Terri of the FattiesUnited blog brought this study to the attention of the fatosphere briefly several months ago, just as I was about to write a post about this study too, so I put the post on the back burner.
However, in writing an upcoming post on treating Surgical Site Infections in people of size, I came across the study again and decided it was important enough to be highlighted once more. Any of us can end in the Emergency Room at any time, regardless of size. But those of us who are fat need to be aware of the possibility of underdosing and to be able to advocate for ourselves as needed. Perhaps sharing the full details of this study will help in that process.
In this study, the initial antibiotic dosages of "morbidly obese" folks (BMI over 40) who visited the E.R. and were prescribed 3 common antibiotics were analyzed retrospectively for a 3-month period. The doses were compared with internal hospital guidelines for antibiotic dose adjustments for obese folks.
Less than 5% of morbidly obese patients were given the correct antibiotic dose for their weight.
That's right, more than 95% of high BMI patients were underdosed with antibiotics, putting them at significant risk for serious complications.
The study notes:
Although there are guidelines for dose adjustments for many of the antibiotics commonly used in the emergency department (ED), they are seldom used...Underdosing antimicrobials presents risk of treatment failure and may promote antimicrobial resistance. Education is necessary to improve early antibiotic administration to obese patients.Study Details
This study was done as a quality improvement review at an urban Level I trauma center with an emergency medicine residency.
In the study, pharmacy records were collected retrospectively to identify the initial dose of cefazolin, cefepime, or ciproflaxin given in the E.R. to patients with a BMI greater than 40 and who weighed more than 100 kg.
These three drugs were chosen because they are used so frequently and because, unlike many antibiotics, there are readily-available guidelines for dosing obese folks without having to do a bunch of complicated extra calculations first. The guidelines are distributed in a handbook each year to every resident and are also always available on the hospital's internal website, so there was no excuse for not knowing or not checking the recommended dosages.
The study looked at only the initial dose given (and to be fair, any additional dose within 4 hours, as sometimes doctors self-correct dosing when they have a chance to look up the guidelines).
This attention to the initial dose is important because the first dose of antibiotics is the most important in knocking down an infection. According to the study, the effectiveness of this class of antibiotics (cephalosporins) is proportional to the amount of time kept above the Minimum Inhibitory Concentration (MIC). If the initial dose does not achieve MIC, then the patient may develop resistance to the antibiotics, not to mention serious complications, longer hospital stays, or even death.
In the study, there were 1,910 orders that fit the criteria in the 3-month study period. Of these, only 4.6% of the antibiotic orders were dosed appropriately for morbidly obese patients.
For cefepime, the adherence rate was 8%. For cefazolin, the adherence rate was 3%, and for ciproflaxin the adherence rate was only 1.2%.
This is an appallingly poor adherence rate to readily-available, simple dosing guidelines. The study notes this and emphasizes how important it is to ensure adequate dosing in morbidly obese patients:
Attaining therapeutic dosing in [morbidly obese] patients is especially important. Obese patients present a greater risk of infection and a higher morbidity and mortality associated with infection than does the general population. Subtherapeutic dosing increases the risk of treatment failure, unnecessary escalation to broader-spectrum antibiotics, and selection of resistant pathogens...Because early antibiotic administration reduces mortality in life-threatening infections, meeting proper dosing guidelines in the [Emergency Department] should be of the highest priority.The authors go on to cite another study which found that when the perioperative dose of cefazolin was doubled to 2g in obese patients, the postoperative infection rate dropped from 16.5% to 5.6%. This shows that increased dosages of this antibiotic in heavier patients do result in improved outcomes.
Interestingly, there is recent data (Pevzner 2011) on cesareans in morbidly obese patients suggesting that even a doubled, 2g dose of cefazolin may not be enough, and that further research is needed to figure out the most effective perioperative dose in this group. What implications this has for E.R. usage is unknown but suggests doses bigger than 2g may also need to be considered. Research needs to be done to find the optimal dose for each size.
Sooner or later, people of every size end up in the E.R., especially as they age. Different populations present different care challenges; obese people present a unique subset whose care challenges are often under-recognized and under-addressed.
Bottom line, the best care protocols for obese people are yet to be determined because research on the topic has been woefully inadequate. Furthermore, even when the best care protocols are known, they are often not followed by medical personnel. Therefore, it is critical as people of size that we know about key care issues in our own care and how to advocate for ourselves when we interact with medical personnel.
One of the most understudied areas in the care of obese patients is optimal medication dosage. Research shows that obese patients (and especially morbidly obese patients) are often dosed inappropriately with a variety of drugs, from chemotherapy to anti-coagulants to antibiotics, and this may be correlated to poorer outcomes among these groups.
Clearly, it is imperative that more research and physician education be done on appropriate medication dosage for people of size as quickly as possible.
In this study, only initial antibiotic dosing at the Emergency Room was examined, using only common antibiotics with easily-available dose adjustments. Even so, less than 5% of the morbidly obese patients were given dosages that adhered to the internal guidelines of the hospital.
One has to wonder how adequate the dosing was in very fat patients for the rest of their hospital stays and how that impacted their outcomes.
Ironically, this was in a hospital that is a regional referral center for fat patients and is recognized as a Bariatric Surgery "Center of Excellence" (ugh). That makes the findings even more alarming.
If a teaching hospital that specializes in the treatment of very fat people doesn't routinely use the correct antibiotic dosing in their E.R., what are the underdosing rates in community hospitals that don't specialize in fat patients at all?
This study has lessons both for people of size and for the medical community.
Fat people should know that if they end up in the E.R. for an infection of some sort, they need to ask their physician to check into adjusted antibiotic doses for weight. Not every type of antibiotic needs dose adjustment, mind ─ it all depends on how they are designed to work in the body. But this study indicates that you may really have to push your physician to find out about dose adjustments and to use them when they are indicated.
Most physicians truly want their patients to get better, so it's really OK to ask about whether weight-based dosing is needed for you. However, don't be afraid to ask for a consult with an infections specialist if you feel your E.R. doctor is not attentive to your concerns, or to involve the hospital's Patient Advocate in getting your concerns heard. There are measures in place to help patients advocate for their own needs, and you don't have to go it alone.
But the first step is self-education, to know where the potential issues may lie, to know to ask questions about dosages, and to feel empowered enough to do so.
For medical professionals, the associated lesson is that they must aggressively press for better research on optimal medication dosage in obese patients, and to continue to push for more physician education and accountability on these matters.
*Next post.....other ways to improve response to infections in people of size, including IV antibiotics, more frequent dosings, and topical infusions.
Am J Emerg Med. 2011 Dec 12. Underdosing of common antibiotics for obese patients in the ED. Roe JL, Fuentes JM, Mullins ME. PMID: 22169576
BACKGROUND: Obesity is a growing problem in the United States. Obesity alters the pharmacokinetic profiles of various drugs. Although there are guidelines for dose adjustments for many of the antibiotics commonly used in the emergency department (ED), they are seldom used. METHODS: This is an institutional review board-approved retrospective study at an American Society of Metabolic and Bariatric Surgery Center of Excellence and a level I trauma center with annual ED volumes of more than 80 000 visits. Data were retrospectively collected from ED pharmacy records during a 3-month period in 2008. Any first dose of cefepime, cefazolin, or ciprofloxacin administered in our ED to a patient recorded as both more than 100 kg and with a body mass index greater than 40 kg/m(2) was compared with our hospital guidelines and found to either adhere or not adhere to those guidelines. RESULTS: There were 1910 orders found to meet the study criteria: 775 orders for cefepime, 625 orders for cefazolin, and 510 orders for ciprofloxacin. Adherence rates for first dose of cefepime, cefazolin, and ciprofloxacin administered, respectively, were 8.0%, 3.0%, and 1.2%. CONCLUSION: Emergency physicians frequently underdose cefepime, cefazolin, and ciprofloxacin in obese patients. Underdosing antimicrobials presents risk of treatment failure and may promote antimicrobial resistance. Education is necessary to improve early antibiotic administration to obese patients.Surgery. 2004 Oct;136(4):738-47. Perioperative antibiotic prophylaxis in the gastric bypass patient: do we achieve therapeutic levels? Edmiston CE, et al. PMID: 15467657
BACKGROUND: Perioperative surgical antibiotic prophylaxis requires that therapeutically effective drug concentrations be present in the tissues. METHODS: Patients undergoing Roux-en-Y gastric bypass for morbid obesity were given 2 g cefazolin preoperatively, followed by a second dose at 3 hours. Thirty-eight patients were each assigned to 1 of 3 body mass index (BMI) groups: (A) BMI=40-49 (N = 17); (B) BMI=50-59 (N=11); (C) BMI > or= 60 (N=10). Multiple timed serum (baseline; incision, 15, 30, 60 minutes; prior to second prophylactic dose; and closure) and tissue (skin, subcutaneous fat, and omentum) specimens were collected and cefazolin concentration analyzed by microbiological assay. RESULTS: ...Over 90% of serum samples exhibited therapeutic concentrations covering 53.8% of gram-positive and 78.6% of gram-negative surgical pathogens. However, therapeutic tissue levels were achieved in only 48.1%, 28.6%, and 10.2% of groups A, B, and C, respectively. CONCLUSIONS: Pharmacokinetic analysis suggests that present dosing strategies may fail to provide adequate perioperative prophylaxis in gastric bypass patients.Obstet Gynecol. 2011 Apr;117(4):877-82. Effects of maternal obesity on tissue concentrations of prophylactic cefazolin during cesarean delivery. Pevzner L, et al. PMID: 21422859
OBJECTIVE: To estimate the adequacy of antimicrobial activity of preoperative antibiotics at the time of cesarean delivery as a function of maternal obesity. METHODS: Twenty-nine patients scheduled for cesarean delivery were stratified according to body mass index (BMI) category, with 10 study participants classified as lean (BMI less than 30), 10 as obese (BMI 30-39.9), and nine as extremely obese (BMI 40 or higher). All patients were given a dose of 2 g cefazolin 30-60 minutes before skin incision. Antibiotic concentrations from adipose samples, collected after skin incision and before skin closure, along with myometrial and serum samples, were analyzed with microbiological agar diffusion assay. RESULTS: Cefazolin concentrations within adipose tissue obtained at skin incision were inversely proportional to maternal BMI (r=-0.67, P<.001)...Although all specimens demonstrated therapeutic cefazolin levels for gram-positive cocci (greater than 1 microgram/g), a considerable portion of obese and extremely obese did not achieve minimal inhibitory concentrations of greater than 4 micrograms/g for Gram-negative rods in adipose samples at skin incision (20% and 33.3%, respectively) or closure (20.0% and 44.4%, respectively)... CONCLUSION: Pharmacokinetic analysis suggests that present antibiotic prophylaxis dosing may fail to provide adequate antimicrobial coverage in obese patients during cesarean delivery.