a 64-year - old man , weighing 47 kg and having a height of 154 cm , was scheduled for a pericardiectomy for treatment of constrictive pericarditis . when he was hospitalized with a two - week history of aggravating dyspnea , he had been placed on outpatient follow - up for pulmonary tuberculosis , previously diagnosed with dyspnea on exertion and pleural effusion . his past medical history included diabetes mellitus diagnosed 20 years ago and stent insertion in the left anterior descending ( lad ) coronary artery eight years ago . preoperative ecg revealed left atrial enlargement , and st depression and flat t - wave on lead ii , iii and v4 - 6 . coronary computerized tomography demonstrated that the lad stent was intact , but there was > 50% narrowing of the left circumflex coronary artery , and pericardial thickening with adhesion to the right atrial and left ventricular lateral walls . echocardiography showed a left ventricular ejection fraction of 73% , and mild pulmonary hypertension with a systolic right ventricular pressure of 38 mmhg . an hour before surgery , premedication was done with i m morphine 3 mg . on arrival , continuous monitoring of ecg lead ii and v5 was initiated , and the radial artery cannulation was done under local anesthesia for pressure monitoring . vital signs before induction of anesthesia were hr 85/min , abp 108/68 mmhg , and spo2 98% . rocuronium 50 mg was administered to facilitate endobronchial intubation with a 35 fr left - sided double - lumen tube . after intubation , lungs were ventilated with a tidal volume of 8 - 10 ml / kg , adjusted to maintain end - tidal co2 within 33 - 38 mmhg . anesthesia was maintained with 1.0 - 1.5% sevoflurane in 60% oxygen in air and continuous infusion of remifentanil at 0.1 - 0.3g / kg / min . after induction of anesthesia , the patient was turned to the head - down position with the head rotated leftward by approximately 60 to facilitate internal jugular catheterization . an 18-g puncture needle was inserted at the conjoined site of both bellies of the scm , and was advanced toward the ipsilateral nipple until free regurgitation of venous , non - pulsatile blood flow was observed . during the first attempt , the puncture needle had to be withdrawn , as the j - tipped guide wire could be advanced < 10 cm . after 5 min of manual compression , jugular venous puncture was retried in the same manner , and non - pulsatile , free - regurgitant blood flow was again obtained . in the second attempt , the j - tipped guide wire was inserted into the vessel without significant resistance , even though it was initially difficult to advance the wire and the puncture needle had to be withdrawn a few millimeters to obtain free regurgitant blood flow . then , a 7-fr double - lumen central venous catheter ( arrow gard blue , arrow international , inc . , usa ) was inserted using the seldinger method and was suture - fixed at 16 cm in the skin after confirming free inflow of fluid . at the end of procedure , the guide wire withdrawn showed no deformations . central venous pressure ( cvp ) was measured to be 20 mmhg with the patient in a supine position and thereafter was maintained within 30 - 40 mmhg in the right semi - lateral decubitus position at approximately 30 during one - lung ventilation for surgery . such a high cvp was considered to be related to the constrictive pericarditis , as the pressure measurement was less than the mean arterial pressure of the radial artery ( 80 - 85 mmhg ) and the waveform was flat without pulsations , being affected by right - side one - ling ventilation and surgical manipulation of the heart . during the catheterization , vital signs were stable with hr 83/min , bp 90 - 100/65 - 68 mmhg , and spo2 99 - 100% . arterial blood gas analysis was done after induction of anesthesia and revealed ph 7.486 , pao2 331 mmhg , and paco2 36.2 mmhg with fio2 0.6 . approximately 50 minutes after the surgery began , the pressure waveform from the central venous catheter changed abruptly into what was seemingly an arterial waveform , with a mean pressure of 61 mmhg , almost same to the mean arterial pressure of 62 mmhg ( fig . 1 ) . simultaneously , blood regurgitated through the fluid line connected to the central venous catheter . even though about 300 ml of fluid had already been administered , arterial blood gas measurement was done on blood withdrawn from the central venous catheter , indicating a pao2 of 438.7 mmhg with a fio2 of 0.6 , confirming that it was arterial blood . 2 ) . fluid infusion was immediately stopped , and the catheter was removed when the surgery was completed . after confirming that there was no bleeding or developing hematoma in the puncture site with > 15 min of compression , the double - lumen tube was replaced with a single - lumen endotracheal tube . thereafter , the patient was transferred to the intensive care unit with the endotracheal tube in situ . extubation was done after seven days of mechanical ventilatory care for tachypnea and co2 retention , and the patient was transferred to the general ward without central venous catheter - related complications on the 10th postoperative day . arterial puncture is most frequently encountered , but rarely results in more serious complications , such as hematoma development compromising airway , thromboembolism causing cerebrovascular accident , arteriovenous fistula or pseudoaneurysm . arterial catheterization can happen after arterial puncture , but the incidence is very low ( < 0.1% ) . obesity , hypotension , reduced hemoglobin , low oxygen saturation or unavailability of ultrasonic guidance are risk factors for arterial catheterization . in healthy patients , arterial puncture is easily recognized by pulsatile regurgitation of bright red blood ; however , in patients with hypoxemia or hypotension , those visual parameters would be unreliable due to a weak pulsation of dark red blood . in contrast , patients with increased cvp , including those with congestive heart failure , tricuspid regurgitation , or constrictive pericarditis , may present with forced venous regurgitation , which can be misinterpreted as arterial puncture . in this case , clinically significant pitfalls on differentiation of arterial puncture are the features of the regurgitant blood flow , including color , pulsation , force , or velocity . as fio2 had been maintained at 0.6 after induction of anesthesia , it was difficult to macroscopically discriminate between arterial and venous blood . also , we already anticipated increased blood regurgitation due to the elevated diastolic pressure caused by restrictive physiology of pericarditis . it would be highly suspicious of an arterial puncture if massive regurgitation of bright red blood with pulsation or large hematoma was observed ; however , in this case , those findings were not definitive . first , overlap between the carotid artery and jugular vein could be increased with leftward head rotation . together with a relatively deep insertion of the puncture needle , such an increased overlapping could facilitate a penetration of the anterior wall of the carotid artery through the jugular vein . .   demonstrated that when the head was maximally rotated leftward without discomfort , an overlap of > 75% was observed in 54% of patients , especially in those with advanced age ( > 60 yr ) and venous dilation . kim et al .   also found that the degree of overlap between the carotid artery and jugular vein increased with leftward head rotation in korean patients . considering the small build of our patient , puncture needle could be inserted relatively deep , and eventually penetrate the anterior wall of the carotid artery after advanced through the jugular vein . and non - deformed guide wire withdrawn could be another evidence of carotid puncture , not subclavian artery . second , multiple attempts at venous puncture are known to increase the incidence of mechanical complications of cvc , reportedly increasing by about 10-fold after at least two unsuccessful attempts even with an experienced physician . the ultrasound - guided method is reported to be helpful to reduce the complications . it is unclear why the pressure waveform abruptly changed 1 hr after the arterial catheterization . non - pulsatile , plain waveform , mimicking venous property despite arterial insertion , might be attributed to kinking of the catheter or partial obstruction of the catheter tip against the vessel wall . some measurement errors in pressure transducer system , such as excessive damping , could result in such a plain arterial waveform . abrupt change in pressure waveform and measurement would be attributed to a sudden release of previously kinked catheter or position shift of catheter due to surgical manipulation of the heart . hwang and kim   reported a case of gradual increase in cvp from 34 - 37 mmhg when the catheter was indwelled , to almost the same to the mean arterial pressure . similar to our case , they confirmed arterial insertion via arterial blood gas measurement because the pressure waveform did not appear to be arterial and they assumed damping to be a primary cause . they accomplished the catheterization at the first attempt , and presented no difficulties during catheterization . proper discrimination between the unmasked arterial and central venous waveforms could be difficult due to atrial fibrillation , which presumably resulted from hypotension during induction in their patient with severe coronary artery disease . unlike their case , we observed the abrupt change of previously plain waveform to arterial waveform ( fig . 3 ) , requiring no comparison of arterial gas measurement with venous blood . recently , percutaneous / intravascular intervention with a hemostatic device was shown to be safe and applicable treatment for arterial trauma . in this case , however , the catheter was removed and then manually compressed . this can sometimes cause bleeding , cerebrovascular accident or pseudoaneurysm , the risk of which , however , is dependent on the catheter size , elapsed time from catheterization , and the site of catheterization . because the arterial catheterization was maintained briefly , no hematoma formation in the aorta was confirmed with tee , and the internal jugular vein could be compressed more easily than the subclavian vein , the removal and compression were judged to be appropriate . the concern was the possibility of surgical field contamination ; the removal 
 and compression were done after the surgery was finished . when visual discrimination between arterial and venous blood regurgitation is unreliable , anesthesiologists should confirm where one punctures using all the available methods one has on the scene , especially after at least two unsuccessful attempts or in patients with advanced age or clinical conditions resulting in jugular venous dilation . to prevent arterial catheterization , one should limit the leftward rotation of the head by < 40 and consider using ultrasound - guided method after more than two unsuccessful attempts .
we present a case of inadvertent arterial insertion of a central venous catheter , identified during a pericardiectomy procedure after observing abrupt changes in pressure waveform and confirmed via arterial blood gas analysis and transesophageal echocardiography . 
 central venous pressure measurement was initially 20 mmhg in supine , and then elevated to 30 - 40 mmhg in right lateral decubitus , presumably resulting from constrictive physiology of pericarditis . 
 the pressure waveforms , however , abruptly changed from a venous to an arterial waveform during surgery . 
 when visual discrimination between arterial and venous blood regurgitation is unreliable , anesthesiologists should confirm that using all the available methods one has on the scene , especially after at least two unsuccessful attempts or in patients with advanced age or clinical conditions resulting in jugular venous dilation . to prevent arterial catheterization 
 , one should limit the leftward rotation of the head by < 40 and consider using ultrasound - guided method after more than two unsuccessful attempts .