A novel biometric approach to estimating tidal volume.

BACKGROUND: Low tidal volume ventilation (LTVV) of 4-8 mL/kg of ideal body weight (IBW) reduces mortality in patients with acute respiratory distress syndrome, and, more recently, it has been recommended as the default therapy for all controlled ventilation. However, adherence to LTVV is poor. Barriers to adherence include not having height measurements taken or IBW calculated during admission. The aim of our project was to develop and validate a simple one step biometric measuring tool to directly estimate tidal volume (VT) in ventilated patients based on their demispan. OBJECTIVES: To validate our novel biometric approach for the estimation of VT in mechanically ventilated patients by demonstrating its accuracy as a simple reliable alternative to IBW derived from measured height. DESIGN AND SETTING: A simple computer program was written based on regression equations for demispan, height and IBW which used simple substitution to produce a vector graphic scale with markings in millilitres of 6 mL/kg IBW VT printed onto a paper tape. We performed an observational validation study on ventilated patients after cardiac surgery comparing the VT derived from demispan measurements using our tape with the VT based on IBW calculated from pre-operative vertical height. MAIN OUTCOME MEASURE: We compared compliance with a target VT ≤ 6.5 mL/kg for VT derived using our demispan method and with VT based on IBW calculated from vertical height. RESULTS: Eighty-two patients were studied. The mean age was 65.7 years (SD, 11.4) and 61 patients (74%) were male. Mean height was 170.4 cm (SD, 9.5) and mean body mass index for the group was 28.6 kg/m2 (SD, 5.5). The VT based on 6 mL/kg IBW estimated by traditional height method and using our biometric tape method correlated well (r = 0.8) and was not statistically different, with a mean difference of -7.5 mL (SEM, 8.8). Bland-Altman plot showed 95% limits of agreement from -64 mL to 79 mL around the mean difference of 7.5 mL, with 4 points (4.9%) outside the limits of agreement. Fifty-one of the initial VT (62%) were compliant, with a target of ≤ 6.5 mL/kg IBW using volumes determined from measured height, while 66 of the tape volumes (80%) would have been compliant at a target of ≤ 6.5 mL/kg IBW. CONCLUSION: Estimating VT using of our biometric one step approach based on demispan correlates well with VT derived from vertical height. The simplicity of its use and accuracy could lead to improved adherence in a large cohort of patients who currently do not receive the recommended VT restriction.

Perioperative Hemoglobin Trajectory in Adult Cardiac Surgical Patients.

Preoperative anemia and nadir hemoglobin (Hb) during cardiopulmonary bypass (CPB) have been identified as significant risk factors for blood transfusion during cardiac surgery. The aim of this study was to confirm the association between preoperative anemia, perioperative fluid management, and blood transfusion. In addition, the proportion of elective cardiac surgery patients presenting for surgery with anemia was identified to examine whether the opportunity exists for timely diagnosis and intervention. Data from referral until hospital discharge were comprehensively reviewed over a 12-month period for all nonemergency cardiac surgical patients operated on in our institution. Of the 342 patients identified, elective cases were referred a median of 35 days before preoperative clinic and operated on a median of 14 days subsequently. Subacute cases had a median of 3 days from referral to surgery. As per the World Health Organization (WHO) criteria for anemia, 24.2% of elective and 29.6% of subacute patients were anemic. Blood transfusion was administered to 46.2% of patients during their admission. Transfusion was more likely in patients who were female (odds ratio [OR]: 2.45, 95%confidence interval [CI]: 1.28-4.70), had a low body mass index (BMI) (OR: .89, 95% CI: .84-.94), preoperative anemia (OR: 5.15, 95% CI: 2.59-10.24), or renal impairment (OR: 5.44, 95% CI: 2.42-12.22). Hemodilution minimization strategies reduced the Hb fall during CPB, but not transfusion rates. This study identifies a high prevalence of preoperative anemia with sufficient time for elective referrals to undergo appropriate diagnosis and interventions. It also confirms that low red cell mass (anemia and low BMI) and renal impairment are predictors of perioperative blood transfusion. Perfusion strategies to reduce hemodilution are effective at minimizing the intraoperative fall in Hb concentration but did not influence transfusion rate.

Learning and teaching motor skills in regional anesthesia: a different perspective.

Existing literature on learning in regional anesthesia broadly covers the rate of skill acquisition and the structure of educational programs. A complementary body of literature spanning psychology to medical education can be found describing skill acquisition in other fields. Concepts described in this literature have direct application to the teaching of regional anesthesia. This review introduces a selection of these complementary educational concepts, applying them to ultrasound-guided regional anesthesia skills education. Key educational concepts presented in this article can be divided into 3 sections, namely, how residents acquire manual skills, how tutors teach, and type of feedback.