The ‘whoosh’ test

Abstract

SummaryWe describe a previously unreported test to confirm accurate needle placement in caudal epidurals. Of 26 patients undergoing caudal epidural, 19 (73%) had correct needle placement as determined by epidurography. AN of these had a positive 'whoosh' test. There were no false positives. Key wordsAnaesthetic techniques, regional; caudal.Epidural injections of local anaesthetic agents and corticosteroids are widely used to provide symptomatic relief in patients suffering from low back disorders. The caudal route, although theoretically safer in that the risk of dural puncture is small, has the disadvantage that needle placement is less certain. We describe a clinical test to confirm the position of the needle in the epidural space, and assess the accuracy of the method using epidurography on a series of patients. MethodsPatients who were suffering from low back pain and sciatica were studied. Any patient having a contraindication to contrast media or radiological investigation was excluded from the study. Blood pressure and pulse measurements were made with the patient supine; they were then placed in the prone position and, under aseptic conditions, the sacral hiatus was palpated and the skin infiltrated with local anaesthetic (lignocaine 1% 2 ml). A 21G needle was inserted through the sacrococcygeal membrane, and aspiration performed to ensure that the needle had not penetrated a blood vessel or the dura. The operator then applied a stethoscope over the thoracolumbar region in the midline and listened as a volume of approximately 2 ml of air was injected. Our hypothesis was that if the needle was truly in the epidural space; then a 'whoosh' heard with the stethoscope upon injection would confirm the passage of air proximally in the epidural space; a positive test. Conversely, a needle position that lay outside the epidural space would not produce such a sound; a negative test.The position of the needle was confirmed by injecting 5 ml of contrast medium (Niopam 300) and taking plain X rays (AP and lateral) to detect the presence of contrast in the epidural space. If the position was confirmed, the therapeutic injection was performed; otherwise the needle was withdrawn and resited. Afterwards the patient was admitted to hospital overnight and routine observations performed. ResultsA total of 26 patients were included in the study ( Table 1). There were seven patients classified clinically as obese; six women (mean weight 81 kg) and one man (weight 117 kg). Of these patients, three had a positive test confirmed by epidurography. The other four patients had needle positions outside the sacral hiatus, confirming the difficulty of needle placement in obese patients. However, instead of a silent 'whoosh' test the operator heard a high pitched crackling sound with the stethoscope and was able to palpate air in the subcutaneous fat. This small series showed the 'whoosh' test to be both specific and sensitive. DiscussionThe caudal route of entry to the epidural space is preferred to the lumbar route by many practitio...

A Comparison of Two Techniques for Ultrasound-guided Caudal Injection: The Influence of the Depth of the Inserted Needle on Caudal Block

“…In our study, the needle insertion procedures were performed under ultrasound guidance, and the needles were successfully inserted through the sacral hiatus at the first attempt in all patients. In fact, the failure rate of the traditional caudal injection technique, preformed blindly, has been reported to reach up to 25% despite the various supporting methods available, such as the "Whoosh test" and nerve stimulation method [ 20 , 21 , 22 ]. The main causes of failure can include: 1) failure to identify the sacral hiatus due to uncertain surface anatomy or anatomical variation, 2) difficulty of inserting the needle through a too narrow sacral hiatus, and 3) impossiblity of advancing the needle into a sacral canal with a small AP diameter.…”

Comparison of analgesic efficacy of caudal dexmedetomidine versus caudal tramadol with ropivacaine in paediatric infraumbilical surgeries: A prospective, randomised, double-blinded clinical study

“…Thereafter, patients were placed in a lateral position and the skin of the back over the sacrum was disinfected using povidone-iodine solution, and under aseptic precautions, single-dose caudal epidural injection was performed using a 25-gauge needle. Needle position was confirmed by the pop sensed during penetration of the sacrococcygeal ligament, which was followed by the whoosh test[7] using 0.5 ml of air. After negative aspiration of blood or cerebrospinal fluid, caudal medication was given as per the group assigned.…”

Caudal Epidural Block: An Updated Review of Anatomy and Techniques

“…A subjective feeling of “give” or loss of resistance suggests piercing the SCL [18] but is associated with a miss rate up to 26% even in experienced hands [5]. The “whoosh test,” performed by auscultation at the thoracolumbar region with a stethoscope while injecting 2 mL of air [19], has a sensitivity of 80% and a specificity of 60% in adults [20]. Palpating for subcutaneous bulging on rapid injection of 5 mL air or saline had a positive predictive value of 83% and a negative predictive value of 44% [4].…”