Morbidity In High-risk Surgical Patients Research Articles

Predicting and Preventing Postoperative Mortality and Morbidity in High-Risk Surgical Patients

Predicting and Preventing Postoperative Mortality and Morbidity in High-Risk Surgical Patients

Arterial pulse pressure and postoperative morbidity in high-risk surgical patients

BackgroundSystemic arterial pulse pressure (systolic minus diastolic pressure) ≤53 mm Hg in patients with cardiac failure is correlated with reduced stroke volume and is independently associated with accelerated morbidity and mortality. Given that deconditioned surgical and heart failure patients share similar cardiopulmonary physiology, we examined whether lower pulse pressure is associated with excess morbidity after major surgery. MethodsThis was a prospective observational cohort study of patients deemed by their preoperative assessors to be at higher risk of postoperative morbidity. Preoperative pulse pressure was calculated before cardiopulmonary exercise testing. The primary outcome was any morbidity (PostOperative Morbidity Survey) occurring within 5 days of surgery, stratified by pulse pressure threshold ≤53 mm Hg. The relationship between pulse pressure, postoperative morbidity, and oxygen pulse (a robust surrogate for left ventricular stroke volume) was examined using logistic regression analysis (accounting for age, sex, BMI, cardiometabolic co-morbidity, and operation type). ResultsThe primary outcome occurred in 578/660 (87.6%) patients, but postoperative morbidity was more common in 243/ 660 patients with preoperative pulse pressure ≤53 mm Hg{odds ratio (OR): 2.24 [95% confidence interval (CI): 1.29–3.38]; P<0.001). Pulse pressure ≤53 mm Hg [OR:1.23 (95% CI: 1.03–1.46); P=0.02] and type of surgery were independently associated with all-cause postoperative morbidity (multivariate analysis). Oxygen pulse <90% of population-predicted normal values was associated with pulse pressure ≤ 53 mm Hg [OR: 1.93 (95% CI: 1.32–2.84); P=0.007]. ConclusionsIn deconditioned surgical patients, lower preoperative systemic arterial pulse pressure is associated with excess morbidity. These data are strikingly similar to meta-analyses identifying low pulse pressure as an independent risk factor for adverse outcomes in cardiac failure. Low preoperative pulse pressure is a readily available measure, indicating that detailed physiological assessment may be warranted. Clinical trial registrationISRCT registry, ISRCTN88456378.

Haemodynamic monitoring using arterial waveform analysis

To describe the theory behind arterial waveform analysis, the different variables that may be obtained using this method, reliability of measurements and their clinical relevance. Areas for future research are identified. The precision of cardiac output (CO) measurements varies considerably and deteriorates during haemodynamic instability. Significant device-to-device differences exist. Nevertheless, most are sufficiently accurate for tracking changes in CO. Targeted intervention guided by haemodynamic monitoring reduces mortality and morbidity in high-risk surgical patients. Dynamic changes in variables such as systolic pulse variation, pulse pressure variation (PPV) and stroke volume variation (SVV) may be useful for evaluating fluid responsiveness, although important caveats exist. Newer indices such as PPV : SVV ratio may be useful in identifying preload and vasopressor-dependent patients. Peripheral arterial dP/dt has not been validated in critically ill patients and requires further investigation. Despite significant limitations in measurement accuracy and inter-device differences, arterial waveform analysis is a potentially useful tool for monitoring the central circulation in critically ill patients. Future studies investigating the effects of haemodynamic management guided by arterial waveform variables in critically ill patients are urgently needed. The evaluation of cardiopulmonary interactions and usefulness of dP/dt are other areas that require further investigation.

Dopexamine and microcirculatory flow in transplanted small bowel: The Leeds experience

Intestinal mucosa is extremely vulnerable to ischemic injury. In transplanted small bowel, this may represent preservation, ischemia-reperfusion injury, technical errors, postimplantation ischemia, or rejection. Such injury may compromise the mucosal barrier. Barrier dysfunction can lead to bacterial translocation and endotoxemia, a trigger for multisystem organ failure (MSOF). Prevention of further ischemic injury in the postoperative period by maintaining optimal graft perfusion may have a major role to play in ensuring graft viability. Previous methods of monitoring graft function have included clinical assessment, serum procoagulant levels, serial endoscopy and mucosal biopsy, and intestinal permeability studies. These methods are not ideal for monitoring early graft function. A number of noninvasive measures of graft perfusion are now available. These include laser Doppler flowmetry (LDF) and gut tonometry. Neither of these techniques has been applied to the transplanted small bowel. LDF is easy to use, is noninvasive, allows continuous monitoring, and its use has been validated in orthotopic liver transplantation (OLT) and in postoperative monitoring of new grafts. Gut tonometry was designed to allow measurement of bowel intramucosal pH (pHi). Low intestinal pH indicates splanchnic hypoperfusion or anaerobic metabolism, is common in critical illness, and is associated with increased morbidity and mortality after major surgery and trauma. Gastric tonometry has been used to monitor early graft function in OLT. Both techniques enable evaluation both of graft function and of therapies aimed at improving perfusion. The pharmacologic profile of dopexamine suggests it would prove a valuable agent in improving splanchnic blood flow. It is a dopamine (DA) analog with action at β 2 adrenoceptors and DA 1 receptors and only moderate activity at β 1 and DA 2 receptors. Dopexamine possesses no direct α-adrenoceptor activity, but norepinephrine reuptake is inhibited. Dopexamine improves cardiac performance by vasodilatation and mild isotropic activity. These hemodynamic effects are achieved without increased myocardial oxygen consumption. Dopexamine has been shown to improve splanchnic oxygenation, an effect which appears to be independent of its systemic effects. Boyd et al have shown that deliberately increasing oxygen delivery perioperatively significantly reduces mortality and morbidity in high-risk surgical patients. We have therefore studied the effects of dopexamine on gut mucosal blood flow following small bowel transplantation, using LDF and gastric tonometry.

Increasing oxygen delivery in surgical patients

<h3>To the Editor.</h3> —Dr Boyd and colleagues¹conclude from their study that "[p]erioperative increase of oxygen delivery with dopexamine hydrochloride significantly reduces mortality and morbidity in high-risk surgical patients." I do not understand why they elect to report their results in terms of an increase in oxygen delivery (Do₂I), and I do not believe that their results support this interpretaton. They set out to control the arterial oxygen saturation and hemoglobin in the two groups of patients, and the results indicate that they accomplished this goal; there were no statistically significant differences between the groups in these measured variables. Cardiac index was significantly different between the two groups, as a direct effect of the intervention. Since the formula for calculating Do₂I uses arterial oxygen saturation, hemoglobin, and cardiac index, the difference in Do₂I between the two groups depends only on the difference in

Increasing Oxygen Delivery in Surgical Patients

<h3>To the Editor.</h3> —Dr Boyd and colleagues¹conclude from their study that "[p]erioperative increase of oxygen delivery with dopexamine hydrochloride significantly reduces mortality and morbidity in high-risk surgical patients." I do not understand why they elect to report their results in terms of an increase in oxygen delivery (Do₂I), and I do not believe that their results support this interpretaton. They set out to control the arterial oxygen saturation and hemoglobin in the two groups of patients, and the results indicate that they accomplished this goal; there were no statistically significant differences between the groups in these measured variables. Cardiac index was significantly different between the two groups, as a direct effect of the intervention. Since the formula for calculating Do₂I uses arterial oxygen saturation, hemoglobin, and cardiac index, the difference in Do₂I between the two groups depends only on the difference in

A Randomized Clinical Trial of the Effect of Deliberate Perioperative Increase of Oxygen Delivery on Mortality in High-Risk Surgical Patients

To assess the effect of deliberate perioperative increase in oxygen delivery on mortality and morbidity in patients who are at high risk of both following surgery. Prospective, randomized clinical trial. A teaching hospital general intensive care unit, London, England. A total of 107 surgical patients, who were assessed as high risk from previously identified criteria, were studied during an 18-month period. Patients were randomly assigned to a control group (n = 54) that received best standard perioperative care, or to a protocol group (n = 53) that, in addition, had deliberate increase of oxygen delivery index to greater than 600 mL/min per square meter by use of dopexamine hydrochloride infusion. Mortality and complications were assessed to 28 days postoperatively. Groups were similar with respect to demographics, admission criteria, operation type, and admission hemodynamic variables. Groups were treated similarly to maintain blood pressure, arterial saturation, hemoglobin concentration, and pulmonary artery occlusion pressure; however, once additional treatment with dopexamine hydrochloride had been given, the protocol group had significantly higher oxygen delivery preoperatively (median, 597 vs 399 mL/min per square meter; P < .001) and postoperatively (P < .001). Results indicate a 75% reduction in mortality (5.7% vs 22.2%; P = .015) and a halving of the mean (+/- SEM) number of complications per patient (0.68 [+/- 0.16] vs 1.35 [+/- 0.20]; P = .008) in patients randomized to the protocol group. Perioperative increase of oxygen delivery with dopexamine hydrochloride significantly reduces mortality and morbidity in high-risk surgical patients.

Enteral feeding in the critically injured patient.

Metabolic support is an integral component in the care of the critically injured patient. When hypermetabolism occurs, there are increases in energy demands along with changes in substrate utilization. This article reviews the prospective randomized clinical trials that were undertaken at Denver General Hospital over the past decade that address both the timing of nutritional support and the route of administration in this critically injured population. Also discussed is a review of a meta-analysis that attests to the feasibility of early postoperative enteral feeding with the possibility of decreased septic morbidity in high-risk surgical patients. With the clinical knowledge gained from these trials, an algorithm for nutritional intervention was developed that represents our current standard of practice.

Analgesia for Post-Cesarean Delivery Pain

Summary A recent survey by Gibbs et al27 indicates that of the cesarean sections performed in this country 41 per cent are conducted using general anesthesia, 34 per cent are conducted using spinal anesthesia, and 21 per cent are conducted using epidural anesthesia. This survey identifies three separate populations of patients and three different routes by which we may tailor the patient’s postoperative analgesia. These routes that involve epidural, intrathecal, and patient-controlled IV analgesic administration are gaining in popularity and are replacing traditional IM analgesics. It has become clear over the past few years that intraspinal narcotics and PCAs can provide the post-cesarean patient with superior analgesia compared with IM narcotics.24, 32 It has also become clear that these techniques can be delivered safely with very little risk to the patient, perhaps no greater than conventional analgesic techniques. The benefits of these new techniques is not limited to better analgesia. Patients given epidural morphine following cesarean section become ambulatory earlier than those given IV morphine for relief of pain.17 Epidural opiate analgesia has been shown to reduce morbidity in high-risk surgical patients and thereby improve outcome.48, 69 There is also evidence that even the low-risk cesarean section patients given intraspinal morphine for postoperative pain relief may have a shorter hospital stay than those given IV and IM narcotics.56 Finally, recent studies by Harrison et al32 and Eisenach et al24 have compared IM, PCA, and epidural narcotics for providing post-cesarean analgesia. They demonstrated that, in terms of providing analgesia, PCA was superior to IM narcotics, and that epidural narcotics were superior to PCA. A surprising finding, and one that deserves further study, was that even though those patients given epidural narcotics reported better analgesia than those given IM or PCA, those patients given PCA reported higher levels of satisfaction compared with prior cesarean deliveries than those patients given epidural narcotics.24 Again, it is not a direct comparison but an implied or inferred comparison. Thus, in those instances when epidural or intrathecal narcotic administration is impossible or undesirable, PCA can provide an attractive alternative, offering excellent analgesia and a high degree of patient satisfaction. In this article we reviewed the analgesic options available for the post-cesarean patient and attempted to outline the risks, benefits, and implementation of three new techniques for providing analgesia. With each new year these techniques have been finding, and will undoubtedly continue to find, wider clinical application, thereby improving the care for women having cesarean deliveries.