Temperature-dependent pharmacokinetics and pharmacodynamics of vecuronium

BACKGROUND: The authors evaluated the influence of temperature on the pharmacokinetics and pharmacodynamics of vecuronium because mild core hypothermia doubles its duration of action. METHODS: Anesthesia was induced with alfentanil and propofol and maintained with nitrous oxide and isoflurane in 12 healthy volunteers. Train-of-four stimuli were applied to the ulnar nerve, and the mechanical response of the adductor pollicis was measured. Volunteers were actively cooled or warmed until their distal esophageal temperatures were in one of four ranges: < 35.0 degrees C, 35.0-35.9 degrees C, 36.0-36.9 degrees C, and > or = 37.0 degrees C. With temperature stabilized, vecuronium was infused at 5 microg x kg(-1) x min(-1) until the first response of each train-of-four had decreased by 70%. Arterial blood (for vecuronium analysis) was sampled at intervals until the first response recovered to at least 90% of its prevecuronium level. Vecuronium, 20 microg x kg(-1) x min(-1), was then infused for 10 min, and arterial blood was sampled at intervals for up to 7 h. Population-based nonlinear mixed-effects modeling was used to examine the effect of physical characteristics and core temperature on vecuronium pharmacokinetics and pharmacodynamics. RESULTS: Decreasing core temperature over 38.0-34.0 degrees C decreases the plasma clearance of vecuronium (11.3% per degrees C), decreases the rate constant for drug equilibration between plasma and effect site (0.023 min(-1) per degrees C), and increases the slope of the concentration-response relationship (0.43 per degrees C). CONCLUSIONS: Our results show that reduced clearance and rate of effect site equilibration explain the increased duration of action of vecuronium with reducing core temperature. Tissue sensitivity to vecuronium is not influenced by core temperature.     

Peritubular capillary basement membrane changes in chronic renal allograft rejection: Comparison of light microscopic and ultrastructural observations

Marked peritubular capillary basement membrane (PTCBM) multilayering, the ultrastructural feature of chronic antibody-mediated rejection (ABMR) of kidney allografts, was found to correspond histologically to PTCs with thickened BMs; such PTCs have been suggested as a novel histological marker of chronic rejection. We investigated whether scoring of PTCBM thickening can substitute the ultrastructural search for PTCBM multilayering. The thickening was graded in PAS- and Jones-stained sections in 110 biopsies from recipients with a late dysfunction, all examined ultrastructurally for transplant capillaropathy (≥3 PTCs with ≥5 BM layers). Grade 0 indicated no thickening. Grade 1 and grade 2 were assigned when the PTCBMs were as thick as or thicker than those of the non-atrophic tubules, and duplication/chain-like lamination of the PTCBM was noted in ≤3 or ≥4 high-power fields, respectively. The series was enrolled in subgroups of those with and those without histopathological lesions of chronic rejection. Fifty-six biopsies displayed lesions of chronic ABMR. Transplant capillaropathy was demonstrated in 40 biopsies. Grade 2 thickening furnished a substantial interobserver concordance rate (κ = 0.803) and correlated with the transplant capillaropathy. Jones staining performed somewhat better in scoring than PAS staining. Grade 2 thickening was verified in 35 biopsies involving chronic ABMR, and in one control biopsy (sensitivity 61.4%, specificity 0.98). Grade 1 thickening was not suggestive of chronic ABMR at all. In conclusion, grade 2 thickening can be regarded as the histopathological lesion of chronic ABMR; however, electron microscopy remains the gold standard in the assessment of PTCBM changes.     

Steroid withdrawal at 3 months after kidney transplantation: a comparison of two tacrolimus-based regimens

The 6 month prospective, randomized study compared the steroid-sparing potential of two tacrolimus-based regimens after renal transplantation. A total of 489 patients were randomized (1:1) to receive tacrolimus/mycophenolate mofetil (MMF)/steroids (n = 243; group Tac/MMF/S) or tacrolimus/azathioprine/steroids (n = 246; group Tac/Aza/S). At 3 months, steroids were tapered off in 267 (54.6%) patients free from steroid-resistant acute rejection and with serum creatinine concentrations <160 micromol/l. The incidence of biopsy-confirmed acute rejection at month 3 was lower in group Tac/MMF/S compared with group Tac/Aza/S (18.1% vs. 26.0%,P = 0.035). Moreover, more patients in the Tac/MMF/S group met the criteria for steroid withdrawal than in the Tac/Aza/S group (60.5% vs. 48.8%; P < 0.01). The incidence of acute rejection during months 4-6 was low in all groups, both for patients on steroid-free dual therapy (Tac/MMF: 2.7%, Tac/Aza: 0.8%) and for patients who continued steroid maintenance therapy (Tac/MMF/S: 3.5%, Tac/Aza/S: 7.1%). Moreover, kidney function was well preserved in steroid-free patients with month 6 median serum creatinine levels of 119.5 micromol/l (Tac/MMF), and 115.1 micromol/l (Tac/Aza). For patients who continued to receive steroids, month 6 median creatinine levels were 130.5 micromol/l (Tac/MMF/S) and 132.8 micromol/l (Tac/Aza/S). The criteria for the selection of patients to discontinue steroids were adequate. Both tacrolimus-based regimens allowed the safe discontinuation of steroids in low-risk patients at month 3. The Tac/MMF combination was superior in the prevention of acute rejections and more patients met the chosen criteria for steroid withdrawal.     

Über die Pathogenese und eine neuartige Therapie des „paralytischen Ileus”

Zusammenfassung Wir k?nnen sagen, da? aufgrund dieser Untersuchungen der Begriff des „paralytischen” Ileus einer Revision bedarf, da es sich um keine echte Paralyse oder Parese handelt, vielmehr um eine Hemmung der Darmt?tigkeit durch den erh?hten sympathischen Tonus. Durch entsprechende Sympathicolytica kann das physiologische Gleichgewicht der autonomen Innervation wiederhergestellt werden. In diesem Sinne sollte man den sogenannten paralytischen Ileus eher als einen sympathicotonischen oder adrenergischen Ileus bezeichnen.

---

Summary Based on clinical experience of 12 years sympathicolytic compounds of different mode of action were tested in cats. Many of these drugs unaequivocally induced peristalsis in narcotized and laparotomized cats with peristaltic standstill. Major tranquilizers (chlorpromazine, butyrophenons) act by relieving sympathetic inhibition of the peristaltic reflex, i.e. at the site of the intramural plexus. Clinical indications and results are discussed. It is suggested that what used to be termed as “paralytic” ileus is actually an expression of sympathetic overactivity which often follows trauma or surgical stress.

---

---

a. G.     

Peritubular capillaries in chronic renal allograft rejection: a quantitative ultrastructural study

Peritubular capillaries (PCs) with a circumferentially multilayered basement membrane have been suggested as an ultrastructural indicator of chronic renal allograft rejection (CR). The authors validated this lesion as a marker for CR, by analyzing its quantitative features, specificity, and sensitivity in 169 renal biopsy specimens. The mean number of circumferential layers (PCcirc) and the incidences of the grades (mild: 2 to 4, moderate: 5 to 6, severe: 7 or more layers) were investigated in biopsy specimens involving CR (CR(Bx), n = 46), acute rejection (n = 11), normal kidneys (n = 20), psoriatics treated with cyclosporine (n = 13), renal transplants with chronic cyclosporine toxicity (n = 12), native kidney diseases (NKD, n = 56), and transplant nephrectomies attributable to CR (Cr(nephr), n = 11). CR was diagnosed with regard to the clinical features and the presence of intimal fibrosis in 41 biopsy specimens or transplant glomerulopathy in 35 biopsy specimens (cg; identified only by electron microscopy in 10 cases). NKD included chronic glomerulonephritis, chronic tubulointerstitial nephritis, benign nephrosclerosis, thrombotic microangiopathy, diabetic nephropathy, and renal disease in elderly patients (median age, 72 years). All PCs around glomeruli were sampled (median, 14 profiles per case). PCs with a moderate/ severe lesion appeared as serrated profiles with a thick, ribbon-like basement membrane layer in semithin plastic sections. The numbers of circumferentially multilayered PCs were significantly characteristic of CR (PCcirc in CR(Bx): 2.87+/-1.83 SD; range, 0 to 7.36; P < .001 v other groups). A severe lesion occurred exclusively in CR (in 12% of the PCs in CR(Bx), and in 38% in CRnephr). A moderate lesion was observed in 0.6% of the PCs in NKD, 16% in CR(Bx), and 21% in CRnephr. Three or more PCs with a moderate lesion were encountered only in CR. A mild lesion was not suggestive of CR at all. In CR(Bx), 27 cases showed a severe lesion or 3 or more PCs with a moderate lesion (cpc; sensitivity: 59%). Four of the 27 cases lacked cg. The cumulative incidence of cpc and cg was 85%. In transplants with cyclosporine toxicity, the presence of cpc verified the coexistence of CR in 7 specimens. In conclusion, cpc is a specific marker of CR. The incidence of cpc increases as CR progresses. The lesion may be caused by a low-grade rejection injury to the PCs. Careful analysis of semithin sections promotes the better sampling of cpc. An ultrastructural demonstration of cpc and cg defines CR more precisely than does light microscopic evaluation per se.     

Steroid sensitivity of chronic uraemic and renal transplant patients measured by the antibody dependent cellular cytotoxicity reaction

The steroid (methylprednisolone) sensitivity of chronic uraemic and renal transplant patients was examined on the basis of the extent of inhibition of the antibody-dependent cellular cytotoxicity (ADCC) reaction, and via the effect on the ADCC capacity test (ADCC-C). Individuals with an inhibition of 30% or more were classified as steroid-sensitive. Immunopharmacological tests and the clinical picture showed 67%, 12 of the 18 renal transplant patients to be steroid-sensitive. In 92% of the cases the transplanted kidney was functioning well one year or more postoperatively. In 5 of the 6 steroid-resistant patients rejection necessitated removal of the transplanted kidney. The method is simple to perform and gives reproducible results, and appears suitable for application in clinical practice.