Addressing Acid-Catalyzed Deamidation and the Solubility of Hydrophobic Peptides in Multi-Attribute Method Workflows

Recently, we introduced an optimized and automated Multi-Attribute Method (MAM) workflow, which (a) significantly reduces the number of missed cleavages using an automated two-step digestion procedure and (b) dramatically reduces chromatographic peak tailing and carryover of hydrophobic peptides by implementing less retentive reversed-phase column chemistries. Here, further insights are provided on the impact of postdigest acidification and the importance of maintaining hydrophobic peptides in solution using strong chaotropic agents after digestion. We demonstrate how oxidation can significantly increase the solubility of hydrophobic peptides, a fact that can have a profound impact on quantitation of oxidation levels if care is not taken in MAM workflows. We conclude that (a) postdigestion acidification can result in significant acid-catalyzed deamidation during storage in an autosampler at 5 °C and (b) a strong chaotropic agent, such as guanidine hydrochloride, is critical for preventing loss of hydrophobic peptides through adsorption, which can result in (sometimes extreme) biases in quantitation of tryptophan oxidation levels. An optimized method is presented, which effectively addressed acid-catalyzed deamidation and solubility of hydrophobic peptides in MAM workflows.

Optimized Multi-Attribute Method Workflow Addressing Missed Cleavages and Chromatographic Tailing/Carry-Over of Hydrophobic Peptides

Peptide mapping by liquid chromatography mass spectrometry (LC-MS) and the related multi-attribute method (MAM) are well-established analytical tools for verification of the primary structure and mapping/quantitation of co- and post-translational modifications (PTMs) or product quality attributes in biopharmaceutical development. Proteolytic digestion is a key step in peptide mapping workflows, which traditionally is labor-intensive, involving multiple manual steps. Recently, simple high-temperature workflows with automatic digestion were introduced, which facilitate robustness and reproducibility across laboratories. Here, a modified workflow with an automatic digestion step is presented, which includes a two-step digestion at high and low temperatures, as opposed to the original one-step digestion at a high temperature. The new automatic digestion workflow significantly reduces the number of missed cleavages, obtaining a more complete digestion profile. In addition, we describe how chromatographic peak tailing and carry-over is dramatically reduced for hydrophobic peptides by switching from the traditional C18 reversed-phase (RP) column chemistry used for peptide mapping to a less retentive C4 column chemistry. No negative impact is observed on MS/MS-derived sequence coverage when switching to a C4 column chemistry. Overall, the new peptide mapping workflow significantly reduces the number of missed cleavages, yielding more robust and simple data interpretation, while providing dramatically reduced tailing and carry-over of hydrophobic peptides.

Deglycosylation by the Acidic Glycosidase PNGase H+ Enables Analysis of N-Linked Glycoproteins by Hydrogen/Deuterium Exchange Mass Spectrometry

Hydrogen/deuterium exchange monitored by mass spectrometry (HDX-MS) has become an important method to study the structural dynamics of proteins. However, glycoproteins represent a challenge to the traditional HDX-MS workflow for determining the deuterium uptake of the protein segments that contain the glycan. We have recently demonstrated the utility of the glycosidase PNGase A to enable HDX-MS analysis of N-glycosylated protein regions. Here, we have investigated the use of the acidic glycosidase PNGase H⁺, which has a pH optimum at 2.6, to efficiently deglycosylate N-linked glycosylated peptides during HDX-MS analysis of glycoproteins. Our results show that PNGase H⁺ retains high deglycosylation activity at HDX quench conditions. When used in an HDX-MS workflow, PNGase H⁺ allowed the extraction of HDX data from all five glycosylated regions of the serpin α₁-antichymotrypsin. We demonstrate that PNGase A and PNGase H⁺ are capable of similar deglycosylation performance during HDX-MS analysis of α₁-antichymotrypsin and the IgG1 antibody trastuzumab (TZ). However, PNGase H⁺ provides broader specificity and greater tolerance to the disulfide-bond reducing agent TCEP, while PNGase A offers advantages in terms of commercial availability and purity. Overall, our findings demonstrate the unique features of PNGase H⁺ for improving conformational analysis of glycoproteins by HDX-MS, in particular, challenging glycoproteins containing both glycosylations and disulfide bonds.

Conformational Destabilization of Immunoglobulin G Increases the Low pH Binding Affinity with the Neonatal Fc Receptor

Crystallographic evidence suggests that the pH-dependent affinity of IgG molecules for the neonatal Fc receptor (FcRn) receptor primarily arises from salt bridges involving IgG histidine residues, resulting in moderate affinity at mildly acidic conditions. However, this view does not explain the diversity in affinity found in IgG variants, such as the YTE mutant (M252Y,S254T,T256E), which increases affinity to FcRn by up to 10×. Here we compare hydrogen exchange measurements at pH 7.0 and pH 5.5 with and without FcRn bound with surface plasmon resonance estimates of dissociation constants and FcRn affinity chromatography. The combination of experimental results demonstrates that differences between an IgG and its cognate YTE mutant vary with their pH-sensitive dynamics prior to binding FcRn. The conformational dynamics of these two molecules are nearly indistinguishable upon binding FcRn. We present evidence that pH-induced destabilization in the CH2/3 domain interface of IgG increases binding affinity by breaking intramolecular H-bonds and increases side-chain adaptability in sites that form intermolecular contacts with FcRn. Our results provide new insights into the mechanism of pH-dependent affinity in IgG-FcRn interactions and exemplify the important and often ignored role of intrinsic conformational dynamics in a protein ligand, to dictate affinity for biologically important receptors.

Differences in plasminogen activator inhibitor 1 in subcutaneous versus omental adipose tissue in non-obese and obese subjects

Human adipose tissue can produce plasminogen activator inhibitor-1 (PAI-1). It has been suggested that high levels of PAI-1 are of importance in enhanced cardiovascular disease observed among obese subjects, especially abdominally obese individuals. In the present study, we investigated the level of mRNA and production of PAI-1 in adipose tissue from two adipose tissue depots (omental vs. subcutaneous). Adipose tissue from both depots was obtained from obese (mean BMI, 46.9 kg/m 2) and non-obese (mean BMI, 23.9 kg/m 2) women. PAI-1 mRNA was measured both in fresh adipose tissue obtained immediately after surgery and after the adipose tissue (fragments) had been incubated for up to 72 h. In immediately frozen adipose tissue, PAI-1 mRNA expression was similar in omental and subcutaneous adipose tissue. No differences between obese and non-obese women were found. However, when adipose tissue fragments were cultured, PAI-1 mRNA and PAI-1 production were significantly higher in omental than in subcutaneous adipose tissue (p < 0.05). In the culture system, the production of PAI-1 in obese subjects was higher than in non-obese subjects in both subcutaneous (p < 0.05) and in omental adipose tissue (p = 0.19). In order to test whether these regional differences observed after incubation of the adipose tissue were due to differences in local accumulation of cytokines that may stimulate PAI-1 by a paracrine or autocrine manner, we investigated the expression of transforming growth factor beta1 (TGF-beta1) mRNA and tumor necrosis factor alpha (TNF-alpha) mRNA and protein. No differences between the two fat depots were found. In conclusion, no differences in PAI-1 expression between omental and subcutaneous adipose tissue were observed in biopsies frozen immediately after removal, but after incubation of adipose tissue (which somehow stimulates PAI-1 production), higher levels of PAI-1 were found in omental adipose tissue than in subcutaneous adipose tissue. Finally, PAI-1 production in adipose tissue from obese women was higher in non-obese women after incubation for 72 h.

How do anaesthesiologists treat malignant hyperthermia in a full-scale anaesthesia simulator?

BACKGROUND

Clinical malignant hyperthermia (MH) is rare and usually occurs unexpectedly. Prompt diagnosis and correct treatment is crucial for survival of the patient developing fulminant MH. The aims of the present study were to investigate whether anaesthesiologists could make a correct diagnosis of MH and to evaluate their treatment of fulminant MH in a simulator.

METHODS

Thirty-two teams (one anaesthesiologist/one nurse anaesthetist) were exposed to an event of clinical MH in a full-scale simulator. Their performance was videotaped for retrospective analysis of the treatment on the basis of the recommendations of the Danish Malignant Hyperthermia Register.

RESULTS

All 32 teams asked the surgeon to terminate the surgery as fast as possible, switched off the vaporiser and administered 100% oxygen. Although all intended to hyperventilate the patient, only 14 teams actually managed to perform the hyperventilation. Most problems were found in teams that switched to manual ventilation. All teams treated the patient with dantrolene, and symptomatic treatment was initiated by all even though some elements of the full treatment were lacking, possibly due to the limited time available.

CONCLUSION

All teams diagnosed MH in the simulator satisfactorily. The surprising negative finding was that more than half of the participants failed to hyperventilate the "patient" although they intended to do so. This investigation shows that the problem in these teams' treatment of MH was more a question of practical management of the resources than lack of theoretical knowledge.

Management of anaphylactic shock evaluated using a full-scale anaesthesia simulator

BACKGROUND

The diagnosis of an anaphylactic reaction during anaesthesia is not the first consideration for the anaesthetist and might be missed. The aim of this study was to describe anaesthetists' management of an anaphylactic reaction concerning diagnosing, treatment and application of anaesthesia crisis resource management (ACRM) in a full-scale anaesthesia simulator.

METHODS

Forty-two anaesthetists in teams of two attended training sessions with a critical incident of anaphylactic shock in a full-scale simulator. Trained observers from the study group evaluated the medical treatment according to a treatment sequence developed from the literature and graded the ACRM performance on a five-point scale where 1 is bad and 5 is best.

RESULTS

None of the teams made the correct diagnosis within 10 min and treatment according to the treatment sequence was not initiated. Only 6/21 teams considered the right diagnosis but first after hints from the instructor 15 min after the start of the incident. Evaluation of the use of the total ACRM concept (that is the use of all of the ACRM expressions seen in a total connection: called general impression) gave a median value of 2.0 with a range of (1-3).

CONCLUSION

Anaphylactic shock was difficult to diagnose and no structured plans were used for the treatment in the simulated incident in this study.

ResusSim 98--a PC advanced life support trainer

Advanced life support (ALS) requires several different skills and the recall of complex information. The personal computer is an ideal tool for the teaching of factual information. We have developed a computer programme that simulates a variety of cardiac arrest scenarios. Its aim is to communicate specialist knowledge to junior staff in a challenging and entertaining way. Each scenario has a real time ECG, clinical signs of the simulated patient, blood pressure, oxygen saturation and temperature. Arterial blood samples can be analysed and the medical record can be reviewed. Interventions available include defibrillation, intubation, fluid and drug therapy. Built-in variation means that repeating a scenario may lead to different patient behaviour. An important part of the programme is the intelligent debriefing of the user after each patient. Each action elicits a comment that is based upon the current European Resuscitation Council guidelines. This is then hyperlinked to an extensive help file that includes the text of the guidelines, diagrams, pictures and algorithms that aid the user in the learning of ALS skills in association with existing teaching programmes. ResusSim 98 runs under Windows 3.1, Windows 95/98 and Windows NT 4.0.

Treatment of ventricular fibrillation during anaesthesia in an anaesthesia simulator

BACKGROUND

To evaluate treatment of ventricular fibrillation (VF) occurring during anaesthesia and the use of a full-scale simulator, 80 anaesthetists in teams of two were attending a training session in the simulator Sophus.

METHODS

The sessions were recorded on videotape and reviewed with the anaesthetists afterwards. Time of treatment and the sequence were registered.

RESULTS

Onset time for VF was the starting point. Most of the subjects changed respiratory settings. Four teams did not change inspiratory oxygen and 17 teams did not turn off the vaporiser. Cardiac compression was initiated by all teams. DC-defibrillation was not used by two teams, with 38 of 40 teams defibrillating once, 37 twice and 29 teams three times. Adrenaline was administered by 30 of 40 teams.

CONCLUSION

There was very little consistency among the teams regarding treatment for VF according to accepted algorithms. An anaesthesia simulator could be a tool for training and it is a safe way of demonstrating for the anaesthetist that certain treatment algorithms and behaviour during critical incidents are the most effective.

The Sophus anaesthesia simulator v. 2.0. A Windows 95 control-center of a full-scale simulator

The Sophus group was founded in Denmark in 1992 with the aims of doing research into human error in anaesthesiology. Development of a simulation-environment was seen as one of the tools for research and training. This article describes the PC user interface of the SOPHUS anaesthesia simulator, SOPHUS v. 2.0 for Windows 95, and the script language, SASL v. 1.2. The script language provides possibilities of making scenarios, which develop in different directions according to the treatment of the patient by means of IF/THEN-statements, loops etc.

Post-operative nocturnal hypoxia in septoplasty: the value of nasal packing with airway tubes

Nasal obstruction influences respiration during sleep and post-operative nasal packing may cause nocturnal oxygen desaturation and obstructive sleep apnoea. In order to investigate the influence of nasal packing with airway tubes on post-operative hypoxia during sleep, the oxygen saturation was monitored perioperatively in 18 patients, undergoing septoplasty followed by nasal packing using Merocel packs with airway tubes. For the group as a whole, no significant perioperative change of either median minimal or median mean oxygen desaturation could be demonstrated. A similar, non-significant perioperative prolongation of the relative time of nocturnal oxygen desaturation, expressed as per cent of the total nocturnal observation time, was seen. The results indicate that nasal packing with airway tubes may prevent post-operative hypoxia during sleep, but further investigation of post-operative nocturnal hypoxia and nasal packs, is needed.

Impact of immediate and delayed myocardial scintigraphy on therapeutic decisions in suspected acute myocardial infarction

Early myocardial scintigraphic imaging has become technically feasible in patients admitted to hospital with suspected acute myocardial infarction. After prompt injection of 99mTc-sestamibi, subsequent scintigraphic imaging of perfused myocardium can be performed. During a 5-month period, 237 patients were admitted to the coronary care unit of a district hospital on suspicion of acute ischaemic syndrome, and injection of 99mTc-sestamibi for the performance of myocardial scintigraphy was carried out in 134 patients, on average 2 h after onset of symptoms. The investigation was repeated in 126 patients, on average 18 h after the injection. Three planar views were taken in the coronary care unit with a mobile gamma camera. The prevalence of acute myocardial infarction was 53%. The predictive value at the first scintigraphic imaging for a positive or negative test for myocardial infarction 54% and 56%, respectively. Even exclusion of patients with a previous infarction did not increase the diagnostic validity. The predictive value of a negative test, 77%, at the second scintigraphy was still insufficient to make immediate therapeutic decisions. Myocardial scintigraphy performed early, on suspicion of acute myocardial infarction, cannot therefore be used routinely as a diagnostic test prior to intervention in unselected patients because some 90% of this patient group have myocardial perfusion defects.

Dopamine, dobutamine, and dopexamine. A comparison of renal effects in unanesthetized human volunteers

BACKGROUND

Recently, dopexamine (DX), which acts via adrenergic beta 2 and dopaminergic DA1 receptors, has been introduced in the treatment of low cardiac output states. However, the renal effects of DX have not been compared to those produced by equipotent inotropic doses of dopamine (DA), which predominantly stimulates DA1 and DA2 receptors, and of dobutamine (DB), which stimulates beta 1 but not DA receptors. The current study tested the null hypothesis that, with equal increases in cardiac output, DX, DA, and DB would have similar effects on renal function.

METHODS

Each drug was given for 2 h on three different occasions to eight normal subjects in doses adjusted to produce a similar 30-35% increase in cardiac output. Effective renal plasma flow (ERPF) and glomerular filtration rate (GFR) were measured as renal clearances of 131I-hippuran and 99mTc-DTPA, respectively. Lithium clearance (CLi) was used as an index of proximal tubular outflow.

RESULTS

Doses of DA, DX, and DB were 2.90 +/- 0.19, 1.00 +/- 0.02, and 4.92 +/- 0.40 microgram.kg-1.min-1, respectively. Dopamine and DX increased ERPF by 23% and 10%, respectively, whereas ERPF remained unchanged during DB. The increase in ERPF was smaller during DX compared with DA. The GFR remained unchanged during DA and DB, but increased during DX (7%). The CLi increased by 35% and 30% during DA and DX, respectively, but was not changed by DB. Calculated absolute proximal reabsorption rate (APR = GFR--CLi) decreased by 13% during DA, but remained unchanged during DB and DX. Dopamine increased sodium clearance (CNa) by 103%, but the changes during DX and DB were not significant. Only DA decreased fractional distal reabsorption (FDRNa = 1--CNa/CLi).

CONCLUSIONS

The findings are consistent with a specific, renal-vasodilating effect of DA and DX. However, in the current doses, this effect of DX was of lesser magnitude compared with that of DA. Only DA significantly increased CNa, and the decreases in APR and FDRNa indicate that an effect on tubular reabsorption rate contributed to the natriuresis.

Perioperative monitoring with pulse oximetry and late postoperative cognitive dysfunction

In a randomized, blinded clinical study, we have used objective and subjective measures to determine if perioperative monitoring with pulse oximetry--by virtue of its potential to lessen hypoxaemia--would decrease late postoperative cognitive dysfunction. We investigated 736 adult patients undergoing elective procedures (other than cardiac, neurosurgical or for cancer) under regional or general anaesthesia, allocated randomly to undergo (group I) or not to undergo (group II) pulse oximetry monitoring in the operating theatre and recovery room. Cognitive function was evaluated using the Wechsler memory scale (WMS) and continuous reaction time (RT) test the day before surgery, and on the 7th day after operation or at discharge if that occurred before postoperative day 7. A questionnaire sent 6 weeks after surgery elicited patients' subjective perceptions regarding cognitive abilities. There were no significant differences between the two groups in either the total WMS score, the score for each WMS subtests or RT test. The questionnaire revealed that 7% in group I and 11% in group II believed cognitive abilities had decreased (ns). For the 40 patients whose WMS scores were 10 points less after than before operation, a follow-up study was undertaken 3 months after surgery. At that time, the median WMS score had returned to the preoperative value. We conclude that, for these 736 patients, subjective and objective measures did not indicate less postoperative cognitive impairment after perioperative monitoring with pulse oximetry.

Randomized evaluation of pulse oximetry in 20,802 patients: II. Perioperative events and postoperative complications

BACKGROUND

The authors describe the effect of pulse oximetry monitoring on the frequency of unanticipated perioperative events, changes in patient care, and the rate of postoperative complications in a prospective randomized study.

METHODS

The study included 20,802 surgical patients in Denmark randomly assigned to be monitored or not with pulse oximetry in the operating room (OR) and postanesthesia care unit (PACU).

RESULTS

During anesthesia and in the PACU, significantly more patients in the oximetry group had at least one respiratory event than did the control patients. This was the result of a 19-fold increase in the incidence of diagnosed hypoxemia in the oximetry group than in the control group in both the OR and PACU (P < 0.00001). In the OR, cardiovascular events were observed in a similar number of patients in both groups, except myocardial ischemia (as defined by angina or ST-segment depression), which was detected in 12 patients in the oximetry group and in 26 patients in the control group (P < 0.03). Several changes in PACU care were observed in association with the use of pulse oximetry. These included higher flow rate of supplemental oxygen (P < 0.00001), increased use of supplemental oxygen at discharge (P < 0.00001), and increased use of naloxone (P < 0.02). The rate of changes in patient care as a consequence of the oximetry monitoring increased as the American Society of Anesthesiologists physical status worsened (P < 0.00001). One or more postoperative complications occurred in 10% of the patients in the oximetry group and in 9.4% in the control group (difference not significant). The two groups did not differ significantly in cardiovascular, respiratory, neurologic, or infectious complications. The duration of hospital stay was a median of 5 days in both groups (difference not significant). An equal number of inhospital deaths were registered in the two groups. Questionnaires, completed by the anesthesiologists at the five participating departments, revealed that 18% of the anesthesiologists had experienced a situation in which a pulse oximeter helped to avoid a serious event or complication and that 80% of the anesthesiologists felt more secure when they used a pulse oximeter.

CONCLUSIONS

This study demonstrated that pulse oximetry can improve the anesthesiologist's ability to detect hypoxemia and related events in the OR and PACU and that the use of the oximeter was associated with a significant decrease in the rate of myocardial ischemia. Although monitoring with pulse oximetry prompted a number of changes in patient care, a reduction in the overall rate of postoperative complications was not observed.

Randomized evaluation of pulse oximetry in 20,802 patients: I. Design, demography, pulse oximetry failure rate, and overall complication rate

BACKGROUND

Although pulse oximetry is currently in widespread use, there are few data documenting improvement in patient outcome as a result of the use of oximetry. The authors describe the study design, patient demographic findings, data validation, pulse oximetry failure rate, and overall postoperative complication rates in the first large prospective randomized multicenter clinical trial on perioperative pulse oximetry monitoring.

METHODS

In five Danish hospitals, by random assignment, monitoring did or did not include pulse oximetry for patients 18 yr of age and older, whether scheduled for elective or emergency operations, or for regional or general anesthesia, except during cardiac and neurosurgical procedures. Operational definitions were established for perioperative events and postoperative complications. The data were collected preoperatively, during anesthesia, in the postanesthesia care unit, and until the day of discharge from the hospital or the seventh postoperative day.

RESULTS

Of 20,802 patients, 10,312 were assigned to the oximetry group and 10,490, to the control group. In general, the demographic data, patient factors, and anesthetic agents used were distributed evenly. A slight intergroup difference was found in the distribution of age, duration of surgery, some types of surgery, and some types of anesthesia. The total failure rate of the oximetry was 2.5%, but it increased to 7.2% in patients with American Society of Anesthesiologists physical status 4 (P < 0.00001). In 14.9% of the patients, one or more events occurred in the operating room and 13.5% in the postanesthesia care unit. The overall postoperative complication rate was 9.7%. The total rates of cardiovascular and respiratory complications were 2.78% and 3.50%, respectively. Within the first seven postoperative days, 0.47% of the patients died. Anesthesia was not thought to have been solely responsible for any death, but in 7 patients (1 per 3,365), it was a possible contributory factor.

CONCLUSIONS

Despite the finding of a few significant inter-group differences, the randomization was well balanced with a high validity of data. The overall postoperative complication rate was similar to that in other recent morbidity and mortality studies.

Hypoxaemia is reduced by pulse oximetry monitoring in the operating theatre and in the recovery room

To determine the impact of pulse oximeter monitoring on the incidence, severity and duration of hypoxaemia in the operating theatre (OT) and in the recovery room (RR), we investigated 200 patients in a randomized study. The extent of hypoxaemia in the OT was compared with that in the RR. Adult inpatients were allocated randomly to two groups: group I, pulse oximeter data and alarms "available"; group II, these data "unavailable" to the anaesthesia team and RR staff. Hypoxaemia was graded into four values of oxyhaemoglobin saturation (SpO2). The incidence of hypoxaemia was reduced significantly in group I in both OT and RR. In the OT, five patients in group II suffered SpO2 less than 76% compared with none in group I (P less than 0.02). In group II in the RR, seven patients suffered SpO2 less than 81%; three of these had SpO2 less than 76%. No patients in group I exhibited such small values of saturation. The smallest recorded SpO2 in the OT and the RR was significantly greater in group I. The cumulative duration of hypoxaemia was significantly less in group I in the RR, but not in the OT. The incidence and severity of hypoxaemia in the OT and in the RR were comparable, whereas the cumulative duration of hypoxaemia was significantly greater in the RR than in the OT. The occurrence of hypoxaemia in an individual patient in the OT significantly increased this patient's risk of suffering hypoxaemia in the RR. We conclude that the extent of hypoxaemia, especially in the RR, may be reduced significantly by pulse oximeter monitoring, but even with the information provided, some patients still develop hypoxaemia.

Myocardial perfusion at fatal infarction: location and size of scintigraphic defects

In a consecutive study of myocardial scintigraphy in acute ischemic syndrome, four patients had 99mTc-hexamibi injected intravenously before they developed fatal cardiogenic shock. Planar scintigraphy was performed after death. Slices of the hearts after autopsy were analyzed for scintigraphic and pathoanatomic abnormalities. Location of perfusion defects in planar views of the heart was in good agreement with the scintigraphied, sliced sections. The extent of infarction judged from inspection and formasan staining was much smaller (7%-40% and 6%-43% of the total slice area) than found at scintigraphy, where 83%-92% of the myocardium showed ischemia as defined by a 99mTc-hexamibi uptake below an arbitrary limit on half maximum uptake. Myocardial hypoperfusion might thus aggravate the functional impairment at myocardial infarction and lead to cardiogenic shock.

Nasal packing and nocturnal oxygen desaturation

Nasal obstruction influences respiration during sleep, and nasal packing may be the cause of obstructive sleep apnoea. In order to investigate this phenomenon, perioperative nocturnal oxygen saturation was monitored for 3 nights with continuous, non-invasive pulse oximetry in 12 patients who had total nasal packs after septoplasty. Significant extension of nocturnal accumulated time of oxygen saturation less than 90% was demonstrated both during the first and second postoperative nights. The clinical significance of these results is as yet unknown, but the use of partial nasal packing in association with septoplasty is advocated and further investigations on nocturnal oxygen saturation are called for.

[Laparoscopic cholecystectomy. The first 45 operations]

During a period of 13 weeks, 45 patients with symptom-producing gall bladder stones (attacks of gall stone colic n = 39 (87%); acute cholecystitis n = 6 (13%)), corresponding to approximately 85% of the total number of gall bladder stone patients during the period were selected for laparoscopic cholecystectomy. Two patients had previously undergone upper abdominal operations and had adhesions and one patient suffered from cirrhosis of the liver with portal hypertension. It proved necessary to convert five of the laparoscopic cholecystectomies to open cholecystectomies (11%) on account of technical difficulties (severe acute changes due to cholecystitis (n = 3), indeterminable anatomical conditions (n = 1) and one case of liver metastases (n = 1)). The median duration of operation was 90 minutes with a range from 30 to 360 minutes. Peroperative cholangiography was not undertaken routinely. No cases of forgotten stones in the common bile duct occurred. No deaths occurred and, in all, three slight complications occurred (7%): two patients had haematoma in the abdominal wall and one patient minimal leakage of bile from the stump of the gall bladder on account of insufficient ligation of the cystic duct. This patient was treated with an endoscopically placed drain in the common bile duct for two weeks, after which she was well. No lesions of the common bile duct occurred. None of the complications required laparotomy. The median duration of hospitalization was 24 hours with a range from one to 14 days. All of the patients were at work or could manage their usual activities after 14 days. The median duration of sick leave was seven days.(ABSTRACT TRUNCATED AT 250 WORDS)

Episodic nocturnal hypoxia and nasal packs

Nasal obstruction influences respiration during sleep and nasal packs may cause obstructive sleep apnoea. In order to investigate this, the perioperative oxygen saturation was monitored for 3 nights with continuous pulse oximetry in 12 patients, who had bilateral nasal packs after septoplasty. A significant increase in the number of nocturnal episodes of hypoxia and a significant prolongation of the mean duration of the individual hypoxic periods were demonstrated during the first and the second post-operative nights. The clinical significance of these results is as yet unknown, but the use of partial nasal packing in septoplasty is advocated. Further investigations of nocturnal oxygen desaturation and design of nasal packs, securing the post-operative nasal airway, are needed.

Influence of a single dose of indomethacin on some biochemical changes and postoperative intestinal paralysis following minor surgery. A prospective randomized double-blind study

The influence of a single dose of indomethacin on the surgical stress response was investigated in a double-blind study including 43 patients scheduled for elective operation of inguinal hernia. Indomethacin or placebo was administered rectally 1 h before the start of operation. All patients had a standardized general anaesthetic. Blood samples for leucocyte count, sedimentation rate, iron and haemoglobin, and measurements of body temperature were taken preoperatively and on the day after surgery. Blood samples for glucose were taken preoperatively, and 4, 8 and 24 h after skin incision. In both groups a significant increase in leucocyte count and sedimentation rate as well as a decrease in serum iron were found, but there was no difference between the groups. Plasma glucose increased from 4 to 8 h after skin incision in the indomethacin group, but not in the placebo group. The postoperative need for methadon, the time needed to regain normal intestinal function and the hospital stay were the same in the two groups, and body temperature showed no change. These findings indicate that a single dose of indomethacin given preoperatively increased plasma glucose but had no effect on the other parameters studied.

Abnormal duodenal loop in patients with irritable bowel syndrome

The frequency of an abnormal duodenal loop (AD) was investigated in 36 patients with irritable bowel syndrome (IBS) and in a sex- and age-matched control group of patients with Crohn's disease. The frequency was significantly higher in the patients with IBS than in the control group (41% versus 18%; p less than 0.02). Among IBS patients with AD, the frequency of food-provoked pain was higher than in IBS patients with a normal duodenum (65% versus 21%; p less than 0.01). We conclude that AD may be one of the reasons for complaints in IBS.

Serum lipoprotein profiles of young atherosclerosis-susceptible White Carneau and atherosclerosis-resistant Show Racer pigeons

1. Newly-hatched atherosclerosis-susceptible White Carneau and atherosclerosis-resistant Show Racer pigeons (Columba livia) had significantly lower (P less than 0.01) alpha/beta serum lipoprotein ratios than 6-week, 3-month, or 6-month old pigeons of the corresponding breed, as determined by densitometric analysis of polyacrylamide disc gel electrophoretic profiles. 2. Differences in alpha/beta serum lipoprotein ratios were not observed between the two breeds at any age studied.