www.ems1.com/patient-assessment/articles/unique-patient-signs-a-case-study-f4CQBuoUo9uTCHrZ/ Accessed May 1, 2024

Mistovich, J. J. & Karren, K. J. (2014) Prehospital Emergency Care (11th Ed). Hoboken, New Jersey: Pearson Education

Peate, I. & Sawyer, S (2024) Fundamentals of Applied Pathophysiology for Paramedics. Hoboken, New Jersey:  Wiley Blackwell