Sedation in neurological intensive care unit

Analgesia and sedation has been widely used in intensive care units where iatrogenic discomfort often complicates patient management. In neurological patients maximal comfort without diminishing patient responsiveness is desirable. In these patients successful management of sedation and analgesia incorporates a patient based approach that includes detection and management of predisposing and causative factors, including delirium, monitoring using sedation scales, proper medication selection, emphasis on analgesia based drugs and incorporation of protocols or algorithms. So, to optimize care clinician should be familiar with the pharmacokinetic and pharmacodynamic variables that can affect the safety and efficacy of analgesics and sedatives.

Isaac's syndrome associated with myasthenia gravis and thymoma

A 65-year-old male developed fatigable weakness of ocular and bulbar muscle and positive anti-acetyl cholinesterase antibodies suggesting the diagnosis of myasthenia gravis. His condition responded to anticholinesterase and immunotherapy. However, 18 months later, he developed painful paresthesiae, muscle cramps with hyperhiderosis, and was diagnosed as having Isaac's syndrome (neuromyotonia, continuous muscle fibre activity). Computed tomography of the chest revealed a thymic mass, which was confirmed after surgery and histopathology as thymic cell carcinoma. The co-occurrence of myasthenia gravis and continuous muscle fiber activity should prompt the consideration of the occurrence of these disorders as one of the paraneoplastic manifestations, most often due to a thymic neoplasm. Both these conditions respond to treatment of underlying thymoma. This case is a very rare presentation worth reporting.

Acute renal failure caused by pheniramine maleate induced rhabdomyolysis: an unusual case

Antihistamines are easily available over-the-counter medications, which are frequently involved in overdoses. The usual course is accompanied by the anticholinergic effects of these agents. We report a case of a suicide attempt in a young male, where ingestion of antihistamine pheniramine maleate was complicated by nontraumatic rhabdomyolysis and oliguric acute renal failure. Rhabdomyolysis and acute renal failure is a rarely reported but potentially serious complication among patients who present to the emergency after intentional overdoses making recognition and prompt intervention essential. We also describe the potential mechanism of muscle injury in antihistamine overdose.

Organelle-specific injury to melanin-containing cells in human skin by pulsed laser irradiation

Physical models predict that ultraviolet laser radiation of appropriately brief pulses can selectively alter melanin-containing cellular targets in human skin. We exposed skin of normal human volunteers to brief (20 nanosecond) 351-nm wave length pulses from a XeF excimer laser, predicting that those cells containing the greatest quantities of melanized melanosomes (lower half of the epidermis) would be selectively damaged. Transmission electron microscopy revealed the earliest cellular alteration to be immediate disruption of melanosomes, both within melanocytes and basal keratinocytes. This disruption was dose dependent and culminated in striking degenerative changes in these cells. Superficial keratinocytes and Langerhans cells were not affected. We conclude that the XeF excimer laser is capable of organelle-specific injury to melanosomes. These findings may have important clinical implications in the treatment of both benign and malignant pigmented lesions by laser radiations of defined wave lengths and pulse durations.

The effect of temperature and other factors on selective microvascular damage caused by pulsed dye laser

Brief pulses of 577-nm radiation have recently been shown to selectively damage superficial cutaneous blood vessels, resulting clinically in purpura. There was a sharp threshold of exposure dose necessary for causing purpura in any given subject, which correlated with histologic evidence of extravasation and specific vascular injury. As a means of studying mechanisms for such damage, heat, cold, pressure, suction, UV radiation, and intradermal epinephrine were used to alter human cutaneous microvasculature prior to and during 577-nm pulsed dye laser exposures. When compared with control sites, only cooling of the skin significantly affected the exposure dose needed to cause purpura. The magnitude of this effect is quantitatively most consistent with intravascular microvaporization as the cause of vessel rupture and hence purpura.

Effect of repeated oral administration of quinalphos on blood esterases in Bubalus bubalis

The effect of quinalphos on blood esterases was investigated in male buffalo calves after daily oral doses of 0.7, 1.4 and 2.1 mg/kg body weight for 28 consecutive days. Quinalphos markedly inactivated serum carboxylesterase (69-90%) and plasma cholinesterase activity (75-88%). Esterase activities in animals receiving 0.7 mg/kg/day of quinalphos approached normal levels 14 days after the termination of its ingestion. The results suggest that quinalphos is an effective inhibitor of blood esterases in vivo and its repeated exposure to buffaloes may impair detoxification of organophosphorus insecticides that are mainly biodegraded by carboxylesterase enzyme.

Treatment of pityriasis rosea with UV radiation

Twenty patients with symptomatic and extensive pityriasis rosea were treated with unilateral UV-B phototherapy in a bilateral comparison study. Five consecutive daily erythemogenic exposures resulted in substantially decreased pruritus and extent of disease greater than that on the untreated side in approximately 50% of the patients. Therapy seems to be most beneficial to patients receiving treatment within the first week of the eruption.

Effect of chloramphenicol pretreatment on malathion-induced acute toxicity in the rat

Pretreatment of rats with chloramphenicol (CAP) (100 mg/kg, ip) 30 min prior to a single oral LD50 dose of malathion (MTH) at 340 mg/kg completely protected against MTH-induced signs of cholinergic toxicity. Pretreatment with CAP also decreased the extent and duration of MTH-induced inhibition of cholinesterase (ChE). It was previously established that CAP inhibits (1) the cytochrome-P-450-catalyzed oxidative desulfuration of methylparathion to the much more toxic oxygen analog methylparaoxon (MOX) and (2) the carboxyesterase in rat liver. Since carboxyesterases account for 60% or more of the catabolism of MTH in the rat, the present results were surprising. Thus it appears that the inhibition of MTH toxicity by CAP pretreatment is attributable to inhibition by CAP of the metabolic activation of MTH to MOX.

Pharmacokinetics and plasma protein binding (in vitro) of oxytetracycline in buffalo (Bubalus bubalis)

The pharmacokinetics of oxytetracycline given in a single dose (22 mg/kg) either IV or IM was studied in 4 female buffalo calves. The half-life (t1/2) after IV administration varied between 169.02 and 216.56 minutes and that after IM administration, between 630 and 990 minutes. The drug was distributed well in the body after IM administration (Vdarea 1.18 to 2.15 L/kg). The total body clearances varied between 1.02 and 1.45 and between 1.17 and 1.49 ml/kg/min after the IV and the Im dosings, respectively. It has been proposed that oxytetracycline is excreted mainly by glomerular filtration in the buffalo species, but tubular reabsorption also may have a small part. About 42% of the drug was bound to plasma proteins at concentrations of 2 to 20 micrograms of oxytetracycline/ml. The drug dosage schedules to maintain serum levels of 0.5, 1, 2, and 5 micrograms/ml also are determined.

Low-intensity selective UV phototherapy. A clinical trial in outpatient therapy for psoriasis

A UV source of low-intensity output with peak effective emission in the 300 to 320-nm range, termed low-intensity selective UV phototherapy (LISUP), is being advocated for home phototherapy for psoriasis. Twenty patients with plaque-type psoriasis were treated three times a week as outpatients with this unit; the results were compared with those found in a similar group of 20 outpatients treated previously three times a week with a proved and effective protocol using erythemogenic exposures to a conventional UV-B source. Emollients were the only topical agents used during therapy. Eight patients had clearing and five others showed improvement with LISUP. Eighteen patients had clearing and one showed improvement with the UV-B protocol. We found LISUP less frequently effective when used three times a week in clearing plaque-type psoriasis. Therefore, we recommend a trial of this unit before purchase by the patient.

Combined methotrexate--ultraviolet B therapy in the treatment of psoriasis

Twenty-six patients with extensive psoriasis were treated with a 3-week course of methotrexate followed by a combination of ultraviolet B (UVB) therapy and methotrexate. A plaque of psoriasis was shielded during UV therapy to serve as a control. When lesions cleared to less than 5% of body involvement, the methotrexate was stopped and UVB therapy alone was used as maintenance therapy. This protocol achieved clearance of disease in all twenty-six patients in a mean of 7 (+/- 1.5) weeks, with twelve (+/- 4.0) exposures to UVB therapy and a final UVB radiation dose at clearance of 320 (+/- 157) mjoules/cm2. The mean total dose of methotrexate was 112 mg (range, 75 mg-165 mg). At the time of clearing, the shielded area had a decrease in sealing and thickness in twenty-two patients but was free of psoriasis in only four patients. In a preliminary study we were unable to reproduce a methotrexate recall of UV-induced erythema. The combination therapy of methotrexate and UVB allows for clearing of psoriasis at relatively low doses of UVB and methotrexate, and thus may reduce the long-term cumulative toxicity of both agents.

The interaction of UVA and UVB in the production of threshold erythema

A study was done to demonstrate quantitatively and graphically the way in which suberythemogenic doses of broadband UVA and UVB interact in producing a visible erythema. On the backs of fair-skinned human volunteers the minimal erythema dose (MED) was determined for polychromatic UVA and UVB. Increasing fractions of the UVA MED were given to sites already exposed to various fractions of the UVB MED resulting in sites exposed to various doses of both UVA and UVB. The same experiment was repeated with the order of wavebands reversed. It was demonstrated that when UVA was followed by UVB an erythema was produced in those sites where the sum of the fractions was equal to one, an interaction termed photoaddition. When the UVA exposure followed the UVB, erythema was again predominantly noted in those sites demonstrating photoaddition. However, in the latter case, numerous sites of threshold erythema were noted where the sum of the fractions was greater than one. This is suggestive of photorecovery. No evidence of photoaugmentation was observed with either order of exposure.

A study on renal function in the Indian buffalo (Bubalus bubalis)

Glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) in buffalo species (Bubalus bubalis) were estimated using a single injection technique. The total body clearances of inulin and para-aminohippuric acid (PAH) served as estimates of GFR and ERPF, respectively. Inulin and PAH were administered to animals as a single i.v. bolus. The time-concentration curves were determined for each compound. Three mathematical models were applied to the data. The two compartment model gave the best fit to the data. The single compartment model gave slightly higher values, but could be used in clinical and certain research situations to estimate renal functions when it is not practical to take large number of samples.

Biological fate of 32P malathion in Gallus domesticus (desi poultry birds)

During this study, a minor surgical technique was developed for the separation of urine and faeces in birds and fate of 32P malathion was studied, following a single oral dose of 394 mg/kg. The birds showed characteristic signs and symptoms of organophosphorus poisoning and the results suggested that the compound is rapidly absorbed from the gastro-intestinal tract, significant quantities being detected in plasma after 0.5 h of ingestion. Highest concentration of 32P was present during 6 to 8 h of administration. At 6 h, 32P was highest in liver followed by other organs. With the lapse of time the concentration of 32P in various organs decreased at 48 h, it was not detected except in liver, kidney, lung and spleen when only traces were observed. The cumulative urinary and faecal excretion study revealed that within 24 h 90% is rapidly excreted mainly via the urine and only small amounts in the faeces. Metabolism studies showed that the compound is quickly metabolised. Because of the rapid turnover of the compound, this study indicated that the accumulation of this compound is unlikely in the body system.