Correction to: Cardiopulmonary exercise testing (CPET) in the United Kingdom-a national survey of the structure, conduct, interpretation and funding.

[This corrects the article DOI: 10.1186/s13741-017-0082-3.].

Cardiopulmonary exercise testing (CPET) in the United Kingdom-a national survey of the structure, conduct, interpretation and funding.

BACKGROUND: Cardiopulmonary exercise testing (CPET) is an exercise stress test with concomitant expired gas analysis that provides an objective, non-invasive measure of functional capacity under stress. CPET-derived variables predict postoperative morbidity and mortality after major abdominal and thoracic surgery. Two previous surveys have reported increasing utilisation of CPET preoperatively in England. We aimed to evaluate current CPET practice in the UK, to identify who performs CPET, how it is performed, how the data generated are used and the funding models. METHODS: All anaesthetic departments in trusts with adult elective surgery in the UK were contacted by telephone to obtain contacts for their pre-assessment and CPET service leads. An online survey was sent to all leads between November 2016 and March 2017. RESULTS: The response rate to the online survey was 73.1% (144/197) with 68.1% (98/144) reporting an established clinical service and 3.5% (5/144) setting up a service. Approximately 30,000 tests are performed a year with 93.0% (80/86) using cycle ergometry. Colorectal surgical patients are the most frequently tested (89.5%, 77/86). The majority of tests are performed and interpreted by anaesthetists. There is variability in the methods of interpretation and reporting of CPET and limited external validation of results. CONCLUSIONS: This survey has identified the continued expansion of perioperative CPET services in the UK which have doubled since 2011. The vast majority of CPET tests are performed and reported by anaesthetists. It has highlighted variation in practice and a lack of standardised reporting implying a need for practice guidelines and standardised training to ensure high-quality data to inform perioperative decision making.

Double bypass for inoperable pancreatic malignancy at laparotomy: postoperative complications and long-term outcome.

INTRODUCTION: Between 4% and 13% of patients with operable pancreatic malignancy are found unresectable at the time of surgery. Double bypass is a good option for fit patients but it is associated with a high risk of postoperative complications. The aim of this study was to identify pre-operatively which patients undergoing double bypass are at high risk of complications and to assess their long-term outcome. METHODS: Of the 576 patients undergoing pancreatic resections between 2006 and 2011, 50 patients who underwent a laparotomy for a planned pancreaticoduodenectomy had a double bypass procedure for inoperable disease. Demographic data, risk factors for postoperative complications and pre-operative anaesthetic assessment data including the Portsmouth Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity (P-POSSUM) and cardiopulmonary exercise testing (CPET) were collected. RESULTS: Fifty patients (33 men and 17 women) were included in the study. The median patient age was 64 years (range: 39-79 years). The complication rate was 50% and the in-hospital mortality rate was 4%. The P-POSSUM physiology subscore and low anaerobic threshold at CPET were significantly associated with postoperative complications (p =0.005 and p =0.016 respectively) but they were unable to predict them. Overall long-term survival was significantly shorter in patients with postoperative complications (9 vs 18 months). Postoperative complications were independently associated with poorer long-term survival (p =0.003, odds ratio: 3.261). CONCLUSIONS: P-POSSUM and CPET are associated with postoperative complications but the possibility of using them for risk prediction requires further research. However, postoperative complications following double bypass have a significant impact on long-term survival and this type of surgery should therefore only be performed in specialised centres.

Effects of low cardiopulmonary reserve on pancreatic leak following pancreaticoduodenectomy.

BACKGROUND: Postoperative complications are increased in patients with reduced cardiopulmonary reserve undergoing major surgery. Pancreatic leak is an important contributor to postoperative complications and death following pancreaticoduodenectomy. The aim of this study was to determine whether reduced cardiopulmonary reserve was a risk factor for pancreatic leak. METHODS: All patients who underwent pancreaticoduodenectomy between January 2006 and July 2010 were identified from a prospectively held database. Data analysis was restricted to those who underwent cardiopulmonary exercise testing during preoperative assessment. Pancreatic leak was defined as grade A, B or C according to the International Study Group on Pancreatic Fistula definition. An anaerobic threshold (AT) cut-off value of 10·1 ml per kg per min was used to identify patients with reduced cardiopulmonary reserve. Univariable and multivariable analyses were performed to identify other risk factors for pancreatic leak. RESULTS: Some 67 men and 57 women with a median age of 66 (range 37-82) years were identified. Low AT was significantly associated with pancreatic leak (45 versus 19·2 per cent in patients with greater cardiopulmonary reserve; P = 0·020), postoperative complications (70 versus 38·5 per cent; P = 0·013) and prolonged hospital stay (29·4 versus 17·5 days; P = 0·001). On multivariable analysis, an AT of 10·1 ml per kg per min or less was the only independent factor associated with pancreatic leak. CONCLUSION: Low cardiopulmonary reserve was associated with pancreatic leak following pancreaticoduodenectomy. AT seems a useful tool for stratifying the risk of postoperative complications.

Comparative rates of antibiotic action against Staphylococcus epidermidis biofilms.

The relative resistance of S. epidermidis implant-associated infections to antibiotic therapy has been ascribed to a protective function of the gluelike biofilm matrix produced by strains of S. epidermidis in contact with artificial surfaces. Using a standardized S. epidermidis biofilm assay we determined the periods of exposure required by various antibiotics to produce cessation of biofilm metabolic activity. Rifampin has the superior rate of action, producing substantial disruption of biofilm activity by 7 hr of exposure, but leading to replacement of the susceptible bacterial cells by rifampin-resistant mutant survivors. Other antibiotics required longer periods of exposure, in excess of 48 hr, but produced a bactericidal outcome. Combinations of antibiotics with rifampin produced strikingly divergent results. Cefazolin and vancomycin (cell wall active antibiotics) produced a bactericidal outcome at 16 hr of exposure, whereas gentamicin (aminoglycoside) neutralized the rapid action of rifampin with metabolic activity maintained at 48 hr. We confirmed the selectively protective function of the S. epidermidis biofilm with regard to antibiotic action. In vitro biofilm assays may be of value in guiding antibiotic therapy in S. epidermidis implant-associated infection.

The effect of protamine on antibiotic action against Staphylococcus epidermidis biofilms.

Infection associated with medical devices may involve bacterial biofilms, a possible cause of antibiotic resistance. Protamine, a basic polypeptide, depresses the metabolic activity of Staphylococcus epidermidis in a standardized biofilm assay. The resistance of the biofilm preparations to many antibiotics, with the sole exception of rifampin, was confirmed. Rifampin produced predominant lysis and killing with foci of genetically programmed resistance. The combination of protamine with antibiotics produced no change, except the combination with rifampin where clear classic synergism with a totally bactericidal outcome was demonstrated. Protamine is a member of the larger family of charged polycations, some of which possess membrane potential altering properties, possibly interfering with the protective nature exhibited by the negatively charged bacterial biofilm matrix.

Antibiotic activity against Staphylococcus epidermidis biofilms in dialysis fluids.

Infection associated with medical devices may be resistant to conventional antibiotic therapy. A potential mechanism explaining this variable therapeutic response is the presence of bacterial biofilms on the surface of the prosthetic material which may confer a biologically important protective function to the entrapped bacteria. To study these questions, we prepared standardized biofilms and conventional fluid phase cultures from a panel of ten Staphylococcus epidermidis strains. All ten strains showed in the fluid phase a variable pattern of sensitivity to seven antibiotics but were uniformly sensitive to rifampin and vancomycin. In the biofilm phase they demonstrated solid antibiotic resistance with the variable exception of rifampin. The nature of the milieu was a major variable. Fresh peritoneal dialysis solution enhanced the activity of rifampin but this effect was not present with spent or neutral dialysis fluids.

The effects of heparin on rifampin activity against Staphylococcus epidermidis biofilms.

Rifampin shows unique antimicrobial activity against Staphylococcus epidermidis biofilms, although in the in vitro situation rifampin resistance emerges rapidly by the selection of preexisting resistant mutants present in a small number in any large bacterial population. Fresh peritoneal dialysis solution is synergistic with rifampin suppressing rifampin resisters. The antimicrobial properties of rifampin are affected by heparin and protamine in entirely different directions. Heparin blocks the action of rifampin whereas protamine is synergistic producing a total bactericidal outcome. Protamine, when combined with heparin, unexpectedly did not influence the ability of heparin to antagonize rifampin. The mechanisms involved are unknown. The results are discussed in terms of known characteristics of the drugs and of the biofilm surface.

The activity of rifampin and analogs against Staphylococcus epidermidis biofilms in a CAPD environment model.

Rifampin has been noted to exhibit exceptional antimicrobial activity against Staphylococcus epidermidis biofilms as compared to commonly used antibiotics. To further explore this unique effect of rifampin, we evaluated the antimicrobial activity of three commercially available preparations of rifampin, two rifampin analogs (CGP29861 and rifapentine) and the parent compound rifamycin SV. These were tested against standardized S. epidermidis biofilms in various milieus. All six members of the rifamycin group tested demonstrated marked antimicrobial activity but with minor foci of resisters when tested in a peptone water environment. The microscopy of the exposed biofilms showed profound lysis and morphological distortion of the remaining cells. The synergistic elimination of the foci of resistance was achieved in an environment of fresh peritoneal dialysis (PD) solution or by the addition of vancomycin. Neither vancomycin nor fresh PD solution demonstrated significant antimicrobial activity when tested alone with biofilm preparations. Spent PD fluid markedly antagonized the activity of the rifamycins with the exception of the rifampin analogs, an effect primarily of pH. The synergistic effect of vancomycin with the rifamycins was not affected either by protein content or pH, leaving the antagonistic properties of spent PD fluid unexplained. The variable activity of the different members of the rifamycin group underlines the importance of structural differences in determining their interaction with bacterial biofilms. Further precision of the nature of these structural interactions is seen to have considerable potential for therapeutic advancement of catheter-associated sepsis.

Rifampin activity against Staphylococcus epidermidis biofilms.

Rifampin has demonstrated remarkable antimicrobial activity against Staphylococcus epidermidis biofilms. Four other antibiotics had no effect when used alone; three of these (clindamycin, gentamicin, and tetracycline) were antagonistic to rifampin when used in combination. Vancomycin was synergistic with rifampin, producing complete killing. Fresh peritoneal dialysis (PD) solution accentuated the antimicrobial activity, whereas spent PD fluid neutralized it.

Antibiotic prophylaxis in vascular surgery: pharmacokinetic study of four commonly used cephalosporins.

Plasma levels of antibiotics often do not correlate well with their tissue levels. To determine optimal antibiotic coverage for prophylactic effect in vascular surgery, we studied the tissue pharmacokinetics of four cephalosporins in dogs: cefazolin, cefoxitin, cefamandole, and moxalactam for 3 hours after a single (25 mg/kg) intravenous injection. The minimal inhibitory concentration (MIC) of these antibiotics for the three most common pathogens involved in graft infections (Staphylococcus aureus, S. albus, and Escherichia coli) and their tissue concentration (TC) in the plasma, muscle, subcutaneous tissue, and aortic wall were assayed. The data are presented as TC/MIC ratio. Cefoxitin and moxalactam failed to achieve an effective therapeutic TC/MIC ratio (greater than 10) for S. aureus and S. albus in all the tissues studied whereas cefoxitin and cefamandole were above therapeutic levels. All antibiotics achieved an effective therapeutic ratio against E. coli, but cefamandole performed better (p less than 0.05) than cefoxitin; the latter reached effective levels at 3 hours. Cefamandole attained the most effective bioactive aortic tissue levels when the three most common pathogens were considered together and should therefore be considered as an antibiotic agent of choice for prophylaxis in vascular surgery.

Are burn wound biopsies obsolete? A comparative study of bacterial quantitation in burn patients using the absorbent disc and biopsy techniques.

A study of bacterial quantitation in burn wounds was undertaken to compare a new absorbent paper disc technique with the standard burn wound biopsy technique. In the first part of the study 228 paired samples were used to compare the two methods; a high correlation coefficient was found with the four most commonly encountered bacteria, and both methods showed a high specificity and sensitivity for each of the organisms. In the second portion of the study, the discs were compared with burn wound biopsies that had been divided into their superficial and deep segments. Thirty paired samples were studied and again the correlation was high, indicating that the disc technique also measured the organisms found in the deeper tissue levels. The absorbent disc technique is simple, convenient, noninvasive, inexpensive, and yields reproducible results. These findings indicate that burn wound biopsies may no longer be required for infection monitoring in the burn patient.

Pulmonary bacterial clearance and alveolar macrophage function in septic shock lung.

The association between the pulmonary bacterial clearance and the development of septic shock lung has been demonstrated in porcine and canine experimental models. In order to elucidate the role of the pulmonary reticuloendothelial system in bacterial clearance, the functions of alveolar macrophages (AM) obtained by bronchopulmonary lavage were studied. Five piglets were infused intravenously with Pseudomonas aeruginosa labeled with tritiated thymidine at 3 to 6 X 10(8) CFU/kg/min. Septic shock and manifestations like those of the adult respiratory distress syndrome developed within 1 h, and the pigs died within 2 to 3 h. Pulmonary bacterial clearance was 93% initially, and progressively decreased to 29%, as Pao2 decreased and lung water increased. The number of bacteria in the serial lung biopsy specimens increased steadily, although the distribution was not homogeneous. Differential centrifugations, repeated washings, and scintillation countings of the lavage fluid showed that in vivo AM phagocytosis was nil, despite the abundant bacteria found in the lavage fluid. However, when these AM were washed and tested in vitro in the presence of optimal concentrations of opsonin and oxygen, their phagocytic capability was well preserved, and was not significantly different from that of prebacterial infusion baseline values. It is concluded that in the septic shock lung, the lung clears bacteria not primarily by AM uptake but by other mechanisms, such as mechanical leakage into the pulmonary space, or by pulmonary intravascular leukocyte uptake. The apparent AM dysfunction in vivo is not intrinsic, and is likely to be caused by microenvironmental factors, such as lack of adequate opsonin and oxygen.

Metronidazole as a prophylactic agent in wound infection after colon surgery.

Metronidazole was the most effective antianaerobic agent tested in an in vitro system that used a high-density inoculum of mixed enteric organisms. A prospective randomized clinical trial assessing metronidazole and neomycin against erythromycin and neomycin as preoperative bowel preparations demonstrated a marked reduction in the anaerobic flora of patients receiving metronidazole. A second trial revealed that intravenous metronidazole administered 1 hour before and at 8 and 16 hours after the operation provided similar protection against wound infection. Our total experience with 181 patients receiving metronidazole either by mouth or intravenously was three wound infections caused by aerobic enteric organisms, as incidence of 1.6%. There was no wound infection owing to anaerobic organisms of gut origin. The residual problem was that of six wound infections resulting from Staphylococcus aureus presumed to be of skin origin.

Elective colon surgery: clindamycin versus metronidazole prophylaxis.

Orally administered clindamycin-neomycin as a prophylactic antibiotic in patients scheduled to undergo colon surgery was compared to orally administered metronidazole-neomycin. Clindamycin levels of the colon contents and the mucosa were 8 to 10 times higher than the serum levels. Three of the 43 patients who received metronidazole had wound infection whereas none of the 38 patients who received clindamycin did. Clindamycin may help to prevent staphylococcal infection, a known problem associated with metronidazole use. It may also play a role in preventing infection at the anastomosis in patients who undergo colon resection.

Penicillin tolerance of human isolates of group C streptococci.

Seventeen clinical isolates of group C streptococci were tested for penicillin tolerance. Sixteen of the strains showed penicillin tolerance with a 32-fold or greater difference between the minimal inhibitory concentration and the minimal bactericidal concentration. Synergism was demonstrated with a combination of penicillin and gentamicin for all 17 strains tested. The rate of antibiotic killing was measured for five of the streptococcal strains by using the combination of penicillin and gentamicin. All isolates were killed within 5 h with the combination, but viable organisms were recovered after 48 h when either drug was used alone. Our study suggests that penicillin tolerance with group C streptococci may occur frequently and may account for the poor outcome of serious group C streptococcal infections tested with penicillin alone.

The influence of oral versus parenteral preoperative metronidazole on sepsis following colon surgery.

The incidence of wound infection following surgery on the colon is reduced by the preoperative adminstration of appropriate antibiotics. Quantitative bacteriologic studies raise the fundamental question as to whether effective antibiotic prophylaxis results from reduction of the bacterial content of the gut prior to surgery or whether effective tissue levels of the antibiotic is the key factor. Oral neomycin and metronidazole have been shown to markedly reduce the incidence of wound infection following colon surgery. A prospective randomized double-blind clinical trial was undertaken to compare the effectiveness of intravenous metronidazole (high tissue level) with oral administration (tissue and gut activity) on the incidence of wound infection. There was no difference in wound infection rates between the two groups of patients. Surprisingly, there was a significant reduction in the bacteroides content in the colon of patients who received intravenous metronidazole one hour before operation to a level almost equal to that achieved by the administration of the drug for two days by mouth before operation. Metronidazole levels in the colon at the time of surgery were comparable for both groups. The median time for recolonization of the colon was six days for the oral group, and four days for the intravenous group. Although peritoneal fluid contained significant numbers of coliforms and enterococci, clinical infection did not occur. These data suggest that systemic antibiotics effective against anerobic flora of the colon markedly reduce postoperative septic complications.

The effect of metronidazole on the incidence of postoperative wound infection in elective colon surgery.

A prospective randomized clinical trial assessing the relative effectiveness of erythromycin-neomycin and metronidazole-neomycin as a preoperative bowel preparation was carried out. Bacteriologic studies of feces and colon content revealed no significant difference in the reduction of aerobic bacteria between the two groups. There was, however, a significantly greater reduction in anaerobic bacteria in the feces and colon contents of patients receiving metronidazole. Wound infection rate was 25% in the erythromycin group, and organisms recovered from the wound in all cases were fecal in nature. Two wound infections occurred in the metronidazole group (5%) and in both cases the organisms recovered were staphylococci of presumed skin origin. These studies suggest that anaerobic bacteria are the major contributors to wound infection after colon surgery and that their specific reduction is associated with a lower incidence of wound infection.