Terry K. Rosborough

Heparin Thromboprophylaxis in Gastric Bypass Surgery

Background: Patients undergoing gastric bypass surgery are at risk for postoperative venous thromboembolism. Thromboprophylaxis often includes fixed doses of some type of heparin. However, it is unlikely that the same dose of subcutaneous heparin will be optimal for all patients, because heparin pharmacokinetics depend on a number of patient variables, including thickness of the adipose layer. Methods: An adjusted-dose, unfractionated heparin protocol was developed using pharmacokinetic data from 245 medical and surgical patients. Heparin doses were adjusted to achieve subtherapeutic peak anti-factor Xa heparin activity levels of 0.11-0.25 units/mL. This protocol was then applied to a prospective series of 700 patients undergoing laparoscopic Roux-en-Y gastric bypass who had no history of thromboembolism. Heparin prophylaxis was begun the evening of the day of surgery. Results: No patients were diagnosed with a deep venous thrombosis, but 3 (0.4%) were diagnosed with a non-fatal pulmonary embolism. Heparin therapy was halted because of bleeding in 2.3% of patients but only half of these required blood transfusions (1% of total). No patient required reoperation. Minor wound hematomas occurred in 0.6%. There were no deaths from any cause in this series. Conclusion: Use of a monitored, adjusted-dose unfractionated heparin prophylactic protocol in a laparoscopic gastric bypass patient population resulted in doses greater than those used in traditional fixed-dose protocols. However, bleeding and thromboembolism rates were very low and no patients died.

Unfractionated Heparin Infusion for Thromboprophylaxis in Highest Risk Gastric Bypass Surgery

Background: Patients undergoing gastric bypass for obesity are at risk for postoperative venous thromboembolic complications. Per our routine, these patients receive unfractionated heparin (UFH) per a previously described, blood volume-based, subcutaneous prophylactic UFH protocol. However, some patients have additional risk factors for thromboembolism, and we consider these patients to be at highest risk. To increase the predictability and reliable achievement of prophylactic anti-factor Xa levels for these patients at highest risk, we developed a prophylactic UFH continuous intravenous infusion protocol. Methods: An UFH prophylactic protocol was developed in which the initial UFH loading dose and infusion rate were determined, based on patient blood volume and age.The target prophylactic anti-factor Xa activity range was 0.15-0.20 units/mL. 19 patients were admitted to the hospital the day before gastric bypass surgery. A prophylactic UFH infusion was initiated, and anti-factor Xa levels were checked and adjusted per protocol. The patients underwent surgery the following day and the UFH infusion was continued intra-operatively. Results: No patients were diagnosed with a deep venous thromboembolism. 2 patients experienced peri-operative hemorrhagic complications in spite of anti-factor Xa activity levels in, or only slightly above, the targeted range. Both patients recovered without further complications. Conclusion: For highest risk gastric bypass patients, an UFH prophylactic continuous infusion protocol was effective in preventing postoperative thromboembolic events. Hemorrhagic complications were easily managed and did not result in long-term sequelae.

Unreliability of International Normalized Ratio for Monitoring Warfarin Therapy in Patients with Lupus Anticoagulant

Study Objective. To compare the international normalized ratios (INRs) of patients positive for lupus anticoagulant and the INRs of control patients receiving warfarin therapy with equivalent therapeutic chromogenic factor X levels.

Achieving Target Antifactor Xa Activity with a Heparin Protocol Based on Sex, Age, Height, and Weight

Study Objectives. To develop and validate an improved unfractionated heparin (UFH) dosage protocol, using antifactor Xa levels as the outcome variable.

Selecting an Equation to Estimate Glomerular Filtration Rate for Use in Renal Dosage Adjustment of Drugs in Electronic Patient Record Systems

Study Objective. To identify a variant of the Cockcroft‐Gault equation whose estimate would agree with the Modification of Diet in Renal Disease (MDRD) estimate of glomerular filtration rate (GFR) since the MDRD equation may not be programmable in some electronic patient record systems.

Internal medicine point-of-care ultrasound assessment of left ventricular function correlates with formal echocardiography

Although focused cardiac ultrasonographic (FoCUS) examination has been evaluated in emergency departments and intensive care units with good correlation to formal echocardiography, accuracy for the assessment of left ventricular systolic function (LVSF) when performed by internal medicine physicians still needs independent evaluation.

Heparin resistance as detected with an antifactor Xa assay is not more common in venous thromboembolism than in other thromboembolic conditions.

Study Objective. To identify whether heparin resistance when measured with an antifactor Xa assay is more frequent in patients with venous thromboembolic disease than in patients with other thromboembolic conditions.

Case report: an unrecognized etiology of transient gallbladder pain in heart failure diagnosed with internist-performed point-of-care ultrasound

The excellent sensitivity and specificity of right upper quadrant (RUQ) ultrasound for gallbladder pathology in patients with abdominal pain is heavily relied upon in routine diagnostic evaluation. The hour-to-hour timing of this test in a patient with fluctuating symptoms is not widely recognized as having a significant impact on its sensitivity. However, we present a case report describing the essential role of symptom-timed point-of-care ultrasound in making an elusive diagnosis of transient cholecystalgia in a patient with RUQ pain and congestive heart failure (CHF). This case also demonstrates an important etiology of RUQ pain in patients with CHF beyond that of congestive hepatopathy. A review of the related entities of acalculous cholecystitis, congestive hepatopathy, and diffuse gallbladder wall thickening is provided.

Relationship between chromogenic factor X and international normalized ratio differs during early warfarin initiation compared with chronic warfarin administration.

Chromogenic factor X (CFX) monitoring is necessary in patients with potential international normalized ratio (INR) artifacts during warfarin therapy. The relationship of CFX with the INR needs to be quantitated to have warfarin protocols that are equivalent with either test as a monitoring parameter. This study investigated whether the CFX/INR relationship is different during warfarin initiation compared with that during chronic warfarin therapy. Outpatients (N = 164) taking chronic doses of warfarin and inpatients (N = 137) initiating warfarin therapy had plasma samples tested for CFX and INR. The best fit mathematical relationship of CFX and INR was determined for both groups. A six hundred and twenty-five bed, adult-only, private, tertiary care teaching hospital was the setting of the study. The best fit equation for chronic warfarin patients was quadratic using a reciprocal transformation of the INR. The best fit equation for the warfarin initiation patients was linear using logarithmic transformation of CFX and INR. The predicted CFX from INRs over the range of 1.4–2.2 was 7–18% higher in the warfarin initiation patients than in the chronic warfarin patients. Translation of CFX values into equivalent INRs for use in warfarin initiation and maintenance protocols is improved when using equations specific to the patient situation.

Skull and Sinus

Traditional outpatient diagnosis of acute rhinosinusitis frequently results in overuse of antibiotics. Point-of-care ultrasound (POCUS) of the maxillary sinus is specific for clinically important fluid, but may miss subtle abnormalities that are rarely clinically important. The ethmoid and frontal sinuses are more challenging to image and are infrequently abnormal in isolation from the maxillary sinus. The absence of maxillary sinus fluid is a strong reason to avoid antibiotics in most patients, and helps reassure them. However, a patient with fever, severe symptoms suggestive of sinusitis, but no fluid with maxillary ultrasound, may need a computerized tomography (CT) scan to look for isolated ethmoid, frontal, or sphenoid sinusitis. A few clinical studies, and our clinic’s experience, suggest that ultrasound can substantially reduce antibiotic use for sinusitis [1–3], although there are no large randomized trials to confirm this. Only 23% of patients suspected of sinusitis in our clinic had positive ultrasound [3]. The presence of fluid does not differentiate between viral and bacterial disease, so the final antibiotic decision requires integration of ultrasound with the rest of the patient findings.