Body Surface Area Calculation Research Articles

Formulas to calculate body surface area (BSA) in children—Suitability for daily use

Purpose of study: The calculation of body surface area (BSA) in children has significant importance both in emergency medicine and intensive care medicine. Important applications of BSA include the calculation of drug doses in anaesthesia, paediatric nephrology, oncology, and immunology. During the last years, a multiplicity of formulas with different complexity and impact in daily practice was published. The purpose of this study was to summarize the most important formulas for use in the daily routine.

Variability in results from predicted resting energy needs as compared to measured resting energy expenditure in Korean children

Energy needs are influenced by many factors, including ethnicity. Multiple studies have shown that the accuracy of an energy prediction equation varies with the ethnic background of the study population. Therefore, it is crucial to identify the most accurate energy prediction equation to use for a given population. This study compared measured resting energy expenditure to results from commonly-used energy prediction equations to identify the most accurate equation to use for Korean children. Based on previous literature showing wide variation in accuracy of energy prediction equations in different ethnic groups, we hypothesized that results from measured- vs. predicted energy needs would be significantly different in this population. Subjects were 92 South Korean children (38 boys, 54 girls) age 7.7 +/- 2.7 years (mean +/- SD). Measurements included: resting metabolic rate (TrueOne 2400 metabolic cart), weight/height (digital scale/stadiometer); body fat (BIA, Inbody720), blood pressure (sphingomanometer), triceps skinfold thickness (MD-500 skinfold calipers), muscle mass (Heymsfield's formula) and body surface area (Dubois formula) calculations. Resting energy needs were predicted using the Harris-Benedict, WHO/NAO/FAO, Altman and Dittmer, Maffeis, and Schofield-HW equations, and the Dietary Reference Intake recommendations. Measured and predicted energy needs were significantly correlated (P < .001 for all; range R(2) = 0.54-0.56), yet significantly different for all equations studied (P < .05) except the Maffeis and Schofield-HW equations. Differences (means +/- SD) between measured vs. predicted energy needs ranged from 9.5 +/- 123.2 (Schofield-HW) to 199.6 +/- 132.7 (WHO/NAO/FAO) kcal/day, where a value closer to zero indicates increased accuracy of the prediction equation to correspond to measured energy needs. Although results from equations studied were significantly correlated with measured resting energy needs, notable discrepancies existed which, over time, could produce undesirable weight changes in Korean children.

A cross-sectional study comparing variation in body surface area and chemotherapy dosing in pediatric oncology using two different methods

Standardizing body surface area (BSA) determination is essential for avoiding variation in chemotherapy dosage calculations. In this study, we compared variation in BSA calculation using weight and height by the Mosteller formula with weight alone using recently adapted table at a local oncology center. Cross-sectional study of pediatric oncology patients presenting to a pediatric oncology clinic over a week period of time. One-hundred consecutive pediatric oncology patients presented to the clinic. The mean BSA calculated by the Mosteller formula was 0.83 m(2) (SD 0.24) and the mean BSA determined by the table (based on weight alone) was 0.82 m(2) (SD 0.25). The mean variation in dosing between the two methods was 1.64% (SD 3.4). Only 13 out of 100 patients (13%) had equal dosing using both methods and 21 out of 100 patients (21%) had dosing variation greater than 5%. When comparing both methods, using paired t-test, the difference was statistically significant (t((99)) = 3.99 and p < 0.001). Significant differences in BSAbased chemotherapy dosing exist in our center. The Mosteller method should remain the standard until prospective studies are performed to determine the significance of this dosing variability on toxicity and survival outcome.

Prednisone dosing per body weight or body surface area in children with nephrotic syndrome—is it equivalent?

The current guidelines recommend a dosage of prednisone of 60 mg/m(2) body surface area per day (BSA PRED) for the initial therapy of nephrotic syndrome (NS). Alternatively, a dosage of 2 mg/kg body weight per day (W PRED) can be used. We hypothesized that the BSA PRED and W PRED are not equivalent and analyzed the differences between BSA PRED calculated with various formulas for body surface area (BSA), W PRED and the dose of prednisone prescribed for our patients. We performed a retrospective chart review of the patients at their initial presentation of NS. Thirty-three children were included, of median age 3.34 years at presentation. The W PRED was significantly lower than BSA PRED (P < 0.05), with a median W PRED:BSA PRED ratio of 0.85 [interquartile range (IQR) 0.8 to 0.9]. The difference between W PRED and BSA PRED decreased proportionally to patients' weights up to 30 kg. No differences were noted between the various BSA formulas using both weight and height for the calculation of BSA. The Bland-Altman analysis showed a proportional error between W PRED and BSA PRED up to the average daily dose of 60 mg, with a mean bias of 0.86 (95% limits of agreement = 0.68 to 1.05). Ten out of the 33 patients (30%) were given a lower than recommended BSA PRED dose by more than 5 mg/day. In conclusion, the dosage of prednisone at 2 mg/kg per day versus 60 mg/m(2) per day is not equivalent for patients with weights <30 kg and/or dose <60 mg/day.

P-287 Treatment of Full-Term Infants with Patent Ductus Arteriosus Based on Preterm Infants

Background: Functional status of heart is important in patients with circulatory instability. However, currently, measurements of cardiac function often need invasive methods such as Swan-Ganz catheterization or heavy machine such as a full-scale ultrasonoscope. Materials and Methods: During a 2 mouths period, we evaluated the aortic flow using a dedicated Doppler ultrasonometer which is non-invasive and can be performed conveniently and portably on the bedside. A total of 100 persons were recruited for recording of aortic blood flow. The machine automatically analyzes aortic flow waveforms to generate peak velocity (VPK) peak, velocity time interval (VTI), heart rate (HR), stroke volume (SV), cardiac output (CO) and cardiac index (CI). Results: The age of examined subjects ranged from 1 month to 62 years old, the height (Ht) ranged between 57 and 181 cm. The weight (Wt) between 4.2 and 106 kg, the calculated body surface area (BSA) ranged between 0.27 and 2.3 cm2. The regression analysis for various indices were listed as follows: Index Y = K (constant) +b (slope) × Index X: VPK = 1.5049 + 0.0028×Wt; VPK = 1.592 + 0.0015×Ht; VPK = 1.5477 + 0.1284×BSA; SV = 35.905 + 0.7856×Wt; SV = 31.384 + 0.7169×Ht; SV = 16.308 + 41.161×BSA; CO = 0.0396 + 3.399×Wt; CO = 0.0367 + 0.071×Ht; CO = 2.3948 + 2.0859×BSA. Conclusion: Our experience showed cardiac function can be obtained conveniently and non-invasively using a dedicated portable meter. We also demonstrate that peak aortic blood flow velocity is almost a constant through human ages, while cardiac output increased with progressive increase in individual size.

P-286 Non-Invasive Evaluation of Aortic Blood Flow in Normal Taiwanese

Background: Functional status of heart is important in patients with circulatory instability. However, currently, measurements of cardiac function often need invasive methods such as Swan-Ganz catheterization or heavy machine such as a full-scale ultrasonoscope. Materials and Methods: During a 2 mouths period, we evaluated the aortic flow using a dedicated Doppler ultrasonometer which is non-invasive and can be performed conveniently and portably on the bedside. A total of 100 persons were recruited for recording of aortic blood flow. The machine automatically analyzes aortic flow waveforms to generate peak velocity (VPK) peak, velocity time interval (VTI), heart rate (HR), stroke volume (SV), cardiac output (CO) and cardiac index (CI). Results: The age of examined subjects ranged from 1 month to 62 years old, the height (Ht) ranged between 57 and 181 cm. The weight (Wt) between 4.2 and 106 kg, the calculated body surface area (BSA) ranged between 0.27 and 2.3 cm2. The regression analysis for various indices were listed as follows: Index Y = K (constant) +b (slope) × Index X: VPK = 1.5049 + 0.0028×Wt; VPK = 1.592 + 0.0015×Ht; VPK = 1.5477 + 0.1284×BSA; SV = 35.905 + 0.7856×Wt; SV = 31.384 + 0.7169×Ht; SV = 16.308 + 41.161×BSA; CO = 0.0396 + 3.399×Wt; CO = 0.0367 + 0.071×Ht; CO = 2.3948 + 2.0859×BSA. Conclusion: Our experience showed cardiac function can be obtained conveniently and non-invasively using a dedicated portable meter. We also demonstrate that peak aortic blood flow velocity is almost a constant through human ages, while cardiac output increased with progressive increase in individual size.

A Cross-Sectional Study Comparing Variation in Body Surface Area and Chemotherapy Dosing in Pediatric Oncology Using Two Different Methods

Abstract: Standardizing Body Surface Area (BSA) determination is essential for avoiding variation in chemotherapy dosage calculations. In this study we compared variation in BSA calculation using weight and height by the Mosteller formula with weight alone using recently adapted table at the Princess Norah Oncology Center (PNOC).Methods: Cross-sectional study of pediatric oncology patients presenting to the pediatric oncology clinic at PNOC over a week period of time.Results: One hundred consecutive pediatric oncology patients presented to the clinic. The mean BSA calculated by the Mosteller formula was 0.83m2 (Standard Deviation = 0.24) and the mean BSA determined by the table (based on weight alone) was 0.82m2 (Standard Deviation = 0.25). The mean variation in dosing between the two methods was 1.64% (Standard Deviation = 3.4). Only 13 out of 100 patients (13%) had equal dosing using both methods and 21 out of 100 patients (21%) had dosing variation greater than 5%. When comparing both methods, using paired t-test, the difference was statistically significant (t(99) = 3.99 and P < 0.001).Conclusion: Significant differences in BSA-based chemotherapy dosing exist in our center. The Mosteller method should remain the standard until prospective studies are performed to determine the significance of this dosing variability on toxicity and survival outcome.

Variation in melphalan dosing in myeloma patients undergoing high-dose chemotherapy and autotransplantation

7047 Background: Chemotherapy doses are often reduced in obese patients to ameliorate toxicity; a practice shown to result in adverse outcome in breast cancer. The dose of melphalan used before autografting in myeloma correlates with outcome. Because melphalan is widely distributed in the body, exposure of myeloma cells to the drug is likely dependent upon the actual body weight (ABW). We evaluated variability in melphalan dose received by patients in terms of mg/kg ABW and ideal body weight (IBW). Methods: Data on 243 autotransplants for myeloma after 200 mg/m2 melphalan were analyzed retrospectively. The weight value used to calculate body surface area (BSA) using the Dubois formula was the ABW if it was lower than or up to 20% higher than IBW (non-obese). If ABW was >20% above IBW (obese), the value used for BSA calculation was IBW + 25–50% of the difference between ABW and IBW. Results: 191 patients were obese (ABW 20.2% to 104.7% higher than IBW; median 42.8% higher) and 92 were non-obese (ABW 18.3% lower than to 19.5% higher than IBW; median 9.0% higher). The melphalan dose administered was 2.9–6.2 mg/kg ABW (median 4.5) and 4.6–7.5 mg/kg IBW (median 5.6). There was no correlation between the mg/kg IBW and mg/kg ABW doses (r=0.10; P=0.12). The median dose for the obese group was significantly lower than the non-obese group when calculated by ABW (4.0 vs 5.0 mg/kg; range 2.9–5.5 vs 4.4–6.2; P<0.0001). The median dose was higher for the obese group when calculated by IBW (5.8 vs 5.5 mg/kg; range 5.0–7.5 vs 4.6–6.3; P<0.0001). There was a strong inverse correlation (r=0.90; P<0.0001) between the per cent ABW-IBW difference and the melphalan dose in mg/kg ABW - consistent with decreasing drug exposure as the degree of obesity increased. Expectedly, there was a modest direct correlation (r=0.49; P<0.0001) between the per cent ABW-IBW difference and the melphalan dose in mg/kg IBW. Conclusions: The dose of melphalan measured in mg/kg ABW is significantly lower in obese patients than in non-obese patients due to dose-adjustment. Further work is required to see if this affects outcome. No significant financial relationships to disclose.

Baseline Fitness Measures In A Cohort Of Obese Children

BACKGROUND: There is an increasing population of overweight and obese children. While many studies have investigated interventional strategies to reduce weight, few studies have reported the actual fitness status of obese children. PURPOSE: To establish baseline fitness measures in a mixed-race cohort of obese children. METHODS: We studied 33 patients (18 male) between the ages of 10-17 years. Patients were referred to the Children's Heart Centre from the Centre for Healthy Weights Program at B.C. Children's Hospital. All patients were above the 95th percentile for body mass index (BMI), adjusted for age. Initial assessment included a physical examination by a pediatric cardiologist, an electrocardiogram (ECG), an echocardiogram (ECHO), and a cardiopulmonary exercise test (CPX). The CPX was completed on a treadmill according to our institutional protocol. Treadmill speed started at 2.0 mph and increased by 0.5 mph every minute until volitional fatigue. Measurements included: height, weight, calculated body surface area (BSA) and BMI, minute ventilation (VE), peak oxygen consumption (VO2peak), respiratory exchange ratio (RER) and heart rate (HR). Our criteria for a maximal test were a HR ≥180 bpm and a RER ≥1.10. RESULTS: Mean height and weight were 164.9 ± 10.5 cm and 94.4 ± 16.8 kg, respectively. ECG and ECHO findings were normal in all but 1 patient who had an enlarged left ventricle. Only 14/33 (42%) patients satisfied the criteria for a maximal test. Peak VE was 83.0 ± 26.6 L/min. Mean absolute VO2peak was 2.70 ± 0.60 L/ min. Mean relative VO2peak was 29.0 ± 6.5 ml/kg/min (64% predicted). There was no significant difference between relative VO2peak for boys and girls. There was a significant correlation between HR and absolute VO2peak (r=0.46; p<0.01). CONCLUSION: We have shown that in this cohort of mixed-race obese children, less than half were able to satisfy our criteria for completing a maximal effort exercise test. In those patients it is difficult to determine whether or not there is a significant reduction in their aerobic capacity, interpret other aspects of their test results, and provide objective information for exercise prescription. Exercise testing is safe and should be considered before providing exercise prescription to these children.

Predictive validity of an age-specific MET equation among youth of varying body size

The purpose of this study was to cross-validate the age-specific Freedson MET equation among children and adolescents of varying body size. Sixty-seven children (41 boys; 26 girls) between 6 and 13 years completed five 3-min trials (1.6, 3.2, 4.0, 4.8, and 6.4 km h(-1)) on a motorized treadmill. During each trial, participants wore an Actigraph accelerometer while oxygen consumption was assessed by indirect calorimetry. Using the Actigraph activity counts, predicted MET values were determined with the age-specific Freedson equation and were compared with measured MET values using dependent t tests. Participants were divided into body size categories based on their calculated body surface area (BSA, m2) (small: BSA<or=0.96 m2; medium: 0.96 m2<BSA<or=1.20 m2; large: BSA>1.20 m2) to determine if body size influenced the difference between measured and predicted MET values. The measured MET value was similar to the predicted MET value at the slowest treadmill speed (1.6 km h(-1)) (2.3 vs. 2.3 METs); however, the measured MET value was lower than the predicted MET value at the remaining speeds (3.2, 4.0, 4.8, and 6.4 km h(-1)) (P<0.001). With the exception of the fastest treadmill speed (6.4 km h(-1)), the mean difference between the measured and predicted MET values was greater between the two smaller BSA categories compared to the largest BSA category. The results suggest that the age-specific Freedson child equation significantly overestimates energy expenditure (METs) during locomotor speeds between 3.2 and 6.4 km h(-1). This effect was primary observed among relatively smaller children.

Temporal trends in protocol-specified adjuvant chemotherapy dosing in obese patients with breast cancer

11055 Purpose: Dosing of breast cancer adjuvant chemotherapy in obese women varies substantially, with up to 40% of obese women receiving reduced (compared to full weight-based) doses. Such variation indicates uncertainty about best practices. This study reports changes over time in protocol-specified dose determinations in heavy patients. Methods: The National Cancer Institute database of cooperative group trials was used to identify completed clinical trials of non-myeloablative breast cancer adjuvant chemotherapy. Dose determinations specified in each protocol were categorized into one of four groups: 1) full weight-based dosing, 2) dose reduction in heavy patients (ideal or corrected body weight used to calculate body surface area, BSA), 3) dosing in heavy patients left to physician’s discretion, or 4) no specific instructions. Results: Of 110 eligible clinical trial protocols identified, 61 (55%) were retrieved. Of the 16 protocols initiated before 1985, 15 (94%) either did not address dose determination (n = 6) or specified dose reduction (n = 9) in heavy patients. Of the 45 protocols initiated after 1985, 26 (58%) specified full weight-based dosing, 13 (29%) specified dose reductions, 4 (9%) left dosing in heavy women to the physician’s discretion, and 3 (7%) had no specific instructions for dose determinations in heavy patients. The difference in the use of full weight based doses before and after 1985 was statistically significant (p value = 0.0003, 2-sided Fisher’s exact test). One of the cooperative groups, which contributed 10 of the 45 (22%) clinical trial protocols since 1985, specifies a maximum BSA of 2.0 m2 for cyclophosphamide and doxorubicin in all protocols. Conclusions: Over the last two decades, dose determinations in clinical trial protocols have, with the exception of one cooperative group, specified use of actual body weight. Present-day dose reductions in obese patients who are not participating in clinical trials suggest a lack of diffusion of information about optimal dosing in obesity. The continued practice of limiting the doses of cyclophosphamide and doxorubicin in patients with a BSA over 2.0 m2 in the protocols of one cooperative group may contribute to persistent uncertainty about optimal dosing in heavy patients. No significant financial relationships to disclose.

Oral chemotherapy safety practices at US cancer centres: questionnaire survey

Objective To characterise current safety practices for the use of oral chemotherapy.Design Written questionnaire survey of pharmacy directors of cancer centres.Setting Comprehensive cancer centres in the United States.Results Respondents from...

Effect of body surface area calculations on body fat estimates in non-obese and obese subjects

The purpose of the present study was to compare body surface area (BSA) estimates using two equations (Dubois and Dubois versus Livingston) and their respective effects on per cent body fat (%BF) obtained with two molecular approaches of body composition analysis, two-compartment (2C) and five-compartment (5C) models. Body composition data using the 2C model were studied in healthy adults, 432 women (body mass index (BMI): 28.3 ± 4.4 kg m−2) and 147 men (BMI: 26.8 ± 3.9 kg m−2), while another sample of 126 women (BMI: 30.4 ± 3.7 kg m−2) was evaluated using the 5C model. Measures of body volume (BV) assessed by air displacement plethysmography, bone mineral content by dual energy x-ray absorptiometry (DXA) and total-body water by deuterium dilution were used to estimate %BF with the 5C model. Comparison of means and linear regression analysis was performed. Using BSADubois, either in 2C and 5C models, BV and %BF estimates were significantly underestimated compared to results obtained using BSALivingston (p < 0.05). BMI was strongly associated with %BF differences using BSADubois and BSALivingston in both 2C (men: r = 0.90; women: r = 0.88) and 5C models (r = 0.88). Though %BFDubois and %BFLivingston were strongly associated (r2 = 1.000), some variability was observed on %BF differences using BSADubois and BSALivingston. These findings suggest that BSA calculation is critical in BF estimation, supporting the use of a more accurate equation for non-obese and obese subjects.

Quality Performance Improvement With the Implementation of Standard Chemotherapy Order Forms

Before October 2000, physicians in our institution handwrote chemotherapy orders on blank order sheets. There was no standard to which the physician could include variables that were crucial to the completeness of a chemotherapy order. For this reason, chemotherapy orders were frequently incomplete and had to be adjusted by the pharmacist after discussing the missing variables with the ordering physician. As a part of our goal to minimize errors, standard chemotherapy forms were initiated at our institution in October 2000. The first standard form implemented was a written order form that constituted a standard of the ideal variables necessary to accurately complete chemotherapy orders. These variables were the diagnosis, regimen, height, weight, body surface area (BSA), route, frequency, duration and chemotherapy dose and calculation based upon BSA. The next updated form was an electronic version similar to the original, and was implemented in April 2002. From February 1999 to March 2000, using the traditional unstandardized blank order sheets, the average order completeness was 45%. After the standard written forms were introduced, from October 2000 to March 2002, the average chemotherapy order completeness was 81%, an improvement of 36%. Completeness improved to an average of 93% from April 2002 to December 2003, after the implementation of the electronic chemotherapy form. Chemotherapy order completeness improves considerably through the standardization of chemotherapy order forms. The electronic forms show an additional improvement over handwritten forms. Electronic standardization of chemotherapy forms should be adopted as a best-practice model in hematology-oncology practices throughout the country.

Quality Performance Improvement With the Implementation of Standard Chemotherapy Order Forms

Purpose Before October 2000, physicians in our institution handwrote chemotherapy orders on blank order sheets. There was no standard to which the physician could include variables that were crucial to the completeness of a chemotherapy order. For this reason, chemotherapy orders were frequently incomplete and had to be adjusted by the pharmacist after discussing the missing variables with the ordering physician. As a part of our goal to minimize errors, standard chemotherapy forms were initiated at our institution in October 2000. Methods The first standard form implemented was a written order form that constituted a standard of the ideal variables necessary to accurately complete chemotherapy orders. These variables were the diagnosis, regimen, height, weight, body surface area (BSA), route, frequency, duration and chemotherapy dose and calculation based upon BSA. The next updated form was an electronic version similar to the original, and was implemented in April 2002. Results From February 1999 to March 2000, using the traditional unstandardized blank order sheets, the average order completeness was 45%. After the standard written forms were introduced, from October 2000 to March 2002, the average chemotherapy order completeness was 81%, an improvement of 36%. Completeness improved to an average of 93% from April 2002 to December 2003, after the implementation of the electronic chemotherapy form. Conclusion Chemotherapy order completeness improves considerably through the standardization of chemotherapy order forms. The electronic forms show an additional improvement over handwritten forms. Electronic standardization of chemotherapy forms should be adopted as a best-practice model in hematology-oncology practices throughout the country.

Gender‐related differences of renal mass supply and metabolic demand after living donor kidney transplantation

Kidney donation from female donors to male recipients has been reported to be associated with decreased allograft survival. Whether there was a gender-related inadequacy between donor nephron supply and recipient functional demand was investigated in this study. One hundred ninety-five living donor kidney transplant recipients that had neither ischemic injury, episode of rejection, nor any complication were included. Weights and heights of both donors and recipients were recorded to calculate body surface area, lean body weight, and body mass index. The donated kidney was weighed just after cold flush, and the recipient's serum creatinine (Scr) was measured on a daily basis post-operatively. When the recipient's Scr reached the baseline, a 24-h urine was collected for the amount of proteinuria (Upr), creatinine excretion (Ucr) and creatinine clearance (Ccr) calculation. The effect of donor and recipient gender was analysed by independent sample t-test. On average, male donors and recipients were heavier and taller than females. However, the mass of kidneys donated from men and women were not statistically different. The gender-related differences in post-transplant Scr and Ucr of recipients were associated with the differences in the parameters of metabolic demands of recipients rather than with the weight of implanted kidney (renal mass supply) or with pre-operative renal functions of donors (functional supply). The early graft function is not determined by donor gender. The effect of recipient gender on the graft function depends on the metabolic demands, which are higher in male recipients.

A Simplified Weight-Based Method for Pediatric Drug Dosing for Zidovudine and Didanosine in Resource-Limited Settings

Zidovudine and didanosine are antiretroviral drugs used for human immunodeficiency virus (HIV)-infected children with dose recommendations based on body surface area calculations. Although weight and height can both be measured, it may be impractical to expect providers in resource-limited settings to estimate accurately body surface area. We developed an antiretroviral dosing chart based on authoritative sources for brand name drugs in weight bands (ie, 5-6.9, 7-9.9, 10-11.9, 12-14.9, 15-16.9, 17-19.9, 20-24.9, 25-29.9, 30-34.9 and 35-40 kg) to assist proper dosing of antiretrovirals for HIV-infected children in resource-limited settings. For drugs dosed by body surface area, we estimated likely weights and heights for age using standardized US growth charts for girls from which doses in weight bands were calculated. For this analysis, we calculated the difference between weight-based doses and body surface area-based doses for zidovudine 10 mg/mL oral solution, zidovudine 100-mg capsules, and didanosine 25, 50 and 100-mg chewable tablets using actual heights and weights from HIV-infected children in Africa and Romania. We used 1752 observations from 826 HIV-infected children (48% girls) from 9 countries. A total of 454 observations were in children <20 kg and 1298 > or =20 kg. For those <20 kg, the median difference of the weight-based dose as compared with the body surface area-based dose for zidovudine solution was -6.4% (range, -22.6, +13.7), zidovudine capsules +3.1% (range, -38.8, +44.7), didanosine chewable tablets +0.7% (range, -24.4, +22.5); for those > or =20 kg for zidovudine solution was 0.0% (range, -16.4, +11.8), zidovudine capsules +7.6% (range, -16.4, +36.9) and didanosine chewable tablets +1.2% (range, -16.4, +14.1). The dose precision for children <20 versus > or =20 kg was different for zidovudine solution (P < 0.001) and zidovudine capsules (P < 0.001), but not didanosine chewable tablets. The frequency that weight-based dose was more than 20% less than the body surface area-based dose for those <20 kg was 1.3% for zidovudine solution, 27.2% for zidovudine capsules and 4.9% for didanosine chewable tablets. For those > or =20 kg, the weight-based dose was never more than 20% less than the body surface area-based dose. Dosing zidovudine and didanosine by weight band provides reasonably precise dosing as compared with body surface area-based doses. However, use of zidovudine capsules in children <20 kg results in under dosing by >20% in many instances. Didanosine chewable tablets allow for higher dosing precision compared with zidovudine capsules because of increased flexibility in the dosage form. Solid dosage forms of antiretroviral medications designed specifically for children are urgently needed.

Cardiopulmonary bypass and mitral valve replacement during pregnancy

Gravid patient cardiopulmonary bypass remains a high-risk procedure with regard to fetal preservation. Maternal mortality is similar to that of the nonpregnant female at 1.5-5%. However, fetal mortality remains high at 16-33%, with an average of 19% over the past 25 years, with no correlation to gestational age. Teratogenesis is a major consideration in the first trimester. Variations in the timing of surgical intervention, gestational age, maternal health status, type of procedure, pre- or postorganogenesis, perfusion protocol, and pharmaceutical therapy are all factors that can influence fetomaternal outcome. In this report, we present a literature review along with our experience of a 26-year-old female who developed complications with her pregnancy at approximately 17 weeks gestation, with adverse neurological sequelae. The patient was 152 cm in height and weighed 48 kg, with a calculated body surface area of 1.40 M2. She had no prior history of cardiac disease and, upon admission to our institution, presented with a declining health status in pulmonary edema and was treated medically, with an ultimate requirement for mitral valve replacement. The total cardiopulmonary bypass time was 99 min with an aortic crossclamp time of 83 min. The literature, as expected, is limited to case reports and reviews since a controlled clinical trial during pregnancy is nonexistent, using extracorporeal circulation. This greatly challenges the medical staff in managing such difficult cases, with an incidence of heart disease during pregnancy of 1.2-3.7%.

Height prediction from ulna length.

Height is fundamental to assessing growth and nutrition, calculating body surface area, and predicting pulmonary function in childhood. Its measurement is hindered by muscle weakness, joint, or spinal deformity. Arm span has been used as a substitute, but is inaccurate. The objective of the study was to identify a limb measurement that precisely and reproducibly predicts height in childhood. Males (n=1144) and females (n=1199), aged 5 years 4 months to 19 years 7 months, without disability were recruited from Melbourne schools. Height, arm span, ulna, forearm, tibia, and lower leg lengths were measured with a Harpenden stadiometer and anthropometer. Prediction equations for height based on ulna length (U) and age in years (A) were developed using linear regression. Ulna centile charts were developed by the LMS method. For males, height (cm)=4.605U+1.308A+28.003 (R2=0.96); for females, height (cm)=4.459U+1.315A+31.485 (R2=0.94). Intra- and inter-observer variability was 0.41% and 0.61% relative to the mean, respectively. Height prediction equations from tibia, forearm, and lower leg length were calculated. We show that ulna measurement is reproducible and precisely predicts height in school-age children. It appears to be superior to arm span measurement when neuromuscular weakness, joint, or spinal deformity exists. Ulna growth charts should facilitate growth assessment.

A Standard Weight Descriptor for Dose Adjustment in the Obese Patient

To develop a standard weight descriptor that can be used for estimation of patient size for obese patients. Data were available from 3849 patients: 2839 from oncology patients (index data set) and 1010 from general medical patients (validation data set). The patients had a wide range of age (16-100 years), weight (25-165 kg) and body mass index (BMI) [12-52 kg/m2] in both data sets. From the normal-weight patients in the oncology data set, an equation for male and female patients was developed to predict their normal weight as the sum of the lean body mass and normal fat body mass. The equations were evaluated by predicting the weight of patients in the general medical data set who had a normal BMI (<25 kg/m2). In addition, the clinical utility of the predicted normal weight (PNWT) descriptor was assessed by (i) comparing body surface area and allometric scaling calculations based on actual weight of obese patients versus PNWT; and (ii) comparing the predictive performance of creatinine clearance using the Cockcroft and Gault equation when using actual weight of obese patients versus PNWT to predict gentamicin clearance. The PNWT equations developed from the oncology data set predicted accurately the actual weight of normal weighted (BMI <25 kg/m2) general medical patients (R2 = 0.968 men, R2 = 0.946 women). Using actual weight when computing body surface area and when allometric scaling for obese patients results in significant overestimation of patient size, especially for female patients and those with BMIs >35 kg/m2. The use of PNWT in the Cockcroft and Gault equation provided better predictions of gentamicin clearance than when using actual weight. A standard weight descriptor has been developed that can be used in dosing algorithms for patients who are obese (BMI >30 kg/m2).