Why is my patient with diabetic ketoacidosis (DKA) and hypovolemia hypertensive?

Although we may expect patients with DKA to present with hypotension due to hypovolemia, many patients with DKA may actually be hypertensive. This finding is particularly intriguing because hyperinsulinemia, not insulinopenia as found in DKA, has been associated with hypertension. 1,2

Though not proven, potential explanations for hypertension in DKA include elevated serum levels of catecholamines, pro-inflammatory cytokines, renin, angiotension II and aldosterone.3-5 Hyperosmolality may also lead to the release of antidiuretic hormone (ADH) which increases blood pressure via V2 receptors.  Another possibility is that the high insulin levels associated with the treatment of DKA suppress the catecholamine-stimulated production of vasodilative eicosanoids (eg, prostaglandins) by adipose tissue. 1 It’s possible that in any given patient, 1 or more of these mechanisms may be enough to override the potential hypotensive effect of insulin deficiency in DKA.

We should note that reports of frequent hypertension in DKA have primarily involved pediatric patients. A 2011 study found that 82% of pediatric patients with DKA had hypertension during the first 6 hours of admission with no patient having hypotension.3  

On the other extreme, refractory hypotension without obvious cause (eg, sepsis, acute adrenal insufficiency, cardiogenic causes) has also been reported in DKA.5Because insulin inhibits the production of vasodilative prostaglandins (eg, PGI2 and PGE2), severe insulin deficiency in DKA can also contribute to hypotension along with volume depletion. 

Potential genetic polymorphism in the synthesis and metabolism of prostaglandins may at least partially explain the varied blood pressure response and whether a patient with DKA presents with hypertension or hypotension. 5  

The author would like to acknowledge the valuable contribution of Lloyd Axelrod MD, Massachusetts General Hospital, to this post.

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  1. Axelrod L. Insulin, prostaglandins, and the pathogenesis of hypertension. Diabetes 1991;40:1223-1227. https://diabetes.diabetesjournals.org/content/40/10/1223 
  2. Chatzipantelli K, Head C, Megerman J, et al. The relationship between plasma insulin level, prostaglandin productin by adipose tissue and blood pressure in normal rats and rats with diabetes mellitus and diabetic ketoacidosis. Metabolism 1996;45:691-98. https://www.sciencedirect.com/science/article/abs/pii/S002604959690133X 
  3. Deeter KH, Roberts JS, Bradford H, et al. Hypertension despite dehydration during severe pediatric diabetic ketoacidosis. Pediatr Diabetes 2011;12:295-301. https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1399-5448.2010.00695.x 
  4. Ferris JB, O’Hare JA, Kelleher CM, et al. Diabetic control and the renin-angiotensin system, catecholamines and blood pressure. Hypertension 1985 7(Suppl II):II-58-II-63. https://www.ahajournals.org/doi/abs/10.1161/01.HYP.7.6_Pt_2.II58  
  5. Singh D, Cantu M, Marx MHM, et al. Diabetic ketoacidosis and fluid refractory hypotension. Clin Pediatrics 2016;55:182-84. https://journals.sagepub.com/doi/abs/10.1177/0009922815584549?journalCode=cpja 


Why is my patient with diabetic ketoacidosis (DKA) and hypovolemia hypertensive?

My patient with COPD exacerbation has an elevated venous blood PCO2. How accurate is the peripheral venous blood gas PC02 in patients with hypercarbia?

Short answer: Not as accurate as we might like! An elevated venous pC02 is a good indicator of the presence of arterial hypercarbia but beyond that if you really want to know what the arterial pC02 is in your patient with hypercarbia, you should get an arterial blood gas (ABG).

A meta-analysis of studies involving patients with COPD presenting to the emergency department (ED) found a good agreement for pH and bicarbonate values between arterial and venous blood gases but not for pC02 or p02 (1). More specifically, the 95% limit of agreement varied widely from -17 to +26 mmHg between venous and arterial pC02 (average difference ~6.0 mm). In the same study, a venous pC02 of ~45 mmHg or less correctly identified patients who were hypercarbic based on ABG. Similar results have been reported by other studies involving patients with COPD exacerbation (2,3).

Another meta-analysis involving all comers (COPD and non-COPD patients) concluded that venous pC02 should not be used as a substitute for arterial pC02 when accurate pC02 is required (4). In fact, they emphasized that venous pC02 was not always greater than arterial pC02!

Bonus pearl: Did you know that an unexpectedly low bicarbonate level in a patient with COPD and CO2 retention should alert us to the possibility of concurrent metabolic acidosis (eg, due to lactic acidosis, uremia)?

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1. Lim BL, Kelly AM. A meta-analysis on the utility of peripheral venous blood gas analyses in exacerbations of chronic obstructive pulmonary disease in the emergency department. Eur J Emerg Med 2010;17:246-48. https://journals.lww.com/euro-emergencymed/Abstract/2010/10000/A_meta_analysis_on_the_utility_of_peripheral.2.aspx
2. McCanny P, Bennett K, Staunton P, et a. Venous vs arterial blood gases in the assessment of patients presenting with an exacerbation of chronic obstructive pulmonary disease. Am J Emerg Med 2012;30:896-900. https://www.sciencedirect.com/science/article/abs/pii/S0735675711002865
3. McKeevere TM, Hearson G, Housely G, et al. Using venous blood gas analysis in the assessment of COPD exacerbations: a prospective cohort study. Thorax 2016;71:210-15. https://www.researchgate.net/publication/285545995_Using_venous_blood_gas_analysis_in_the_assessment_of_COPD_exacerbations_A_prospective_cohort_study
4. Byrne AL, Bennett M, Chatterji R, et al. Peripheral venous and arterial blood gas analysis in adults:are they comparable? A systematic review and meta-analysis. Respirology 2014;19:168-75. https://onlinelibrary.wiley.com/doi/full/10.1111/resp.12225

My patient with COPD exacerbation has an elevated venous blood PCO2. How accurate is the peripheral venous blood gas PC02 in patients with hypercarbia?

My 70 year old male patient is admitted with 1 day of fever, dysuria, and urinary frequency and urgency, but has a negative urine dipstick test for nitrites and leukocyte esterase. Could he still have acute bacterial prostatitis?

Short answer: Yes! In fact, no routine clinical imaging test can adequately rule out prostatic involvement in men with urinary tract infection (UTI) symptoms (1)! 

Although the presence of nitrites and leukocyte esterase (LE) may have a high positive predictive value for acute bacterial prostatitis (ABP) (~95%), their combined absence has a negative predictive value of only ~70%; ie, we may miss about one-third of patients with UTI symptoms if we relied solely on the results of nitrite and LE urine dipstick (2,3). Negative nitrites alone has a negative predictive value of only ~ 45%, while a negative LE has a negative predictive value of ~60% (3).

To evaluate for ABP, our patient should undergo rectal exam for prostatic tenderness, as should all men with UTI symptoms. The finding of a tender prostate in this setting is supportive of ABP, although its absence will still not rule out this diagnosis because the reported sensitivity of rectal exam may vary from 9% to 100% in ABP (1). 
Although there may not be a general agreement on the definition of ABP, 2 studies utilizing indium-labeled leukocyte scintigraphy or a combination of PSA levels and transrectal ultrasound have provided evidence for frequent prostatic involvement in men with UTI symptoms (4,5).  In these studies, an inflammatory reaction within the prostate was seen in the majority of cases, even when the digital rectal examination was not painful or when clinicians diagnosed pyelonephritis without prostatitis.
Bonus pearl: Did you know that the lifetime probability of a man receiving a diagnosis of prostatitis is >25% (1)? 

Also see a related P4P pearl: https://pearls4peers.com/2017/07/27/should-male-patients-with-suspected-urinary-tract-infection-routinely-undergo-a-prostate-exam/


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1. Etienne M, Chavanet P, Sibert L, et al. Acute bacterial prostatitis: heterogeneity in diagnostic criteria and management. Retrospective multicentric analysis of 371 patients diagnosed with acute prostatitis. BMC Infect Dis 2008, 8:12 doi:10.1186/1471-2334-8-12. https://bmcinfectdis.biomedcentral.com/articles/10.1186/1471-2334-8-12
2. Lipsky BA, Byren I, Hoey CT. Treatment of bacterial prostatitis. Clin Infect Dis 2010;50:1641-1652. https://academic.oup.com/cid/article/50/12/1641/305217
3. Etienne M, Pestel-Caron M, Chavanet P, et al. Performance of the urine leukocyte esterase and nitrite dipstick test for the diagnosis of acute prostatitis. Clin Infect Dis 2008; 46:951-53. https://academic.oup.com/cid/article/46/6/951/351423
4. Velasco M, Mateos JJ, Martinez JA, et al. Accurate topographical diagnosis of urinary tract infection in male patients with (111)indium-labelled leukocyte scintigraphy. Eur J Intern Med 2004;15:157-61. https://www.ncbi.nlm.nih.gov/pubmed/15245717
5. Ulleryd P, Zackrisson B, Aus G, et al. Prostatic involvement in men with febrie urinary tract infection as measured by serum prostate-specific antigen and transrectal ultrasonography. BJU Int 1999;84:470-74. https://onlinelibrary.wiley.com/doi/full/10.1046/j.1464-410x.1999.00164.x


My 70 year old male patient is admitted with 1 day of fever, dysuria, and urinary frequency and urgency, but has a negative urine dipstick test for nitrites and leukocyte esterase. Could he still have acute bacterial prostatitis?

My patient has developed isolated eosinophilia without symptoms while receiving an antibiotic. Should I consider discontinuing the antibiotic or can I just continue it as long as she has no symptoms?

Short answer: We don’t really know what’s the best way to manage patients with  isolated (asymptomatic) eosinophilia (IE) that develops during antibiotic therapy. We do know that the majority of patients with IE may never develop hypersensitivity reaction such as rash, renal or liver injuries, but predicting who will or will not get HSRs is a challenge.1-3 Couple of studies may help us in our decision making, however.

In a 2015 study1 involving patients receiving outpatient parenteral antibiotics, eosinophilia was present in 25% of patients during their course of treatment, of whom 30% subsequently developed HSR and 5% developed more than 1 sign of HSR. Patients with IE and subsequent HSR developed eosinophilia earlier in their course of treatment (median 11 vs 17 days) and had a higher peak absolute eosinophil count (~ 850 vs ~700/ ml).  The authors suggested that close monitoring for rash and renal injury in patient with IE during antibiotic therapy be considered, and that medication changes may be necessary when IE is associated with earlier onset of eosinophilia or higher absolute eosinophil count.

In a 2017 prospective study2 of patients with eosinophilic drug reactions (~20% related to antibiotics), the majority (56%) were asymptomatic. Earlier onset of eosinophilia and higher eosinophil count were associated with symptomatic eosinophilia, similar to the aforementioned study. The frequency of patients with IE who went on to have symptomatic eosinophilia when the suspect drug was continued vs those in whom it was not continued remains unclear from these studies.

Ultimately, the decision to continue or discontinue a suspect antibiotic when your patient has new-onset IE should be made on a case-by-case basis, taking into account the severity of the patient’s infection, availability of equally effective and tolerated alternative drugs and the ability to closely monitor for symptomatic disease. The timing of onset of eosinophilia and its peak absolute count may also play a role.

Bonus pearl: Did you know that only 18% of inpatients with cutaneous drug eruptions may have peripheral eosinophilia?4

The author acknowledges the invaluable input of Kimberly Blumenthal, MD in composing this pearl.

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  1. Blumenthal KG, Youngster I, Rabideau DJ, et al. Peripheral blood eosinophilia and hypersensitivity reactions among patients receiving outpatient parenteral antibiotics. J Allergy Clin Immunol 2015;136:1288.1294. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4640981/
  2. Ramirez E, Mdrano-Casique N, Tong HY, et al. Eosinophilic drug reactions detected by a prospective pharmacovigilance programme in a tertiary hospital. Br J Pharmacol 2017;83:400-15. https://bpspubs.onlinelibrary.wiley.com/doi/pdf/10.1111/bcp.13096
  3. Rauscher C, Freeman A. Drug-induced eosinophilia. Allergy Asthma Proc 2018;39:252-56. https://www.ncbi.nlm.nih.gov/pubmed/29669671
  4. Romagosa R, Kapoor S, Sanders J, et al. inpatient adverse cutaneous drug erutpions and eosinophilia. Arch Dermatol 2001; 137:511-12. https://www.ncbi.nlm.nih.gov/pubmed/11295947   



My patient has developed isolated eosinophilia without symptoms while receiving an antibiotic. Should I consider discontinuing the antibiotic or can I just continue it as long as she has no symptoms?

My elderly patient with abdominal pain has a negative Murphy’s sign on physical exam. How accurate is Murphy’s sign in diagnosing cholecystitis?

Not as accurate as we might like! In fact, no single clinical finding has been found to carry sufficient weight in ruling in or excluding cholecystitis and Murphy’s sign (inability to take a deep breath due to pain upon palpation of the right upper quadrant) is no exception. 1

A meta-analysis of patients with Murphy’s sign reported a sensitivity of 65% and a specificity of 87% (positive LR 2.8, negative LR 0.4, with 95% C.I. including 1.0 in both). 1,2  However, among the elderly (mean age 79 y), the sensitivity may be a slow as 48% 2 and in patients with gangrenous cholecystitis as low as 33%.3  

In contrast, Murphy’ s sign elicited at the time of ultrasound of the gallbladder (ie,“sonographic Murphy’s) is generally thought to very sensitive  (>90%) for acute cholecystitis;3,4 1 study reported a sensitivity of 63%, however (specificity 94%).5  Remember that altered mental status may also mask sonographic Murphy’s sign. 

Indirect fist percussion of the liver has been suggested by some authors as a more sensitive alternative to Murphy’s sign (100% vs 80%) in a small series of patients with cholecystitis.2

Bonus pearl: Did you know that another technique originally described by the famed American surgeon, John Murphy, to diagnose acute cholecystitis consisted of the “hammer stroke maneuver” in which percussion of the right midsubcostal region with the bent middle finger of the left hand was performed using the right hand to strike the dorsum of the left hand with hammer-like blows? 6

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  1. Trowbridge RL, Rutkowski NK, Shojania KG. Does this patient have acute cholecystitis. JAMA 2003;289:80-86. https://jamanetwork.com/journals/jama/article-abstract/195707
  2. Ueda T, Ishida E. Indirect fist percussion of the liver is a more sensitive technique for detecting hepatobiliary infections than Murphy’s sign. Current Gerontol Geriat Res, Volume 2015, Article ID 431638. https://www.hindawi.com/journals/cggr/2015/431638/
  3. Simeone JF, Brink JA, Mueller PR, et al. The sonographic diagnosis of acute gangrenous cholecystitis. The importance of the Murphy sign. AJR 1989;152:289-90. https://www.ncbi.nlm.nih.gov/pubmed/2643262
  4. O’Connor OJ, Maher MM. Imaging of cholecystitis. AJR 2011;196:W36774. https://www.ajronline.org/doi/full/10.2214/AJR.10.4340
  5. Rallis PW, Lapin SA, Quinn MF, et al. Prospective evaluation of the sonographic Murphy sign in suspected acute cholecystitis. J Clin Ultrasound 1982;10:113-5. https://www.ncbi.nlm.nih.gov/pubmed/6804512
  6. Salati SA, al Kadi A. Murphy’s sign of cholecystitis-a brief revisit. Journal of Signs and Symptoms 2012;1:53-6. https://www.researchgate.net/publication/230820198_Murphy’s_sign_of_cholecystitis-_a_brief_revisit



My elderly patient with abdominal pain has a negative Murphy’s sign on physical exam. How accurate is Murphy’s sign in diagnosing cholecystitis?

My patient with history of gastric bypass surgery now presents with right upper quadrant pain and gallstones. Is there a connection between gastric bypass surgery and gallstones?

An increased risk of new gallstones following gastric bypass surgery (GBS) has been reported by several studies (1-5).  More specifically, a study involving patients with baseline normal gallbladder ultrasound found that at 6 months following GBS 36% of patients developed gallstones and 13% developed sludge (4).  Similarly, a gallstone formation rate of 32% has been reported after GBS among patients who did not receive prophylactic treatment (5). 

New cholelithiasis following GBS may be largely attributed to rapid weight loss following this procedure, not the surgery itself or its related anatomical changes. Of interest, rapid weight loss, even by dieting, has been shown to increase the risk of gallstones (6).

However, overweight patients also have an increased risk of developing cholelithiasis at baseline, in part related to increased cholesterol secretion resulting in bile supersaturation with cholesterol (1).  Though weight loss may be expected to decrease this risk, rapid weight loss is thought to change the bile composition towards higher concentrations of calcium and cholesterol and increased production of gallbladder mucin, contributing to the pathogenicity of gallstone formation (5). 

In light of these findings, some have recommended routine prophylactic cholecystectomy as part of the GBS (7,8),  while others have argued against it (9,10), largely due to different observed rates of post-GBS symptomatic gallstones requiring cholecystectomies in various studies. Of note, post-operative ursodiol (ursodeoxycholic acid) may also reduce the incidence of post-GBS cholelithiasis (5,11). 

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1. Everhart JE. Contributions of obesity and weight loss to gallstone disease. Ann Intern Med 1993;119(10):1029–35. https://www.ncbi.nlm.nih.gov/pubmed/8214980
2. Wudel LJ, Wright JK, Debelak JP, Allos TM, Shyr Y, Chapman WC. Prevention of gallstone formation in morbidly obese patients undergoing rapid weight loss: Results of a randomized controlled pilot study. J Surg Res 2002;102(1):50–6. https://www.ncbi.nlm.nih.gov/pubmed/11792152
3. Manatsathit W, Leelasincharoen P, Al-Hamid H, Szpunar S, Hawasli A. The incidence of cholelithiasis after sleeve gastrectomy and its association with weight loss: A two-centre retrospective cohort study. Int J Surg [Internet] 2016;30:13–8. Available from: http://dx.doi.org/10.1016/j.ijsu.2016.03.060 https://www.ncbi.nlm.nih.gov/pubmed/27063855
4. Shiffman M, Sugerman H, Kellum J, Brewer W, Moore E. Gallstone formation after rapid weight loss: a prospective study in patients undergoing gastric bypass surgery for treatment of morbid obesity. Am J Gastroenterol 1991;(86):1000–5. https://www.ncbi.nlm.nih.gov/pubmed/1858735
5. Sugerman H, Brewer W, Shiffman M, et al. A Multicenter, Placebo-Controlled, Randomized, Double-Blind, Prospective Trial of Prophylactic Ursodiol for the Prevention of Gallstone Formation Rapid Weight Loss. Am Jourmal Surg 1995;169(January):91–7. https://www.ncbi.nlm.nih.gov/pubmed/7818005

6. de Oliverira CIB, Chaim EA, da Silva BB. Impact of rapid weight reduction on risk of cholelithiasis after bariatric surgery. Obesity Surgery 2003;13:625-8.
7. Tarantino I, Warschkow R, Steffen T, Bisang P, Schultes B, Thurnheer M. Is routine cholecystectomy justified in severely obese patients undergoing a laparoscopic Roux-en-Y gastric bypass procedure? A comparative cohort study. Obes Surg 2011;21(12):1870–8. https://reference.medscape.com/medline/abstract/21863228
8. Amstutz S, Michel JM, Kopp S, Egger B. Potential Benefits of Prophylactic Cholecystectomy in Patients Undergoing Bariatric Bypass Surgery. Obes Surg 2015;25(11):2054–60. https://link.springer.com/article/10.1007%2Fs11695-015-1650-6
9. Karadeniz M, Gorgun M, Kara C. The evaluation of gallstone formation in patients undergoing Roux-en -Y gastric bypass due to morbid obesity. Turkish J Surg 2014;30(2):76–9. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4379817/
10. D’Hondt M, Sergeant G, Deylgat B, Devriendt D, Van Rooy F, Vansteenkiste F. Prophylactic Cholecystectomy, a Mandatory Step in Morbidly Obese Patients Undergoing Laparoscopic Roux-en-Y Gastric Bypass? J Gastrointest Surg 2011;15(9):1532–6. https://www.ncbi.nlm.nih.gov/pubmed/21751078
11. Miller K, Hell E, Lang B, Lengauer E. Gallstone Formation Prophylaxis after Gastric Restrictive Procedures for Weight Loss: A Randomized Double-Blind Placebo-Controlled Trial. Ann Surg 2003;238(5):697–702. https://www.ncbi.nlm.nih.gov/pubmed/14578732

Contributed by Kim Schaefer, Harvard medical student, Boston, MA. 


My patient with history of gastric bypass surgery now presents with right upper quadrant pain and gallstones. Is there a connection between gastric bypass surgery and gallstones?

Why does my patient with alcoholic cirrhosis have macrocytic anemia?

Macrocytic anemia is commonly due to folate or vitamin B12 (cobalamin) deficiency.1 Deficiency in these vitamins can be related broadly to poor intake, poor absorption, or drug interference. In patients with chronic excess alcohol consumption, both intake and/or absorption of these vitamins may be affected.

Although folate deficiency is increasingly rare in many developed countries due to mandatory folate fortification of flour and uncooked-grain, alcohol use can be associated with malnourishment severe enough to causes folate deficiency. In addition, alcohol itself can alter folate metabolism and absorption.  More specifically, chronic alcohol consumption has been shown to be associated with decreased folate absorption by the small intestine, altered intrahepatic processing and distribution between the systemic and enterohepatic folate circulations as well as increased folate urinary excretion. 2 Though uncommon,3 alcohol can also be associated with a food B12 malabsorption process, whereby despite adequate intake, B12 is not released or absorbed from food. 4

But what if serum folate and B12 levels return as normal in our patient with macrocytosis? It turns out that alcohol consumption, independent of folate or B12 deficiency, may also cause macrocytosis. 5 Though the exact mechanism is unknown, it may be related to alcohol’s direct toxicity or that of its metabolites; alcohol is oxidized to acetaldehyde, which affects membranes of red blood cells (RBCs) and their precursors by forming adducts with erythroid proteins,6 and interfering with cell division.7 Interestingly, alcohol-related macrocytosis may appear before anemia is detected and can resolve within 2-4 months of abstinence.

In addition to alcohol, cirrhosis itself may be associated with macrocytic anemia caused by lipid deposition on RBC membranes.1

See also a related pearl at  https://pearls4peers.com/2019/07/26/my-patient-with-anemia-has-an-abnormally-high-mean-red-blood-cell-corpuscular-volume-mcv-what-conditions-should-i-routinely-consider-as-a-cause-of-his-macrocytic-anemia   


  1. Hoffbrand V, Provan D. ABC of clinical haematology: macrocytic anaemias. BMJ 2011;314(7078):430–430. https://www.ncbi.nlm.nih.gov/pubmed/9040391
  2. Medici V, Halsted CH. Folate, alcohol, and liver disease. Mol Nutr Food Res 2013;57(4):596–606. https://www.ncbi.nlm.nih.gov/pubmed/23136133
  3. Bode C, Bode CJ. Effect of alcohol consumption on the gut. Best Pract Res Clin Gastroenterol [Internet] 2003;17(4):575–92. https://www.sciencedirect.com/science/article/pii/S1521691803000349
  4. Dali-Youcef N, Andrès E. An update on cobalamin deficiency in adults. QJM 2009;102(1):17–28. https://academic.oup.com/qjmed/article/102/1/17/1502492
  5. Savage DG, Ogundipe A, Allen RH, Stabler SP, Lindenbaum J. Etiology and diagnostic Evaluation of macrocytosis. Am J Med Sci [Internet] 2000;319(6):343–52. http://dx.doi.org/10.1016/S0002-9629(15)40772-4 https://www.ncbi.nlm.nih.gov/pubmed/10875288
  6. Latvala J, Parkkila S, Melkko J, Niemelä O. Acetaldehyde adducts in blood and bone marrow of patients with ethanol-induced erythrocyte abnormalities. Mol Med 2001;7(6):401–5. https://www.ncbi.nlm.nih.gov/pubmed/11474133
  7. Wickramasinghe SN, Malik F. Acetaldehyde causes a prolongation of the doubling time and an increase in the modal volume of cells in culture. Alcohol Clin Exp Res 1986;10(3):350–4. https://www.ncbi.nlm.nih.gov/pubmed/3526962


Contributed by Kim Schaefer, Harvard medical student, Boston, MA

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Why does my patient with alcoholic cirrhosis have macrocytic anemia?

Is there a connection between my patient’s blood type and risk of thromboembolic events?

There seems to be, given the weight of the evidence to date suggesting that non-blood group O may be associated with non-valvular atrial fibrillation (NVAF)-related peripheral cardioembolic complications, myocardial infarction (MI) and ischemic stroke. 1-4

A 2015 retrospective Mayo Clinic study involving patients with NVAF adjusted for CHADS2 score found significantly lower rate of peripheral embolization in those with blood group O compared to those with other blood groups combined (3% vs 2%, O.R. 0.66, 95% CI, 0.5-0.8); rates of cerebral thromboembolic events were not significantly different between the 2 groups, however. 1

A 2008 systematic review and meta-analysis of studies spanning over 45 years reported a significant association between non-O blood group and MI, peripheral vascular disease, cerebral ischemia of arterial origin, and venous thromboembolism.2 Interestingly, the association was not significant for angina pectoris or for MI when only prospective studies were included.  Some studies have reported that the association between VWF and the risk of cardiovascular mortality may be independent of blood group. 5,6

Although the apparent lower risk of thromboembolic conditions in O blood group patients may be due to lower levels of von Willebrand factor (VWF) and factor VIII in this population 1,4, other pathways likely  play a role.7  

As for why the rate of peripheral (but not cerebral) thromboembolic events in NVAP is affected by blood group, it is suggested that, because of their size, larger clots (facilitated by lower VWF levels) may bypass the carotid and vertebral orifices in favor of their continuation downstream to the “peripheral bed”.1

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  1. Blustin JM, McBane RD, Mazur M, et al. The association between thromboembolic complications and blood group in patients with atrial fibrillation. Mayo Clin Proc 2015;90;216-23. https://www.sciencedirect.com/science/article/abs/pii/S002561961401043X
  2. Wu O, Bayoumi N, Vickers MA, et al. ABO (H) groups and vascular disease: a systematic review and meta-analysis. J Thromb Haemostasis 2008;6:62-9. https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1538-7836.2007.02818.x
  3. Medalie JH, Levene C, Papier C, et al. Blood groups, myocardial infarction, and angina pectoris among 10,000 adult males. N Engl J Med 1971;285:1348-53. https://www.nejm.org/doi/pdf/10.1056/NEJM197112092852404
  4. Franchini M, Capra F, Targher G, et al. Relationship between ABO blood group and von Willebrand factor levels: from biology to clinical implications. Thrombosis Journal 2007, 5:14. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2042969/
  5. Meade TW, Cooper JA, Stirling Y, et al. Factor VIII, ABO blood group and the incidence of ischaemic heart disease. Br J Haematol 1994;88:601-7. https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2141.1994.tb05079.x
  6. Jager A, van Hinsbergh VW, Kostense PJ, et al. von Willebrand factor, C-reactive protein, and 5-year mortality in diabetic and nondiabetic subjects: the Hoorn Study. Arterioscl Thromb Vasc Biol 1999;19:3071-78. https://www.researchgate.net/publication/12709043_von_Willebrand_Factor_C-Reactive_Protein_and_5-Year_Mortality_in_Diabetic_and_Nondiabetic_Subjects_The_Hoorn_Study
  7. Sode BF, Allin KH, Dahl M, et al. Risk of venous thromboembolism and myocardial infarction associated with factor V Leiden and prothrombin mutations and blood type. CMAJ 2013.DOI:10.1503/cmaj.121636. https://www.ncbi.nlm.nih.gov/pubmed/23382263
Is there a connection between my patient’s blood type and risk of thromboembolic events?

Should I routinely treat my patients with acute COPD exacerbation with antibiotics?

The answer is “NO”! With an estimated 20% to 50% of acute chronic obstructive pulmonary disease (COPD) exacerbations attributed to noninfectious factors (1,2), routine inclusion of antibiotics in the treatment of this condition is not only unnecessary but potentially harmful.

Although the Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines recommends the use of antibiotics in patients who have dyspnea, increased sputum volume, and increased sputum purulence—or at least 2 of these 3 criteria when sputum purulence is one of them (3)—, these recommendations are not based on robust evidence and have not been widely corroborated (2,4-6).

That’s why the findings of a 2019 New England Journal of Medicine study (PACE) supporting the use of serum C-reactive protein (CRP) as an adjunctive test in COPD exacerbation is particularly welcome (1). In this multicenter randomized controlled trial performed in the U.K., the following CRP guidelines (arrived from prior studies) were provided to primary care clinicians to be used as part of their decision making in determining which patients with COPD exacerbation may not need antibiotic therapy:

• CRP less than 20 mg/L: Antibiotics unlikely to be beneficial
• CRP 20-40 mg/L: Antibiotics may be beneficial, mainly if purulent sputum is present
• CRP greater than 40 mg/L: Antibiotics likely to be beneficial

Adoption of these guidelines resulted in significantlly fewer patients being placed on antibiotics without evidence of harm over a 4-week follow-up period (1).  Despite its inherent limitations (eg, single country, outpatient setting), CRP testing may be a step in the right direction in curbing unnecessary use of antibiotics in COPD exacerbation.  


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1. Butler CC, Gillespie D, White P, et al. C-reactive protein testing to guide antibiotic prescribing for COPD exacerbations. N Engl J Med 2019;381:111-20. https://www.ncbi.nlm.nih.gov/pubmed/31291514
2. Llor C, Moragas A, Hernandez S, et al. Efficacy of antibiotic therapy for acute exacerbations of mild to moderate chronic obstructive pulmonary disease. Am J Respir Crit Care Med 2012;186:716-23. https://www.ncbi.nlm.nih.gov/pubmed/22923662
3. Global Initiative for Chronic Obstructive Lung Disease. Global strategy for the diagnosis, management, and prevention of chronic obstructive pulmonary disease. GOLD, 2019 (http://www.goldcopd.org).
4. Brett AS, Al-Hasan MN. COPD exacerbations—A target for antibiotic stewardship. N Engl J Med 2018;381:174-75. https://www.ncbi.nlm.nih.gov/pubmed/31291521
5. Miravitlles M, Moragas A, Hernandez S, et al. Is it possible to identify exacerbations of mild to moderate COPD that do not require antibiotic treatment? Chest 2013;144:1571-7. https://www.ncbi.nlm.nih.gov/pubmed/23807094
6. Van Vezen P, Ter Riet G, Bresser P, et al. Doxycycline for outpatient-treated acute exacerbations of COPD: a randomized double-blind placebo-controlled trial. Lancet Respir Med 2017;5:492-9. https://www.ncbi.nlm.nih.gov/pubmed/28483402

Should I routinely treat my patients with acute COPD exacerbation with antibiotics?

Should I routinely select antibiotics with activity against anaerobes in my patients with presumed aspiration pneumonia?

Anaerobes have been considered a major cause of aspiration pneumonia (AP) based on studies published in 1970’s (1-3). More recent data, however, suggest that anaerobes no longer play an important role in most cases of AP (4-7) and routine inclusion of specific anti-anaerobic drugs in their treatment is no longer necessary.

An important reason for anaerobes not playing an important role in AP in the current era is the change in the demographics of patients who may be affected. Patients reported in older studies often suffered from alcohol use disorder, drug ingestion, seizure disorders and acute cerebrovascular accident. In contrast, more recent data show that AP often occurs in nursing home residents, the elderly with cognitive impairment, and those with dysphagia, gastrointestinal dysmotility or tube feeding (8,9).

In addition, many cases of AP reported in older studies involved delay of 4 or more days before seeking medical attention and, not surprisingly, often presented with lung abscess, necrotizing pneumonia, empyema, or putrid sputum, features that are relatively rare in the current era.

Further supporting the diminishing role of anaerobes in AP, are recent microbiological studies of the respiratory tract in AP revealing the infrequent isolation of anaerobes and, even when isolated, often coexisting with aerobic bacteria. The latter observation is important because, due to the alteration in the redox potential (9,10), treatment of aerobic bacteria alone may lead to less oxygenation consumption and less favorable environment for survival of anaerobes in the respiratory tract.

We should also always consider the potential adverse effects of unnecessary antibiotics with anaerobic activity in our frequently debilitated patients, including gastrointestinal dysbiosis (associated with Clostridiodes difficile infections and overgrowth of antibiotic-resistant pathogens such as vancomycin-resistant enterococci (VRE), hypersensitivity reactions, drug interactions, and central nervous system toxicity (11,12).

Thus, the weight of the evidence does not justify routine anaerobic coverage of AP in today’s patients.


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1. Bartlett JG, Gorbach SL, Finegold SM. The bacteriology of aspiration pneumonia. Am J Med. 1974;56(2):202-7. https://www.ncbi.nlm.nih.gov/pubmed/4812076
2. Bartlett JG, Finegold SM. Anaerobic pleuropulmonary infections. Medicine (Baltimore). 1972;51(6):413-50. https://www.ncbi.nlm.nih.gov/pubmed/4564416
3. Bartlett JG, Gorbach SL. The triple threat of aspiration pneumonia. Chest. 1975;68(4):560-6. https://www.ncbi.nlm.nih.gov/pubmed/1175415
4. Finegold SM. Aspiration pneumonia. Rev Infect Dis. 1991;13 Suppl 9:S737-42. https://www.ncbi.nlm.nih.gov/pubmed/1925318
5. Bartlett JG. How important are anaerobic bacteria in aspiration pneumonia: when should they be treated and what is optimal therapy. Infect Dis Clin North Am. 2013;27(1):149-55. https://www.ncbi.nlm.nih.gov/pubmed/23398871
6. El-Solh AA, Pietrantoni C, Bhat A, Aquilina AT, Okada M, Grover V, et al. Microbiology of severe aspiration pneumonia in institutionalized elderly. Am J Respir Crit Care Med. 2003;167(12):1650-4. https://www.ncbi.nlm.nih.gov/pubmed/12689848
7. Marik PE, Careau P. The role of anaerobes in patients with ventilator-associated pneumonia and aspiration pneumonia: a prospective study. Chest. 1999;115(1):178-83. https://www.ncbi.nlm.nih.gov/pubmed/9925081
8. Bowerman TJ, Zhang J, Waite LM. Antibacterial treatment of aspiration pneumonia in older people: a systematic review. Clin Interv Aging. 2018;13:2201-13. https://www.ncbi.nlm.nih.gov/pubmed/30464429
9. Mandell LA, Niederman MS. Aspiration Pneumonia. N Engl J Med. 2019 Feb 14;380(7):651-663. doi: 10.1056/NEJMra1714562. https://www.ncbi.nlm.nih.gov/pubmed/30763196
10. Walden, W. C., & Hentges, D. J. (1975). Differential effects of oxygen and oxidation-reduction potential on the multiplication of three species of anaerobic intestinal bacteria. Applied microbiology, 30(5), 781–785. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC187272/
11. Sullivan A, Edlund C, Nord CE. Effect of antimicrobial agents on the ecological balance of human microflora. Lancet Infect Dis. 2001;1(2):101-14. https://www.ncbi.nlm.nih.gov/pubmed/11871461
12. Bhalla A, Pultz NJ, Ray AJ, Hoyen CK, Eckstein EC, Donskey CJ. Antianaerobic antibiotic therapy promotes overgrowth of antibiotic-resistant, gram-negative bacilli and vancomycin-resistant enterococci in the stool of colonized patients. Infect Control Hosp Epidemiol. 2003;24(9):644-9. https://www.ncbi.nlm.nih.gov/pubmed/14510245


Contributed by Amar Vedamurthy, MD, MPH, Mass General Hospital, Boston, MA

Should I routinely select antibiotics with activity against anaerobes in my patients with presumed aspiration pneumonia?