Supplementary cleaning does not remove protein deposits from re-usable laryngeal mask devices

PURPOSE: To test the hypothesis that supplementary cleaning facilitates removal of protein deposits from the laryngeal mask airway (LMA). METHODS: Twenty previously used Classic) and Flexible LMAs were hand washed, machine washed, dried, autoclaved and then randomly allocated into four groups for supplementary cleaning. In Group A, the dorsal surface was immersed in water and the surface scrubbed with a high-speed rotating brush. In Group B, the dorsal surface was immersed in a plaque removing solution. In Group C, the dorsal surface was immersed in a protein removing solution. In Group D (controls), the dorsal surface was immersed in water. Before and after supplementary cleaning the LMAs were immersed in a protein staining solution, rinsed and a high-resolution digital image taken of the dorsal surface. The location and severity of staining were scored by two observers blinded to group assignment. RESULTS: Staining was similar before and after supplementary cleaning for all groups. Mild, moderate and severe staining occurred in 31%, 7% and 2% of zones respectively; 60% were unstained. Staining was less common on the cuff than on the backplate and distal tube (both: P < 0.00001). Staining was less common on the backplate than on the distal tube (P = 0.001). Staining was always present on the mid-portion of the backplate or distal tube. CONCLUSION: Supplementary cleaning using a rotating brush, plaque or protein removing solution does not facilitate removal of protein deposits from re-usable LMAs; however, the infectious risk associated with the protein deposits remains to be determined.     

The effect of high concentration potassium permanganate on protein contamination from metallic and synthetic rubber airway equipment

We tested the hypothesis that supplementary cleaning using potassium permanganate 8 mg.l(-1) eliminates protein deposits from the reusable metallic and synthetic rubber airway equipment. Twenty Macintosh laryngoscope blades (surgical steel), 20 pairs of Magill's forceps (surgical steel) and 20 Guedel airways (synthetic rubber) were allocated to two groups for supplementary cleaning. In group A, the device was immersed in potassium permanganate 8 mg.l(-1). In group B (controls), the device was immersed in sterile water. The devices were then immersed in a protein staining solution, rinsed and the severity of staining was scored. In addition, the devices were inspected for tissue and then tested for occult blood. Protein contamination was lower in the potassium permanganate group for all devices (each device: p < 0.0001). There was no staining detected in the permanganate group. In the permanganate group, dried tissue was detected in the teeth of one pair of forceps, which was not detected following supplementary cleaning. Additionally, occult blood was detected on two pairs of forceps and a laryngoscope blade, which was not detected following supplementary cleaning. In the control group, no tissue was detected but one pair of forceps and two laryngoscope blades tested positive for occult blood before and after supplementary cleaning. We conclude that supplementary cleaning using potassium permanganate 8 mg.l(-1) eliminates protein deposits from re-usable metallic and synthetic rubber airway equipment.     

Routine cleaning and autoclaving does not remove protein deposits from reusable laryngeal mask devices

We tested the hypothesis that routine cleaning and autoclaving does not remove protein deposits from reusable laryngeal mask airways (LMAs). All previously used classic and flexible LMAs from a single hospital were tested. Each LMA was hand-washed in an enzymatic solution for 3 min, machine-washed with a disinfectant for 14 min at up to 85 degrees C; dried for 30 min at 75 degrees C, packaged in porous film, and autoclaved for 4 min at 134 degrees C. Protein deposits were detected by immersion in a 1.2% erythrosin B solution, which stains for proteins present on surfaces. The outer surface, inner surface, and edges of the cuff, and the outer and inner surface of the airway tube were examined for the uptake of stain. The severity of staining was scored according to the percentage of surface area stained: nil, mild (>0%-20%), moderate (>20%-80%), and severe (>80%-100%). Fifty-nine LMAs were collected (16 classic and 43 flexible). Staining was detected on 15 (94%) classic LMAs and 39 (91%) flexible LMAs. All staining was graded as mild. Staining was less common on the inner surface than the outer surface or edges for both devices (all P < 0.004). Staining was less common with the airway tube than any location on the cuff (all P < 0.02). Two unused LMAs used as controls were without staining. We conclude that routine cleaning and autoclaving does not remove protein material from reusable LMAs. IMPLICATIONS: Routine cleaning and autoclaving does not remove protein material from reusable laryngeal mask airway devices.     

High concentration potassium permanganate eliminates protein and particle contamination of the reusable Classic laryngeal mask airway

In this three-stage study, we test the hypothesis that supplementary cleaning with potassium permanganate > or =4 mg.l(-1) eliminates protein and particle contamination from the reusable Classic laryngeal mask airway. The first stage involved supplementary cleaning of 70 1 x 1 cm segments from deliberately contaminated laryngeal mask airways using potassium permanganate at 0, 2, 4, 8, 16, 32 and 64 mg.l(-1) and testing for protein staining. This showed that the lowest concentration required to eliminate protein contamination was 8 mg.l(-1). The second stage involved supplementary cleaning of 50 used laryngeal mask airways with either potassium permanganate 8 mg.l(-1) or saline and testing for protein staining. This showed that protein contamination was lower in the potassium permanganate group (p < 0.00001): all laryngeal mask airways in the control group and none in the potassium permanganate group were contaminated. The third stage involved scanning electron microscopic examination of 1 x 1 cm segments from three laryngeal mask airways used in the control group, three from the potassium permanganate group, plus three brand new laryngeal mask airways. The mean density of > or =1 mum surface particles was lower in the potassium permanganate 8 mg.l(-1) than the control group (21 vs. 121 .cm(-2), p < 0.0001) and was similar to brand new laryngeal mask airways (24 .cm(-2)). We conclude that supplementary cleaning with potassium permanganate 8 mg.l(-1) eliminates protein deposits from reusable laryngeal mask airways and reduces particle contamination to similar levels to brand new laryngeal mask airways.     

Repeat autoclaving does not remove protein deposits from the classic laryngeal mask airway

INTRODUCTION: We tested the hypothesis that repeated autoclaving removes protein deposits from the classic laryngeal mask airway (LMA). METHODS: Twenty previously used LMAs were hand washed, machine washed, dried, autoclaved and randomly allocated into four equal-sized groups for repeat autoclaving on 0 (control), 1, 2 and 3 occasions. After the final autoclave cycle, the LMAs were immersed in a protein-staining solution, rinsed, dried and a high-resolution digital image taken of the dorsal and ventral surfaces. The severity of staining was scored by two blinded observers. RESULTS: All LMAs were stained. There was no reduction in staining with repeat autoclaving. CONCLUSIONS: Repeat autoclaving does not remove protein deposits from the LMA.     

Residual protein contamination of ProSeal laryngeal mask airways after two washing protocols

The risk of prion protein cross-infection has focussed attention on the potential hazards of protein contamination of re-usable medical devices. This study determined the frequency of protein contamination of ProSeal laryngeal mask airways (PLMA) after two cleaning procedures and tested the hypothesis that the combination of hand- and machine-washing removes protein contamination more effectively than hand-washing alone. After clinical use fifty-four PLMAs were randomly allocated to be washed by hand or by hand then machine. All PLMAs were then autoclaved at 134 degrees C for 4 minutes. After processing, each PLMA was immersed in a 1.2% solution of erythrosin B and examined for uptake of stain. The site (outer surface, bowl and edges of the cuff airway and drain tube, finger strap) and severity (nil/mild/moderate/severe) of staining was scored by a blinded observer. There were no differences in the site or severity of staining between the two cleaning procedures. Staining was detected on 89% of PLMAs that were hand-washed and 78% of PLMAs that were hand-, then machine-washed (P=0.27). When staining occurred, it was mild in 98%, moderate in 2% and was never severe. Staining was more frequent on the edge than at any other location (all comparisons: P < or = 0.01). The strap never had any staining. We conclude that residual contamination of PLMAs with protein deposits is common even when machine-washing is used to augment hand-washing before autoclaving. The infection risk associated with these deposits remains to be determined.     

Eliminating protein from reusable laryngeal mask airways. A study comparing routinely cleaned masks with three alternative cleaning methods

Laryngeal mask airways (LMAs) have the potential to act as a vector for the transmission of prion diseases. This study was undertaken to define the problem of protein contamination and to investigate three alternative cleaning methods. Forty-eight LMAs were allocated to one of four groups, stained with erythrosin and given a total stain score and a grid stain score in order to determine the degree of protein contamination. Eighteen randomly selected LMAs that had been routinely cleaned and sterilised (group 1) were compared with 12 LMAs that had been washed and scrubbed with the benefit of prior staining (group 2), 13 that had been washed and scrubbed without any visual guide (group 3) and 13 that had been cleaned using a Biosonic ultrasonic cleaning system (group 4). The results show that none of the cleaning methods achieved optimal results, as all methods left proteinaceous material on some masks. The study showed that: (i) staining as a guide to cleaning does not lead to more effective removal of proteinaceous material; (ii) systematic cleaning and scrubbing does lead to more effective removal of proteinaceous material from surfaces other than the grid area; and (iii) ultrasonic cleaning was more effective than other methods of cleaning for the removal of proteinaceous material from those areas of the mask most inaccessible, such as the grid.     

Changes in the intracuff pressure of the laryngeal masks airway caused by repeated use

PURPOSE: To observe the changes in permeability and elasticity in the cuff of the laryngeal mask airway (LMA) caused by repeated use. METHODS: In vitro use was simulated on six # 4 LMAs on 140 occasions. Ambient air was insufflated into the cuff until a value of 200 mmHg intracuff pressure (ICP) was reached, and this was maintained for 50 min. After each simulation, the LMA was sterilized at 121 degrees C for 20 min. After every 20 simulations insufflation of 40 ml air was carried out to determine the maximum value of ICP (initial ICP), and after three hours, spontaneous deflation (final ICP) was measured. The values of initial and final ICPs throughout the eight tests were attributed to the elastance and the permeability of the cuff respectively. At the end of the study the thickness of the wall of the cuffs was measured using an optical microscope. RESULTS: The initial ICP with the new LMA (first test) was of 191 +/- 4.4 mmHg. This value increased from the fifth test onwards until the end of the study. The value of the final ICP in the first test was 111 +/- 3 mmHg and decreased with successive sterilizations. Between 80 and 100 simulations, initial ICP increased from 186.5 +/- 2.9 to 191.7 +/- 2.3 (P = 0.006). The thickness of the wall (694 +/- 17 microns) was inversely related with the elasticity and the permeability of the cuff. CONCLUSIONS: The "safe" life-span of the cuff of the LMAs, measured by the initial modifications of the physical properties of the silicone during simulations, was estimated to be 80-100 uses and was related to the thickness of its wall.     

The ProSeal has a shorter life-span than the Classic laryngeal mask airway

We tested the hypothesis that the life-span of the ProSeal laryngeal mask airway (LMA) is shorter than the Classic LMA. We also compared residual cuff volumes and changes in elastance and permeability with use. Six new size 4 ProSeal LMAs and 6 new size 4 Classic LMAs were tested. Each LMA underwent a simulated clinical use cycle until it failed the pre-use check tests. The simulated clinical use cycle comprised: i) inflating the cuff to the maximum recommended volume for 1 h; ii) immersion in an enzymatic solution for 3 min; iii) washing the external and internal surfaces; iv) automatic washing for 14 min (< or =85 degrees C); v) drying for 30 min (< or =75 degrees C); and vi) autoclaving at 134 degrees C for 4 min at 206 kPa. Before the first cycle and every 10 subsequent cycles, the cuff was inflated with 40 mL air and the intracuff pressure was measured immediately and 3 h later. The initial intracuff pressure was taken to be an inverse measure of the elastance or resistance to deformation, and the intracuff pressure change were taken as a measure of the permeability. The residual cuff volume was determined for 10 Classic and 10 ProSeal size 4 LMAs using a gas dilution technique. The mean +/- sd (range) longevity for the ProSeal LMA and Classic LMA was 82 +/- 23 (45-109) uses and 133 +/- 35 (76-176) uses, respectively. The ProSeal LMA has a shorter life-span than the Classic LMA (P = 0.01). For the ProSeal LMA, there was no change in elastance or permeability with use. For the Classic LMA, there was a decrease in elastance (P < 0.0001) and an increase in permeability (P < 0.0001) with use. The residual cuff volume was higher for the ProSeal LMA (2.6 +/- 1.3 mL versus 1.5 +/- 0.9, P = 0.04). We conclude that the life-span of the ProSeal LMA is shorter than the Classic LMA, but both exceed the manufacturer's recommendations of 40 uses. We recommend that reusable LMA devices be discarded when they fail the pre-use check tests, rather than after a specific number of uses.     

Protein contamination of the Laryngeal Mask Airway and its relationship to re-use

The Laryngeal Mask Airway is a reusable device for maintaining the patency of a patient's airway during general anaesthesia. The device can be reused after it has been cleaned and sterilized. Protein contamination of medical instruments is a concern and has been found to occur despite standard sterilization techniques. The reason for the concern relates to the possibility of the transmission of prions and the risk of developing a neurodegenerative disorder such as Creutzveldt-Jacob disease. The purpose of this study was to quantify the amount of protein contamination that occurs, and to relate this to the number of times the Laryngeal Mask Airway has been used. Fifty previously used Classic Laryngeal Masks were collected after routine sterilization and packaging. The devices were immersed in protein detecting stain and then visual inspection performed to assess the degree and distribution of the staining. The researcher was blinded to the number of times the Laryngeal Mask Airway had been used. Linear regression analysis of the degrees of staining of the airway revealed that protein contamination occurs after the first use of the device and this increases with each subsequent use. This finding highlights the concern that the currently used cleaning and sterilization methods do not prevent the accumulation of proteinaceous material on Laryngeal Mask Airways. Consideration should be given to the search for more efficient cleaning and sterilization techniques or the use of disposable devices.     

Potassium-verapamil cardioplegia for myocardial protection: an experimental evaluation through preservation and transplantation

The efficacy of potassium-verapamil cardioplegia for myocardial protection was studied using the canine heart preservation and transplantation system. Coronary vascular washout of the grafts was performed via the aortic root both in Group I (n=8) with 4 degrees C high potassium cardioplegic solution and in Group II (n=8) with 4 degrees C high potassium and 1 mg/L verapamil solution. The heart were immersed into the same solution as used for washout and stored at 4 degrees C for 6 hours, without oxygenation and perfusion. The grafts were transplanted orthotopically under conditions of cardiopulmonary (CP) bypass. Adequate hemodynamics without the support of CP bypass was obtained in all the grafts of Group II during a 2-hour observation period. In contrast, only five out of eight grafts in Group I were able to support the recipient circulation. Contraction bands were more prominently and frequently observed in the histology in Group I. Thus, the combination of coronary vascular washout with cold potassium-verapamil cardioplegia and storage at 4 degrees C with the same solution seems to be effective for myocardial protection of the canine heart in cases of orthotopic transplantation.     

Functional and metabolic effects of nicardipine on ischemic rat hearts with multidose potassium cardioplegia

This study was undertaken to assess the effect of a calcium antagonist, nicardipine (N), added in a cardioplegic solution on the ischemic myocardium. Isolated rat hearts were perfused with oxygenated Krebs Ringer Bicarbonate (KRB) solution by Langendorff's perfusion method and were subjected to 2 hours of ischemic arrest at 30 degrees C with multidose cardioplegia (every 30 min, for 5 min) and a subsequent 60 min of reperfusion. HR, LVP, coronary flow and oxygen tension of coronary effluent were monitored. Oxygen saturation of intracellular myoglobin and redox state of mitochondrial cytochrome aa3 in the myocardial cell were continuously measured throughout studies by a spectrophotometer. Oxygenated crystalloid cardioplegic solution (KRB) containing 25 mM of potassium was used. 40 rats were divided into 4 groups (10 rats each) according to the concentration of N (none, 0.5, 1 and 2 mg/L) in fully oxygenated potassium cardioplegic solution (PO2: 601 +/- 31 mmHg). The percent recovery of pressure-rate product after reperfusion was compared in each group and the optimal concentration of N was found to be 1 mg per liter of cardioplegic solution. No significant difference was found between Group Ia (N = 0 mg/L) and Group Ib (N = 1 mg/L) in metabolic or hemodynamic recovery after reperfusion. In other experiments, 40 rats in Group IIa (N = 0 mg/L, n = 20) and Group IIb (N = 1 mg/L, n = 20) received 10 ml of poorly oxygenated cardioplegic solution (PO2: 215 +/- 10 mmHg) on each reinfusion followed by a 25 min interval of ischemic arrest. The index of oxygen utilization, MVO2/pressure-rate product after reperfusion was significantly lower in Group IIb than in Group IIa (p less than 0.05). The results show that the addition of N (1 mg/L) to the cardioplegic solution preserved a more aerobic state (higher intracellular oxygen level) in the myocardium by further suppressing myocardial oxygen demand during the ischemic period which resulted in better myocardial protection. Therefore, it is concluded that the addition of N to the cardioplegic solution enhances myocardial preservation during myocardial ischemia.     

Arterial reconstruction in rat liver transplantation – development of a new tubing technique of the common hepatic artery

Arterialization of liver transplants in rats results in an improved function compared with grafts without artery. Here we compared techniques of reconstruction, focusing on thrombosis, duration of procedure and severity of pancreas damage after dissecting the gastroduodenal artery (GDA). Group 1: tube was inserted into the proper hepatic artery (PHA) of donor and recipient. Group 2: tube was placed into common hepatic artery (CHA) of donor and recipient. Group 3: cuff was placed over the CHA of the recipient and the graft's artery was slipped over the cuff. Tubing in PHA leads to a thrombosis rate of 40% after 6 months. Arteries remain perfused by using a cuff or tube in CHA. Dissection of the GDA does not influence pancreatic perfusion. Reconstruction took 19 s using the large tube, about 30 s for the tube into PHA and 1 min for the cuff. The method of choice is using a tube for the CHA.     

Cuff filling volumes and pressures in pediatric laryngeal mask airways

BACKGROUND: Hyperinflation of LMA cuffs carries the risk of airway morbidity by exerting pressure on laryngeal and pharyngeal structures. Cuff hyperinflation in LMAs can result from nitrous oxide diffusion into the LMA cuff and from deliberate manual cuff inflation. METHODS: In an in vitro set up, maximum recommended cuff filling volumes for size 1, 1.5, 2, 2.5, 3 disposable LMAs from different manufacturers [SoftSeal LMA (Portex); Unique LMA (Intavent); Marshall LAD, LaryngoSeal (Tyco)] and reusable Classic and ProSeal LMAs (Intavent) were inflated into completely emptied LMA-cuffs and into LMA-cuffs at resting volume. Cuff pressures were measured using a cuff manometer. Experiments were performed eight times using two exemplars of each brand/size. RESULTS: Maximum recommended cuff filling volumes for pediatric LMAs resulted in hyperinflation (cuff pressure >60 cmH(2)O) in almost all LMAs, starting with emptied cuff. Starting from resting cuff volume, the maximum recommended inflation volume resulted in cuff pressures of >120 cmH(2)O in all LMAs and sizes except in the ProSeal size 3 (101 +/- 1 cmH(2)O). CONCLUSIONS: Since the volume of air which is effectively required depends on several factors and varies between patients, the cuffs should be inflated only with the minimum volume of air required to form an effective seal with the respiratory and gastrointestinal tracts and the cuff pressure should be controlled.     

Laryngeal mask airways – to inflate or to deflate after insertion?

Background: Hyperinflation of the laryngeal mask airway (LMA) cuff is known to be a risk factor for airway morbidity and increased leakage around the LMA. While the manufacturers’ recommendation is to inflate the cuff with the maximum recommended volumes and/or to adjust the cuff pressure to <60 cmH₂O, cuff pressures below 40 cmH₂O have been shown to be associated with a minimal rate of sore throat and minimal leakage. However, it remains to be determined whether inflation or deflation is needed to achieve favorable pressures. Therefore, we assessed the need for cuff‐volume adjustment following insertion of the LMA unchanged straight from the sterile packaging in a prospective audit. Methods: One thousand children (0–16 years) undergoing elective surgery were consecutively included in this quality of care audit. After taking the LMA from its sterile packaging, the LMA cuff was emptied and the amount of air recorded. Then, the same amount of air was returned into the LMA, the LMA was inserted into the patient, and the cuff pressure was measured using a calibrated cuff manometer. Results: Following insertion of the LMA (without further inflation or deflation of the cuff), 20.5% of children had cuff pressures ≥60 cmH₂, while 55.7% had LMA cuff pressures <40 cmH₂O. Cuff pressures were also significantly higher in size 1 LMAs (66.6% had cuff pressures ≥60 cmH₂O and 2% <40 cmH₂O) compared with all other sizes (P < 0.05). Furthermore, cuff pressures in LMAs with a poly vinyl chloride (PVC) surface were higher compared to LMAs with a silicone surface (65.2%≥60 cmH₂O and 9.3% <40 cmH₂O vs 9%≥60 cmH₂O and 67.6% <40 cmH₂O, respectively). Conclusions: This study demonstrates that LMAs, particularly when using small‐sized LMAs or LMAs with a more rigid PVC surface, need to be deflated following insertion of the device rather than inflated to avoid cuff hyperinflation. Hence, cuff pressures should be measured routinely using a manometer to minimize potential pressure‐related airway complications.     

A comparison of postoperative sore throat after use of laryngeal mask airway and tracheal tube

Purpose We compared the degree of postoperative sore throat (PST) after use of a laryngeal mask airway (LMA; by two insertion techniques) and a tracheal tube (TT) in adult patients.Methods Eighty-six adult patients undergoing surgery of an extremity were randomized into three groups. The LMAs (size 4 for men, 3 for women) and TTs were lubricated with 2% lidocaine gel. After the induction of anesthesia, an LMA with the cuff deflated was inserted and then the cuff was inflated in group A, an LMA with the cuff inflated was inserted in group B, and the trachea was intubated using vecuronium in group C; staff anesthesiologists performed all these methods. LMA cuffs were inflated with the maximum recommended volume of air. TT cuffs were inflated with the minimum volume of air without gas leakage at 20cmH₂O pressure. The mode of ventilation depended on the individual anesthesiologists. Blood traces on the devices were examined after their removal. PST was rated immediately after anesthesia and on the first postoperative day, using a three-point score and a 100-mm visual analog scale, respectively.Results Most of the patients receiving an LMA breathed spontaneously and those receiving a TT underwent controlled ventilation. The ratio of positive blood traces on devices, as well as the degree of PST immediately after anesthesia, was similar in the three groups; however, on the first postoperative day, the severity of PST was greater in the LMA groups than in the TT group (P = 0.016). The severity of PST was similar with the two LMA insertion techniques.Conclusion In the conditions of our study, LMAs inserted with the cuff either fully inflated or deflated worsened PST compared with TTs.This work was presented in part at the 49th annual meeting of the Japanese Society of Anesthesiologists, Fukuoka, Japan, April 18–20, 2002     

Reusable Laryngeal Mask Airways can be used more than 40 times

STUDY OBJECTIVE: To compare the mechanical properties of classic, reusable Laryngeal Mask Airways (LMAs) that have been used more than 100 times with one unused LMA. DESIGN: Laboratory testing of devices used clinically. SETTING: Metropolitan university hospital. MEASUREMENTS: Cuff and tube specimens from LMAs that had been used at least 100 times were tested for elongation, tensile strength, stiffness, and tear strength using standard American Society of Testing and Materials protocols. Samples from an unused LMA were analyzed in the same manner for comparison. MAIN RESULTS: Tensile strength of the cuff samples was found to increase by approximately 25%. There was an increase in cuff stiffness and decreased tear strength similar to the manufacturer-reported trends. Cuff elongation decreased by 30%. Results for the LMA tube differed depending on whether the samples were taken in the machine direction or transverse direction. Tensile strength decreased by 30% in machine direction and, on average, very little in transverse direction. CONCLUSIONS: The material in reusable classic LMAs does not lose its strength after 100 uses to the extent that its manufacturer claims. At least 100 uses may be considered safe for these devices.     

Adenosine cardioplegia. Adenosine versus potassium cardioplegia: effects on cardiac arrest and postischemic recovery in the isolated rat heart

Adenosine is a potential cardioplegic agent by virtue of its specific inhibitory properties on nodal tissue. We tested the hypothesis that adenosine could be more effective than potassium in inducing rapid cardiac arrest and enhancing postischemic hemodynamic recovery. Isolated rat hearts were perfused with Krebs-Henseleit buffer or cardioplegic solutions to determine the time to cardiac arrest and the high-energy phosphate levels at the end of cardioplegia. Cardioplegic solutions contained adenosine 10 mmol/L, potassium 20 mmol/L, or adenosine 10 mmol/L + potassium 20 mmol/L and were infused at a rate of 2 ml/min for 3 minutes at 10 degrees C. Both time taken and total number of beats to cardiac arrest during 3 minutes of cardioplegia were reduced by adenosine 10 mmol/L and adenosine 10 mmol/L + potassium 20 mmol/L when compared with potassium 20 mmol/L alone (p less than 0.001). Tissue phosphocreatine was conserved by adenosine 10 mmol/L when compared with potassium 20 mmol/L, being 7.1 +/- 0.2 (mumol/gm wet weight (n = 7) and 6.0 +/- 0.3 mumol/gm wet weight (n = 5), respectively (p less than 0.05). Postischemic hemodynamic recovery was tested in isolated working rat hearts. After initial cardiac arrest, the cardioplegic solution was removed with Krebs-Henseleit buffer at a rate of 2 ml/min for 3 minutes at 10 degrees C, and thereafter total ischemia was maintained for 30 or 90 minutes at 10 degrees C before reperfusion. Adenosine 10 mmol/L enhanced recovery of aortic output when compared with potassium 20 mmol/L or adenosine 10 mmol/L + potassium 20 mmol/L, the percentage recovery after 30 minutes of ischemia being 103.0% +/- 4.4% (n = 6), 89.0% +/- 5.8% (n = 6), and 86.6% +/- 4.3% (n = 6), respectively (p less than 0.05 for comparison between adenosine 10 mmol/L and potassium 20 mmol/L). Thus adenosine cardioplegia caused rapid cardiac arrest and improved postischemic recovery when compared with potassium cardioplegia and with a combination of these two agents.     

Amyloid deposition in systemic organs in long-term hemodialysis patients

It has not been yet elucidated whether, in long-term hemodialysis patients, amyloid deposition in the transverse carpal ligament (TCL) is a symptom of systemic amyloidosis or a localized one. In 2 patients amyloid deposition was noted in the TCL which had been resected at operation, and we observed amyloid deposits also in other organs at autopsy after their deaths. In the two patients, no diseases resulting in secondary amyloidosis were observed. The unlabeled antibody peroxidase-antiperoxidase method (PAP method) served to reveal the deposits of beta 2-microglobulin (beta 2M) in the TCL and other organs comparable to the Congo red positive area. And the Congo red staining for the amyloid protein after potassium permanganate treatment was preserved. According to these results, the carpal tunnel syndrome (CTS) in long-term hemodialysis was considered as a symptom of systemic amyloidosis. Amyloid was deposited mainly in the vessel walls and the deposition was not circumferential but segmental.     

Haemodynamic consequences and uterine contractions following 0.5 or 1.0 litre crystalloid infusion before obstetric epidural analgesia

Purpose

The efficacy of infusion of 0.5 L and 1.0 L Ringer’s lactate (LR) to prevent hypotension during induction of obstetric analgesia was studied. The effect of the different fluid boluses on fetal heart rate (FHR) and frequency of uterine contractions were also determined.

Methods

Ninety-two ASA 1–2 parturients were randomized to receive 0.5 L (Group 1) and 1.0 L (Group 2) LR immediately before incremental epidural injections with lidocaine to achieve T₁₀ sensory block. Systolic blood pressure (SBP) was measured with an automated BP cuff every two minutes for 30 min after infusion of fluid bolus. Fetal heart rate monitoring and tocometry were used continuously. The number of uterine contractions were recorded 30 min before and 60 min after iv bolus.

Results

The SBP decreased in both groups, but there was no difference between groups in mean SBP or maternal heart rate. The incidence of hypotension (SBP < 90 mmHg or decrease of 20%) was 4% in both groups. The FHR record of a patient in Group 1 showed a single late deceleration, and a decrease in beat-to-beat variability occured in one patient in Group 2. A decrease in the frequency of uterine contractions of two or more contractions per 30 min was noted more frequently in Group 2 (P < 0.05). The duration of iv bolus was longer in Group 2 than Group 1 (18.8 ± 4.3 min vs 12.3 ± 4.5 min, P < 0.01).

Conclusion

Administration of 1.0 L LR iv does not provide added protection against maternal hypotension, and is associated with delay in providing pain relief and a risk of decreasing uterine contraction frequency.