Difference between revisions of "CT with IV contrast in low renal function"
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===Weight adjustment=== | ===Weight adjustment=== | ||
| − | The needed dose is proportional to the ''lean body weight'' of the patient. For contrast CT, this is optimally calculated by the Boer formula, using height and weight of the patient.<ref name="CarusoDe Santis2018">{{cite journal|last1=Caruso|first1=Damiano|last2=De Santis|first2=Domenico|last3=Rivosecchi|first3=Flaminia|last4=Zerunian|first4=Marta|last5=Panvini|first5=Nicola|last6=Montesano|first6=Marta|last7=Biondi|first7=Tommaso|last8=Bellini|first8=Davide|last9=Rengo|first9=Marco|last10=Laghi|first10=Andrea|title=Lean Body Weight-Tailored Iodinated Contrast Injection in Obese Patient: Boer versus James Formula|journal=BioMed Research International|volume=2018|year=2018|pages=1–6|issn=2314-6133|doi=10.1155/2018/8521893}}</ref> Taking this formula, the needed volume of IV contrast from the unadjusted volume given in the table above becomes: | + | The needed dose is proportional to the ''lean body weight'' of the patient. For contrast CT in obese individuals, this is optimally calculated by the Boer formula, using height and weight of the patient.<ref name="CarusoDe Santis2018">{{cite journal|last1=Caruso|first1=Damiano|last2=De Santis|first2=Domenico|last3=Rivosecchi|first3=Flaminia|last4=Zerunian|first4=Marta|last5=Panvini|first5=Nicola|last6=Montesano|first6=Marta|last7=Biondi|first7=Tommaso|last8=Bellini|first8=Davide|last9=Rengo|first9=Marco|last10=Laghi|first10=Andrea|title=Lean Body Weight-Tailored Iodinated Contrast Injection in Obese Patient: Boer versus James Formula|journal=BioMed Research International|volume=2018|year=2018|pages=1–6|issn=2314-6133|doi=10.1155/2018/8521893}}</ref> Taking this formula, the needed volume of IV contrast from the unadjusted volume given in the table above becomes: |
| − | *For men: Weight-adjusted volume = Unadjusted volume x ((0. | + | *For men: Weight-adjusted volume = Unadjusted volume x ((0.00723 × W) + (0.00474 × H) − 0.341) |
| − | *For women: Weight-adjusted volume = Unadjusted volume x ((0. | + | *For women: Weight-adjusted volume = Unadjusted volume x ((0.00583 × W) + (0.011 × H) − 1.12) |
, where W is body weight in kilograms and H is body height in centimeters. | , where W is body weight in kilograms and H is body height in centimeters. | ||
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'''Hydration''' by drinking or intravenous volume expander, either before or after contract administration, decreases the risk of contrast-induced nephropathy.<ref name="YangHiremath2013">{{cite journal|last1=Yang|first1=Xiaoming|last2=Hiremath|first2=Swapnil|last3=Akbari|first3=Ayub|last4=Shabana|first4=Wael|last5=Fergusson|first5=Dean A.|last6=Knoll|first6=Greg A.|title=Prevention of Contrast-Induced Acute Kidney Injury: Is Simple Oral Hydration Similar To Intravenous? A Systematic Review of the Evidence|journal=PLoS ONE|volume=8|issue=3|year=2013|pages=e60009|issn=1932-6203|doi=10.1371/journal.pone.0060009}}</ref> | '''Hydration''' by drinking or intravenous volume expander, either before or after contract administration, decreases the risk of contrast-induced nephropathy.<ref name="YangHiremath2013">{{cite journal|last1=Yang|first1=Xiaoming|last2=Hiremath|first2=Swapnil|last3=Akbari|first3=Ayub|last4=Shabana|first4=Wael|last5=Fergusson|first5=Dean A.|last6=Knoll|first6=Greg A.|title=Prevention of Contrast-Induced Acute Kidney Injury: Is Simple Oral Hydration Similar To Intravenous? A Systematic Review of the Evidence|journal=PLoS ONE|volume=8|issue=3|year=2013|pages=e60009|issn=1932-6203|doi=10.1371/journal.pone.0060009}}</ref> | ||
| + | |||
| + | ==Example== | ||
| + | As a fictional example, an obese 50 year old male has undergone gastric bypass surgery two days before and has now developed abdominal pain and diarrhea. This is an indication for CT with IV (and oral) contrast.<ref name="LevineCarucci2014">{{cite journal|last1=Levine|first1=Marc S.|last2=Carucci|first2=Laura R.|title=Imaging of Bariatric Surgery: Normal Anatomy and Postoperative Complications|journal=Radiology|volume=270|issue=2|year=2014|pages=327–341|issn=0033-8419|doi=10.1148/radiol.13122520}}</ref> GFR is estimated to be 30 ml/min. | ||
| + | |||
| + | Medical records are checked for additional risk factors, finding diabetes. Based on this, it is deemed appropriate to keep a ratio of maximum 1 g iodine/(ml/min of GFR). With the local iodine concentration of 350 mg/ml, the amount that can be given is: | ||
| + | *2.9 ml * 30 = 87 ml | ||
| + | |||
| + | With the local iodine concentration being 350 mg/ml, the weight-unadjusted volume needed for the abdominal CT is 60 ml. The patient weights 120 kg and is 176 cm tall. The weight adjusted volume is thus: | ||
| + | *60ml x ((0.00723 × 120) + (0.00474 × 176) − 0.341) = 82 ml | ||
| + | |||
| + | The contrast that can be given is thus slightly less than is needed. The patient was probably dehydrated from the diarrhea, and may be rehydrated before the exam. In an emergency, the patient may need surgery without a prior CT. | ||
| + | |||
{{Bottom}} | {{Bottom}} | ||
Revision as of 22:05, 9 November 2018
Author:
Mikael Häggström [notes 1]
In CT with IV contrast, decreased renal function and several other conditions increase the risk of contrast-induced nephropathy, which is a potentially lethal renal injury to the kidney following intravenous radiocontrast.[1]
Contents
When it matters
According to European guidelines, the main risk factors of contrast-induced nephropathy:[2]
- Estimated glomerular filtration rate (eGFR) of less than 30 ml/min/1.73 m2 before intra-venous or intra-arterial radiocontrast administration with second-pass renal exposure (passing lungs or other tissues before the kidneys).
- eGFR of less than 45 ml/min/1.73 m2 before intra-arterial administration with first-pass renal exposure or in ICU patients
- Known or suspected acute renal failure
- Large doses of radiocontrast given IA with first-pass renal exposure
- Multiple radiocontrast injections within 48-72 h
Other risk factors
Look in the medical records (and/or ask the patient) for other risk factors of contrast-induced nephropathy.
The Roxana Mehran score predictor applies the following ten variables:[3]
- Age (4 points if older than 75 years old)
- Anemia (3 points)
- Use of an intra-aortic balloon pump (5 points)
- Decreased real function. In terms of estimated glomerular filtration rate in ml/min:
- eGFR 60 to 40 (2 points)
- eGFR 40 to 20 (4 points)
- eGFR less than 20 (6 points)
- Hypotension (5 points, if systolic BP less than 80 mmHg for at least one hour requiring inotropic support)
- Contrast media volume (1 point per 100 ml)
- Congestive heart failure (5 points)
- Diabetes (3 points).
A risk score of less than 6 carries a risk of 7.5% to score more than 16 carries up to 57% risk.[3]
In addition to those in the Roxana Mehran score, the following are also risk factors of contrast-induced nephropathy:[2]
- Hypoxia
- Cirrhosis
- NSAIDs or (other) nephrotoxic drugs
- Persons in dialysis with residual renal function of at least 400 ml urine / 24h
- Individuals who have undergone kidney transplantation
Metformin use potentially causes lactic acidosis if contrast-induced nephropathy occurs, and according to European guidelines it should be stopped at least 48 hours before a CT with IV contrast if GFR is between 30 and 44 ml/min/1.73 m2. If lower, no contrast should be given unless absolutely necessary.[4]
How much contrast can be given?
In some emergent conditions such as CT of aortic aneurysm with suspected rupture, the need for contrast is greater than the risk of contrast-induced nephropathy.
For the rest of the investigations, evidence suggests that contrast doses should be limited to a ratio of grams of iodine to glomerular filtration rate (Igram / GFRml/min) of a maximum of 1 g/(ml/min).[5] According to European guidelines, the ratio should be less than 1.1 g/(ml/min) for intra-arterial contrast medium administration with first-pass renal exposure (not passing lungs or peripheral tissue before reaching the kidneys).[2] Swedish guidelines are more restrictive, recommending a ratio of less than 0.5 g/(ml/min) in patients with risk factors and irrespective of route of administration, and even more caution in first-pass renal exposure.[2]
| Igram / GFRml/min ratio |
240 mg/ml | 350 mg/ml | 370 mg/ml |
|---|---|---|---|
| 0.5 | 2.1 ml *GFRml/min | 1.4 ml *GFRml/min | 1.4 ml *GFRml/min |
| 1 | 4.2 ml *GFRml/min | 2.9 ml *GFRml/min | 2.7 ml *GFRml/min |
| 1.1 | 4.6 ml *GFRml/min | 3.1 ml *GFRml/min | 3.0 ml *GFRml/min |
How much contrast is needed
| Exam | Iodine concentration | Comments | |||
|---|---|---|---|---|---|
| 300 mg/ml | 350 mg/ml | 370 mg/ml | |||
| CT of brain | 95ml[6] | 80 ml[6] | 75 ml[6] | ||
| CT of thorax | Overall | 70 - 95 ml[notes 2] | 60 - 80 ml[notes 2] | 55 - 75 ml[notes 2] | Parenchymal changes of the lung can often be evaluated adequately without the use of intravenous contrast. |
| CT pulmonary angiogram | 20 ml[notes 3] | 17 ml[notes 3] | 15 ml[notes 3] | Minimal amount when using specific low-contrast protocol.[notes 3] | |
| CT of abdomen | Overall | 70 ml[6] | 60 ml[6] | 55 ml[6] | |
| Liver | 55 ml[notes 4] | 45 ml[notes 4] | 40-45 ml[notes 4] | Minimal required amount.[notes 4] | |
| CT angiography | 25 ml[notes 5] | 20 ml[notes 5] | When using specific low-contrast protocol.[notes 5] | ||
Weight adjustment
The needed dose is proportional to the lean body weight of the patient. For contrast CT in obese individuals, this is optimally calculated by the Boer formula, using height and weight of the patient.[7] Taking this formula, the needed volume of IV contrast from the unadjusted volume given in the table above becomes:
- For men: Weight-adjusted volume = Unadjusted volume x ((0.00723 × W) + (0.00474 × H) − 0.341)
- For women: Weight-adjusted volume = Unadjusted volume x ((0.00583 × W) + (0.011 × H) − 1.12)
, where W is body weight in kilograms and H is body height in centimeters.
Actions
Treating risk factors
Risk factors can sometimes be treated or at least mitigated, especially if having suddenly appeared, such as a decreased renal function when it was previously normal. In such cases a common easily treated cause is dehydration.
Hydration by drinking or intravenous volume expander, either before or after contract administration, decreases the risk of contrast-induced nephropathy.[8]
Example
As a fictional example, an obese 50 year old male has undergone gastric bypass surgery two days before and has now developed abdominal pain and diarrhea. This is an indication for CT with IV (and oral) contrast.[9] GFR is estimated to be 30 ml/min.
Medical records are checked for additional risk factors, finding diabetes. Based on this, it is deemed appropriate to keep a ratio of maximum 1 g iodine/(ml/min of GFR). With the local iodine concentration of 350 mg/ml, the amount that can be given is:
- 2.9 ml * 30 = 87 ml
With the local iodine concentration being 350 mg/ml, the weight-unadjusted volume needed for the abdominal CT is 60 ml. The patient weights 120 kg and is 176 cm tall. The weight adjusted volume is thus:
- 60ml x ((0.00723 × 120) + (0.00474 × 176) − 0.341) = 82 ml
The contrast that can be given is thus slightly less than is needed. The patient was probably dehydrated from the diarrhea, and may be rehydrated before the exam. In an emergency, the patient may need surgery without a prior CT.
Notes
- ↑ For a full list of contributors, see article history. Creators of images are attributed at the image description pages, seen by clicking on the images. See Radlines:Authorship for details.
- ↑ 2.0 2.1 2.2 0.3–0.4 gI/kg in a 70kg individual, according to:
- Iezzi, Roberto; Larici, Anna Rita; Franchi, Paola; Marano, Riccardo; Magarelli, Nicola; Posa, Alessandro; Merlino, Biagio; Manfredi, Riccardo; et al. (2017). "Tailoring protocols for chest CT applications: when and how?
- ↑ 3.0 3.1 3.2 3.3 Using dual energy CTA (such as 90/150SnkVp), according to:
- Leroyer, Christophe; Meier, Andreas; Higashigaito, Kai; Martini, Katharina; Wurnig, Moritz; Seifert, Burkhardt; Keller, Dagmar; Frauenfelder, Thomas; et al. (2016). "Dual Energy CT Pulmonary Angiography with 6g Iodine—A Propensity Score-Matched Study
- ↑ 4.0 4.1 4.2 4.3 The liver generally needs an enhancement of at least 30 HU for proper evaluation according to:
- Multislice CT
- Bae, Kyongtae T. (2010). "Intravenous Contrast Medium Administration and Scan Timing at CT: Considerations and Approaches
- ↑ 5.0 5.1 5.2 CT-angiography in a 70kg person, with 100-150 mg I/kg by using 80 kVp, mAs-compensation for constant CNR, fixed injection duration adapted to scan time, automatic bolus tracking and a saline chaser, according to:
- Nyman, Ulf (2012). Contrast Medium-Induced Nephropathy (CIN) Gram-Iodine/GFR Ratio to Predict CIN and Strategies to Reduce Contrast Medium Doses
References
- ↑ Rudnick, M.; Feldman, H. (2008). "Contrast-Induced Nephropathy: What Are the True Clinical Consequences? ". Clinical Journal of the American Society of Nephrology 3 (1): 263–272. doi:. ISSN 1555-9041.
- ↑ 2.0 2.1 2.2 2.3 Nyman, Ulf; Ahlkvist, Joanna; Aspelin, Peter; Brismar, Torkel; Frid, Anders; Hellström, Mikael; Liss, Per; Sterner, Gunnar; et al. (2018). "Preventing contrast medium-induced acute kidney injury ". European Radiology. doi:. ISSN 0938-7994.
- ↑ 3.0 3.1 Kalgi Modi, Scott C. Dulebohn (2017). Contrast-Induced Nephropathy. StatPearls Publishing. CC-BY-4.0
- ↑ Error on call to Template:cite web: Parameters url and title must be specified. . ESUR. Retrieved on 2018-11-09.
- ↑ Keaney, J. J.; Hannon, C. M.; Murray, P. T. (2013). "Contrast-induced acute kidney injury: how much contrast is safe? ". Nephrology Dialysis Transplantation 28 (6): 1376–1383. doi:. ISSN 0931-0509.
- ↑ 6.0 6.1 6.2 6.3 6.4 6.5 . New Zealand Datasheet. New Zealand Medicines and Medical Devices Safety Authority. Retrieved on 2018-10-16.
- ↑ Caruso, Damiano; De Santis, Domenico; Rivosecchi, Flaminia; Zerunian, Marta; Panvini, Nicola; Montesano, Marta; Biondi, Tommaso; Bellini, Davide; et al. (2018). "Lean Body Weight-Tailored Iodinated Contrast Injection in Obese Patient: Boer versus James Formula ". BioMed Research International 2018: 1–6. doi:. ISSN 2314-6133.
- ↑ Yang, Xiaoming; Hiremath, Swapnil; Akbari, Ayub; Shabana, Wael; Fergusson, Dean A.; Knoll, Greg A. (2013). "Prevention of Contrast-Induced Acute Kidney Injury: Is Simple Oral Hydration Similar To Intravenous? A Systematic Review of the Evidence ". PLoS ONE 8 (3): e60009. doi:. ISSN 1932-6203.
- ↑ Levine, Marc S.; Carucci, Laura R. (2014). "Imaging of Bariatric Surgery: Normal Anatomy and Postoperative Complications ". Radiology 270 (2): 327–341. doi:. ISSN 0033-8419.
