16. Stroke for first responders – August 2015
Stroke is the second leading cause of death or disability in Australia. The Australian Bureau of statistics report 60,000 strokes occur each year with one quarter in Victoria. As many as one third of these people die within twelve months with the annual cost to the country over two billion dollars. Any management that can reduce incidence of stroke or improve outcomes once occurred has huge benefit potential.
The brain is the key part of the central nervous system and is responsible for all conscious thought and actions and many subconscious body functions.
The major part of the brain, the cerebrum, is responsible for higher functions including consciousness and awareness. It includes the major senses of sight, smell, taste and hearing though these are only small parts of the cerebrum. The ability to think and speak is governed by the cerebrum. Most importantly this part of the brain includes a large part given to controlling motor function. Due to an interesting anatomical design where nerves change sides within the neck, the right side of the brain controls the left side of the body and vice versa.
At the base of the brain twelve cranial nerves arise that control activities of the muscles in the face, tongue and eyes (including the optic nerve). At the lower back of the brain is the cerebellum. This is responsible for balance, coordination and steadiness of walking. At the very base of the back of the brain is the brainstem. This is where the brain ends and the spinal cord begins. It is the part of the brain responsible for the most basic body functions, the life support system if you like. It controls the heart rate, blood pressure and respiration. It also controls the vomiting centre.
All of these components of the brain are contained within the protective confines of the skull. However if there is any problem with the skull, such as from trauma, or a problem within the brain itself, such as stroke, then a variety of patient presentations may result depending on the part of the brain affected. These presentations can provide important clues to the problem.
What is stroke? The definition of stroke is comparatively simple. A stroke occurs when the blood flow to a part of the brain is acutely disrupted. There are several types of stroke and they can be differentiated by the cause of the disruption. Stroke used to be known as cerebrovascular accident.
Essentially stroke is caused by interruption of blood flow through one or more blood vessels that supply the brain. These interruptions include either a sudden blockage or a rupture of the blood vessel. The blockage form of stroke is known as ischemic stroke meaning that there is limited or no blood flow past the blockage.
The rupture form of stroke is known as haemorrhagic. It involves bleeding into the brain and has two major problems. Firstly it also interferes with blood getting past the rupture to the rest of the brain. The second problem though is that the bleeding creates a pool of blood trapped inside the skull that puts pressure or ‘squeezes’ other parts of the brain. This can cause parts of the brain to become affected.
Ischemic stroke ‘blockage’: As many as four out of five strokes that occur are ischemic making this by far the most common cause. There are essentially two ways for an ischemic stroke to occur. One way is for a blood clot that forms somewhere else in the body to break off and be carried in the blood until it lodges in one of the blood vessels in the brain. Blood clots that lodge this way are called embolisms and often follow disturbances in the normal heart rhythm.
The second and more common is a progressive narrowing of a blood vessel in the brain. This is similar to the blockages that form in the arteries of the heart that cause angina and heart attack. The usual cause of this is cholesterol and fat deposits sticking to and damaging the inner artery walls. This damage causes blood clots at the site trying to heal the injury. These clots can cause acute blockages. This gets worse over time until eventually blockage is complete.
High blood pressure and high blood sugar are both factors that increase the likelihood of this occurring making them risk factors for stroke. This is called a thrombus stroke. The part of the brain past the blockage supplied by the blood vessel will be affected.
Haemorrhagic stroke: One in five strokes are caused by a haemorrhage within the brain. This occurs when a weakness in the wall of a blood vessel ruptures causing bleeding. This also causes disruption of blood supply past the site of bleeding.
There is also the added problem of the blood clot that develops. This may form inside the brain itself (intra-cerebral) or it may form on the outside of the brain (sub-dural and sub-arrachnoid). In either case the bleeding is trapped inside the skull. This can literally squeeze the brain and put more pressure on the other parts of the brain making the problem worse. In this case the part of the brain supplied by the ruptured blood vessel will be affected but so too will other parts of the brain that are put under pressure by the ‘squeezing’.
Transient ischemic attack (TIA): The TIA, or mini stroke as many patients refer to it, is a thrombus stroke that is not fully developed. As the blood vessel gets narrower and closer to blocking completely signs and symptoms begin to show. These can appear when there is greater need for blood such as during stress or exercise. As the patient relaxes or perhaps even collapses the demand for blood will naturally decrease. The signs and symptoms will then resolve completely. This is just like angina of the brain.
This presentation should resolve quickly, typically within a few minutes. If it persists for more than an hour or so or if the signs and symptoms have not resolved by the time emergency response arrives the patient should be assumed to be having a stroke and not a TIA. This includes if the signs and symptoms have even partially resolved.
It is essential that even if there is complete resolution of all presenting problems that the patient is transported to hospital. Each TIA should be considered as a ‘warning event’ as there is a likelihood of subsequent stroke within a few days for these patients.
Recognising stroke: The presentation of any stroke varies depending on the part of the brain affected by interruption of blood supply. Without intervention damage to the affected part of the brain will become permanent as cells not receiving blood begin to die. For brain cells this will not take very long at all and minutes will be important.
Recall that most strokes are thrombotic. They also occur mostly in the cerebrum since that is by far the largest part of the brain. As such the typical stroke presentation will involve some impact on some of those functions within the cerebrum. The classic stroke presentation and one commonly seen has a predictable combination of:
- Loss of facial muscle control F and/or
- Loss of motor function of limbs on one side of the body including an arm A
- Difficulty with speech S
Facial muscle control loss usually means the face appears to droop on one side. This can be best observed by standing in front of the patient and comparing both sides. A friend or relative nearby can be asked for an opinion. Motor function can be assessed in the same way that GCS is normally assessed. The patient can be asked to reach up with both hands to grasp the outstretched assessor’s fingers. Where the patient is unable to do this the motor function can be assessed for ability to localize or even to withdraw from pain if necessary. It must be kept in mind that this must be compared equally for both sides of the body.
Speech is assessed by asking a standard question such as the patient’s name, what day it is or what the current location is. The patient’s speech may be normal, or slow and slurred or there may be none at all. Even where stroke patients may not be able to speak, if they are awake they may be able to fully understand you and answer with head nodding or other means. They may also be very puzzled and concerned so reassurance is important. This goes for the family as well.
Where elements of this classic triad are observed, particularly all three, the potential for stroke is significant and should be acted upon. Because brain cells do not endure ischemia well for more than short periods, action must be prompt.
If in doubt and stroke is a possibility – assume the patient is having a stroke until proven otherwise. The time to act is immediate – T.
These letters are classically applied as FAST for stroke assessment and action. That is, if there is abnormal facial expression or tone and/or there is altered or loss of arm function on one side and/or the patient has difficulty speaking. These signs of stroke can be detected during assessment by looking for particular actions or observations
Not all strokes appear classically like this. Some patients may complain of headache. Most ischemic strokes will not have any headache. Haemorrhage though may produce severe headache. All patients with severe headache should be considered as possibly having a haemorrhage inside their brain. If the cerebellum is involved there may be loss of balance or difficulty walking
The minority of strokes involve haemorrhage. These types cause problems within the brain as do other stroke types. They bring that added complication: the brain squeezing from bleeding trapped within the protective skull
When the brain is ‘squeezed’ like this, known as increased intracranial pressure, it pushes down on the brain beneath. The result of this depends on where the pressure is. It may include loss of motor function or it may include change of consciousness. It may cause seizures. If the cranial nerves are squeezed it may cause changes in the patient’s vision. It may also cause changes in pupils. The optic nerve passes messages of light from the eye to the brain. If it is squeezed stopping messages moving along the nerve, the brain assumes there is no light being seen. No message can be sent back on the optic nerve so the pupil fully dilates to its resting state.
Importantly if the brain stem is squeezed there may be changes in the basic vital sign observations. This can include rising blood pressure and slowing of pulse rate. It may include changes in normal respiration or repeated vomiting. All of these are controlled in the brain stem
Time of onset: The time a stroke occurs is very important. Brain cells do not survive very long when they are ischemic or when they are being ‘squeezed’ in haemorrhage. If any treatment is possible, then the time the problem started is important to know.
If possible, determine from the family or witnesses when the problem started. If this cannot be determined, such as if a patient has awoken from sleep or has been found by others already like this, the onset time is the last time the patient was known to be well. If the last time the patient was seen well was when they went to bed or one hour before they were found, for example, then that is what must be documented as the time of onset for the problem. Patients who are within around four to five hours from onset may be able to be treated in a stroke centre.
Stroke mimics: It is important to consider stroke might be the cause as this is the most serious possibility. Minutes are critical to outcome. However not all causes of abnormal brain function are stroke. Where possible, stroke mimics must be ruled out first. There are a number of stroke mimics that can be considered. For the first responder it is important only to consider the most obvious and basic of these.
The first mimic is hypoglycaemia. Patients with blood sugar abnormality can have sudden changes in consciousness so this should always be assessed for early.
Consider also where a patient is under the influence of alcohol or has collapsed due for other reasons. Drugs or alcohol may mask physical injuries or medical problems so if in doubt, always continue to assume stroke. The same applies if a patient has ‘fainted’ (syncope) but still appears unwell. Assume stroke until proven otherwise.
Pre-hospital management of the stroke patient: The most critical aspects of stroke patient management are recognition of the problem and transfer of the patient to appropriate care. Brain cells die quickly so the key is to value minutes. Use the FAST scale to assess for stroke potential. If in doubt, assume stroke as the cause
If the patient is conscious, they should be positioned either semi reclined or in a preferred position of comfort. The patient may slump to the affected side and not be able to support themselves. Support any weak arm or leg that may hang and be vulnerable to being injured. The patient may not be able to do so for themselves and may not even be aware.
Attention must be paid to the airway in the stroke patient. Stroke patients may lose control of their airway reflexes and this may be complicated by ongoing vomiting. Lateral positioning may help. Only insert an oropharyngeal airway if there is no gag reflex at all. Patients who are suffering acute stroke should not be allowed to gag on airway devices as this may increase the squeezing within the brain.
When assessing for stroke mimics, treat any hypoglycaemia that is found. Oxygen therapy is only required where hypoxia is indicated using pulse oximetry. If this is not available, oxygen can be administered to any patient in an altered conscious state until it is. Provide assisted ventilation if the patient’s breathing fails.
Importantly, provide a timely situation report to enable rapid paramedic response and early notification to the receiving hospital.
In-hospital management of the stroke patient: Recall that strokes may come from two major causes – thrombotic or haemorrhagic (i.e. blockage or bleed). In hospital management will depend on which is the problem.
The first step will be to confirm the cause and this will be by using computed tomography (CAT) scan. This will determine if the cause is haemorrhage or otherwise. If it is haemorrhage, then decisions will need to be made whether neurosurgery is possible and whether intensive care facilities will be necessary.
If it is a thrombosis stroke current medical therapy makes use of thrombolysis therapy. Recall that the thrombosis is in part a clot in an artery supplying the blood. Thrombolysis is a therapy that can dissolve some of the new clot and so reopen the blocked vessel. For this to work the brain cells must still be alive meaning thrombolysis therapy must be commenced within about 4.5 hours of onset. This makes estimating time of onset of event important.
To provide this therapy, a stroke patient must be transferred to a dedicated stroke service hospital. Not all hospitals will provide the range of services required for full stroke care and local familiarity should be sought prior to transport. Stroke services provide acute care along with ongoing care afterward including rehabilitation, physiotherapy, speech therapy and diet care
Jeff Kenneally www.prehemt.com
Jeff is the author of the 2014 – 2016 Ambulance Victoria First Responder clinical practice protocols and accompanying education program.