Biomedical subjects
Publications and source records attributed to H Singh.
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PURPOSE: Massive pulmonary embolus (PE) is often rapidly fatal. Surgical thrombectomy has a mortality rate as high as 74%. Multiple percutaneous methods have been tested with limited success. The purpose of this study was to evaluate the Arrow-Trerotola percutaneous thrombolytic device (PTD) for (i) the ability to clear pulmonary embolus and (ii) the effect on normal pulmonary vasculature. These were tested in a canine model. MATERIALS AND METHODS: Iatrogenic unilateral massive PEs were created in nine canines. These PEs were then treated with the PTD. The device was also activated in the normal pulmonary artery. Immediately after treatment, six animals were killed. Three animals were allowed to recover and underwent pulmonary arteriography 1 month later to evaluate pulmonary hypertension, stenosis, or occlusion; they were then killed. Autopsy specimens were evaluated for histologic evidence of acute or chronic vascular injury. RESULTS: Acutely, the PTD effectively thrombolysed the PE in all animals. Histologically, there was moderate intimal injury, but no evidence of pulmonary artery disruption. There was one device failure. One month after treatment, there was no radiographic evidence of pulmonary stenosis at device activation sites, no pulmonary hypertension, and only mild histologic evidence of scar formation. CONCLUSION: In preliminary animal testing, the PTD is safe and effective for treating large central pulmonary emboli. Human clinical trials are warranted.
PURPOSE: Significant inferior vena cava (IVC) filter migration has been associated with deployment of some filter types in IVCs measuring more than 28 mm in diameter at inferior vena cavography. The purposes of this study were to (a) determine if significant differences exist between IVC measurements obtained using a gold standard technique and two other widely accepted methods, and (b) if differences exist, how often do these differences cause incorrect IVC sizing around a diameter of 28 mm, with its associated filter migration issues. MATERIALS AND METHODS: One hundred thirteen consecutive inferior vena cavograms were retrospectively reviewed. The transverse diameter of the infrarenal IVC was determined by using a calibrated intravascular catheter (the gold standard), subtraction of 20% from the measured transverse IVC diameter on a cut-film radiograph, and a radiopaque ruler placed immediately posterior to the patient. RESULTS: The concordance correlation of the 20% magnification method versus internal calibration was 0.94. Kappa analysis to determine agreement at a diameter of 28 mm yielded a Kappa coefficient of 0.490. The concordance correlation of an external ruler versus internal calibration was 0.43, with a Kappa coefficient of 0. CONCLUSION: The poor Kappa correlations for both methods demonstrate that they are unreliable in identifying megacava. Inferior vena cavography prior to IVC filter placement should be performed with a calibrated intravascular catheter.
BACKGROUND: We studied the effect of variable doses of ketamine on the endpoints of hypnosis, e.g., unresponsiveness to verbal commands (UVC), loss of eyelash reflex (LER), and inhibition of body movement response with or without sneezing to nasal membrane stimulation (INBMR), and processed EEG variables, e.g., bispectral index (BIS), 95% spectral edge frequency (SEF) and median frequency (MF) during propofol infusion. METHODS: Forty-eight patients received either propofol infusion, 30 mg.kg-1.h-1 (Group P; n = 12) or ketamine bolus, 0.25, 0.5 or 0.75 mg i.v., followed by propofol infusion, 30 mg.kg-1.h-1 + variable dose ketamine infusion, 0.25, 0.5 or 0.75 mg.kg-1.h-1 (Groups PK0.25, PK0.5 and PK0.75; n = 12 each) until UVC, LER and INBMR. BIS, 95% SEF and MF values were monitored and recorded at the endpoints of hypnosis. Propofol and ketamine concentrations were measured at INBMR. RESULTS: Propofol infusion, 30 mg.kg-1.h-1, induced UVC, LER and INBMR at BIS: 65 +/- 2, 63 +/- 9 and 33 +/- 7; 95% SEF: 17 +/- 3, 17 +/- 4 and 14 +/- 3; and MF values of 5 +/- 2, 5 +/- 3 and 3 +/- 2, respectively. With adjunctive ketamine (Groups PK0.5 and PK0.75), the hypnotic endpoints were achieved at higher BIS and 95% SEF values and lower propofol doses and concentrations as compared to Groups P and PK0.25 (9.9 +/- 5.8 and 9.4 +/- 3.4 vs. 13.4 +/- 4.5 and 14 +/- 5.8 micrograms.ml-1). CONCLUSIONS: Our results suggest additive interaction between propofol and ketamine (Groups PK0.5 and PK0.75) for achieving the hypnotic endpoints; however, ketamine did not depress the EEG variables in proportion to its hypnotic effect. The paradoxically higher BIS and 95% SEF values at the hypnotic endpoints may be due to lower propofol concentrations and/or no effect of ketamine on the EEG variables.
Homozygosity for the methylenetetrahydrofolate reductase (MTHFR) gene C677T polymorphism may cause hyperhomocysteinaemia, a recognized risk factor for stroke, in individuals with folate deficiency. Homozygous sickle cell (SS) disease is associated both with increased demands for folic acid and a tendency to develop stroke. We therefore investigated a possible role of the MTHFR C677T polymorphism in SS disease patients with stroke. Investigation of the frequency of the polymorphism in 48 patients with stroke and in 48 age-, sex- and racially-matched SS controls without stroke failed to reveal a difference between the groups (Fisher exact test, P = 0.99). Homozygosity for the MTHFR C677T polymorphism is unlikely to be a risk factor for stroke in this population with SS disease.
One may have to use a monitor of cortical suppression to maintain the optimal level of sedation and hypnosis. The bispectral index (BIS), a processed EEG parameter, which incorporates coupling along with the frequency and amplitude of EEG waveforms, has been proposed as a measure of the pharmacodynamic anaesthetic effect on the central nervous system. The numerical value of BIS varies from 0 to 100 (no cerebral activity to fully awake patient). In order to achieve the desired level of propofol sedation or hypnosis, a target concentration of propofol at the effect site or in the blood must be delivered. Alternately, one may use BIS monitoring to monitor hypnosis or sedation levels or to reflect propofol concentrations in the blood. Significant correlations between plasma propofol concentrations and BIS values (r = 0.68-0.78) have been reported by many investigators. During propofol-induced sedation, BIS values may be maintained above 75 to prevent airway obstruction and hypoxia. During propofol intravenous anaesthesia, BIS values from 40 to 60 have been proposed to maintain the desired level of hypnosis, with values below 50 associated with an insignificant probability of recall. However, the major limitation of the BIS monitor (monitor of hypnosis) relates to the fact that balanced anaesthesia comprises hypnosis, areflexia and analgesia and requires the administration of hypnotic agents, muscle relaxants and analgesics to achieve the desired clinical effects. Therefore, besides using the BIS value guidelines, one may also consider the haemodynamic, autonomic and somatic responses of the patient, the anaesthetic technique and the surgical interventions before deriving definite conclusions about the overall anaesthetic state of the patient.
Hypnotic endpoints and/or EEG variables, e.g. bispectral index, 95% spectral edge frequency and median frequency, have been studied to monitor anaesthetic (hypnotic) depth during total intravenous anaesthesia. In this study, the relation between the hypnotic endpoints of unresponsiveness to verbal commands, loss of eyelash reflex and body movement response to mechanical nasal membrane stimulation vs. bispectral index, 95% spectral edge frequency and median frequency during propofol anaesthesia with or without fentanyl is presented. Forty-two patients were randomly assigned to receive either propofol infusion, 30 mg kg-1 h-1 (n = 22), or propofol infusion, 30 mg kg-1 h-1 + fentanyl bolus, 2 micrograms kg-1 i.v. (n = 20). Bispectral index, 95% spectral edge frequency and median frequency and propofol doses were monitored and recorded at unresponsiveness to verbal commands, loss of eyelash reflex and inhibition of nasal body movement response. The bispectral index values were significantly higher in the propofol + fentanyl compared with the propofol group, i.e. 74.7 +/- 10.9, 73.1 +/- 10.5 and 47.1 +/- 9.2 vs. 65.8 +/- 9.8, 59.6 +/- 10 and 33.8 +/- 5.7 at unresponsiveness to verbal commands, loss of eyelash reflex and inhibition of nasal body movement response respectively. Doses of propofol for achieving the hypnotic endpoints were significantly lower in the propofol + fentanyl compared with the propofol group. Plasma propofol concentrations at inhibition of nasal body movement response were lower in the propofol + fentanyl compared with the propofol group (9.2 +/- 2.0 micrograms mL-1 vs. 14.1 +/- 4.2 micrograms mL-1). Our results suggest that fentanyl pretreatment potentiates the effects of propofol and achieves the hypnotic endpoints at higher bispectral index values and lower propofol doses and concentrations (measured at inhibition of nasal body movement response).
We studied the movement response to skin incision in 68 adult (males/females) ASA I-II patients receiving propofol +/- fentanyl intravenous anaesthesia using the bispectral index and 95% spectral edge frequency monitoring with an A-1050 EEG monitor. Following Ethics Committee approval, patients were randomly assigned to one of the following four treatments: Group P (n = 17): propofol infusion, 1 mg kg-1 min-1 intravenous for 2 min, followed by propofol infusion, 200 micrograms kg-1 min-1, until skin incision; Group PF1 (n = 17): fentanyl bolus, 1 microgram kg-1 intravenous + propofol infusion as in Group P; Group PF2 (n = 17): fentanyl bolus, 2 micrograms kg-1 intravenous + propofol infusion as in Group P; and Group PF3 (n = 17): fentanyl bolus, 3 micrograms kg-1 intravenous + propofol infusion as in Group P. The bispectral index and 95% spectral edge frequency were monitored continuously and recorded prior to induction of anaesthesia (base-line) and at skin incision. Twelve, 10, 4 and 4 patients responded to skin incision in Groups P, PF1, PF2 and PF3, respectively (P and PF1 vs. PF2 or PF3; P = 0.0001, and 0.006). The bispectral index and 95% spectral edge frequency were significantly lower at skin incision compared with the base-line values in all the four treatment groups. However, only bispectral index values were significantly lower in the nonmovement as compared with the movement (M) category (32.6 +/- 8.9 vs. 37.4 +/- 10.3; P = 0.04). Though deeper levels of hypnosis to lower bispectral index and 95% spectral edge frequency values may be effective in preventing the movement response to skin incision, provision of adequate analgesia rather than lower bispectral index and 95% spectral edge frequency (clinical maintenance) values may be more reliable for preventing the response to skin incision as bispectral index and 95% spectral edge frequency measure the hypnotic component of the anaesthetic effect. Lower bispectral index values may be more discriminatory as compared with 95% spectral edge frequency values for preventing the movement response to skin-incision.
The poultry industry in subtropical climates faces the challenges of climate and variable feed quality, in addition to those challenges encountered in temperate zones. These challenges aggravate the problem associated with the progressive decline in reproductive performance due to genetic selection for growth and yield traits. Heat stress is the major cause of lower fertility in both males and females, regardless of age. Under such situations, nongenetic factors play critical roles in maintaining or increasing reproductive efficiency in broiler breeders. The relatively low cost of skilled labor in subtropical countries enables consideration of artificial insemination for hens in cages or on the floor as an alternative to conventional floor mating, and also identification and culling of males producing few sperm or sperm of inferior quality. Artificial insemination allows extended use of superior males and setting up rooster stud farms. Such operations, plus selection for economic growth and carcass traits in pedigree lines known to tolerate the climate, will be important for continued growth of market share.
OBJECTIVE: This study was conducted to stimulate respiratory muscles by functional magnetic stimulation (FMS) of the spinal nerves (T1-L5) to obtain maximum expiratory function. DESIGN: A prospective before and after trial. SETTING: Functional Magnetic Stimulation Laboratory, Spinal Cord Injury Service, VA Palo Alto Health Care System, Palo Alto, CA. PARTICIPANTS: Twelve normal able-bodied subjects. INTERVENTION: A commercially available magnetic stimulator with a round magnetic coil (MC) was used. Respiratory muscle activation was achieved by placing the MC at each spinous process ranging from T1 to L5 vertebral levels. MAIN OUTCOME MEASURE: The planned major outcome was to determine the optimal MC placement for producing maximal expiratory pressure (MEP) and expiratory reserve volume (ERV) by FMS. These measurements were compared with the subjects' voluntary maximal efforts. A profile with varying stimulation intensities was also obtained in select individuals for determining the highest expiratory pressure. RESULTS: Stimulation at the T9 spinal level resulted in the highest mean MEP and ERV. Stimulation between T8 and L5 produced similar MEP and ERV as obtained from the T9 MC placement. The mean maximum MEP and ERV produced by FMS were 76.8 +/- 6.4 cm H2O (7.52 +/- 0.62 kPa) and 1.28 +/- 0.15 L, which were 67% and 79% of the subjects' voluntary maximal efforts, respectively. A stimulation intensity of 80% resulted in the highest expiratory pressure. CONCLUSION: FMS of lower thoracic and lumbar regions produced significant expiratory pressures and volumes. FMS of the expiratory muscles may prove to be a valuable technique for restoring cough in patients with spinal cord injury or other neurologic diseases, and in critical care or perioperative settings.
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Vibrio cholerae WO7 (serogroup O1) isolated from patients with diarrhea produces an extracellular toxin despite the absence of ctx, zot, and ace genes from its genome. The toxin elongates Chinese hamster ovary cells, produces fluid accumulation in ligated rabbit ileal loops, and agglutinates freshly isolated rabbit erythrocytes. Maximal production of this toxin (WO7 toxin) was seen in AKI medium with the pH adjusted to 8.5 at 37 degrees C under shaking conditions. We purified this toxin to homogeneity by sequential ammonium sulfate precipitation, affinity chromatography using a fetuin-Sepharose CL-4B column, and gel filtration chromatography, which increased the specific activity of the toxin by 1.6 x 10(6)-fold. The toxin is heat labile and sensitive to proteases and has a subunit structure consisting of two subunits with molecular masses of about 58 and 40 kDa as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Agglutination of GM1-coated sheep erythrocytes by toxin suggests that GM1 might be the physiologic receptor for WO7 toxin on the enterocytes. An immunodiffusion test between the antiserum raised against the purified WO7 toxin and the purified toxin gave a well-defined precipitation band. In the immunoblot assay, two bands were observed in the 58- and 40-kDa region. At the same time, antiserum against WO7 toxin failed to show any cross-reactivity with cholera toxin or Escherichia coli heat-labile toxin (LT1) in an immunodiffusion test or immunoblot assay. The enterotoxic activity of WO7 toxin could be inhibited by antiserum against purified WO7 toxin. Our results indicate that WO7 toxin is structurally and functionally distinct from other cholera toxins and that the enterotoxic activities expressed by WO7 toxin appear to contribute to the pathogenesis of disease associated with V. cholerae O1 strains.
OBJECTIVE: To compare early complication rates in unselected cases of coronary artery stenting in patients with stable v unstable angina. SETTING: Tertiary referral centre. PATIENTS: 390 patients with stable angina pectoris (SAP) and 306 with unstable angina (UAP). Patients treated for acute myocardial infarction (primary angioplasty) or cardiogenic shock were excluded. INTERVENTIONS: 268 coronary stents were attempted in 211 patients (30.3%). Stents used included AVE (63%), Freedom (14%), NIR (7%), Palmaz-Schatz (5%), JO (5%), and Multilink (4%). Intravascular ultrasound was not used in any of the cases. All stented patients were treated with ticlopidine and aspirin together with periprocedural unfractionated heparin. RESULTS: 123 stents were successfully deployed in 99 SAP patients v 132 stents in 103 UAP patients. Failed deployment occurred with nine stents in SAP patients, v four in UAP patients (NS). Stent thrombosis occurred in four SAP patients and 11 UAP patients. Multivariate analysis showed no relation between stent thrombosis and clinical presentation (SAP v UAP), age, sex, target vessel, stent length, or make of stent. Stent thrombosis was associated with small vessel size (p < 0.001) and bailout stenting (p = 0.01) compared with elective stenting and stenting for suboptimal PTCA, with strong trends toward smaller stent diameter (p = 0.052) and number of stents deployed (p = 0.06). Most stent thromboses occurred in vessels < 3 mm diameter. CONCLUSIONS: Coronary artery stenting in unstable angina is safe in vessels >/= 3 mm diameter, with comparable initial success and stent thrombosis rates to stenting in stable angina.
Respiratory physiological deadspace (VDphys) during normocapnic ventilation under anaesthesia was studied in 253 patients scheduled for elective non-thoracic surgery. Subjects were ventilated with SERVO 900B ventilator using CO2 analyser 930 (Siemens-Elema Sweden) to adjust minute volume sufficient to maintain end-tidal carbon dioxide fraction (FECO2) around 5.5kPa with normocapnic confirmation using arterial blood gas analysis. VDphys was calculated using Enghoff's modification of Bohr's equation. VDphys and deadspace to tidal volume ratios (VD/VT) in male patients were 142.6 +/- 28.4 ml and 0.37 +/- 0.068 respectively and were significantly higher than that in females (119.4 +/- 35.6 ml and 0.36 +/- 0.067). Males had significantly higher VDphys/mass (2.5 +/- 0.68 ml.kg) compared with females (2.2 +/- 0.54 ml/kg, P < 0.001) but significantly lower body mass index (BMI) (20.67 +/- 3.2 in males and 22.47 +/- 4.1 in females, P < 0.001). VDphys showed positive correlation with weight, height and body surface area (BSA) but VDphys/kg showed negative correlation with BMI. Multiple regression analysis produced a best fit equation for VDphys = 9.7 + 64.3 x BSA + 13.51S where S = 1 for females and 2 for males.
BACKGROUND: Congenital kyphosis and kyphoscoliosis are much less common than congenital scoliosis. However, they are potentially more serious because compression of the spinal cord and paraplegia sometimes develop. The goals of the present study were to document the natural history of congenital kyphosis and kyphoscoliosis and to determine the stage at which the natural progression should be interrupted by treatment. METHODS: We reviewed the medical records and radiographs of the spine of 112 consecutive patients. Sixty-eight patients had a type-I kyphosis due to an anterior failure of vertebral-body formation, twenty-four had a type-II kyphosis due to an anterior failure of vertebral-body segmentation, and twelve had a type-III kyphosis due to a combination of anomalies; the deformities of the remaining eight patients could not be classified. Eighty-five skeletally immature, untreated patients were first evaluated at a mean age of six years and nine months (range, two months to sixteen years and three months), and twenty-seven patients were skeletally mature at the time of the first visit. Sixty-three of the eighty-five skeletally immature patients were observed without any treatment for a mean period of six years and six months (range, one to sixteen years) before skeletal maturity, and the remaining twenty-two patients had a posterior arthrodesis of the spine soon after the initial visit. At skeletal maturity, forty-one patients had not been treated and sixty-eight had had an arthrodesis of the spine. The remaining three patients had not yet reached skeletal maturity at the time of the most recent follow-up. RESULTS: The apex of the kyphosis was seen at all levels but was most frequent between the tenth thoracic and the first lumbar level (seventy-four patients; 66 percent). There was no relationship between the severity of the kyphosis and its location in the spine. Progression of the curve was most rapid during the adolescent growth spurt and stopped only at skeletal maturity. Progression was most rapid and the magnitude of the curve was the greatest in type-III kyphosis (twelve patients) followed by type-I kyphosis due to a posterolateral quadrant vertebra (thirty-nine patients), a posterior hemivertebra (eight patients), a butterfly vertebra (fifteen patients), and a wedged vertebra (six patients). A kyphosis due to two adjacent type-I vertebral anomalies progressed more rapidly and produced a more severe deformity than did a similar single anomaly. The prognosis for type-II kyphosis was variable and was much more severe when an anterolateral unsegmented bar had produced a kyphoscoliosis (nine patients) than it was when a midline anterior bar had produced a pure kyphosis (fifteen patients), which usually progressed slowly. Spontaneous neurological deterioration due to compression of the spinal cord occurred in ten patients (seven of whom had a type-I kyphosis and three of whom had an unclassifiable anomaly) at a mean age of thirteen years and eight months, and one other patient (with an unclassifiable anomaly) had spastic paraparesis at the age of twenty-eight years. CONCLUSIONS: Congenital kyphosis and kyphoscoliosis are uncommon deformities with the potential to progress rapidly, resulting in severe deformity and possible neurological deficits. A thorough knowledge of the natural history is essential in the planning of appropriate and timely treatment to prevent progression of the deformity and neurological complications.
This paper endeavours to identify the background characteristics of health centre users in Trinidad and Tobago and their perceptions of the efficiency of the services provided. Multistage sampling was employed to select 1451 users. Data were obtained during structured interviews on regular clinic days. Of the people using the health centres, 80.4% were unemployed and 75.9% were women. People aged over 60 accounted for 25.4% of the sample. Users included a disproportionately high number of persons from the lower socioeconomic categories. The proportions of persons of different ethnic and religious groups closely reflected those in the country's general population. Approximately 74% of the interviewees were satisfied with the performance of the doctors in the health centres. For nurses the satisfaction rating was about 10% higher. The greatest needs for improvement were perceived to be in pharmacists' and doctors' services, with particular reference to waiting times.
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