David Bracco

Reference values of fat-free and fat masses by bioelectrical impedance analysis in 3393 healthy subjects

Determination of fat-free mass (FFM) and fat mass (FM) is of considerable interest in the evaluation of nutritional status. In recent years, bioelectrical impedance analysis (BIA) has emerged as a simple, reproducible method used for the evaluation of FFM and FM, but the lack of reference values reduces its utility to evaluate nutritional status. The aim of this study was to determine reference values for FFM, FM, and %FM by BIA in a white population of healthy subjects, to observe the changes in these values with age, and to develop percentile distributions for these parameters. Whole-body resistance of 1838 healthy white men and 1555 women, aged 15-64 y, was determined by using four skin electrodes on the right hand and foot. FFM and FM were calculated according to formulas validated for the subject groups and analyzed for age decades. This is the first study to present BIA-determined age- and sex-specific percentiles for FFM, FM, and %FM for healthy subjects, aged 15-64 y. Mean FM and %FM increased progressively in men and after age 45 y in women. The results suggest that any weight gain noted with age is due to a gain in FM. In conclusion, the data presented as percentiles can serve as reference to evaluate the normality of body composition of healthy and ill subject groups at a given age.

Bedside determination of fluid accumulation after cardiac surgery using segmental bioelectrical impedance.

OBJECTIVES Bioelectrical impedance analysis (BIA) is based on the physical property of tissues to conduct electrical currents, impedance being inversely related to tissue fluid content. At high frequency, the electrical current flows across both intracellular and extracellular pathways, making the assessment of fat-free mass possible while a low-frequency current flows through the extracellular space. Similarly, segmental BIA may be used to assess segmental body fluid repartition. The aim of this study was to assess fluid accumulation after cardiac surgery by multiple frequency segmental BIA. DESIGN Observational, clinical study. SETTING A 17-bed, surgical intensive care unit in a university hospital. PATIENTS Twenty-six patients before and after open-heart surgery with cardiopulmonary bypass. INTERVENTIONS None. MEASUREMENTS AND MAIN RESULTS After surgery, fluid accumulation resulted in a decrease in whole-body and segmental bioelectrical impedance in the arm and in the trunk. There was a good correlation between the fluid accumulation measured by fluid balance and by whole-body or segmental impedance changes. The major part (71%) of fluid accumulation occurred in the trunk. Multiple frequency measurements did not indicate a fluid shift between the intra- and extracellular compartments. CONCLUSION Cardiac surgery produced a significant decrease in segmental trunk BIA, reflecting fluid accumulation at the trunk level.

Segmental bioelectrical impedance analysis to assess perioperative fluid changes.

Objectives Perioperative fluid accumulation determination is a challenge for the clinician. Bioelectrical impedance analysis (BIA) is a noninvasive method based on the electrical properties of tissues, which can assess body fluid compartments. The study aimed at assessing their changes in three types of surgery (thoracic, abdominal, and intracranial) requiring various regimens of fluid administration. Design Prospective descriptive trial. Patients A total of 26 patients scheduled for elective surgery were separated into three groups according to site of surgery: thoracic (n = 8), abdominal aortic (n = 8), and brain surgery (n = 10). Setting University teaching hospital. Intervention None. Measurements Whole body, segmental (arm, trunk, and legs) BIA at multiple frequency (0.5, 50, 100 kHz) was used to assess perioperative fluid accumulation after surgery. The fluid balances were calculated from the charts. Results The patients were aged 62 ± 4 yrs. Fluid balances were 4.8 ± 1.0 L, 4.1 ± 0.5 L, and 1.9 ± 0.3 L, respectively, in the three groups. In trunk surgery patients, fluid accumulation was detected as a drop in impedance in the operated area at all frequencies. In the operated area, there was an expansion of both intra- and extracellular compartments. A reduction in high frequencies’ impedance in the legs was only detected after aortic surgery. Fluid accumulation and trunk impedance changes were strongly correlated. Neurosurgery only induced minor body fluid changes. Conclusions Segmental BIA is able to detect and localize perioperative fluid accumulation. It may become a bedside tool to quantify and to localize fluid accumulation.

Epidural Analgesia in Cardiac Surgery: An Updated Risk Assessment

INTRODUCTION The use of epidural anesthesia carries risks that have been known for 50 years. The debate about the use of locoregional technique in cardiac anesthesia continues. The objective of this report is to estimate the risks and their variability of a catheter-related epidural hematoma in cardiac surgery patients and to compare it with other anesthetic and medical procedures. METHODS Case series reporting the use of epidural anesthesia in cardiac surgery were researched through Medline. Additional references were retrieved from the bibliography of published articles and from the internet. Risks of complications in other anesthetic and medical activity were retrieved from recent reviews. RESULTS Based on the present evidence, the risk of epidural hematoma in cardiac surgery is 1:12,000 (95% CI of 1:2100 to 1:68,000), which is comparable to the risk in the nonobstetrical population of 1:10,000 (95% CI 1:6700 to 1:14,900). The risk of epidural hematoma is comparable to the risk of receiving a wrong blood product or the yearly risk of having a fatal road accident in Western countries. CONCLUSIONS The risk of a hematoma after epidural in cardiac surgery is comparable to other nonobstetrical surgical procedures. Its routine application in a controlled setting should be encouraged.

The Analgoscore: A Novel Score to Monitor Intraoperative Nociception and its Use for Closed-Loop Application of Remifentanil

Purpose . Measuring pain during general anesthesia is difficult because communication with the patient is impossible. The focus of this project is the evaluation of an objective score (‘Analgoscore’ TM ) of intraoperative nociception based on mean arterial pressure (MAP) and heart rate (HR). The Analgoscore is used for closed-loop application of remifentanil. Methods . The Analgoscore ranges from -9 (too profound analgesia) to 9 (too superficial analgesia) in increments of 1, with -3 to +3 representing excellent pain control, -3 to -6 and 3 to 6 good pain control, and -6 to -9 and 6 to 9 insufficient pain control. According to the zone of pain, a remifentanil infusion was either closed-loopadministered (Closed-loop-group) or manually administered by the same anesthesiologist (Control group). The percentage of anesthetic time within the different control zones was recorded as well as the variability of MAP and HR and compared between the two groups. Data presented as means ± standard deviation. Results . In the closed-loop group, 16 patients (5 f, 11 m; age 49 ± 21 y) underwent anesthesia of 111 ± 44 min, and received a dose of remifentanil of 0.13 ± 0.08 μg/kg/min. During 84%, 14% and 0.5% of the total anesthesia time, the Analgoscore showed excellent, good or insufficient pain control, respectively. During 70% of the time, MAP ranged from -5% to 5%, during 21% of the time it ranged from - 10% to -5% and from 5% to 10% and during 9% of the time, it ranged from -20% to -10% and from 10% to 20% below or above the target values. Heart rate was within 10% of target value in 99% of the total anesthesia time. Artifacts were recorded only 1.5% of the time. The control group of eleven patients (4 f, 7 m; age 57 ± 16 y) underwent anesthesia of 110 (25) min; remifentanil of 0.17 (0.1) μg/kg/min was infused. Excellent control was obtained 79% of the time, whereas good control and insufficient control yielded 16% and 0%, respectively. Artifacts were recorded 5% of the time. Discussion . The Analgoscore is a novel score of intraoperative nociception based on blood pressure and heart rate. Remifentanil was successfully closed-loop-administered using this score. The closed-loop system provided equal hemodynamic stability to meticulous manual administration of remifentanil.

A novel approach for pain management in cardiac surgery via median sternotomy: bilateral single-shot paravertebral blocks.

Regional analgesia has entered cardiac anesthesia in the form of spinal or epidural analgesia. However, the risk of spinal or epidural hematoma is a constant worry. Alternative regional techniques might be applicable in cardiac surgery. The purpose of this study is to present a novel technique of bilateral single-shot paravertebral blocks (BSS-PVB) for cardiac surgery via median sternotomy and compare its efficacy versus high thoracic epidural analgesia (TEA). Fifty-two patients were compared in this prospective cohort audit. In 26 patients, cardiac surgery was performed using low-dose fentanyl/BSS-PVB (bilateral blocks of 3 mL bupivacaine 0.5% each, T1-7) and general anesthesia; in another 26 patients, TEA (bupivacaine 0.125% at 10 mL/hour) and general anesthesia were used. Patients were assigned to cohorts according to their preoperative data and types of surgery. All patient data are shown as mean +/- SD; pain scores were compared between groups using the t test immediately, 6 hours, and 24 hours after surgery (P < .05). In the BSS-PVB-group (19 men, 7 women), mean age was 65 +/- 11 years, weight 74 +/- 16 kg, ejection fraction 59% +/- 12%, and duration of surgery 130 +/- 27 minutes; in the TEA-group (17 men, 9 women), mean age was 63 +/- 10 years, weight 75 +/- 16 kg, ejection fraction 58% +/- 12%, and duration of surgery 113 +/- 27 minutes. These data and preoperative comorbidity variables were not significantly different between the two groups. In each group, 18 patients underwent off-pump coronary artery bypass grafting, 3 on-pump and 5 mitral valve replacements. All patients were successfully immediately extubated. Postoperative pain scores were at any point significantly lower with TEA, immediately at 2.4 +/- 2.2 versus 3.7 +/- 2.6, at 6 hours at 1.1 +/- 1.5 versus 2.4 +/- 1.8, and at 24 hours at 1.0 +/- 1.4 versus 2.3 +/- 1.6 (0 = no pain, 10 = maximum pain). There was no complications related to epidural catheter placement or BSS-PVB. Using both techniques, immediate extubation after cardiac surgery is feasible; TEA provides better pain relief after cardiac surgery than BSS-PVB.

Subcutaneous cervical and facial emphysema with the use of the Bonfils fiberscope and high-flow oxygen insufflation.

We present a case in which use of the Bonfils retromolar intubation fiberscope resulted in cervical and facial subcutaneous emphysema. The patient was a 75-yr-old woman with Mallampati Grade I airway. The Bonfils retromolar intubation fiberscope was used for teaching purposes. Flow on the oxygen port of the fiberscope was set at 10 L/min. Immediately after insertion of the scope, her whole face and cervical skin showed severe subcutaneous emphysema. The patient was intubated conventionally and the emphysema resolved within 24 h. Subcutaneous emphysema after air insufflation is known from dental procedures with air entering through holes in the teeth. In our case, the oxygen insufflation was sufficient to create emphysema, probably through tiny mucosal lesions.

Pharmacologic support of the failing circulation: practice, education, evidence, and future directions.

F ollowing a physiologic stress, the organism initiates the socalled acute phase response, which involves inflammatory mediators, hormones (thyroid hormones, steroids, sexual hormones, insulin), and the autonomic nervous system. Pharmacologic support of the failing circulation has been debated for 40 yrs, and catecholamines have been used for near a century to support it (1, 2). These physiologic neurohumoral mediators are mandatory to be adapted to terrestrial life as, for example, the massive catecholamine surge necessary to adapt from an intrauterine to an extrauterine life in which umbilical cord catecholamine levels correlate with perinatal stress (3). Actually, several agents are available with different pharmacologic spectra. Among catecholamines, dopamine, dobutamine, epinephrine, and norepinephrine are the most used drugs. The SOAP initiative is a “snapshot” of all patients admitted to 200 intensive care units (ICUs) across Europe during 2 wks, and has recently been published in the journal (3a). In the present issue of Critical Care Medicine, Dr. Sakr and colleagues (4) present a secondary analysis focusing on hemodynamic support using the database. They isolated patients receiving catecholamines and analyzed their survival according to the drug received. Other aspects from the SOAP survey were published as abstracts (5–8) or articles assessing specific points such as the pulmonary artery catheter (9).

Microcirculatory response during on-pump versus off-pump coronary artery bypass graft surgery.

Objectives: The use of cardiopulmonary bypass (CPB) during coronary artery bypass graft surgery (CABG) is associated with a systemic inflammatory response, resulting in altered microcirculation. The aim of this study was to evaluate whether beating heart surgery can preserve the microcirculation. Methods: Sublingual microcirculation was characterized by a Sidestream Darkfield Imaging Microscope during off-pump (OPCABG) and on-pump (ONCABG) surgery. Microcirculatory parameters were evaluated during eight precise perioperative time points. Results: The quality of the microcirculation decreased during early ONCABG. OPCABG resulted in a significantly better microcirculation compared to ONCABG for three of six parameters during surgery. However, by the end of surgery and postoperatively, the microcirculatory parameters were no different between the groups. Conclusions: While the results do not show a marked preservation of the microcirculation during and after OPCABG compared to ONCABG, they coincide with the body temperature fluctuations of each group during and after surgery. Our work suggests that active warming could impact the microcirculation parameters.

Microcirculation: more questions than answers.

U ntil recently, microcirculation was a sort of black box between the arterial and venous compartment. Pulmonary artery catheters and associated techniques can investigate the upstream part whereas the downstream part is estimated using organ function, SvO2 or lactate. This black box played a key role in exchange with tissues and is considered the motor of disease, especially in septic shock. Except using invasive animal experiments such as in vivo cremaster microscopy, little data were available to see inside the black box. Ten years ago, laser Doppler allowed to measure red blood cell velocities in the small arteries and capillaries oriented toward the probe, such as in the digestive tract. Orthogonal polarization spectroscopy, further refined in sidestream dark field (SDF) microscopy allows to visualize directly the blood flowing in a thin mucosa (1). By using a wavelength absorbed by hemoglobin, red blood cell appears dark and this allows us to measure the diameter of the capillaries, the type and velocity of flow. The explored area corresponds to roughly 0.7 mm (940 750 m). Numerous investigations are published, showing the effect of specific pathology or therapeutic intervention on microcirculation. Interestingly, changes in the microcirculation can occur without changes in macrocirculation (1), the latter being defined as flow/pressure/oxygen content through the aortic valve. Persistent alterations in microcirculations, despite correction of “macrocirculatory” parameters, are associated with worse prognosis on septic shock (2). Microcirculatory alteration in the early postoperative period is associated with an increased risk of complications, despite no changes in cardiac output or oxygen transport (3).