Can we rely on arterial line sampling in performing activated plasma thromboplastin time after cardiac surgery?

BACKGROUND AND OBJECTIVE: Arterial catheters are routinely used to sample blood for clotting studies in most cardiothoracic intensive care units. The clotting profile in surgical bleeding after cardiac surgery influences further management. Aspiration and discard of a certain amount of blood from the line, prior to sampling, are assumed to clear heparin contamination. We have investigated this assumption through analysis of the clotting profile by simultaneous arterial line and peripheral venous samples. METHODS: The morning following cardiac surgery, simultaneous arterial line and peripheral venous blood samples were taken for activated plasma thromboplastin time (APTT) ratio and international normalized ratio (INR) in 49 randomly selected patients. Also, a thromboelastogram analysis (TEG) (n = 7) was made. A survey of 22 UK cardiothoracic intensive care units was carried out to determine the practice for the withdrawal of blood for clotting studies. RESULTS: The median arterial APTT ratio value was 1.32 +/- 0.52 as compared to the median peripheral APTT ratio value which was 1.1 +/- 0.24 (P < 0.001). INR values were statistically similar by both routes. Heparin contamination was confirmed by TEG which revealed that the R-value for arterial catheter blood samples without heparinase in the cup was higher (406.00 +/- 64.44 s) compared with the value for arterial samples with heparinase in the cup (318.28 +/- 47.26s, P < 0.05). The survey of 22 UK cardiothoracic intensive care units showed that heparinized arterial lines were by far the commonest ports used for blood withdrawal for the measurement of APTT ratio results. CONCLUSIONS: Samples withdrawn from heparinized arterial lines cannot be relied upon for APTT ratio results.     

Prediction of activity energy expenditure using accelerometers in children

PURPOSE: To validate two accelerometer-based activity monitors as measures of children's physical activity using energy expenditure as the criterion measure. METHODS: Actiwatch (AW) and Actical (AC) activity monitors were validated against continuous 4-h measurements of energy expenditure (EE) in a respiratory room calorimeter and 1-h measurements in an exercise laboratory using a portable calorimeter and treadmill in 32 children, ages 7-18 yr. The children performed structured activities including basal metabolic rate (BMR), playing Nintendo, using a computer, cleaning, aerobic exercise, ball toss, treadmill walking, and running. Equations were developed to predict activity energy expenditure (AEE = EE - BMR), and physical activity ratio (PAR = EE/BMR) from a power function of AW or AC, and age, sex, weight, and height. Thresholds were determined to categorize sedentary, light, moderate, and vigorous levels of physical activity. RESULTS: Activity counts accounted for the majority of the variability in AEE and PAR, with small contributions of age, sex, weight, and height. Overall, AW equations accounted for 76-79% and AC equations accounted for 81% of the variability in AEE and PAR. Relatively wide 95% prediction intervals suggest the accelerometers are best applied to groups rather than individuals. Sensitivities were higher for the vigorous threshold (97%) than the other thresholds (86-92%). Specificities were on the order of 66-73%. The positive predictive values for sedentary, light, moderate, and vigorous categories were 80, 66, 69, and 74% for AW, respectively, and 81, 68, 72, 74% for AC, respectively. CONCLUSION: Both accelerometer-based activity monitors provided valid measures of children's AEE and PAR, and can be used to discriminate sedentary, light, moderate, and vigorous levels of physical activity but require further development to accurately predict AEE and PAR of individuals.     

Secondary ultrasound examination increases the sensitivity of the FAST exam in blunt trauma

INTRODUCTION: Approximately one third of stable patients with significant intra-abdominal injury do not have significant intraperitoneal blood evident on admission. We hypothesized that a delayed, repeat ultrasound study (Secondary Ultrasound--SUS) will reveal additional intra-abdominal injuries and hemoperitoneum. METHODS: We performed a prospective observational study of trauma patients at our Level I trauma center from April 2003 to December 2003. Patients underwent an initial ultrasound (US), followed by a SUS examination within 24 hours of admission. Patients not eligible for a SUS because of early discharge, operative intervention or death were excluded. All US and SUS exams were performed and evaluated by surgical/emergency medicine house staff or surgical attendings. RESULTS: Five hundred forty-seven patients had both an initial US and a SUS examination. The sensitivity of the initial US in this patient population was 31.1% and increased to 72.1% on SUS (p < 0.001) for intra-abdominal injury or intra-abdominal fluid. The specificity for the initial US was 99.8% and 99.8% for SUS. The negative predictive value was 92.0% for the initial US and increased to 96.6% for SUS (p = 0.002). The accuracy of the initial ultrasound was 92.1% and increased to 96.7% on the SUS (p < 0.002). No patient with a negative SUS after 4 hours developed clinically significant hemoperitoneum. CONCLUSION: A secondary ultrasound of the abdomen significantly increases the sensitivity of ultrasound to detect intra-abdominal injury.     

Port catheter placement by nephrologists in an interventional nephrology training program

We retrospectively reviewed all subcutaneous single- and double-lumen port catheters (PCs) inserted by interventional nephrologists at our institution to determine the success rate, immediate and late complications, and functional life. From January 2000 to August 2002, 187 PCs were placed in 187 patients (42% males, 51% Caucasians, mean age 50 +/- 14 years). There were no immediate complications related to the procedure such as hemorrhage, pulmonary embolism, or pneumothorax. There were a total of 35,078 catheter-days of follow-up. Sixteen catheters were removed during the observation period: three because of infection, seven after completion of chemotherapy, and six for other reasons. The remaining PCs are either functioning or the patients have died. The initial success rate was 100%. Kaplan-Meier analysis showed a 30-day survival of 97% and a 1-year survival of 92%. Interventional nephrologists, who have adequate training in central venous tunneled cuffed catheter placements, can successfully place PCs, with excellent success and minimal complications.     

Design of braided composite cardiovascular catheters based on required axial, flexural, and torsional rigidities

Cardiovascular catheterization is a common medical procedure. A single braided catheter with different rigidities at the proximal and distal ends can, if properly designed, provide the necessary control and flexibility and thus replace the current two-piece (external catheter/internal guidewire) system. An analytical model based on classical laminate plate theory was developed in order to predict the elastic properties of angle-plied, single-overlap two-dimensional fiber composite tubular braids, which are required for the determination of the axial, flexural, and torsional rigidities. In this work the analytical model has been used to design one-piece cardiovascular catheters with axial, flexural, and torsional rigidities similar to those values for existing two-piece catheters, thus validating the model as a tool for designing braided cardiovascular catheters.     

Influence of stressors on the rewarding effects of alcohol in Wistar rats: studies with alcohol deprivation and place conditioning

Rationale and objectives Studies on laboratory animals have provided conflicting results regarding the actions of stressors on the rewarding effects of alcohol. In the present study, we first examined the effects of footshock or social defeat, given during deprivation, on the alcohol deprivation effect (ADE). We then tested the effects of stressors on place conditioning to alcohol, another technique used to measure drug reward.Methods Male Wistar rats were trained to drink 10% alcohol in a 24 h access, free-choice design and received intermittent footshock or defeat 5 times during a 2-week alcohol deprivation period, followed by 2 weeks of free access to alcohol. There were three such cycles. In the place conditioning studies, animals received footshock, defeat, or no stress immediately prior to conditioning sessions where they received alcohol (0.6 or 1.0 g/kg, IP) or vehicle injections.Results Alcohol intake of footshock-treated animals was significantly higher than that of controls following the first and second, but not the third period of alcohol deprivation and stress exposure. Defeat caused a smaller increase in alcohol intake that was significant only after the first deprivation and stress cycle. In the place conditioning studies, we found that either stressor blocked the place aversion induced by 1.0 g/kg alcohol.Conclusions These results demonstrate that stressors can modify the rewarding and aversive properties of alcohol, measured using two different paradigms. Footshock and defeat produced transient, but significant increases in the magnitude of ADE, while exposure to either stressor reduced the aversive effects of a high dose of alcohol measured using the place conditioning paradigm.     

Effect of gestational age on cord blood plasma copper,zinc, magnesium and albumin

BACKGROUND: The transport of essential trace elements from mother to fetus varies throughout gestation, and the role of transport proteins in the neonate and the mother may change during pregnancy. Magnesium, often used as tocolytic agent, may reach the fetus and appear in cord blood at higher than normal concentrations. AIMS: To determine cord blood plasma zinc, copper and magnesium concentrations, as well as plasma albumin in premature and full-term newborns, and correlate these values with those of maternal blood plasma at birth. Also, to examine whether cord blood plasma concentration of these elements varies with gestational age. SUBJECTS: The 35 mother-infant pairs included: 11 in the 38-42-week gestational age (GA), 9 in the 34-37-week GA, 11 in the 29-33-week GA group and 4 in the 24-28-week GA. Magnesium for tocolysis was given to five of the mothers in the 29-33-week GA cohort and two of the women giving birth at 24-28-week GA. RESULTS: Trend analysis showed that while cord plasma zinc decreased with GA at birth, the reverse was observed for copper. There were no differences with GA either in maternal plasma zinc or copper. However, maternal ceruloplasmin tended to decrease with GA (P=0.0174). Maternal and cord blood plasma magnesium exhibited a strong correlation (r=0.942, P<0.001), as well as between cord plasma magnesium and zinc (r=0.448, P<0.01). CONCLUSIONS: While the vigorous mother-to-fetus uphill zinc transfer is clear throughout the last trimester, copper remains in cord blood plasma at much lower concentrations than in the mother, suggesting that prematurity may place the newborn infant at a greater risk than the term infant to copper deficiency. This situation, together with a reduced synthesis in the fetus of the transport protein ceruloplasmin, creates another potential challenge in the nutritional support of the premature infant.     

Successful orthotopic liver transplantation after trimethoprim-sulfamethoxazole associated fulminant liver failure

Trimethoprim-sulfamethoxazole (TMP-SMZ) is one of the most commonly used antibiotics. Although many of its adverse effects are well recognized, TMP-SMZ related hepatotoxicity is considered rare and is usually characterized by cholestasis or mixed hepatocellular-holestatic reactions. In this study, we describe the case of a previously healthy young man with acute fulminant liver failure caused by TMP-SMZ. The patient presented with complaints of 'flu-like' symptoms with myalgia and fever after taking TMP-SMZ for 7 d for otitis externa. The patient subsequently developed fever, worsening jaundice, and a rash on his neck and chest. Liver enzymes peaked on day 3 with alanine aminotransferase (ALT) 11,549, aspartate aminotransferase (AST) 23,289, alkaline phosphatase 245, and total bilirubin 10.3 mg/dL, with a conjugated bilirubin of 8.3 mg/dL, prothrombin time (PT) 60.5 s, partial normalized ratio (PTT) 49 s, and international normalized ratio (INR) 7.5. Of note, acetaminophen level on admission was undetectable. Serology for hepatitis A, B, C, cytomegalovirus, HIV, toxoplasmosis, and blood cultures were all negative. The patient developed hepatic encephalopathy with hallucination on day 4. Laboratory tests revealed a serum ammonia level of 190 U, serum creatinine kinase (CK) 10,466 (42 on admission), serum creatinine 8.2 mg/dL (1.2 on admission), and significant metabolic acidosis. Renal ultrasound was unremarkable. The patient was started on hemodialysis for acute renal failure. Meanwhile, liver transplantation assessment was also initiated. On day 8 post-admission (15 d after taking TMP-SMZ), the patient received a successful orthotopic liver transplant.     

Garlic prevents ultrastructural alterations caused by dehydration in mouse cerebral microvessels

Dehydration is known to significantly reduce both the time required for the first platelet aggregate and the time to full occlusion in photochemically-induced thrombosis, in vivo. Ultrastructural changes that contribute to such events remain unknown. Therefore, the effect of water deprivation for 24 hr, (as a model for dehydration) on the ultrastructure of mouse pial microvessels was investigated. The possible beneficial effect of garlic in preventing such ultrastructural changes was also investigated. Four groups of TO strain: control, control-garlic treated, dehydrated, and dehydrated-garlic treated male mice, 10/group, were used. Dehydration was induced by water deprivation for 24 hr. Garlic solution was i.p. injected at 0.1 ml/10g body weight. In urethane-anesthetized (2 mg/g, i.p.) mice, topical and transvessel bimodal fixation of pial microvessels was done with a phosphate buffered mixture of glutaraldehyde and paraformaldehyde, followed by a conventional electron microscopy procedure. Examination of control cerebral pial microvessels showed no evidence of cellular damage. Membranes of endothelial cells were intact. Within pial microvessels there was no evidence of platelet aggregation. Garlic treatments did not cause any ultrastructure abnormalities in control mice. Compared with control, dehydration caused the appearance of thrombi that consisted of platelet aggregates. Discoid platelets containing granules, spheroid degranulated platelets, and those with large pseudopodia were present in 80% of dehydrated mice. The venular endothelial surface of dehydrated mice revealed dilated profiles of endoplasmic reticulum and variously shaped vacuoles. Swelling of nuclear envelopes and mitochondrial distension were also present in dehydrated mice. Concomitant garlic treatment prevented most of these ultrastructural changes. These findings demonstrated the extent of damage to the pial microvessels in response to water deprivation and demonstrated the beneficial effect of garlic as a possible mean of protection against oncoming vascular pathology.