Thermography: a noninvasive assessment of pediatric thoracic epidural blocks

Infrared thermography to assess dermatomal levels of labor epidural analgesia with 1 mg/mL ropivacaine plus 0.5 µg/mL sufentanil: a prospective cohort study

BACKGROUND

Assessment of the effectiveness of obstetric epidural analgesia may be difficult and techniques for objective assessment of epidural spread of local anesthetic would be useful. In this prospective cohort study we assessed whether obstetric epidural analgesia from a low concentration of ropivacaine led to significant change in cutaneous temperature, related to sympathetic block detected by infrared thermography, at dermatomes C4, T4, T10, L2 and L5.

METHODS

Women in spontaneous labor who requested epidural analgesia were consecutively recruited. Epidural analgesia was induced with a bolus of 10-15 mL of ropivacaine 1 mg/mL and sufentanil 0.5 µg/mL, followed by continuous epidural infusion. Skin temperature was measured using thermography before and 20 min after the epidural bolus. The verbal pain score using a numeric rating scale was recorded before and 60 min after the epidural bolus. The upper sensory block to cold sensation was tested 30 and 60 min after the bolus by a physician blinded to the skin temperature. Failed epidural analgesia was defined as verbal pain score >3 at 60 min.

RESULTS

Fifty-three parturients were included and analyzed. We found a significant increase in skin temperatures measured at T4, T10, L2 and L5 dermatomes, but not at C4, and a significant difference in the change in skin temperature at T10 between failed (n=3) and successful (n=50) epidural analgesia.

CONCLUSIONS

These results suggest that infrared thermography might be useful for the early diagnosis of successful obstetric epidural analgesia.

Thermographic skin temperature measurement compared with cold sensation in predicting the efficacy and distribution of epidural anesthesia

Due to the high rates of epidural failure (3-32%), novel techniques are required to objectively assess the successfulness of an epidural block. In this study we therefore investigated whether thermographic temperature measurements have a higher predictive value for a successful epidural block when compared to the cold sensation test as gold standard. Epidural anesthesia was induced in 61 patients undergoing elective abdominal, thoracic or orthopedic surgery. A thermographic picture was recorded at 5, 10 and 15 min following epidural anesthesia induction. After 15 min a cold sensation test was performed. Epidural anesthesia is associated with a decrease in skin temperature. Thermography predicts a successful epidural block with a sensitivity of 54% and a PPV of 92% and a specificity of 67% and a NPV of 17%. The cold sensation test shows a higher sensitivity and PPV than thermography (97 and 93%), but a lower specificity and NPV than thermography (25 and 50%). Thermographic temperature measurements can be used as an additional and objective method for the assessment of the effectiveness of an epidural block next to the cold sensation test, but have a low sensitivity and negative predictive value. The local decrease in temperature as observed in our study during epidural anesthesia is mainly attributed to a core-to-peripheral redistribution of body heat and vasodilation.

Thermography as an early predictive measurement for evaluating epidural and femoral-sciatic block success in dogs

OBJECTIVE

To evaluate skin temperature increase as an early predictive measure for evaluating epidural and femoral-sciatic block success in dogs.

STUDY DESIGN

Prospective clinical trial.

ANIMALS

A total of 29 dogs undergoing orthopaedic surgery on one hindlimb.

METHODS

Dogs were anaesthetized and placed into lateral recumbency with the affected limb uppermost and the coat was clipped. Baseline infrared thermographic images (T0) of the affected limb, of the paw pad of the affected leg and of the ipsilateral paw pad were taken. Subsequently, dogs were administered either an epidural (EPI; n=11) or a femoral-sciatic block (FS; n=18) using bupivacaine 1 mg kg^-1. Then, 2 minutes after placement of the block, thermographic images were obtained every 3 minutes for a total of four measurements (T1-T4) and surgery was commenced. Rescue analgesia consisting of fentanyl 1 μg kg^-1 was administered if needed. A regional block was considered successful if the dose of fentanyl administered was less than the lower 95% confidence interval of the geometric mean of the total fentanyl used in each group. A ≥ 1 °C increase of skin temperature was considered as the minimum increase required for detection of a successful block.

RESULTS

A total of 12 out of 18 blocks in the FS and eight of 11 in the EPI group were considered successful based on fentanyl consumption. Out of these, only four of 12 in the FS and one of eight in the EPI group developed an increase in temperature of ≥ 1 °C. Contrarily, four of six of the nonsuccessful cases in the FS and three of three in the EPI group developed an increase in temperature of ≥ 1 °C.

CONCLUSIONS AND CLINICAL RELEVANCE

Contrary to reports in humans, thermography did not indicate regional block success prior to surgery in dogs. However further studies under more controlled conditions are needed to determine whether thermography can be used to indicate failure of regional blockade.

Infrared thermography in paediatrics: a narrative review of clinical use

BACKGROUND

Infrared thermography (IRT) has been used in adult medicine for decades, but recent improvements in quality of imaging and increasing computer processing power have allowed for a diversification of clinical applications. The specific usage of IRT in a paediatric population has not been widely explored, so this article aims to summarise the available literature in this area. IRT involves the non-contact, accurate measurement of skin surface temperature to identify temperature changes suggesting disease. IRT could well have unique applications in paediatric medicine.

METHODS

Electronic searches were performed independently by two authors, using the databases of MEDLINE (via Web of Science), the Cochrane Library, CINAHL (EBSCO) and Scopus, including articles published from 1990 to July 2016. The search strategy that was used aimed to include articles that covered the topics of IRT and children, including studies with participants 18 years old or younger. Articles were screened by title and abstract by two authors. Meta-analysis was not performed due to the marked heterogeneity in applications, study design and outcomes: this is a narrative summary of the available literature.

RESULTS

IRT has been shown to be an effective additional diagnostic tool in a number of different paediatric specialties, namely in fracture screening, burns assessment and neonatal monitoring. Small measurable skin temperature changes can effectively add to the clinical picture, while computer-tracking systems can be reliably used to focus investigations on particular areas of the body.

CONCLUSION

Throughout this review of the available literature, there has been a general consensus that this non-invasive, non-irradiating and relatively inexpensive technology may well have a place in the management of paediatric patients in the future.