Vishal Uppal

Intracatheter air in continuous thoracic paravertebral block: distraction or assistance?

To the Editor, Non-neuraxial techniques, such as bilateral paravertebral blocks (PVB), are increasingly offered for abdominal surgeries where identification of the catheter tip improves safety and efficacy. A variety of techniques (e.g., fluid, air, or colour Doppler have been described to locate the needle or catheter tip, each with its own advantages and drawbacks. We describe a case of bilateral PVB wherein intracatheter air was visualized on initial injection under ultrasound, localizing the catheter tip. A 46-yr-old female patient (weight, 66 kg; height, 158 cm) scheduled for laparotomy consented to bilateral PVB for postoperative analgesia. After positioning the patient prone, a pre-procedural scan with a linear probe (7-13 MHz, SonoSite M-turbo, Bothel, WA, USA) identified the T8-9 paravertebral space (PVS) bilaterally. Using sterile precautions, continuous PVB was performed using Sonocurl catheters (Sonolong, Sonocurl 100, Pajunk Medizintechnologie GmbH, Geisingen, Germany). The blocks were performed using an intercostal approach with the needle inserted in plane from lateral to medial. The needle tip was identified in the PVS by observing the displacement of pleura with injection of 3 mL of 5% dextrose. The catheter was introduced without real-time ultrasound guidance until it extended 4 cm into the space. Next, 0.5% ropivacaine 20 mL was injected in small aliquots while observing for drug delivery under ultrasound. At the start of injection, we observed air inside the catheter being displaced, confirming catheter tip location within the PVS (Figure, Panels A and B). We further confirmed drug delivery using colour Doppler and pleural displacement. A postoperative chest x-ray also showed the catheter tip in the paravertebral area on magnification (Figure, Panel C). Air used as a contrast to identify the catheter tip is well described for extremity nerve blocks, but such descriptions are uncommon for truncal blocks. Hydro location is useful when the surrounding tissue, i.e., nerves and fascia, are hyperechoic or isoechoic, giving a clear contrast for the fluid, but PVS appears hypoechoic. Hence, liquids may not provide the required discriminative characteristics to locate the catheter tip. Although air is hypoechoic, its deposition around the catheter tip can provide better surrounding contrast to make the tip visible. We deliberately avoided injecting additional air to prevent difficulties in making further block attempts, if needed. While radiological confirmation of catheter tip location is common practice, confirming the catheter tip location while performing the block can avoid unnecessary exposure to radiation. Further studies are needed to evaluate the utility of this technique. There is no foolproof method to identify the catheter tip in the PVS, especially with interference from pleural movements with colour Doppler. Clinicians often have to rely on pleural displacement resulting from injection of a drug. Use of the sonocurl pigtail catheter likely allowed the catheter to remain in the intercostal space once it was inserted, thus facilitating insonation of the catheter tip. In summary, there are multiple recognized techniques to locate the position of the catheter tip for continuous PVB, and intracatheter air may serve as an additional tool for this purpose. Electronic supplementary material The online version of this article (doi:10.1007/s12630-013-9969-8) contains supplementary material, which is available to authorized users.

Single-Injection Versus Multiple-Injection Technique of Ultrasound-Guided Paravertebral Blocks: A Randomized Controlled Study Comparing Dermatomal Spread.

Background and Objectives The objective of this study was to investigate the extent of dermatomal spread following an ultrasound-guided thoracic paravertebral block (PVB) when equal volumes of local anesthetic are injected at 1 versus 5 vertebral levels. Methods Seventy patients undergoing a unilateral mastectomy were randomized to receive either single or multiple injections of a PVB under real-time ultrasound guidance using a parasagittal approach. The patients in the single-injection group received a PVB at T3–T4 level with 25 mL of 0.5% ropivacaine and 4 subcutaneous sham injections. Patients in the multiple-injection group received 5 injections of a PVB from T1 to T5 level. Five milliliters of 0.5% ropivacaine was injected at each level. Evaluation of the sensory block was carried out 20 minutes following the completion of the PVB. Results The median (interquartile range) dermatomal spread was not significantly different for the single-injection group (5 [4-6]) compared with the multiple-injection group (5 [5-6]), with a median difference of 0 segments (95% confidence interval, −1 to 0 segments; P = 0.22). The median time to performance of the single-injection PVB was shorter compared with the multiple-injection group (10 minutes), with a mean difference of −4 minutes (95% confidence interval, −6 to −3 minutes; P < 0.001). Conclusions An ultrasound-guided single-injection PVB provides equivalent dermatomal spread and duration of analgesia compared with a multiple-injection PVB. The single-injection technique takes less time to perform and hence may be preferred over a multiple-injection technique. The trial was registered prospectively at ClinicalTrials.gov (NCT02852421) on July 15, 2016.

Hyperbaric Versus Isobaric Bupivacaine for Spinal Anesthesia: Systematic Review and Meta-analysis for Adult Patients Undergoing Noncesarean Delivery Surgery

BACKGROUND: It is widely believed that the choice between isobaric bupivacaine and hyperbaric bupivacaine formulations alters the block characteristics for the conduct of surgery under spinal anesthesia. The aim of this study was to systematically review the comparative evidence regarding the effectiveness and safety of the 2 formulations when used for spinal anesthesia for adult noncesarean delivery surgery. METHODS: Key electronic databases were searched for randomized controlled trials, excluding cesarean delivery surgeries under spinal anesthesia, without any language or date restrictions. The primary outcome measure for this review was the failure of spinal anesthesia. Two independent reviewers selected the studies and extracted the data. Results were expressed as relative risk (RR) or mean differences (MDs) with 95% confidence intervals (CIs). RESULTS: Seven hundred fifty-one studies were identified between 1946 and 2016. After screening, there were 16 randomized controlled clinical trials, including 724 participants, that provided data for the meta-analysis. The methodological reporting of most studies was poor, and appropriate judgment of their individual risk of bias elements was not possible. There was no difference between the 2 drugs regarding the need for conversion to general anesthesia (RR, 0.60; 95% CI, 0.08–4.41; P = .62; I2 = 0%), incidence of hypotension (RR, 1.15; 95% CI, 0.69–1.92; P = .58; I2 = 0%), nausea/vomiting (RR, 0.29; 95% CI, 0.06–1.32; P = .11; I2 = 7%), or onset of sensory block (MD = 1.7 minutes; 95% CI, −3.5 to 0.1; P = .07; I2 = 0%). The onset of motor block (MD = 4.6 minutes; 95% CI, 7.5–1.7; P = .002; I2 = 78%) was significantly faster with hyperbaric bupivacaine. Conversely, the duration of motor (MD = 45.2 minutes; 95% CI, 66.3–24.2; P < .001; I2 = 87%) and sensory (MD = 29.4 minutes; 95% CI, 15.5–43.3; P < .001; I2 = 73%) block was longer with isobaric bupivacaine. CONCLUSIONS: Both hyperbaric bupivacaine and isobaric bupivacaine provided effective anesthesia with no difference in the failure rate or adverse effects. The hyperbaric formulation allows for a relatively rapid motor block onset, with shorter duration of motor and sensory block. The isobaric formulation has a slower onset and provides a longer duration of both sensory and motor block. Nevertheless, the small sample size and high heterogeneity involving these outcomes suggest that all the results should be treated with caution.