Reducing Complications in the Very High ‘BMI’ Patient

In the last month, we had three ST-elevation myocardial infarction (STEMI) patients who presented acutely ill with particularly difficult clinical problems. Each of these patients required urgent coronary angiography and percutaneous coronary intervention (PCI) for acute MI. Each patient was morbidly obese with a body mass index (BMI) of > 40kg/m2 (5’3”: 300lbs, 6’0”: 405lbs, 5’6”: 345lbs). My team and I were relieved and very thankful we had adopted a “radial first” approach to cardiac cath and now were able to apply the technique to all acute coronary syndrome (ACS) patients. In each patient, we performed the diagnostic study and subsequent PCI from the right radial approach. One patient needed ultrasound guidance to complete radial access. No intervention exceeded our door-to-balloon time. It was also noteworthy that in one patient, the anticipated problems we know to occur with femoral access came true the next day when he continued to do poorly and needed an intra-aortic balloon pump (IABP). IABP insertion was attempted through the right femoral approach with much difficulty (e.g. positioning, prepping and taping up the large panniculus). Worse, the insertion failed, because of the inability to advance the sheath and secure the deep access to the femoral artery. Another patient also served to illustrate another unusual but potentially disastrous problem of positioning, nearly falling off our cath table because of his size and the narrow construction of modern cath lab tables.

Given this recent experience and a publication¹ addressing this topic, I thought it would be worthwhile to review some of the potential complications related to the high BMI patients and ways that may help to reduce these complications. In the The Cardiac Catheterization Handbook, a method of positioning and preparing the obese patient on the cath lab is discussed.²

Vascular complications

Reducing catheterization-related vascular complications begins with recognition of risk factors for complications and preparations to deal with the associated events. All team members — cardiologists, nurses, and techs alike — are responsible for understanding, preparing for and recognizing potential vascular access problems. Major cath lab complications include death, acute myocardial infarction, emergency bypass surgery, and stroke in <3% of patients.³ While less dramatic (although more frequent), minor complications can be as troubling as major complications. Femoral access site bleeding or vessel occlusion, arrhythmias, and transient ischemic attack may occur during or immediately after the procedure. Late complications of renal insufficiency or the rare infection also occur but will not be addressed here. Of all complications, vascular access complications (site bleeding, hematomas, retroperitoneal bleeding, pseudoaneurysm, and arterio-venous (A-V) formation) are the most common cause of morbidity of cath, and if not recognized, can be fatal. These complications result in additional discomfort, extended hospital stay, and higher hospital costs. They often require additional expensive treatment (e.g. blood transfusions, vascular surgery). Patient characteristics and the risk of complications are listed in Table 1.

What is body mass index (BMI) and why is it used?

To define the low, normal and overweight patients, the body mass index (BMI), or Quetelet index, was developed in 1850 by the Belgian polymath Adolphe Quetelet⁴ and was intended to reflect human body fat based on an individual’s weight and height. BMI does not actually measure the percentage of body fat. BMI is defined as the individual’s body mass (weight) divided by the square of his or her height. Depending on the units of measure, BMI is calculated as follows:

BMI = kg/m²
BMI = lbs/in² *703, (correction factor for lbs, inches)
BMI = lbs/ft² *4.88, (correction factor for lbs, feet)

The World Health Organization has classified obesity based on BMI into four categories, as described in Table 2. Patients with a BMI >40kg/m² have also been termed as having extreme obesity (EO). EO patients represent 6% of the total U.S. population and comprise the fastest growing obesity subgroup.⁶ It is well known to all cath lab personnel that performing angiography in patients with EO is associated with higher radiation exposure to both team and operators, and that these patients are at high risk for complications, especially related to access bleeding, which can result in higher in-hospital mortality.⁷

Strategies for reducing complications in the high BMI patient

One strategy among all others to reduce bleeding complications is obvious: changing to radial access. Although intuitively beneficial, there were little data supporting this opinion in the subgroup of high BMI patients until recently. Hibbert et al¹ studied outcomes of EO patients undergoing radial or femoral angiography, and PCI. From their review of 21,103 consecutive coronary procedures from January 2007 to August 2010, the investigators analyzed a cohort of patients with a BMI >40 kg/m². Patients were excluded if there were incomplete data, additional non-coronary procedures (e.g., right heart catheterization, percutaneous valve implantation, patent foramen ovale closure), cardiopulmonary resuscitation, or cardiogenic shock. Both femoral and radial procedures were routinely performed using 6 French (Fr) sheaths.

Of 564 procedures (4% of all patients), 203 (36%) underwent radial angiography and 361 (64%) had a femoral approach. The composite primary outcome of bleeding, access site injury, or non-access site complications occurred in 2% of radial cases and 7.5% of cases in the femoral group (p<0.029), an endpoint primarily due to increased rates of bleeding complications (0% radial vs. 3.3% femoral; p< 0.015) and access site injury (0% radial vs. 4.7% femoral; p< 0.002). Non-access site complications did not differ between the groups.  Of interest, 2 patients in the femoral group had emergency surgery for hemodynamically significant bleeds, and 1 patient died before surgical intervention. In the radial group, 1 patient had an aortic dissection found 7 days after the angiogram and was successfully managed surgically. Overall, compared to a femoral approach, the radial approach significantly reduced the incidence of procedural-related morbidity in EO patients for both diagnostic and PCI procedures. 

However, there was a small price to pay for radial access, with significantly longer procedure times (44 min vs. 31 min, p<0.001) and fluoroscopy times (13 vs. 7 min, p<0.001), with correspondingly more radiation exposure (dose area product, 194 Gycm2 vs. 123 Gycm², p<0.001) and a trend toward more contrast volume use (p<0.06). While diagnostic angiography comprised the bulk of the study procedures, with only a slight imbalance in procedure time and radiation favoring femoral approach, in the PCI subgroup, radial access did not significantly lengthen procedure time, but was accompanied by modest increase in fluoroscopy time (13 min vs. 17 min, p<0.01). Also of particular note is that in the high-risk subgroups, such as patients with STEMI, the radial approach did show reductions in adverse events.

While it is well known that a high BMI makes for more difficult and perhaps more dangerous cardiac cath, it is worth remembering that other medical problems are also common in this group. Additional health risks acquired by the obese patient are listed in Table 3. 

Active steps to reduce potential complications

The high BMI patient is difficult for the staff to transfer to the cath table. The team should use additional helpers to lift and employ transfer slides under the patient. Care should be taken that momentum does not move the patient too far across the table such that the patient might fall. The patient should be positioned on the table with attention to the balance point of patient and arm boards. Restraints are of little value in most cases. In EO patients that cannot be fully moved onto the table, use of a gurney to keep the lower half of the patient off the table can be a last resort, but panning becomes nearly impossible in this setting (Figure 2).²

Because of the increased potential for problems, the lab should consider using an expanded “time out” verification process to address individual patient risk factors, medication doses to be received and equipment to be used. Not much more needs to be said about the decision to use radial as preferred access.^8,9,10 Ultrasound-guided access may be particularly helpful in this patient group.¹¹

The preparation of femoral access drapes after marking the correct location in the groin should be part of the increased attention the operators must employ for safest vascular access. Access techniques should consider micro puncture needles and smaller sheaths (certainly <8Fr), and whenever possible avoid venous sheaths (which add to potential bleeding risk).

To reduce post procedure bleeding chances further, early sheath removal should be performed. In many cases, vascular closure devices are favored. However, the risks versus benefits of the closure device in such patients need to be carefully weighed. Remember that vascular closure device failure can be catastrophic, especially in this subgroup of patients. While manual compression has long been the standard for management of the puncture site, its effectiveness in this type of patient is always a source of uncertainty and concern.

The level of anticoagulant intensity and duration should be minimized if possible, but kept appropriate for the clinical presentation. Consider use of low-dose heparin or the substitution of bivalirudin for unfractionated heparin. Common sense suggests that minimizing the procedure time will reduce potential for patient movement with the sheath in place that can kink and bleed, unbeknownst to the operator or team. In addition, all nurses should be familiar with the correct dosing for the increased weight and, of course, renal function, of these patients. Lastly, consider admitting the patient to special skilled nursing units experienced in the care of the post PCI patient, with emphasis on the unexpected vascular complications.

I hope this discussion will be of help to your lab in your efforts to successfully and safely manage our growing population of high BMI patients needing cardiac catheterization.

References

1. Hibbert B, Simard T, Wilson KR, et al. Transradial versus transfemoral artery approach for coronary angiography and percutaneous coronary intervention in the extremely obese. J Am Coll Cardiol Intv 2012; 5: 819-826.
2. Kern M, Skelding K. Chapter 2: Arterial and venous access. In: Kern MJ ed. The Cardiac Catheterization Handbook. 5th Edition. Philadelphia, PA: Elsevier; 2011: 77.
3. Dumont CJ, Keeling AW, Bourguignon C, et al Predictors of vascular complications post diagnostic cardiac catheterization and percutaneous coronary interventions. Dimens Crit Care Nurs 2006 May-Jun; 25(3): 137-142.
4. Eknoyan G. Adolphe Quetelet (1796–1874)—the average man and indices of obesity. Nephrology Dialysis Transplantation 2007; 23(1): 47-51.
5. McTigue K, Larson JC, Valoski A, et al. Mortality and cardiac and vascular outcomes in extremely obese women. JAMA 2006; 296: 79-86.
6. Sturm R. Increases in clinically severe obesity in the United States, 1986–2000. Arch Intern Med 2003; 163: 2146-2148.
7. Das SR, Alexander KP, Chen AY, et al. Impact of body weight and extreme obesity on the presentation, treatment, and in-hospital outcomes of 50,149 patients with ST-segment elevation myocardial infarction: results from the NCDR (National Cardiovascular Data Registry). J Am Coll Cardiol 2011; 58: 2642-2650.
8. Jolly SS, Yusuf S, Cairns J, et al., for the RIVAL Trial Group. Radial versus femoral access for coronary angiography and intervention in patients with acute coronary syndromes (RIVAL): a randomised, parallel group, multicentre trial. Lancet 2011; 377: 1409-1420.
9. Rao SV, Ou FS, Wang TY, et al. Trends in the prevalence and outcomes of radial and femoral approaches to percutaneous coronary intervention: a report from the national cardiovascular data registry. J Am Coll Cardiol Intv 2008; 1: 379-386.
10. Bertrand OF, Rao SV, Pancholy S, et al. Transradial approach for coronary angiography and interventions: results of the first international transradial practice survey. J Am Coll Cardiol Intv 2010; 3: 1022-1031.
11. Seto A. Ultrasound guidance for radial access: getting in the first time. Cath Lab Digest May 2012;20(5):1-10.

Disclosure: Dr. Kern reports that he is a speaker for Volcano Therapeutics and St. Jude Medical, and is a consultant for Merit Medical.