Single spinal anesthesia has been widely used in short lower abdomen, perineal and lower limb surgery, with the advantages of less medication, quick onset and perfect block.
Ligamentum flavum is composed of elastic fiber, with the growth of age, ligamentum flavum can appear hyperplasia and hypertrophy, elastic loss, calcification, to the waist, leading to lumbar spinal stenosis, compression of ponytail, and then cause waist and leg pain. In contrast to ligamentum flavum, the interspinous and suprasspinous ligaments are composed of collagen fibers. Therefore, this resistance against the needle may disappear. False cavity formation caused by the degeneration of the intervertebral ligament, such degenerative changes occur frequently in the elderly, usually in the lumbar area, when the epidural needle enters such a false cavity or cyst will also lead to sudden resistance to disappear, resulting in a mistake for having reached the epidural cavity(5).There are some cases of intervertebral space stenosis or some cases of interspinous ligament calcification or osteogenesis. Needneedle resistance was always large at puncture, this can often be cases of multiple episodes of epidural or subarachnoid puncture or cases of congenital thin ligaments, The sensation of breakthrough is also not obvious during epidural puncture. Some study concluded that the incidence of midline gap in the thoracic ligament is lower than the cervical segment, but higher than the waist(6, 7). Therefore, the epidural puncture is not reliable, especially the median puncture. In clinical work, we found that some female patients of older grade were lack of puncture breakthrough, which posed a challenge to our clinical work, especially young doctors. Similarly, the sense of puncture breakthrough was hardly felt in our experimental group.
An epidural anaesthetic typically involves inserting a larger diameter needle than a spinal needle in order to allow epidural catheter placement. The epidural needle passes through the same tissues as a spinal needle but stops short of penetrating the dura. The tip of the epidural needle is thus positioned in the epidural space which lies just before the dura and subarachnoid space. An epidural catheter is often passed through the epidural needle which is then removed. Although the spinal and epidural techniques are similar, there are still certain differences, such as the difficulty of the puncture and the damage to the patient's ligaments(8). Muranakal observed the midline approaches or lateral approach by epidural puncture, the success rate of one attempted was 94% and 89%, respectively(9). There was no statistically significant difference. But lateral approaches were more likely to touch nerve roots, so we chose the midline approaches. Neither the control group nor the experimental group had nerve injury, these are all the results that we want to get.
During spinal anesthesia, an introducer needle is often used as a means of stabilizing subsequent placement of a small-gauge needle. However, we finally chose not to use the guide needle, because we felt that it could improve the breakthrough sense of puncture and was conducive to identifying the puncture level, and the current puncture needle does not look very fragile, and it's not easy to bend and break. Of course, before we reach the bone, the speed must be slow, otherwise the needle will bend or even break.
For 25 G Whitacre pencil-point spinal needle, the incidence of postoperative headache (PDPH) was 2.2%(10). The midline approaches can reduce the probability of headache after spinal anesthesia and increase the puncture success rate(11) .
When we pierce through the arachnoid to reach the bone, there may be more cerebrospinal fluid leakage than CSEA, but our experimental group did not have postdural puncture headache, maybe these lost CSF is not enough to cause PDPH. Similarly, we hardly found blood flowing out of the puncture needle, although there are many small blood vessels before reaching the bone, which may be because the puncture needle is thin enough(0.5mm).
Clinically, the phenomenon of pain in puncture point and low backache occurs after CESA, and some patients' backache can reach a moderate degree.Some investigations have shown that the incidence of backache after spinal anesthesia can reach 2% -31%, which seriously affects the postoperative quality of life of patients, so the backache after spinal anesthesia should get more attention(12). For the pathophysiological mechanism of lumbar back pain after intraspinal anesthesia, some study found that the damage was mainly related to the suprasal lumbar back ridge ligament, interspinal ligament and flates ligament caused by anesthesia puncture, as well as the induced aseptic inflammation and aseptic synovitis. The common reasons related to lumbar back pain after spinal anesthesia are, including operation method, puncture path, puncture number, and puncture needle thickness. Repeated puncture, puncture force, and puncture needle thickness are directly related to the occurrence of backache after spinal anesthesia. Because it's simple, the midline approaches can reduce the probability of headache after spinal anesthesia and increase the puncture success rate(11).
We found that in patients with CSEA, the postoperative puncture point or backache rate was significantly higher than that in those with pencil-point spinal needle. This may be due to the high success rate of puncture caused from the traditional puncture method relying on the sense of breakthrough, of course, a smaller diameter needle also plays a key role: compared with CESA, 25G needle puncture has minimally invasive advantages: less damage to suprasinal ligament, interspinal ligament, flavate ligament and dura; reduce the damage probability of spinal nerve and epidural blood vessels.
In summary, although the success rate of midline approaches is relatively high(9), sometimes the breakthrough feeling is not obvious. The results from this study indicate that our method can significantly improve the success rate when the breakthrough feeling is not obvious, and will not cause nerve damage, PDPH, bleeding, back pain and other complications. For beginners, you can try, as a supplement to the puncture method.