Exit to the front wall of the sacral canal. Now the needle with mandrin, which should be kept cut to the patient’s abdomen (ventral), is injected in the ventral and cranial direction at an angle of 70 ° –80 ° to the skin before contact with the anterior wall of the sacral canal . If the needle is sufficiently thick and thick, before this there will be a “failure” through the sacrococgeal membrane (in adults it lies at a depth of 0.5 cm to 4 cm, depending on the body build). It is not necessary to use a large force in the “punching” of this membrane, in order not to injure the periosteum of the anterior wall of the canal (it is very close here) and this does not cause pain or make a “hook” on the needle. If the needle did not “fall through” the membrane, and did not reach the bone, it is necessary to again palpate and evaluate all the bone markers. In 5-7% of adults, it is completely impossible to enter the sacral canal, and other methods of anesthesia are used for them.
Entry into the sacral canal. Now, without pulling out the needle, its sleeve is brought closer to the patient (in the interyagic fold). The needle should be at an angle of 30 ° -45 ° to the skin in this place in women (almost parallel to the back), but at an angle of only 10 ° -20 ° to the skin in this place in men (and black women).
And here it is moved forward, into the sacral canal, not as deep as 4 cm (safer — at 2 cm). At the same time, the needle tip can “scratch” the periosteum of the anterior wall of the canal (you can feel it with your fingers), but if the needle section “looks” ventrally (Fig. 318, position 2), this is not a problem, but only reliable if you sign channel, although specifically to achieve this should not, so as not to damage the venous plexus. The needle can be facilitated (with the right hand) by gently pressing its tube against the patient’s skin with your left index finger (which indicated the puncture site).
Signs of a needle in the sacral canal. Now it is necessary to stop and make sure that the needle actually passed into the canalis sacralis through the hiatus sacralis, and did not get into one of the giatus traps, which is similar to this giatus (see below). The needle must be in the median sagittal plane (not deviating to the side). If it is turned too deep (more than 50 ° to the skin), one might think that its tip was in the bone marrow or even ventral (in front) of the sacrum, “falling” through the bone. It is necessary once again to probe all the bony landmarks: the horns on both sides of the needle, the tailbone — below and on the same midline with the needle, the middle ridge above and also on the midline, both spinae iliacaeposterioressuperiores with an injection site should be equal to an unilateral triangle. In addition, the needle will be capable of paddle-like movements, in which the sacrococigial membrane will play the role of the key; but this is better not to do so as not to injure the vessels in the sacral canal. Having removed the mandrin, they should determine (pressing parallel to the needle) the depth of its introduction — it should in no case reach the line connecting the spinae iliacae posteriores superiores (there is already a dural bag that cannot be pierced so that there is no headache afterwards or unexpected spinal anesthesia now). Immediately after removing the mandrin, an aspiration test should be performed (until the blood in the needle has had time to coagulate).
The air sample is possible if the needle is in the correct position . Having attached a small (up to 5 ml) syringe with 1.5 ml of air to the needle (immediately after removing the mans drain), slightly tighten the pores of the Shen towards themselves (aspiration test) and, if there is no blood or CSF, quickly inject air. If the needle is standing correctly, there will be no resistance, and the patient will not feel anything. If he feels a sharp pain, the tip of the needle is under the periosteum of the canal, and the needle must be tightened. If there was no pain or resistance to the introduction of a small dose of air, as much as 5 ml of air was drawn into the syringe and, gently pressing the fingers of the left hand to the skin above the needle tip, again quickly enter the air. If your fingers feel subcutaneous crepitus, the needle tip is not in the sacral canal, but under the skin. Air can escape from the channel under the skin lateral through the posterior sacral openings (Fig. 119), this is normal. If the patient feels discomfort (tickling or squeezing) in the thighs or berries during the introduction of the second, larger portion of air, this will also confirm the correct position of the needle. If you attach either your ear or a stethoscope to the lumbar spine, you can hear the correct position of the needle when introducing air characteristic sound, which will confirm its entry into the epidural space.
The introduction of the catheter (through the needle or above the needle, if the puncture was done by intravenous cannula on the needle) is carried out with the certainty that the needle is in the sacral canal. If so, the short plastic cannula (if put on the needle) will pass easily. When conducting a soft catheter through the lumen of the needle, the resistance will be no greater, or even less, than with intervertebral epidural catheterization. This is not surprising: the tip of the needle is not bent (such needles are not needed for caudal access), and the catheter should not bend, since from the very beginning it runs parallel to the hard shell of the spinal cord. If a long epidural catheter can be carried out far, by 12-13 cm (which is difficult for adults), good epidural anesthesia of the lumbar and even lower thoracic segments can be obtained.