Gravid status is not associated with postoperative nausea and vomiting: a matched case-control study.

BACKGROUND: Postoperative nausea and vomiting (PONV) is a common and unpleasant complication of general anesthesia. There are well-known risk factors that predispose a patient to develop PONV. While studies exist that explore PONV incidence in gravid and non-gravid women separately, limited studies exist to compare the two cohorts to identify if pregnancy is associated with increased risk for PONV or differences in PONV prophylaxis and treatment. METHODS: This is a retrospective case-control cohort study, with 1:2 matching based on age, year of surgery, and surgical procedure. Electronic medical records were abstracted for demographic information, predisposing risk factors, prophylactic antiemetics, PONV documentation, rescue antiemetics, PACU stay, and length of hospitalization. Analyses of risk factors for PONV were performed using logistic and multinomial logistic regression analyses. RESULTS: 237 gravid women who underwent non-obstetric procedures with general anesthesia were identified and matched with 474 non-gravid women. PONV complicated the course of 51 (21.5%) gravid and 72 (15.2%) non-gravid women. The number of prophylactic antiemetics was fewer among gravid (median 2 [1, 2]) than non-gravid (3 [2, 3]) women (P < 0.001). No association was found between gravid status and risk for PONV (adjusted odds ratio 1.35 [95%CI 0.84, 2.17], P = 0.222). Gravid women had longer hospital lengths of stay (P < 0.001), despite having shorter surgical duration (P = 0.015). CONCLUSIONS: The risk for PONV is similar between gravid and similarly aged women. However, anesthesiologists administer fewer prophylactic antiemetics to gravid women during non-obstetric surgery.

International multicentre review of perioperative management and outcome for catecholamine-producing tumours.

BACKGROUND: Surgery for catecholamine-producing tumours can be complicated by intraoperative and postoperative haemodynamic instability. Several perioperative management strategies have emerged but none has been evaluated in randomized trials. To assess this issue, contemporary perioperative management and outcome data from 21 centres were collected. METHODS: Twenty-one centres contributed outcome data from patients who had surgery for phaeochromocytoma and paraganglioma between 2000 and 2017. The data included the number of patients with and without α-receptor blockade, surgical and anaesthetic techniques, complications and perioperative mortality. RESULTS: Across all centres, data were reported on 1860 patients with phaeochromocytoma or paraganglioma, of whom 343 underwent surgery without α-receptor blockade. The majority of operations (78·9 per cent) were performed using minimally invasive techniques, including 16·1 per cent adrenal cortex-sparing procedures. The cardiovascular complication rate was 5·0 per cent overall: 5·9 per cent (90 of 1517) in patients with preoperative α-receptor blockade and 0·9 per cent (3 of 343) among patients without α-receptor blockade. The mortality rate was 0·5 per cent overall (9 of 1860): 0·5 per cent (8 of 517) in pretreated and 0·3 per cent (1 of 343) in non-pretreated patients. CONCLUSION: There is substantial variability in the perioperative management of catecholamine-producing tumours, yet the overall complication rate is low. Further studies are needed to better define the optimal management approach, and reappraisal of international perioperative guidelines appears desirable.

ANTECEDENTES: La cirugía de los tumores productores de catecolaminas puede complicarse por la inestabilidad hemodinámica intraoperatoria y postoperatoria. Se han propuesto distintas estrategias de manejo perioperatorio, pero ninguna ha sido evaluada en ensayos aleatorizados. Para evaluar este tema, se han recogido los datos de los resultados y del manejo perioperatorio contemporáneo de 21 centros. MÉTODOS: Veintiún centros aportaron datos de los resultados de los pacientes operados por feocromocitoma y paraganglioma entre 2000-2017. Los datos incluyeron el número de pacientes con y sin bloqueo del receptor α, las técnicas quirúrgicas y anestésicas, las complicaciones y la mortalidad perioperatoria. RESULTADOS: Los centros en su conjunto aportaron datos de 1.860 pacientes con feocromocitoma y paraganglioma, de los cuales 343 pacientes fueron intervenidos sin bloqueo del receptor α. La gran mayoría (79%) de las cirugías se realizaron utilizando técnicas mínimamente invasivas, incluido un 17% de procedimientos con preservación de la corteza suprarrenal. La tasa de complicaciones cardiovasculares fue de 5,0% en total; 5,9% (90/1517) en pacientes con bloqueo preoperatorio de los receptores α y 0,9% (3/343) en pacientes no pretratados. La mortalidad global fue del 0,5% (9/1860); 0,5% (8/1517) en pacientes pretratados y 0,3% (1/343) en pacientes no tratados previamente. CONCLUSIÓN: Existe una variabilidad sustancial en el manejo perioperatorio de los tumores productores de catecolaminas, aunque la tasa global de complicaciones es baja. Este estudio brinda la oportunidad para efectuar comparaciones sistemáticas entre estrategias de prácticas terapéuticas variables. Se necesitan más estudios para definir mejor el enfoque de manejo óptimo y parece conveniente volver a evaluar las guías internacionales perioperatorias.

Effect of Intraoperative High Positive End-Expiratory Pressure (PEEP) With Recruitment Maneuvers vs Low PEEP on Postoperative Pulmonary Complications in Obese Patients: A Randomized Clinical Trial.

Importance: An intraoperative higher level of positive end-expiratory positive pressure (PEEP) with alveolar recruitment maneuvers improves respiratory function in obese patients undergoing surgery, but the effect on clinical outcomes is uncertain. Objective: To determine whether a higher level of PEEP with alveolar recruitment maneuvers decreases postoperative pulmonary complications in obese patients undergoing surgery compared with a lower level of PEEP. Design, Setting, and Participants: Randomized clinical trial of 2013 adults with body mass indices of 35 or greater and substantial risk for postoperative pulmonary complications who were undergoing noncardiac, nonneurological surgery under general anesthesia. The trial was conducted at 77 sites in 23 countries from July 2014-February 2018; final follow-up: May 2018. Interventions: Patients were randomized to the high level of PEEP group (n = 989), consisting of a PEEP level of 12 cm H2O with alveolar recruitment maneuvers (a stepwise increase of tidal volume and eventually PEEP) or to the low level of PEEP group (n = 987), consisting of a PEEP level of 4 cm H2O. All patients received volume-controlled ventilation with a tidal volume of 7 mL/kg of predicted body weight. Main Outcomes and Measures: The primary outcome was a composite of pulmonary complications within the first 5 postoperative days, including respiratory failure, acute respiratory distress syndrome, bronchospasm, new pulmonary infiltrates, pulmonary infection, aspiration pneumonitis, pleural effusion, atelectasis, cardiopulmonary edema, and pneumothorax. Among the 9 prespecified secondary outcomes, 3 were intraoperative complications, including hypoxemia (oxygen desaturation with Spo2 ≤92% for >1 minute). Results: Among 2013 adults who were randomized, 1976 (98.2%) completed the trial (mean age, 48.8 years; 1381 [69.9%] women; 1778 [90.1%] underwent abdominal operations). In the intention-to-treat analysis, the primary outcome occurred in 211 of 989 patients (21.3%) in the high level of PEEP group compared with 233 of 987 patients (23.6%) in the low level of PEEP group (difference, -2.3% [95% CI, -5.9% to 1.4%]; risk ratio, 0.93 [95% CI, 0.83 to 1.04]; P = .23). Among the 9 prespecified secondary outcomes, 6 were not significantly different between the high and low level of PEEP groups, and 3 were significantly different, including fewer patients with hypoxemia (5.0% in the high level of PEEP group vs 13.6% in the low level of PEEP group; difference, -8.6% [95% CI, -11.1% to 6.1%]; P < .001). Conclusions and Relevance: Among obese patients undergoing surgery under general anesthesia, an intraoperative mechanical ventilation strategy with a higher level of PEEP and alveolar recruitment maneuvers, compared with a strategy with a lower level of PEEP, did not reduce postoperative pulmonary complications. Trial Registration: ClinicalTrials.gov Identifier: NCT02148692.

Agitation in adults in the post-anaesthesia care unit after general anaesthesia.

BACKGROUND: Agitation after general anaesthesia can lead to self-harm, violence against staff, and increased resource utilisation. We aimed to assess patient and procedural characteristics associated with this complication in adults. METHODS: We identified cases of agitation (Richmond Agitation-Sedation Scale score +3 or +4, or administration of haloperidol) in patients after general anaesthesia in the PACU from July 1, 2010 to September 30, 2016. The cases were matched 1:1 with control patients without agitation by age, sex, and procedure. Potential clinical associations were assessed with a multivariable analysis. RESULTS: We identified agitation in 510 patients [incidence: 2.5 cases/1000 patients; 95% confidence interval (CI): 2.3-2.7]. Variables associated with agitation were substance misuse [odds ratio (OR): 6.77; 95% CI: 1.23-37.2; P=0.03], cognitive impairment (OR: 4.66; 95% CI: 1.79-12.1; P=0.002), obesity (OR: 2.49; 95% CI: 1.66-3.73; P<0.001), psychiatric problems (OR: 2.05; 95% CI: 1.32-3.19; P=0.002), fall risk (OR: 1.66; 95% CI: 1.02-2.70; P=0.04), postoperative presence of a tracheal tube (OR: 16.6; 95% CI: 7.25-38.2; P<0.001), urine catheter (OR: 7.25; 95% CI: 4.31-12.2; P<0.001), nasogastric tube (OR: 4.06; 95% CI: 1.51-10.9; P=0.006), or chest tube (OR: 3.46; 95% CI: 1.07-11.2; P=0.006). Compared with control patients, more agitated patients had postoperative delirium (16.1% vs 6.3%; P<0.001) and pulmonary complications (9.8% vs 4.7%; P=0.002). CONCLUSIONS: Agitation after general anaesthesia was associated with postoperative indwelling catheters, tracheal intubation and patient features suggestive of pre-existing mental health problems. Anticipation of high-risk patients could allow allocation of staffing resources to provide a safe environment for anaesthetic recovery.

Pattern of perioperative gabapentinoid use and risk for postoperative naloxone administration.

BACKGROUND: Single preoperative gabapentinoid (gabapentin and pregabalin) administration has been associated with respiratory depression during Phase I anaesthesia recovery. In this study, we assess for associations between chronic (home) use and perioperative administration (preoperative and postoperative) of gabapentinoids, and risk for severe over-sedation or respiratory depression as inferred from the use of naloxone. METHODS: From 2011 to 2016, we identified patients undergoing general anaesthesia discharged to standard postoperative wards and administered naloxone within 48 h of surgery in a single centre. These patients were 2:1 matched on age, sex, and type of procedure. Patient and perioperative characteristics were abstracted and compared to assess for risk for naloxone administration. RESULTS: We identified 128 patients that received naloxone after operation [odds ratio 1.2; 95% confidence interval (CI) 1.0, 1.4 per 1000 general anaesthetics]. Patients on chronic or postoperative gabapentinoid therapy were at significantly higher risk for receiving naloxone after operation. Multivariable analysis detected significant interactions between chronic and postoperative use of gabapentinoids, where continuation of chronic gabapentinoid medications into the postoperative period was associated with an increased rate of naloxone administration (6.30, 95% CI 2.4, 16.7; P=0.001). Obstructive sleep apnoea (P=0.005) and preoperative disability (P=0.003) were also associated with an increased risk for postoperative naloxone administration. Patients who received naloxone had longer hospital stays and higher rates of postoperative delirium. CONCLUSIONS: Continuation of chronic gabapentinoid medications into the postoperative period is associated with the increased use of naloxone to reverse over-sedation or respiratory depression. Such patients requiring this therapy warrant high levels of postoperative monitoring.

Association between exposure to anaesthesia and surgery and long-term cognitive trajectories in older adults: report from the Mayo Clinic Study of Aging.

BACKGROUND: The link between exposure to general anaesthesia and surgery (exposure) and cognitive decline in older adults is debated. We hypothesised that it is associated with cognitive decline. METHODS: We analysed the longitudinal cognitive function trajectory in a cohort of older adults. Models assessed the rate of change in cognition over time, and its association with exposure to anaesthesia and surgery. Analyses assessed whether exposure in the 20 yr before enrolment is associated with cognitive decline when compared with those unexposed, and whether post-enrolment exposure is associated with a change in cognition in those unexposed before enrolment. RESULTS: We included 1819 subjects with median (25th and 75th percentiles) follow-up of 5.1 (2.7-7.6) yr and 4 (3-6) cognitive assessments. Exposure in the previous 20 yr was associated with a greater negative slope compared with not exposed (slope: -0.077 vs -0.059; difference: -0.018; 95% confidence interval: -0.032, -0.003; P=0.015). Post-enrolment exposure in those previously unexposed was associated with a change in slope after exposure (slope: -0.100 vs -0.059 for post-exposure vs pre-exposure, respectively; difference: -0.041; 95% confidence interval: -0.074, -0.008; P=0.016). Cognitive impairment could be attributed to declines in memory and attention/executive cognitive domains. CONCLUSIONS: In older adults, exposure to general anaesthesia and surgery was associated with a subtle decline in cognitive z-scores. For an individual with no prior exposure and with exposure after enrolment, the decline in cognitive function over a 5 yr period after the exposure would be 0.2 standard deviations more than the expected decline as a result of ageing. This small cognitive decline could be meaningful for individuals with already low baseline cognition.

Postoperative delirium in elderly patients is associated with subsequent cognitive impairment.

BACKGROUND: We examined the risk for postoperative delirium (POD) in patients with mild cognitive impairment (MCI) or dementia, and the association between POD and subsequent development of MCI or dementia in cognitively normal elderly patients. METHODS: Patients ≥65 yr of age enrolled in the Mayo Clinic Study of Aging who were exposed to any type of anaesthesia from 2004 to 2014 were included. Cognitive status was evaluated before and after surgery by neuropsychological testing and clinical assessment, and was defined as normal or MCI/dementia. Postoperative delirium was detected with the Confusion Assessment Method for the intensive care unit. Logistic regression analyses were performed. RESULTS: Among 2014 surgical patients, 74 (3.7%) developed POD. Before surgery, 1667 participants were cognitively normal, and 347 met MCI/dementia criteria. The frequency of POD was higher in patients with pre-existing MCI/dementia compared with no MCI/dementia {8.7 vs 2.6%; odds ratio (OR) 2.53, [95% confidence interval (CI) 1.52-4.21]; P <0.001}. Postoperative delirium was associated with lower education [OR, 3.40 (95% CI, 1.60-7.40); P =0.002 for those with <12 vs ≥16 yr of schooling]. Of the 1667 patients cognitively normal at their most recent assessment, 1152 returned for postoperative evaluation, and 109 (9.5%) met MCI/dementia criteria. The frequency of MCI/dementia at the first postoperative evaluation was higher in patients who experienced POD compared with those who did not [33.3 vs 9.0%; adjusted OR, 3.00 (95% CI, 1.12-8.05); P =0.029]. CONCLUSIONS: Mild cognitive impairment or dementia is a risk for POD. Elderly patients who have not been diagnosed with MCI or dementia but experience POD are more likely to be diagnosed subsequently with MCI or dementia.

Association between neuraxial analgesia, cancer progression, and mortality after radical prostatectomy: a large, retrospective matched cohort study.

BACKGROUND: Systemic opioids are immunosuppressive, which could promote tumour recurrence. We, therefore, test the hypothesis that supplementing general anaesthesia with neuraxial analgesia improves long-term oncological outcomes in patients having radical prostatectomy for adenocarcinoma. METHODS: Patients who had general anaesthesia with neuraxial analgesia (n=1642) were matched 1:1 based on age, surgical year, pathological stage, Gleason scores, and presence of lymph node disease with those who had general anaesthesia only. Medical records were reviewed. Outcomes of interest were systemic cancer progression, recurrence, prostate cancer mortality, and all-cause mortality. Data were analysed using stratified proportional hazards regression, the Kaplan-Meier method, and log-rank tests. The median follow-up was 9 yr. RESULTS: After adjusting for comorbidities, positive surgical margins, and adjuvant hormonal and radiation therapies within 90 postoperative days, general anaesthesia only was associated with increased risk for systemic progression [hazard ratio (HR)=2.81, 95% confidence interval (CI) 1.31-6.05; P=0.008] and higher overall mortality (HR=1.32, 95% CI 1.00-1.74; P=0.047). Although not statistically significant, similar findings were observed for the outcome of prostate cancer deaths (adjusted HR=2.2, 95% CI 0.88-5.60; P=0.091). CONCLUSIONS: This large retrospective analysis suggests a possible beneficial effect of regional anaesthetic techniques on oncological outcomes after prostate surgery for cancer; however, these findings need to be confirmed (or refuted) in randomized trials.

Obesity trends in the surgical population at a large academic center : a comparison between 1989-1991 to 2006-2008 epochs.

BACKGROUND: Changes in the prevalence of obesity of surgical patients overtime and in relation to the general population have not been well characterized. METHODS: Height, weight, age and gender data of adult patients who underwent general anesthesia at our institution were abstracted. Reliable data was available for the years 1989-1991 and 2006-2008, and comparisons were made between these epochs. Additional comparisons were made between our Minnesota surgical patients and the general Minnesota population. RESULTS: Substantial changes in patient weight occurred with a decline in normal weight patients (body mass index [BMI] < or =25.0) from 41.6% to 30.9% (P <0.001), while the prevalence of obesity (BMI 30-34.9) increased from 14.9% to 20.6% (P <0.001) and morbidly obesity (BMI > 35) from 7.1% to 14.8% (P <0.001). Minnesota surgical patients had a higher prevalence of obesity in every demographic category (P <0.001) compared to the general population. CONCLUSION: A substantial increase in the prevalence of obesity and morbid obesity among surgical patients at our institution occurred and the prevalence of obesity in our contemporary practice is higher than the general population. These observations most likely have profound implications on healthcare delivery resources, though its impact has yet to be determined.

Obstructive sleep apnoea and perioperative complications in bariatric patients.

BACKGROUND: The objective of this study was to determine the relationship between perioperative complications and the severity of obstructive sleep apnoea (OSA) in patients undergoing bariatric surgery who had undergone preoperative polysomnography (PSG). METHODS: The records of 797 patients, age >18 yr, who underwent bariatric operations (442 open and 355 laparoscopic procedures) at Mayo Clinic and were assessed before operation by PSG, were reviewed retrospectively. OSA was quantified using the apnoea-hypopnoea index (AHI) as none (≤ 4), mild (5-15), moderate (16-30), and severe (≥ 31). Pulmonary, surgical, and 'other' complications within the first 30 postoperative days were analysed according to OSA severity. Logistic regression was used to assess the multivariable association of OSA, age, sex, BMI, and surgical approach with postoperative complications. RESULTS: Most patients with OSA (93%) received perioperative positive airway pressure therapy, and all patients were closely monitored after operation with pulse oximetry on either regular nursing floors or in intensive or intermediate care units. At least one postoperative complication occurred in 259 patients (33%). In a multivariable model, the overall complication rate was increased with open procedures compared with laparoscopic. In addition, increased BMI and age were associated with increased likelihood of pulmonary and other complications. Complication rates were not associated with OSA severity. CONCLUSIONS: In obese patients evaluated before operation by PSG before bariatric surgery and managed accordingly, the severity of OSA, as assessed by the AHI, was not associated with the rate of perioperative complications. These results cannot determine whether unrecognized and untreated OSA increases risk.

Comparison of two ventilatory strategies in elderly patients undergoing major abdominal surgery.

BACKGROUND: 'Open lung' ventilation is commonly used in patients with acute lung injury and has been shown to improve intraoperative oxygenation in obese patients undergoing laparoscopic surgery. The feasibility of an 'open lung' ventilatory strategy in elderly patients under general anaesthesia has not previously been assessed. METHODS: 'Open lung' ventilation (recruitment manoeuvres, tidal volume 6 ml kg(-1) predicted body weight, and 12 cm H(2)O PEEP) (RM group) was compared with conventional ventilation (no recruitment manoeuvres, tidal volume 10 ml kg(-1) predicted body weight, and zero end-expiratory pressure) in elderly patients (>65 yr) undergoing major open abdominal surgery with regard to oxygenation, respiratory system mechanics, and haemodynamic stability. We also monitored the serum levels of the interleukins (IL)-6 and IL-8 before and after surgery to determine whether the systemic inflammatory response to surgery depends on the ventilatory strategy used. RESULTS: Twenty patients were included in each group. The RM group tolerated open lung ventilation without significant haemodynamic instability. Intraoperative Pa(o(2)) improved in the RM group (P<0.01) and deteriorated in controls (P=0.01), but postoperative Pa(o(2)) was similar in both groups. The RM group had improved breathing mechanics as evidenced by increased dynamic compliance (36%) and decreased airway resistance (21%). Both IL-6 and IL-8 significantly increased after surgery, but the magnitude of increase did not differ between the groups. CONCLUSIONS: A lung recruitment strategy in elderly patients is well tolerated and improves intraoperative oxygenation and lung mechanics during laparotomy.

Intraoperative ventilator settings and acute lung injury after elective surgery: a nested case control study.

BACKGROUND: While acute lung injury (ALI) is among the most serious postoperative pulmonary complications, its incidence, risk factors and outcome have not been prospectively studied. OBJECTIVE: To determine the incidence and survival of ALI associated postoperative respiratory failure and its association with intraoperative ventilator settings, specifically tidal volume. DESIGN: Prospective, nested, case control study. SETTING: Single tertiary referral centre. PATIENTS: 4420 consecutive patients without ALI undergoing high risk elective surgeries for postoperative pulmonary complications. MEASUREMENTS: Incidence of ALI, survival and 2:1 matched case control comparison of intraoperative exposures. RESULTS: 238 (5.4%) patients developed postoperative respiratory failure. Causes included ALI in 83 (35%), hydrostatic pulmonary oedema in 74 (31%), shock in 27 (11.3%), pneumonia in nine (4%), carbon dioxide retention in eight (3.4%) and miscellaneous in 37 (15%). Compared with match controls (n = 166), ALI cases had lower 60 day and 1 year survival (99% vs 73% and 92% vs 56%; p<0.001). Cases were more likely to have a history of smoking, chronic obstructive pulmonary disease and diabetes, and to be exposed to longer duration of surgery, intraoperative hypotension and larger amount of fluid and transfusions. After adjustment for non-ventilator parameters, mean first hour peak airway pressure (OR 1.07; 95% CI 1.02 to 1.15 cm H(2)O) but not tidal volume (OR 1.03; 95% CI 0.84 to 1.26 ml/kg), positive end expiratory pressure (OR 0.89; 95% CI 0.77 to 1.04 cm H(2)O) or fraction of inspired oxygen (OR 1.0; 95% CI 0.98 to 1.03) were associated with ALI. CONCLUSION: ALI is the most common cause of postoperative respiratory failure and is associated with markedly lower postoperative survival. Intraoperative tidal volume was not associated with an increased risk for early postoperative ALI.

Protective intraoperative ventilation with higher versus lower levels of positive end-expiratory pressure in obese patients (PROBESE): study protocol for a randomized controlled trial.

BACKGROUND: Postoperative pulmonary complications (PPCs) increase the morbidity and mortality of surgery in obese patients. High levels of positive end-expiratory pressure (PEEP) with lung recruitment maneuvers may improve intraoperative respiratory function, but they can also compromise hemodynamics, and the effects on PPCs are uncertain. We hypothesized that intraoperative mechanical ventilation using high PEEP with periodic recruitment maneuvers, as compared with low PEEP without recruitment maneuvers, prevents PPCs in obese patients. METHODS/DESIGN: The PRotective Ventilation with Higher versus Lower PEEP during General Anesthesia for Surgery in OBESE Patients (PROBESE) study is a multicenter, two-arm, international randomized controlled trial. In total, 2013 obese patients with body mass index ≥35 kg/m2 scheduled for at least 2 h of surgery under general anesthesia and at intermediate to high risk for PPCs will be included. Patients are ventilated intraoperatively with a low tidal volume of 7 ml/kg (predicted body weight) and randomly assigned to PEEP of 12 cmH2O with lung recruitment maneuvers (high PEEP) or PEEP of 4 cmH2O without recruitment maneuvers (low PEEP). The occurrence of PPCs will be recorded as collapsed composite of single adverse pulmonary events and represents the primary endpoint. DISCUSSION: To our knowledge, the PROBESE trial is the first multicenter, international randomized controlled trial to compare the effects of two different levels of intraoperative PEEP during protective low tidal volume ventilation on PPCs in obese patients. The results of the PROBESE trial will support anesthesiologists in their decision to choose a certain PEEP level during general anesthesia for surgery in obese patients in an attempt to prevent PPCs. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT02148692. Registered on 23 May 2014; last updated 7 June 2016.

Outcome of adult cardiopulmonary resuscitations at a tertiary referral center including results of "limited" resuscitations.

BACKGROUND: The results of in-hospital resuscitations may depend on a variety of factors related to the patient, the environment, and the extent of resuscitation efforts. We studied these factors in a large tertiary referral hospital with a dedicated certified resuscitation team responding to all cardiac arrests. METHODS: Statistical analysis of 445 prospectively recorded resuscitation records of patients who experienced cardiac arrest and received advanced cardiac life support resuscitation. We also report the outcomes of an additional 37 patients who received limited resuscitation efforts because of advance directives prohibiting tracheal intubation, chest compressions, or both. MAIN OUTCOME MEASURES: Survival immediately after resuscitation, at 24 hours, at 48 hours, and until hospital discharge. RESULTS: Overall, 104 (23%) of 445 patients who received full advanced cardiac life support survived to hospital discharge. Survival was highest for patients with primary cardiac disease (30%), followed by those with infectious diseases (15%), with only 8% of patients with end-stage diseases surviving to hospital discharge. Neither sex nor age affected survival. Longer resuscitations, increased epinephrine and atropine administration, multiple defibrillations, and multiple arrhythmias were all associated with poor survival. Patients who experienced arrests on a nursing unit or intensive care unit had better survival rates than those in other hospital locations. Survival for witnessed arrests (25%) was significantly better than for nonwitnessed arrests (7%) (P =.005). There was a disproportionately high incidence of nonwitnessed arrests during the night (12 AM to 6 AM) in unmonitored beds, resulting in uniformly poor survival to hospital discharge (0%). None of the patients whose advance directives limited resuscitation survived. CONCLUSIONS: Very ill patients in unmonitored beds are at increased risk for a nonwitnessed cardiac arrest and poor resuscitation outcome during the night. Closer vigilance of these patients at night is warranted. The outcome of limited resuscitation efforts is very poor.

Endotracheal tube and tracheobronchial obstruction as causes of hypoventilation with high inspiratory pressures.

Two cases of difficult ventilation are presented, the first caused by endotracheal tube obstruction with nasal turbinate, and the second caused by tracheobronchial obstruction with blood clots. The clinical presentation in each case was characterized by extreme difficulty in ventilating and severe hypercapnia despite vigorous ventilatory efforts with either a mechanical ventilator or resuscitator bag. A simple manipulation of the endotracheal tube cuff helped to differentiate between increased impedance caused by endotracheal tube obstruction as opposed to increased respiratory system impedance beyond the tip of tube. In the second patient, in whom even a short interruption of ventilation was poorly tolerated, simultaneous rigid bronchoscopy (for removal of intratracheal masses) and ventilation via endotracheal tube were successfully performed.

Treatment of a bronchopleural fistula with a Fogarty catheter and oxidized regenerated cellulose (surgicel).

A patient with bronchopleural fistula was successfully treated by occluding the fistula with an inflated Fogarty catheter balloon packed with oxidized regenerated cellulose (Surgicel) using a fiberoptic bronchoscope. After 48 h, the balloon was deflated, the fistula had sealed, and the patient did well. This simple and relatively noninvasive therapy was effective in this patient who was not a surgical candidate.

Effects of mean airway pressure and tidal volume on lung and chest wall mechanics in the dog.

Dependencies of the dynamic mechanical properties of the respiratory system on mean airway pressure (Paw) and the effects of tidal volume (VT) are not completely clear. We measured resistance and dynamic elastance of the total respiratory system (Rrs and Ers), lungs (RL and EL), and chest wall (Rcw and Ecw) in six healthy anesthetized paralyzed dogs during sinusoidal volume oscillations at the trachea (50-300 ml; 0.4 Hz) delivered at mean Paw from -9 to +23 cmH2O. Changes in end-expiratory lung volume, estimated with inductance plethysmographic belts, showed a typical sigmoidal relationship to mean Paw. Each dog showed the same dependencies of mechanical properties on mean Paw and VT. All elastances and resistances were minimal between 5 and 10 cmH2O mean Paw. All elastances, Rrs, and RL increased greatly with decreasing Paw below 5 cmH2O. Ers and EL increased above 10 cmH2O. Ecw, Ers, Rcw, and Rrs decreased slightly with increasing VT, but RL and EL were independent of VT. We conclude that 1) respiratory system impedance is minimal at the normal mean lung volume of supine anesthetized paralyzed dogs; 2) the dependency of RL on lung volume above functional residual capacity is dependent on VT and respiratory frequency; and 3) chest wall, but not lung, mechanical behavior is nonlinear (i.e., VT dependent) at any given lung volume.

Determinants of transdiaphragmatic pressure in dogs.

We measured the transdiaphragmatic pressure (Pdi) during bilateral phrenic nerve stimulation and evaluated the determinants of its change with lung volume, chest wall geometry, and respiratory system impedance in supine dogs. Four rows of radiopaque markers were sewn onto muscle bundles of the costal and crural diaphragm between their origin on the central tendon and their insertion on the rib cage and spine. The length of the diaphragm (L) was determined from the projection images of marker rows using biplane fluoroscopy. Measurements were made at lung volumes between total lung capacity and functional residual capacity before and after the infusion of Ringer lactate solution into the abdominal cavity. In contrast to relaxation, during tetanic stimulation the active lengths of the muscle bundles were similar at all volumes, but the diaphragm assumed different shapes. Although the small differences in active muscle length with volume and liquid loads are consistent with only small changes in muscle force output, Pdi varied by a factor of greater than or equal to 5. There was no single L/Pdi curve that fitted all data during 50-Hz stimulations. We conclude that under these experimental conditions Pdi is not a unique measure of the force produced by the diaphragm and that lung volume, chest wall geometry, and respiratory system impedance are important determinants of the mechanical efficiency of the diaphragm as a pressure generator.

Lung tissue and airway impedances during pulmonary edema in normal range of breathing.

How pulmonary edema affects lung tissue and airway properties is not clear. From measurements of airway pressure and flow, we measured lung elastance (EL) and resistance (RL) in 5 anesthetized-paralyzed open-chested dogs during sinusoidal forcing in the frequency (f) and tidal volume (VT) ranges of normal breathing. RL was divided into its tissue (Rti) and airway (Raw) components from measurements of alveolar pressure through capsules glued to the lung surface. After induction of severe pulmonary edema by injection of oleic acid into the right atrium, forcing was repeated at the same mean airway pressure (Paw) as in control animals (11 cmH2O) and at a higher Paw (14 cmH2O), as would occur in closed-chested dogs during edema (G. M. Barnas, D. Stamenovic, and K. R. Lutchen. J. Appl. Physiol. 73: 1040-1046, 1992). Edema increased EL, and this increase was greater at Paw = 14 cmH2O (P < 0.05). The f dependences of EL and Rti were increased by edema (P < 0.05), and there was a large negative dependence of EL on VT at Paw = 14 cmH2O. Edema increased RL (P < 0.05), but this increase depended on f, VT, and Paw. The increase in RL was due largely to increases in Rti at Paw = 14 cmH2O and to increases in Raw at Paw = 11 cmH2O. We conclude that the functional effects of oleic acid-induced pulmonary edema on RL are due mostly to changes in lung tissue.

Effect of body position on regional diaphragm function in dogs.

The in situ lengths of muscle bundles of the crural and three regions of the costal diaphragm between origin and insertion were determined with a video roentgenographic technique in dogs. At total lung capacity (TLC) in both the prone and supine positions, the length of the diaphragm is not significantly different from the unstressed excised length, suggesting that the diaphragm is not under tension at TLC and that there is a hydrostatic gradient of pleural pressure on the diaphragmatic surface. Except for the ventral region of the costal diaphragm, which does not change length at lung volumes greater than 70% TLC, all other regions are stretched during passive deflations from TLC. Therefore below TLC the diaphragm is under passive tension and supports a transdiaphragmatic pressure (Pdi). The length of the diaphragm relative to its unstressed length is not uniform at functional residual capacity (FRC) and does not follow a strict vertical gradient that reverses when the animal is changed from the supine to the prone position. By inference, the length of muscle bundles is determined by factors other than the vertical gradient of Pdi. During mechanical ventilation, regional shortening is identical to the passive deflation length-volume relationship near FRC. Prone and supine FRC is the same, but the diaphragm is slightly shorter in the prone position. In both positions, during spontaneous ventilation there are no consistent differences in regional fractional shortening, despite regional differences in initial length relative to unstressed length.