Applied Physiology: Lecture 2 - Neuro Cont'd (Spinal) Flashcards
(119 cards)
1
Q
What is the autonomic nervous system (ANS)?
A
A subdivision of the peripheral nervous system that regulates body activities generally not under conscious control.
2
Q
What type of muscles does the visceral motor innervate?
A
Non-skeletal (non-somatic) muscles.
3
Q
What does ‘autonomic’ mean in the context of the nervous system?
A
It means independent; not automatic.
4
Q
What types of muscles and organs are served by the autonomic nervous system?
A
- Cardiac muscle
- Smooth muscle
- Internal organs
- Skin
5
Q
What is the basic anatomical difference between the somatic and autonomic nervous systems?
A
In the somatic division, motor neuron cell bodies reside in the CNS and their axons extend to skeletal muscles. In the autonomic system, there are chains of two motor neurons: a preganglionic neuron in the brain or spinal cord and a ganglionic neuron in a ganglion outside the CNS.
6
Q
What is the role of the hypothalamus in the autonomic nervous system?
A
It regulates autonomic tone, which is the balance between sympathetic and parasympathetic activity, and serves as the major control and integration center of the ANS.
7
Q
What is the parasympathetic nervous system also known as?
A
The craniosacral system.
8
Q
Where are the preganglionic neurons of the parasympathetic nervous system located?
A
In the brain stem or sacral levels of the spinal cord (S2-S4).
9
Q
Which cranial nerves are associated with the parasympathetic nervous system?
A
- Cranial nerve III
- Cranial nerve VII
- Cranial nerve IX
- Cranial nerve X
10
Q
What neurotransmitter is used at the end organ and preganglionic synapse in the parasympathetic nervous system?
A
Acetylcholine.
11
Q
What is the sympathetic nervous system also referred to as?
A
The thoracolumbar system.
12
Q
Where are the preganglionic neurons of the sympathetic nervous system located?
A
In the lateral horn of gray matter from T1 to L2.
13
Q
What physiological responses are associated with sympathetic activation?
A
- Sweating
- Hair standing on end
- Increased blood pressure
- Dry mouth
- Pupil dilation
- Increased heart and respiratory rates
- Liver glucose release
14
Q
What neurotransmitter is primarily used by postganglionic sympathetic fibers?
A
Norepinephrine (noradrenaline).
15
Q
What are cholinergic fibers?
A
Fibers that contain and use acetylcholine (ACH) as the neurotransmitter, including all preganglionic autonomic fibers and all postganglionic parasympathetic fibers.
16
Q
What are adrenergic fibers?
A
Fibers that contain and use norepinephrine as the neurotransmitter, including sympathetic postganglionic fibers to the heart, smooth muscle, and other glands.
17
Q
What are the two types of acetylcholine receptors in the autonomic nervous system?
A
- Muscarinic receptors
- Nicotinic receptors
18
Q
What effects do muscarinic receptors cause?
A
Effects similar to parasympathetic stimulation, found in the heart, smooth muscle, and glands.
19
Q
What type of response do muscarinic receptors mediate?
A
A slow, prolonged response via G-protein coupled receptors.
20
Q
What does nicotine act on in the nervous system?
A
Ganglionic and skeletal muscle synapses, nerve membranes, and sensory endings.
21
Q
What is the function of nicotinic receptors?
A
They mediate fast synaptic transmission at ganglionic synapses and at skeletal muscle.
22
Q
What type of receptor is a ligand-gated ion channel receptor?
A
It mediates a fast, short-lived response.
23
Q
What are the two subdivisions of adrenergic receptors?
A
- α (alpha) receptors
- β (beta) receptors
24
Q
What is the function of α₁ adrenergic receptors?
A
They mediate smooth muscle vasoconstriction and are located on sympathetic effector organs.
25
Where are α₂ adrenergic receptors located and what is their function?
They are located on the membrane of presynaptic neurons and modulate norepinephrine release in an inhibitory manner.
26
What is the primary location and function of β₁ adrenergic receptors?
Found primarily on cardiac tissue, they increase the rate and force of contraction.
27
What is the role of β₂ adrenergic receptors?
They mediate smooth muscle relaxation and are found on smooth muscle of some organs.
28
Which cranial nerves contain preganglionic fibers of the parasympathetic nervous system (PNS)?
* Oculomotor (III)
* Facial (VII)
* Glossopharyngeal (IX)
* Vagus (X)
29
What is the primary function of the vagus nerve in the PNS?
It innervates visceral organs of the thorax and abdomen, stimulating digestion and reducing heart rate and blood pressure.
30
Where are the preganglionic cell bodies of the vagus nerve located?
In the dorsal motor nucleus in the medulla.
31
What is referred pain?
Pain in visceral organs perceived as originating from somatic regions of the body that receive innervation from the same spinal cord segments.
32
What are the three pathways an axon may take in the sympathetic nervous system (SNS)?
* Synapse with postganglionic neurons in the ganglion it first reaches
* Continue through the sympathetic trunk ganglion to a prevertebral ganglion
* Pass through both ganglia to the adrenal medulla
33
What are dermatomes?
Areas of skin innervated by a single spinal nerve.
34
What spinal nerves innervate the diaphragm?
C3-5 via the phrenic nerve.
35
What muscle functions are associated with C5-6 spinal nerves?
* Shoulder abduction
* External rotation
* Flexion
* Elbow flexion
36
What is the sympathetic response characterized by?
* Tachycardia
* Vasoconstriction
* Bronchodilation
* Decreased GI motility
* Sphincter constriction
* Inhibited bladder evacuation
* Mydriasis
* Diaphoresis
37
What is the parasympathetic response characterized by?
* Bradycardia
* Vasodilation
* Bronchoconstriction
* Increased GI motility
* Sphincter relaxation
* Bladder evacuation
* Miosis
38
What types of injuries can affect the spinal cord?
* Ischemic injury
* Compression injury
* Traumatic injury
39
What is spinal shock?
Loss of temperature regulation and spinal cord reflexes below the level of the injury.
40
What are common effects of high thoracic and cervical spinal cord injuries?
Reductions in systemic blood pressure due to loss of sympathetic nervous system activity and bradycardia.
41
What is the role of the sympathetic nervous system in relation to blood pressure?
It maintains systemic vascular resistance; loss of its activity can lead to decreased blood pressure.
42
What is the effect of T1-T4 sympathetic innervation loss on the heart?
It can lead to bradycardia.
43
What is the outcome of a complete injury at the C1-2 level?
Tetraplegia with complete phrenic nerve and respiratory muscle paralysis requiring permanent mechanical ventilation.
44
What potential recovery is associated with a C3-4 spinal cord injury?
Potential for some recovery of respiratory function.
45
What characterizes incomplete tetraplegia at the C5-T1 level?
Variable upper extremity involvement with some paralysis of intercostal and abdominal muscles, leading to paradoxical respiration.
46
What is the impact of a T1-8 spinal cord injury?
Paraplegia with loss of abdominal muscle control.
47
How does a T9-12 spinal cord injury affect abdominal muscle control?
Paraplegia with preserved abdominal muscle control.
48
What is the result of an L1-L5 spinal cord injury?
Incomplete paraplegia with urinary incontinence.
49
What complications arise from an S1-S5 spinal cord injury?
Incomplete paraplegia with gastrointestinal dysmotility and urinary retention.
50
What is a complete transection of the spinal cord?
A severe injury resulting in total loss of function below the level of injury.
51
What are the phases of neurologic symptoms in spinal shock?
* Phase 1: Flaccid paralysis
* Phase 2: Return of reflexes
* Phase 3: Early hyperreflexia
* Phase 4: Hyperreflexia and contractures
52
What is the goal of managing primary spinal cord injury?
To stabilize and prevent further spinal cord injury.
53
What differentiates primary injury from secondary injury in spinal cord injuries?
Primary injury occurs at the time of the initial insult, while secondary injury is due to ongoing insults that damage previously injured or unharmed neurons.
54
What are common acute treatments for spinal cord injury?
* Intubation
* IVF bolus
* Mechanical ventilation
* Inotropic support
55
What is the role of Baclofen in spinal cord injury management?
It modulates GABA B, decreases alpha motor neuron activity, and reduces skeletal muscle tone.
56
What is autonomic dysreflexia and when does it occur?
A condition that can occur after spinal cord injury above T6, characterized by hypertension, bradycardia, and flushing.
57
What triggers autonomic dysreflexia?
Stimuli such as cutaneous pain or distension of hollow viscus.
58
What are the symptoms of autonomic dysreflexia?
* Hypertension (SBP > 200 mmHg)
* Bradycardia
* Sweating
* Flushing above the injury level
59
How can autonomic dysreflexia be prevented?
By avoiding triggers and using dense regional blocks or deep volatile anesthesia.
60
What is the significance of the baroreceptor reflex in autonomic dysreflexia?
It causes bradycardia due to intense constriction of vascular beds below the level of injury.
61
What are the common sequelae of chronic spinal cord injury?
* Impaired alveolar ventilation
* Cardiovascular instability
* Infections
* Anemia
* Altered thermoregulation
62
What is a common cause of death in patients with chronic spinal cord transection?
Renal failure.
63
What is the risk associated with spinal cord injury regarding venous health?
Increased risk of deep venous thrombosis.
64
What is the treatment approach for autonomic dysreflexia?
Avoid triggers and consider short-acting vasodilators.
65
What is autonomic dysreflexia (AD) and how does it manifest?
AD results from a spinal cord injury above T6, causing segmental autonomic reflexes to activate en masse due to stimuli like cutaneous pain or hollow viscus distension. Symptoms include hypertension (SBP > 200 mmHg), bradycardia, flushing, and sweating above the injury level.
66
What are the causes and symptoms of Cauda Equina Syndrome?
Cauda Equina Syndrome is caused by L1-L5 nerve root compression, often due to a herniated disc or trauma. Symptoms include saddle anesthesia, sciatica, bladder dysfunction, weakness, and pain. Treatment is emergent to prevent irreversible damage.
67
What are the symptoms of Anterior Cord Syndrome?
Anterior Cord Syndrome results from a lack of blood supply to the anterior spinal artery, leading to loss of motor function and loss of pain and temperature sensation, while fine touch, proprioception, and vibration remain intact.
68
What is the significance of the anterior spinal artery in spinal cord perfusion?
The anterior spinal artery supplies 2/3 of the spinal cord's blood supply and is a single artery with limited collateral flow, making it a common cause of spinal cord infarct.
69
What is the formula for spinal cord perfusion pressure (SCPP)?
SCPP = MAP - ISCP, where MAP is mean arterial pressure and ISCP is intracranial spinal pressure.
70
What are the anesthetic considerations for spine surgery?
Anesthetic considerations include maintaining spinal cord perfusion, ensuring patient safety and comfort, creating a favorable environment for neuro monitoring, and avoiding ischemic optic neuropathy.
71
What are the risk factors associated with postoperative vision loss (POVL)?
* Obesity
* Male sex
* Hypertension
* Diabetes
* Coronary artery disease
* Long anesthetic duration (> 6-8 hours)
* Large blood loss (>800 mL)
* Large crystalloid administration
* Use of the Wilson Frame
72
What is the typical time frame for autonomic dysreflexia to become evident after a spinal cord injury?
AD typically becomes evident 1-6 months following a spinal cord injury above T6.
73
What is the role of the baroreceptor reflex in bradycardia associated with autonomic dysreflexia?
Bradycardia in AD results from the baroreceptor reflex due to intense constriction of vascular beds below the level of the injury.
74
What is the common cause of anterior cord syndrome outside of neuro cases?
Non-neuro causes of anterior cord syndrome can include systemic hypotension or ischemia.
75
What are the key goals of anesthesia during spine surgery?
Goals include maintaining spinal cord perfusion while keeping the patient asleep, safe, and comfortable, and creating an environment suitable for neuro monitoring.
76
What are the common surgical procedures associated with spine surgery?
* Laminectomy
* Discectomy
* Fusion
* PSO (posterior spinal osteotomy)
* Tumor removal
* Trauma repair
* Revision surgery
77
What are the potential consequences of delaying treatment for Cauda Equina Syndrome?
Delaying treatment can lead to permanent irreversible damage, including bladder and bowel dysfunction.
78
What is the relationship between spinal cord injury and hemodynamic fluctuations?
The spinal cord does not tolerate fluctuations in hemodynamics well, which can lead to complications such as autonomic dysreflexia.
79
How can anesthetic techniques help prevent autonomic dysreflexia during surgery?
Dense regional blocks or deep volatile anesthetics can help prevent the onset of autonomic dysreflexia during surgical procedures.
80
What are the symptoms of central cord syndrome?
Central cord syndrome is characterized by motor loss and variable sensory loss due to injury to the central gray matter.
81
What is the significance of the artery of Adamkiewicz?
The artery of Adamkiewicz supplies blood to the lower two-thirds of the spinal cord and is crucial for preventing spinal cord infarction.
82
What are the potential effects of spinal cord perfusion on surgical outcomes?
Maintaining adequate spinal cord perfusion is critical for preventing complications such as ischemic damage and ensuring optimal surgical outcomes.
83
What is the typical presentation of symptoms in patients with autonomic dysreflexia?
Patients may experience severe headaches, sweating, and flushing above the level of injury due to autonomic dysreflexia.
84
What should be monitored during anesthesia for spine surgery?
Extra monitors may be required to ensure adequate neuro monitoring and spinal cord perfusion during anesthesia for spine surgery.
85
What should be avoided to ensure patient safety during surgery?
* Excessive blood loss (>800mL)
* Prolonged surgical duration (>6-8 hours)
* Hypotension
* Poor positioning
86
What is the recommended patient positioning to avoid complications?
Place the patient in reverse Trendelenburg with eyes without pressure and neck in a neutral position.
87
What are the neuro monitoring techniques mentioned?
* SSEPs
* MEPS
* BAEP (to be discussed later)
* EMG
88
What does SSEP assess?
The functional status of the cerebral cortex and spinal cord, recording responses to infer the physiological state of the neural tract.
89
What changes should be monitored in SSEP?
* Changes in amplitude
* Changes in latency
90
How do volatile anesthetics affect SSEP?
They increase latency and decrease amplitude.
91
What is the effect of N2O on SSEP?
N2O increases latency and decreases amplitude.
92
What is the effect of opioids on SSEP?
Opioids increase latency and decrease amplitude.
93
What is the effect of ketamine on SSEP?
Ketamine decreases latency and increases amplitude.
94
What are the anesthesia considerations for SSEP?
Restrict N2O and volatile agents to less than 1-0.5 MAC; opioids and/or ketamine are desirable.
95
What does MEP stand for and what does it predict?
MEP stands for Motor Evoked Potential and may be an earlier indicator of potential spinal cord injury.
96
What is the effect of N2O on SSEP?
Increases latency and decreases amplitude
## Footnote
N2O is known to have a significant impact on sensory evoked potentials.
97
What is the effect of opioids on SSEP?
Increase latency and decrease amplitude
## Footnote
Opioids are commonly used in anesthesia but can alter SSEP responses.
98
What is the effect of ketamine on SSEP?
Decreases latency and increases amplitude
## Footnote
Ketamine is unique among anesthetics in its effects on SSEP.
99
What are the anesthesia considerations for SSEP?
Restrict N2O and volatile agents to less than 1-0.5 MAC; opioids and/or ketamine are desirable
## Footnote
Proper management of anesthetics is crucial for maintaining SSEP integrity.
100
What does MEP stand for and what does it predict?
Motor Evoked Potential; may be an earlier predictor of impending damage to the spinal cord
## Footnote
MEP monitoring can provide valuable insights during surgical procedures.
101
What is the anesthetic effect of volatile agents on MEP?
Significantly decrease amplitude and increase latency
## Footnote
Awareness of these effects can guide anesthetic choices.
102
What are the anesthetic considerations for MEPs?
Total intravenous anesthesia is desirable; Etomidate, Propofol, and Ketamine are preferred
## Footnote
This approach helps minimize interference with MEP monitoring.
103
What factors negatively affect MEPs?
* Hypo/hyperthermia
* Anemia
* Hypotension
* Hypoxia
* Hypocarbia
## Footnote
These factors can compromise the accuracy of MEP readings.
104
What is the effect of neuromuscular blockade on EMG?
Contraindicated as EMG is largely unaffected by induction and maintenance drugs
## Footnote
Understanding this helps in planning neuromuscular management.
105
What anesthetic agents are largely unaffected by EMG?
* Inhalational agents
* N2O
* Sedatives
* Opioids
* Hypnotics
## Footnote
These agents do not significantly alter EMG readings.
106
What are potential causes of SSEP changes?
* Spine positioning
* Brachial plexus injury
* Spine changes with ligament release
* Cord manipulation
* Hematoma
* Deliberate hypotension
## Footnote
Identifying these causes is essential for monitoring during surgery.
107
What is the effect of propofol on SSEP?
Minimal effects on cortical responses
## Footnote
Propofol is often favored for its stability in SSEP monitoring.
108
What is the effect of STP on SSEP?
No effect on latency and amplitude
## Footnote
STP can be safely used without impacting SSEP outcomes.
109
What is the significance of monitoring amplitude and latency in SSEP and MEP?
Help identify impending neural compromise and allow for intervention to avert permanent injury
## Footnote
Monitoring these parameters is critical for patient safety.
110
What is the role of controlled muscle relaxation in MEPs?
Facilitate muscle responses during monitoring
## Footnote
This technique is important for accurate MEP assessment.
111
The extent of physiological effects of spinal cord injury is dependent on what?
Level of injury, most severe at the cervical level
## Footnote
Understanding injury levels helps predict patient outcomes.
112
What is hypotension a result of in spinal cord injury?
Loss/decrease of sympathetic nervous system activity and systemic vascular resistance
## Footnote
This condition can lead to neurogenic shock which may last for weeks.
113
What are major concerns caring for those with spinal cord concerns?
* Maintain adequate blood flow and oxygen
* Optimize operative conditions
* Smooth/rapid emergence
## Footnote
These concerns are critical for patient recovery and safety.
114
What should be considered when using Succinylcholine in patients with motor deficits?
Should be used with caution due to risk of hyperkalemia
## Footnote
This risk is particularly important in patients with neuromuscular issues.
115
What is advised regarding acute spinal cord injury and neck manipulation?
Avoid excessive movement
## Footnote
Minimizing movement is essential to prevent further injury.
116
Can Succinylcholine be used in the first few hours following spinal cord injury?
Can be used without significant risk of hyperkalemia
## Footnote
Timing of administration is important to minimize risks.
117
What is the sequelae of chronic spinal cord injury?
* Impaired alveolar ventilation
* CV instability manifested as autonomic hyperreflexia
* Chronic pulmonary and GU infections
* Anemia
* Altered thermoregulation
## Footnote
These complications can significantly affect quality of life.
118
What are cervical and thoracic spinal cord injuries at risk of developing?
* Autonomic hyperreflexia in response to surgery
* Bowel distention
* Bladder distention
## Footnote
These conditions require careful monitoring during surgical procedures.
119
How can autonomic hyperreflexia be prevented?
General or spinal anesthesia as both block afferent limp pathway
## Footnote
Local anesthesia techniques may not be effective in preventing this condition.
