Constant rate infusion of tramadol in isoflurane-anesthetized pigs undergoing experimental surgery.

The purpose of this study was to investigate the effect of tramadol (TM) (2 mg/kg) administered intramuscularly (IM) followed by a constant rate infusion (CRI) of TM (2 mg/kg/h) in pigs. Sixteen pigs undergoing experimental surgery were premedicated IM with a combination of alfaxalone (5 mg/kg) and midazolam (0.5 mg/kg). Anaesthesia was induced with propofol (2 mg/kg) intravenously (IV) and maintained with isoflurane. Pigs were randomly assigned to one of the two following groups: Group 1 (n=8): received a loading dose of TM (2 mg/kg) followed by a CRI of TM (2 mg/kg/h); Group 2 (n=8): a loading dose of TM (2 mg/kg) followed by a CRI of lactated Ringer's solution (2 ml/kg/h). Heart rate (HR), respiratory rate (RR), rectal temperature (RT), haemoglobin oxygen saturation (SpO2), fraction of inspired oxygen (FIO2), end-tidal concentration of isoflurane (FEISO), end-tidal carbon dioxide concentration (FECO2), pH, arterial oxygen partial pressure (PaO2), arterial carbon dioxide partial pressure (PaCO2) and bicarbonate concentration (HCO3-) were recorded immediately after loss of righting reflex (T=0 min) and at 15-min intervals over a period of 60 min. Continuous data were analysed using a repeated- -measure analysis of variance (ANOVA) and a p-value ⟨0.05 was considered significant. HR, RR and FEISO were significantly lower (p⟨0.05) in Group 1 at T30 and T45, which corresponded to the time of the most intense surgical stimulation. The results suggest that the TM infusion minimizes the HR and RR response, slightly reducing isoflurane requirements and determining a superior perioperative analgesia.

Pharmacokinetics of tramadol and its major metabolite after intramuscular administration in piglets.

Tramadol (T) is a centrally acting atypical opioid used for treatment of dogs. Piglets might experience pain following castration, tooth clipping and tail docking and experimental procedures. The aim of this study was to assess the pharmacokinetics of T and its active metabolite M1 in male piglets after a single intramuscular injection. Six healthy male piglets were administered T (5 mg/kg) intramuscularly. Blood was sampled at scheduled time intervals and drug plasma concentrations evaluated by a validated HPLC method. T plasma concentration was quantitatively detectable from 0.083 to 8 h. M1 was quantified over a shorter time period (0.083-6 h) with a Tmax at 0.821 h. The study demonstrated that piglets produce a larger amount of M1 compared with dogs, horses and goats. The human minimum effective concentration of M1 (40 ng/mL) was exceeded for over 3 h in piglets. If it is assumed to also apply to piglets, it could be speculated that the drug efficacy might exert its action over 3 h or longer. This assumption has to be confirmed by further specific pharmacokinetic/pharmacodynamic studies.

Methods for detecting early signs of AIDS dementia complex in asymptomatic HIV-1-infected subjects.

OBJECTIVES: To determine the optimal diagnostic procedures for identifying early signs of AIDS dementia complex (ADC) in asymptomatic HIV-1-infected individuals, in order to prevent further cognitive function impairment by early treatment. DESIGN: Study patients had been referred electively and consecutively to hospital; all had been referred for the first time and gave informed consent. Inclusion criteria were (1) lack of history and/or symptoms of psychosis and neurological disorders; (2) lack of active viral, protozoan or fungal pathology; (3) abstinence from heroin and/or cocaine for at least 6 months before baseline evaluation. SETTINGS: Subjects were seen at the L. Spallanzani Hospital for Infectious Diseases, Rome, Italy between March 1989 and March 1991. PARTICIPANTS: Eighty-two asymptomatic HIV-1-infected subjects: 41 drug users, 27 homosexuals and 14 heterosexuals. MAIN OUTCOME MEASURES: All subjects were evaluated using Wechsler-Bellevue I, Benton C form and Bender tests. Thirty-nine subjects underwent single-photon emission computed tomography (SPECT) and 12 magnetic resonance imaging (MRI). The immunological status of each subject was determined. RESULTS: On psychometric testing, 23 out of the 82 (28%) asymptomatic subjects had a mental decay percentage (MD%) > or = 20%. Cerebral perfusion abnormalities were detected in 31 out of 39 (79.48%) subjects who underwent SPECT; MRI abnormalities were observed in seven out of 12 (58%) subjects. Twelve out of 23 subjects with MD% > or = 20, 15 out of 29 subjects with SPECT abnormalities and four out of seven patients with MRI abnormalities had total CD4+ lymphocyte counts > or = 500 x 10(6)/l. CONCLUSIONS: The high incidence of abnormal SPECT and of MD% > or = 20 in asymptomatic HIV-1-infected patients, and the lack of correlation between immunological status and degree of mental decay, SPECT and MRI abnormalities raise many questions about subclinical HIV-1 neurological disease.