【Monday】You can't miss the key point of the anesthesia junior high school exam point intensive lecture 04

The largest artery at the root of the spinal cord

Analysis: The largest artery at the root of the spinal cord (Adamkiewicz artery) usually originates in the intercostal arteries at the T5 and T12 levels and the abdominal aorta in the lumbar region

Pudendal nerves

Analysis: The sensation

1) Superior gluteal nerve (L4--S1)

2) Sub-gluteal nerve (L5--S2)

3) Pudendal nerves (S2, S3, S4)

4) Sciatic nerve (L4, L5, S1, S2, S3)

The sympathetic fibers that innervate the pelvis originate from T10 to L2 and form the epigastric plexus

Cholanges

Analysis: Cerebrospinal fluid (CSF) is produced by choroidal plexus

Cerebral blood vessels constrict, cerebral blood flow unchanged

Analysis: Cerebral perfusion pressure (CCP) is to maintain the pressure value
of blood perfusion in brain tissue.

It is obtained by
subtracting intracranial pressure (ICP) from mean arterial pressure (MAP).

If jugular venous pressure (JVP) is higher than ICP, then cerebral perfusion pressure = MAP-JVP
.

Normal cerebral perfusion pressure in adults is 70 to 90 mmHg
.

If the patient's cerebral perfusion pressure < 70 mmHg will present cerebral ischemia
.

Self-regulation of cerebral blood flow, that is, according to the MAP, the intracranial blood vessels expand or contract to ensure constant cerebral blood flow
.

When the cerebral perfusion pressure decreases, cerebral blood vessels expand to ensure constant cerebral blood flow; Conversely, when cerebral perfusion pressure rises, cerebral blood vessels increase peripheral resistance by contracting to ensure constant
cerebral blood flow.

When the MAP is 50-150mmHg, cerebral blood flow can ensure good self-regulation ability
.

When map < 50 mmHg, the cerebral blood vessels have been expanded to the maximum extent, and further reduction of map will lead to a linear decrease in cerebral blood flow (Figures 2-6
).

5.
Regarding cerebral blood flow (CBF), when PaO2 is higher than ____mmHg, CBF does not change
with the change of PaO2.

60mmHg

Analysis: CBF is about 750ml/min, which is equivalent to about 15% of the heart output (about 2% of the body weight).


In other words, 50 ml/ (100 g brain tissue · min).


Cerebral blood flow is not evenly distributed throughout the brain, and areas of metabolic activity require more brain perfusion
.

It is for this reason that gray matter requires 4 times more cerebral blood flow than white matter, which consists
only of the axons of nerve cells as well as support cells.

All inhaled anesthetics can cause a dose-dependent increase
in CBF.

This effect is most pronounced in halothane, which is also present in isoflurane, sevoflurane, and deflurane, especially when inhaled concentrations greater than 1.
5 MAC
.

However, inhaled anesthetics can increase CBF while at the same time reducing brain metabolism, a phenomenon known as the "separation phenomenon" because the decrease in the demand for brain metabolism does not reduce
the proportion of CBF.

Cerebrovascular resistance and cerebral perfusion pressure are the two major determinants
of CBF.

Cerebrovascular resistance is mainly affected
by intravascular PaCO2PaO2.

In normal humans, CBF increases linearly as PaCO2 increases (Figures 2-7
).

Normal or high partial pressure of blood oxygen has less effect on CBF, and when PaO2 < 60mmHg, cerebral blood vessels will be significantly expanded, and then CBF will increase, ensuring the supply
of oxygen to brain cells.

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