Perioperative intravenous contrast administration and the incidence of acute kidney injury after major gastrointestinal surgery: prospective, multicentre cohort study

BACKGROUND

This study aimed to determine the impact of preoperative exposure to intravenous contrast for CT and the risk of developing postoperative acute kidney injury (AKI) in patients undergoing major gastrointestinal surgery.

METHODS

This prospective, multicentre cohort study included adults undergoing gastrointestinal resection, stoma reversal or liver resection. Both elective and emergency procedures were included. Preoperative exposure to intravenous contrast was defined as exposure to contrast administered for the purposes of CT up to 7 days before surgery. The primary endpoint was the rate of AKI within 7 days. Propensity score-matched models were adjusted for patient, disease and operative variables. In a sensitivity analysis, a propensity score-matched model explored the association between preoperative exposure to contrast and AKI in the first 48 h after surgery.

RESULTS

A total of 5378 patients were included across 173 centres. Overall, 1249 patients (23·2 per cent) received intravenous contrast. The overall rate of AKI within 7 days of surgery was 13·4 per cent (718 of 5378). In the propensity score-matched model, preoperative exposure to contrast was not associated with AKI within 7 days (odds ratio (OR) 0·95, 95 per cent c.i. 0·73 to 1·21; P = 0·669). The sensitivity analysis showed no association between preoperative contrast administration and AKI within 48 h after operation (OR 1·09, 0·84 to 1·41; P = 0·498).

CONCLUSION

There was no association between preoperative intravenous contrast administered for CT up to 7 days before surgery and postoperative AKI. Risk of contrast-induced nephropathy should not be used as a reason to avoid contrast-enhanced CT.

Comparison of paracorporeal and continuous flow ventricular assist devices in children: preliminary results

Objectives

With the scarcity of organs, a durable, reliable ventricular assist device (VAD) is required. The Berlin Heart EXCOR ® (BH) remains the most established VAD in the paediatric population. Implantable continuous flow (CF) VADs have been introduced to the paediatric field with encouraging early results. In this study, we compared the results of a newly introduced CF VAD (HeartWare VAD [HVAD] ® ) to results in a matched group of BH recipients.

Methods

The study included patients aged <16 years who received mechanical left VAD (LVAD) support between December 2005 and January 2016. The preimplant characteristics and postimplant outcomes of patients who received the HVAD were compared with those of a matched group who received the BH. Patients with congenital heart disease were excluded.

Results

Thirty patients were included in the study: 13 had received the HVAD and were matched with 17 patients who had received the BH LVAD. The only difference in preimplant characteristics was the need for higher inotropic support in the BH group. There was no difference in the need for right ventricular (RV) support (58.8% for BH vs 53.8% for HVAD, P  = 1.00) or in the incidence of cerebrovascular accidents (12.5% vs 7.7%, respectively, P  = 1.00), though the BH group showed prolonged mechanical ventilation (31.3% vs 0%, P  = 0.047). There were no deaths while on VAD support in either group. Patients with the HVAD showed a bimodal distribution for the primary end point (transplant/explant): All HVAD recipients who also required early RV support reached this end point within 30 days of receiving the implant.

Conclusions

Our early experience with the CF intracorporeal LVAD system (HVAD) indicates outcomes comparable to those with the well-established pulsatile flow paracorporeal LVAD (BH). The theoretical durability of the CF device, which might also allow for the possibility of hospital discharge and better quality of life, is yet to be proven.

X-ray bang-time and fusion reaction history at picosecond resolution using RadOptic detection

We report recent progress in the development of RadOptic detectors, radiation to optical converters, that rely upon x-ray absorption induced modulation of the optical refractive index of a semiconductor sensor medium to amplitude modulate an optical probe beam. The sensor temporal response is determined by the dynamics of the electron-hole pair creation and subsequent relaxation in the sensor medium. Response times of a few ps have been demonstrated in a series of experiments conducted at the LLNL Jupiter Laser Facility (JLF). This technology will enable x-ray bang-time and fusion burn-history measurements with ∼ ps resolution.

The determinants of periorbital skin ageing in participants of a melanoma case-control study in the U.K

BACKGROUND

Skin ageing is said to be caused by multiple factors. The relationship with sun exposure is of particular interest because the detrimental cutaneous effects of the sun may be a strong motivator to sun protection. We report a study of skin ageing in participants of an epidemiological study of melanoma.

OBJECTIVES

To determine the predictors of periorbital cutaneous ageing and whether it could be used as an objective marker of sun exposure.

METHODS

Photographs of the periorbital skin in 1341 participants were graded for wrinkles, degree of vascularity and blotchy pigmentation and the resultant data assessed in relation to reported sun exposure, sunscreen use, body mass index (BMI), smoking and the melanocortin 1 receptor (MC1R) gene status. Data were analysed using proportional odds regression.

RESULTS

Wrinkling was associated with age and heavy smoking. Use of higher sun-protection factor sunscreen was protective (P = 0·01). Age, male sex, MC1R variants ('r', P=0·01; 'R', P=0·02), higher reported daily sun exposure (P=0·02), increased BMI (P=0·01) and smoking (P=0·02) were risk factors for hypervascularity. Blotchy pigmentation was associated with age, male sex, higher education and higher weekday sun exposure (P=0·03). More frequent sunscreen use (P=0·02) and MC1R variants ('r', P=0·03; 'R', P=0·001) were protective.

CONCLUSIONS

Periorbital wrinkling is a poor biomarker of reported sun exposure. Vascularity is a better biomarker as is blotchy pigmentation, the latter in darker-skinned individuals. In summary, male sex, sun exposure, smoking, obesity and MC1R variants were associated with measures of cutaneous ageing. Sunscreen use showed some evidence of being protective.

Cost-effectiveness of cell salvage and alternative methods of minimising perioperative allogeneic blood transfusion: a systematic review and economic model

OBJECTIVES

To compare patient outcomes, resource use and costs to the NHS and NHS Blood Transfusion Authority (BTA) associated with cell salvage and alternative methods of minimising perioperative allogeneic blood transfusion.

DATA SOURCES

Electronic databases covering the period 1996-2004 for systematic reviews and 1994-2004 for economic evidence.

REVIEW METHODS

Existing systematic reviews were updated with data from selected randomised controlled trials (RCTs) that involved adults scheduled for elective non-urgent surgery. Any resource use or cost data were extracted for potential use in populating an economic model. Relative risks or weighted mean difference of each outcome for each intervention were assessed, taking into account the number of RCTs included in each outcome and intervention and the presence of any heterogeneity. This allowed indirect comparison of the relative effectiveness of each intervention when the intervention is compared with allogeneic blood transfusion. A decision analytic model synthesised clinical and economic data from several sources, to estimate the relative cost-effectiveness of cell salvage for people undergoing elective surgery with moderate to major expected blood loss. The perspective of the NHS and patients and a time horizon of 1 month were used. The economic model was developed from reviews of effectiveness and cost-effectiveness and clinical experts. Secondary analysis explored the robustness of the results to changes in the timing and costs of cell salvage equipment, surgical procedure, use of transfusion protocols and time horizon of analysis.

RESULTS

Overall, 668 studies were identified electronically for the update of the two systematic reviews. This included five RCTs, of which two were cell salvage and three preoperative autologous donation (PAD). Five published systematic reviews were identified for antifibrinolytics, fibrin sealants and restrictive transfusion triggers, PAD plus erythropoietin, erythropoietin alone and acute normovolaemic haemodilution (ANH). Twelve published studies reported full economic evaluations. All but two of the transfusion strategies significantly reduced exposure to allogeneic blood. The relative risk of exposure to allogeneic blood was 0.59 for the pooled trials of cell salvage (95% confidence interval: 0.48 to 0.73). This varied by the type and timing of cell salvage and type of surgical procedure. For cell salvage, the relative risk of allogeneic blood transfusion was higher in cardiac surgery than in orthopaedic surgery. Cell salvage had lower costs and slightly higher quality-adjusted life years compared with all of the alternative transfusion strategies except ANH. The likelihood that cell salvage is cost-effective compared with strategies other than ANH is over 50%. Most of the secondary analyses indicated similar results to the primary analysis. However, the primary and secondary analyses indicated that ANH may be more cost-effective than cell salvage.

CONCLUSIONS

The available evidence indicates that cell salvage may be a cost-effective method to reduce exposure to allogeneic blood transfusion. However, ANH may be more cost-effective than cell salvage. The results of this analysis are subject to the low quality and reliability of the data used and the use of indirect comparisons. This may affect the reliability and robustness of the clinical and economic results. There is a need for further research that includes adequately powered high-quality RCTs to compare directly various blood transfusion strategies. These should include measures of health status, health-related quality of life and patient preferences for alternative transfusion strategies. Observational and tracking studies are needed to estimate reliably the incidence of adverse events and infections transmitted during blood transfusion and to identify the lifetime consequences of the serious hazards of transfusion on mortality, health status and health-related quality of life.

Exchange Transfusion During Extra Corporeal Membrane Oxygenation Used as a Bridge to ABO-Mismatch Cardiac Transplantation

We report a case in which exchange transfusion was performed directly from the extracorporeal membrane oxygenation circuit in a child being bridged to cardiac transplantation. This allowed preparation for ABO-mismatched heart transplant in a child dependent on extracorporeal support, awaiting a suitable ABO-matched donor. Exchange transfusion or plasmapheresis in this setting would normally be performed on cardiopulmonary bypass to allow exsanguinations under hypothermia immediately pre-transplant. This allows little time for depletion of isohemagglutinins, occasionally leading to prolonged bypass times. We believe our method to be a safe alternative, allowing ample time for immunological preparation for ABO-incompatible transplant.

ABO-INCOMPATIBLE HEART TRANSPLANTATION IN INFANTS: THE FREEMAN HOSPITAL EXPERIENCE

BACKGROUND

Incompatibility of the major blood groups A, B, and O has been an absolute contraindication for heart transplantation. However, because of immunologic immaturity, infants may have relative protection from hyperacute rejection and thus could undergo transplantation with ABO-mismatched organs.

METHODS

Since January 2000, the authors have adopted a policy of considering infants for ABO-incompatible heart transplantation. Serum isohemagglutinin titers were measured before, during, and after transplantation. Two infants (3 and 2 months old) and a 21-month-old child underwent ABO-incompatible heart transplantation. During cardiopulmonary bypass, plasma exchange was performed. No other antibody-removal procedures were performed. A routine immunosuppressive regimen was used, and rejection was monitored by endomyocardial biopsies. An additional two patients (31 and 18 months old) were worked up but were unsuitable for ABO-incompatible transplantation because of high isohemagglutinin titers. They were successfully bridged to transplantation and received heart transplants from ABO-compatible donors.

RESULTS

All three infants with ABO-incompatible heart transplants are fit and well, 40 months, 30 months, and 12 months postoperatively. All three had serum antibodies to antigens of the donor's blood group before transplantation. No hyperacute rejection occurred. No morbidity attributable to the ABO incompatibility has been observed.

CONCLUSIONS

ABO-mismatched heart transplantation may be undertaken safely and without any short-term adverse consequences in infants and young children in whom isohemagglutinin production is not yet established.

The waiting game: bridging to paediatric heart transplantation

BACKGROUND

Although mechanical circulatory support might not increase the number of adults surviving to transplantation, because of the shortage of donor organs, the situation might be different for children. Our aim was to assess the effect of mechanical assist devices to bridge children with end-stage cardiomyopathy to heart transplantation.

METHODS

A 5-year retrospective review was undertaken with data from the UK paediatric transplant programme and from bridging to transplant done at two paediatric transplant centres in the UK.

FINDINGS

Between Jan 1, 1998 and Dec 31, 2002, 22 children with end-stage cardiomyopathy, median age 5.7 years (range 1.2-17), were supported by a mechanical assist device as a bridge to first heart transplantation, with a 77% survival rate to hospital discharge. Nine were supported by a paracorporeal ventricular assist device, six received transplantation, five survived to discharge (55%), with one late death. 13 were supported by extra-corporeal membrane oxygenation, and 12 were transplanted and survived to discharge (92%) with one late death. With urgent listing, the median waiting time for a heart was 7.5 days (range 1.5-22 days). The correlation between the proportion of patients bridged to transplantation and the proportion of patients dying while on the transplant waiting list was r=-0.93, p=0.02.

INTERPRETATION

Our findings lend support to the hypothesis that a national mechanical assist programme to bridge children to transplantation can minimise the number dying while on the heart transplant waiting list. In the context of urgent listing and a short waiting time, extra-corporeal membrane oxygenation seems to provide the safest form of support.

Diversity of bacteria associated with natural aphid populations

The bacterial communities of aphids were investigated by terminal restriction fragment length polymorphism and denaturing gradient gel electrophoresis analysis of 16S rRNA gene fragments generated by PCR with general eubacterial primers. By both methods, the gamma-proteobacterium Buchnera was detected in laboratory cultures of six parthenogenetic lines of the pea aphid Acyrthosiphon pisum and one line of the black bean aphid Aphis fabae, and one or more of four previously described bacterial taxa were also detected in all aphid lines except one of A. pisum. These latter bacteria, collectively known as secondary symbionts or accessory bacteria, comprised three taxa of gamma-proteobacteria (R-type [PASS], T-type [PABS], and U-type [PAUS]) and a rickettsia (S-type [PAR]). Complementary analysis of aphids from natural populations of four aphid species (A. pisum [n = 74], Amphorophora rubi [n = 109], Aphis sarothamni [n = 42], and Microlophium carnosum [n = 101]) from a single geographical location revealed Buchnera and up to three taxa of accessory bacteria, but no other bacterial taxa, in each aphid. The prevalence of accessory bacterial taxa varied significantly among aphid species but not with the sampling month (between June and August 2000). These results indicate that the accessory bacterial taxa are distributed across multiple aphid species, although with variable prevalence, and that laboratory culture does not generally result in a shift in the bacterial community in aphids. Both the transmission patterns of the accessory bacteria between individual aphids and their impact on aphid fitness are suggested to influence the prevalence of accessory bacterial taxa in natural aphid populations.

Transfusion-related alloimmune neutropenia: an undescribed complication of blood transfusion

Alloimmune neutropenia in neonates is rare. We describe severe and persistent neutropenia in a 4-week-old neonate, which arose within 2 h of a transfusion of blood that contained about 28 mL of plasma and in which strong antibodies against human neutrophil antigen 1b (HNA-1b) were subsequently identified. The infant was positive for HNA-1b. No other likely cause of neutropenia was discovered. We believe this complication of blood transfusion to be a previously unrecognised one, and have called the condition transfusion-related alloimmune neutropenia (TRAIN).

The incidence and characteristics of neonatal irreversible lung dysplasia

A 3-year retrospective study of 173 neonates treated with extracorporeal membrane oxygenation in the United Kingdom identified 9 cases of irreversible lung dysplasia, including alveolar capillary dysplasia (n = 5), surfactant protein B deficiency (n = 1), pulmonary hypoplasia (n = 1), pulmonary lymphangiectasis (n = 1), and combined lymphangiectasis and hypoplasia (n = 1).

Coagulation factor activity during neonatal extra-corporeal membrane oxygenation

OBJECTIVE

To ascertain the activity of major coagulation factors during the first 24 h of extra-corporeal membrane oxygenation (ECMO) used to support hypoxaemic neonates.

DESIGN AND SETTING

A prospective observational study in a regional centre for ECMO and paediatric cardiac surgery, placing 15-20 neonates on ECMO per year.

PATIENTS

Ten neonates receiving ECMO for severe hypoxaemia.

MEASUREMENT AND RESULTS

The activity of major clotting factors, of the inhibitor anti-thrombin III and of markers of blood activation were measured during the first 24 h of neonatal extra-corporeal membrane oxygenation (ECMO) and prior to initiation of ECMO. There was laboratory evidence of factor deficiency and of activation of coagulation at all stages. The initiation of ECMO leads to an initial worsening of coagulopathy, but factor deficiency and abnormal activation of coagulation is also seen prior to ECMO in these very sick neonates.

CONCLUSION

If factor deficiency is to be avoided a pro-active approach is required to rapidly correct factor activity. This would include the use of fresh frozen plasma. The effect of such an approach on outcome is at yet uncertain.

'Real life' clinical learning on an interprofessional training ward

This paper describes the multi-method evaluation of an interprofessional training ward placement for medical, nursing, occupational therapy and physiotherapy students. Unique in the UK, and an extension of pioneering work in Sweden (Wahlström et al. 1997, Wahlstroöm & Sandén 1998), this interprofessional clinical placement allowed senior pre-qualifying students, under the supervision of practitioners, to plan and deliver interprofessional care for a group of orthopaedic and rheumatology patients. This responsibility enabled students to develop both their profession-specific skills in a real-world setting and the quality of their interprofessional teamwork. Student teams were supported by facilitators who led reflective sessions and acted as a resource for the students' problem-based learning. The training ward was evaluated by a multi-method approach, incorporating interviews, observations and questionnaires with students, patients and clinical staff. The evaluation findings have been grouped into a number of themes which offer an insight into the varying perspectives of training ward students, patients and staff. This paper pays particular attention to the nursing perspective of the interprofessional training ward pilot.

Use of intravenous immunoglobulins as an adjunct in the conservative management of chylothorax

Two children who developed chylothorax after surgery for congenital heart disease are presented. The conservative management of chylothorax is reviewed and the use of immunoglobulins in the treatment of sepsis is discussed. One patient survived.

Pharmacokinetics of calcium absorption from two commercial calcium supplements

This study was conducted to compare pharmacokinetic indices of calcium absorption after a single oral (500 mg calcium) load of Citracal (calcium citrate) and Os-Cal (calcium carbonate). In 18 postmenopausal normal women, venous blood samples were obtained for the measurement of calcium before and hourly for 6 hours after an oral ingestion of Citracal, Os-Cal, or placebo with a breakfast meal. The change in area under the curve (delta AUC) in serum calcium from preload was 2.5-fold greater for Citracal than Os-Cal, and the peak-basal variation in serum calcium was 76% higher for Citracal than Os-Cal. The increment in serum calcium from preload after Citracal administration was significantly higher than that obtained after placebo load during most time periods and significantly higher than that of Os-Cal at 1, 4, and 5 hours after load. In contrast, delta AUC and peak basal variation of Os-Cal did not differ significantly from placebo and increment in serum calcium was significantly increased from placebo only at 6 hours. In conclusion, Citracal is much more bioavailable than Os-Cal.

Vascular surgical society of great britain and ireland: autologous transfusion reduces blood transfusion requirements in aortic surgery

BACKGROUND: Elective aortic surgery is associated with a blood loss that warrants a routine blood crossmatch of 4-6 units. Autologous transfusion strategies to reduce blood requirements were evaluated in a pilot study involving six hospitals in the North West. METHODS: Eighty patients undergoing elective aortic surgery were randomized to either autologous (a combination of acute normovolaemic haemodilution and intraoperative cell salvage) or homologous transfusion. The transfusion trigger, in the absence of pressing clinical need, was 8 g dl-1 haemoglobin for both groups. RESULTS: Randomization achieved two groups well matched for age, aneurysm or occlusive surgery, aspirin intake, estimated blood volume, preoperative haemoglobin and aneurysm size. In the 'best' hospitals (n = 49) mean(s.d.) blood loss (630(49) ml) was significantly lower (P < 0.01) than that in the 'worst' hospitals (1077(110) ml, n = 31) and fewer patients required transfusion (nine of 42 versus 15 of 30; P < 0.05). No significant differences were found between homologous and autologous groups for all variables measured in the 'best' hospitals. In the 'worst' hospitals blood requirements were significantly higher (P < 0.05) for the homologous group (800(112) ml) compared with the autologous group (489(65) ml), although blood loss was similar (1239(195) versus 915(92) ml respectively). CONCLUSION: Autologous transfusion techniques significantly reduced homologous blood requirements in aortic surgery where blood loss exceeded 800 ml.

Telomere length shortening is associated with disease evolution in chronic myelogenous leukemia

We studied telomere length in the peripheral blood leukocyte samples of a large group of patients with chronic myelogenous leukemia (CML) by Southern blot hybridization using the (TTAGGG)4 probe. The average telomere length expressed as the peak telomere repeat array (TRA) of the peripheral blood samples obtained from a group of 34 healthy age-matched controls ranged between 7.6 and 10.0 kb and the mean peak TRA was 8.7 kb. Forty-one patients in the chronic phase of CML were studied; 32/41 (78%) showed telomere reduction (<7.6 kb) relative to age-matched controls and the mean peak TRA was 6.4 kb (range 4.0-10.6 kb). Serial samples were analysed from 12 patients at both chronic phase and during disease progression. The leukocyte DNA of all 12 patients in accelerated phase and/or blast crisis showed telomere reduction relative to age-matched controls and the mean peak TRA was 4.1 kb (range 3.0-5.4 kb). The peak TRA in the accelerated or blast phase was reduced compared with the corresponding paired sample in the chronic phase in all cases studied. These data show that a marked reduction in telomere length is associated with disease progression in CML.

Intrathoracic tracheal rupture

This paper reports five new cases of intrathoracic tracheal rupture in cats, and summarizes these cases in conjunction with 11 cases from the literature. Most cats had no obvious respiratory signs at the time of injury, and in half of them the tracheal rupture was the only injury. The interval from trauma to onset of dyspnoea ranged from 1 to 28 days (median 12.5 days). Radiographic findings include loss of continuity of the trachea, often with a gas-filled diverticulum present between separated tracheal rings. With careful attention to surgical technique and anaesthetic management the prognosis for these cats is excellent. All eight of the cats reported in the last 14 years having surgical correction survived and returned to normal. The surgical anatomy, approach and tracheal anastomosis technique is described and recommendations for anaesthetic management are made.

Converting enzyme inhibition causes hypocitraturia independent of acidosis or hypokalemia

BACKGROUND

Angiotensin II stimulates the proximal tubular Na/H antiporter and increases proximal tubular cell pH. Because intracellular pH may affect urinary citrate excretion and enzymes responsible for renal citrate metabolism, the present studies examined the effect of enalapril, an angiotensin converting enzyme inhibitor, on the activity of renal cortical ATP citrate lyase and urinary citrate excretion.

METHODS

Enalapril was given to rats (15 mg/kg/day) for seven days and to humans (10 mg twice daily) for 10 days. Blood and 24-hour urine samples were obtained in both groups. Renal cortical tissue from rats was analyzed for enzyme activity.

RESULTS

In rats, enalapril decreased urinary citrate excretion by 88%. The change in urinary citrate was not associated with a difference in plasma pH, bicarbonate nor potassium concentration. However, similar to metabolic acidosis and hypokalemia, enalapril caused a 42% increase in renal cortical ATP citrate lyase activity. When given to humans, enalapril significantly decreased urinary citrate excretion and urine citrate concentration by 12% and 16%, respectively, without affecting plasma pH or electrolytes.

CONCLUSIONS

Enalapril decreases urinary citrate in rats and humans. This is due, at least in part, to increases in cytosolic citrate metabolism through ATP citrate lyase in rats similar to that seen with chronic metabolic acidosis and hypokalemia. The effects of enalapril on urinary citrate and renal cortical ATP citrate lyase occur independently of acidosis or hypokalemia but may be due to intracellular acidosis that is common to all three conditions.

Isolation from phage display libraries of single chain variable fragment antibodies that recognize conformational epitopes in the malaria vaccine candidate, apical membrane antigen-1

Phage display of single chain variable fragment (scFv) antibodies is a powerful tool for the selection of important and useful antibody specificities. We have constructed such a library from mice protected from malaria challenge by immunization with recombinant Plasmodium chabaudi DS apical membrane antigen (AMA-1). Panning on refolded AMA-1 enriched a population of scFvs which specifically bound the antigen. The single chain antibodies recognize conformational epitopes on AMA-1 from the P. chabaudi DS strain but not on AMA-1 of the 556KA strain of P. chabaudi. A subset of the antibody fragments recognized AMA-1 from the human malaria parasite Plasmodium falciparum. Nucleotide sequencing revealed that at least four unique scFv genes were selected by the panning procedure. These scFv antibodies are valuable reagents for probing the structure and function of AMA-1 and will be used to test the feasibility of using recombinant antibodies in a passive immunization therapy against malaria.

Absence of the beta subunit (cchb1) of the skeletal muscle dihydropyridine receptor alters expression of the alpha 1 subunit and eliminates excitation-contraction coupling

The multisubunit (alpha 1s, alpha 2/delta, beta 1, and gamma) skeletal muscle dihydropyridine receptor transduces transverse tubule membrane depolarization into release of Ca2+ from the sarcoplasmic reticulum, and also acts as an L-type Ca2+ channel. The alpha 1s subunit contains the voltage sensor and channel pore, the kinetics of which are modified by the other subunits. To determine the role of the beta 1 subunit in channel activity and excitation-contraction coupling we have used gene targeting to inactivate the beta 1 gene. beta 1-null mice die at birth from asphyxia. Electrical stimulation of beta 1-null muscle fails to induce twitches, however, contractures are induced by caffeine. In isolated beta 1-null myotubes, action potentials are normal, but fail to elicit a Ca2+ transient. L-type Ca2+ current is decreased 10- to 20-fold in the beta 1-null cells compared with littermate controls. Immunohistochemistry of cultured myotubes shows that not only is the beta 1 subunit absent, but the amount of alpha 1s in the membrane also is undetectable. In contrast, the beta 1 subunit is localized appropriately in dysgenic, mdg/mdg, (alpha 1s-null) cells. Therefore, the beta 1 subunit may not only play an important role in the transport/insertion of the alpha 1s subunit into the membrane, but may be vital for the targeting of the muscle dihydropyridine receptor complex to the transverse tubule/sarcoplasmic reticulum junction.

The lack of influence of long-term potassium citrate and calcium citrate treatment in total body aluminum burden in patients with functioning kidneys

BACKGROUND

It has been suggested that citrate salts might enhance aluminum (Al) absorption from a normal diet, posing a threat of Al toxicity even in subjects with normal renal function. We have recently reported that in normal subjects and patients with moderate renal failure, short-term treatment with tricalcium dicitrate (Ca3Cit2) does not significantly change urinary and serum Al levels. However, we have not assessed total body Al stores in patients on long-term citrate treatment.

OBJECTIVE

The objective of this study was to ascertain body content of Al non-invasively using the increment in serum and urinary Al following the intravenous administration of deferoxamine (DFO) in patients with kidney stones and osteoporotic women undergoing long-term treatment with potassium citrate (K3Cit) or Ca3Cit2, respectively.

METHODS

Ten patients with calcium nephrolithiasis and five with osteoporosis who were maintained on potassium citrate (40 mEq/day or more) or calcium citrate 800 mg calcium/day (40 mEq citrate) for 2 to 8 years, respectively, and 16 normal volunteers without a history of regular aluminum-containing antacid use participated in the study. All participants completed the 8 days of study, during which they were maintained on their regular home diet. Urinary Al excretion was measured during a two-day baseline before (Days 5, 6) and for 1 day (Day 7) immediately following a single intravenous dose of DFO (40 mg/kg). Blood for Al was obtained before DFO administration, and at 2, 5 and 24 hours following the start of the infusion.

RESULTS

The median 24-hour urinary Al excretion (microgram/day) at baseline versus post-DFO value was 15.9 vs. 44.4 in the normal subjects and 13.3 vs. 35.7 in the patients. These values were all within normal limits and did not change significantly following DFO infusion (p = 0.003 and p = 0.0001, respectively). The median change of 17.1 micrograms/day in urinary Al in the normal subjects was not significantly different from the 18.7 micrograms/day change measured in the patient group (p = 0.30). Similarly, no change in the mean serum Al was detected at any time following the DFO infusion, either in the patient or control group (patients 4.1 to 4.3 ng/ml, controls 7.4 to 4.6 ng/ml).

CONCLUSION

The results suggest that abnormal total body retention of Al does not occur during long-term citrate treatment in patients with functioning kidneys.

The reproducibility and repeatability of the Wits analysis

Since the introduction of the Wits analysis, the validity of the method has been questioned, as the functional occlusal plane in particular has been cited as a major source of error. This may be either subjectively placed or defined by existing cephalometric methods. A study is therefore reported of the repeatability (intraobserver comparison) and reproducibility (interobserver comparison) of the Wits assessment on the basis of a double series of tracings by each of two observers. No statistically significant difference was found for the repeatability of distance AO-BO by either observer, but interobserver repeatability was less satisfactory, and the mean values varied by approximately 75%. It was also found that the highest single error between two series of tracings was 3.1 mm (observer A) and 5.8 mm (observer B).