Pelvic fat volume reduction with preoperative very low energy diet (VLED): implications for rectal cancer surgery in the obese.

BACKGROUND: Obese patients have higher complication rates after pelvic surgery. Laparoscopic rectal surgery may not be possible in the obese individual due to mesorectal, total pelvic and general visceral fat volumes. Very low energy diets reduce visceral fat but the changes within the pelvis and mesorectum are unknown. The aim of the present study was to quantify the proportion of fat lost from total pelvic and mesorectal fat with a very low energy diet (VLED) and define simple, accessible measurements that correlate with expected volume reduction. METHODS: A study was conducted on proportion change in mesorectal and intrapelvic fat volumes in patients on a VLED prior to bariatric surgery at the Alfred Hospital in Melbourne. The VLED was a standardized 4-week meal replacement. Proportion change in mesorectal and intrapelvic fat volumes were measured. Patients had standardized pre-diet and post-diet magnetic resonance imaging (MRI) of the pelvis. Body mass index, weight and girth measures were obtained. Adipose quantification analysis was performed using Q-Fat. RESULTS: Nine patients were included in this study, who were preparing for bariatric (not colorectal) surgery (5 females, median age 42 years, range 27-59 years) pre-protocol body mass index was 55.8 (range 39.5-60.6 kg/m2); median weight was 163 kg. Median mesorectal fat reduction was 29.9% (range 11.6-66.6%). Linear regression showed a relationship between the amount of mesorectal fat reduction and two variables: patient height and the distance from S1 to the posterior aspect of the rectum on MRI. The relationship predicted response to the diet (R2 67%, p = 0.040). CONCLUSIONS: Very low energy diets result in a clinically significant reduction in mesorectal fat with a lesser change in total pelvic fat, suggesting that very low energy diets may be useful for preparation for pelvic surgery in the obese. The distance from S1 to the posterior rectum correlates well with mesorectal reduction, making this a valuable clinical tool when volumetric analysis is not possible. This analysis is limited to the quantification of the effect of the diet and cannot comment on the safety of this approach before pelvic cancer surgery.

Correction to: Pelvic fat volume reduction with preoperative very low energy diet (VLED): implications for rectal cancer surgery in the obese.

Due to substantial contributions by Dr. Phillip Malouf and Dr. Stephen Bell.

Classification of low systemic vascular resistance using photoplethysmogram and routine cardiovascular measurements.

Low systemic vascular resistance (SVR) can be a useful indicator for early diagnosis of critical pathophysiological conditions such as sepsis, and the ability to identify low SVR from simple and noninvasive physiological signals is of immense clinical value. In this study, an SVR classification system is presented to recognize the occurrence of low SVR, among a heterogenous group of patients (N = 48), based on the use of routine cardiovascular measurements and features extracted from the finger photoplethysmogram (PPG) as inputs to a quadratic discriminant classifier. An exhaustive feature search was performed to identify a near optimum feature subset. Cohen's kappa coefficient (κ) was used as a performance measure to compare candidate feature sets. The classifier using the following combination of features performed best (κ = 0.56, sensitivity = 96.30%, positive predictivity = 92.31%): normalized low-frequency power (LFNU) derived from PPG, ratio of low-frequency power to high-frequency power (LF/HF) of the PPG variability signal, and the ratio of mean arterial pressure to heart rate (MAP/HR). Classifiers that used either LF(NU) (κ = 0.43), LF/HF (κ = 0.37) or MAP/HR (κ = 0.43) alone showed inferior performance. Discrimination of patients with and without low SVR can be achieved with reasonable accuracy using multiple features derived from the PPG combined with routine cardiovascular measurements.

A new insulin derivative for the preparation of insulin--enzyme conjugates: an application in the enzyme immunoassay of insulin.

A new insulin derivative, mercaptobutyrimidyl pyridine disulfide insulin, was prepared under conditions which directed the reaction preferentially through the terminal alpha-amino group of the A-chain. The purified monosubstituted insulin exhibited only a marginal decrease in antigenicity as measured by radioimmunoassay; there was, however, a significant reduction in biological activity in the mouse convulsion assay. Conjugation of the insulin derivative to human placental alkaline phosphatase was carried out via a thiol interchange reaction and the resulting conjugate was active in a double-antibody, solid-phase enzyme immunoassay for insulin.