Infraclavicular subclavian venous catheterization has various benefits such as patients’ comfort, a lower infection rate, and a lower risk of catheter-related thrombosis compared with other central venous catheterization sites such as femoral or internal jugular vein.1–4 However, this approach can produce some serious complications such as arterial puncture, hemothorax, or pneumothorax. Compared with the internal jugular approach, the subclavian approach is more likely to be complicated by pneumothorax.1,5
Lung deflation method has been used based on the unevidenced belief that it allows the lung apex to move downward and increases the distance from the subclavian vein (SCV) to the pleura. However, prolonged lung deflation can cause complications such as hypoxemia, atelectasis, and instability of vital signs in anesthetized patients, which may limit the duration of procedures and risk the patient safety. In practice, maintenance or interruption of mechanical ventilation during infraclavicular subclavian catheterization is solely at the discretion of clinicians without clear evidence.
Some recent studies have revealed that lung deflation has no effect on the distance between the SCV and the pleura or on the cross-sectional area of the SCV.6,7 Those results raised issues over the concerns about the possibility of pneumothorax while maintaining mechanical ventilation during the subclavian approach.
To date, no randomized controlled study has been performed with regard to the influence of mechanical ventilation on the incidence of pneumothorax. Thus, we hypothesized that, during infraclavicular subclavian venous catheterization, maintenance of mechanical ventilation would not be inferior to interruption of mechanical ventilation with regard to the incidence of pneumothorax. The purpose of this study was to assess the influence of mechanical ventilation on the incidence of pneumothorax during infraclavicular subclavian venous catheterization.
This prospective, single-blind, randomized study was approved by the IRB of Seoul National University Hospital (Ref: 1301-066-459) and registered at ClinicalTrials.gov (NCT01815801) before enrollment. After obtaining written informed consent from each patient, we enrolled 334 patients who underwent neurosurgery requiring subclavian venous catheterization between May 2013 and April 2014.
Patients with infection over the skin puncture site, history of the clavicle or shoulder fracture, history of neck, breast, or thoracic surgery, anatomical abnormality of the clavicle or chest wall, diaphragmatic dysfunction, or history of chronic obstructive pulmonary disease or pneumothorax were excluded. Patients were randomly assigned to 2 groups using a computer-generated random number table: those who underwent right subclavian venous catheterization with the patients’ lungs under mechanical ventilation (ventilation group, n = 167) and without mechanical ventilation (deflation group, n = 167).
After induction of general anesthesia and tracheal intubation, patients were placed in the supine position with their shoulders and head in the neutral position without shoulder retraction8 and without pulling their arms.9 Patients were mechanically ventilated by using volume control mode with a tidal volume of 8 mL/kg and inspiration/expiration ratio of 1:2. The respiratory rate was adjusted to maintain the end-tidal CO2 level between 35 and 45 mm Hg. PEEP was not used throughout the procedure. In the ventilation group, catheterization was performed without interruption of mechanical ventilation. In the deflation group, catheterization was performed with mechanical ventilation interrupted, and mechanical ventilation was resumed after placement of catheters. If patients’ Spo2 values went below 95%, the procedures were temporarily suspended just for a few times of manual ventilation with 100% O2.
Right infraclavicular subclavian venous catheterization was performed by 1 of the 3 preassigned, experienced anesthetists who had performed >100 infraclavicular subclavian venous catheterizations to minimize interobserver bias of catheterization.1 A modified Seldinger technique with a 20-cm-long double-lumen central venous catheter (Arrow International Inc., Reading, PA) was used without ultrasound guidance in the same manner as our previous study.8,9
After sterile preparation, the skin was punctured 1 cm lateral and inferior to the midclavicular line below the clavicle. The puncture needle with the bevel up was directed toward the suprasternal notch and advanced until it came into contact with the bony surface of the clavicle. Then, the needle was withdrawn slightly and readvanced beneath the clavicle toward the sternal notch with gentle suction applied to the syringe. If a regurgitation of venous blood into the syringe was not achieved, the needle was withdrawn slowly to the subcutaneous tissue with a continuous negative pressure within the syringe. When the venous puncture failed on the first attempt, the needle was directed toward a more cephalad point than the suprasternal notch and advanced as in the first attempt. If this second attempt failed, the needle was angled toward the caudad or cephalad direction at the discretion of the anesthetist. After 3 failed attempts of the first anesthetist, the second anesthetist performed the procedure up to 3 times in the same manner as the first anesthetist. The number of attempts was recorded. If the second investigator also failed, the internal jugular venous catheterization was performed.
When venous puncture was successful, a guidewire was passed into the vein through the puncture needle with its J-tip of the guidewire directed downward, and the needle and syringe were removed. After dilation of the subcutaneous tissue with a dilator over the guidewire, the central venous catheter was advanced. Successful intravascular placement of the catheter was confirmed by the aspiration of venous blood through both catheter lumens and by monitoring the central venous pressure via a fluid-filled pressure transducer system. Subjective difficulties throughout the procedure were evaluated subjectively by the assigned anesthetists on a 4-level scale: none, mild, moderate, or severe.
In this study, we recorded the incidence of oxygen saturation drop below 95% when Spo2 decreased below 95% on a patient monitor. In such a case, the procedure was paused temporarily and a few times of manual ventilation was applied with 100% O2 to prevent further oxygen desaturation.
Failure of the subclavian venous catheterization was defined as both the first and the second anesthetists having failed to insert the catheter into the SCV on each of 3 attempts, or arterial puncture or air aspiration was identified within the syringe during the procedure. If a failure occurred, sufficient pressure was applied to control bleeding at least for 5 minutes.
Anteroposterior chest radiographs were taken immediately after surgery and 1 day later in all patients to check the location of the catheter tip and any potential complications such as pneumothorax or hemothorax. Misplacement of the catheter tip was defined as the catheter tip located in the ipsilateral internal jugular vein or contralateral SCV.
The primary end point was the incidence of pneumothorax after infraclavicular subclavian venous catheterization. Sample size was calculated using the PASS software (ver. 11.0; NCSS, Kaysville, UT). Previous studies showed that the incidence of pneumothorax was 1.1% to 3.1%.1,9,10 To obtain 80% statistical power with an αof 0.05, with a noninferiority margin of 3%, 150 patients were needed in each group. Although the noninferiority margin is usually set at 5% in clinical situations, we set the noninferiority margin at 3% based on the clinical judgment that the incidence of pneumothorax is known to be extremely low. Considered a 10% dropout, we estimated that 167 patients were needed in each group.
Data were presented as means ± SD or numbers of patients (%). The SPSS software (version 21.0; SPSS Inc, Chicago, IL) was used for the analysis. A noninferiority analysis was performed to determine whether maintenance of mechanical ventilation was inferior to the deflated lung with regard to the primary end point of the incidence of pneumothorax. A 2-sided 90% confidence interval for the incidence difference (ie, incidence of pneumothorax in the deflation group—incidence of pneumothorax in the ventilation group) was calculated using an exact method,11 and the lower limit was compared with −0.03, a preassigned noninferiority margin. If the lower bound of the 2-sided 90% confidence interval is higher than −0.03, we can reject the inferiority of the ventilation group over the deflation group.
The χ2 test or Fisher exact test was performed to compare the incidence of arterial puncture, hemothorax, incidence of subclavian venous catheterization success and primary venous puncturing, oxygen saturation drop below 95% during catheterization, subjective difficulties, and misplacement of the catheter tip. The independent t test was used to compare the mean age, weight, height, body mass index values, and the number of attempts. A P value of <.05 was considered to indicate statistical significance.
During catheterization, a mild form of bronchospasm, as diagnosed by capnographic waveforms and high peak inspiratory pressure, occurred in 2 patients of the ventilation group. After further exclusion of these 2 patients, a total of 332 patients were enrolled: 165 patients in the ventilation group and 167 patients in the deflation group (Figure).
Patients’ characteristics were comparable between 2 groups except for the sex difference (Table 1), but there were no significant differences in the total mechanical complications (2.7% vs 3.3%, P = .515) or success rate of catheterization between the male and the female (99.3% vs 97.7%, P = .104). The incidence of major complications was similar between 2 groups (Table 2). Neither pneumothorax nor hemothorax occurred in the ventilation group, but pneumothorax was observed in 1 patient of the deflation group (0% vs 0.6%). The incidence of pneumothorax in the deflation group was 0.6% higher than that in the ventilation group and the 2-sided 90% confidence interval for the difference was (−1.29% to 3.44%). Because the lower bound for the 2-sided 90% confidence interval, −1.29%, was higher than the predefined noninferiority margin of −3%, the inferiority of the ventilation group over the deflation group was rejected at the .05 level of significance. This result met the prespecified criterion for declaring noninferiority. Arterial puncture occurred in 2 patients of each group, respectively. The rates of catheter misplacement were 3.6% (6/161) in the ventilation group and 2.4% (4/164) in the deflation group.
There was no difference in the success rate of subclavian venous catheterization between 2 groups (Table 3). The oxygen saturation dropped below 95% in 9 patients in the deflation group, while none in the ventilation group (5.4% vs 0%, P = .007).
This prospective randomized study showed that maintenance of mechanical ventilation was not inferior to the lung deflation during right infraclavicular subclavian venous catheterization in terms of the incidence of pneumothorax. Interruption of lung ventilation during subclavian venous catheterization may have been used based on the nonevidenced presumption that, in the deflated lung, the distance between the SCV and the lung could be increased decreasing the possibility of pneumothorax. However, any evidence supporting the necessity of lung deflation is lacking.
In recent sonographic studies, lung deflation did not extend the distance between the SCV and the pleura, which indirectly suggests that lung deflation is not likely to prevent pneumothorax during SCV catheterization.6,7 Another sonographic study12 showed that lung deflation did not cause caudal movement of lung apex for the infraclavicular approach in infants. Although the abovementioned sonographic studies were not designed to evaluate clinical outcomes, those results raised issues over whether lung deflation decreases the possibility of pneumothorax during the subclavian approach.
Pneumothorax is one of the severe potential complications of subclavian venous catheterization with a reported incidence of 1.1% to 3.1%.1,9,10 The incidence was higher with the number of attempts increased, large bore catheters used, or inexperienced practitioners.13–17 The investigators of this study were board-certified, experienced anesthesiologists, and used a double-lumen central venous catheter in all procedures. Furthermore, the number of attempts was limited up to 3 times for each practitioner. All these factors may explain the relatively lower incidence of the pneumothorax during this study.
Lung volumes are affected by several factors such as age, height, and body mass index.18–20 However, because of the prospective randomized controlled study design, these factors did not show any difference between the 2 groups. In spontaneous breathing adults, the cross-sectional area of the SCV increases significantly at end-expiration when compared with end-inspiration.6 Contrarily, in mechanically ventilated subjects, the cross-sectional area of the SCV has not been shown to be increased after lung deflation.7 Because both groups did not show any difference in the success rate of catheterization in this study, we speculate that the cross-sectional area of the SCV might not be affected greatly regardless of lung deflation.
Central venous catheterizations are commonly performed on patients under mechanical ventilation in both intensive care units and operating theater. If the duration of lung deflation is prolonged, there would be a higher possibility of hypoxemic events irrespective of the fact that 100% oxygen was delivered through endotracheal tube before cessation of ventilation. Because of the oxygen saturation drop under 95% during the procedures, 9 patients (5.4%) in the deflation group needed additional ventilation even though relatively healthy patients without significant pulmonary disease were enrolled. However, if we had paused ventilation until the guidewire insertion rather than until the successful placement of catheters, fewer incidences of the oxygen saturation drop under 95% could have been observed in the deflation group. Oxygen desaturation could be even worse in critically ill patients because they are less likely to tolerate a prolonged lung deflation.
In this study, we did not examine the procedure under ultrasonography guidance. Recent studies have suggested that ultrasonography-assisted insertion can increase the success rate of subclavian venous catheterization compared with the landmark-guided method.21–23 However, because of the randomized controlled design of this study, we are sure that lack of ultrasonography guidance did not produce any problems in data analysis. In addition, subclavian catheterization under ultrasonography guidance may not be always feasible because of the anatomical relationships between the SCV and the clavicle.1,24 Catheterization under ultrasonography guidance is not infallible and requires caution and experience.1,25
This study had some limitations. First, the incidence of pneumothorax was compared only during infraclavicular approach in this study. Because the distance between the pleura and the target reference line regarding the supraclavicular approach was increased after lung deflation,12 further study may be necessary for the other subclavian approaches. Second, the practitioners were confined to skilled experts and the study populations were not overweighted. Because catheterizations can be more challenging in morbidly obese patients26–28 and the complications or failure rate can be increased at the hands of less experienced persons,1,4 further research may be needed to verify our results in these populations. Third, the proportion of sex was different between the groups in our study. Although the most previous studies and our study showed similar complication rates between male and female, there are some reports that the male5 or the female29 sex showed higher complication rates, which was ascribed to their anatomical differences. Last, patients in intensive care units used to be ventilated with high inspiratory pressure and PEEP because of the decreased lung compliance. The subjects in this study were not under PEEP nor under high inspiratory pressure, which may limit general applicability of the results of this study to an intensive care unit patient.
In conclusion, the success and complication rates during infraclavicular subclavian venous catheterization were similar regardless of mechanical ventilation. Especially, maintenance of mechanical ventilation was not inferior to interruption of mechanical ventilation with regard to the incidence of pneumothorax. Thus, we may suggest that the patients’ lungs do not need to be deflated during infraclavicular subclavian venous catheterization.
Name: Eugene Kim, MD.
Contribution: This author helped conduct the study, analyze the data, and write the manuscript.
Name: Hyun Joo Kim, MD.
Contribution: This author helped design the study, conduct the study, and analyze the data.
Name: Deok Man Hong, MD, PhD.
Contribution: This author helped design the study and conduct the study.
Name: Hee-Pyoung Park, MD, PhD.
Contribution: This author helped design the study and conduct the study.
Name: Jae-Hyon Bahk, MD, PhD.
Contribution: This author helped design the study, analyze the data, and write the manuscript.
This manuscript was handled by: Sorin J. Brull, MD.
The authors express sincere gratitude to the Medical Research Collaborating Center (MRCC) of SNUH for their statistical assistance.
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