Week 6 – Bicarbonate and Progression of CKD

“Bicarbonate Supplementation Slows Progression of CKD and Improves Nutritional Status”

J Am Soc Nephrol. 2009 Sep;20(9):2075-84. [free full text]

Metabolic acidosis is a common complication of advanced CKD. Some animal models of CKD have suggested that worsening metabolic acidosis is associated with worsening proteinuria, tubulointerstitial fibrosis, and acceleration of decline of renal function. Short-term human studies have demonstrated that bicarbonate administration reduces protein catabolism and that metabolic acidosis is an independent risk factor for acceleration of decline of renal function. However, until this 2009 study by de Brito-Ashurst et al., there were no long-term studies demonstrating the beneficial effects of oral bicarbonate administration on CKD progression and nutritional status.

The study enrolled CKD patients with CrCl 15-30ml/min and plasma bicarbonate 16-20 mEq/L and randomized them to treatment with either sodium bicarbonate 600mg PO TID (with protocolized uptitration to achieve plasma HCO3  ≥ 23 mEq/L) for 2 years, or to routine care. The primary outcomes were: 1) the decline in CrCl at 2 years, 2) “rapid progression of renal failure” (defined as decline of CrCl > 3 ml/min per year), and 3) development of ESRD requiring dialysis. Secondary outcomes included 1) change in dietary protein intake, 2) change in normalized protein nitrogen appearance (nPNA), 3) change in serum albumin, and 4) change in mid-arm muscle circumference.

134 patients were randomized, and baseline characteristics were similar among the two groups. Serum bicarbonate levels increased significantly in the treatment arm. (See Figure 2.) At two years, CrCl decline was 1.88 ml/min in the treatment group vs. 5.93 ml/min in the control group (p < 0.01). Rapid progression of renal failure was noted in 9% of intervention group vs. 45% of the control group (RR 0.15, 95% CI 0.06–0.40, p < 0.0001, NNT = 2.8), and ESRD developed in 6.5% of the intervention group vs. 33% of the control group (RR 0.13, 95% CI 0.04–0.40, p < 0.001; NNT = 3.8). Regarding nutritional status, dietary protein intake increased in the treatment group relative to the control group (p < 0.007). Normalized protein nitrogen appearance decreased in the treatment group and increased in the control group (p < 0.002). Serum albumin increased in the treatment group but was unchanged in the control group, and mean mid-arm muscle circumference increased by 1.5 cm in the intervention group vs. no change in the control group (p < 0.03).

In conclusion, oral bicarbonate supplementation in CKD patients with metabolic acidosis reduces the rate of CrCl decline and progression to ESRD and improves nutritional status. Primarily on the basis of this study, the KDIGO 2012 guidelines for the management of CKD recommend oral bicarbonate supplementation to maintain serum bicarbonate within the normal range (23-29 mEq/L). This is a remarkably cheap and effective intervention. Importantly, the rates of adverse events, particularly worsening hypertension and increasing edema, were unchanged among the two groups. Of note, sodium bicarbonate induces much less volume expansion than a comparable sodium load of sodium chloride.

In their discussion, the authors suggest that their results support the hypothesis of Nath et al. (1985) that “compensatory changes [in the setting of metabolic acidosis] such as increased ammonia production and the resultant complement cascade activation in remnant tubules in the declining renal mass [are] injurious to the tubulointerstitium.” The hypercatabolic state of advanced CKD appears to be mitigated by bicarbonate supplementation. The authors note that “an optimum nutritional status has positive implications on the clinical outcomes of dialysis patients, whereas [protein-energy wasting] is associated with increased morbidity and mortality.”

Limitations to this trial include its open-label, no-placebo design. Also, the applicable population is limited by study exclusion criteria of morbid obesity, overt CHF, and uncontrolled HTN.

Further Reading:
1. Nath et al. “Pathophysiology of chronic tubulo-interstitial disease in rats: Interactions of dietary acid load, ammonia, and complement component-C3” (1985)
2. KDIGO 2012 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease (see page 89)
3. UpToDate, “Pathogenesis, consequences, and treatment of metabolic acidosis in chronic kidney disease”

Summary by Duncan F. Moore, MD

Week 5 – Dexamethasone in Bacterial Meningitis

Streptococcus pneumoniae

“Dexamethasone in Adults With Bacterial Meningitis”

N Engl J Med 2002; 347:1549-1556 [free full text]

The current standard of care in the treatment of suspected bacterial meningitis in the developed world includes the administration of dexamethasone prior to or at the time of antibiotic initiation. The initial evaluation of this practice in part stemmed from animal studies, which demonstrated that dexamethasone reduced CSF concentrations of inflammatory markers as well as neurologic sequelae after meningitis. RCTs in the pediatric literature also demonstrated clinical benefit. The best prospective trial in adults was this 2002 study by de Gans et al.

The trial enrolled adults with suspected meningitis and randomized them to either dexamethasone 10mg IV q6hrs x4 days started 15-20 minutes before the first IV antibiotics or a placebo IV with the same administration schedule. The primary outcome was the Glasgow Outcome Scale at 8 weeks (1 = death, 2 = vegetative state, 3 = unable to live independently, 4 = unable to return to school/work, 5 = able to return to school/work). Secondary outcomes included death and focal neurologic abnormalities. Subgroup analyses were performed by organism.

301 patients were randomized. At 8 weeks, 15% of dexamethasone patients compared with 25% of placebo patients had an unfavorable outcome of Glasgow Outcome Scale score 1-4 (RR 0.59, 95% CI 0.37 – 0.94, p= 0.03). Among patients with pneumococcal meningitis, 26% of dexamethasone patients compared with 52% of placebo patients had an unfavorable outcome. There was no significant difference among treatment arms within the subgroup of patients infected with meningococcal meningitis. Overall, death occurred in 7% of dexamethasone patients and 15% of placebo patients (RR 0.48, 95% CI 0.24 – 0.96, p = 0.04). In pneumococcal meningitis, 14% of dexamethasone patients died, and 34% of placebo patients died.  There was no difference in rates of focal neurologic abnormalities or hearing loss in either treatment arm (including within any subgroup).

In conclusion, early adjunctive dexamethasone improves mortality in bacterial meningitis. As noted in the above subgroup analysis, this benefit appears to be driven by the efficacy within the pneumococcal meningitis subgroup. Of note, the standard initial treatment regimen in this study was amoxicillin 2gm q4hrs for 7-10 days rather than our standard ceftriaxone + vancomycin +/- ampicillin. Largely on the basis of this study alone, the IDSA guidelines for the treatment of bacterial meningitis (2004) recommend dexamethasone 0.15 mg/kg q6hrs for 2-4 days with first dose administered 10-20 min before or concomitant with initiation of antibiotics. Dexamethasone should be continued only if CSF Gram stain, CSF culture, or blood cultures are consistent with pneumococcus.

References / Further Reading:
1. IDSA guidelines for management of bacterial meningitis (2004)
2. Wiki Journal Club
3. 2 Minute Medicine

Summary by Duncan F. Moore, MD

Image Credit: CDC / Dr. Richard Facklam, US Public Domain, via Public Health Image Library

Week 4 – ARDSNet

“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. ARDSNet @ Wiki Journal Club
2. ARDSNet @ 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


“Intensive versus Conventional Glucose Control in Critically Ill Patients”

by the Normoglycemia in Intensive Care Evaluation–Survival Using Glucose Algorithm Regulation (NICE-SUGAR) investigators

N Engl J Med 2009;360:1283-97. [free full text]

On the wards we often hear 180 mg/dL used as the upper limit of acceptable for blood glucose with the understanding that tighter glucose control in inpatients can lead to more harm than benefit. The relevant evidence base comes from ICU populations, with scant direct data in non-ICU patients. The 2009 NICE-SUGAR study is the largest and best among this evidence base.

The study randomized ICU patients (expected to require 3 or more days of ICU-level care) to either “intensive” glucose control (target glucose 81 to 108 mg/dL) or conventional glucose control (target of less than 180 mg/dL). The primary outcome was 90-day all-cause mortality.

6104 patients were randomized to the two arms, and both groups had similar baseline characteristics. 27.5% of patients in the intensive-control group died versus 24.9% in the conventional-control group (OR 1.14, 95% CI 1.02-1.28, p= 0.02). Severe hypoglycemia (< 40 mg/dL) was found in 6.8% of intensive patients but only 0.5% of conventional patients.

In conclusion, intensive glucose control increases mortality in ICU patients. The fact that only 20% of these patients had diabetes mellitus suggests that much of the hyperglycemia treated in this study (97% of intensive group received insulin, 69% of conventional) was from stress, critical illness, and corticosteroid use. For ICU patients, intensive insulin therapy is clearly harmful, but the ideal target glucose range remains controversial and by expert opinion appears to be 140-180. For non-ICU inpatients with or without diabetes mellitus, the ideal glucose target is also unclear – the ADA recommends 140-180, and the Endocrine Society recommends a pre-meal target of < 140 and random levels < 180.

References / Further Reading:
1. ADA Standards of Medical Care in Diabetes 2016 (skip to page S99)
2. NICE-SUGAR @ Wiki Journal Club

Summary by Duncan F. Moore, MD

Week 2 – CAST

“Mortality and Morbidity in Patients Receiving Encainide, Flecainide, or Placebo”

The Cardiac Arrhythmia Suppression Trial (CAST)

N Engl J Med. 1991 Mar 21;324(12):781-8. [full text]

Ventricular arrhythmias are common following MI, and studies have demonstrated that PVCs and other arrhythmias such as non-sustained ventricular tachycardia (NSVT) are independent risk factors for cardiac mortality following MI. As such, by the late 1980s, many patients with PVCs post-MI were treated with antiarrhythmic drugs in an attempt to reduce mortality. The 1991 CAST trial sought to prove what predecessor trials had failed to prove – that suppression of such rhythms post-MI would improve survival.

This trial took post-MI patients with PVCs (with no sustained VT) and reduced EF and randomized them to an open-label titration period in which encainide, flecainide, or moricizine was titrated to suppress at least 80% of the PVCs and 90% of the runs of NSVT. Patients were then either randomized to continuation of the antiarrhythmic drug assigned during the titration period or transitioned to a placebo. The primary outcome was death or cardiac arrest with resuscitation, “either of which was due to arrhythmia.”

The trial was terminated early due to increased mortality in the encainide and flecainide treatment groups. 1498 patients were randomized following successful titration during the open-label period, and they were reported in this paper. The results of the moricizine arm were reported later in a different paper (CAST-II). The RR of death or cardiac arrest due to arrhythmia was 2.64 (95% CI 1.60–4.36; number needed to harm = 28.2). See Figure 1 on page 783 for a striking Kaplan-Meier curve. The RR of death or cardiac arrest due to all causes was 2.38 (95% CI 1.59–3.57; NNH = 20.6). Regarding other secondary outcomes, cardiac death/arrest due to any cardiac cause was similarly elevated in the treatment group, and there were no significant differences in non-lethal endpoints among the treatment and placebo arms.

In this large RCT, the treatment of asymptomatic ventricular arrhythmias with encainide and flecainide in patients with LV dysfunction following MI resulted in increased mortality. This study provides a classic example of how a treatment that seems to make intuitive sense based on observational data can be easily and definitively disproven with a placebo-controlled trial with hard endpoints (e.g. death). Although PVCs and NSVT are associated with cardiac death post-MI and reducing these arrhythmias might seem like an intuitive strategy for reducing death, correlation does not equal causation. Modern expert opinion at UpToDate notes no role for suppression of asymptomatic PVCs or NSVT in the peri-infarct period. Indeed such suppression may increase mortality. As noted on Wiki Journal Club, modern ACC/AHA guidelines “do not comment on the use of antiarrhythmic medications in ACS care.”

Further Reading/References:
1. CAST @ Wiki Journal Club
2. CAST @ 2 Minute Medicine
3. CAST-I Trial @ ClinicalTrials.gov
4. CAST-II trial publication, NEJM 1992
5. UpToDate “Clinical features and treatment of ventricular arrhythmias during acute myocardial infarction”

Summary by Duncan F. Moore, MD

Week 1 – CLOT

“Low-Molecular-Weight Heparin versus a Coumarin for the Prevention of Recurrent Venous Thromboembolism in Patients with Cancer”

by the Randomized Comparison of Low-Molecular-Weight Heparin versus Oral Anticoagulant Therapy for the Prevention of Recurrent Venous Thromboembolism in Patients with Cancer (CLOT) Investigators

N Engl J Med. 2003 Jul 10;349(2):146-53. [free full text]

Malignancy is a pro-thrombotic state, and patients with cancer are at significant and sustained risk of venous thromboembolism (VTE) even when treated with warfarin. Warfarin is a suboptimal drug that requires careful monitoring, and its effective administration is challenging in the setting of cancer-associated difficulties with oral intake, end-organ dysfunction, and drug interactions. The 2003 CLOT trial was designed to evaluate whether treatment with low-molecular-weight heparin (LMWH) was superior to treatment with a vitamin K antagonist (VKA) in the prevention of recurrent VTE.

The study randomized adults with active cancer and newly diagnosed symptomatic DVT or PE to treatment with either dalteparin subQ daily (200 IU/kg daily x1 month, then 150 IU/kg daily x5 months) or a vitamin K antagonist x6 months (target INR 2.5, with 5-7 day LMWH bridge). The primary outcome was the recurrence of symptomatic DVT or PE within 6 months of follow-up. Secondary outcomes included major bleed, any bleeding, and all-cause mortality.

338 patients were randomized to the LMWH group, and 338 were randomized to the VKA group. Baseline characteristics were similar among the two groups. 90% of patients had solid malignancies, and 67% of patients had metastatic disease. Within the VKA group, INR was estimated to be therapeutic 46% of the time, subtherapeutic 30% of the time, and supratherapeutic 24% of the time. Within the six-month follow-up period, symptomatic VTE occurred in 8.0% of the dalteparin group and 15.8% of the VKA group (HR 0.48, 95% CI 0.30-0.77, p=0.002; NNT = 12.9). The Kaplan-Meier estimate of recurrent VTE at 6 months was 9% in the dalteparin group and 17% in the VKA group. 6% of the dalteparin group developed major bleeding versus 6% of the VKA group (p = 0.27). 14% of the dalteparin group sustained any type of bleeding event versus 19% of the VKA group (p = 0.09). Mortality at 6 months was 39% in the dalteparin group versus 41% in the VKA group (p = 0.53).

In summary, treatment of VTE in cancer patients with low-molecular-weight heparin reduced the incidence of recurrent VTE relative to the incidence following treatment with vitamin K antagonists. Notably, this reduction in VTE recurrence was not associated with a change in bleeding risk. However, it also did not correlate with a mortality benefit either. This trial initiated a paradigm shift in the treatment of VTE in cancer. LMWH became the standard of care, although cost and convenience may have limited access and adherence to this treatment.

Until recently, no trial had directly compared a DOAC to LMWH in the prevention of recurrent VTE in malignancy. In an open-label, noninferiority trial, the Hokusai VTE Cancer Investigators demonstrated that the oral Xa inhibitor edoxaban (Savaysa) was noninferior to dalteparin with respect to a composite outcome of recurrent VTE or major bleeding. The 2018 SELECT-D trial compared rivaroxaban (Xarelto) to dalteparin and demonstrated a reduced rate of recurrence among patients treated with rivaroxaban (cumulative 6-month event rate of 4% versus 11%, HR 0.43, 95% CI 0.19–0.99) with no difference in rates of major bleeding but increased “clinically relevant nonmajor bleeding” within the rivaroxaban group.

Further Reading/References:
1. CLOT @ Wiki Journal Club
2. CLOT @ 2 Minute Medicine
3. UpToDate, “Treatment of venous thromboembolism in patients with malignancy”
4. Hokusai VTE Cancer Trial @ Wiki Journal Club
5. “Edoxaban for the Treatment of Cancer-Associated Venous Thromboembolism,” NEJM 2017
6. “Comparison of an Oral Factor Xa Inhibitor With Low Molecular Weight Heparin in Patients With Cancer With Venous Thromboembolism: Results of a Randomized Trial (SELECT-D).” J Clin Oncol 2018.

Summary by Duncan F. Moore, MD

Image Credit: Westgate EJ and FitzGerald GA, CC BY 2.5, via Wikimedia Commons

Week 52 – Donor-Feces Infusion for Recurrent C. difficile

“Duodenal Infusion of Donor Feces for Recurrent Clostridium difficile

N Engl J Med. 2013 Jan 31;368(5):407-15. [free full text]

Clostridioides (formerly Clostridium) difficile infection (CDI) is a common, increasingly prevalent, and increasingly recurrent disease. As discussed in the 2017-2018 Academic Year Week 43 post, the IDSA/SHEA guidelines published March 2018 now list vancomycin PO as first line treatment for initial, non-severe CDI. These guidelines also list fecal microbiota transplantation (FMT) as an option for treatment of a second or subsequent recurrence of CDI. FMT received a rating of “Strong [recommendation] / Moderate [level of evidence]” for this indication thanks to this 2013 trial by van Nood et al. – the first prospective RCT to compare antibiotic therapy to FMT in recurrent CDI.

This single-academic-center (Netherlands), open-label, randomized controlled trial compared three regimens for the treatment of recurrent CDI. One treatment arm received vancomycin 500mg PO QID x4-5 days followed by bowel lavage and then infusion of donor feces through nasoduodenal tube, another treatment arm received a standard 14-day vancomycin 500mg PO QID regimen, and the final treatment arm received a standard 14-day vancomycin regimen with additional bowel lavage on day 4 or 5. The primary endpoint was cure without relapse by 10 weeks.

43 patients were randomized prior to the termination of the trial due to the markedly higher rates of recurrent CDI among patients who did not receive FMT. Regarding the primary outcome, 13 (81%) of the FMT group were cured after the first infusion (and remained so) at 10 weeks, whereas resolution of CDI occurred in only 4 (31%) of the vancomycin-alone group and in only 3 (23%) of the vancomycin + bowel lavage group (p < 0.001 for both pairwise comparisons vs. FMT).

In this randomized controlled trial, fecal microbiota transplantation was superior to both vancomycin and vancomycin plus bowel lavage in the cure of recurrent Clostridium difficile infection. Although this trial was small, its effect was enormous. As mentioned above, FMT is now recommended by guidelines for the treatment of multiply-recurrent CDI. FMT has been the subject of numerous published and ongoing trials, including this notable 2017 study by Kao et al. that demonstrated noninferiority of FMT delivered via oral capsules versus “conventional” colonoscopic delivery.

Further Reading/References:
1. Wiki Journal Club
2. 2 Minute Medicine
3. 2017 Update to IDSA/SHEA Clinical Practice Guidelines for Clostridium difficile Infection
4. Kao et. al, “Effect of Oral Capsule- vs Colonoscopy-Delivered Fecal Microbiota Transplantation on Recurrent Clostridium difficile Infection.” JAMA. 2017;318(20):1985-1993.
5. IDSA, “Fecal Microbiota Transplantation”
6. Food and Drug Administration, “Enforcement Policy Regarding Investigational New Drug Requirements for Use of Fecal Microbiota for Transplantation to Treat Clostridium difficile Infection Not Responsive to Standard Therapies”

Summary by Duncan F. Moore, MD

Image Credit: CDC/ Lois S. Wiggs (PHIL #6260), Public Domain, via Wikimedia Commons

Week 51 – Rifaximin Treatment in Hepatic Encephalopathy

“Rifaximin Treatment in Hepatic Encephalopathy”

N Engl J Med. 2010 Mar25;362(12):1071-81. [free full text]

As we are well aware at Georgetown, hepatic encephalopathy (HE) is highly prevalent among patients with cirrhosis, and admissions for recurrent HE place a significant burden on the medical system. The authors of this study note that HE is thought to result from “the systemic accumulation of gut-derived neurotoxins, especially ammonia, in patients with impaired liver function and portosystemic shunting.” Lactulose is considered the standard of care for the prevention of HE. It is thought to decrease the absorption of ammonia in the gut lumen through its cathartic effects and by alteration of colonic pH. The minimally absorbable oral antibiotic rifaximin is thought to further reduce ammonia production through direct antibacterial effects within the gut lumen. Thus the authors of this pivotal 2010 study sought to determine the additive effect of daily rifaximin prophylaxis in the prevention of HE.

The study enrolled adults with cirrhosis and 2+ episodes of overt HE during the past 6 months and randomized them to treatment with either rifaximin 550mg PO BID x6 months or placebo 550mg PO BID x6 months. The primary outcome was time to first breakthrough episode of HE (West Haven Score of 2+ or West Haven Score 0 –> 1 with worsening asterixis). Secondary outcomes included time to first hospitalization involving HE and adverse events, including those “possibly related to infection.”

299 patients were randomized. 140 and 159 patients were assigned to rifaximin and placebo, respectively. Baseline characteristics were similar among the two groups. Lactulose use prior to and during the study was similar in both groups at approximately 91%. Breakthrough HE occurred in 31 (22.1%) of the rifaximin patients and 73 (45.9%) of the placebo patients [HR 0.42, 95% CI 0.28-0.64, p<0.001, absolute risk reduction 23.7%, NNT = 4.2]. This result was consistent within all tested subgroups, except patients with MELD score 19-24 and patients who were not using lactulose at baseline. (See Figure 3.) Hospitalization involving HE occurred in 19 (13.6%) of the rifaximin patients and 36 (22.6%) of the placebo patients [HR 0.50, 95% CI 0.29-0.87, p = 0.01, absolute risk reduction 9.1%, NNT = 11.0]. There were no differences in adverse events among the two treatment groups.

Thus, prophylactic rifaximin reduced the incidence of recurrent HE and its resultant hospitalizations. This landmark trial showed a clear treatment benefit with implied savings in healthcare utilization costs associated with HE recurrences and hospitalizations. This marked effect was demonstrated even in the setting of relatively good (91%) lactulose adherence in both treatment arms prior to and throughout the trial.  On the day this trial was published in 2010, the FDA approved rifaximin for “reduction in risk of overt hepatic encephalopathy recurrence” in adults.

Because rifaximin is not generic and remains quite expensive, its financial utility is limited from an insurance company’s perspective. There is no other comparable nonabsorbable antibiotic for this indication. UpToDate suggests starting with lactulose therapy and then adding a nonabsorbable antibiotic, such as rifaximin, both for the treatment of overt HE and for the prevention of recurrent HE. In practice, most insurance companies will require a prior authorization for outpatient rifaximin treatment, but in my recent experience, this process has been perfunctory and easy.

Further Reading/References:
1. ClinicalTrials.gov, NCT00298038
2. FDA, NDA approval letter for Xifaxan (rifaximin)
3. UpToDate, “Hepatic encephalopathy in adults: Treatment”

Summary by Duncan F. Moore, MD

Week 50 – VERT

“Effects of Risedronate Treatment on Vertebral and Nonvertebral Fractures in Women With Postmenopausal Osteoporosis”

by the Vertebral Efficacy with Risedronate Therapy (VERT) Study Group

JAMA. 1999 Oct 13;282(14):1344-52. [free full text]

Bisphosphonates are a highly effective and relatively safe class of medications for the prevention of fractures in patients with osteoporosis. The VERT trial published in 1999 was a landmark trial that demonstrated this protective effect with the daily oral bisphosphonate risedronate.

The trial enrolled post-menopausal women with either 2 or more vertebral fractures per radiography or 1 vertebral fracture with decreased lumbar spine bone mineral density. Patients were randomized to the treatment arm (risedronate 2.5mg PO daily or risedronate 5mg PO daily) to the daily PO placebo control arm. Measured outcomes included: 1) the prevalence of new vertebral fracture at 3 years follow-up, per annual imaging, 2) the prevalence of new non-vertebral fracture at 3 years follow-up, per annual imaging, and 3) change in bone mineral density, per DEXA q6 months.

2458 patients were randomized. During the course of the study, “data from other trials indicated that the 2.5mg risedronate dose was less effective than the 5mg dose,” and thus the authors discontinued further data collection on the 2.5mg treatment arm at 1 year into the study. All treatment groups had similar baseline characteristics. 55% of the placebo group and 60% of the 5mg risedronate group completed 3 years of treatment. The prevalence of new vertebral fracture within 3 years was 11.3% in the risedronate group and 16.3% in the placebo group (RR 0.59, 95% CI 0.43-0.82, p = 0.003; NNT = 20). The prevalence of new non-vertebral fractures at 3 years was 5.2% in the treatment arm and 8.4% in the placebo arm (RR 0.6, 95% CI 0.39-0.94, p = 0.02; NNT = 31). Regarding bone mineral density (BMD), see Figure 4 for a visual depiction of the changes in BMD by treatment group at the various 6-month timepoints. Notably, change from baseline BMD of the lumbar spine and femoral neck was significantly higher (and positive) in the risedronate 5mg group at all follow-up timepoints relative to the placebo group and at all timepoints except 6 months for the femoral trochanter measurements. Regarding adverse events, there was no difference in the incidence of upper GI adverse events among the two groups. GI complaints “were the most common adverse events associated with study discontinuance,” and GI events lead to 42% of placebo withdrawals but only 36% of the 5mg risedronate withdrawals.

Oral risedronate reduces the risk of vertebral and non-vertebral fractures in patients with osteoporosis while increasing bone mineral density. Overall, this was a large, well-designed RCT that demonstrated a concrete treatment benefit. As a result, oral bisphosphonate therapy has become the standard of care both for treatment and prevention of osteoporosis. This study, as well as others, demonstrated that such therapies are well-tolerated with relatively few side effects. A notable strength of this study is that it did not exclude patients with GI comorbidities.  One weakness is the modification of the trial protocol to eliminate the risedronate 2.5mg treatment arm after 1 year of study. Although this arm demonstrated a reduction in vertebral fracture at 1 year relative to placebo (p = 0.02), its elimination raises suspicion that the pre-specified analyses were not yielding the anticipated results during the interim analysis and thus the less-impressive treatment arm was discarded.

Further Reading/References:
1. Weekly alendronate vs. weekly risedronate [https://www.ncbi.nlm.nih.gov/pubmed/15619680]
2. Comparative effectiveness of pharmacologic treatments to prevent fractures: an updated systematic review (2014) [https://www.ncbi.nlm.nih.gov/pubmed/25199883]

Summary by Duncan F. Moore, MD

Image Credit: Nick Smith, CC BY-SA 3.0, via Wikimedia Commons


“A Controlled Trial of Renal Denervation for Resistant Hypertension”

N Engl J Med. 2014 Apr 10;370(15):1393-401 [free full text]

Approximately 10% of patients with hypertension have resistant hypertension (SBP > 140 despite adherence to three maximally tolerated doses of antihypertensives, including a diuretic). Evidence suggests that the sympathetic nervous system plays a large role in such cases, so catheter-based radiofrequency ablation of the renal arteries (renal denervation therapy) was developed as a potential treatment for resistant HTN. The 2010 SYMPLICITY HTN-2 trial was a small (n=106), non-blinded, randomized trial of renal denervation vs. continued care with oral antihypertensives that demonstrated a remarkable 30-mmHg greater decrease in SBP with renal denervation. Thus the 2014 SYMPLICITY HTN-3 trial was designed to evaluate the efficacy of renal denervation in a single-blinded trial with a sham-procedure control group.

The trial enrolled adults with resistant HTN with SBP ≥ 160 despite adherence to 3+ maximized antihypertensive drug classes, including a diuretic. (Pertinent exclusion criteria included secondary hypertension, renal artery stenosis > 50%, prior renal artery intervention.) Patients were randomized to either renal denervation with the Symplicity (Medtronic) radioablation catheter or to renal angiography only (sham procedure). The primary outcome was the mean change in office systolic BP from baseline at 6 months. (The examiner was blinded to intervention.) The secondary outcome was the change in mean 24-hour ambulatory SBP at 6 months. The primary safety endpoint was a composite of death, ESRD, embolic event with end-organ damage, renal artery or other vascular complication, hypertensive crisis within 30 days, or new renal artery stenosis of > 70%.

535 patients were randomized. On average, patients were receiving five antihypertensive medications. There was no significant difference in reduction of SBP between the two groups at 6 months. ∆SBP was -14.13 ± 23.93 mmHg in the denervation group vs. -11.74 ± 25.94 mmHg in the sham-procedure group for a between-group difference of -2.39 mmHg (95% CI -6.89 to 2.12, p = 0.26 with a superiority margin of 5 mmHg). The change in 24-hour ambulatory SBP at 6 months was -6.75 ± 15.11 mmHg in the denervation group vs. -4.79 ± 17.25 mmHg in the sham-procedure group for a between-group difference of -1.96 mmHg (95% CI -4.97 to 1.06, p = 0.98 with a superiority margin of 2 mmHg). There was no significant difference in the prevalence of the composite safety endpoint at 6 months with 4.0% of the denervation group and 5.8% of the sham-procedure group reaching the endpoint (percentage-point difference of -1.9, 95% CI -6.0 to 2.2).

In patients with resistant hypertension, renal denervation therapy provided no reduction in SBP at 6-month follow-up relative to a sham procedure.

This trial was an astounding failure for Medtronic and its Symplicity renal denervation radioablation catheter. The magnitude of the difference in results between the non-blinded, no-sham-procedure SYMPLICITY HTN-2 trial and this patient-blinded, sham-procedure-controlled trial is likely a product of 1) a marked placebo effect of procedural intervention, 2) Hawthorne effect in the non-blinded trial, and 3) regression toward the mean (patients were enrolled based on unusually high BP readings that over the course of the trial declined to reflect a lower true baseline).

Currently, there is no role for renal denervation therapy in the treatment of HTN (resistant or otherwise). However, despite the results of SYMPLICITY HTN-3, other companies and research groups are assessing the role of different radioablation catheters in patients with low-risk essential HTN and with resistant HTN. (For example, see https://www.ncbi.nlm.nih.gov/pubmed/29224639.)

Further Reading/References:
2. UpToDate, “Treatment of resistant hypertension,” heading “Renal nerve denervation”

Summary by Duncan F. Moore, MD