Adult male patients (ASA I-II) undergoing cervical laminoplasty were allocated to either the caudal block (CB, N.=24) or non-block (NB, N.=24) group. Following anesthesia induction, urinary catheterization was performed using a 16 French Foley catheter. Thereafter, an ultrasound-guided caudal block was performed with 8 ml of % ropivacaine and 100 µg of fentanyl for patients in group CB, while group NB did not receive a caudal block. We assessed urinary catheter-induced discomfort as mild, moderate, or severe at 0, 2, 6, 10, and 18 hours after surgery, and compared the incidence and severity of discomfort between the groups using a randomized double-blind design.
The ultrasound-guided caudal block was first described by Klocke and colleagues in 2003 [ 24 ] and has, since then, gained increasing popularity. Several studies from various ethnic populations have repeatedly reported very high successful rates (–100%) of ultrasound-guided caudal injection [ 11 , 12 , 25 – 27 ]. The patient can be placed in prone or lateral decubitus position. Usually, a 7–13 MHz, liner transducer will suffice for most caudal epidural injection; however, a 2–5 MHz, curved transducer may be needed in obese patients. The ultrasound transducer was first placed transversely at the midline to obtain the transverse view of sacral hiatus (Figure 4 ). The two sacral cornua appear as two hyperechoic structures. Between the sacral cornua are two band-like hyperechoic structures; the superficial one is the SCL, and the deep one is the dorsal surface of sacral bone. The sacral hiatus was the hypoechoic region between the 2 band-like hyperechoic structures [ 25 ]. At this level, the ultrasound transducer is rotated 90 degrees to obtain the longitudinal view of sacral hiatus (Figure 5 ). Under longitudinal view, the block needle is inserted using the “in-plane” technique. The block needle can be visualized in real time, piercing the SCL, entering the sacral hiatus, but cannot be visualized beyond the apex of sacral hiatus. Therefore, without knowledge of dural sac termination from image study in advance, it is suggested that advancement of needle tip beyond the apex of sacral hiatus be limited to 5 mm to avoid dural puncture because the distance between the apex of sacral hiatus and dural sac termination can be as short as less than 6 mm [ 7 ].
In a retrospective study, Narozny and associates (2001) investigated the clinical effectiveness of nerve root blocks (., peri-radicular injection of bupivacaine and triamcinolone) for lumbar mono-radiculopathy in patients with a mild neurological deficit. These researchers analyzed 30 patients (aged 29 to 82 years) with a minor sensory/motor deficit and an unequivocal MRI finding (20 disc herniations, 10 foraminal stenoses) treated with a SNRB. Based on the clinical and imaging findings, surgery (decompression of the nerve root) was justifiable in all cases. Twenty-six patients (87 %) had rapid (1 to 4 days) and substantial regression of pain, 5 required a repeat injection. Furthermore, 60 % of the patients with disc herniation or foraminal stenosis had permanent resolution of pain, so that an operation was avoided over an average of 16 months (6 to 23 months) follow-up. The authors concluded that SNRBs are very effective in the non-operative treatment of minor mono-radiculopathy and should be recommended as the initial treatment of choice for this condition.