Insulin and glycolysis dependency of cardioprotection by nicotinamide riboside

Decreased nicotinamide adenine dinucleotide (NAD+) levels contribute to various pathologies such as ageing, diabetes, heart failure and ischemia-reperfusion injury (IRI). Nicotinamide riboside (NR) has emerged as a promising therapeutic NAD+ precursor due to efficient NAD+ elevation and was recently shown to be the only agent able to reduce cardiac IRI in models employing clinically relevant anesthesia. However, through which metabolic pathway(s) NR mediates IRI protection remains unknown. Furthermore, the influence of insulin, a known modulator of cardioprotective efficacy, on the protective effects of NR has not been investigated. Here, we used the isolated mouse heart allowing cardiac metabolic control to investigate: (1) whether NR can protect the isolated heart against IRI, (2) the metabolic pathways underlying NR-mediated protection, and (3) whether insulin abrogates NR protection. NR protection against cardiac IRI and effects on metabolic pathways employing metabolomics for determination of changes in metabolic intermediates, and 13C-glucose fluxomics for determination of metabolic pathway activities (glycolysis, pentose phosphate pathway (PPP) and mitochondrial/tricarboxylic acid cycle (TCA cycle) activities), were examined in isolated C57BL/6N mouse hearts perfused with either (a) glucose + fatty acids (FA) ("mild glycolysis group"), (b) lactate + pyruvate + FA ("no glycolysis group"), or (c) glucose + FA + insulin ("high glycolysis group"). NR increased cardiac NAD+ in all three metabolic groups. In glucose + FA perfused hearts, NR reduced IR injury, increased glycolytic intermediate phosphoenolpyruvate (PEP), TCA intermediate succinate and PPP intermediates ribose-5P (R5P) / sedoheptulose-7P (S7P), and was associated with activated glycolysis, without changes in TCA cycle or PPP activities. In the "no glycolysis" hearts, NR protection was lost, whereas NR still increased S7P. In the insulin hearts, glycolysis was largely accelerated, and NR protection abrogated. NR still increased PPP intermediates, with now high 13C-labeling of S7P, but NR was unable to increase metabolic pathway activities, including glycolysis. Protection by NR against IRI is only present in hearts with low glycolysis, and is associated with activation of glycolysis. When activation of glycolysis was prevented, through either examining "no glycolysis" hearts or "high glycolysis" hearts, NR protection was abolished. The data suggest that NR's acute cardioprotective effects are mediated through glycolysis activation and are lost in the presence of insulin because of already elevated glycolysis.

Performance and usability of pre-operative prediction models for 30-day peri-operative mortality risk: a systematic review

Estimating pre-operative mortality risk may inform clinical decision-making for peri-operative care. However, pre-operative mortality risk prediction models are rarely implemented in routine clinical practice. High predictive accuracy and clinical usability are essential for acceptance and clinical implementation. In this systematic review, we identified and appraised prediction models for 30-day postoperative mortality in non-cardiac surgical cohorts. PubMed and Embase were searched up to December 2022 for studies investigating pre-operative prediction models for 30-day mortality. We assessed predictive performance in terms of discrimination and calibration. Risk of bias was evaluated using a tool to assess the risk of bias and applicability of prediction model studies. To further inform potential adoption, we also assessed clinical usability for selected models. In all, 15 studies evaluating 10 prediction models were included. Discrimination ranged from a c-statistic of 0.82 (MySurgeryRisk) to 0.96 (extreme gradient boosting machine learning model). Calibration was reported in only six studies. Model performance was highest for the surgical outcome risk tool (SORT) and its external validations. Clinical usability was highest for the surgical risk pre-operative assessment system. The SORT and risk quantification index also scored high on clinical usability. We found unclear or high risk of bias in the development of all models. The SORT showed the best combination of predictive performance and clinical usability and has been externally validated in several heterogeneous cohorts. To improve clinical uptake, full integration of reliable models with sufficient face validity within the electronic health record is imperative.

Prospective comparison of three methods for detecting peri-operative neurocognitive disorders in older adults undergoing cardiac and non-cardiac surgery

Postoperative neurocognitive disorders occur frequently in older adult patients. Neuropsychological assessment is the gold standard for diagnosis, but the resources required for routine use are significant. Instead, it is common for simplified and unvalidated tests to be used for trials and in clinical practice. We undertook a single-centre prospective observational study in elective surgical patients aged ≥ 65 years recruited between September 2019 and January 2021. Patients underwent neuropsychological assessment, the Modified Telephone Interview for Cognitive Status and Montreal Cognitive Assessment before surgery. Tests were repeated at approximately four to eight postoperative weeks. We included 105 patients and 28 (27%) were lost to follow-up. Pre-operative Modified Telephone Interview for Cognitive Status and cognitive domain scores were very weakly to moderately correlated (r = 0.09-0.41). Pre-operative Montreal Cognitive Assessment and cognitive domain scores were very weakly to weakly correlated (r = 0.17-0.37) Postoperative Modified Telephone Interview for Cognitive Status and cognitive domain scores were very weakly to weakly correlated (r = 0.09-0.36). Postoperative Montreal Cognitive Assessment score and cognitive domain scores were very weakly to weakly correlated (r = 0.07-0.36). Overall, there was limited agreement between tests. We conclude that the Modified Telephone Interview for Cognitive Status and Montreal Cognitive Assessment should not be used in isolation to diagnose postoperative neurocognitive disorders. There seems to be little to no pre-operative, postoperative or pre- to postoperative correlation between these tests and the neuropsychological assessment in older adults without pre-operative cognitive impairment.

Empagliflozin reduces TNFa-induced reactive oxygen species through inhibition of the human endothelial Na+/H+ exchanger 1

Background

Chronic low-grade inflammation, endothelial dysfunction and oxidative stress are major interactive pathways contributing to the pathogenesis of HFpEF. The sodium/glucose cotransporter 2 (SGLT2) inhibitor Empagliflozin (EMPA) inhibits inflammation-induced ROS generation in endothelial cells. EMPA also lowers Na+/H+ exchanger 1 (NHE1) activity and cytoplasmatic Na+ levels ([Na+]c) in cardiomyocytes.

Purpose

It is unknown how inflammation causes oxidative stress in endothelial cells and how EMPA can mitigate this. Here we examined for human endothelial cells whether 1) inflammatory mediators activate NHE1 activity, 2) increased [Na+]c mediates the inflammation-induced ROS production, and 3) EMPA reduces inflammation-induced ROS through NHE1 inhibition.

Methods

Human umbilical vein endothelial cells (HUVECs) and human coronary artery endothelial cells (HCAECs) were incubated with vehicle (V), 10ng/mL TNFα, 1μM EMPA or the canonical NHE1 inhibitor 10μM Cariporide. NHE1 activity was measured using the intracellular pH sensitive seminaphtharhodafluor fluorescence, by the pH recovery rate after an ammonium pulse. Intracellular ROS were detected by fluorescent live cell imaging in the presence of 10ng/mL TNFα or under increased Na+ conditions using 100nM ouabain (partial inhibition of the Na+/K+ pump). [Na+]c was measured using the sodium-binding benzofuran isophthalate 1 fluorescent probe.

Results

TNFα enhanced NHE1 activity in HCAECs (Fig a, in Δ[H+]/sec, V 0.81±0.14, TNFα 1.86±0.35 p<0.05). Increasing [Na+]c by ouabain elevated ROS generation (Fig b, in mM, HUVECs; V 5.6±1.3, ouabain 25.2±1.6 p<0.001, HCAECs; V 18.5±2.4, ouabain 91.2±32.6 p<0.05). EMPA reduced NHE1 activity in HUVECs (in Δ[H+]/sec, V 3.55±0.54, EMPA 1.66±0.25 p<0.01 vs V, Cariporide 0.95±0.11 p<0.001 vs V). HCAECs showed similar results. EMPA lowered [Na+]c (HUVECs; from 8.8±0.9 to 6.0±0.5 mM, p<0.05, HCAECs; from 7.8±0.7 to 4.0±0.8 mM, p<0.001). ROS generation was reversed in the presence of EMPA and/or Cariporide indicating that the effect was mediated by NHE inhibition (Fig c).

Conclusions

TNFα induces oxidative stress in EC through NHE1 activation and the consequently increased [Na+]c. EMPA acutely inhibits TNFα-induced ROS generation by inhibiting NHE1 and lowering [Na+]c in human cardiac and non-cardiac endothelial cells. Our data suggest that the previously reported cardiac effects of EMPA on NHE1 and [Na+]c are also present in endothelial cells. Endothelial ion homeostasis may be a valuable target to reduce inflammation-induced ROS generation and can constitute the pathway through which SGLT2 inhibitors offer protection in HFpEF patients, as examined in the EMPEROR-Preserved trial.

Funding Acknowledgement

Type of funding sources: None. Figure 1

Effects of surgery and general anaesthesia on sleep-wake timing: CLOCKS observational study

Surgery and general anaesthesia have the potential to disturb the body’s circadian timing system, which may affect postoperative outcomes. Animal studies suggest that anaesthesia could induce diurnal phase shifts, but clinical research is scarce. We hypothesised that surgery and general anaesthesia would result in peri‐operative changes in diurnal sleep–wake patterns in patients. In this single‐centre prospective cohort study, we recruited patients aged ≥18 years scheduled for elective surgery receiving ≥30 min of general anaesthesia. The Munich Chronotype Questionnaire and Pittsburgh Sleep Quality Index were used to determine baseline chronotype, sleep characteristics and sleep quality. Peri‐operative sleeping patterns were logged. Ninety‐four patients with a mean (SD) age of 52 (17) years were included; 56 (60%) were female. The midpoint of sleep (SD) three nights before surgery was 03.33 (55 min) and showed a phase advance of 40 minutes to 02.53 (67 min) the night after surgery (p < 0.001). This correlated with the midpoint of sleep three nights before surgery and was not associated with age, sex, duration of general anaesthesia or intra‐operative dexamethasone use. Peri‐operatively, patients had lower subjective sleep quality and worse sleep efficiency. Disruption started from one night before surgery and did not normalise until 6 days after surgery. We conclude that there is a peri‐operative phase advance in midpoint of sleep, confirming our hypothesis that surgery and general anaesthesia disturb the circadian timing system. Patients had decreased subjective sleep quality, worse sleep efficiency and increased daytime fatigue.

[Postoperative remote monitoring]

During the course of surgical interventions, complications mostly occur in the postoperative period. Slight clinical indications can be observed, which precede a significant deterioration of the patient's condition. On the general ward vital parameters, such as heart and breathing frequencies are measured every 4-8 h. Even if the monitoring of critically ill patients is increased to every 2 h and the measurement of vital functions takes 10 min, the patient is only monitored for 120 min in a 24 h period and remains postoperatively on the general ward without monitoring for 22 out of 24 h. New wireless monitoring systems are available to continuously register some vital functions with the aid of wearable sensors. These systems can alert and alarm ward personnel if the patient's condition deteriorates. Although the optimal monitoring system does not yet exist and implementation of these new wireless monitoring systems might involve some risks, these new methods offer a great opportunity to optimize surveillance of postoperative patients on the general ward.

Remote wireless vital signs monitoring on the ward for early detection of deteriorating patients: A case series

INTRODUCTION

Remote wireless monitoring is a new technology that allows the continuous recording of ward patients' vital signs, supporting nurses by measuring vital signs frequently and accurately. A case series is presented to illustrate how these systems might contribute to improved patient surveillance.

METHODS AND RESULTS

Five hospitals in three European countries installed a remote wireless vital signs monitoring system on medical or surgical wards. Heart rate, respiratory rate and temperature were measured by the system every 2 min. Four cases of (paroxysmal) atrial fibrillation are presented, two cases of sepsis and one case each of pyrexia, cardiogenic pulmonary edema and pulmonary embolisms. All cases show that the remote monitoring system revealed the first signs of ventilatory and circulatory deterioration before a change in the trends of the respective values became obvious by manual vital signs measurement.

DISCUSSION

This case series illustrates that a wireless remote vital signs monitoring system on medical and surgical wards has the potential to reduce time to detect deteriorating patients.

Novel method for intraoperative assessment of cerebral autoregulation by paced breathing

Background

Cerebral autoregulation (CA) is the mechanism that maintains constancy of cerebral blood flow (CBF) despite variations in blood pressure (BP). Patients with attenuated CA have been shown to have an increased incidence of peri-operative stroke. Studies of CA in anaesthetized subjects are rare, because a simple and non-invasive method to quantify the integrity of CA is not available. In this study, we set out to improve non-invasive quantification of CA during surgery. For this purpose, we introduce a novel method to amplify spontaneous BP fluctuations during surgery by imposing mechanical positive pressure ventilation at three different frequencies and quantify CA from the resulting BP oscillations.

Methods

Fourteen patients undergoing sevoflurane anaesthesia were included in the study. Continuous non-invasive BP and transcranial Doppler-derived CBF velocity (CBF V ) were obtained before surgery during 3 min of paced breathing at 6, 10, and 15 bpm and during surgery from mechanical positive pressure ventilation at identical frequencies. Data were analysed using frequency domain analysis to obtain CBF V -to-BP phase lead as a continuous measure of CA efficacy. Group averages were calculated. Values are means ( sd ), and P <0.05 was used to indicate statistical significance.

Results

Preoperative vs intraoperative CBF V -to-BP phase lead was 43 (9) vs 45 (8)°, 25 (8) vs 24 (10)°, and 4 (6) vs -2 (12)° during 6, 10, and 15 bpm, respectively (all P =NS).

Conclusions

During surgery, cerebral autoregulation indices were similar to values determined before surgery. This indicates that CA can be quantified reliably and non-invasively using this novel method and confirms earlier evidence that CA is unaffected by sevoflurane anaesthesia.

Clinical trial registration

NCT03071432.

Sevoflurane based anaesthesia does not affect already impaired cerebral autoregulation in patients with type 2 diabetes mellitus

BACKGROUND

The baroreflex regulates arterial blood pressure (BP). During periods when blood pressure changes, cerebral blood flow (CBF) is kept constant by cerebral autoregulation (CA). In patients with diabetes mellitus (DM), low baroreflex sensitivity (BRS) is associated with impaired CA. As sevoflurane-based anaesthesia obliterates BRS, we hypothesised that this could aggravate the already impaired CA in patients with DM resulting in a 'double-hit' on cerebral perfusion leading to increased fluctuations in blood pressure and cerebral perfusion.

METHODS

On the day before surgery, we measured CBF velocity (CBFV), heart rate, and BP to determine BRS and CA efficacy (CBFV_mean-to-BP_mean-phase lead) in 25 patients with DM and in 14 controls. During the operation, BRS and CA efficacy were determined during sevoflurane-based anaesthesia. Patients with DM were divided into a group with high BRS (DM_BRS↑) and a group with low BRS (DM_BRS↓). Values presented are median (inter-quartile range).

RESULTS

Preoperative vs intraoperative BRS was 6.2 (4.5-8.5) vs 1.9 (1.1-2.5, P<0.001) ms mm Hg^-1 for controls, 5.8 (4.9-7.6) vs 2.7 (1.5-3.9, P<0.001) ms mm Hg^-1 for patients with DM_BRS↑, and 1.9 (1.5-2.8) vs 1.1 (0.6-2.5, P=0.31) ms mm Hg^-1 for patients with DM_BRS↓. Preoperative vs intraoperative CA efficacy was 43° (38-46) vs 43° (38-51, P=0.30), 44° (36-49) vs 41° (32-49, P=0.52), and 34° (28-40) vs 30° (27-38, P=0.64) for controls, DM_BRS↑, and DM_BRS↓ patients, respectively.

CONCLUSIONS

In diabetic patients with low preoperative BRS, preoperative CA efficacy was also impaired. In controls and diabetic patients, CA was unaffected by sevoflurane-based anaesthesia. We therefore conclude that sevoflurane-based anaesthesia does not contribute to a 'double-hit' phenomenon on cerebral perfusion.

CLINICAL TRIAL REGISTRATION

NCT 03071432.

Peri-operative continuation of metformin does not improve glycaemic control in patients with type 2 diabetes: A randomized controlled trial

Historically, metformin was withheld before surgery for fear of metformin-associated lactic acidosis. Currently, however, this risk is deemed to be low and guidelines have moved towards the continuation of metformin. We hypothesized that continuing metformin peri-operatively would lower postoperative serum glucose level without an effect on plasma lactate levels. We performed a single-blind multicentre randomized controlled trial in people with type 2 diabetes mellitus scheduled for non-cardiac surgery and continued (MF+ group) or withheld (MF- group) metformin before surgery. The main outcome measures were the differences in peri-operative plasma glucose and lactate levels. We randomized 70 patients (37 MF+ group and 33 MF- group) with type 2 diabetes mellitus. Postoperative glucose levels were similar in the MF+ and the MF- groups (8.2 ± 1.8 vs 8.3 ± 2.3 mmol/L P = .95) Although preoperative lactate levels were slightly higher in the MF+ group compared with the MF- group (1.5 vs 1.2 mmol/L; P = .02), the postoperative lactate levels were not significantly different (1.2 vs 1.0 mmol/L; P = .18). In conclusion, continuation of metformin during elective non-cardiac surgery does not improve glucose control or raise lactate levels to a clinically relevant degree.

Effects of combined helium pre/post-conditioning on the brain and heart in a rat resuscitation model

BACKGROUND

The noble gas helium induces cardio- and neuroprotection by pre- and post-conditioning. We investigated the effects of helium pre- and post-conditioning on the brain and heart in a rat resuscitation model.

METHODS

After approval by the Animal Care Committee, 96 Wistar rats underwent cardiac arrest for 6 min induced by ventricular fibrillation. Animals received 70% helium and 30% oxygen for 5 min before cardiac arrest and for 30 min after restoration of spontaneous circulation (ROSC). Control animals received 70% nitrogen and 30% oxygen. Hearts and brains were excised after 2, 4 h or 7 days. Neurological degeneration was evaluated using TUNEL and Nissl staining in the hippocampal CA-1 sector. Cognitive function after 7 days was detected with the tape removal test. Molecular targets were measured by infrared western blot. Data are shown as median [Interquartile range].

RESULTS

Helium treatment resulted in significantly less apoptosis (TUNEL positive cells/100 pixel 73.5 [60.3-78.6] vs.78.2 [70.4-92.9] P = 0.023). Changes in Caveolin-3 expression in the membrane fraction and Hexokinase-II in the mitochondrial fraction were observed in the heart. Caveolin-1 expression of treated animals significantly differed from control animals in the membrane fraction of the heart and brain after ROSC.

CONCLUSION

Treatment with helium reduced apoptosis in our resuscitation model. Differential expression levels of Caveolin-1, Caveolin-3 and Hexokinase II in the heart were found after helium pre- and post-conditioning. No beneficial effects were seen on neurofunctional outcome.

Bispectral Index Guided Target Controlled Midazolam Sedation: a new advanced technique for dental procedures

OBJECTIVES

To assess the efficacy and safety of Bispectral Index (BIS) guided Target Controlled Infusion (TCI) of midazolam for anxiolysis or minimal sedation during extensive periodontal or implant surgery in a single operator/sedationist model.

METHODS

Retrospective analysis of thirty adult ASA 1 or ASA 2 patients undergoing periodontal surgery or dental implant surgery under local anaesthesia were included. The calculated effect site concentration (Ce) of midazolam applied by TCI, BIS, heart rate (HR), and peripheral oxygen saturation (SpO2) were monitored continuously. Non-invasive blood pressure (NIBP) and mean arterial pressure (MAP) were measured every 10 minutes. All peri-operative parameters were recorded every 10 minutes. All patients were interviewed 1 week after the procedure to explore their experience of sedation and the periodontal or implant surgery procedure.

RESULTS

Extensive periodontal or implant surgery treatment in all 30 patients was completed in a mean time of 120 min (range 50-180 min). The calculated mean effect site concentration for midazolam was 50 ng/ml (range 24-80). The mean BIS was 85 (74-100) during induction and was maintained between 80 and 90 during the oral surgical procedure by adjusting TCI Ce. There were no clinically significant cardiopulmonary changes during midazolam infusion with regard to SpO2, NIBP, MAP and heart rate. Patients experienced profound anterograde amnesia and were very satisfied with the sedation and the surgical procedure.

CONCLUSIONS

BIS guided TCI sedation with midazolam facilitates predictable minimal sedation enabling long periodontal or implant surgery procedures by a single operator/sedationist within safe physiological limits.

Very Long-Chain Acyl-Coenzyme A Dehydrogenase Deficiency and Perioperative Management in Adult Patients

Surgery and anesthesia pose a threat to patients with very long-chain acyl-CoA dehydrogenase deficiency (VLCADD), because prolonged fasting, stress, and pain are known risk factors for the induction of metabolic derangement. The optimal perioperative management in these patients is unknown and the use of volatile agents and agents dissolved in fatty acids has been related to postoperative metabolic complications. However, the occurrence of metabolic derangement is multifactorial and depends, amongst others, on the severity of the mutation and residual enzyme activity. Current guidelines suggest avoiding both volatile anesthetics as well as propofol, which seriously limits the options for providing safe anesthesia. Therefore, we reviewed the available literature on the perioperative management of patients with VLCADD. We concluded that the use of some medications, such as volatile anesthetics, in patients with VLCADD might be wrongfully avoided and could in fact prevent metabolic derangement by the adequate suppression of pain and stress during surgery. We will illustrate this with a case report of an adult VLCADD patient undergoing minor surgery. Besides the use of remifentanil, anesthesia was uneventfully maintained with the use of sevoflurane, a volatile agent, and continuous glucose infusion. The patient was monitored with a continuous glucose meter and creatinine kinase measurements.

Hyperglycemia and ambulatory surgery

BACKGROUND

Perioperative hyperglycemia is associated with postoperative complications after major surgery. However, more than 50% of surgical procedures are performed in an ambulatory setting, where glucose is not routinely measured. The objectives of this study were to investigate the change in capillary glucose during ambulatory surgery, to identify patients at risk for perioperative increasing glucose and to evaluate whether hyperglycemia predisposes for complications after ambulatory surgery.

METHODS

In this prospective multicenter cohort study, adult patients planned for ambulatory surgery, were included and capillary glucose was measured 1 hour before and 1 hour after surgery. Patients were contacted 90 days after surgery to determine the occurrence of postoperative complications.

RESULTS

Nine hundred and nine patients were included, 48 (5.3%) patients had diabetes mellitus (DM). Overall median glucose increased from 5.4 mmol L-1 preoperatively to 5.6 mmol L-1 postoperatively (P<0.001). Hyperglycemia, glucose ≥7.8 mmol L-1, occurred in 8.8% of the patients. Dexamethasone administration (given in 406 [44.7%] patients) was a risk factor for glucose increase (P<0.001). Hyperglycemia was not a risk factor for postoperative complications (OR 1.19, 95%CI 0.57-2.48, P=0.646). However, prediagnosed DM was a risk factor for postoperative complications, independent of hyperglycemia (OR 2.56, 95%CI 1.10-5.97, P=0.030).

CONCLUSION

Minor ambulatory surgery is not associated with a clinically relevant increase in glucose. The very small glucose increase we observed could be attributed to the administration of dexamethasone for PONV prophylaxis. Hyperglycemia during ambulatory surgery is not associated with complications after discharge.

[Intravenous light sedation with midazolam by dentists]

Approximately 800,000 Dutch people refrain from going to the dentist because of fear. Behavioural therapy, a psychological approach to treating anxiety, is taught extensively at the various Dutch universities and is used in dental practice in the Netherlands. For medicinal treatment, dentists in the Netherlands use nitrous oxide sedation and orally administered benzodiazepines. For the intravenous administration of sedatives Dutch dentists are almost entirely dependent on an anaesthesiologist. Light intravenous sedation with midazolam can be used to make anxious patients more comfortable. Dutch dentists can apply light sedation with midazolam intravenously in adult patients themselves, subject to a wide range of conditions.

Is "really conscious" sedation with solely an opioid an alternative to every day used sedation regimes for colonoscopies in a teaching hospital? Midazolam/fentanyl, propofol/alfentanil, or alfentanil only for colonoscopy: a randomized trial

BACKGROUND

We investigated the satisfaction of patients and endoscopists and concurrently safety aspects of an "alfentanil only" and two clinically routinely used sedation regimes in patients undergoing colonoscopy in a teaching hospital.

METHODS

One hundred and eighty patients were prospectively randomized in three groups: M (midazolam/fentanyl), A (alfentanil), and P (propofol/alfentanil); M and A were administered by an endoscopy nurse, P by an anesthesia nurse. Interventions, heart rate, saturation, electrocardiogram, noninvasive blood pressure, and expiratory CO₂ were monitored using video assistance. After endoscopy, patients and gastroenterologists completed questionnaires about satisfaction.

RESULTS

A high level of satisfaction was found in all groups, with patients in group P being more satisfied with their sedation experience (median 1.75, p < 0.001). Gastroenterologist satisfaction varied not significantly between the three alternatives. Patients in group A felt less drowsy, could communicate more rapidly than patients in both other groups, and met discharge criteria immediately after the end of the procedure. Respiratory events associated with sedation were observed in 43% patients in group M, 47% in group P, but only 13% in group A (p < 0.001).

CONCLUSIONS

These results suggest that alfentanil could be an alternative for sedation in colonoscopy even in the setting of a teaching hospital. It results in satisfied patients easily taking up information, and recovering rapidly. Although one might expect to observe more respiratory depression with an "opioid only" sedation technique without involvement of anesthesia partners, respiratory events were less frequent than when other methods were used.

Analgesia without sedatives during colonoscopies: worth considering?

Colonoscopy is a proven method for bowel cancer screening and is often experienced as a painful procedure. Today, there are two main strategies to facilitate colonoscopy. First, deep sedation results in satisfied patients but increases sedation-associated risks and raises costs for healthcare providers. Second, there is the advocacy for colonoscopies without any form of sedation. This might be an option for a special group of patients, but does not hold true for everybody. Following Moerman’s hypothesis: “If pain is the crucial point, why do we need sedation?” this review shows the analgesic options for a painless procedure, increasing success rates without increasing risk of sedation. There are two agents, with the potential to be a nearly ideal analgesic agent for colonoscopy: alfentanil and nitrous oxide (N₂O). Administration of either substance causes the patient to be comfortable yet alert and facilitates a short turnover. Advantages of these drugs include rapid onset and offset of action, analgesic and anxiolytic effects, ease of titration to desired level, rapid recovery, and an excellent safety profile.

Cyclosporine A administered during reperfusion fails to restore cardioprotection in prediabetic Zucker obese rats in vivo

BACKGROUND AND AIMS

Hyperglycaemia blocks sevoflurane-induced postconditioning, and cardioprotection in hyperglycaemic myocardium can be restored by inhibition of the mitochondrial permeability transition pore (mPTP). We investigated whether sevoflurane-induced postconditioning is also blocked in the prediabetic heart and if so, whether cardioprotection could be restored by inhibiting mPTP.

METHODS AND RESULTS

Zucker lean (ZL) and Zucker obese (ZO) rats were assigned to one of seven groups. Animals underwent 25 min of ischaemia and 120 min of reperfusion. Control (ZL-/ZO Con) animals were not further treated. postconditioning groups (ZL-/ZO Sevo-post) received sevoflurane for 5 min starting 1min prior to the onset of reperfusion. The mPTP inhibitor cyclosporine A (CsA) was administered intravenously in a concentration of 5 (ZO CsA and ZO CsA+Sevo-post) or 10 mg/kg (ZO CsA10+Sevo-post) 5 min before the onset of reperfusion. At the end of reperfusion, infarct sizes were measured by TTC staining. Blood samples were collected to measure plasma levels of insulin, cholesterol and triglycerides. Sevoflurane postconditioning reduced infarct size in ZL rats to 35±12% (p<0.05 vs. ZL Con: 60±6%). In ZO rats sevoflurane postconditioning was abolished (ZO Sevo-post: 59±12%, n.s. vs. ZO Con: 58±6%). 5 mg and 10 mg CsA could not restore cardioprotection (ZO CsA+Sevo-post: 59±7%, ZO CsA10+Sevo-post: 57±14%; n.s. vs. ZO Con). In ZO rats insulin, cholesterol and triglyceride levels were significant higher than in ZL rats (all p<0.05).

CONCLUSION

Inhibition of mPTP with CsA failed to restore cardioprotection in the prediabetic but normoglycaemic heart of Zucker obese rats in vivo.

Ischaemic and morphine-induced post-conditioning: impact of mK(Ca) channels

BACKGROUND

Mitochondrial calcium-sensitive potassium (mK(Ca)) channels are involved in cardiac preconditioning. In the present study, we investigated whether also ischaemic-, morphine-induced post-conditioning, or both is mediated by the activation of mK(Ca) channels in the rat heart in vitro.

METHODS

Animals were treated in compliance with institutional and national guidelines. Male Wistar rats were randomly assigned to one of seven groups (each n = 7). Control animals were not further treated. Post-conditioning was induced either by 3 × 30 s of ischaemia/reperfusion (I-PostC) or by administration of morphine (M-PostC, 1 µM) for 15 min at the onset of reperfusion. The mK(Ca)-channel inhibitor paxilline (1 µM) was given with and without post-conditioning interventions (M-PostC+Pax, I-PostC+Pax, and Pax). As a positive control, we determined whether direct activation of mK(Ca) channels with NS1619 (10 µM) induced cardiac post-conditioning (NS1619). Isolated hearts underwent 35 min ischaemia followed by 120 min reperfusion. At the end of reperfusion, infarct sizes were measured by triphenyltetrazolium chloride staining.

RESULTS

In the control group, infarct size was 53 (5)% of the area at risk. Morphine- and ischaemic post-conditioning reduced infarct size in the same range [M-PostC: 37 (4)%, I-PostC: 35 (5)%; each P<0.05 vs control]. The mK(Ca)-channel inhibitor paxilline completely blocked post-conditioning [M-PostC+Pax: 47 (7)%, I-PostC+Pax: 51 (3)%; each P<0.05 vs M-PostC and I-PostC, respectively]. Paxilline itself had no effect on infarct size (NS vs control). NS1619 reduced infarct size to 33 (4)% (P < 0.05 vs control).

CONCLUSIONS

Ischaemic- and morphine-induced post-conditioning is mediated by the activation of mK(Ca) channels.

[Perioperative beta-receptor blockade. For and against]

Results from recent studies have questioned the application of beta-receptor blockers for reduction of morbidity and mortality during the perioperative period. This holds true especially for patients with no or only low cardiac risk. Although beta-receptor blockade was a form of standard therapy at the end of the 1990s, data today show no clear evidence for such a therapy not even in patients at risk for cardiac events. At least in patients with low risk the initiation of beta-receptor blockade during the perioperative period might lead to side-effects, thereby increasing morbidity and mortality.

Ischemic preconditioning phosphorylates mitogen-activated kinases and heat shock protein 27 in the diabetic rat heart

Diabetes mellitus blocks protection by ischemic preconditioning (IPC), but the mechanism is not known. We investigated the effect of ischemic preconditioning on mitogen-activated protein kinases (extracellular signal-regulated kinases 1 and 2, c-Jun N-terminal kinases, p38 mitogen-activated kinase) and heat shock protein 27 phosphorylation in diabetic and nondiabetic rat hearts in vivo. Two groups of anaesthetized nondiabetic and diabetic rats underwent a preconditioning protocol (3 cycles of 3 min coronary artery occlusion and 5 min of reperfusion). Two further groups served as untreated controls. Hearts were excised for protein measurements by Western blot. Four additional groups underwent 25 min of coronary occlusion followed by 2 h of reperfusion to induce myocardial infarction. In these animals, infarct size was measured. IPC reduced infarct size in the nondiabetic rats but not in the diabetic animals. In diabetic rats, IPC induced phosphorylation of the mitogen-activated protein kinases and of heat shock protein 27. We conclude that protection by IPC is blocked by diabetes mellitus in the rat heart in vivo without affecting phosphorylation of mitogen-activated protein kinases or heat shock protein 27. Therefore, the blockade mechanism of diabetes mellitus is downstream of mitogen-activated kinases and heat shock protein 27.

Hyperglycaemia blocks sevoflurane-induced postconditioning in the rat heart in vivo: cardioprotection can be restored by blocking the mitochondrial permeability transition pore

BACKGROUND

Recent studies showed that hyperglycaemia (HG) blocks anaesthetic-induced preconditioning. The influence of HG on anaesthetic-induced postconditioning (post) has not yet been determined. We investigated whether sevoflurane (Sevo)-induced postconditioning is blocked by HG and whether the blockade could be reversed by inhibiting the mitochondrial permeability transition pore (mPTP) with cyclosporine A (CsA).

METHODS

Chloralose-anaesthetized rats (n=7-11 per group) were subjected to 25 min coronary artery occlusion followed by 120 min reperfusion. Postconditioning was achieved by administration of 1 or 2 MAC sevoflurane for the first 5 min of early reperfusion. HG was induced by infusion of glucose 50% (G 50) for 35 min, starting 5 min before ischaemia up to 5 min of reperfusion. CsA (5 or 10 mg kg(-1)) was administered i.v. 5 min before the onset of reperfusion. At the end of the experiments, hearts were excised for infarct size measurements.

RESULTS

Infarct size (% of area at risk) was reduced from 51.4 (5.0)% [mean (sd)] in controls to 32.7 (12.8)% after sevoflurane postconditioning (Sevo-post) (P<0.05). This infarct size reduction was completely abolished by HG [51.1 (13.2)%, P<0.05 vs Sevo-post], but was restored by administration of sevoflurane with CsA [35.2 (5.2)%, P<0.05 vs HG+Sevo-post]. Increased concentrations of sevoflurane or CsA alone could not restore cardioprotection in a state of HG [Sevo-post2, 54.1 (12.6)%, P>0.05 vs HG+Sevo-post; CsA10, 58.8 (11.3)%, P>0.05 vs HG+CsA].

CONCLUSIONS

Sevoflurane-induced postconditioning is blocked by HG. Inhibition of the mPTP with CsA is able to reverse this loss of cardioprotection.

Comparing the organisational structure of the preoperative assessment clinic at eight university hospitals

The preoperative assessment clinic (PAC) has been implemented in most major hospitals. However, there is no uniformity in the way PACs are organised. We compared the organisational structure of the PACs from all eight university hospitals in The Netherlands, looking at the following variables: number of patients visiting the PAC, staffing of the PAC, opening hours, scheduling, and additional preoperative diagnostic testing. The number of patients seen yearly varies from 7.000 to 13.500. In all clinics, the preoperative assessment was performed by anaesthetists and residents. In five PACs, preoperative assessment was also performed by physician assistants or nurse practitioners. Opening hours varied. Consultations are by appointment, 'walk-in', or a combination of these two. In four clinics additional testing is performed at the PAC itself. This study shows that the organisational structure of the PAC at similar university hospitals varies greatly; this can have important implications when designing a benchmarking process.

Patient Experiences with the Preoperative Assessment Clinic (PEPAC): validation of an instrument to measure patient experiences

BACKGROUND

Presently, no comprehensive and validated questionnaire to measure patient experiences of the preoperative assessment clinic (PAC) is available. We developed and validated the Patient Experiences with the Preoperative Assessment Clinic (PEPAC) questionnaire, which can be used for quantitative measurements of patient experiences of the PAC.

METHODS

We adapted the National Health Service outpatient questionnaire, incorporating questions specific for anaesthesiology. To make the PEPAC appropriate for quantitative measurements, dimensions and single items suitable for statistical analysis were constructed. Each dimension consists of multiple items measuring the same aspect of care. Reliability was established by computing Cronbach's alpha coefficients. Construct validity was assessed by correlating the dimensions with the patient's overall appraisal (Pearson's r). These dimensions should explain a substantial level of variance of the patients' overall appraisal; therefore, regression analysis was performed.

RESULTS

After a pilot phase, the questionnaire was sent to 700 consecutive patients (response 74%). Five scales measuring five dimensions of patient experiences were constructed. Cronbach's alpha ranged from 0.56 to 0.84, supporting reliability of the PEPAC. Correlations between the dimensions and patients' overall appraisal ranged from 0.22 to 0.56. Collectively, the five scales explained 51% of patients' overall appraisal.

CONCLUSIONS

The PEPAC is a comprehensive, reliable, and validated questionnaire to measure patient experiences with the PAC. It might be a useful tool to identify the service areas of the PAC that require improvement and to determine which actions can bring about improvement.

Xenon preconditioning differently regulates p44/42 MAPK (ERK 1/2) and p46/54 MAPK (JNK 1/2 and 3) in vivo †

BACKGROUND

Xenon (Xe) induces preconditioning (PC) of the rat heart in vivo via activation of p38 mitogen-activated protein kinase (MAPK). The role of ERK 1/2 and JNK 1/2 and 3 in Xe-PC has yet not been determined.

METHODS

For infarct size measurements, anaesthetized rats were subjected to 25 min of coronary artery occlusion followed by 120 min of reperfusion. Animals received Xe 70% during three 5 min periods with and without the ERK inhibitor PD 98059 (1 mg kg(-1), PD) or the JNK inhibitor SP 600125 (6 mg kg(-1), SP) (n=10 per group). Additional hearts were excised for western blot and kinase activity assay: without further treatment, after the first, the second and the third period of Xe-PC or at the end of the last washout phase (n=4 each).

RESULTS

Infarct size (% of area at risk) was reduced from 46.2 (8.1)% to 28.4 (11.3)% after Xe-PC (P<0.01). PD completely abolished this effect [49.7 (11.4)%, P<0.01 vs Xe-PC]. The ratio of particulate/cytosolic phospho ERK 1/2 was time dependently increased during the PC protocol [ERK 1: 15 min: 2.4 (1.2), 25 min: 1.5 (0.3), 35 min: 1.6 (0.7), 45 min: 1.5 (0.5) vs Con 1.0 (0.5) and ERK 2: 15 min: 3.3 (1.8), 25 min: 2.0 (1.5), 35 min: 1.8 (1.7), 45 min: 0.9 (0.6) vs Con 0.8 (0.4)]. This finding was confirmed by a non-radioactive MAPK activity assay. In contrast SP had no effect on Xe-PC and the phosphorylation state of JNK was not influenced by Xe-PC.

CONCLUSION

Besides the p38 MAPK, ERK 1/2 also is a mediator of Xe-PC. However, JNK is not involved, demonstrating a highly specific regulation of different kinases during Xe-PC.

Effect of sevoflurane preconditioning on ischaemia/reperfusion injury in the rat kidney in vivo

BACKGROUND AND OBJECTIVE

Whereas the protective effect of anaesthetic and ischaemic preconditioning has been described for several organs, it is uncertain whether this mechanism is also effective in the kidney. We compared the effect of preconditioning with sevoflurane and preconditioning with short episodes of ischaemia on renal ischaemia/reperfusion injury in the rat in vivo.

METHODS

Fourteen days after right-sided nephrectomy, anaesthetized male Wistar rats were randomly assigned to a sham-operated group (no arterial occlusion, n = 5) or underwent 45 min of left renal artery occlusion (control group, n = 9) followed by 3 days of reperfusion. Two further experimental groups of animals were preconditioned prior to ischaemia either by administering 1 MAC sevoflurane for 15 min followed by 10 min of washout (sevoflurane group, n = 10) or by subjecting the animals to three short episodes of renal ischaemia (ischaemia-preconditioned group, n = 8). Blood creatinine was measured during reperfusion and morphological damage was assessed by histological examination.

RESULTS

Baseline creatinine values were similar in all four groups (0.7 +/- 0.2 mg dL-1; mean +/- SD) and remained unchanged in the sham-operated animals after 3 days (0.8 +/- 0.2 mg dL-1). Creatinine levels increased in the ischaemic preconditioning group (3.3 +/- 1.2 mg dL-1) and sevoflurane preconditioning group (4.0 +/- 1.1 mg dL-1) compared to the control group (1.6 +/- 0.6 mg dL-1). Morphological damage was less severe in the control group, i.e. in animals without preconditioning, than in both preconditioning groups.

CONCLUSION

Neither sevoflurane nor ischaemic preconditioning preserves renal function or attenuates cell damage in the rat in vivo.

The effect of anaesthetics on the myocardium - new insights into myocardial protection

A variety of laboratory and clinical studies clearly indicate that exposure to anaesthetic agents can lead to a pronounced protection of the myocardium against ischaemia-reperfusion injury. Several changes in the protein structure of the myocardium that may mediate this cardioprotection have been identified. Ischaemia-reperfusion of the heart occurs in a variety of clinical situations including transplantations, coronary artery bypass grafting or vascular surgery. Ischaemia may also occur during a stressful anaesthetic induction. Early restoration of arterial blood flow and measures to improve the ischaemic tolerance of the tissue are the main therapeutic options (i.e. cardioplegia and betablockers). There exists increasing evidence that anaesthetic agents interact with the mechanisms of ischaemia-reperfusion injury and protect the myocardium by a 'preconditioning' and a 'postconditioning' mechanism. Hence, the anaesthesiologist may substantially influence the critical situation of ischaemia-reperfusion during surgery by choosing the appropriate anaesthetic agent. This review summarizes the current understanding of the mechanisms of anaesthetic-induced myocardial protection. In this context, three time windows of anaesthetic-induced cardioprotection are discussed: administration (1) during ischaemia, (2) after ischaemia-during reperfusion (postconditioning) and (3) before ischaemia (preconditioning). Possible clinical implications of these interventions will be reviewed.

Moderate glucose deprivation preconditions myocardium against infarction

Glucose-free perfusion preconditions myocardium against the consequences of subsequent ischemia. We investigated whether mitochondrial ATP-sensitive potassium (mK (ATP)) channels are involved in preconditioning by glucose deprivation, and whether moderate glucose deprivation also preconditions myocardium. Isolated rat hearts underwent 30 min of no-flow ischemia followed by 1 h reperfusion. Controls were not further treated. Three groups were preconditioned by perfusion with 0, 40 or 80 mg/dl (0, 2.22, 4.44 mmol/l) glucose (correction of osmotic pressure by addition of urea) for 10 min followed by 10 min perfusion with normal buffer (150 mg/dl, or 8.33 mmol/l glucose) before the ischemia reperfusion protocol. In one group, 100 micromol/l of the mK (ATP) channel blocker 5-HD was added to the glucose-free perfusate. Two groups were treated with 5-HD or urea before ischemia without preconditioning. Left ventricular developed pressure and maximum ischemic contracture (82 +/- 21 mmHg) were similar in all groups. Mean left ventricular developed pressure was 100 +/- 16 mm Hg under baseline conditions, and poorly recovered to 8 +/- 11 mm Hg during reperfusion. Preconditioning with 0 and 40 mg/dl glucose containing buffer reduced infarct size from 41 +/- 10% (control) to 23 +/- 12% (p = 0.02) and 26 +/- 8% (p = 0.011). The 5-HD blocked preconditioning by glucose deprivation (38 +/- 9%, p = 0.04) while 80 mg/dl glucose, 5-HD and urea had no effect on infarct size (39 +/- 9%; 38 +/- 13%; 37 +/- 8%; p = 1.0 each). We conclude that transient severe glucose deprivation and moderate glucose deprivation preconditions the isolated rat heart. Preconditioning by complete glucose deprivation depends on the opening of mK (ATP) channels.

Haemodynamic changes during halothane, sevoflurane and desflurane anaesthesia in dogs before and after the induction of severe heart failure

BACKGROUND AND OBJECTIVE

The effects of desflurane and sevoflurane on the failing myocardium are still uncertain. We investigated the effects of different concentrations of sevoflurane, desflurane and halothane in dogs with pacing induced chronic heart failure.

METHODS

Global (left ventricular pressure, left ventricular dP/dt, Konigsbergtransducer) and regional myocardial function (systolic segment length shortening, ultrasonic crystals) were measured in chronically instrumented dogs with tachycardia induced severe congestive heart failure. Measurements were performed in healthy dogs and after induction of heart failure in the awake state and during anaesthesia with 0.75, 1.0, 1.25 and 1.75 minimum alveolar concentration (MAC) of halothane, sevoflurane or desflurane.

RESULTS

The anaesthetics reduced dP/dtmax in a dose-dependent manner in healthy dogs (dP/dtmax decreased to 43-53% of awake values at 1.75 MAC). Chronic rapid left ventricular pacing increased heart rate and left ventricular end-diastolic pressure and decreased mean arterial pressure, left ventricular systolic pressure and dP/dtmax. The reduction in contractility was similar in the failing myocardium (to 41-50% of awake values at 1.75 MAC). Segmental shortening was reduced during anaesthesia by 50-62% after pacing compared with 22-44% in normal hearts. While there were similar effects of the different anaesthetics on diastolic function in healthy dogs, after induction of heart failure a more pronounced increase of the time constant of isovolumic relaxation and a greater decrease of dP/dtmin was observed with sevoflurane than with desflurane, indicating a stronger depression of diastolic function.

CONCLUSIONS

While the negative inotropic effects of sevoflurane and desflurane were similar in normal and in the failing myocardium in vivo, desflurane led to a better preservation of diastolic function in the failing myocardium.