Adequate Tissue Perfusion Research Articles

Postoperative fluid management in major elective plastic surgery

To document the current practice of postoperative fluid management and evaluate its effectiveness in major elective plastic surgery. We conducted a retrospective review on consecutive adult patients undergoing major elective plastic surgery necessitating intensive care unit or high dependency unit admission between May 2005 and May 2007. Hourly fluid input, output and vital signs were recorded for the first 48h postoperatively. Hourly urine output was used as a measure of adequacy of tissue perfusion with 0.5-1.5mlkg(-1)h(-1) being considered normal. Urine output outside of this range for more than four consecutive hours was considered clinically abnormal. These measurements were related temporally to any adjustment of the rates of fluid administration. Intra-operative balance and daily total fluid balance were recorded. Twenty-four out of 85 patients were excluded because of pre-existing renal impairment (n=12), regular diuretic use (n=8) or incomplete documentation (n=4). No patients had pre-existing cardiac failure. The mean intra-operative positive fluid balance was 3687ml (range 1300-8711), with a mean cumulative volume of 4522ml (range 2560-9465) on postoperative day 1 and this increased with the length of hospital stay. A brisk diuresis (range 1.5-9.0; mean, 3.6mlkg(-1)h(-1)) occurred in 41 (67%) patients, half of them within 7h postoperatively. 26 (43%) patients received excessive fluid, which were responded to within 1-31h (mean 13.5). Six (10%) patients developed cardiac failure, requiring fluid restriction and/or diuretics. Patients undergoing major elective plastic surgery are in massive positive fluid balance. Majority of these patients develop a brisk diuresis in the early postoperative period. Current practice centres on preventing oliguria, often with excessive and unnecessary fluid being administered resulting in cardiac failure in some patients. Postoperative fluid management should be guided by a protocol with minimal fluid administration that maintains adequate tissue perfusion, guided by lower and upper limits of desirable urine output. The rates of fluid administration should be adjusted dynamically by the surgical or the nursing staff using such a protocol.

Invited Commentary

The use of arteriovenous extracorporeal membrane oxygenation (ECMO), as an extended measure of cardiopulmonary resuscitation, also known as E-CPR, has a definite role; however, it is small and ill defined. In patients where cardiac recovery is anticipated, it is an unpredictable and unknown entity. Often, this is a bridging option to either a transplant or a more definitive mechanical assist device, which in itself may be a further bridge to transplantation or destination therapy. The ease and speed with which this can be instituted with percutaneous cannulation (borrowed from port access techniques), offers its appealing advantage. Patients treated with E–CRP progress through three distinct phases during their treatment. The first phase involves technical and circulatory issues. Placement of an appropriate sized venous cannula and establishing adequate tissue perfusion should achieve metabolic resuscitation within a few hours. The second phase involves inflammation, characterized by a complete whiteout of the lung fields. Avoiding high fractional inspiratory oxygen (FiO2) and high positive end-expiratory pressure on nonfunctional lungs will facilitate recovery. Renal dysfunction in those with marginal renal status will require filtration through the circuit or dialysis as a supportive measure. The third phase involves infection and end-organ failure. Proactive regular surveillance cultures from the circuit and the patient are required, along with broad spectrum antibiotics and antifungals as appropriate. Heparin resistance and sensitivity are not unusual and need vigilance during ECMO management. Regular neurologic assessment with clinical and radiologic means is important in all of these patients. In this study, Dr Thiagarajan and colleagues [1Thiagarajan R.R. Brogan T.V. Scheurer M.A. Laussen P.C. Rycus P.T. Bratton S.L. Extracorporeal membrane oxygenation to support cardiopulmonary resuscitation in adults.Ann Thorac Surg. 2009; 87: 778-785Abstract Full Text Full Text PDF PubMed Scopus (213) Google Scholar], present a comprehensive audit of the outcomes in 295 patients. The findings are supportive of the experience in the centers that undertake this intervention. The use of ECMO has increased in recent years, although not with improved outcomes. This reflects on the willingness of the centers to be aggressive toward managing their patients. Further studies will help in patient selection in the future. Neurologic injury, sepsis, and multiorgan failure are the nemesis of this treatment. Even though this study could not evaluate the impact of large volume centers, it is reasonable to expect that large volume centers have more to offer toward better outcomes. With a growing need and increasing expertise of most centers in providing mechanical circulatory assist devices, I see a more definitive role for E-CRP evolving in the future. Extracorporeal Membrane Oxygenation to Support Cardiopulmonary Resuscitation in AdultsThe Annals of Thoracic SurgeryVol. 87Issue 3PreviewExtracorporeal membrane oxygenation (ECMO) to support cardiopulmonary resuscitation (CPR) has been shown to improve survival in children and adults. We describe outcomes after the use of ECMO to support CPR (E-CPR) in adults using multiinstitutional data from the Extracorporeal Life Support Organization (ELSO) registry. Full-Text PDF

Septic shock resuscitation: what goals and how to achieve them?

The need to achieve adequate tissue oxygen delivery early in patients with septic shock is well established. However, it is less well recognized that tissue hypoperfusion can exist despite normalization of systemic hemodynamics. Efforts to resuscitate septic patients until adequate tissue perfusion has been achieved can potentially improve outcome. In a multicenter study, 130 patients with septic shock were resuscitated within 12 hours of diagnosis using a protocol including goals for mean arterial and pulmonary artery occluded pressures, urinary output, arterial pH, and hemoglobin goals. They were then randomly assigned to further resuscitation with either a cardiac index (≥ 3 l/minute per m2) or a gastric mucosal pH (≥ 7.32) target. The intensive care unit length of stay and 28-day mortality did not differ between groups, but more patients in the cardiac index group were in the target range, both at baseline and after resuscitation, as compared with the gastric mucosal pH group. In contrast to cardiac index, gastric mucosal pH at baseline and at 24 and 48 hours predicted mortality. Whether other targets for the chosen variables, or different and – in particular – earlier resuscitation efforts would have favored one group cannot be concluded from the data provided.

Probing the limits of regional tissue oxygenation measures

Assessment of tissue health is the Holy Grail in determining whether patients are in shock and when resuscitation efforts can be stopped because recovery has occurred. Tissue health, itself, results from the complex interaction between cardiac pump function, circulating blood volume and vasomotor tone, the number of capillary units perfused, and the ability of the tissue to use the delivered oxygen. Although the macro-circulation seems well evaluated both invasively and non-invasively using measures of blood pressure, cardiac output and mixed venous oxygen saturation, some studies suggest that resuscitation aiming only towards macrocirculatory parameters might be insufficient to improve tissue perfusion. Presently, there are neither generally accepted measures of global tissue viability nor reasonable leading candidate measures on the horizon. For example, although the strong ion gap assessment of metabolic acidosis predicts mortality in trauma patients, it cannot be used to assess response to therapy because crystalloid resuscitation itself alters the strong ion gap [1]. Furthermore, although regional measures of metabolism such as the sublingual tissue partial pressure of carbon dioxide [2] and urethral mucosal NAD/NADH ratios [3] track circulatory deficiency and resuscitation, their ability to assess the global status and their intrinsically highly unstable baseline values make their routine clinical use limited. Non-invasive continuous measurements of tissue hemoglobin oxygenation using near-infrared spectroscopy have been studied and proposed to assess tissue hypoperfusion. The absolute tissue oxygen saturation (StO2) has been proven to be instrumental in predicting outcome in trauma patients [4] but is otherwise relatively insensitive to define earlier stages of tissue hypoperfusion, despite adequate macrocirculation resuscitation aiming to prevent ischemic organ injury. The use of continuous StO2 as a marker of tissue perfusion is still being studied, however, and potentially may demonstrate greater sensitivity early on in trauma resuscitation. Increased interest in functional hemodynamic monitoring [5], for which the fluid challenge or exercise stress test are classic examples, has recently been applied since observed static numbers cannot really evaluate the adequacy of tissue perfusion, especially regional measures of blood flow and tissue viability. Although systemic hypotension with hypoperfusion, a low mixed venous oxygen saturation and elevated serum lactate levels may be used to identify tissue ischemia, normal blood pressure, flow rates, mixed venous oxygen saturation and lactate levels do not ensure the adequacy of resuscitation. In this regard, the use of a transient vascular occlusion test (VOT) to assess StO2 responses has gained increasing interest. The use of an ischemic challenge, or VOT, has further improved and expanded its predictive ability to scenarios such as trauma, severe sepsis and septic shock [6-8]. The VOT is a provocative test in which StO2 is measured on a distal site, such as the thenar eminence, whilst a transient rapid vascular occlusion is performed, using a sphygmomanometer, for either a defined time interval (for example, 3 minutes) or until the StO2 decreases to a defined minimal threshold. Following this, the vascular occlusion is released and the StO2 is allowed to recover. Several emergent parameters arise from this technique, including the rate of deoxygenation (thought to reflect the local metabolic rate), the rate of reoxygenation (thought to reflect local cardiovascular reserve and microcirculatory flow), and the postobstructive hyperemic response. The VOT has not been standardized, however, and has to be better characterized before making a decision on its relevance. Specifically, StO2 can be measured at different anatomical sites (thenar, forearm, deltoid), using different near-infrared spectroscopy probe sizes (15 mm vs. 25 mm) and different types and levels of ischemic deflation thresholds or ischemic times. Information is reported in the present issue on methodological issues such as depth for measurement, different modes of VOT, and determinants of VOT abnormalities. Finally, the StO2 behavior in different disease states and forms of resuscitation and the associate VOT parameters have not been defined. Given the non-invasive and potentially automated nature of StO2 and the VOT, respectively, if these measures are proven useful in clinical decision-making, then their impact on overall resuscitation management would be great. The present supplement to Critical Care aims to address several aspects of these issues, from defining the basic physics of near-infrared spectroscopy and the VOT to clinical studies further exploring the potential of this technique in different patient groups. As with all new technologies applied to the clinical sphere, it is mandatory to identify their operating characteristics and limitations before extending their measures to patient care. Following that, it is always useful to remember that no monitoring device - no matter how insightful its data - will improve patient outcome unless coupled with a treatment that improves outcome.

Reply to Letter: Agreed: “PRAM May be Useful to Assess the Cardiovascular Changes in Obese Patients During Laparoscopy”

To the Editor: I thank Dr. Forfori et al. for their critique of my commentary [1], but certain statements presented by them as fact must be clarified. First, notwithstanding an inherent reproducibility error of ±15–20% [2], pulmonary artery thermodilution cardiac output (TDCO) provides mean values at normal cardiac indices that agree with other reference standards. Fact: thermodilution is still the clinical gold-standard which all pretenders of equivalence must mimic. Other methods, if to be accepted as an equivalent or replacement for TDCO, must provide a small bias and reproducibility error, and limits of agreement within ±30%. In the face of this, Forfori et al. trivialize the studies of Nguyen et al. [3] and Artuso et al. [4], which both used TDCO as their test method to determine CO and the derived indices of cardiac index (CI) stroke volume SV, stroke index (SI) and systemic vascular resistance (SVR) and SVRI. Alleging equivalence to TDCO, the authors emphasize that their results for SV are similar to those of Dumont et al. [5], which are, on the mean, 64 and 72 mL, respectively. They go on to suggest that, when comparing populations of different BMI and BSA, absolute SV is preferable to reporting SV indexed to BSA (SV/m=SI). Thus, the authors intimate that normalization of SV (or CO) between varying patient populations is unwarranted. It is this authors’ opinion that, normalization of SV/CO by BSA provides the only practical method to assess and compare the adequacy of tissue perfusion within and between patient populations of diverse anthropometric dimensions; I did not invent this rather obvious convention. With reference to their alleged agreement with the SV results of Dumont et al., Bland–Altman method yields a difference between absolute SV values of only 12%. However, normalization by their respective BSAs (2.64 m for Balderi et al. [6] vs 2.41 m for Dumont et al.) produces a SI difference of 21%, which represents an unacceptable negative bias. It can therefore be stated that SI obtained by the PRAM method substantially underestimated the SI estimate found by TDCO. Thus, the authors ought to have stated that, for a beat-to-beat method measuring SV, comparing measurements of absolute SV and CO between different methods and patient populations is misleading. The authors must have known this to be correct because Balderi et al. [6], the subject of the commentary and reply, reported their results as SI and CI (Table 2 and Fig. 1). With respect to systemic vascular resistance index (SVRI), Forfori et al. are quite correct in showing that Artuso et al. incorrectly labeled the dimensions of what they report as SVR (dyne·s·cm). Using data provided by Artuso et al., the values given are actually those of SVRI (dyne·s·cm·m). For the SVRI reported on induction of anesthesia, the following computation pertains: {[(MAP-CVP)×80]/CO}×BSA={[(82.97–15.15)× 80]/9.23}×2.6=1,528 dyne·s·cm·m, which is less than half that reported by Balderi et al. Considering the statement that the SVR values reported by Balderi et al. are “only slightly different from Dumont et al.”, simple computation shows that, on the mean, the SVR of Balderi et al. is 40% higher. OBES SURG (2009) 19:131–133 DOI 10.1007/s11695-008-9743-0

Preconditions of Hemostasis in Trauma: A Review. The Influence of Acidosis, Hypocalcemia, Anemia, and Hypothermia on Functional Hemostasis in Trauma

Beside the often discussed topics of consumption and dilution coagulopathy, additional perioperative impairments of coagulation are caused by acidosis, hypocalcemia, anemia, hypothermia, and combinations. Reviewing current literature, cutoff values of these parameters become obvious at which therapy should commence. A notable impairment of hemostasis arises at a pH < or = 7.1. Similar effects are caused by a BE of -12.5 or less. Thus, in case of severe bleeding, buffering toward physiologic pH values is recommended, especially with massive transfusions of older RBCCs displaying exhausted red blood cell buffer systems. It completes the optimization of the volume homeostasis to ensure an adequate tissue perfusion. Combining beneficial cardiovascular and coagulation effects, the level for ionized calcium concentration should be held > or = 0.9 mmol/L. From the hemostatic point of view, the optimal Hct is higher than the one required for oxygenation. Even without a "classical" transfusion trigger, the therapy of acute, persistent bleeding should aim at reaching an Hct > or = 30%. A core temperature of < or = 34 degrees C causes a decisive impairment of hemostasis. A controlled hypotensive fluid resuscitation should aim at reaching a mean arterial pressure of > or = 65 mm Hg (possibly higher for cerebral trauma). Prevention and later aggressive therapy of hypothermia by exclusive infusion of warmed fluids and the use of warming devices are prerequisites for the cure of traumatic coagulopathy. Combined appearance of single preconditions cause additive impairments of the coagulation system. The prevention and timely correction, especially of the combination acidosis plus hypothermia, is crucial for the treatment of hemorrhagic coagulopathy.

Clinical validation of the non-invasive cardiac output monitor USCOM-1A in critically ill patients

Cardiac output is frequently monitored to maintain and improve cardiac function with the primary goal of adequate tissue perfusion. The pulmonary artery catheter is considered to be the gold standard although several non-invasive devices are being introduced and gaining attention. To evaluate the accuracy of the ultrasonic cardiac output monitor (USCOM)-1A (Pty Ltd, Coffs Harbour, NSW, Australia), a non-invasive cardiac output device including its capability to differentiate between different shock states in haemodynamically unstable ICU patients was used in this single-centre, prospective, observational study. Cardiac output was measured with a pulmonary artery catheter and transcutaneously via a suprasternal approach with the USCOM-1A by continuous-wave Doppler ultrasound in 25 adult patients in a mixed medical and surgical ICU in a major teaching hospital in the Netherlands. A total of 1315 USCOM-1A cardiac output measurements were performed. In order to reduce time-variability, the mean of five consecutive USCOM-1A measurements was calculated. Total 263 values were compared with 263 thermodilution cardiac output measurements performed with a pulmonary artery catheter. Data were analysed for systematic error, precision and correlation. Systematic and random errors were found. On average USCOM-1A values were 12% lower than thermodilution measurements (systematic error), while the random error was 17% (coefficient of variation). The error comprised an inter-operator variability of 3%, an inter-patient variability of 11% and residual variability of 15%. The correlation coefficient of the calculated cardiac index with the USCOM-1A and the pulmonary artery catheter was r = 0.8024 and 0.6438, respectively. Temperature and gender did not influence correlations. The learning curve for USCOM-1A skill acquisition was steep. The correlation between the two techniques was acceptable, although relevant systematic and variable errors were detected. USCOM-1A provided adequate data to distinguish non-invasively different shock types in ICU patients.

Using Transcutaneous Oxygen Pressure Measurements as Selection Criteria for Activated Protein C Use

Limited resources and the expense of Activated Protein C (APC) (drotrecogin alfa) may contribute to the reluctance to utilize this drug in sepsis. Employing the PROWESS criteria resulted in absolute reduction in 28-day mortality of 6.1%, representing a relative risk reduction of 19.4%. Additional patient categorization and selection may lead to less frequent drug use with the same survival advantage. We used transcutaneous partial pressure of oxygen (PtcO2) as an indicator of microcirculatory perfusion to identify which septic patients may benefit from APC. Nineteen patients consecutively admitted with severe sepsis or septic shock that fulfilled the PROWESS criteria for APC treatment. APC was administered to patients with the PROWESS selection criteria, only if the PtcO2 information demonstrated tissue ischemia. Nineteen patients met the PROWESS criteria. Ten patients demonstrated poor tissue perfusion using PtcO2 monitors and received APC. Nine patients had adequate tissue perfusion and did not receive APC. There were no differences in age, gender, APACHE II scores, lactate levels, or organ failure between the two groups. The 10 patients who received APC had a mortality of 3 of 10 (30%). The survivors of this group uniformly converted to PtcO2 values consistent with survival within 12 hours to 24 hours of drug administration. The nine patients who did not receive APC had a mortality of 2 of 9 (22%), not statistically significant from those who received the drug (p = 0.89). Withholding APC did not result in an increase in mortality from severe sepsis in those patients who demonstrated adequate PtcO2 values. The transcutaneous oxygen measurement may be a useful adjuvant in addition to the other selection criteria for better identification of patients who may benefit from APC.

Hypoxemia after an axial flow pump Jarvik-2000 implantation: Catheter induced

Hypoxemia after an axial flow pump Jarvik-2000 implantation: Catheter induced

Targeting the prevention of plaque rupture as a new strategy for prevention of acute arterial cardiovascular events

Acute arterial cardiovascular disease is usually caused by the sudden thrombotic occlusion of a vessel that is critical for maintaining adequate tissue perfusion and that contains an atherosclerotic plaque. Due to a myriad of processes within this plaque, rupture of its fibrous cap may occur, thereby exposing highly procoagulant material to the circulating blood, leading to occlusive thrombus formation and subsequent ischemia or infarction. In particular, inflammatory cells bearing tissue factor at their surface play a pivotal role in this mechanism, as tissue factor has been found to be the principal activator of the coagulation cascade, leading to the generation of thrombin and subsequent conversion of fibrinogen to fibrin. Hence, pharmacological strategies aimed at the prevention and treatment of acute cardiovascular disease thus far mainly focus on the reduction of atherosclerotic burden (e.g. by preventative strategies towards risk factors for atherosclerosis or by administration of statins) or on the inhibition of coagulation activation (e.g. by anticoagulants or anti-platelet agents). Besides these strategies, which have indeed been proven to be effective, stabilization of the atherosclerotic plaque could theoretically prevent plaque rupture and its … *Corresponding author. Tel: +31 20 5662171; fax: +31 20 6919658. E-mail address : m.m.levi{at}amc.uva.nl

Dexmedetomidine continuous rate infusion during isoflurane anaesthesia in canine surgical patients

ObjectiveTo determine the effects of three rates of dexmedetomidine (DMED) constant rate infusion (CRI) on overall tissue perfusion, isoflurane (ISO) requirements, haemodynamics and quality of recovery in canine surgical patients. Study designProspective, randomized, blinded clinical study. AnimalsClient-owned dogs presented for soft tissue or orthopaedic surgery. MethodsFollowing intravenous (IV) pre-medication with DMED (5 μg kg−1) and buprenorphine (10 μg kg−1) and propofol induction, anaesthesia was maintained with ISO in oxygen/air supplemented with a DMED CRI (1, 2 or 3 μg kg−1 hour−1; groups 1, 2 and 3, respectively). Ventilation was controlled in all animals using intermittent positive pressure ventilation (IPPV). Monitoring included end-tidal (ET) gases, ECG, arterial blood pressure, body temperature and sequential arterial blood gas and lactate measurements. Quality of recovery was scored after intramuscular (IM) administration of atipamezole (ATI) (12.5 μg kg−1). Immediate post-operative analgesia was provided with carprofen and/or buprenorphine. An analysis of variance was conducted for repeated measurements obtained during 80 minutes after first incision. Categorical data were evaluated with Chi-square analyses. ResultsArterial blood pressure remained stable and within clinically acceptable limits. Mean heart rate in group 2 was significantly lower than in group 1. The incidence of 2nd degree AV block type II was significantly higher in group 3. Mean arterial lactate concentrations remained below 2 mmol/L in all groups during the study, with a significant increase occurring during recovery compared with surgery for group 3. Mean e′ISO% was similar and <1% in all groups. Complete recovery from anaesthesia was achieved after ATI administration and was of good quality in all but three animals. Conclusions and clinical relevanceDexmedetomidine CRI is a reliable and valuable adjunct to ISO anaesthesia in maintaining surgical anaesthesia in ASA I-II dogs. Data reported indicate adequate overall tissue perfusion and a low ISO requirement while enabling a smooth and rapid recovery following ATI. The DMED CRI of 1 μg kg−1 hour−1 following a loading dose of 5 μg kg−1 produced the most favourable results.

Stunning, Hibernation, and Assessment of Myocardial Viability

The last 3 decades have witnessed an unprecedented improvement in the outcome of patients with acute coronary syndromes. The widespread use of thrombolytic therapy and percutaneous coronary interventions, in association with increasingly potent antithrombotic agents, has contributed to significant reductions in mortality and morbidity in these patients. Although overall survival has improved, a downside of this success has been the greater number of patients with residual left ventricular (LV) dysfunction undergoing progressive LV remodeling and congestive heart failure. This problem is compounded by the rising age of our population and the higher prevalence of comorbidities such as diabetes mellitus that confer an increased risk of coronary artery disease (CAD) and congestive heart failure. Patients with CAD represent by far the most numerous cohort among those with congestive heart failure, and their treatment remains a partial success.1 Typically, these patients have multivessel disease, increased LV volumes, and variable degrees of regional and/or global systolic dysfunction, although more cases of isolated diastolic dysfunction have been reported recently.2–4 In these patients, coronary revascularization may lead to symptomatic and prognostic improvement, and these clinical benefits are accompanied by evidence of reverse LV remodeling. In this context, the concept of myocardial viability was developed and a number of different techniques have been used to demonstrate the presence of viable tissue before coronary revascularization. The aim of this review article is to summarize our current understanding of the concept of myocardial viability and its clinical implications in patients with CAD and chronic LV dysfunction. Throughout this review, we use the term viability to describe dysfunctional myocardium subtended by diseased coronary arteries with limited or absent scarring that therefore has the potential for functional recovery. Viability is a prospective definition, but it does not imply evidence of functional recovery after interventions. The term hibernation, which …

The Chinese Society of Anesthesiology: 2006 Annual Meeting

The Chinese Society of Anesthesiology (CSA) 2006 Annual Meeting was held on September 9–11, 2006, at the Zhenzhou International Exhibition Center, Henan Province, China. The annual meeting was cosponsored by the Henan branch of the CSA and was attended by more than 2600 anesthesiologists representing six countries. Invited guests included internationally renowned speakers from the United States (USA), Canada, the United Kingdom (UK), Singapore, Japan, and China. There were 2261 abstracts and 287 invited oral presentations, including refresher courses, panels, and clinical case discussions. A variety of anesthesia fields were covered, including clinical anesthesia, pain medicine, critical care medicine, and anesthesia education. Professor Shuren Li, from Beijing Friendship Hospital, president of the CSA opened the meeting. This first session was moderated by Professor Ailun Luo, from Peking Union Medical College Hospital, and Junke Wang, from the First Hospital, China Medical University, Shenyang. President Shuren Li provided a summary of the annual activities of the CSA. Internationally, the CSA became an official member of the World Federation of Societies of Anesthesia. The CSA has completed a survey of the demographics of Chinese anesthesiologists. The CSA has tried to provide more training and educational opportunities across the country, and is also set to strengthen the training of anesthesiologists in the western areas of China. Thereafter, Professor Steven Shafer from Stanford University, USA, provided an update on propofol and target-controlled infusion (TCI) highlighting relevant pharmacokinetic concepts and new developments in the field. Professor Adrian W. Gelb, University California San Francisco, USA, presented a lecture on “Perioperative Stroke in General Surgical Patients.” Professor Gelb discussed the risk factors and management of perioperative stroke and outlined the role that China could play in helping to better understand this problem. Professor Mervyn Maze, Imperial College, UK, reported on “Mechanism and Perioperative Application of
2 Agonists” highlighting both laboratory and clinical studies. Professor Ronald D. Miller, University California San Francisco, USA, gave a report on “The Future of Anesthesia (the Next 20 Years) and the Role of Technology.” Professor Miller described new drugs and the wonderful opportunities in the future for anesthesiologists to be involved in perioperative care and illustrated the important role of new technology. All of the invited lectures presented in English were simultaneously translated into Mandarin and the PowerPoints were in both languages to facilitate communication. The meeting was held in five meeting halls beginning the afternoon of September 9 and all sessions ran in parallel. Dr. Xiangyang Guo, from Peking Union Medical College Hospital, and Dr. Liyun Zhao, from Beijing Anzhen Hospital, discussed issues of “Anesthesia for Patients with Diabetes Mellitus or Pulmonary Artery Hypertension.” Dr. Guo reviewed the literature showing that the control of perioperative blood glucose level was very important in determining outcome. His lecture advised Chinese anesthesiologists to pay more attention to the management of blood glucose of surgical patients with diabetes mellitus. Dr. Zhao provided an update on “Research About Pulmonary From the *Department of Anesthesiology, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China; †Department of Anesthesiology, The Third Affiliated Hospital, Zhengzhou University, Zhengzhou, China; ‡Department of Anesthesiology, Peking Union Medical College Hospital, Beijing, China; and §Department of Anesthesiology, University California San Francisco, School of Medicine, San Fransisco, California. Accepted for publication July 3, 2007. Address correspondence and reprint requests to Dr. Yun Yue, Department of Anesthesiology, Beijing Chaoyang Hospital, Capital Medical University, 100020, Beijing, China. Address e-mail to yueyun@hotmail.com. Copyright © 2007 International Anesthesia Research Society DOI: 10.1213/01.ane.0000281077.53805.50

Die Physiologie der Wundheilung

Wound healing is a complex biological phenomenon. A variety of cellular and biochemical events take place designed to achieve tissue integrity following injury. Even though hypoxia caused by the damaged microvasculature is an important initial stimulus of the healing cascade, adequate tissue perfusion and oxygenation is an absolute pre-requisite for a successful repair since essential wound healing mechanisms such as collagen deposition and bactericidal defence are oxygen dependent reactions. Based upon these findings, there are several ways to overcome the obstacle of tissue hypoxia in clinical practice. Supplemental oxygen is capable of increasing tissue oxygen tension. Following surgery, pain, cold and to little fluids are the main issues of vasoconstriction, impaired tissue perfusion and oxygenation as well. However, all these parameters must be corrected at the same time because any one is sufficient to cause maximal vasoconstriction. A well hydrated, pain free and warm patient should be the main goal of peri- and postoperative surgical care.

Permissive range of hypercapnia for improved peripheral microcirculation and cardiac output in rabbits*

Permissive hypercapnia improves outcomes in patients with respiratory failure, most likely because of a reduction in ventilator-induced lung injury. Because hypercapnia is a potent vasoactive stimulus, adequate tissue perfusion and oxygen delivery to dilated microvessels may be restored. We examined how Paco2 affects microvascular changes, hemodynamics, and cardiac output in rabbits. We evaluated the permissive range of Paco2 required for maintenance of the peripheral circulation. Prospective experimental animal study. Animal research laboratory. A total of 31 Japanese domestic white rabbits. The animals were anesthetized with pentobarbital. An ear chamber was prepared to examine blood vessels by intravital microscopy. The rabbits were mechanically ventilated with air, oxygen, and CO2. The values of Paco2 were adjusted to about 20 (hypocapnia), 40 (normocapnia), 60, 80, 100, 125, 150, and >250 mm Hg (hypercapnia). After stabilization at each Paco2 level, microvascular changes were recorded with a microscope-closed video camera to permit analysis of arteriolar diameter and blood flow. The pH and heart rate decreased and mean blood pressure increased progressively as the Paco2 was increased. When Paco2 was increased from 20 to 80 mm Hg, vessel diameter, blood-flow velocity, and blood-flow rate increased markedly. Cardiac output increased slightly. When Paco2 exceeded 100 mm Hg, all of these variables decreased. When Paco2 exceeded 150 mm Hg, all variables were significantly lower than the control values (p < .01). Intravital microscopic visualization of the rabbit ear microcirculation showed that 150 mm Hg is the permissive upper limit of acute hypercapnia with respect to maintenance of the peripheral microcirculation.

A PROSPECTIVE RANDOMIZED TRIAL COMPARING OXYGEN DELIVERY VERSUS TRANSCUTANEOUS PRESSURE OF OXYGEN VALUES AS RESUSCITATIVE GOALS

Transcutaneous pressure of oxygen (PtcO2) correlates with arterial pressure of oxygen (PaO2) in nonshock states, but in shock states, PtcO2 approximates cardiac output with no response to increasing fraction of inspired oxygen (FiO2) and PaO2. An incremental change of more than 21 mmHg in PtcO2 in response to an FiO2 of 1.0 (identified as the oxygen challenge test [OCT]) implies adequate tissue perfusion, and lack of response has been associated with mortality. Patients with severe sepsis and septic shock requiring pulmonary artery catheters were randomized to two groups: the oxygen delivery (DO2) group was treated to a DO2 and mixed venous oxygen saturation goals, and the PtcO2 group was treated to achieve an OCT value of 40 mmHg or more. The DO2 (n = 30) and PtcO2 (n = 39) groups were similar in baseline characteristics. Mortality rate was 12 (40%) of 39 for the DO2 group and 5 (13%) of 39 for the PtcO2 group (P = 0.02). Logistic regression analysis of the statistically significant variables between survivors and nonsurvivors demonstrated that inability to reach the PtcO2 goal at 24 h after resuscitation (T24) and a positive cardiac history are associated with mortality (P < 0.001). The area under the receiver operating curve was 0.824 for the OCT at T24. The best OCT value was 25 mmHg at T24 with positive and negative predictive values of 87% and 90%, respectively. Treating patients with severe sepsis/septic shock to an OCT value of 25 mmHg or more may provide a specific end point of resuscitation that may be associated with better survival than resuscitating to the central hemodynamic parameters of DO2 and mixed venous oxygen saturation.

VASOPRESSIN MEDIATES THE PRESSOR EFFECT OF HYPERTONIC SALINE SOLUTION IN ENDOTOXIC SHOCK

The administration of lipopolysaccharide (LPS) to experimental animals results in a septic shock-like syndrome characterized by hypotension, and the hemodynamic management includes the restoration of adequate tissue perfusion by administration of resuscitation fluids to achieve an effective circulating volume. In the present study, we sought to investigate the effects of hypertonic saline solution administration on vasopressin secretion and mean arterial pressure in endotoxic shock. The pressor response to isotonic saline solution (0.9% sodium chloride) or hypertonic saline (7.5% sodium chloride, 4 mL/kg i.v.) was evaluated 4 h after LPS (1.5 mg/kg) administration. At this moment, plasma vasopressin did not differ from control; however, the blood pressure was lower in the LPS-treated group. The hypertonic saline administration was followed by an immediate recovery of blood pressure and also by an increase in plasma vasopressin levels compared with isotonic saline solution. The vasopressin V1 receptor antagonist (10 microg/kg, i.v., 5 min before infusion) blocked the pressor response to hypertonic saline solution. These data suggest that the recovery of blood pressure after hypertonic saline solution administration during endotoxic shock is mediated by vasopressin secretion.

Coagulopaty in associated with massive transfusion

Massive hemorrhage is a formidable challenge for anesthesia care providers in the elective setting and poses even greater potential challenges in the trauma setting. In all this cases, the anesthesia care providers are faced with large-volume resuscitations that typically start with crystalloid and colloid and rapidly progress to blood and blood products. These large-volume replacement may cause coagulopathy, which can be difficult to manage in the setting of ongoing blood loss. Coagulopathy associated with massive transfusion is multifactorial event that results from hemodilution, hypothermia, the use of fractionated blood products and disseminated intravascular coagulation. Maintaining a normal body temperature is a first-line, effective strategy to improve hemostasis during massive transfusion. Treatment strategies include the maintenance of adequate tissue perfusion, the corection of anemia, and the use of hemostatic blood products.

Nitric oxide and nursing: a review

This paper, therefore, aimed to review published literature in this area of pharmacological exploitation, to look at the therapeutic applications and clinical relevance and, by so doing, provide an accessible source for nurses to gain insight into the role of nitric oxide in the clinical setting. Nitric oxide is a chemical mediator fundamental in the maintenance of adequate tissue perfusion and effective cardiovascular function; a major endogenous regulator of vascular tone. The use of nitrates are well established as pharmacological agents but it is only recently that it has been recognized that they act as a source of nitric oxide. Although widely addressed within the medical literature, there appears to be a paucity of nursing literature that explores either its physiological action, or its relevance to nursing practice. This literature review provides an overview of the use of nitric oxide and its implications for nursing practice and patient outcomes. Knowledge of nitric oxide and its action is pertinent to nurses across diverse specialities. It helps in understanding the principles of many nitrogen-derived medications which nurses administer to their patients on a daily basis. In terms of oral medication, this is demonstrated by greater insights into the action of nitrates, the appreciation of surprising developments in medications such as sildenafil and the development of new drug opportunities such as nitric oxide-non-steroidal anti-inflammatory drugs. Equally, the use of inhaled nitric oxide therapy in adult and neonatal critical care units appears to be an increasingly valuable source of treatment. A particular research challenge is found in the attempt at nitric oxide inhibition in the management of septic shock. The authors argue that understanding such esoteric areas of therapeutic developments is increasingly to be part of the repertoire of knowledge and skills for nurses in the 21st century.

Imaging microvascular obstruction and its clinical significance following acute myocardial infarction

Obstruction of the coronary microvasculature contributes to the pathophysiology of MI and adversely affects post-MI recovery. This "no-reflow" phenomenon resulting from microvascular obstruction is an indicator of lack of adequate tissue perfusion within the infarcted myocardium, even after restoration of epicardial blood flow. Regions of microvascular obstruction can be detected and quantifed because of rapid advances in and refinement of imaging technologies over the past decade. This article focuses on the non-invasive imaging modalities used to assess MO, discusses the prognostic implications of MO, and briefly addresses strategies for reducing MO.