Week 8 – FUO

“Fever of Unexplained Origin: Report on 100 Cases”

Medicine (Baltimore). 1961 Feb;40:1-30. [free full text]

In our modern usage, fever of unknown origin (FUO) refers to a persistent unexplained fever despite an adequate medical workup. The most commonly used criteria for this diagnosis stem from the 1961 series by Petersdorf and Beeson.

This study analyzed a prospective cohort of patients evaluated at Yale’s hospital for FUO between 1952 and 1957. Their FUO criteria: 1) illness of more than three week’s duration, 2) fever higher than 101º F on several occasions, and 3) diagnosis uncertain after one week of study in hospital. After 126 cases had been noted, retrospective investigation was undertaken to determine the ultimate etiologies of the fevers. The authors winnowed this group to 100 cases based on availability of follow-up data and the exclusion of cases that “represented combinations of such common entities as urinary tract infection and thrombophlebitis.”

In 93 cases, “a reasonably certain diagnosis was eventually possible.” 6 of the 7 undiagnosed patients ultimately made a full recovery. Underlying etiologies (see table 1 on page 3) included: infectious 36% (with TB in 11%), neoplastic diseases 19%, collagen disease (e.g. SLE) 13%, pulmonary embolism 3%, benign non-specific pericarditis 2%, sarcoidosis 2%, hypersensitivity reaction 4%, cranial arteritis 2%, periodic disease 5%, miscellaneous disease 4%, factitious fever 3%, no diagnosis 7%.

Clearly, diagnostic modalities have improved markedly since this 1961 study. However, the core etiologies of infection, malignancy, and connective tissue disease/non-infectious inflammatory disease remain most prominent, while the percentage of patients with no ultimate diagnosis has been increasing (for example, see PMIDs 9413425, 12742800, and 17220753). Modifications to the 1961 criteria have been proposed (for example: 1 week duration of hospital stay not required if certain diagnostic measures have been performed) and implemented in recent FUO trials. One modern definition of FUO: fever ≥ 38.3º C, lasting at least 2-3 weeks, with no identified cause after three days of hospital evaluation or three outpatient visits. Per UpToDate, the following minimum diagnostic workup is recommended in suspected FUO: blood cultures, ESR or CRP, LDH, HIV, RF, heterophile antibody test, CK, ANA, TB testing, SPEP, and CT of abdomen and chest.

Further Reading/References:
1. “Fever of unknown origin (FUO). I A. prospective multicenter study of 167 patients with FUO, using fixed epidemiologic entry criteria. The Netherlands FUO Study Group.” Medicine (Baltimore). 1997 Nov;76(6):392-400.
2. “From prolonged febrile illness to fever of unknown origin: the challenge continues.” Arch Intern Med. 2003 May 12;163(9):1033-41.
3. “A prospective multicenter study on fever of unknown origin: the yield of a structured diagnostic protocol.” Medicine (Baltimore). 2007 Jan;86(1):26-38.
4. UpToDate, “Approach to the Adult with Fever of Unknown Origin”
5. “Robert Petersdorf, 80, Major Force in U.S. Medicine, Dies” The New York Times, 2006.

Summary by Duncan F. Moore, MD

Image Credit: by Menchi @ Wikimedia Commons, CC BY-SA 3.0

Week 7 – ARDSNet aka ARMA

“Ventilation with Lower Tidal Volumes as Compared with Traditional Tidal Volumes for Acute Lung Injury and the Acute Respiratory Distress Syndrome”

by the Acute Respiratory Distress Syndrome Network (ARDSNet)

N Engl J Med. 2000 May 4;342(18):1301-8. [free full text]

Acute respiratory distress syndrome (ARDS) is an inflammatory and highly morbid lung injury found in many critically ill patients. In the 1990s, it was hypothesized that overdistention of aerated lung volumes and elevated airway pressures might contribute to the severity of ARDS, and indeed some work in animal models supported this theory. Prior to the ARDSNet study, four randomized trials had been conducted to investigate the possible protective effect of ventilation with lower tidal volumes, but their results were conflicting.

The ARDSNet study enrolled patients with ARDS (diagnosed within 36 hours) to either a lower initial tidal volume of 6ml/kg, downtitrated as necessary to maintain plateau pressure ≤ 30 cm H2O, or to the “traditional” therapy of an initial tidal volume of 12 ml/kg, downtitrated as necessary to maintain plateau pressure ≤ 50 cm of water. The primary outcomes were in-hospital mortality and ventilator-free days within the first 28 days. Secondary outcomes included number of days without organ failure, occurrence of barotrauma, and reduction in IL-6 concentration from day 0 to day 3.

861 patients were randomized before the trial was stopped early due to the increased mortality in the control arm noted during interim analysis. In-hospital mortality was 31.0% in the lower tidal volume group and 39.8% in the traditional tidal volume group (p = 0.007, NNT = 11.4). Ventilator free days were 12±11 in the lower tidal volume group vs. 10±11 in the traditional group (n = 0.007). The lower tidal volume group had more days without organ failure (15±11 vs. 12±11, p = 0.006). There was no difference in rates of barotrauma among the two groups. Decrease in IL-6 concentration between days 0 and 3 was greater in the low tidal volume group (p < 0.001), and IL-6 concentration at day 3 was lower in the low tidal volume group (p = 0.002).

In summary, low tidal volume ventilation decreases mortality in ARDS relative to “traditional” tidal volumes. The authors felt that this study confirmed the results of prior animal models and conclusively answered the question of whether or not low tidal volume ventilation provided a mortality benefit. In fact, in the years following, low tidal volume ventilation became the standard of care, and a robust body of literature followed this study to further delineate a “lung-protective strategy.” Critics of the study noted that, at the time of the study, the “traditional” (standard of care) tidal volume in ARDS was less than the 12 ml/kg used in the comparison arm. (Non-enrolled patients at the participating centers were receiving a mean tidal volume of 10.3 ml/kg.) Thus not only was the trial making a comparison to a faulty control, but it was also potentially harming patients in the control arm. An excellent summary of the ethical issues and debate regarding this specific issue and regarding control arms of RCTs in general can be found here.

Corresponding practice point from Dr. Sonti and Dr. Vinayak and their Georgetown Critical Care Top 40: “Low tidal volume ventilation is the standard of care in patients with ARDS (P/F < 300). Use ≤ 6 ml/kg predicted body weight, follow plateau pressures, and be cautious of mixed modes in which you set a tidal volume but the ventilator can adjust and choose a larger one.”

PulmCCM is an excellent blog, and they have a nice page reviewing this topic and summarizing some of the research and guidelines that have followed.

Further Reading/References:
1. Wiki Journal Club
2. 2 Minute Medicine
3. PulmCCM “Mechanical Ventilation in ARDS: Research Update”
4. Georgetown Critical Care Top 40, page 6
5. PulmCCM “In ARDS, substandard ventilator care is the norm, not the exception.” 2017.

Summary by Duncan F. Moore, MD

Photo Credit: Hanno H. Endres at de.wikipedia, CC BY-SA 3.0

Week 6 – SOLVD

“Effect of Enalapril on Survival in Patients with Reduced Left Ventricular Ejection Fractions and Congestive Heart Failure”

by the Studies of Left Ventricular Dysfunction (SOLVD) Investigators

N Engl J Med. 1991 Aug 1;325(5):293-302. [free full text]

Heart failure with reduced ejection fraction (HFrEF) is a very common and highly morbid condition. We now know that blockade of the renin-angiotensin-aldosterone system (RAAS) with an ACEi or ARB is a cornerstone of modern HFrEF treatment. The 1991 SOLVD trial played an integral part in demonstrating the benefit of and broadening the indication for RAAS blockade in HFrEF.

The trial enrolled patients with HFrEF and LVEF ≤ 35% who were already on treatment (but not on an ACEi) and had Cr ≤ 2.0 and randomized them to treatment with enalapril BID (starting at 2.5mg and uptitrated as tolerated to 20mg BID) or treatment with placebo BID (again, starting at 2.5mg and uptitrated as tolerated to 20mg BID). Of note, there was a single-blind run-in period with enalapril in all patients, followed by a single-blind placebo run-in period. Finally, the patient was randomized to his/her actual study drug in a double-blind fashion. The primary outcomes were all-cause mortality and death from or hospitalization for CHF. Secondary outcomes included hospitalization for CHF, all-cause hospitalization, cardiovascular mortality, and CHF-related mortality.

2569 patients were randomized. Follow-up duration ranged from 22 to 55 months. 510 (39.7%) placebo patients died during follow-up compared to 452 (35.2%) enalapril patients (relative risk reduction of 16% per log-rank test, 95% CI 5-26%, p = 0.0036). See Figure 1 for the relevant Kaplan-Meier curves. 736 (57.3%) placebo patients died or were hospitalized for CHF during follow-up compared to 613 (47.7%) enalapril patients (relative risk reduction 26%, 95% CI 18-34, p < 0.0001). Hospitalizations for heart failure, all-cause hospitalizations, cardiovascular deaths, and deaths due to heart failure were all significantly reduced in the enalapril group. 320 placebo patients discontinued the study drug versus only 182 patients in the enalapril group. Enalapril patients were significantly more likely to report dizziness, fainting, and cough. There was no difference in the prevalence of angioedema.

Treatment of HFrEF with enalapril significantly reduced mortality and hospitalizations for heart failure. The authors note that for every 1000 study patients treated with enalapril, approximately 50 premature deaths and 350 heart failure hospitalizations were averted. The mortality benefit of enalapril appears to be immediate and increases for approximately 24 months. Per the authors, “reductions in deaths and rates of hospitalization from worsening heart failure may be related to improvements in ejection fraction and exercise capacity, to a decrease in signs and symptoms of congestion, and also to the known mechanism of action of the agent – i.e., a decrease in preload and afterload when the conversion of angiotensin I to angiotensin II is blocked.” Strengths of this study include its double-blind, randomized design, large sample size, and long follow-up. The fact that the run-in period allowed for the exclusion prior to randomization of patients who did not immediately tolerate enalapril is a major limitation of this study.

Prior to SOLVD, studies of ACEi in HFrEF had focused on patients with severe symptoms. The 1987 CONSENSUS trial was limited to patients with NYHA class IV symptoms. SOLVD broadened the indication of ACEi treatment to a wider group of symptoms and correlating EFs. Per the current 2013 ACCF/AHA guidelines for the management of heart failure, ACEi/ARB therapy is a Class I recommendation in all patients with HFrEF in order to reduce morbidity and mortality.

Further Reading/References:
1. Wiki Journal Club
2. 2 Minute Medicine
3. Effects of enalapril on mortality in severe congestive heart failure – Results of the Cooperative North Scandinavian Enalapril Survival Study (CONSENSUS). 1987.
4. 2013 ACCF/AHA guideline for the management of heart failure: executive summary

Summary by Duncan F. Moore, MD

Week 5 – IDNT

“Renoprotective Effect of the Angiotensin-Receptor Antagonist Irbesartan in Patients with Nephropathy Due to Type 2 Diabetes”

aka the Irbesartan Diabetic Nephropathy Trial (IDNT)

N Engl J Med. 2001 Sep 20;345(12):851-60. [free full text]

Diabetes mellitus is the most common cause of ESRD in the US. In 1993, a landmark study in NEJM demonstrated that captopril (vs. placebo) slowed the deterioration in renal function in patients with T1DM. However, prior to this 2002 study, no study had addressed definitively whether a similar improvement in renal outcomes could be achieved with RAAS blockade in patients with T2DM. Irbesartan (Avapro) is an angiotensin II receptor blocker that was first approved in 1997 for the treatment of hypertension. Its marketer, Bristol-Meyers Squibb, sponsored this trial in hopes of broadening the market for its relatively new drug.

This trial randomized patients with T2DM, hypertension, and nephropathy (per proteinuria and elevated Cr) to treatment with either irbesartan, amlodipine, or placebo. The drug in each arm was titrated to achieve a target SBP ≤ 135, and all patients were allowed non-ACEi/non-ARB/non-CCB drugs as needed. The primary outcome was a composite of the doubling of serum Cr, onset of ESRD, or all-cause mortality. Secondary outcomes included individual components of the primary outcome and a composite cardiovascular outcome.

1715 patients were randomized. The mean blood pressure after the baseline visit was 140/77 in the irbesartan group, 141/77 in the amlodipine group, and 144/80 in the placebo group (p = 0.001 for pairwise comparisons of MAP between irbesartan or amlodipine and placebo). Regarding the primary composite renal endpoint, the unadjusted relative risk was 0.80 (95% CI 0.66-0.97, p = 0.02) for irbesartan vs. placebo, 1.04 (95% CI 0.86-1.25, p = 0.69) for amlodipine vs. placebo, and 0.77 (0.63-0.93, p = 0.006) for irbesartan vs. amlodipine. The groups also differed with respect to individual components of the primary outcome. The unadjusted relative risk of creatinine doubling was 33% lower among irbesartan patients than among placebo patients (p = 0.003) and was 37% lower than among amlodipine patients (p < 0.001). The relative risks of ESRD and all-cause mortality did not differ significantly among the groups. There were no significant group differences with respect to the composite cardiovascular outcome. Importantly, a sensitivity analysis was performed which demonstrated that the conclusions of the primary analysis were not impacted significantly by adjustment for mean arterial pressure achieved during follow-up.

In summary, irbesartan treatment in T2DM resulted in superior renal outcomes when compared to both placebo and amlodipine. This beneficial effect was independent of blood pressure lowering. This was a well-designed, double-blind, randomized, controlled trial. However, it was industry-sponsored, and in retrospect, its choice of study drug seems quaint. The direct conclusion of this trial is that irbesartan is renoprotective in T2DM. In the discussion of IDNT, the authors hypothesize that “the mechanism of renoprotection by agents that block the action of angiotensin II may be complex, involving hemodynamic factors that lower the intraglomerular pressure, the beneficial effects of diminished proteinuria, and decreased collagen formation that may be related to decreased stimulation of transforming growth factor beta by angiotensin II.” In September 2002, on the basis of this trial, the FDA broadened the official indication of irbesartan to include the treatment of type 2 diabetic nephropathy. This trial was published concurrently in NEJM with the RENAAL trial. RENAAL was a similar trial of losartan vs. placebo in T2DM and demonstrated a similar reduction in the doubling of serum creatinine as well as a 28% reduction in progression to ESRD. In conjunction with the original 1993 ACEi in T1DM study, these two 2002 ARB in T2DM studies led to the overall notion of a renoprotective class effect of ACEis/ARBs in diabetes. Enalapril and lisinopril’s patents expired in 2000 and 2002, respectively. Shortly afterward, generic, once-daily ACE inhibitors entered the US market. Ultimately, such drugs ended up commandeering much of the diabetic-nephropathy-in-T2DM market share for which irbesartan’s owners had hoped.

Further Reading/References:
1. “The effect of angiotensin-converting-enzyme inhibition on diabetic nephropathy. The Collaborative Study Group.” NEJM 1993.
2. CSG Captopril Trial @ Wiki Journal Club
3. IDNT @ Wiki Journal Club
4. IDNT @ 2 Minute Medicine
5. US Food and Drug Administration, New Drug Application #020757
6. RENAAL @ Wiki Journal Club
7. RENAAL @ 2 Minute Medicine

Summary by Duncan F. Moore, MD