The key points you can't miss · Anesthesia Junior and Intermediate Test Center Intensive Lecture 04

Notes Guan Yong 1.
One patient was going to undergo abdominal aortic aneurysm repair after open abdominal aorta occlusion
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Postoperatively, the patient developed paraplegia but retained proprioception
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If the spinal cord injury in this patient was caused by a blockage of the abdominal aorta, the blood vessel most likely to be affected is the artery of _________
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Analysis of the largest artery of the spinal root: The largest artery of the spinal root (Adamkiewicz artery) usually originates from the intercostal arteries at the T5 and T12 levels and the abdominal aorta at the waist
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Although sometimes anatomic variations exist, the largest artery of the spinal root (the artery of Adamkiewicz) is considered to be the main supply vessel for the anterior spinal artery of the lower thoracic and lumbar spinal cords
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Anterior cord syndrome (ACS) can be caused by a number of causes, including hypoperfusion of the anterior spinal artery
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ACS is mainly characterized by loss of motor function and loss of pain and temperature sensation below the level of the affected spinal cord
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However, proprioceptive, vibratory and tactile pressure sensations are not affected
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In the above case, the surgical procedure resulted in occlusion of the largest artery in the spinal root, which ultimately resulted in ACS
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2.
In the second stage of labor, the parturient has obvious perineal pain
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The sensory innervation of the perineum originates from the _______ nerve
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Pudendal nerve analysis: The pudendal nerves (S2, S3, S4) innervate the perineal sensation
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The pelvis is innervated by the lumbosacral trunk, sacral plexus, coccygeal plexus, pelvic sympathetic trunk, and parasympathetic nerves
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The sacral plexus originates from L4, L5, S1, S2, S3 and part of S4 (where L4 and L5 are collectively referred to as the lumbosacral trunk)
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The sacral plexus has many branches, including: 1) Superior gluteal nerve (L4--S1) 2) Inferior gluteal nerve (L5--S2) 3) Pudendal nerve (S2, S3, S4) 4) Sciatic nerve (L4, L5, S1) , S2, S3) The sympathetic fibers that innervate the pelvis originate from T10 to L2, forming the epigastric plexus
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The epigastric plexus further divides into left and right hypogastric plexuses at the level of the sacral promontory
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The parasympathetic and afferent nerves of the pelvic viscera are composed of pelvic visceral nerves originating from S2-S4
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The hypogastric plexus and the pelvic splanchnic nerves together constitute the hypogastric plexus (containing sympathetic and parasympathetic components)
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The hypogastric plexus is further divided into other plexuses, which mainly control defecation, urination, ejaculation, and orgasm
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3.
In the central nervous system, cerebrospinal fluid is produced in _______
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Analysis of the choroid plexus: Cerebrospinal fluid (CSF) is produced by the choroid plexus
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The choroid plexus is distributed in the lateral, third and fourth ventricles
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The choroid plexus is formed by the vascular pia embedded in the ventricle, which is highly folded in the ventricle, showing a cauliflower shape
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The generation of CSF is both an active secretion process and a passive filtering process
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CSF has a well-defined circulation pattern, is produced from the lateral ventricles (where the vast majority of CSF is produced), enters the third ventricle through the interventricular foramen, then enters the fourth ventricle through the midbrain aqueduct, and finally passes through the median foramen and 2 A lateral foramen leaves the ventricle and enters the subarachnoid space
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Subsequently, CSF flows into the spinal cord via the foramen magnum
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CSF is reabsorbed above the cerebral hemispheres, mainly through reabsorption into the venous system by bulk arachnoid villi
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The subarachnoid space is formed by the walls of the meningeal sinuses
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The driving force for resorption is hydrostatic pressure
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4.
A 30-year-old male patient with a basal blood pressure of 120/80mmHg.
The general anesthesia was shallow during tracheal intubation, and the blood pressure rose to 175/90mmHg
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At this time, elevated blood pressure can cause cerebral blood flow to the patient's cerebrovascular _______, cerebral blood flow ______
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(Assuming constant intracranial pressure) cerebral vasoconstriction, cerebral blood flow unchanged
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Analysis: Cerebral perfusion pressure (CCP) is the pressure value that maintains blood perfusion in cerebral tissue
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It is derived from mean arterial pressure (MAP) minus intracranial pressure (ICP)
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If jugular venous pressure (JVP) is higher than ICP, then cerebral perfusion pressure = MAP-JVP
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The normal cerebral perfusion pressure in adults is 70-90mmHg
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Cerebral ischemia will occur if the patient's cerebral perfusion pressure is <70 mmHg
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Self-regulation of cerebral blood flow, that is, according to the difference of MAP, intracranial blood vessels expand or contract to ensure constant cerebral blood flow
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When cerebral perfusion pressure decreases, cerebral blood vessels dilate to ensure constant cerebral blood flow; on the contrary, when cerebral perfusion pressure increases, cerebral blood vessels increase peripheral resistance by constricting to ensure constant cerebral blood flow
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When MAP is 50-150mmHg, cerebral blood flow can ensure good self-regulation ability
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When MAP<50mmHg, the cerebral blood vessels have been dilated to the maximum extent, and further reduction of MAP will lead to a linear decrease in cerebral blood flow (Figure 2-6)
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5.
Regarding cerebral blood flow (CBF), when PaO2 is higher than ____mmHg, CBF does not change with the change of PaO2
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60mmHg analysis: CBF is about 750ml/min, which is equivalent to about 15% of cardiac output (about 2% of human body weight)
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In other words, 50ml/(100g brain tissue·min)
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Cerebral blood flow is not evenly distributed throughout the brain, and metabolically active regions require more cerebral perfusion
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It is for this reason that gray matter requires four times as much cerebral blood flow as white matter, which consists only of the axons of nerve cells and supporting cells
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All inhalational anesthetics cause a dose-dependent increase in CBF
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This effect was most pronounced with halothane, but also with isoflurane, sevoflurane, and desflurane, especially at inhaled concentrations greater than 1.
5 MAC
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However, inhalation anesthetics can increase CBF while decreasing brain metabolism, a phenomenon known as the "dissociation phenomenon" because a reduction in brain metabolic demand does not result in a lower proportion of CBF
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Cerebrovascular resistance and cerebral perfusion pressure are the two major determinants of CBF
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Cerebrovascular resistance is mainly affected by intravascular PaCO2PaO2
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In normal humans, CBF increases linearly with increasing PaCO2 (Figure 2-7)
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Normal or high blood oxygen partial pressure has little effect on CBF, while when PaO2<60mmHg, cerebral blood vessels will expand significantly, and then CBF will increase, ensuring the supply of oxygen to brain cells
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