Why are patients with acute exacerbation of COPD at higher risk of venous thromboembolism (VTE)?

Patients admitted to the hospital for acute exacerbation of COPD are generally regarded as being at high risk of venous thromboembolism (VTE) (prevalence 5%-29%), possibly due to the frequent coexistence of other risk factors, such as immobility, history of smoking, and venous stasis.1 The exact mechanism(s) behind this association remains poorly understood, however.

Among patients with moderate-very severe COPD (GOLD criteria stage II-IV),  high BMI, low exercise tolerance, history of pneumothorax, congestive heart failure, and peripheral vascular disease have also been associated with VTE.1

Systemic inflammation has also been implicated in increasing the risk of VTE in patients with COPD. Although the pathophysiology of COPD is largely defined by the local inflammatory response to airway injury, evidence suggests that there is also a systemic inflammatory response in COPD.2,3 This systemic inflammation could in turn contribute to the increased risk of vascular disease, including VTE, coronary artery disease, and cerebrovascular disease.4

Bonus pearl: Did you know that VTE may be 3x more prevalent among patients with COPD exacerbation without known cause (vs those with identifiable cause) and is associated with a 1-year mortality of 61.9%! 5

References:

  1. Kim V, Goel N, Gangar J, et al. Risk factors for venous thromboembolism in chronic obstructive pulmonary disease. Chronic Obstr Pulm Dis 2014;1: 239-249. https://www.ncbi.nlm.nih.gov/pubmed/25844397
  2. Lankeit M, Held M. Incidence of venous thromboembolism in COPD: linking inflammation and thrombosis? Eur Respir J 2016;47(2):369-73. https://www.ncbi.nlm.nih.gov/pubmed/26828045
  3. Sinden NJ1, Stockley RA. Systemic inflammation and comorbidity in COPD: a result of ‘overspill’ of inflammatory mediators from the lungs? Review of the evidence. Thorax 2010;65:930-6. https://www.ncbi.nlm.nih.gov/pubmed/20627907
  4. King PT. Inflammation in chronic obstructive pulmonary disease and its role in cardiovascular disease and lung cancer. Clinical and Translational Medicine 2015;4:26. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4518022/
  5. Gunen H, Gulbas G, In E, et al. Venous thromboemboli and exacerbations of COPD. Eur Respir J 2010;36:1243-8.  https://www.ncbi.nlm.nih.gov/pubmed/19926740 

Contributed by Camilo Campo, Medical Student, Harvard Medical School, Boston, MA.

Why are patients with acute exacerbation of COPD at higher risk of venous thromboembolism (VTE)?

Can non-steroidal anti-inflammatory drugs (NSAIDs) suppress cancer metastasis?

A 2017 meta-analysis reported that NSAIDs are associated with lower risk of distant metastasis in patients with breast, prostate, lung, and colorectal cancer.1

The mechanism accounting for this observation is not fully understood. However, since inflammation has been implicated as a driving force for tumor metastasis 2, blunting the inflammatory microenvironment that surrounds tumors may explain NSAIDs’ reported beneficial effect.

NSAIDs may also have a direct effect on cancer cells. In-vitro studies demonstrate that NSAIDs induce the expression of a protein (p75 neurotrophic receptor, p75NTR) associated with suppression of tumor growth and metastasis in prostate cancer; this protein also suppresses growth of bladder cancer cells.3,4

Ibuprofen and indomethacin are among the commonly available NSAIDS shown to exhibit such anti-tumor effect. Interestingly, non-COX-inhibiting NSAIDS (eg, [R] flurbiprofen, an enantiomer of ibuprofen) may also be effective suggesting that inhibition of cell survival may not be COX-mediated.

Although these findings and observations are promising, randomized-controlled trials are clearly needed to better define the role of NSAIDs in the clinical management of cancer.

 

References: 

  1. Zhao X, Xu Z, Li H. NSAIDs use and reduced metastasis in cancer patients: Results from a meta-analysis. Sci Rep 2017; 7:1875. https://www.ncbi.nlm.nih.gov/pubmed/28500305
  2. Qian BZ. Inflammation fires up cancer metastasis. Semin Cancer Biol 2017; 47:170-176. https://www.ncbi.nlm.nih.gov/pubmed/28838845
  3. Khwaja F, Allen J, Lynch J, Andrews P, Djakiew D. Ibuprofen inhibits survival of bladder cancer cells by induced expression of the p75NTR tumor suppressor protein. Cancer Res 2004; 64:6207-6213. https://www.ncbi.nlm.nih.gov/pubmed/15342406
  4. Krygier S, Djakiew D. Neurotrophin receptor p75NTR suppresses growth and nerve growth factor-mediated metastasis of human prostate cancer cells. Int J Cancer 2002; 98:1-7. https://www.ncbi.nlm.nih.gov/pubmed/11857376

Contributed by Camilo Campo, Medical Student, Harvard Medical School, Boston, MA.

Can non-steroidal anti-inflammatory drugs (NSAIDs) suppress cancer metastasis?

Can I rule out primary adrenal insufficiency by obtaining a single morning serum cortisol level in my hospitalized patient with unexplained hyponatremia?

Primary adrenal insufficiency (PAI) can be confidently ruled out when the morning (eg, 6 AM) serum cortisol level is greater than 17 ug/dl. Lower cut-off values are associated with lower probability of excluding PAI: > 10 ug/dl, 62%-67% and ≥5 ug/dl, 36%. 1,2 Conversely, PAI is highly likely when the morning serum cortisol level is less than 3 ug/dl. 3

Since many patients may have serum cortisol levels between 3 ug/dl and 17 ug/dl (ie, in the “indeterminate” range), confirmatory testing commonly performed through cosyntropin stimulation test (CST) is often necessary.

Although the standard CST involves measuring serum cortisol levels at baseline, 30 min, and 60 min with peak cortisol level <18 ug/dl indicative of PAI, several studies have reported that a single post-CST cortisol level obtained at 60 min may also be diagnostic. 3

 

References

  1. Erturk E, Jaffe CA, Barkan AL. Evaluation of the integrity of the hypothalamic-pituitary-adrenal axis by insulin hypoglycemia test. J Clin Endocrinol Metab 83;2350-54. https://www.ncbi.nlm.nih.gov/pubmed/9661607
  2. Bornstein SR, Allolio B, Arlt W, et al. Diagnosis and treatment of primary adrenal insufficiency: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab 2016;101:364-89. https://academic.oup.com/jcem/article/101/2/364/2810222
  3. Odom DC, Gronowski AM, Odom E, et al. A single, post-ACTH cortisol measurement to screen for adrenal insufficiency in the hospitalized patient. J Hosp Med 2018;13: E1-E5. https://www.ncbi.nlm.nih.gov/pubmed/29444197
Can I rule out primary adrenal insufficiency by obtaining a single morning serum cortisol level in my hospitalized patient with unexplained hyponatremia?

Should I order a blood transfusion based on the hemoglobin (Hgb) or the hematocrit (Hct)?

Despite the frequent interchangeability of Hgb (g/dL) and Hct (%) by a ratio of ~1:3, directly-measured blood Hgb levels may be preferred for assessing the need for blood transfusion for at least 3 reasons:

First, in contrast to the widely-used automated measurements of Hct, Hgb is not affected by conditions that affect the size of the RBCs or the mean corpuscular Hgb concentration (MCHC). This is because the Hct is not a direct measure of Hgb; rather it’s the proportion of blood occupied by RBCs which, in automated systems, is derived by multiplying the number of RBCs by the mean corpuscular volume (MCV).1-3

This may not be a significant issue when MCHC is normal, but when MCHC is abnormal, HCT may not accurately reflect the blood Hgb concentration. For example, in patients with hypochromic iron deficiency anemia with RBCs containing less hemoglobin (ie, low MCHC), the Hct may overestimate blood Hgb levels. Conversely in hereditary spherocytosis with its attendant low RBC volume and high MCHC, the Hct may underestimate Hgb levels.

Second, Hct results may also be more subject to technical factors in the lab. For example, blood at room temperature between 6-24 h may be associated with RBC swelling and increased Hct without any change in its Hgb concentration.4

Finally, national and international guidelines on blood transfusion generally target Hgb, not Hct results.5-7

For a related pearl, go to https://pearls4peers.com/2016/11/01/should-i-use-a-hemoglobin-level-of-7-or-8-gdl-as-a-threshold-for-blood-transfusion-in-my-hospitalized-patient.

 

References

  1. Tefferi A, Hanson CA, Inwards DJ. How to interpret and pursue an abnormal complete blood cell count in adults. Mayo Clin Proc 2005;80:923-36. https://www.ncbi.nlm.nih.gov/pubmed/16007898
  2. Macdougall IC, Ritz E. The Normal Haematocrit Trial in dialysis patients with cardiac disease: are we any the less confused about target hemoglobin? Nephrol Dial Transplant 1998;13:3030-33. https://academic.oup.com/ndt/article-pdf/13/12/3030/9907456/3030.pdf
  3. Kelleher BP, Wall C, O’Broin SD. Haemoglobin, not haematocrit, should be the preferred parameter. Nephrol Dial Transplant 2001;16:1085-87. https://www.ncbi.nlm.nih.gov/pubmed/11328933
  4. Hayuanta HH. Can hemoglobin-hematocrit relationship be used to assess hydration status? CDK-237/vol 43 no.2, th. 2016 http://www.kalbemed.com/Portals/6/20_237Opini-Can%20Hemoglobin-Hematocrit%20Relationship%20Be%20Used%20to%20Assess%20Hydration%20Status.pdf
  5. Blood transfusion. NICE guideline, November, 2015. https://www.nice.org.uk/guidance/ng24/chapter/Recommendations#fresh-frozen-plasma-2 uk
  6. National Blood Authority: Australia. Patient blood management, November 2016. https://www.blood.gov.au/system/files/documents/nba-patient-blood-management-resource-guide-nov_2016_v3_sm_web_file.pdf
  7. Carson JL, Guyatt G, Heddle NM, et al. Clinical practice guidelines from the AAABB: red blood cell transfusion thresholds and storage. JAMA 2016; 316:2025-2035. https://www.ncbi.nlm.nih.gov/pubmed/27732721

 

If you like this pearl, don’t forget to sign up for future pearls delivered directly to your mailbox from “Oceans of Knowledge”!

Should I order a blood transfusion based on the hemoglobin (Hgb) or the hematocrit (Hct)?

How should I interpret the growth of “normal respiratory flora” from sputum of my patient with community-acquired pneumonia (CAP)?

Since the primary reason for obtaining a sputum culture in a patient with pneumonia is to sample the lower respiratory tract, you should first verify that the sputum was “adequate” by reviewing the gram stain. Absence of neutrophils (unless the patient is neutropenic) with or without epithelial cells on gram stain of sputum suggests that it may not be an adequate sample (ie, likely saliva)1, and therefore growth of normal respiratory flora (NRF) should not be surprising in this setting.  

Other potential explanations for NRF on sputum culture in patients with CAP include:2-5

  • Delay in sputum processing with possible overgrowth of oropharyngeal flora.
  • Pneumonia caused by pathogens that do not grow on standard sputum culture media (eg, atypical organisms, viruses, anaerobes).
  • Pneumonia caused by potential pathogens such as as Streptococcus mitis and Streptococcus anginosus group that may be part of the NRF.
  • Initiation of antibiotics prior to cultures (eg, in pneumococcal pneumonia).

Of note, since 2010, several studies have shown that over 50% of patients with CAP do not have an identifiable cause.3 So, growing NRF from sputum of patients with CAP appears to be common.

References

  1. Wong LK, Barry AL, Horgan SM. Comparison of six different criteria for judging the acceptability of sputum specimens. J Clin Microbiol 1982;16:627-631. https://www.ncbi.nlm.nih.gov/pubmed/7153311
  2. Donowitz GR. Acute pneumonia. In Mandell, Douglas, and Bennett’s Principles and Practice of Infectious Diseases (2010). Churchill Livingstone, pp 891-916.
  3. Musher DM, Abers MS, Bartlett JG. Evolving understanding of the causes of pneumonia in adults, with special attention to the role of pneumococcus. Clin Infect Dis 2017;65: 1736-44. https://www.ncbi.nlm.nih.gov/pubmed/29028977
  4. Abers MS, Musher DM. The yield of sputum culture in bacteremic pneumococcal pneumonia after initiation of antibiotics. Clin Infect Dis 2014; 58:1782. https://www.ncbi.nlm.nih.gov/pubmed/24604901
  5. Bartlett JG, Gorbach SL, Finegold SM. The bacteriology of aspiration pneumonia. Bartlett JG, Gorbach SL, Finegold SM. Am J Med 1974;56:202-7. https://www.ncbi.nlm.nih.gov/pubmed/4812076
How should I interpret the growth of “normal respiratory flora” from sputum of my patient with community-acquired pneumonia (CAP)?

Can my patient with renal insufficiency safely undergo gadolinium-based contrast MRI?

It may be possible for patients with renal insufficiency, including those with end-stage kidney disease (ESKD), to undergo MRI using potentially safer preparations of gadolinium-based contrast agents (GBCAs) with “very low, if any” risk of the feared nephrogenic systemic sclerosis (NSF). 1

In contrast to the so called “linear” chelates of gadolinium (eg, gadodiamide, gadopentetate), “cyclic” GBCA’s (eg, gadoteridol) have not been clearly associated with NSF. 2 A Veterans Administration study involving gadoteridol identified no cases of NSF among the 141 patients on hemodialysis following 198 exposures. 2 In fact, the 2017 American College of Radiology (ACR) Manual on Contrast Media reports the risk of NSF with cyclic chelates as “very low, if any”. 1 Even when a cyclic GBCA is used in patients with ESKD, however, hemodialysis is recommended as soon as possible after MRI. 3

GBCAs are chelates with 2 major components: gadolinium and either a linear or cyclic ligand. Cyclic ligands bind to gadolinium more avidly, resulting in lower probability of circulating renally-cleared free gadolinium which when deposited in tissue is thought to potentially trigger NSF.2

Although NSF is characterized by progressive fibrosis of skin and soft tissue, it may involve multiple organs with an estimated 30% mortality rate. 4

 Bonus Pearl: Did you know NSF is really a new disease, with no evidence of its existence before 1997?

References

  1. “Nephrogenic Systemic Fibrosis”. In ACR Manual on Contrast Media; Version 10.3; May 31, 2017. https://www.acr.org/-/media/ACR/Files/Clinical-Resources/Contrast_Media.pdf
  2. Reilly RF. Risk for nephrogenic systemic fibrosis with gadoteridol (ProHance) in patients who are on long-term hemodialysis. Clin J Am Soc Nephrol 2008;3:747-51. https://www.ncbi.nlm.nih.gov/pubmed/18287249
  3. Wang Y, Alkasab TK, Nari O, et al. Incidence of nephrogenic systemic fibrosis after adoption of restrictive gadolinium-based contrast agent guidelines. Radiology 2011;260:105-111.  https://www.ncbi.nlm.nih.gov/pubmed/21586680
  4. Schlaudecker JD, Bernheisel CR. Gadolinium-associated nephrogenic systemic fibrosis. Am Fam Physician 2009;80:711-14. https://www.aafp.org/afp/2009/1001/p711.pdf

 

Contributed by Richard Newcomb, MD, Mass General Hospital, Boston, MA.

Can my patient with renal insufficiency safely undergo gadolinium-based contrast MRI?

Can my patient develop “anemia of chronic disease” acutely while hospitalized?

“Anemia of chronic disease” is better termed anemia of inflammation (AI) which may occur in acute as well as chronic inflammatory states. 1 As such, the view that anemia in the critically ill patients is simply caused by excess phlebotomy is inaccurate. 2 The CRIT study demonstrated that AI in critically ill patients develops even within 30 days, often despite blood transfusions. 3

In addition to the usual causes of AI (eg autoimmune disorders), AI can occur during bacterial, viral or yeast infections and sepsis 4,5.

Recent studies implicate both iron sequestration and impaired erythropoiesis as causes of AI. 1 Inflammation stimulates hepatic production of iron-regulatory peptide, hepcidin, which decreases delivery of iron from macrophages to developing erythrocytes.  Inflammation also causes production of pro-inflammatory cytokine, IL-6, which suppresses erythropoiesis.

Couple of cool studies using injection of heat-killed Brucella abortus in mice as a model of AI, showed dramatic hemoglobin drop by 7 days.6,7. In addition, not only were iron restriction from increase in hepcidin and transient erythropoiesis demonstrated, erythrocyte lifespan was also shortened in these experiments. AI is truly a multifactorial process.

 

References 

  1. Frankel PG. Anemia of inflammation: A review. Med Clin N Ame 2017;101:285-96. https://www.ncbi.nlm.nih.gov/pubmed/28189171
  2. Corwin HL, Krantz SB. Anemia of the critically ill: “Acute” anemia of chronic disease. Crit Care Med 2000;28:3098-99. https://www.ncbi.nlm.nih.gov/pubmed/10966311
  3. Corwin HL, Gettinger A, Pearl RG, et al. The CRIT study: anemia and blood transfusion in the critically ill-current clinical practice in the United states. Crit Care Med 2004;32:39-52. https://www.ncbi.nlm.nih.gov/pubmed/14707558
  4. Gabriel A, Kozek S, Chiari A, et al. High-dose recombinant human erythropoietin stimulates reticulocyte production in patients with multiple organ dysfunction syndrome. J Trauma:Injury, Infection, and Critical Care 1998;44:361-67. https://www.ncbi.nlm.nih.gov/pubmed/9498512
  5. Roy CN. Anemia of inflammation. Hematology Am Soc Hematol Educ Program. 2010;2010:276-80. doi: 10.1182/asheducation-2010.1.276. https://www.ncbi.nlm.nih.gov/pubmed/21239806
  6. Kim A, Fung E, Parikh SG, et al. A mouse model of anemia of inflammation: complex pathogenesis with partial dependence on hepcidin. Blood 2014;123:1129-36. https://www.ncbi.nlm.nih.gov/pubmed/24357728
  7. Gardenghi S, Renaud TM, Meloni A, et al. Distinct roles for hepcidin and interleukin-6 in the recovery from anemia in mice injected with heat-killed Brucella abortus. Blood 2014;123:1137-45. https://www.ncbi.nlm.nih.gov/pubmed/24357729
Can my patient develop “anemia of chronic disease” acutely while hospitalized?