Development and feasibility of a Patient Blood Management implementation programme in vascular surgery.

Vascular surgery is the largest (non-cardiac) user of blood transfusion which is associated with increased risk to patients. Patient Blood Management (PBM) is a quality improvement programme in transfusion medicine involving educational change and recommendations through preoperative, operative, and postoperative surgery. We wished to assess the feasibility to implement a PBM programme in vascular surgery. A multidisciplinary programme was developed at a vascular unit by PBM experts. The PBM programme involved a series of educational lectures, consultations, and discussions with doctors, nurses, and theatre staff. A one-page PBM checklist of recommendations was developed for all patients undergoing vascular surgery. Prospective audits were conducted before (October 2014 to March 2015) and after (November 2015 to February 2016) PBM implementation. Outcomes were blood transfusion and haemoglobin concentration (Hb) trigger threshold. A total of 211 patients were admitted under vascular surgery: 127 for Audit 1 and 84 for Audit 2. Overall, 30% of patients were transfused, with 193 units transfused in Audit 1 and 85 in Audit 2. PBM implementation was associated with a reduction in patients receiving a blood transfusion (37% to 20%; p = 0.01). However, there was no difference in Hb trigger threshold (76 g/L vs 72 g/L, p = 0.051). A PBM programme is feasible and can be implemented in vascular surgery. PBM was associated with an improvement in transfusion use and length of patient stay that merits further investigation.

Preoperative intravenous iron before cardiac surgery: a prospective multicentre feasibility study.

BACKGROUND: Preoperative anaemia affects one third of patients undergoing cardiac surgery and is associated with increased mortality and morbidity. Although it is recommended that perioperative teams should identify and treat patients with preoperative anaemia before surgery, introducing new treatment protocols can be challenging in surgical pathways. The aim of this study was to assess the feasibility and effectiveness of introducing a preoperative intravenous iron service as a national initiative in cardiac surgery. METHODS: We performed a multicentre, stepped, observational study using the UK Association of Cardiothoracic Anaesthesia and Critical Care Research Network. The primary feasibility outcome was the ability to set up an anaemia and intravenous iron clinic at each site. The primary efficacy outcome was change in haemoglobin (Hb) concentration between intervention and operation. Secondary outcomes included blood transfusion and hospital stay. Patients with anaemia were compared with non-anaemic patients and with those who received intravenous iron as part of their routine treatment protocol. RESULTS: Seven out of 11 NHS hospitals successfully set up iron clinics over 2 yr, and 228 patients were recruited into this study. Patients with anaemia who received intravenous iron were at higher surgical risk, were more likely to have a known previous history of iron deficiency or anaemia, had a higher rate of chronic kidney disease, and were slightly more anaemic than the non-treated group. Intravenous iron was administered a median (inter-quartile range, IQR [range]) of 33 (15-53 [4-303]) days before surgery. Preoperative intravenous iron increased [Hb] from baseline to pre-surgery; mean (95% confidence interval) change was +8.4 (5.0-11.8) g L-1 (P<0.001). Overall, anaemic compared with non-anaemic patients were more likely to be transfused (49% [59/136] vs 27% (22/92), P=0.001) and stayed longer in hospital (median days [IQR], 9 [7-15] vs 8 [6-11]; P=0.014). The number of days alive and at home was lower in the anaemic group (median days [IQR], 20 [14-22] vs 21 [17-23]; P=0.033). CONCLUSION: The development of an intravenous iron pathway is feasible but appears limited to selected high-risk cardiac patients in routine NHS practise. Although intravenous iron increased [Hb], there is a need for an appropriately powered clinical trial to assess the clinical effect of intravenous iron on patient-centred outcomes.

The Association Between Pulsatile Cardiopulmonary Bypass and Acute Kidney Injury After Cardiac Surgery: A Before-and-After Study.

OBJECTIVES: To investigate the association between pulsatile perfusion and cardiac surgery-associated acute kidney injury. DESIGN: An uncontrolled, retrospective before-and-after study. SETTING: Single tertiary hospital. PARTICIPANTS: A total of 2,489 patients undergoing cardiac surgery with cardiopulmonary bypass (CPB). INTERVENTIONS: Pulsatile versus nonpulsatile perfusion. MEASUREMENTS AND MAIN RESULTS: Data for nonpulsatile perfusion was collected from April 1, 2016, to March 31, 2017 (n = 1,223). A practice change to universal pulsatile CPB occurred on April 3, 2017. Data for pulsatile perfusion was collected from May 1, 2017, to June 30, 2018 (n = 1,266). The primary outcome was the incidence of acute kidney injury (AKI) after cardiac surgery. Multivariable analysis was carried out to adjust for known confounders. Secondary outcomes included AKI stage, stroke, length of stay, and mortality. Subgroup analyses were carried out using prolonged CPB and chronic kidney disease. The primary outcome, incidence of AKI, did not differ between the nonpulsatile control group and the pulsatile group (23.9% v 25.4%, p = 0.392). The pulsatile group was not associated with AKI in the multivariable analysis (Odds ratio 1.09, p = 0.413). There were no differences in stages of AKI in the nonpulsatile group v pulsatile group (13.6% v 14.9%, 2.9% v 4.3%, and 7.4% v 6.1% for stages 1, 2, and 3, respectively, p = 0.12). There were no differences in subgroup analyses or secondary outcomes. CONCLUSIONS: There was no association found between kidney injury and pulsatile perfusion. It is likely that there is either no association between pulsatile perfusion and reduced kidney injury or that the difference is extremely small.

The Effects of Escalation of Respiratory Support and Prolonged Invasive Ventilation on Outcomes of Cardiac Surgical Patients: A Retrospective Cohort Study.

OBJECTIVES: The aim of this study was to determine the effects of escalation of respiratory support and prolonged postoperative invasive ventilation on patient-centered outcomes, and identify perioperative factors associated with these 2 respiratory complications. DESIGN: A retrospective cohort analysis of cardiac surgical patients admitted to the cardiothoracic intensive care unit (ICU) between August 2015 and January 2018. Escalation of respiratory support was defined as "unplanned continuous positive airway pressure," "non-invasive ventilation," or "reintubation" after surgery; prolonged invasive ventilation was defined as "invasive ventilation beyond the first 12 hours following surgery." The primary endpoint was the composite of escalation of respiratory support and prolonged ventilation. SETTING: Tertiary cardiothoracic ICU. PARTICIPANTS: A total of 2,098 patients were included and analyzed. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The composite of escalation of support or prolonged ventilation occurred in 509 patients (24.3%). Patients who met the composite had higher mortality (2.9% v 0.1%; p < 0.001) and longer median [interquartile range] length of ICU (2.1 [1.0-4.9] v 0.9 [0.8-1.0] days; p < 0.0001) and hospital (10.6 [8.0-16.0] v 7.2 [6.2-10.0] days; p < 0.0001) stay. Hypoxemia and anemia on admission to ICU were the only 2 factors independently associated with the need for escalation of respiratory support or prolonged invasive ventilation. CONCLUSIONS: Escalation of respiratory support or prolonged invasive ventilation is frequently seen in cardiac surgery patients and is highly associated with increased mortality and morbidity. Hypoxemia and anemia on admission to the ICU are potentially modifiable factors associated with escalation of respiratory support or prolonged invasive ventilation.

Systematic review and consensus definitions for the Standardised Endpoints in Perioperative Medicine (StEP) initiative: infection and sepsis.

BACKGROUND: Perioperative infection and sepsis are of fundamental concern to perioperative clinicians. However, standardised endpoints are either poorly defined or not routinely implemented. The Standardised Endpoints in Perioperative Medicine (StEP) initiative was established to derive a set of standardised endpoints for use in perioperative clinical trials. METHODS: We undertook a systematic review to identify measures of infection and sepsis used in the perioperative literature. A multi-round Delphi consensus process that included more than 60 clinician researchers was then used to refine a recommended list of outcome measures. RESULTS: A literature search yielded 1857 titles of which 255 met inclusion criteria for endpoint extraction. A long list of endpoints, with definitions and timescales, was generated and those potentially relevant to infection and sepsis circulated to the theme subgroup and then the wider StEP-COMPAC working group, undergoing a three-stage Delphi process. The response rates for Delphi rounds 1, 3, and 3 were 89% (n=8), 67% (n=62), and 80% (n=8), respectively. A set of 13 endpoints including fever, surgical site, and organ-specific infections as defined by the US Centres for Disease Control and Sepsis-3 are proposed for future use. CONCLUSIONS: We defined a consensus list of standardised endpoints related to infection and sepsis for perioperative trials using an established and rigorous approach. Each endpoint was evaluated with respect to validity, reliability, feasibility, and patient centredness. One or more of these should be considered for inclusion in future perioperative clinical trials assessing infection, sepsis, or both, thereby permitting synthesis and comparison of future results.

Evaluation of the Clinical Utility of Transesophageal Echocardiography and Invasive Monitoring to Assess Right Ventricular Function During and After Pulmonary Endarterectomy.

OBJECTIVE: Patients undergoing pulmonary endarterectomy (PEA) have impaired right ventricular function. The authors sought to assess the clinical utility of commonly used perioperative echocardiographic and right heart catheter measurements in patients undergoing PEA. DESIGN: A single-center prospective observational study. SETTING: The study was conducted in a quaternary care cardiac surgical center in the United Kingdom. PARTICIPANTS: Patients undergoing PEA between April 2015 and January 2016. INTERVENTIONS: Thermodilution cardiac index and echocardiography variables were measured at 3 time points: before sternotomy (T1), after pericardial incision (T2), and after sternal closure (T3). Six-month follow-up echocardiography and 6-minute walk (6-MWT) test were performed. MEASUREMENTS AND MAIN RESULTS: Fifty patients were recruited and complete data sets were available for 41 patients. Tricuspid annular plane systolic excursion declined after pericardial incision and cardiopulmonary bypass (T1: 15 ± 4 mm, T2: 13 ± 4 mm, T3: 7 ± 2 mm; p < 0.0001), returning to baseline 6 months postoperatively. Cardiac index (T1: 2.5 ± 0.7 L/min/m2, T2: 2.6 ± 0.6 L/min/m2, T3: 2.3 ± 0.5 L/min/m2; p = 0.07) and right ventricular fractional area change (T1: 36 ± 11%, T2: 40 ± 12%, T3: 40 ± 9%; p = 0.12) were preserved perioperatively. 6-MWT improved from baseline (294 ± 111 m) to follow-up (357 ± 107 m) (p < 0.001). Pulmonary vascular resistance at T3 correlated moderately with follow-up 6-MWT (R = -0.60). CONCLUSIONS: In patients undergoing PEA, invasive measurements and echocardiography assessment of right ventricular function are not interchangeable. Tricuspid annular plane systolic excursion is not a reliable measure of right ventricular function perioperatively. Pulmonary vascular resistance shows moderate correlation with postoperative functional capacity.

Does the "Weekend Effect" for Postoperative Mortality Stand Up to Scrutiny? Association for Cardiothoracic Anesthesia and Critical Care Cohort Study of 110,728 Cardiac Surgical Patients.

OBJECTIVE: Ongoing debate focuses on whether patients admitted to the hospital on weekends have higher mortality than those admitted on weekdays. Whether this apparent "weekend effect" reflects differing patient risk, care quality differences, or inadequate adjustment for risk during analysis remains unclear. This study aimed to examine the existence of a "weekend effect" for risk-adjusted in-hospital mortality after cardiac surgery. DESIGN: Retrospective analysis of prospectively collected cardiac registry data. SETTING: Ten UK specialist cardiac centers. PARTICIPANTS: A total of 110,728 cases, undertaken by 127 consultant surgeons and 190 consultant anesthetists between April 2002 and March 2012. INTERVENTIONS: Major risk-stratified cardiac surgical operations. MEASUREMENTS AND MAIN RESULTS: Crude in-hospital mortality rate was 3.1%. Multilevel multivariable models were employed to estimate the effect of operative day on in-hospital mortality, adjusting for center, surgeon, anesthetist, patient risk, and procedure priority. Weekend elective cases had significantly lower mortality risk compared to Monday elective cases (odds ratio [OR] 0.64, 95% confidence interval [CI] 0.42, 0.96) following risk adjustment by the logistic European System for Cardiac Operative Risk Evaluation (EuroSCORE) and procedure priority; differences between weekend and Monday for urgent and emergency/salvage cases were not significant (OR 1.12, 95% CI 0.73, 1.72, and 1.07, 95% CI 0.79, 1.45 respectively). Considering only the logistic EuroSCORE but not procedure priority yielded 29% higher odds of death for weekend cases compared to Monday operations (OR 1.29, 95% CI 1.08, 1.54). CONCLUSIONS: This study suggests that undergoing cardiac surgery during the weekend does not affect negatively patient survival, and highlights the importance of comprehensive risk adjustment to avoid detecting spurious "weekend effects."

Enhanced recovery for thoracic surgery in the elderly.

PURPOSE OF REVIEW: Both surgical workload and the age of those patients being considered for radial pulmonary resection are increasing. Enhanced recovery programmes are now well established in most surgical disciplines and are increasingly reported in thoracic procedures. This review will discuss the relevant principles of these programmes as applied to an increasing elderly population. RECENT FINDINGS: Elderly patients undergoing less radial surgical resections without lymphadenectomy have comparable outcomes to those undergoing classical curative treatment. Patients require careful assessment and self-reported quality of life metrics or function may be a better marker of outcome than static measures such as lung function. Hypotension, low values for bispectral index and low anaesthetic gas mean alveolar concentration values are common and independent predictors of mortality in the elderly. Paravertebral blockade is preferred to epidural anaesthesia because of a more favourable side-effect profile and comparable efficacy. As yet no robust work has examined the efficacy of an integrated enhanced recovery programme in thoracic surgery. SUMMARY: Elderly patients are suitable for enhanced recovery programmes but these must be tailored to individual circumstance. Further work is required to comprehensively assess their value in a modern healthcare setting.

Insidious Risk of Severe Mycobacterium chimaera Infection in Cardiac Surgery Patients.

BACKGROUND: An urgent UK investigation was launched to assess risk of invasive Mycobacterium chimaera infection in cardiothoracic surgery and a possible association with cardiopulmonary bypass heater-cooler units following alerts in Switzerland and The Netherlands. METHODS: Parallel investigations were pursued: (1) identification of cardiopulmonary bypass-associated M. chimaera infection through national laboratory and hospital admissions data linkage; (2) cohort study to assess patient risk; (3) microbiological and aerobiological investigations of heater-coolers in situ and under controlled laboratory conditions; and (4) whole-genome sequencing of clinical and environmental isolates. RESULTS: Eighteen probable cases of cardiopulmonary bypass-associated M. chimaera infection were identified; all except one occurred in adults. Patients had undergone valve replacement in 11 hospitals between 2007 and 2015, a median of 19 months prior to onset (range, 3 months to 5 years). Risk to patients increased after 2010 from <0.2 to 1.65 per 10000 person-years in 2013, a 9-fold rise for infections within 2 years of surgery (rate ratio, 9.08 [95% CI, 1.81-87.76]). Endocarditis was the most common presentation (n = 11). To date, 9 patients have died. Investigations identified aerosol release through breaches in heater-cooler tanks. Mycobacterium chimaera and other pathogens were recovered from water and air samples. Phylogenetic analysis found close clustering of strains from probable cases. CONCLUSIONS: We identified low but escalating risk of severe M. chimaera infection associated with heater-coolers with cases in a quarter of cardiothoracic centers. Our investigations strengthen etiological evidence for the role of heater-coolers in transmission and raise the possibility of an ongoing, international point-source outbreak. Active management of heater-coolers and heightened clinical awareness are imperative given the consequences of infection.

Intubated Versus Nonintubated General Anesthesia for Video-Assisted Thoracoscopic Surgery-A Case-Control Study.

OBJECTIVE: General anesthesia with endobronchial intubation and one-lung positive-pressure ventilation always has been considered mandatory for thoracic surgery. Recently, there has been interest in nonintubated techniques for video-assisted thoracoscopic surgery (VATS) in awake and sedated patients. The authors' center developed a nonintubated technique with spontaneous ventilation with the patient under general anesthesia using a supraglottic airway device. The authors believe that this was the first study to compare a nonintubated general anesthetic technique with an intubated general anesthetic technique for VATS. DESIGN: Retrospective, observational study. SETTING: Specialist cardiothoracic hospital in the United Kingdom. PARTICIPANTS: All patients who underwent elective minor VATS over 8 months (n = 73). INTERVENTIONS: A nonintubated general anesthetic technique with spontaneous ventilation via a supraglottic airway device was used for minor VATS procedures. This was compared with a case-matched intubated group. MEASUREMENTS AND MAIN RESULTS: Both groups had comparable baseline characteristics and surgical procedures. The anesthetic time was shorter in the nonintubated group (13.6±8.3 v 24.1±10.9 minutes, p<0.001). Surgical operating time and feasibility were similar. Intraoperatively, there were increases in end-tidal carbon dioxide (59.1±12.9 v 41.8±4.6, p<0.001) and respiratory rate (17.8±5.6 v 13.5±2.0, p<0.001) in the nonintubated group. Fewer patients in the nonintubated group had moderate-severe pain during recovery (19.4% v 48.4%, p = 0.02) and pain on discharge to the ward (25.8% v 61.3%, p = 0.004). There was a trend toward shorter recovery times, reduced oxygen requirement, and shorter hospital stays in the nonintubated group. CONCLUSIONS: A nonintubated general anesthetic technique is a feasible alternative to intubated general anesthesia for minor VATS procedures.

Acute Pain and Analgesic Requirements After Pulmonary Endarterectomy With Deep Hypothermic Circulatory Arrest.

OBJECTIVES: To assess postoperative pain intensity and the analgesic requirements in the postoperative period in patients undergoing sternotomy for pulmonary endarterectomy involving deep hypothermic circulatory arrest. DESIGN: Retrospective cohort study. SETTING: Single-center hospital study. PARTICIPANTS: Patients 18 years and older undergoing sternotomy for cardiac surgery between August 2012 and August 2014. INTERVENTIONS: No modification to usual clinical practice. MEASUREMENTS AND MAIN RESULTS: Intraoperative opioid and steroid administration, referral to the chronic pain unit, intensive care unit pain scores, and analgesic administration in the first 48 hours after the admission to the intensive care unit were recorded. Postoperative pain was evaluated by means of a categoric verbal scale from no pain (0) to severe pain (3); this is the routine analgesic scale used in the authors' intensive care unit. A total of 200 consecutive patients undergoing pulmonary endarterectomy (PEA group) were included in the study. No patient in the PEA group received morphine during surgery. The mean (standard deviation) postoperative pain intensity score at 24 hours was 0.30 (0.54) in the PEA group. Postoperative morphine was administered in 39% of patients. No PEA patient was referred to the chronic pain unit after hospital discharge. CONCLUSION: The total analgesic requirements and pain score of patients undergoing sternotomy for pulmonary endarterectomy with deep hypothermic circulatory arrest seemed to be low.

An exploratory cohort study comparing prothrombin complex concentrate and fresh frozen plasma for the treatment of coagulopathy after complex cardiac surgery.

BACKGROUND: Administration of coagulation factor concentrates to treat bleeding after cardiac surgery with cardiopulmonary bypass might be a strategy for reducing allogeneic blood transfusions, particularly for patients treated with warfarin preoperatively. We performed an exploratory analysis on whether the use of prothrombin complex concentrate (PCC) is safe and effective compared with fresh frozen plasma (FFP) to treat coagulopathy after pulmonary endarterectomy surgery with deep hypothermic circulatory arrest. METHODS: Consecutive adult patients who underwent pulmonary endarterectomy surgery between January 2010 and September 2012 and received PCC or FFP to treat coagulopathy were studied. Blood loss during the first 12 hours of admission to the intensive care unit and patient outcomes were compared with propensity score adjustment. RESULTS: Three hundred fifty-one patients underwent pulmonary endarterectomy surgery, all of whom had warfarin discontinued for up to 5 days before surgery; bleeding complications requiring transfusion of blood products were observed in 108 (31%) patients. Of those, 55 received only FFP and 45 received only PCC, whereas 8 received both. Blood loss was significantly greater in the FFP group compared with the PCC group after 12 hours (median [interquartile range], 650 mL [325-1075] vs 277 mL [175-608], P = 0.008). However, there was no difference in the frequency of patients receiving a red blood cell transfusion (number [percent], 44 [80%] vs 34 [76%], P = 0.594) or in the number of units of red blood cells transfused (median [interquartile range], 2 [1-4] vs 3 [1-5] units, P = 0.181). The final propensity score included preoperative international normalized ratio, postoperative activated partial thromboplastin time, and postoperative platelet count. After inclusion of the propensity score in the regression analyses, there were no differences between patients receiving only PCC and patients receiving only FFP in the need for renal replacement therapy (odds ratio [OR] 2.39, 95% confidence interval [CI] 0.51-11.20, P = 0.27), 30-day-mortality (OR 0.32, 95% CI 0.03-3.36, P = 0.35), intracranial hemorrhage (OR 0.73, 95% CI 0.14-3.89, P = 0.71), hospital length of stay (hazard ratio 0.77, 95% CI 0.50-1.19, P = 0.24), or duration of intensive care stay (hazard ratio 0.91, 95% CI 0.59-1.40, P = 0.66). CONCLUSIONS: This retrospective analysis suggests that PCC may be an alternative to FFP in patients previously treated with warfarin who are coagulopathic after major cardiac surgery. Randomized controlled studies powered to evaluate efficacy and important postoperative outcomes for patients receiving PCC versus FFP for coagulopathic bleeding after cardiopulmonary bypass are warranted.

Controversies and complications in the perioperative management of transcatheter aortic valve replacement.

Transcatheter aortic valve replacement (TAVR) is performed with increasing frequency in the United States since Food and Drug Administration approval in 2011. The procedure involves the replacement of a severely stenosed native or bioprosthetic aortic valve with a specially constructed valvular prosthesis that is mounted onto a stent, without the use of cardiopulmonary bypass and the complications of a major open surgical procedure. TAVR has been performed mostly in elderly patients with multiple comorbidities or who have undergone previous cardiac surgery. The most commonly used access routes are the femoral artery (transfemoral) or the cardiac apex (transapical), but the transaortic and transubclavian approaches are also used with varying frequency. Conscious sedation may be used in patients undergoing transfemoral TAVR, but the use of general anesthesia has not been shown to carry greater risk and permits the use of transesophageal echocardiography to assist in valve positioning and diagnose complications. Cardiovascular instability during TAVR is relatively common, necessitating invasive monitoring and frequent use of vasoactive medications. Complications of the procedure are still relatively common and the most frequent is vascular injury to the access sites or the aorta. Cardiovascular collapse may be the result of major hemorrhage pericardial effusion with tamponade or coronary occlusion due to incorrect valve placement. Persistent hypotension, myocardial stunning, or injury requiring open surgical intervention may necessitate the use of cardiopulmonary bypass, the facilities for which should always be immediately available. Ongoing and planned trials comparing conventional surgery with TAVR in lower risk and younger patients should determine the place of TAVR in the medium- to long-term future.

The effect of adjusting tracheal tube cuff pressure during deep hypothermic circulatory arrest: a randomised trial.

BACKGROUND: Regular endotracheal tube cuff monitoring may prevent silent aspiration. OBJECTIVES: We hypothesised that active management of the cuff of the tracheal tube during deep hypothermic cardiac arrest would reduce silent subglottic aspiration. We also determined to study its effect on postoperative mechanical ventilation and the incidence of postoperative positive tracheal cultures. DESIGN: A randomised clinical trial. SETTING: The study was conducted in a University Teaching Hospital from September 2008 to November 2009. PATIENTS: Twenty-four patients undergoing elective pulmonary endarterectomy were included in the study. INTERVENTION: After induction of general anaesthesia and tracheal intubation, the cuff of the tracheal tube was inflated to 25 cmH2O. Following this, 1 ml of methylene blue dye diluted in 2 ml of physiological saline was injected into the hypopharynx. Patients were randomly assigned to active cuff management during cooling and warming (where cuff pressure was monitored and the cuff was reinflated if it dropped below 20 cmH2O, or deflated if pressure exceeded 30 cmH2O) or passive monitoring (where cuff pressure was monitored but volume was not altered). Before weaning from cardiopulmonary bypass, fibreoptic bronchoscopy was performed. Silent aspiration was then diagnosed if blue dye was seen in the trachea below the cuff of the tube. MAIN OUTCOME MEASURES: The primary aim of this study was to determine the incidence of silent aspiration. Secondary outcomes included duration of postoperative mechanical ventilation of the lungs and incidence of positive culture of tracheal aspirate. RESULTS: Active cuff management patients were younger than controls (51.2 ±â€Š11.6 vs. 63.2 ±â€Š9 years, P = 0.028), but otherwise the two groups were similar. The primary endpoint was reached because we showed that silent aspiration was significantly less frequent in the study group (0/12 vs. 8/12 patients, P = 0.001). Significantly lower intracuff pressures were measured in the control group patients at several timepoints during cooling, just before hypothermic arrest and at all timepoints during rewarming. CONCLUSION: We recommend that the cuff of the tracheal tube should be checked regularly during surgery under deep hypothermia, and the cuff pressure adjusted as required.

Point-of-care assessment of hypothermia and protamine-induced platelet dysfunction with multiple electrode aggregometry (Multiplate®) in patients undergoing cardiopulmonary bypass.

BACKGROUND: Coagulopathy is common after cardiopulmonary bypass (CPB), and platelet dysfunction is frequently considered to be a major contributor to excessive bleeding. Exposure to hypothermia may exacerbate the platelet function defect. We assessed platelet function during and after deep hypothermia with multiple electrode aggregometry (Multiplate(®); Verum Diagnostica GmbH, Munich, Germany). METHODS: Twenty adult patients undergoing pulmonary endarterectomy for chronic pulmonary hypertension were cooled on CPB to 20°C and deep hypothermic arrest was used to facilitate surgery. We analyzed platelet aggregation in whole blood samples at 12 measuring points during and after the procedure. Platelet aggregation was stimulated via the thrombin receptor (TRAPtest) at the patient's actual body temperature (AUC-CT) and after rewarming the samples to 37°C (AUC-37). In addition, we tested samples at 2 time points after 2 minutes of in vitro incubation with 20 µg protamine (0.067 µg/µL). Results are expressed as area under the aggregation curve (AUC). RESULTS: Cooling resulted in a marked decrease of platelet aggregation to a minimum AUC-CT of 20.5 (95% confidence interval [CI] 8.9-32.1) at 20°C body temperature. AUC-CT was significantly different from baseline (92.8, 95% CI 82.5-103.1) for temperatures of ≤28°C (P < 0.001), whereas the change in AUC-37 only became significant at the lowest body temperature (59.4, 95% CI 41.3-77.4). After rewarming to 36°C, AUC-CT and AUC-37 had recovered to 67.6 (95% CI 53.9-81.3) and 71.7 (95% CI 52.5-90.8), respectively. The mean AUC-CT was significantly lower than the mean AUC-37 from cooling at 28°C to warming at 24°C inclusive, and the relationship with temperature during cooling was significantly different between AUC-CT and AUC-37 (regression coefficients 4.7 [95% CI 4.2-5.2] vs 1.3 [95% CI 0.7-1.9]; P < 0.0001). After administration of protamine, mean aggregation decreased significantly for both measurements by 38.2 (95% CI -27.9 to -48.5; P < 0.001) and 44.5 (95% CI -58.5 to -30.5; P < 0.001), respectively. Similarly, adding protamine in vitro resulted in a decrease of mean aggregation by 35.1 (95% CI -71.0 to 0.8; P = 0.055) when measured after administration of heparin, and 56.5 (95% CI -94.5 to -18.5; P = 0.005) at the end of CPB. CONCLUSION: Platelet aggregation, assessed by multiple electrode aggregometry (Multiplate), was severely affected during deep, whole-body hypothermia. This effect was partially reversible after rewarming, and was distinct from a general decline of platelet aggregation during CPB. Protamine also caused a significant decrease in platelet aggregation in vivo and in vitro.