Datta
REPLY anaesthesiologist, who was blinded to which group the patient was in, made the assessment. The authors have mentioned that fluoroscopic guidance is the gold standard. “Swoosh” test was used as a confirmatory test. The operator’s clinical impression of successful placement was recorded based on a loss of resistance on piercing the sacrococcygeal membrane, an approximate angle of 45° between the cannula and patient’s skin, ease of injection of the local anaesthetic and lack of subcutaneous swelling at the injection site. In its original description, only 26 patients were studied for the “whoosh” test, although the test was positive in all patients with a correctly placed needle as identified by epidurography.2 Sensitivity and specificity were not described. Eastwood et al3 reported their findings in 131 adults receiving a caudal steroid injection and found the “whoosh” test to have a sensitivity of 94% but a specificity of only 20% with a significant number of false positive results. In their study in adults using an air “whoosh” test, Chan et al4 found a positive predictive value of 78% for a given insertion. Orme et al5 showed a positive “swoosh” test is a highly sensitive predictor of a successful caudal anaesthetic, with a positive predictive value of 100%. They had a number of false negatives but nevertheless the overall sensitivity of the test was above 90%. In particular, they had no false positive results, a highly desirable characteristic for a diagnostic test, giving a specificity of 100%. The authors have had good results even in lumbar spondylosis. Breaking the cycle of pain could be an explanation. And yes, the patient has to be explained the evidence for and against ESI before treatment.
The authors thank the reader for his keen interest and sagacious comments about the article “A randomized clinical trial of three different steroids agents for treatment of LBA through the caudal route” (MJAFI 2011;67:25–33). The authors acknowledge that the population under study was an extremely heterogeneous population as regards age and BMI. The homogeneity in this trial was the symptom of LBA and the trial showed that ESI are effective in a wide range of age and BMI. The significant male predominance was a reflection of our service and ex-serviceman out patients department (OPD) in a service hospital. It is also agreed that there are a large number of confounders that may affect LBA and the outcome of a treatment strategy such as employment status at the time of presentation, nature of employment, large number of previous interventions for LBA, the psychological profile of the patient, etc. These increase the variance of the measurements of the dependent variable and Bonferroni correction needs to be applied. In this case the dependant variable was restricted to Rolland Morris questionnaire before and after a caudal epidural steroid. Since the various confounders were within the subject design, there is a natural lower risk of introducing bias as the same subject was tested in each case. Of course, anything could happen to the subject between measurements (e.g. exercise and use of NSAIDs), could influence the second measurement. Exercise therapy, focusing on strengthening and stabilising the core muscle groups of the abdomen and back, does appear to produce small improvements in pain and functioning in patients with chronic low back pain. However, only six of the 43 studies included in a Cochrane review were able to demonstrate clinically important and statistically significant differences between intervention and control groups.1 Exercise, however, gives a feeling of “control” to the patient and a sense of well-being. Moreover, only patients with some pain relief are able to exercise. Hence, it was allowed in the study design. The number of NSAIDs tablets taken was recorded but only as an observation, without any correction applied. Counter balancing of the confounders was not possible as this was a “before and after” type of trial to see whether or not caudal epidural steroid have an effect. We tried to control the spread of values of main confounding variables in each group but this obviously gets difficult if there are more than two confounding variables and the study is truly random. Therefore, this trial was not completely immune to the effect of confounding variables. The authors restricted the aim to demonstrate the efficacy of ESIs in LBA whatever may be the aetiology. The risk-benefit ratio in different aetiologies can be evaluated in another study. Regarding administration of the injections, the authors themselves administered the caudal injections. The drug was made by a senior resident as per the study design. Another
MJAFI Vol 67 No 4
REFERENCES 1.
2.
3. 4. 5.
Hayden JA, van Tulder MW, Malmivaara A, Koes BW. Exercise therapy for treatment of non-specific low back pain. Cochrane Database Syst Rev 2005;(3):CD000335. Lewis MPN, Thomas P, Wilson LF, Mulholland RC. The ‘Whoosh’ test. A clinical test to confirm successful needle placement in caudal epidural injections. Anaesthesia 1992;47:57–58. Eastwood D, Williams C, Buchan I. Caudal epidurals: the whoosh test. Anaesthesia 1998;53:305–307. Chan SY, Tay HB, Thomas E. ‘Whoosh’ test as a teaching aid in caudal block. Anaesth Intens Care 1993;21:414–415. Orme RM, Berg SJ. The “swoosh” test – an evaluation of a modified “whoosh” test in children. Br J Anaesth 2003;90:62–65.
Contributed by Col Rashmi Datta Senior Advisor (Anaesthesiology & Critical Care), Army Hospital (R&R), Delhi Cantt. – 10.
396
© 2011, AFMS
REPLY anaesthesiologist, who was blinded to which group the patient was in, made the assessment. The authors have mentioned that fluoroscopic guidance is the gold standard. “Swoosh” test was used as a confirmatory test. The operator’s clinical impression of successful placement was recorded based on a loss of resistance on piercing the sacrococcygeal membrane, an approximate angle of 45° between the cannula and patient’s skin, ease of injection of the local anaesthetic and lack of subcutaneous swelling at the injection site. In its original description, only 26 patients were studied for the “whoosh” test, although the test was positive in all patients with a correctly placed needle as identified by epidurography.2 Sensitivity and specificity were not described. Eastwood et al3 reported their findings in 131 adults receiving a caudal steroid injection and found the “whoosh” test to have a sensitivity of 94% but a specificity of only 20% with a significant number of false positive results. In their study in adults using an air “whoosh” test, Chan et al4 found a positive predictive value of 78% for a given insertion. Orme et al5 showed a positive “swoosh” test is a highly sensitive predictor of a successful caudal anaesthetic, with a positive predictive value of 100%. They had a number of false negatives but nevertheless the overall sensitivity of the test was above 90%. In particular, they had no false positive results, a highly desirable characteristic for a diagnostic test, giving a specificity of 100%. The authors have had good results even in lumbar spondylosis. Breaking the cycle of pain could be an explanation. And yes, the patient has to be explained the evidence for and against ESI before treatment.
The authors thank the reader for his keen interest and sagacious comments about the article “A randomized clinical trial of three different steroids agents for treatment of LBA through the caudal route” (MJAFI 2011;67:25–33). The authors acknowledge that the population under study was an extremely heterogeneous population as regards age and BMI. The homogeneity in this trial was the symptom of LBA and the trial showed that ESI are effective in a wide range of age and BMI. The significant male predominance was a reflection of our service and ex-serviceman out patients department (OPD) in a service hospital. It is also agreed that there are a large number of confounders that may affect LBA and the outcome of a treatment strategy such as employment status at the time of presentation, nature of employment, large number of previous interventions for LBA, the psychological profile of the patient, etc. These increase the variance of the measurements of the dependent variable and Bonferroni correction needs to be applied. In this case the dependant variable was restricted to Rolland Morris questionnaire before and after a caudal epidural steroid. Since the various confounders were within the subject design, there is a natural lower risk of introducing bias as the same subject was tested in each case. Of course, anything could happen to the subject between measurements (e.g. exercise and use of NSAIDs), could influence the second measurement. Exercise therapy, focusing on strengthening and stabilising the core muscle groups of the abdomen and back, does appear to produce small improvements in pain and functioning in patients with chronic low back pain. However, only six of the 43 studies included in a Cochrane review were able to demonstrate clinically important and statistically significant differences between intervention and control groups.1 Exercise, however, gives a feeling of “control” to the patient and a sense of well-being. Moreover, only patients with some pain relief are able to exercise. Hence, it was allowed in the study design. The number of NSAIDs tablets taken was recorded but only as an observation, without any correction applied. Counter balancing of the confounders was not possible as this was a “before and after” type of trial to see whether or not caudal epidural steroid have an effect. We tried to control the spread of values of main confounding variables in each group but this obviously gets difficult if there are more than two confounding variables and the study is truly random. Therefore, this trial was not completely immune to the effect of confounding variables. The authors restricted the aim to demonstrate the efficacy of ESIs in LBA whatever may be the aetiology. The risk-benefit ratio in different aetiologies can be evaluated in another study. Regarding administration of the injections, the authors themselves administered the caudal injections. The drug was made by a senior resident as per the study design. Another
MJAFI Vol 67 No 4
REFERENCES 1.
2.
3. 4. 5.
Hayden JA, van Tulder MW, Malmivaara A, Koes BW. Exercise therapy for treatment of non-specific low back pain. Cochrane Database Syst Rev 2005;(3):CD000335. Lewis MPN, Thomas P, Wilson LF, Mulholland RC. The ‘Whoosh’ test. A clinical test to confirm successful needle placement in caudal epidural injections. Anaesthesia 1992;47:57–58. Eastwood D, Williams C, Buchan I. Caudal epidurals: the whoosh test. Anaesthesia 1998;53:305–307. Chan SY, Tay HB, Thomas E. ‘Whoosh’ test as a teaching aid in caudal block. Anaesth Intens Care 1993;21:414–415. Orme RM, Berg SJ. The “swoosh” test – an evaluation of a modified “whoosh” test in children. Br J Anaesth 2003;90:62–65.
Contributed by Col Rashmi Datta Senior Advisor (Anaesthesiology & Critical Care), Army Hospital (R&R), Delhi Cantt. – 10.
396
© 2011, AFMS
