Carbon dioxide: an alternative to iodinated contrast media

Adrenal vein sampling with gadolinium contrast medium in a patient with florid primary aldosteronism and iodine allergy

We describe a 35-year-old woman who was allergic to iodine contrast medium and was diagnosed with primary aldosteronism (PA) based on functional confirmatory tests. She was suspected to have unilateral PA because of marked hypertension, spontaneous hypokalemia, high plasma aldosterone, reduced plasma renin activity, and a right hypodense adrenal tumor. She wanted to become pregnant and requested adrenalectomy instead of medical treatment with mineralocorticoid receptor antagonists. Localization of PA by adrenal vein sampling (AVS) was necessary, but angiography with iodine contrast medium was not possible because of her allergy. AVS was performed using gadolinium contrast agent (gadoterate meglumine) instead of iodine, in combination with computed tomography angiography (CTA). In AVS, before and after adrenocorticotropin (ACTH) loading, 12 blood samples were drawn from the right adrenal vein, left adrenal central vein, left adrenal common duct, left and right renal veins, and the lower inferior vena cava with only 5 mL of gadolinium medium. There were no complications during AVS. Examination revealed an elevated aldosterone/cortisol ratio on the right side, lateralized ratio of 7.4, and contralateral ratio of 0.76; the patient was diagnosed with right unilateral PA. She underwent right adrenalectomy and showed improvements in aldosterone level from 312.4 pg/mL to 83.0 pg/mL, potassium from 3.0 mEq/L to 3.9 mEq/L, and systolic blood pressure from 138 mm Hg to 117 mm Hg. In PA patients with iodine allergy, AVS can be performed safely and precisely using gadolinium contrast combined with CTA.

Endovascular aneurysm repair: current and future status

Endovascular aneurysm repair has rapidly expanded since its introduction in the early 1990s. Early experiences were associated with high rates of complications including conversion to open repair. Perioperative morbidity and mortality results have improved but these concerns have been replaced by questions about long-term durability. Gradually, too, these problems have been addressed. Challenges of today include the ability to roll out the endovascular technique to patients with adverse aneurysm morphology. Fenestrated and branch stent-graft technology is in its infancy. Only now are we beginning to fully understand the advantages, limitations, and complications of such technology. This paper outlines some of the concepts and discusses the controversies and challenges facing clinicians involved in endovascular aneurysm surgery today and in the future.

Nine-year experience with insertion of vena cava filters in the intensive care unit

BACKGROUND

Vena cava filter insertion (VCF) is traditionally performed in a radiology suite or in the operating room. We reviewed our experience of bedside VCF insertion in the intensive care unit (ICU) performed by general surgeons.

METHODS

A prospective, observational study of bedside VCF insertion in the ICU was performed by general surgeons between February 1996 and June 2005. Demographic data and procedural complications were recorded.

RESULTS

Four hundred three patients underwent bedside VCF insertion. Complications included 1 groin hematoma, 2 misplacements, and a right ventricular perforation from a dilator requiring surgical repair. DVT occurred in 38 patients (8.5%); 14 occurred at the insertion site. There were 2 pulmonary embolisms (<1%) after VCF. Contrast-related renal failure occurred in 2 of the first 35 patients; carbon dioxide gas is now used for contrast in high-risk patients.

CONCLUSIONS

Bedside insertion of VCF in the ICU by surgeons is safe and effective.

Adverse cerebrovascular effects of intraarterial CO2 injections: development of an in vitro/in vivo model for assessment of gas-based toxicity

PURPOSE

To assess whether and how CO(2) can cause ischemic injury in the central nervous system after internal carotid artery injection.

MATERIALS AND METHODS

In 14 adult pigs, both internal carotid arteries were catheterized via a transfemoral approach. One carotid artery served as control and the other was injected via a prototype gas injector with defined volumes and pressures of gas. Effects were assessed by clinical observation, repeated magnetic resonance (MR) imaging, histopathology, and vital staining. An in vitro flow circuit was used to model injection parameters.

RESULTS

Single injections of CO(2) did not produce persistent clinical symptomatology. In vitro conditions were created in which bubbles adhered to the tubing of the circuit, creating functional stenoses, or coalesced into larger bubbles that became trapped, thereby reducing flow and augmenting potential embologenic effects of subsequent injections. With in vitro-derived dual injection parameters, seven pigs underwent two sequential injections of CO(2). All did well after the first injections, but all had adverse effects after the second injections, including involuntary tonic-clonic muscular movements, cardiopulmonary arrest, recurrent intractable seizure activity during recovery, hemorrhagic venous infarcts on gross and histopathologic examination, and blood-brain barrier breakdown on vital staining. MR imaging was not sensitive even after symptomatic intraarterial air injection.

CONCLUSIONS

Absence of adverse effects after single bolus injections in pigs does not prove the safety of intracranial CO(2) injections in human patients. Considering the possible deleterious effects of repeat intravascular injections in the highly sensitive system of the brain, it may be prudent for clinical application at other approved sites to let time pass between boluses sufficient to permit absorption of wall-adherent and coalescent bubbles that could cause gas embolic events.

Estudo angiográfico de fístula arteriovenosa utilizando gás carbônico como meio de contrante

OBJETIVO: Este estudo tem por finalidade obter um método diagnóstico angiográfico alternativo que possa ser utilizado em doentes com alto risco ao uso de meio de contraste iodado. MATERIAIS E MÉTODOS: Foram estudados 26 doentes com insuficiência renal crônica, que tiveram suas fístulas analisadas, submetidos à angiografia digital - na primeira fase, utilizando o meio de contraste iodado e, na segunda fase, gás carbônico como meio de contraste, com registro em filme angiográfico. A angiografia foi avaliada por dois médicos independentes, que analisaram a opacificação, o diagnóstico radiológico e o calibre dos vasos; a análise comparativa das medidas da artéria, da veia e da freqüência respiratória antes e após a injeção de contraste foi realizada pelo autor. RESULTADOS: Os resultados obtidos pela analise estatística utilizando coeficiente kappa apresentaram concordância entre os dois médicos, referente à opacificação, de 0,3217, referente ao diagnóstico radiológico, de 0,5583, e referente à analise de calibre dos vasos, de 0,4298. A análise das medidas da artéria e da veia não apresentou diferença significativa pela medida de posição e dispersão, mostrando concordância na regressão linear, com p-valor de 0,3657 e de 0,2041; para a freqüência respiratória, as análises das medidas de posição e dispersão não apresentaram diferença significativa. CONCLUSÃO: Concluímos ser este método uma alternativa no estudo angiográfico em pacientes com antecedente alérgico ou com risco nefrotóxico.

Comparison of carbon dioxide and iodinated contrast for cavography prior to inferior vena cava filter placement

BACKGROUND

The use of iodinated contrast in the critically ill trauma patient has been associated with the development of acute renal failure. The low incidence of nephrotoxicity associated with carbon dioxide (CO(2)) makes it an ideal contrast agent for cavography. However, the use of CO(2) has been limited, because reportedly it underestimates the diameter of the inferior vena cava (IVC).

METHODS

During a 6-month period (January 2000 through June 2000), 25 adult trauma patients required IVC filter placement. Bedside cavagrams using CO(2) followed by iodinated contrast were employed to determine the diameter of the IVC and the anatomy of the renal veins.

RESULTS

Using CO(2) injection for cavography, we were able to determine the diameter of the IVC and the anatomy of the renal veins in all patients. Furthermore, when CO(2) cavography was compared with the results obtained with iodinated contrast, the difference in diameter of the IVC was within 1 mm.

CONCLUSIONS

Based on these data, it was determined that CO(2) cavagrams accurately reflect the diameter of the IVC and the anatomy of the renal veins. Additionally, CO(2) cavagrams can be safely performed in the intensive care unit during bedside placement of IVC filters.

The endovascular management of ruptured abdominal aortic aneurysms

Endovascular aneurysm repair (EVAR) is a controversial technique, which remains the subject of a number of prospective randomised trials. Although questions remain regarding its long-term durability objective evidence exists which demonstrates its reduced physiological impact compared with conventional open repair. If this technique could be used in patients with ruptured abdominal aortic aneurysm (AAA) it may reduce the high peri-operative mortality. A review of the literature identified a limited experience with EVAR of ruptured AAA. Only a small number of case series with selected patients exist. The majority of patients were haemodynamically stable. However, the selective use of aortic occlusion balloons allowed successful endovascular management in a small number of unstable cases. All investigators had access to an "off the shelf" endovascular stent-graft (EVG). Per-operative mortality ranged from 9 to 45% and may reflect increasing experience and patient selection. A number of patients who underwent successful EVAR were turned down for open repair. A number of important lessons have been learned from these studies but questions remain regarding patient suitability and staffing issues. If these difficulties can be surmounted then the technique may offer an alternative to open repair.

[Gas embolism during radical nephrectomy by retroperitoneal laparoscopy]

A case of CO2 gas embolism occurring during retroperitoneal laparoscopic right radical nephrectomy in a 70-year-old-woman is reported. Patient's outcome was excellent after venous clamping, fluid loading and application of a positive and expiratory pressure. Gas embolism is a well documented complication of laparoscopic surgery, but has been rarely described in retroperitoneal laparoscopy for urologic procedure. The retroperitoneal surgical site, the major surgical procedure with vessel manipulation and the left lateral position seem to be the risk factors for gas embolism in this case.

Digital subtraction angiography of the abdominal aorta and lower extremities: carbon dioxide versus iodinated contrast material

PURPOSE

To compare the diagnostic value of carbon dioxide to that of iodinated contrast material for digital subtraction angiography of the abdominal aorta and lower extremities.

MATERIALS AND METHODS

Thirty-five patients underwent comparative CO2 and iodinated contrast material arteriography of the abdominal aorta and lower extremities. For each contrast study, three independent observers evaluated the degree of opacification and percentage of stenosis of each vessel, the degree of certainty of their observations, and the overall quality of the study. Data of CO2 and iodinated studies were compared using analysis of variance for repeated measures. Interobserver and intertechnique agreements were estimated with Cohen's kappa and intraclass correlation coefficient.

RESULTS

Iodine-based vascular opacification was superior to that with CO2 in the central and distal arteries (P = .02). The degree of certainty and overall quality score were higher for iodine than for CO2-based contrast studies (P = .00001). The interobserver agreement for categorizing stenoses was higher for iodine as compared to CO2-based angiography. No significant difference was observed between the mean stenosis values obtained with CO2 and iodine-based angiography in any segment. Intraclass correlation coefficient demonstrated a high degree of convergence of the two techniques for assessing the percentage of stenosis.

CONCLUSION

CO2 can be used as an alternative to iodinated contrast material for obtaining arteriograms of the abdominal aorta and lower extremities for investigating atherosclerotic disease.

Carbon dioxide as a contrast agent to guide vascular interventional procedures

OBJECTIVE

The purpose of this study was to assess the value and limitations of carbon dioxide (CO2) as a contrast agent to guide vascular interventional procedures.

SUBJECTS AND METHODS

Twenty-two adults underwent 26 vascular interventional procedures (21 arterial, five venous). We aimed to use only CO2 if possible because these patients had renal insufficiency (n = 21; mean creatinine level, 2.8 mg/dl) or were allergic to contrast material (n = 1). Arterial procedures performed included renal angioplasty or stent (n = 6), iliac angioplasty or stent (n = 5), infrainguinal angioplasty (n = 5), arterial bypass graft angioplasty (n = 3), and thrombolysis (n = 2). Venous procedures included transjugular intrahepatic portosystemic shunt recanalization (n = 3), angioplasty of the venous anastomosis of a thigh dialysis graft (n = 1), and angioplasty of the inferior vena cava (n = 1).

RESULTS

Twenty-five of the 26 procedures were successfully performed. Of the 26 procedures, eight required no iodinated contrast material and 11 required less than or equal to 20 ml of contrast material. CO2 proved to be inadequate for the remaining seven procedures. Iliac artery angioplasty or stent placement required an average of 9 ml of iodinated contrast material; infrainguinal angioplasty required an average of 22 ml of iodinated contrast material.

CONCLUSION

CO2 can be successfully used as a contrast agent in a variety of vascular interventional procedures. Such procedures can usually be performed in the iliac and infrainguinal arteries using minimal supplemental iodinated contrast material. However, CO2 failed to provide satisfactory guidance in half of the intraabdominal procedures in our study.