Noninvasive respiratory support in the perioperative period.

PURPOSE OF REVIEW: Pulmonary complications ranging from atelectasis to acute respiratory failure are common causes of poor perioperative outcomes. As the surgical population becomes increasingly at risk for pulmonary dysfunction due to increasing age and weight, development of an approach toward respiratory compromise in these patients is becoming ever more important. Given the utility of noninvasive respiratory support (NRS) in acute respiratory failure, it is likewise likely to also be important in the perioperative period. RECENT FINDINGS: NRS is evaluated from preoperative risk assessment to its use in prevention and treatment of acute respiratory failure. Data supporting intraoperative use of NRS including preinduction continuous positive airway pressure and postextubation NRS for high-risk individuals and surgeries are examined. Timing and duration of NRS is also addressed. Finally, NRS is proposed for treatment for postoperative acute respiratory failure as an alternative to invasive rescue maneuvers. SUMMARY: Noninvasive respiratory support should be considered an important adjunct in perioperative pulmonary care. Usage should be individually tailored in regard to timing and application modality specific to patient and surgical circumstances. More studies are needed, however, to determine the relationship demonstrated between short-term improvements in lung function and long-term outcomes.

Trauma and aggressive homeostasis management.

Homeostasis refers to the capacity of the human body to maintain a stable constant state by means of continuous dynamic equilibrium adjustments controlled by a medley of interconnected regulatory mechanisms. Patients who sustain tissue injury, such as trauma or surgery, undergo a well-understood reproducible metabolic and neuroendocrine stress response. This review discusses 3 issues that concern homeostasis in the acute care of trauma patients directly related to the stress response: hyperglycemia, lactic acidosis, and hypothermia. There is significant reason to question the "conventional wisdom" relating to current approaches to restoring homeostasis in critically ill and trauma patients.

Postoperative noninvasive ventilation.

General anesthesia and surgery are associated with changes in the shape of the chest that result in atelectasis, a major factor in the development of postoperative respiratory failure. Postoperative noninvasive positive pressure ventilation (NIPPV) has been shown to improve oxygenation and ventilation for high-risk patients. NIPPV has been used as rescue therapy for patients developing acute respiratory distress postoperatively, and appears to be most frequently successful in patients whose problem is atelectasis or obesity. Failure to respond to NIPPV after 20 minutes is usually an indication of intubation, mechanical ventilation, and transfer to the intensive care unit.

Clinical review: Special populations--critical illness and pregnancy.

Critical illness is an uncommon but potentially devastating complication of pregnancy. The majority of pregnancy-related critical care admissions occur postpartum. Antenatally, the pregnant patient is more likely to be admitted with diseases non-specific to pregnancy, such as pneumonia. Pregnancy-specific diseases resulting in ICU admission include obstetric hemorrhage, pre-eclampsia/eclampsia, HELLP (hemolysis, elevated liver enzymes, and low platelet count) syndrome, amniotic fluid embolus syndrome, acute fatty liver of pregnancy, and peripartum cardiomyopathy. Alternatively, critical illness may result from pregnancy-induced worsening of pre-existing diseases (for example, valvular heart disease, myasthenia gravis, and kidney disease). Pregnancy can also predispose women to diseases seen in the non-pregnant population, such as acute respiratory distress syndrome (for example, pneumonia and aspiration), sepsis (for example, chorioamnionitis and pyelonephritis) or pulmonary embolism. The pregnant patient may also develop conditions co-incidental to pregnancy such as trauma or appendicitis. Hemorrhage, particularly postpartum, and hypertensive disorders of pregnancy remain the most frequent indications for ICU admission. This review focuses on pregnancy-specific causes of critical illness. Management of the critically ill mother poses special challenges. The physiologic changes in pregnancy and the presence of a second, dependent, patient may necessitate adjustments to therapeutic and supportive strategies. The fetus is generally robust despite maternal illness, and therapeutically what is good for the mother is generally good for the fetus. For pregnancy-induced critical illnesses, delivery of the fetus helps resolve the disease process. Prognosis following pregnancy-related critical illness is generally better than for age-matched non-pregnant critically ill patients.

Metabolic syndrome: anesthesia for morbid obesity.

PURPOSE OF REVIEW: There is an emerging epidemic of obesity worldwide resulting in a greater number of obese patients presenting for surgery. The combined problems of metabolic disease and mechanical impairment from excess tissues present a variety of problems for the anesthesiologist. RECENT FINDINGS: Obesity is associated with nonalcoholic fatty liver disease, dyslipidemia, hyperglycemia and type 2 diabetes. Metabolic syndrome, a constellation of findings associated with visceral obesity, appears to confer additional long-term risk. To date no intervention has proven effective in reducing perioperative risk, although statin therapy is promising. Obese patients are more difficult to intubate in the 'sniffing' position, but placed in the 'ramped' position there is no evidence that this risk is greater than in the general population. Obstructive sleep apnea is associated with adverse postoperative outcomes. Much research has focused on preventing postoperative atelectasis. Preoxygenation with continuous positive airway pressure (CPAP), recruitment maneuvers, intraoperative positive end-expiratory pressure of at least 8 cmH2O and postextubation CPAP appear to improve postoperative pulmonary function. SUMMARY: Current studies have focused on the immediate impact of obesity on anesthesia and postoperative care. Future research will focus primarily on perioperative metabolic optimization.

Noninvasive ventilation immediately after extubation improves lung function in morbidly obese patients with obstructive sleep apnea undergoing laparoscopic bariatric surgery.

BACKGROUND: Noninvasive positive pressure ventilation (NIPPV) may improve postoperative lung function and reduce postoperative complications in patients undergoing abdominal surgery. The purpose of our study was to determine whether the timing of postoperative NIPPV affects lung function 1 day postoperatively. METHODS: Forty morbidly obese patients with known obstructive sleep apnea undergoing laparoscopic bariatric surgery with standardized anesthesia care were randomly assigned to receive NIPPV immediately after tracheal extubation (immediate group) or supplemental oxygen (standard group). All patients had continuous positive airway pressure initiated 30 minutes after extubation in the postanesthesia care unit (PACU) via identical noninvasive ventilators. Spirometry was performed by a blinded observer in the perioperative holding area 1 hour after admission to the PACU and 1 day postoperatively. The primary outcome was the change in forced vital capacity (FVC) from baseline to 24 hours (FVC baseline-FVC 24 hours). RESULTS: Forty patients, 20 in each group, were enrolled in the study. Forced expiratory volume in 1 second, FVC, and peak expiratory flow rate were significantly reduced in both groups from perioperative values throughout the study. At 24 hours, the intervention group had lost only 0.7 L FVC, versus 1.3 L for the intervention group (P = 0.0005). An analysis of covariance confirmed this and indicated that the immediate postoperative NIPPV better preserved spirometric function at 1 and 24 hours postoperatively. Specifically, the differences in the primary outcome were statistically significant. CONCLUSIONS: NIPPV given immediately after extubation significantly improves spirometric lung function at 1 hour and 1 day postoperatively, compared with continuous positive airway pressure started in the PACU, in morbidly obese patients with obstructive sleep apnea undergoing laparoscopic bariatric surgery.

Obstructive sleep apnea is not a risk factor for difficult intubation in morbidly obese patients.

BACKGROUND: Morbid obesity (MO), obstructive sleep apnea (OSA), and neck circumference (NC) are widely believed to be independent risk factors for difficult tracheal intubation. In this study, we sought to determine whether these factors were associated with increased risk of difficult intubation in patients undergoing bariatric surgery. The predictive factors tested were OSA and its severity, as determined by apnea-hypopnea index (AHI), gender, NC, and body mass index (BMI). METHODS: All sequentially enrolled MO patients underwent preoperative polysomnography. Severity of OSA was quantified using AHI and the American Society of Anesthesiologists' OSA severity scale. All patients had a standardized anesthetic that included positioning in the "ramped position" for direct laryngoscopy. RESULTS: One hundred eighty consecutive patients were recruited, 140 women and 40 men. The incidence of OSA was 68%. The mean BMI was 49.4 kg/m(2). The mean AHI was 31.3 (range, 0-135). All the patients' tracheas were intubated successfully without the aid of rescue airways by anesthesiology residents. Six patients required three or more intubation attempts, a difficult intubation rate of 3.3%. There was an 8.3% incidence of difficult laryngoscopy, defined as a Cormack and Lehane Grade 3 or 4 view. There was no relationship between NC and difficult intubation (odds ratio 1.02, 95% confidence interval 0.93-1.1), between the diagnosis of OSA and difficult intubation (P = 0.09), or between BMI and difficult intubation (odds ratio 0.99, 95% confidence interval 0.92-1.06, P = 0.8). There was no relationship between number of intubation attempts and BMI (P = 0.8), AHI (P = 0.82), or NC (P = 0.3). Mallampati Grade III or more predicted difficult intubation (P = 0.02), as did male gender (P = 0.02). Finally, there was no relationship between Cormack and Lehane grade and BMI (P = 0.88), AHI (P = 0.93), or OSA (P = 0.6). Increasing NC was associated with difficult laryngoscopy but not difficult intubation (P = 0.02). CONCLUSIONS: In MO patients undergoing bariatric surgery in the "ramped position," there was no relationship between the presence and severity of OSA, BMI, or NC and difficulty of intubation or laryngoscopy grade. Only a Mallampati score of 3 or 4 or male gender predicted difficult intubation.

Continuous positive airway pressure via the Boussignac system immediately after extubation improves lung function in morbidly obese patients with obstructive sleep apnea undergoing laparoscopic bariatric surgery.

BACKGROUND: Morbidly obese patients are at elevated risk of perioperative pulmonary complications, including airway obstruction and atelectasis. Continuous positive airway pressure may improve postoperative lung mechanics and reduce postoperative complications in patients undergoing abdominal surgery. METHODS: Forty morbidly obese patients with known obstructive sleep apnea undergoing laproscopic bariatric surgery with standardized anesthesia care were randomly assigned to receive continuous positive airway pressure via the Boussignac system immediately after extubation (Boussignac group) or supplemental oxygen (standard care group). All subjects had continuous positive airway pressure initiated 30 min after extubation in the postanesthesia care unit via identical noninvasive ventilators. The primary outcome was the relative reduction in forced vital capacity from baseline to 24 h after extubation. RESULTS: Forty patients were enrolled into the study, 20 into each group. There were no significant differences in baseline characteristics between the groups. The intervention predicted less reduction in all measured lung functions: forced expiratory volume in 1 s (coefficient 0.37, SE 0.13, P = 0.003, CI 0.13-0.62), forced vital capacity (coefficient 0.39, SE 0.14, P = 0.006, CI 0.11-0.66), and peak expiratory flow rate (coefficient 0.82, SE 0.31, P = 0.008, CI 0.21-0.1.4). CONCLUSIONS: Administration of continuous positive airway pressure immediately after extubation maintains spirometric lung function at 24 h after laparoscopic bariatric surgery better than continuous positive airway pressure started in the postanesthesia care unit.

Prone positioning to treat acute severe pulmonary edema in the post-cardiac surgical patient: a case report.

Noncardiogenic pulmonary edema can be fatal without adequate resuscitation. We report, for the first time, the use of prone positioning in the immediate post-cardiac surgical period to treat a patient with profound hypoxemia secondary to massive (noncardiogenic) pulmonary edema. Prone positioning corrects ventilation-perfusion mismatch and allows gravity-dependent drainage of capillary leak-mediated endobronchial pulmonary fluid.

Nonsurgical and surgical treatment of obesity.

An increasing number of morbidly obese patients are presenting for surgery, with the potential for increased perioperative morbidity and mortality. This article reviews surgical and nonsurgical options in the management of morbidly obese patients. Overweight and obese individuals should be treated with diet, exercise, and behavioral therapy. The failure of this approach is an indication for pharmacologic therapy. Bariatric surgery reduces obesity-related complications and reduces long-term morbidity, mortality, and health care resources use.

Massive transfusion exceeding 50 units of blood products in trauma patients.

BACKGROUND: Massive transfusion of blood products in trauma patients can acutely deplete the blood bank. It was hypothesized that, despite a large allocation of resources to trauma patients receiving more than 50 units of blood products in the first 24 hours, outcome data would support the continued practice of massive transfusion. METHODS: A retrospective review of charts and registry data of trauma patients who received over 50 units of blood products in the first day was conducted for a 5-year period at a Level I trauma center. Patients were stratified into groups on the basis of the number of transfusions received. Results are expressed as mean +/- SD. Univariate analysis and multivariate logistic regression were used to identify those risk factors determined in the first 24 hours after admission that were predictive of mortality. Physiologic differences between survivors and nonsurvivors were also examined. RESULTS: Of 7,734 trauma patients admitted between July 1, 1995, and June 30, 2000, 44 (0.6%) received > 50 units of blood products in the first day. Overall mortality in these patients was 57%. There was no significant difference (p = 0.565, chi2) in mortality rate between patients who received > 75 units of blood products in the first day versus those who received 51 to 75 units. Multiple logistic regression analysis identified only one independent risk factor, base deficit > 12 mmol/L, associated with mortality. Base deficit > 12 mmol/L increases the risk of death by 5.5 times (p = 0.013; 95% confidence interval, 1.44-20.95). Neither the total blood product transfusion requirement in the first day nor the packed red blood cell transfusion amount in the first day were significant independent risk factors. Causes of the 25 deaths in this series included exsanguination in the operating room (n = 1) or in the surgical intensive care unit (n = 12), multiple organ failure/sepsis (n = 3), head injury (n = 3), respiratory failure (n = 2), cerebrovascular accident (n = 1), and other (n = 3). Of the survivors, 63% were discharged to home, 21% to rehabilitation, 11% to nursing home, and 5% to another acute care facility. Of the nonsurvivors, the mean Injury Severity Score was 43, 88% had a base deficit > 12 mmol/L, 68% had a Glasgow Coma Scale score < 8, and 64% had a Sequential Organ Failure Assessment score > 10. CONCLUSION: The 43% survival rate in trauma patients receiving > 50 units of blood products warrants continued aggressive transfusion therapy in the first 24 hours after admission.