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Paper text:
a 45-year - old female patient with crps visited the clinic for management of neuropathic pain of the left upper extremity . she had suffered from allodynia and hyperalgesia of the left upper extremity for two years .
we had managed her symptoms with cervical epidural block and thoracic paravertebral block . during this visit
, a left unilateral thoracic paravertebral block at the second thoracic vertebral level was performed in the sitting position with a 22-gauge tuohy needle by the loss of resistance technique .
three hours later , the patient returned to the clinic complaining of left chest pain and mild dyspnea .
stethoscopy of both sides of the thorax revealed slightly decreased breath sounds of respiration on the left .
a curved transducer ( 3 - 5 hz ) was placed on the left anterior chest wall longitudinally on the second intercostal space .
this procedure revealed absence of the lung sliding sign and comet - tail artifact at the pleural line ( fig .
needle thoracotomy was performed in the left second intercostal space on the midclavicular line with an 18 gauge intravenous cannula by ultrasound - guided out - of - plane approach ( fig .
5 ) . after rechecking the cxr , the patient received oxygen therapy for two days to avoid reexpansion of the pneumothorax .
thoracic paravertebral block is the technique of injecting local anesthetics into the paravertebral space containing the thoracic spinal nerves and thoracic sympathetic chain .
this technique can be used for postoperative pain control and for control of chronic pain such as that resulting from crps and post - herpetic neuralgia , as well as pain caused by rib fracture .
the standard technique of paravertebral space location is by loss of resistance to air or saline and fluoroscopy - guided block or ultrasound - guided block can be performed . in this case
, we performed the paravertebral block by the blind technique , because our clinic does not allow for the performance of every paravertebral block with fluoroscopic or ultrasound guidance .
it is recommended that physicians to use fluoroscopy - guided block or ultrasound - guided block , whenever possible .
paravertebral block can result in complications ; hypotension occurs in 4.6% of cases , vascular puncture in 3.8% , pleural puncture in 1.1% and pneumothorax in 0.5% .
the frequency of pneumothorax after paravertebral block is relatively lower than that of other complications .
however , as pneumothorax can develop into a medical emergency , such as respiratory distress , early diagnosis is very important for patients and physicians .
various procedure , such as thoracic paravertebral block , central intravenous catheterization , thoracentesis , and lung biopsies , can result in iatrogenic pneumothorax .
the standard diagnostic tool for pneumothorax is ct , but cxr is commonly used to diagnose pneumothorax and to exclude other diseases .
however , radiologic examination , such as ct or cxr , can require time to perform , and carries the risk of radiation exposure . in many pain clinics ,
the increase in the use of ultrasound has given physicians an excellent diagnostic technique , with the ease of use of ultrasound machines and the easy interpretability of ultrasound image .
ultrasound examination of the chest is non - invasive , economical and free of radiation , and the ultrasound machine is usually placed at the bedside , allowing for its immediate employment .
there are many clinical indications for thoracic ultrasonography , with pleural effusion the most common .
ultrasound examination to detect pneumothorax should be performed in an organized fashion . with patients in the supine position ,
the ultrasound probe is placed on the anterior chest wall longitudinally to find the ribs and pleural line . in the longitudinal view
, the location of the ribs makes it possible to detect the pleural line , while in the transverse view , the ribs and pleural line are not seen in the image .
the pleural line is composed of the visceral pleura , parietal pleura and a small amount of interpleural fluid . in normal subjects , it is difficult to differentiate between the two pleural layers in an ultrasound image .
a hyperechoic pleural line located between and below two ribs is either the parietal or visceral layers .
the parietal pleura normally slides on the visceral pleura , in a manner synchronized with respiration ( sliding sign ) .
the lung sliding sign is always correlated with the normal lung , but absence of the lung sliding sign , while suggestive , is not sufficient to confirm pneumothorax . in a subject with pneumothorax
, the pleural line represents only the parietal pleura , because air collection in the interpleural space prevents visualization of the visceral pleura . during ultrasound examination , two types of artifacts from the pleural line can be observed .
one type is a roughly horizontal hyperechoic pleural line ( horizontal artifact ) and the other type is a roughly vertical hyperechoic reverberation artifact from the pleural line to the edge of the screen ( comet - tail artifact ) .
the horizontal artifact is a brightly echogenic line between the rib shadows and is made by air as a static barrier to ultrasound .
the comet - tail artifact is sign of interstitial lung disease , and also signifies lung parenchyma that is absent of interposed air .
horizontal artifacts with the lung sliding sign represent the normal lung pattern , while horizontal artifacts without the lung sliding sign are a sensitive sign of pneumothorax , and there are reports that the presence of the lung sliding sign and comet - tail sign is indicative of absence of pneumothorax . in the present case ,
pneumothorax was diagnosed easily by cxr and was confirmed by thoracic ultrasonography . in the first ultrasound examination , we could not detect the lung sliding sign or comet - tail sign , but only the horizontal artifact ( fig .
, we were able to detect the lung sliding sign and comet - tail artifact ( fig .
thoracic ultrasonography is more sensitive than supine chest radiography and is as sensitive as ct in the detection of traumatic pneumothorax .
managements of pneumothorax includes observation , simple aspiration , or tube thoracotomy , depending on the size of the pneumothorax , symptoms , presence of continued air leak , and evidence of a tension pneumothorax .
this case was successfully simply treated with observation , oxygen inhalation , and simple aspiration with a specially invented mini - tube device and subclavian catheter on an outpatient basis .
laub et al .   reported that treatment of iatrogenic pneumothorax with a small caliber chest tube with a 2 mm diameter is less painful and less traumatic than large tube thoracotomy .
large intercostal tube drainage has been replaced by smaller tubes and simple aspiration for iatrogenic pneumothorax , so hospitalization is not necessary in many cases .
a small - diameter cannula also can be easily placed with ultrasound . in the present case ,
the patient was managed by simple needle aspiration using an 18-gauge small cannula , not a large large - bore chest tube . in the case
discussed here , the method of ultrasound - guided aspiration of pneumothorax is as follows . with the patient in the supine position ,
a curved transducer ( 3 - 5 hz ) was placed on the left anterior chest wall longitudinally on the second intercostal space to find the ribs and pleural line .
needle thoracotomy was then performed by an ultrasound - guided out - of - plane approach .
an in - plane approach could be used to approach the interpleural space , but the length of our angiocatheter was too short to each the interpleural space . with a longer angiocatheter or tube , we could perform the needle thoracotomy by an in - plane approach . during the ultrasound - guided needle aspiration , it was difficult to find the needle tip when it was advanced into air within the interpleural space
. therefore , it is important to avoid advancing the needle into the interpleural space and to keep the needle tip just below the parietal pleura to avoid lung injury .
we aspirated the air within the interpleural space with a 50 ml syringe and 3-way valve to prevent reentry of the air into interpleural space .
when thoracic ultrasonography showed the lung - sliding sign and comet - tail artifact , we discontinued the aspiration .
because the wound was so small , there was no need for sutures to prevent reexpansion of the pneumothorax . to reduce the occurrence of pneumothorax during thoracic paravertebral block
when pneumothorax occur during paravertebral block , practitioner who is near an ultrasound machine , should scan the anterior chest wall and try to find the lung sliding sign or comet - tail sign to rule out pneumothorax .
ultrasound can also be an excellent practical tool to allow aspiration of interpleural air without vascular injury , nerve injury or lung parenchymal injury . during aspiration ,
use of a small caliber cannula is recommended to aspirate the interpleural air to treat pneumothorax on an outpatient basis and to reduce hospitalization time .
thoracic paravertebral block is performed for the treatment of patients with chronic pain , such as complex regional pain syndrome ( crps ) and post - herpetic neuralgia . 
 thoracic paravertebral block can result in iatrogenic pneumothorax . because pneumothorax can develop into medical emergencies and needle aspiration or chest tube placement may be needed 
 , early diagnosis is very important . 
 recently , thoracic ultrasonography has begun to be used to diagnose pneumothorax . 
 in addition , ultrasound - guided aspiration can be an accurate and safe technique for treatment of pneumothorax , as the needle position can be followed in real time . 
 we report a case of iatrogenic pneumothorax following thoracic paravertebral block for the treatment of chronic pain due to crps , treated successfully by ultrasound - guided aspiration .