What is the relationship between caudal block and sacral hiatus

The caudal approach of the epidural space is done through the sacral hiatus 1. proximal to the vertex of the hiatus, at a 45º angle in relation to the skin. .. Galante D - Utility of ultrasound in needle placement for caudal blocks in children . The sacral hiatus is a defect in the lower part of the posterior wall of the sacrum to avoid this as a total spinal block will occur if the dose for a caudal block is. morphometric measurements of the sacrum in relation to sacral hiatus in dry help in determining the location of the sacral hiatus during caudal epidural block.

Eleven direct morphometric measurements of importance for CEB, relating to the sacral vertebra and hiatus, were obtained Fig. Fig 1 View large Download slide The measured parameters. Statistical analysis Data were expressed as mean sdmedian and range. Analyses were performed using SPSS software, version 9. Results Total posterior closure was found in two sacrums, which were excluded from the study. Agenesis of the hiatus was detected in six 6.

The average length of the sacral hiatus was The length of the sacral hiatus was mostly between 20 and 40 mm Table 1. The average distance between the two superolateral sacral crests the base of the triangle was The distance between the right superolateral sacral crest and the sacral apex was The distance between the left superolateral sacral crest and the sacral apex was Despite these mean values, it is more important to know that the distances from the right and left sacral crests to the hiatus were similar in each sacrum.

The angle between the lines formed by the base of the triangle and the sacral hiatus was The anatomical measurements are given in Table 2. Another approach is the 'no turn' technique, which is a new method developed in the Ain-Shams University, Pediatric Surgical Unit by the author. It has a high success rate and can be easily learned and implemented even by junior staff. New technique for caudal epidural block in pediatric patients.

Ain-Shams J Anaesthesiol ;9: It is commonly used to augment general anesthesia and to manage postoperative pain. Effective postoperative pain relief from caudal analgesia has numerous benefits, including earlier ambulation, reduced time spent in a catabolic state, lowered circulating stress hormone levels, and decreased need for postoperative analgesics including narcotics.

Note that turbulence during injection can be more easily visualized when the depth of the ultrasound is adjusted for 2 cm. Besides, repeated ultrasounds have allowed recognition of the sacrococcygeal anatomy in children 7. Review of the literature in ultrasound-guided caudal epidural anesthesia Chen et al.

They used a high-frequency MHz transducer to identify the sacral hiatus. Initially, a transverse ultrasound image of the sacral hiatus was obtained to identify appropriate landmarks. Then, using the longitudinal view, a 21G Tuohy needle was introduced into the caudal epidural space under direct view. Appropriate needle placement was confirmed by fluoroscopy. Further introduction of the needle into the sacral hiatus and caudal epidural space was done under continuous, real-time ultrasound.

However, the tip of the needle could not be visualized by the ultrasound after being inserted in the epidural sacral space due to bone artifacts. Aspiration was the only method used to identify the presence of CSF or blood 5,6. Gross 8 criticized the aforementioned study saying that Chen et al. Thus, although the technique seems promising, Gross 8 suggests that an individual comparison with the loss of resistance technique should be done.

And he also suggested that standardization for technical similarities among operators is necessary to establish the technical superiority of the ultrasound-guided technique. The absence of alternative methods to aspiration to detect blood or CSF in the study by Chen 5 led Yoon et al.

Caudal Epidural Block: An Updated Review of Anatomy and Techniques

After accessing the epidural space, 5 mL of the anesthetic solution were injected while observing the flow with the high-resolution MHz transducer and color Doppler. The injection was defined as successful if the unidirectional flow dominant color of the solution was observed with the Doppler through the epidural space below the sacrococcygeal ligament. No flow could be observed in other directions multiple colors. Correct placement of the medication was confirmed by contrast fluoroscopy.

Caudal anesthesia

In 52 out of 53 patients evaluated the medication was successfully administered in the caudal epidural space with ultrasound guidance. Fluoroscopy of those 52 patients revealed correct placement of the drug in the caudal epidural space in 50 patients.

However, three patients including one with negative Doppler and two with positive Doppler showed contrast outside the epidural space. They found it useful, especially in moderately obese patients or in patients with difficulty to be placed in ventral decubitus. They reported good visualization of landmarks, but they needed a low-frequency transducer MHz in obese patients to achieved adequate penetration 6.

Recently, a retrospective observational study on caudal injection with 83 pediatric patients was conducted. The objective of this study was to compare the accuracy of caudal epidural needle positioning between two confirmatory tests, the "swoosh" test auscultation with a stethoscope in the sacral region during caudal injection of local anesthetic and real-time ultrasound image transversal bidimensional ultrasound and color flow Doppler. The authors concluded that ultrasound is superior to the "swoosh" test as an objective confirmatory technique during caudal anesthesia in children.

They reported that the presence or absence of turbulence on ultrasound during injection of the local anesthetic in the caudal space is a better indicator of successful anesthesia 6,9. However, the lack of studies on the success rate of adequate positioning of the caudal epidural needle in children led to a comparative study between the accuracy of routine needle placement and graduation of ultrasound view regarding the efficacy of the blockade.

In this context, 53 ultrasound-guided anesthesias in children ages months undergoing low abdominal surgery were investigated. The needle was visualized in the caudal epidural space in 45 out of 53 anesthesias. The injection in the caudal epidural space was clearly seen in the 45 blockades in which the needle was visualized. Those blockades were considered successful according to intraoperative vital signs and postoperative nursing criteria.

In five patients the needle was not visualized in the ultrasound, but the injection inside the caudal epidural space was seen.

Caudal Epidural Block: An Updated Review of Anatomy and Techniques

Those anesthesias were considered successful according to the criteria mentioned. In the three patients that neither the needle nor the injection could be visualized, the anesthesia was considered a failure both by intraoperative vital signs and postoperative nursing criteria. According to their report, success was achieved by ultrasound guidance. Caudal anesthesia in this child was initially impossible due to subcutaneous edema of the sacral region secondary to inadequate needle positioning, which hindered the anatomic identification necessary to perform the anesthesia.

Consequently, a transversal ultrasound of the sacrum was performed linear transducer perpendicular to the spinal axis. This allowed prompt identification of the sacral cornua and hiatus, besides marking needle placement on the skin over the sacrococcygeal ligament, midway between both cornua. Afterwards, a few centimeters above the site of the injection, a new image in the transversal plane showed the characteristic turbulence in the caudal space.

The flow was also detected by the Doppler. The absence of changes in vital signs during the surgery, the presence of a partial motor blockade in the lower limbs, and a comfortable stay in the post-anesthetic recovery unit lead to the classification of the anesthesia as successful. It is useful when anesthesia of lumbar and sacral dermatomes is necessary. Caudal epidural anesthesia is the most popular technique of regional anesthesia used in children up to 8 years of age. Above this age, only the relative difficulty in localizing the sacral hiatus limits its use.

However, in adults the technique has been widely used especially for control of chronic pain. Successful caudal anesthesia requires adequate placement of the needle in the epidural space. This happens because the ultrasound allows the identification of sacral anatomy, besides visualizing the injection in the caudal space during the anesthesia. It is a portable, non-invasive technique, making it an attractive tool in the operating room, especially in difficult cases.

Caudal anesthesia

So, lately, several groups have described the use of the ultrasound during caudal anesthesia both in children and adults The sacrum and coccyx are formed by the fusion of eight vertebrae five sacral and three coccygeal. As a result, a natural defect secondary to incomplete fusion in the posterior midline of the inferior portion of S4 and S5 exists. This defect is known as the sacral hiatus, and it is covered by the sacrococcygeal ligament.

The hiatus is limited laterally by the sacral cornua, and its base is formed by the posterior aspect of the sacrum. This represents a challenge during injection of drugs in the caudal epidural space. The literature reports inadvertent intravascular injection in approximately 2. Moreover, intravascular injection is more common in older patients since the epidural venous plexus which as a rule ends in S4 can continue inferiorly.

Once more, the literature stresses the importance of performing caudal epidural injection with real-time imaging exams in order to maximize the results and minimize complications 6. In adults, epidural injections of local anesthetics and corticosteroids have been widely used to promote pain relief in patients with low lumbar disorders.

Those injections can be done using the translaminar, transforaminal, and caudal routes.


The caudal approach to the epidural space has been the preferred route for many anesthetists, since puncture of the dural sac and intrathecal injection of drugs is rare. For this reason, fluoroscopy has been commonly used to confirm placement of the needle. However, radioactive exposure has become the greatest concern of using fluoroscopy. The ultrasound has become advantageous in localizing the sacral hiatus and guiding the needle into the caudal epidural space because it is easy to use, free from radiation, and it can provide continuous, real-time images of the needle without exposure to radiation in both clinical and virtual conditions.

The main disadvantage of this technique is the impossibility to visualize the needle as it becomes deeper, since ultrasound waves cannot penetrate the bone. Thus, it is necessary to verify the presence of CSF before injecting corticosteroids 5. Note that independently of the technique real-time ultrasound is by far a more demanding intervention because a high degree of manual dexterity, hand-eye coordination, and ability to interpret the bidimensional images are necessary.

Before central neuraxial intervention with the ultrasound, required abilities and familiarity with the spinal ultrasound technique, and sonoanatomy of the spine are required. Besides, one should consider patient positioning during the ultrasound.