Melike Cengiz

Parameterization of red blood cell elongation index – shear stress curves obtained by ektacytometry

Abstract Measurement of red blood cell (RBC) deformability by ektacytometry yields a set of elongation indexes (EI) measured at various shear stresses (SS) presented as SS-EI curves, or tabulated data. These are useful for detailed analysis, but may not be appropriate when a simple comparison of a global parameter between groups is required. Based on the characteristic shape of SS-EI curves, two approaches have been proposed to calculate the maximal RBC elongation index (EImax) and the shear stress required for one-half of this maximal deformation (SS1/2): (i) linear Lineweaver-Burke (LB) model; (ii) Streekstra-Bronkhorst (SB) model. Both approaches have specific assumptions and thus may be subject to the measurement conditions. Using RBC treated with various concentrations of glutaraldehyde (GA) and data obtained by ektacytometry, the two approaches have been compared for nine different ranges of SS between 0.6–75 Pa. Our results indicate that: (i) the sensitivity of both models can be affected by the SS range and limits employed; (ii) over the entire range of SS-data, a non-linear curve fitting approach to the LB model gave more consistent results than a linear approach; (iii) the LB method is better for detecting SS1/2 differences between RBC treated with 0.001–0.005% glutaraldehyde (GA) and for a 40% mixture of rigid cells but is equally sensitive to SB for 10% rigid cells; and (iv) the LB and SB methods for EImax are equivalent for 0.001% and 0.003% GA and 40% rigid, with the SB better for 0.005% GA and the LB better for 10% rigid.

The routine use of pediatric airway exchange catheter after extubation of adult patients who have undergone maxillofacial or major neck surgery: a clinical observational study

IntroductionWe conducted the present study to determine the usefulness of routinely inserting a pediatric airway exchange catheter (PAEC) before tracheal extubation of adult patients who had undergone maxillofacial or major neck surgery and have risk factors for difficult reintubation.MethodsA prospective, observational and clinical study was performed in the 25-bed general intensive care unit of a university hospital. Thirty-six adult patients who underwent maxillofacial or major neck surgery and had risk factors for difficult reintubation were extubated after insertion of the PAEC.ResultsFour of 36 (11.1%) patients required emergency reintubation after 2, 4, 6 and 18 hours after tracheal extubation, respectively. Reintubation of these patients, which was thought to be nearly impossible by direct laryngoscopy, was easily achieved over the PAEC.ConclusionThe PAEC can be a life-saving device during reintubation of patients with risk factors for difficult reintubation such as laryngeo-pharyngeal oedema due to surgical manipulation or airway obstruction resulting from haematoma and anatomic changes. We therefore suggest the routine use of the PAEC in patients undergoing major maxillofacial or major neck surgery.

Effects of storage duration and temperature of human blood on red cell deformability and aggregation

Blood samples used in hemorheological studies may be stored for a period of time, the effects of storage have yet to be fully explored. This study evaluated the effects of storage temperature (i.e., 4 degrees C or 25 degrees C) and duration on RBC deformability and aggregation for blood from healthy controls and from septic patients. Our results indicate that for normal blood, RBC deformability over 0.3-50 Pa is stable up to six hours regardless of storage temperature; at eight hours there were no significant differences in EI but SS1/2 calculated via a Lineweaver-Burk method indicated impaired deformability. Storage temperature affected the stable period for RBC aggregation: the safe time was shorter at 25 degrees C whereas at 4 degrees C aggregation was stable up to 12 hours. Interestingly, blood samples from septic patients were less affected by storage. Blood can thus be stored at 25 degrees C for up to six hours for deformability studies, but should be limited to four hours for RBC aggregation; storage at 4 degrees C may prolong the storage period up to 12 hours for aggregation but not deformability measurements. Therefore, the time period between sampling and measurement should be as short as possible and reported together with results.

Influence of tourniquet application on venous blood sampling for serum chemistry, hematological parameters, leukocyte activation and erythrocyte mechanical properties

Abstract Background: Venous blood sampling is usually performed using a tourniquet to help locate and define peripheral veins to achieve successful and safe venipuncture. Despite widespread usage of tourniquets for venipuncture by medical and laboratory staff, very few are aware of the effects of tourniquet application on laboratory parameters. In addition, definitive guidelines regarding when and how to use a tourniquet for blood sampling are lacking. The aim of the present study was to define the optimal sampling time after tourniquet removal to avoid adverse impact on laboratory analytes. Methods: Blood oxygen and carbon dioxide partial pressure, pH, oxyhemoglobin saturation (satO2), hematological parameters, serum electrolyte concentrations, erythrocyte, deformability and aggregation, leukocyte activation and nitrite/nitrate concentrations obtained 180 s after tourniquet release were compared with baseline values for 10 healthy subjects. Results: Blood gases, hematological parameters and serum electrolyte levels were not affected by the application and removal of a tourniquet. However, there were significant decreases in erythrocyte deformability at 90, 120, 180 s, and increases in erythrocyte aggregation at 5 and 30 s following removal of the tourniquet. A significant increase in granulocyte respiratory burst at 60 s was observed, confirming leukocyte activation due to application of the tourniquet. There were no significant alterations of blood nitrite/nitrate levels. Conclusions: Our blood sampling technique which mimicked the application and release of a tourniquet indicated unaltered values for routine blood gases, hematological testing and serum electrolyte levels. Conversely, hemorheological measurements can be affected. Therefore, it is strongly recommended that tourniquet application should be avoided during blood sampling or, if this is not possible, the procedure should be well standardized and details of the sampling method should be reported. Clin Chem Lab Med 2009;47:769–76.

Repeat percutaneous tracheostomy in the neurocritically ill patient.

IntroductionPercutaneous tracheostomy is a widely used and accepted method for long-term mechanical ventilation and airway protection. Neurocritically ill patients sometimes require repeat tracheostomy, which is traditionally considered a relative contraindication for percutaneous procedure. The aim of this study was to determine the safety of repeat percutaneous tracheostomy in neurocritically ill patients with a history of previous tracheostomy.MethodsIn the 16-bed academic neurointensive care unit, we prospectively enrolled patients who needed new tracheostomy placement for airway protection or prolonged mechanical ventilation and had previously undergone percutaneous tracheostomy placement. We collected data on indications, procedure, periprocedural complications, and outcome of repeated tracheostomy.ResultsBetween January 2001 and October 2005, we enrolled 12 consecutive patients (mean age 35.4±7.0 years) who underwent repeat percutaneous tracheostomy. Head injury was the most common underlying diagnosis (seven patients, 58%). Tracheostomy tube placement was easy and successful in all patients, and none of the patients needed conversion to surgical tracheostomy. In three patients, ultrasound-guided needle aspiration was used before the procedure to confirm the position of the trachea. No patients died or experienced serious complication related to the procedure. Two patients (17%) had a minor periprocedura bleeding, which was controlled with local compression. Long-term outcome was poor, with only two patients alive and off the ventilator at hospital discharge, both with serious disability.ConclusionRepeat percutaneous tracheostomy can be performed safely in neurocritically ill patients who have undergone previous tracheostomy.

A botulism outbreak from roasted canned mushrooms

Food-borne botulism is a rare disease that results from ingestion of the toxins produced by Clostridium botulinum. The most common cause of the disease is the consumption of home-canned foods prepared under inappropriate conditions, especially in rural environments. In this report, a food-borne botulism outbreak potentially caused by roasted home-canned mushrooms is evaluated and the major reasons for delayed diagnosis are emphasized. The clinical features, symptoms and prognosis of the five botulism patients involved in this outbreak are presented. The clinical progressions, treatments, durations of mechanical ventilation, intensive care unit stays and hospital stays of the three patients admitted to Akdeniz University Hospital are reported.

Retrospective Analysis of Prognostic Factors of Severe Traumatic Brain Injury in a University Hospital in Turkey.

AIM To examine the use of prognostic factors such as age, Glasgow Coma Scale (GCS) score, pupil reactivity and computerized tomography (CT) findings for predicting the prognosis of severe traumatic brain injury (TBI) patients in Turkey. MATERIAL AND METHODS We retrospectively evaluated TBI patients who were accepted to Akdeniz University Intensive Care Unit between 1 January 2007 and 31 December 2009. Patient data were collected from the hospital information system. Marshall CT classification was performed and CT findings were noted. The Glasgow outcome scale (GOS) score of patients was calculated according to their 6-months follow up. RESULTS A total of 101 patients with severe TBI were studied. The mean age of the patients was 34.7 ± 14.1 years. Of these, male patients (81.2%) were dominant and road accidents (83.2%) were the most common mechanism of TBI development. In addition, poor neurological outcome was detected in 58.4% of the patients and 29 patients (28.7%) died. The mechanism of injury (p = 0.34), gender (p = 0.64) or age (p = 0.34) did not lead to a difference in neurologic outcomes while the GCS score (p = 0.01), pupillary reactivity (p = 0.000), Marshall CT classification (p = 0.01) and the presence of traumatic subarachnoid haemorrhage (p = 0.04) affected the GOS scores. CONCLUSION In our study, GCS score, CT findings and pupil reactivity were prominent as prognostic factors, but a relationship between age and prognosis was not observed.

A web-based intensive care clinical decision support system: From design to evaluation

The aim of this study is to develop and evaluate a web-based clinical decision support system (CDSS) containing clinical guidelines and protocols that will support intensive care unit (ICU) providers in making decisions more effectively and quickly. First, a survey was carried out with 38 physicians in order to determine their preferences, needs and concerns regarding decision support tools. After the survey, guidelines were prepared by a group of specialists in ICU, and a medical informatician converted the guidelines into algorithm forms. Ten CDSS were developed using the algorithms, and placed onto the Intensive Care Decision Support Website (ICDSW). In order to evaluation of the website, 15 physicians were asked to answer 10 questions in 10 different scenarios first using a paper-based approach, then with ICDSW. When the answers were analyzed, it was found that the answers given by using ICDSW were significantly better than the paper-based approach (p <  0.001). However, there was no significant difference in terms of the time needed to answer the questions (p  =  0.138). The usability score of the website was 85.6  ±  8.89. The study demonstrated the successful implementation of an ICDSW within intensive care units.

Maxillary sinusitis in patients ventilated for a severe head injury and with nostrils free of any foreign body.

BACKGROUND This study aims to determine the frequency of maxillary sinusitis in the patients with traumatic head injury and nostrils free of any foreign body. In addition, the sensitivity and specificity of ultrasonography (US) for the detection of the presence of fluid in maxillary sinuses were evaluated. PATIENTS AND METHODS Forty patients with severe traumatic head injury were included in the study. The patients who had displaced maxillary sinus fracture at the medial wall and naso-tracheal and/or naso-gastric tube were excluded. Paranasal computed tomography (CT) was performed along with the routine cranial CT scanning or in case of unknown source of infection and compared with the results of ultrasonographic examination of maxillary sinuses performed by a single radiologist who was unaware of the CT results. In the patients, who had clinical and radiological signs of sinusitis, a trans-nasal puncture was performed using sinoject (SinoJect, ATOS Medical, Sweden), a spring-activated puncture instrument, to take a sample for microbiologic examination and to drain maxillary sinuses. RESULTS Eighty-five percent of the patients were tracheotomised on the fifth day (on average) of their intensive care unit (ICU) stay. The frequency of sinusitis in the study group was found to be 32.5% (13 patients). The most frequently isolated species were Pseudomonas spp. (37.5%), Escherichia coli (20.8%) and Peptostreptococcus (16.7%). Five of the aspirates were polymicrobial. The sensitivity, specificity, positive predictive value and negative predictive value of B-mode US, compared with CT for the detection of fluid presence in maxillary sinuses in a 100 maxillary sinus examinations, were 92.2%, 81.6%, 83.9% and 90.9%, respectively. CONCLUSION Maxillary sinusitis should be considered as a source of infection or sepsis in patients with traumatic head injury because of its high frequency. US is likely to be used as the first-line diagnostic tool for the determination of fluid in maxillary sinuses, especially in patients who do not require CT or cannot be transported to a radiology unit for CT.

Effect of magnesium supplementation on blood rheology in NOS inhibition-induced hypertension model

This study investigated the effects of magnesium on blood rheological properties and blood pressure in nitric oxide synthase (NOS) inhibition-induced hypertension model. Hypertension was induced by oral administration of the nonselective NOS inhibitor N-nitro-L-arginine methyl ester (L-NAME, 25 mg/kg/day) for 6 weeks and systolic blood pressure was measured by the tail-cuff method. The groups receiving magnesium supplementation were fed with rat chow containing 0.8% magnesium oxide during the experiment. At the end of experiment, blood samples were obtained from abdominal aorta, using ether anesthesia. Plasma and erythrocyte magnesium levels were determined by the atomic absorption spectrometer. RBC deformability and aggregation were determined by rotational ektacytometry. Plasma fibrinogen concentration was evaluated by ELISA. Whole blood and plasma viscosities were determined by viscometer and intracellular free Ca++ level was measured by using spectroflurometric method. Blood pressure was elevated in hypertensive groups and suppressed by magnesium therapy. Plasma viscosity and RBC aggregation were found to be higher in hypertensive rats than control animals and these parameters significantly decreased in magnesium supplemented hypertensive animals. Other measurements were not different between experimental groups. These results confirm that blood pressure, plasma viscosity and RBC aggregation increased in NOS inhibition-induced hypertension model and oral magnesium supplementation improved these parameters.