Prevention of Contrast Nephropathy by Sodium Bicarbonate Versus Sodium Chloride and N-acetylcysteine
Prevention of Contrast Nephropathy by Sodium Bicarbonate Versus Sodium Chloride and N-acetylcysteine
The objective of this study is to assess the efficacy of sodium bicarbonate compared with
 sodium chloride and oral N-acetylcysteine (NAC ) pretreatment for prevention of contrast
 nephropathy in patients with advanced renal disease undergoing cardiac catheterisation.
PROTOCOL

 Prevention of Contrast Nephropathy by Sodium Bicarbonate Versus Sodium Chloride and
 N-Acetylcysteine

 Nephrology and Cardiology Services, Shaare Zedek Medical Center, Jerusalem

 1. Background and rationale

 The development of acute renal failure following cardiac catheterization has been
 recognized since the 1970's. The syndrome of acute renal failure following cardiac
 catheterization is presently felt to be due either to atheroembolic disease or what is
 now referred to as contrast induced nephropathy. Since the clinical course of each is
 different, it is now usually not difficult to diagnose acute contrast induced
 nephropathy.

 All protocols to prevent contrast nephropathy include the infusion of sodium chloride
 with or without oral N-acetylcysteine (NAC) pretreatment, although several recent
 meta-analyses raise some doubt about the efficacy of.

 Review of Shaare Zedek Medical Center experience from 2000 thru 2003 demonstrated a
 significant decrease in the incidence of acute contrast induced nephropathy after
 cardiac catheterization following the introduction of routine NAC usage. This effect was
 detected in a patients with mild renal insufficiency only (creatinine less than
 1.5mg/dl). Patients with higher plasma creatinines did not appear to benefit from NAC
 prophylaxis.

 A recent study demonstrated that preventive hydration with sodium bicarbonate was more
 effective than sodium chloride in patients undergoing radiographic procedures. However,
 in that study, there was no subdivision of the patients by severity of their kidney
 disease and it is not clear if sodium bicarbonate was as effective in patients with more
 severe kidney disease as in those with milder renal impairment. In addition the rate,
 duration and kind of fluids that were used for preventive hydration differed from that
 currently recommended.

 Because free radicals are postulated to mediate contrast induced nephropathy and their
 formation is promoted by an acidic environment, alkalinizing renal tubular fluid with
 bicarbonate may reduce renal injury by reducing free radial formation. NAC is also known
 to be a free radical scavenger but since this compound was relatively ineffective in
 preventing contrast nephropathy in our patients with moderate to severe renal impairment
 (plasma creatinine > 1.5 mg%), we postulate that sodium bicarbonate may be more
 effective in the prevention of contrast nephropathy in these high risk patients.

 The proposed study is designed to test the efficacy of preventive hydration with sodium
 bicarbonate versus sodium chloride and oral NAC pretreatment in patients with stable
 advanced renal insufficiency (CKD stage 3 and 4-GFR 15-60ml/min/1.73m2 calculated by
 MDRD formula) undergoing cardiac catheterization.

 2. Study objectives

 The objective of this study is to assess the efficacy of sodium bicarbonate compared
 with sodium chloride and NACpretreatment for prevention of contrast nephropathy in
 patients with advanced renal disease.

 3. Outcome measure

 The incidence of contrast induced nephropathy, defined as 25% or more increase in serum
 creatinine within 2 days of contrast administration, will be assessed.

 4. Study design

 This is a prospective, randomized, single center trial. Patients due to undergo cardiac
 catheterization either electively or following acute coronary syndromes will be eligible
 for inclusion. Elective patients will be admitted the day before the procedure. After
 baseline assessment and laboratory tests, they will be randomly assigned to one of two
 groups. One group will receive 12 hours infusion of 154 meq/l (0.9%) sodium chloride at
 a rate of 1ml/kg per hour before cardiac catheterization and NAC 600mg x 2/d PO the day
 before and the day of the procedure.

 The second group will receive 154meq/l sodium bicarbonate in 5% dextrose in water mixed
 by the nursing staff by adding 154 ml of 1000 meq/l sodium bicarbonate to 846 ml of 5%
 dextrose in water, slightly diluting the dextrose concentration to 4.23%.The initial IV
 bolus will be 3 ml/kg for one hour before cardiac catheterization. Following this bolus,
 patients will receive the same fluid at a rate of 1 ml/kg per hour during the contrast
 exposure and for 6 hours after the procedure.

 A basic panel of blood chemistries (Na, K, Cl, Ca, P, BUN, creatinine, total protein,
 albumin, complete blood count, pH, HCO3, pCO2 and O2 sat) will be obtained before the
 procedure and post-procedure day 1 and 2 and until any increase of serum creatinine is
 resolved. GFR will be calculated by MDRD formula in all patients before cardiac
 catheterization.

 5. Patient selection

 Patients will be identified as study candidates based on preliminary laboratory tests
 results. They will referred from the clinics of Shaare Zedek, Kupot Cholim and the
 inpatient services of Shaare Zedek Medical Center. Eligible patients include individuals
 aged 18 year or older with GFR 15-60ml/min calculated by MDRD formula, who were
 scheduled to undergo cardiac catheterization. During the randomized study, consecutive
 eligible patients scheduled for exposure to the nonionic radiographic contrast agent
 iopamidol (796 mOsm/kg H2O, 755 mg of iopamidol per milliliter, and 370 mg iodine per
 milliliter) will be considered for enrollment.

 6. Exclusion criteria

 i. Serum creatinine levels more than 8mg/dl or GFR less than 15ml/min

 ii. Change in serum creatinine levels of ³0.5mg/dl during the previous 24 hours.

 iii. Preexisting dialysis

 iv. Multiple myeloma.

 v. Pulmonary edema.

 vi. Uncontrolled hypertension (treated systolic blood pressure more than 160 mmHg, or
 diastolic blood pressure more than 100mmHg.)

 vii. Emergency catheterization.

 viii. Recent exposure to radiographic contrast (within two days of the study).

 ix. Allergy to radiocontrast.

 x. Pregnancy.

 xi. Administration of dopamine, mannitol or NAC before the study.

 7. Blinding

 The study will be completely blinded. The serum creatinine level will be determined in a
 fully blinded fashion by laboratory personnel. The investigators from the Nephrology
 service will analyze the laboratory data without knowledge of patient study groups. The
 patients will not know to which group they will be randomized. The investigators from
 the Cardiology service will know the patient study groups, but will not analyze the
 patients laboratory tests results.

 8. Study Methods

 Qualified patients who agree to enter the study will be assigned to 1 of 2 treatment
 groups based on a computer-generated randomization schedule. Patients allocated to the
 sodium chloride-NAC group will receive 154mEq/L of sodium chloride at a rate of 1ml/kg
 per hour for 12 hours before cardiac catheterization and NAC 600mgx2/d PO the day before
 and the day of the procedure. Patients allocated to the sodium bicarbonate group will
 receive 154 mEq/L of sodium bicarbonate in dextrose and H2O, mixed by the Nursing
 Service by adding 154 mL of 1000 mEq/L sodium bicarbonate to 846 mL of 5% dextrose in
 H2O, slightly diluting the dextrose concentration to 4.23%.

 After appropriate nursing evaluation and initial measurement of blood pressure and
 weight, the pre-contrast fluid will be administered. Patients allocated to the sodium
 chloride-NACgroup will receive 154 mEq/L of sodium chloride at a rate of 1ml/kg per hour
 for 12 hours before cardiac catheterization and NAC 600mgx2/d PO the day before and the
 day of the procedure The initial intravenous bolus in the NaHCO3 group will be 3 mL/kg
 per hour for 1 hour immediately before radiocontrast injection. Following this, patients
 will receive the same fluid at a rate of 1 mL/kg per hour during the contrast exposure
 and for 6 hours after the procedure. For patients weighing more than 110 kg, the initial
 fluid bolus and drip will be limited to those doses administered to a patient weighing
 110 kg. Diuretics will be routinely withheld on the day of contrast injection. A basic
 panel of blood chemistries (Na, K, Cl, Ca, P, BUN, creatinine, total protein, albumin,
 complete blood count, serum pH, HCO3, pCO2 and O2 sat)) will be obtained before the
 procedure and post-procedure days 1 and 2 and until any increase of serum creatinine is
 resolved. GFR will be calculated by MDRD formula before the procedure.

 9. Study End Points and Statistical Analysis

 The primary outcome measure is development of contrast-induced nephropathy, defined by
 an increase in serum creatinine of 25% or more within 2 days after cardiac
 catheterization. This definition is identical to that used in a recent large
 meta-analysis in contrast-induced nephropathy. Post-contrast creatinine will be assessed
 the mornings of days 1 and 2. The highest serum creatinine on post-contrast days 1 or 2
 will be used to calculate the change in serum creatinine (the primary end point).

 Before beginning the study, we estimated the sample size needed for the primary end
 point of contrast-induced nephropathy. Based on our own and other previous data, we
 assumed the development of contrast-induced renal failure in 15% of the sodium
 chloride-NAC group and 5 % of the sodium bicarbonate group. Analysis indicated that a
 sample size of 281 patients would be required to detect a statistically significant
 difference with a power of 80% (two tailed p = 0.05).

 Tests for significance will be conducted using the t test for continuous variables and
 c2 or Fisher exact test for categorical variables. All analyses will be conducted using
 SAS software version 8.2 (SAS Institute Inc, Cary, NC). Data will be expressed as mean
 (SD). All tests will be 2-tailed, with differences reported as significant if p <0.05.

 10. Feasibility of the study

 The average number of cardiac catheterizations performed in Shaare Zedek Medical Center
 is 25-30 procedures per week. A recent review of 30 consecutive cardiac catheterization
 patients showed that 8 would be eligible for enrollment in this protocol. Thus, it
 should take about 10-12 months to enroll the required number of patients.

 11. Safety

 The infusion of sodium bicarbonate and sodium chloride is safe. In the published sodium
 bicarbonate study bolus administration of hydration fluids caused a moderate increase in
 both systolic and diastolic blood pressure (mean 11mm Hg in the sodium chloride group
 and 14 mmHg in the sodium bicarbonate group.) No patients developed clinical heart
 failure or respiratory distress. Since the patients enrolled in our study should have
 controlled hypertension (patients with blood pressure more than 160/100 will be
 excluded) this mild elevation in blood pressure should not be problematic.

 12. Study significance

 Contrast induced nephropathy is a common complication of cardiac catheterizations.
 Prophylactic hydration with sodium chloride and NAC which is currently in use is less
 effective in patients with advanced renal disease and the observed incidence of acute
 contrast induced nephropathy is approximately 15%. In addition the use of this regimen
 requires preventive hospitalization and may be especially problematic in patients with
 chronic kidney disease when they require urgent cardiac catheterization. If preventive
 hydration with sodium bicarbonate is as effective or better than the currently used
 saline-NAC regimen, the pretreatment time for cardiac catheterization could be significantly
 shortened, hence permitting its usage before emergent procedure. Since emergent procedures
 preclude the use of current relatively long pretreatment regimens, bicarbonate could reduce
 the incidence of acute contrast induced nephropathy in this highly vulnerable group.
Inclusion Criteria:

 Eligible patients include individuals aged 18 year or older with GFR 15-60ml/min calculated
 by MDRD formula, who were scheduled to undergo cardiac catheterization. During the
 randomized study, consecutive eligible patients scheduled for exposure to the nonionic
 radiographic contrast agent iopamidol (796 mOsm/kg H2O, 755 mg of iopamidol per milliliter,
 and 370 mg iodine per milliliter) will be considered for enrollment.

 Exclusion Criteria:

 i. Serum creatinine levels more than 8mg/dl or GFR less than 15ml/min

 ii. Change in serum creatinine levels of ³0.5mg/dl during the previous 24 hours.

 iii. Preexisting dialysis

 iv. Multiple myeloma.

 v. Pulmonary edema.

 vi. Uncontrolled hypertension (treated systolic blood pressure more than 160 mmHg, or
 diastolic blood pressure more than 100mmHg.)

 vii. Emergency catheterization.

 viii. Recent exposure to radiographic contrast (within two days of the study).

 ix. Allergy to radiocontrast.

 x. Pregnancy.

 xi. Administration of dopamine, mannitol or NAC before the study.

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