Uttam Garg

Measurement of urinary concentration : a critical appraisal of methodologies

Abstract The measurement of urine concentration provides information concerning the kidney’s ability to appropriately respond to variations in fluid homeostasis. It also assists in the interpretation of other tests performed on the same urine specimen. The gold standard of estimating urinary concentration is the measurement of its osmolality; however, this procedure is not readily available to the practicing physician. Therefore, urine concentration is usually determined by measurement of its specific gravity (SG), which provides a fair estimate of urine osmolality. Over the years numerous tests have been developed to measure urine SG in a simple, quick, reliable and easily available method. These tests measure SG either directly (e.g., gravimetry) or by indirect methods (e.g., refractometry and reagent strip). All these tests have certain limitations based on their underlying physical principles. Specific gravity as measured by refractometry is influenced by proteinuria, such that for each 10 g/l protein the SG increases by 0.003. SG is also influenced by glucosuria such that it increases by approximately 0.002 per 10 g/l glucose when compared with urinary osmolality. Unlike osmolality, which is only affected by the number of particles, refractometry is affected by number, mass and chemical structure of the dissolved particles; hence large molecules like radiographic contrast or mannitol will increase SG relative to osmolality. The reagent strip is minimally affected by glucose, mannitol or radiographic contrast. However, it is affected by urinary pH such that only urine in the pH range of 7.0–7.5 can be correctly interpreted. The measurement of SG by reagent strip is based on the ionic strength of the urine and thus is significantly affected by the ionic composition of the urine and by proteins which have an electric charge in solution. In our experience, SG measured by the refractometer is consistently more accurate than the reagent strip. For the clinician who is interpreting urine SG results, it is important to be aware of these limitations and understand the reasons for possible potential errors of each particular method.

A fatality involving an unusual route of fentanyl delivery: Chewing and aspirating the transdermal patch

We recently encountered a subject who died from an uncommon misuse of a fentanyl transdermal patch, chewing, followed by complications of aspiration of the patch. We report this case to alert medical examiners to the troubling trend of increased fentanyl patch abuse and its expanding range of misuses and associated morbidities. The decedent was a 28-year-old white male with a past medical history of prescription drug abuse who was pronounced dead in the emergency department shortly after arrival. An autopsy was completed and a tough but stretchy beige foreign body was identified lodged in a mainstem bronchus. Toxicological analysis of femoral blood showed methamphetamine, fentanyl and norfentanyl concentrations of 1456, 8.6 and 1.4 ng/mL, respectively. Individuals who abuse prescription medications often modify the route of administration of the drug from the intended method. As this case demonstrates, this choice can be fatal. The novel findings include a chewed patch, aspiration of a drug patch, and combination with an illicit drug at potentially lethal blood levels for both methamphetamine and fentanyl in a novice user.

Analysis of U-47700, a Novel Synthetic Opioid, in Human Urine by LC–MS–MS and LC–QToF

The illicit drug market has rapidly evolved from synthetic cannabinoids to cathinone derivatives and now a new emerging threat of synthetic opioids. These compounds were mostly developed by pharmaceutical companies during drug discovery. The new psychoactive substances are not routinely covered in drug screening and may go undetected. Recently fentanyl analogous, AH-7921, MT-45 and now U-47700 have been encountered in clinical and forensic casework. U-47700 is gaining popularity on drug user forms as a legal alternative to heroin. It is a µ-receptor agonist that is part of the trans-1-2-diamine opioid analgesic drug class developed by The Upjohn Company in an attempt to develop a non-addicting analgesic. A LC-MS-MS method was developed and validated to detect and quantify U-47700. Additional analysis was conducted with an LC-QToF to identify the presence of the parent drug and metabolites. A total of four cases have been evaluated by the LC-MS-MS methodology which has an analytical range of 1-1,250 ng/mL and limit of detection of 1 ng/mL. The concentration of U-47700 in urine specimens ranged from below the limit of quantification to 224 ng/mL. The ToF analysis detected the presence of suspected phase I demethylated metabolites that may assist future analysis of this compound. The prevalence of designer opioids in casework highlights the importance of analysis for new psychoactive substances. Traditional opiates/opioids were not detected in the presented cases, but the available case histories revealed an opioid toxidrome. These findings suggest that U-47700 drug may cause significant morbidity and mortality within the United States as an emerging drug threat.

Hyperoxia and tidal volume: Independent and combined effects on neonatal pulmonary inflammation.

Background: Hyperoxia and tidal volume mechanical ventilation are independent factors in the genesis of lung injury, but it remains unclear the extent to which each is responsible or contributes to this process in newborns. Objectives: To study the independent and combined effects of hyperoxia and tidal volume mechanical ventilation on the induction of lung inflammation in a newborn piglet model of ventilator-induced lung injury. Methods: Following exposure to either ambient air or FIO2 = 1.0 for a period of 3 days, newborn piglets were randomized to receive mechanical ventilation with either high tidal volume (20 ml/kg) or low tidal volume (6 ml/kg) for 4 h while controlling for pH. Results: Monocyte chemoattractant protein-1 level in the lungs of animals randomized to hyperoxia with high tidal volume ventilation was significantly elevated, compared to all other groups (p < 0.05). Myeloperoxidase assayed in lung homogenate was found to be significantly higher in nonventilated animals exposed to hyperoxia (p < 0.01). Only in animals previously exposed to hyperoxia did the addition of high tidal volume ventilation further increase the level of myeloperoxidase present (p < 0.05). Pulmonary vascular resistance was significantly elevated after 4 h of mechanical ventilation compared to 1 h (p < 0.001). Conclusions: We conclude that in neonatal piglets undergoing hyperoxic stress, superimposition of high tidal volume ventilation exacerbates the lung inflammation as assessed by lung monocyte chemoattractant protein-1 and level of myeloperoxidase.

Fatality Involving Complications of Bupivacaine Toxicity and Hypersensitivity Reaction

Abstract:  This case represents unusual findings of elevated bupivacaine and tryptase concentrations following local anesthetic, bupivacaine, administered as a scalene nerve block for elective rotator cuff repair surgery. Following bupivacaine injection, the patient exhibited almost immediate seizure activity, bradycardia, and cardiac arrest. Resuscitative efforts including cardiopulmonary bypass restored a cardiac rhythm. However, the clinical medical status of the patient progressively declined and he died 7 h following administration of the local anesthetic. Autopsy revealed several abnormalities of the heart including cardiomegaly, myocardial bridging, and lipomatous hypertrophy of the intraatrial septum, which may have contributed to bradycardia and arrhythmia. Postmortem toxicology results revealed elevated bupivacaine and tryptase concentrations. Elevated postmortem bupivacaine concentrations 7 h following administration and abrupt onset of seizures indicate unintentional intravascular injection instead of nerve and tissue infiltration. An elevated postmortem tryptase concentration points to the possibility of a hypersensitivity reaction to bupivacaine.

Follicle stimulating and leutinizing hormones, estradiol and testosterone in Prader–Willi syndrome†

Prader–Willi syndrome (PWS) is a classic genomic imprinting disorder in which affected individuals display hypotonia, failure to thrive, feeding difficulties, developmental delays and hypogenitalism/ hypogonadism in infancy.At approximately2–3years of age, hyperphagia, central obesity, short stature, small hands and feet, behavioral problems and characteristic facial features are present [Cassidy, 1984; Butler, 1990; Bittel and Butler, 2005; Butler et al., 2006]. The genetic causes are generally due to a paternal deletion of the chromosome 15q11–q13 region (about 70%), maternal disomy 15 (UPD) (about 25%), or imprinting defects or translocations involving chromosome 15 (about 5%) [Bittel and Butler, 2005]. The characteristic findings of hyperphagia, central obesity, short stature, cryptorchidism and hypogonadism are consistent with endocrine and/or metabolic abnormalities involving the hypothalamic–pituitary axis. While some studies have examined specific hormonal levels in Prader–Willi syndrome [Nagai et al., 1998; Burman et al., 2001; Eiholzer and Lee, 2006; Eiholzer et al., 2006; Butler et al., 2007], a comprehensive examination of follicle stimulating hormone (FSH), leutinizing hormone (LH), estradiol and testosterone levels is lacking in individuals with Prader–Willi syndrome with known genetic subtypes. Thus, we report FSH, LH, estradiol and testosterone levels in a relatively large cohort of males and females (16 years of age and older) with Prader–Willi syndrome as a function of genetic subtype and obesity status. The regulation of FSH and LH secretion and subsequent estradiol (female) and testosterone (male) secretion is highly integrated involving multiple signaling pathways, receptor systems and signaling molecules such as inhibin and ghrelin [Ojeda et al., 2006]. In females, FSH levels vary throughout the menstrual cycle peaking at mid-cycle while LH levels peak prior to ovulation. Both FSH and LH levels increase dramatically after menopause. Hypothalamic hypogonadism subjects are characterized by lowFSH, LHand sexhormone levelswhile normal or elevated FSH levels indicate a gonadal origin. Elevated LH levels are seen in females with ovarian failure while low levels are seen in pituitary failure. Inmales, there is a prominent neonatal surge of LH, FSH and testosterone that begins shortly after birth and peaks at 6–8 weeks of age before gradually waning over 4–6 months [Veldhuis et al., 2006]. This early rise in FSH and LH is not observed in females. At 10 years of age for females and at 11 years of age in males, adrenarche usually occurs as defined by the appearance of pubic and axillary hair and increased apocrine sweat gland activity. This event is triggered by increased adrenal productionof dehydroepiandrosterone, dehydroepiandrosterone sulfate and androstenedione but not cortisol [Veldhuis et al., 2006]. However, maturation of the testes and ovaries (gonadarche) requires the orderly activation of the hypothalamic–pituitary–gonadal axis. The initiation of this process remains poorly defined but involves increased pulsatile secretion of gonadotropin releasing hormone (GnRH) that subsequently controls FSH and LH secretion from the anterior pituitary [Veldhuis et al., 2006]. This orderly

Sevoflurane Concentrations in Blood, Brain, and Lung After Sevoflurane‐Induced Death

Abstract:  Sevoflurane concentrations in blood, brain, and lung were measured in an individual apparently dying from sevoflurane inhalation. Sevoflurane is a volatile nonflammable fluorinated methyl isopropyl ether inhaled anesthetic, chemically related to desflurane and isoflurane. The incidence of abuse of sevoflurane is lower than that of other drugs of abuse possibly due to its inaccessibility to the general public and less pleasurable and addicting effects. The dead subject was an anesthetist found prone in bed holding an empty bottle of sevoflurane (Ultane®). Serum, urine, and liver were screened for numerous drugs and metabolites using enzyme immunoassays and gas chromatography‐mass spectrometry. Analysis did not reveal presence of any drug, including ethanol, other than sevoflurane. Sevoflurane was determined by headspace gas chromatography and revealed concentrations of 15 μg/mL in blood and 130 mg/kg in brain and lung. Autopsy revealed pulmonary edema and frothing in the lung, pathological findings associated with death by sevoflurane or hypoxia. The cause of death was ruled as sevoflurane toxicity and the manner of death as accident.

Sieving coefficient inaccuracies during hemodiafiltration in patients with hyperbilirubinemia

Abstract Hemodiafiltration has assumed an important role in the supportive therapy of critically ill patients. The viability of the filter used for hemodiafiltration can be monitored by estimating the sieving coefficient of small molecules such as creatinine and/or urea. We report on three patients with severe hyperbilirubinemia whose creatinine sieving coefficient was spuriously elevated as a result of discordance in the accuracy of creatinine measurement in plasma and ultrafiltrate respectively. This discordance was a consequence of lack of bilirubin clearance during hemodiafiltration. As a result, while the plasma creatinine determination by the kinetic Jaffe method was negatively influenced by the hyperbilirubinemia, the ultrafiltrate creatinine was not. This report is the first to document the lack of bilirubin clearance during hemodiafiltration and its impact on the calculation of sieving coefficient based on creatinine. The use of urea as the solute for determining the sieving coefficient allows for an accurate estimate and provides a valid means of monitoring this parameter in the setting of hyperbilirubinemia.

Endogenous Production of Nitric Oxide in Endotoxemic Piglets

We sought to assess the relation between endotoxin-induced pulmonary hypertension and the production of nitrix oxide (NO) in neonatal animals. Adult animals respond to endotoxin by increasing exhaled NO and plasma NO metabolites. The response of neonatal animals has not previously been reported. We administered 20 µg/kg of Escherichia coli lipopolysaccharide (LPS) to 12- to 18-day-old and to 5- to 7-week-old piglets. Pulmonary vascular resistance increased significantly in both age groups. Exhaled NO in the 12- to 18-day-old animals and in the 5- to 7-week-old piglets did not increase significantly. A similarly treated group of adult rats did show a significant increase in exhaled NO (2.6 ± 1.0 to 109.5 ± 54.3 ppb; p = 0.028). Plasma NO metabolite measurements followed the same pattern of no increase in both porcine groups, and a large increase in the rat group. However, immunostaining of lungs from 12- to 18-day-old piglets did reveal an increase in inducible NO synthase. These results suggest that piglets demonstrate a limited ability to modulate LPS-induced pulmonary hypertension by elevations in exhaled NO. They also demonstrate the differential response to LPS between species.

Intravenous busulfan dose individualization - impact of modeling approach on dose recommendation.

TDM is intended to limit unintended consequences of drugs with narrow therapeutic indices. However, the application of different sampling strategies and pharmacokinetic approaches results in different dosing recommendations and ostensibly different outcomes. TDM approaches for intravenous busulfan dose individualization employ compartmental or non‐compartmental modeling with anywhere from three to seven drug levels. This investigation was designed to examine the differences in dosing recommendations that arise in children (n = 30) when five different TDM approaches were employed. Significant differences in recommended doses between modeling strategies were observed. More importantly, the recommendations were discordant in 13 cases with at least one model recommending a dose adjustment in the opposite direction relative to the remaining models. The mathematical differences introduced by the application of different TDM approaches are not purely academic. Unification of busulfan TDM approaches should be considered to mitigate inconsistently applied dose adjustment, and facilitate comparisons of outcome, between clinical centers.