- Email: [email protected]
Basis of Estimating Pleural Effusion Size on CT Scan: Response
© 2013 American College of Chest Physicians. Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details. DOI: 10.1378/chest.13-0467
References 1. Oveland NP, Lossius HM, Wemmelund K, Stokkeland PJ, Knudsen L, Sloth E. Using thoracic ultrasound to accurately assess pneumothorax progression during positive pressure ventilation: A comparison with computed tomography. Chest. 2013; 143(2):415-422. 2. Volpicelli G. Sonographic diagnosis of pneumothorax. Intensive Care Med. 2011;37(2):224-232. 3. Lichtenstein D, Mezière G, Biderman P, Gepner A. The “lung point”: an ultrasound sign specific to pneumothorax. Intensive Care Med. 2000;26(10):1434-1440. 4. Lichtenstein DA, Mezière G, Lascols N, et al. Ultrasound diagnosis of occult pneumothorax. Crit Care Med. 2005;33(6): 1231-1238. 5. Soldati G, Testa A, Sher S, Pignataro G, La Sala M, Silveri NG. Occult traumatic pneumothorax: diagnostic accuracy of lung ultrasonography in the emergency department. Chest. 2008; 133(1):204-211.
Basis of Estimating Pleural Effusion Size on CT Scan Reasonable Grouping of Volume Percentage To the Editor: We read with great interest the article by Moy and colleagues1 in CHEST (April 2013) about estimating pleural effusion size on CT scan. The authors developed and validated a simple rule for quantitating pleural effusion size on CT scan with a three-point scale based the anteroposterior (AP) quartile and maximum AP depth: First AP quartile effusions are small, second AP quartile effusions are moderate, and third or fourth AP quartile effusions are large; in borderline cases, AP depth is measured with 3-cm and 10-cm thresholds for the upper limit of small and moderate, respectively. This newly developed classification rule can improve the interpretive consistency of all readers. The study was based on assumptive grouping: Effusion percentage cutoffs were chosen at , 20%, 20% to 40%, and . 40% of the
hemithorax for small, moderate, and large, respectively. Another study2 characterized pleural effusion occupying less than one-third, one-third to two-thirds, and greater than two-thirds of the hemithorax as small, moderate, and large, respectively, but the authors gave no explanation for choosing the assumptive grouping, which may affect the conclusion. In fact, the total volume of hemithoracic cavity changed with the volume of pleural effusion. The pleural effusion percentage was elevated with the increase of effusion volume in a nonlinear pattern, as shown in Figure 1, which was drawn according to the mean effusion volume and corresponding percentage in the study.1 Based on the curve and its trend, the more reasonable cutoff would be set at , 25%, 25% to 50%, and . 50% of the hemithorax for small, moderate, and large, respectively. In addition, it was consistent with the broadly accepted classification on the chest radiograph, in which the volume of pleural effusion identified was quantitatively assessed and qualified as small (, 500 mL), moderate (500-1,000 mL), or large (, 1,000 mL).3-5 This will improve both interobserver agreement and the consistency of different imaging methods. Yijie Hu, MD, PhD Qianjin Zhong, MD, PhD Chongqing, China Affiliations: From the Department of Cardiovascular Surgery, Institute of Surgery Research, Daping Hospital, Third Military Medical University. Financial/nonfinancial disclosures: The authors have reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article. Correspondence to: Qianjin Zhong, MD, PhD, No. 10 Changjiang Zhi Rd, Yuzhong District, Chongqing 400042, China; e-mail: [email protected] © 2013 American College of Chest Physicians. Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details. DOI: 10.1378/chest.13-0376
References 1. Moy MP, Levsky JM, Berko NS, Godelman A, Jain VR, Haramati LB. A new, simple method for estimating pleural effusion size on CT scans. Chest. 2013;143(4):1054-1059. 2. Mironov O, Ishill NM, Mironov S, et al. Pleural effusion detected at CT prior to primary cytoreduction for stage III or IV ovarian carcinoma: effect on survival. Radiology. 2011;258(3):776-784. 3. Vignon P, Chastagner C, Berkane V, et al. Quantitative assessment of pleural effusion in critically ill patients by means of ultrasonography. Crit Care Med. 2005;33(8):1757-1763. 4. Evans AL, Gleeson FV. Radiology in pleural disease: state of the art. Respirology. 2004;9(3):300-312. 5. Blackmore CC, Black WC, Dallas RV, Crow HC. Pleural fluid volume estimation: a chest radiograph prediction rule. Acad Radiol. 1996;3(2):103-109.
Response To the Editor:
Figure 1. Relationship between pleural effusion and effusionto-hemithorax volume percentage.
We thank Drs Hu and Zhong for their thoughtful letter regarding our article on estimating pleural effusion size on CT scans.1 We are happy to further clarify our reasoning for grouping effusions by percentage of the hemithorax volume into small (, 20%), moderate (20%-40%), and large (. 40%).
journal.publications.chestnet.org
Downloaded From: http://journal.publications.chestnet.org/ by David Kinnison on 06/05/2013
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Since no exact threshold accurately predicts an outcome or obligates specific management, any selection of cutoffs is arbitrary, whether based on fraction of the hemithorax or actual volume. Separation into thirds2 or use of quartiles, as suggested by Drs Hu and Zhong, are both, to our knowledge, without precedent. We designed our cutoffs rationally, with no a priori assumptions, based on the ability of the best CT imaging features to consistently separate effusions into groups.1 The rule was engineered for ease of use. It is true that a common plain radiographic classification system uses cutoffs of , 500 mL, 500 to 1,000 mL, and . 1,000 mL.3 We agree that this is a logical starting point for a rule based on CT imaging. However, we avoided a method based on raw volume for two major reasons. First, we found a weaker association between absolute effusion volume and the CT imaging features, as well as inconsistencies in the relationship of absolute volume to percentage volume. For example, small effusions ranged from 78 to 328 mL, moderate effusions ranged from 378 to 1,566 mL, and large effusions ranged from 472 to 3,673 mL (data not previously shown). Second, we firmly believe that the physiologic effect of a pleural effusion of any given volume depends on the patient’s body habitus. It is hard to imagine that a 500-mL effusion in a small, elderly woman is as well tolerated as the same volume in a hulking male athlete. In fact, our data support this common sense conclusion, as the typical geometry of the layering effusion better reflects the volume percent rather than the raw volume. Thus, the effusion percent allows a better fit for the data and a more physiologic representation of disease severity. Clinical medicine is replete with cutoffs in laboratory values, diagnostic criteria, treatment algorithms, and staging rules that undergo regular reevaluation. We claim no monopoly on assessment of pleural effusions, a disease process defined by gradations of increase from the physiologic amount of pleural fluid. The system we proposed yields an expedient and easily taught method for quantifying pleural effusions, thus advancing communication and reproducibility. Jeffrey M. Levsky, MD, PhD Bronx, NY Matthew P. Moy, MD Boston, MA Linda B. Haramati, MD, FCCP Bronx, NY Affiliations: From the Albert Einstein College of Medicine & Montefiore Medical Center (Drs Levsky and Haramati); and Massachusetts General Hospital (Dr Moy). Financial/nonfinancial disclosures: The authors have reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article. Correspondence to: Jeffrey M. Levsky, MD, PhD, Albert Einstein College of Medicine, Montefiore Medical Center, 111 E 210 St, Bronx, NY 10467; e-mail: jlevsky@montefiore.org © 2013 American College of Chest Physicians. Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details. DOI: 10.1378/chest.13-0569
References 1. Moy MP, Levsky JM, Berko NS, Godelman A, Jain VR, Haramati LB. A new, simple method for estimating pleural effusion size on CT scans. Chest. 2013;143(4):1054-1059. 2. Mironov O, Ishill NM, Mironov S, et al. Pleural effusion detected at CT prior to primary cytoreduction for stage III or IV ovarian carcinoma: effect on survival. Radiology. 2011;258(3):776-784. 3. Evans AL, Gleeson FV. Radiology in pleural disease: state of the art. Respirology. 2004;9(3):300-312.
The Use of Average Body Weight in Dosing Unfractionated Heparin To the Editor: In the American College of Chest Physicians guidelines in a supplement to CHEST (February 2012), Garcia et al1 recommend the use of weight-based unfractionated heparin (UFH). These guidelines did not address dosing in overweight and obese patients. With the prevalence of obesity in the United States, correct application of weight-based UFH therapy is an important factor in achieving therapeutic anticoagulation. UFH does not distribute into muscle or fat tissue, giving it a small volume of distribution (Vd) of 0.07 L/kg.2 In addition, adipose tissue is less vascular than lean tissue, making the Vd in obese patient difficult to assess.3 Finally, UFH has saturable pharmacokinetics, meaning requirements are not directly proportional to body weight.3 Failure to achieve an adequate activated partial thromboplastin time (APTT) response, especially in obese patients, continues to be a therapeutic challenge.4 In the Organization to Assess Strategies for Ischemic Syndromes Investigators 2 (OASIS-2) trial,5 the likelihood of major bleeding was increased by 7% for every 10-s increase in the APTT. Based on periodic internal analyses over the last 15 years, UFH dosing using average body weight correlated best with favorable APTT response. Average body weight was defined as ideal body weight plus actual body weight divided by two. All patients received a bolus of 50 units/kg followed by 15 units/kg/h continuous IV infusion based on average body weight. In an analysis from 2010 including 40 patients, the mean age was 67 (range, 35-95) years old, and 53% were men. Twenty-five patients (63%) had a BMI ⱖ 25.0, and 19 (48%) had a BMI . 30 (average, 29.8; range, 17-49). The first measured APTT was above the therapeutic threshold in 85% of the patients and was within the target range in 57% of the patients 6 to 8 h after initiation. Of the 6 patients (15%) whose initial APTT was subtherapeutic, they had the lowest BMI (average 27). This suggests that the low initial APTT may be secondary to pharmacodynamic variability instead of related to the patient’s weight. We anticipate that the use of actual weight, especially in obese patients, would result in higher initial APTT values, potentially exposing patients to unwarranted bleeding risks. Since this has been the practice at this institution, there are no comparisons of actual body weight to include in our report. The use of averageweight in UFH dosing leads to rapid and efficient anticoagulation in the majority of our patients and has led to its use at our institution. Michael Safani, PharmD Stanley E. Hill, PharmD Rex Winters, MD Stanley Kawanishi, MD Steven W. Eppstein, PharmD Stella Min, PharmD Milton Drachenberg, MD Long Beach, CA Affiliations: From the Long Beach Memorial Medical Center (Drs Safani, Hill, Winters, Kawanishi, Eppstein, Min, and Drachenberg); and the Memorial Heart and Vascular Institute (Drs Safani, Winters, and Kawanishi). Financial/nonfinancial disclosures: The authors have reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article. Corresponding author: Michael Safani, PharmD, Long Beach Memorial Medical Center, Department of Pharmacy, 2801 Atlantic Ave, Long Beach, CA 90806; e-mail: [email protected]
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Correspondence
References 1. Oveland NP, Lossius HM, Wemmelund K, Stokkeland PJ, Knudsen L, Sloth E. Using thoracic ultrasound to accurately assess pneumothorax progression during positive pressure ventilation: A comparison with computed tomography. Chest. 2013; 143(2):415-422. 2. Volpicelli G. Sonographic diagnosis of pneumothorax. Intensive Care Med. 2011;37(2):224-232. 3. Lichtenstein D, Mezière G, Biderman P, Gepner A. The “lung point”: an ultrasound sign specific to pneumothorax. Intensive Care Med. 2000;26(10):1434-1440. 4. Lichtenstein DA, Mezière G, Lascols N, et al. Ultrasound diagnosis of occult pneumothorax. Crit Care Med. 2005;33(6): 1231-1238. 5. Soldati G, Testa A, Sher S, Pignataro G, La Sala M, Silveri NG. Occult traumatic pneumothorax: diagnostic accuracy of lung ultrasonography in the emergency department. Chest. 2008; 133(1):204-211.
Basis of Estimating Pleural Effusion Size on CT Scan Reasonable Grouping of Volume Percentage To the Editor: We read with great interest the article by Moy and colleagues1 in CHEST (April 2013) about estimating pleural effusion size on CT scan. The authors developed and validated a simple rule for quantitating pleural effusion size on CT scan with a three-point scale based the anteroposterior (AP) quartile and maximum AP depth: First AP quartile effusions are small, second AP quartile effusions are moderate, and third or fourth AP quartile effusions are large; in borderline cases, AP depth is measured with 3-cm and 10-cm thresholds for the upper limit of small and moderate, respectively. This newly developed classification rule can improve the interpretive consistency of all readers. The study was based on assumptive grouping: Effusion percentage cutoffs were chosen at , 20%, 20% to 40%, and . 40% of the
hemithorax for small, moderate, and large, respectively. Another study2 characterized pleural effusion occupying less than one-third, one-third to two-thirds, and greater than two-thirds of the hemithorax as small, moderate, and large, respectively, but the authors gave no explanation for choosing the assumptive grouping, which may affect the conclusion. In fact, the total volume of hemithoracic cavity changed with the volume of pleural effusion. The pleural effusion percentage was elevated with the increase of effusion volume in a nonlinear pattern, as shown in Figure 1, which was drawn according to the mean effusion volume and corresponding percentage in the study.1 Based on the curve and its trend, the more reasonable cutoff would be set at , 25%, 25% to 50%, and . 50% of the hemithorax for small, moderate, and large, respectively. In addition, it was consistent with the broadly accepted classification on the chest radiograph, in which the volume of pleural effusion identified was quantitatively assessed and qualified as small (, 500 mL), moderate (500-1,000 mL), or large (, 1,000 mL).3-5 This will improve both interobserver agreement and the consistency of different imaging methods. Yijie Hu, MD, PhD Qianjin Zhong, MD, PhD Chongqing, China Affiliations: From the Department of Cardiovascular Surgery, Institute of Surgery Research, Daping Hospital, Third Military Medical University. Financial/nonfinancial disclosures: The authors have reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article. Correspondence to: Qianjin Zhong, MD, PhD, No. 10 Changjiang Zhi Rd, Yuzhong District, Chongqing 400042, China; e-mail: [email protected] © 2013 American College of Chest Physicians. Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details. DOI: 10.1378/chest.13-0376
References 1. Moy MP, Levsky JM, Berko NS, Godelman A, Jain VR, Haramati LB. A new, simple method for estimating pleural effusion size on CT scans. Chest. 2013;143(4):1054-1059. 2. Mironov O, Ishill NM, Mironov S, et al. Pleural effusion detected at CT prior to primary cytoreduction for stage III or IV ovarian carcinoma: effect on survival. Radiology. 2011;258(3):776-784. 3. Vignon P, Chastagner C, Berkane V, et al. Quantitative assessment of pleural effusion in critically ill patients by means of ultrasonography. Crit Care Med. 2005;33(8):1757-1763. 4. Evans AL, Gleeson FV. Radiology in pleural disease: state of the art. Respirology. 2004;9(3):300-312. 5. Blackmore CC, Black WC, Dallas RV, Crow HC. Pleural fluid volume estimation: a chest radiograph prediction rule. Acad Radiol. 1996;3(2):103-109.
Response To the Editor:
Figure 1. Relationship between pleural effusion and effusionto-hemithorax volume percentage.
We thank Drs Hu and Zhong for their thoughtful letter regarding our article on estimating pleural effusion size on CT scans.1 We are happy to further clarify our reasoning for grouping effusions by percentage of the hemithorax volume into small (, 20%), moderate (20%-40%), and large (. 40%).
journal.publications.chestnet.org
Downloaded From: http://journal.publications.chestnet.org/ by David Kinnison on 06/05/2013
CHEST / 143 / 6 / JUNE 2013
1839
Since no exact threshold accurately predicts an outcome or obligates specific management, any selection of cutoffs is arbitrary, whether based on fraction of the hemithorax or actual volume. Separation into thirds2 or use of quartiles, as suggested by Drs Hu and Zhong, are both, to our knowledge, without precedent. We designed our cutoffs rationally, with no a priori assumptions, based on the ability of the best CT imaging features to consistently separate effusions into groups.1 The rule was engineered for ease of use. It is true that a common plain radiographic classification system uses cutoffs of , 500 mL, 500 to 1,000 mL, and . 1,000 mL.3 We agree that this is a logical starting point for a rule based on CT imaging. However, we avoided a method based on raw volume for two major reasons. First, we found a weaker association between absolute effusion volume and the CT imaging features, as well as inconsistencies in the relationship of absolute volume to percentage volume. For example, small effusions ranged from 78 to 328 mL, moderate effusions ranged from 378 to 1,566 mL, and large effusions ranged from 472 to 3,673 mL (data not previously shown). Second, we firmly believe that the physiologic effect of a pleural effusion of any given volume depends on the patient’s body habitus. It is hard to imagine that a 500-mL effusion in a small, elderly woman is as well tolerated as the same volume in a hulking male athlete. In fact, our data support this common sense conclusion, as the typical geometry of the layering effusion better reflects the volume percent rather than the raw volume. Thus, the effusion percent allows a better fit for the data and a more physiologic representation of disease severity. Clinical medicine is replete with cutoffs in laboratory values, diagnostic criteria, treatment algorithms, and staging rules that undergo regular reevaluation. We claim no monopoly on assessment of pleural effusions, a disease process defined by gradations of increase from the physiologic amount of pleural fluid. The system we proposed yields an expedient and easily taught method for quantifying pleural effusions, thus advancing communication and reproducibility. Jeffrey M. Levsky, MD, PhD Bronx, NY Matthew P. Moy, MD Boston, MA Linda B. Haramati, MD, FCCP Bronx, NY Affiliations: From the Albert Einstein College of Medicine & Montefiore Medical Center (Drs Levsky and Haramati); and Massachusetts General Hospital (Dr Moy). Financial/nonfinancial disclosures: The authors have reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article. Correspondence to: Jeffrey M. Levsky, MD, PhD, Albert Einstein College of Medicine, Montefiore Medical Center, 111 E 210 St, Bronx, NY 10467; e-mail: jlevsky@montefiore.org © 2013 American College of Chest Physicians. Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details. DOI: 10.1378/chest.13-0569
References 1. Moy MP, Levsky JM, Berko NS, Godelman A, Jain VR, Haramati LB. A new, simple method for estimating pleural effusion size on CT scans. Chest. 2013;143(4):1054-1059. 2. Mironov O, Ishill NM, Mironov S, et al. Pleural effusion detected at CT prior to primary cytoreduction for stage III or IV ovarian carcinoma: effect on survival. Radiology. 2011;258(3):776-784. 3. Evans AL, Gleeson FV. Radiology in pleural disease: state of the art. Respirology. 2004;9(3):300-312.
The Use of Average Body Weight in Dosing Unfractionated Heparin To the Editor: In the American College of Chest Physicians guidelines in a supplement to CHEST (February 2012), Garcia et al1 recommend the use of weight-based unfractionated heparin (UFH). These guidelines did not address dosing in overweight and obese patients. With the prevalence of obesity in the United States, correct application of weight-based UFH therapy is an important factor in achieving therapeutic anticoagulation. UFH does not distribute into muscle or fat tissue, giving it a small volume of distribution (Vd) of 0.07 L/kg.2 In addition, adipose tissue is less vascular than lean tissue, making the Vd in obese patient difficult to assess.3 Finally, UFH has saturable pharmacokinetics, meaning requirements are not directly proportional to body weight.3 Failure to achieve an adequate activated partial thromboplastin time (APTT) response, especially in obese patients, continues to be a therapeutic challenge.4 In the Organization to Assess Strategies for Ischemic Syndromes Investigators 2 (OASIS-2) trial,5 the likelihood of major bleeding was increased by 7% for every 10-s increase in the APTT. Based on periodic internal analyses over the last 15 years, UFH dosing using average body weight correlated best with favorable APTT response. Average body weight was defined as ideal body weight plus actual body weight divided by two. All patients received a bolus of 50 units/kg followed by 15 units/kg/h continuous IV infusion based on average body weight. In an analysis from 2010 including 40 patients, the mean age was 67 (range, 35-95) years old, and 53% were men. Twenty-five patients (63%) had a BMI ⱖ 25.0, and 19 (48%) had a BMI . 30 (average, 29.8; range, 17-49). The first measured APTT was above the therapeutic threshold in 85% of the patients and was within the target range in 57% of the patients 6 to 8 h after initiation. Of the 6 patients (15%) whose initial APTT was subtherapeutic, they had the lowest BMI (average 27). This suggests that the low initial APTT may be secondary to pharmacodynamic variability instead of related to the patient’s weight. We anticipate that the use of actual weight, especially in obese patients, would result in higher initial APTT values, potentially exposing patients to unwarranted bleeding risks. Since this has been the practice at this institution, there are no comparisons of actual body weight to include in our report. The use of averageweight in UFH dosing leads to rapid and efficient anticoagulation in the majority of our patients and has led to its use at our institution. Michael Safani, PharmD Stanley E. Hill, PharmD Rex Winters, MD Stanley Kawanishi, MD Steven W. Eppstein, PharmD Stella Min, PharmD Milton Drachenberg, MD Long Beach, CA Affiliations: From the Long Beach Memorial Medical Center (Drs Safani, Hill, Winters, Kawanishi, Eppstein, Min, and Drachenberg); and the Memorial Heart and Vascular Institute (Drs Safani, Winters, and Kawanishi). Financial/nonfinancial disclosures: The authors have reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article. Corresponding author: Michael Safani, PharmD, Long Beach Memorial Medical Center, Department of Pharmacy, 2801 Atlantic Ave, Long Beach, CA 90806; e-mail: [email protected]
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Correspondence