Paediatric population pharmacokinetic modelling to assess hydrocortisone replacement dosing regimens in young children

CONTEXT

Accurate hydrocortisone dosing in children with adrenal insufficiency is important to avoid the risks of over and under treatment including iatrogenic Cushing's syndrome and adrenal crisis.

OBJECTIVE

To establish a population pharmacokinetic model of hydrocortisone in children and use this to refine hydrocortisone replacement regimens.

DESIGN AND METHODS

Pharmacokinetic study of hydrocortisone granules, available in 0.5, 1, 2 and 5 mg dose strengths, in 24 children with adrenal insufficiency aged 2 weeks to 6 years. Cortisol concentrations quantified by LC-MS/MS were used to refine an adult pharmacokinetic model to a paediatric population model which was then used to simulate seven different hydrocortisone treatment regimens.

RESULTS

Pre-dose cortisol levels were undetectable in 54% of the 24 children. The developed pharmacokinetic model had good predictive performance. Simulations for the seven treatment regimens using either three- or four-times daily dosing showed treatment regimens delivered an AUC0-24h within the 90% reference range for healthy children except in neonates where two regimens had an AUC below the 5th percentile. Cortisol concentrations at individual time points in the 24 h were outside the 90% reference range for healthy individuals in 50%, 55-65% and 70-75% for children, infants and neonates, respectively, with low cortisol levels being most prevalent.

CONCLUSIONS

Current paediatric hydrocortisone treatment regimens based on either three- or four-times daily administration replicate cortisol exposure based on AUC0-24h, but the majority of cortisol levels are above or below physiological cortisol levels with low levels very common before the next dose.

Does expanded polytetrafluoroethylene mesh really shrink after laparoscopic ventral hernia repair?

BACKGROUND

The shrinkage of mesh has been cited as a possible explanation for hernia recurrence. Expanded polytetrafluoroethylene (ePTFE) is unique in that it can be visualized on computed tomography (CT). Some animal studies have shown a greater than 40% rate of contraction of ePTFE; however, very few human studies have been performed.

STUDY DESIGN

A total of 815 laparoscopic incisional/ventral hernia (LIVH) repairs were performed by a single surgical group. DualMesh Plus (ePTFE) (WL Gore & Associates, Newark, DE) was placed in the majority of these patients using both transfascial sutures and tack fixation. Fifty-eight patients had postoperative CTs of the abdomen and pelvis with ePTFE and known transverse diameter of the implanted mesh. The prosthesis was measured on the CT using the AquariusNet software program (TeraRecon, San Mateo, CA), which outlines the mesh and calculates the total length. Data were collected regarding the original mesh size, known linear dimension of mesh, seroma formation, and time interval since mesh implantation in months.

RESULTS

The mean shrinkage rate was 6.7%. The duration of implantation ranged from 6 weeks to 78 months, with a median of 15 months. Seroma was seen in 8.6% (5) of patients. No relationship was identified between the percentage of shrinkage and the original mesh size (P = 0.78), duration of time implanted (P = 0.57), or seroma formation (P = 0.074). In 27.5% (16) of patients, no shrinkage of mesh was identified. Of the patients who did experience mesh shrinkage, the range of shrinkage was 2.6-25%.

CONCLUSIONS

Our results are markedly different from animal studies and show that ePTFE has minimal shrinkage after LIVH repair. The use of transfascial sutures in addition to tack fixation may have an implication on the mesh contraction rates.

Laparoscopic parastomal hernia repair

Repair of parastomal represents a significant challenge for the hernia surgeon. Repair of these hernias is indicated because of an ill-fitting appliance, cosmetic deformity, inability to maintain proper hygiene and complications from the hernia itself such as incarceration or strangulation. Recent reports in the literature have shown that primary fascial repair can occur in 46% of patients and relocation of the stoma is associated with a 40% recurrence rate. For this reason, the use of polypropylene mesh has been applied to this repair. The recurrence rate with this open technique will still incur a failure rate of 20-29%. Additionally there are other complications such as obstruction, fistulization or mesh erosion with this biomaterial. The laparoscopic approach to this hernia may offer a new choice for this difficult problem. We have used ePTFE to repair 12 parastomal hernias with three different approaches. There have been eight colostomy, two ileostomy and two urostomy hernias. Follow-up ranges from 3-39 months (average 20 months). There has been one recurrence that required two repairs (8%). Other complications included enterotomy (one patient), ileus (one), seroma (one), and death from postoperative aspiration (one). The laparoscopic repair of parastomal hernias appears to be a promising technique for this complex dilemma.

Laparoscopic incisional and ventral hernioplasty: lessons learned from 200 patients

Our first 100 patients and our second 100 patients who underwent a laparoscopic repair of incisional and ventral hernias were compared and evaluated. This analysis revealed that the second group was approximately 9 years older with more comorbid medical conditions. In all, 15% were incarcerated hernias, and 21% were recurrent. Seven operations were converted to the open repair because of adhesions in five patients and either a small or large bowel injury in two patients. There were no complications related to enterotomy. Older and more infirm patients in the second group did not significantly affect outcomes. The average size of the hernia defects was 111 cm2. The average size of the prosthesis was 257.5 cm2. Larger prostheses were used in the second group. With more experience, the recurrence rates have declined from 9% to 4%. The etiology of these recurrences differed in these two groups of patients. Removal of the prosthetic due to infection was a predictable recurrence in two patients. A new hernia below the original hernia has caused us to repair the entire incision that had the initial hernia. Only one technical failure was noted, due to fracture of the suture during transfascial placement and clamping of the suture. It is not recommended to grasp any suture that remains in the patient during this hernioplasty. Recurrences were reduced because of the use of an increased overlap of the biomaterial and the use of dual methods of fixation (tacks and transfascial sutures).

Management of chronic postoperative pain following incisional hernia repair with Composix mesh: a report of two cases

There are new prosthetic biomaterials that are used to repair various defects in the abdominal wall. These have been developed within the last several years. The results of many of these products are not yet available. We report on two patients who developed chronic-pain syndromes that could only be related to the use of Composix mesh. This entity may become more conspicuous in the future, thereby presenting the surgeon with difficulty in approaching this new and difficult problem. We believe that shrinkage of the prosthesis was responsible for the pain. Both of these patients responded favorably to resection of the mesh by the open or laparoscopic technique. This was followed by repair of the fascial defect with DualMesh by the open or laparoscopic method. We were successful in the achievement of the relief of the pain and the repair of the hernia in both cases. We believe that this entity can be treated successfully by this approach. The laparoscopic method is favored.

Laparoscopic incisional and ventral herniorraphy: our initial 100 patients

A review of our initial 100 patients upon whom we attempted a laparoscopic repair of either a ventral and incisional hernia is presented. The average follow-up period of these individuals was 51 months. The operation was completed with the laparoscopic technique in 96 cases. The average defect size was 155 cm2 and the average prosthetic biomaterial size to repair these defects was 214.8 cm2. The major complication rate was 4.1%. The incidence of recurrence in these patients was 9.3%. In all of these cases of recurrence, the method of attachment was that of staples or spiral tacks alone. In 5 patients, it appeared that the prosthesis was too small to cover the defect adequately. We believe that this is an effective operation but one that has two technical mandates. The prosthetic biomaterial (DualMesh) must cover the fascial edges by a minimum of a three-centimeter overlap. Additionally, the attachment of the patch by staples or tacks alone is inadequate; consequently, the herniorraphy must include the use of through and through sutures to assure adequate fixation of the prosthesis.

Plantar verrucae in patients with human immunodeficiency virus. Clinical presentation and treatment response

Several previous studies have yielded data showing that plantar and other cutaneous verrucae follow a more aggressive course in patients infected with human immunodeficiency virus (HIV) than in uninfected individuals. A pilot study was undertaken to identify trends in a sample population that would support this characterization of plantar verrucae in HIV+ patients and to determine whether there are differences in treatment response between HIV+ and HIV- patients. The results show that the HIV+ patients in the study presented with a significantly greater number and total area of lesions than did the HIV- patients. Furthermore, the HIV+ patients experienced a greater frequency of recurrence of their lesions following treatment with surgical curettage. These findings should provide the foundation for other extensive, multicenter studies to further characterize the treatment response of these lesions in HIV+ patients and to develop effective guidelines for their management.

Laparoscopic incisional and ventral herniorrhaphy in 100 patients

BACKGROUND

Laparoscopic incisional and ventral herniorrhaphy, a procedure first described 7 years ago, continues to gain acceptance. A series of about 100 patients who underwent the operation is described. Follow-up in this series was longer (mean 51 months) than that in previously reported series.

METHODS

A retrospective review was conducted of operative and follow-up records of a series of patients scheduled to undergo laparoscopic incisional or ventral herniorrhaphy between 1992 and 1997.

RESULTS

Laparoscopic repair was completed in 96 of 100 patients. The complication rate was 14%, with seromas accounting for half of the postoperative problems. Mean hospital stay was 1 day. The late recurrence rate was 9%, with 4 of the 9 recurrences developing >2 years postoperatively.

CONCLUSIONS

Laparoscopic incisional and ventral herniorrhaphy is safe and effective. Most patients require hospitalization for </=24 hours. Use of an adequately sized prosthesis secured with more than one method is essential. Patients should be observed >/=3 years.

Human alpha1,3/4-fucosyltransferases. III. A Lys/Arg residue located within the alpha1,3-FucT motif is required for activity but not substrate binding

Amino acid sequence alignment of human alpha1, 3/4-fucosyltransferases (FucTs) demonstrates that three highly conserved Lys residues are present in the catalytic domain of FucTs III, IV, V, and VI. Two of these sites are conserved in FucT VII, with the third located within the alpha1,3-FucT motif as a conservative change to Arg at position 223. Site-directed mutagenesis experiments were conducted to change Lys255 of FucT V (equivalent to Arg223 of FucT VII) to either Arg255 or Ala255. Enzyme assays demonstrate that the FucT V K255R mutant has a 34-fold lower specific activity than native FucT V and that the K255A mutant is inactive. Site-directed mutagenesis of FucT VII was also conducted to change Arg223 to Lys223 for analysis of the effect on enzyme kinetic parameters. No differences in acceptor specificities or Km values for either substrate were observed between native FucT VII and the R223K mutant; however, the purified R223K mutant enzyme had a 2-fold increased specific activity compared with purified native FucT VII. No change in GDP-fucose-protectable pyridoxal-P/NaBH4 inactivation was observed for native or mutant FucT V or VII, further supporting the absence of involvement of this residue in sugar nucleotide binding. The results indicate that a basic residue in this position is required for enzyme activity, with a Lys residue providing higher intrinsic activity. The lack of influence of this site on substrate binding parameters and its location within the alpha1,3-FucT motif suggest that at least some of the residues within this motif are involved in catalysis rather than substrate binding.

Human alpha1,3/4-fucosyltransferases. I. Identification of amino acids involved in acceptor substrate binding by site-directed mutagenesis

In a previous study (Xu, Z., Vo, L., and Macher, B. A. (1996) J. Biol. Chem. 271, 8818-8823), a domain swapping approach demonstrated that a region of amino acids found in human alpha1, 3/4-fucosyltransferase III (FucT III) conferred a significant increase in alpha1,4-FucT acceptor substrate specificity into alpha1, 3-fucosyltransferase V (FucT V), which, under the same assay conditions, has extremely low alpha1,4-FucT acceptor substrate specificity. In the current study, site-directed mutagenesis was utilized to identify which of the eight amino acids, associated with alpha1,4-FucT acceptor substrate specificity, is/are responsible for conferring this new property. The results demonstrate that increased alpha1,4-FucT activity with both disaccharide and glycolipid acceptors can be conferred on FucT V by modifying as few as two (Asn86 to His and Thr87 to Ile) of the eight amino acids originally swapped from FucT III into the FucT V sequence. Neither single amino acid mutant had increased alpha1,4-FucT activity relative to that of FucT V. Kinetic analyses of FucT V mutants demonstrated a reduced Km for Galbeta1,3GlcNAc (type 1) acceptor substrates compared with native FucT V. However, this was about 20-fold higher than that found for native FucT III, suggesting that other amino acids in FucT III must contribute to its overall binding site for type 1 substrates. These results demonstrate that amino acid residues near the amino terminus of the catalytic domain of FucT III contribute to its acceptor substrate specificity.

In vivo study of meshes implanted over the inguinal ring and external iliac vessels in uncastrated pigs

BACKGROUND

The effects of placing a prosthesis directly on the internal inguinal ring and external iliac vessels in inguinal hernia repair are unknown. We compared tissue responses to five prostheses implanted in this position in uncastrated male pigs.

METHODS

Three types of polypropylene and two types of expanded polytetrafluoroethylene (ePTFE) mesh were implanted in 20 pigs (n = 8 for each prosthesis type). Specimens of the implants and surrounding tissue were obtained 30 and 90 days after implantation and assessed histologically.

RESULTS

The polypropylene implants had more adhesions, more surface area covered by adhesions, and more tenacious adhesions than did the ePTFE implants. Perivascular cuffing was observed in eight polypropylene and one ePTFE specimen; ossification, necrosis, and testicular venous congestion were seen in polypropylene specimens.

CONCLUSIONS

Abnormal healing processes after implantation of polypropylene mesh may increase complications of the transabdominal preperitoneal and total extraperitoneal approaches in laparoscopic inguinal hernia repair, whereas the minimal response to ePTFE meshes may make them safer for use in the preperitoneal space.

The double stapling technique for low anterior resection. Results, modifications, and observations

Since the introduction of the end-to-end anastomosis (EEA) stapler for rectal reconstruction, we have used a modification of the conventional technique in which the lower rectal segment is closed with the linear stapler (TA-55) and the anastomosis is performed using the EEA instrument across the linear staple line (double stapling technique). Our experience with this procedure includes stapled colorectal anastomoses in 75 patients and is the basis for the report. This review presents the details and advantages of the technique and the results. Complications include two patients with anastomotic leak (2.7%), and two with stenosis that required treatment (2.7%). Protective colostomy was not done in this series. There were no deaths. Our experience and that of others suggests that this modification of the EEA technique can allow a lower anastomosis in some patients, and that it can be done with greater safety and facility.

A comprehensive community-based youth diversion program

The authors describe a community-based program to divert youths from the juvenile justice system. The program's special features and (1) data collection that permits evaluation and accountability, and (2) liaison with justice personnel, service agencies, and the community.

Characterization of an inhibitor of granulocyte/monocyte colony formation in leukemic chicken plasma

The plasma of chicks with myeloblastic leukemia (induced by avian myeloblastosis virus, AMV) contained an inhibitor which blocked colony formation in vitro by marrow cells. It eluted in the second protein peak obtained by Sephadex G-200 gel filtration and was found in the diafiltrate following defiltration through a UM 10 membrane under acidic conditions. It was not extractable with chloroform, was heat-stable (65 degrees C, 30 min), pronase-sensitive and had a molecular weight less than or equal to 5000 daltons as determined by high performance liquid chromatography. Thus, it appears to be a small, acid-soluble, heat-stable peptide. It had no interferon activity. It was not present or present only at very low levels in normal plasma. Furthermore, it was not elevated in chicks infected only with the nonleukemogenic helper virus of AMV, and was, therefore, associated with leukemia rather than virus-replication. Leukemic myeloblasts, purified by passage in suspension culture, released the inhibitor. It acted directly on the colony-forming cell and inhibited normal cells much more than leukemic cells. In normal marrow, macrophage and granulocyte progenitors were affected. A similar inhibitor in normal plasma inhibited only granulocyte progenitors.

The use of cellulose products to reduce agar concentration in microbiological media

The use of agar in media for culturing microorganisms is fundamental to microbiological investigations. Shortages of agar have caused increased costs and difficulty in obtaining media. Evidence is presented for the use of carboxymethylcellulose (CMC), an inert compound, in conjunction with agar to reduce the concentration of agar necessary to achieve a solid plating surface. A variety of bacteria, blue-green bacteria, fungi, and a yeast were tested for growth on CMC agar media. T-2 bacteriophage and three cyanophages were tested for plaque-forming efficiency on CMC agar plates. Selective and differential media were also formulated with a CMC agar supplement. Growth of all microorganisms was comparable on CMC and agar control. Use of cellulose products provides a means of decreasing agar consumption without affecting successful cultivation of microorganisms.