Mary E. Warner

Clinical Significance of Pulmonary Aspiration during the Perioperative Period

BackgroundPulmonary aspiration of gastric contents during the perioperative period may be associated with postoperative mortality or pulmonary morbidity. Recent determination of the incidence of perioperative pulmonary aspiration and evaluation of factors related to clinical outcomes is lacking. MethodsWe retrospectively reviewed the perioperative courses of 172,334 consecutive patients 18 yr of age or older who underwent 215,488 general anesthetics for procedures performed in all surgical specialties from July 1985 to June 1991. Pulmonary aspiration was defined as either the presence of bilious secretions or particulate matter in the tracheobronchial tree or, in patients who did not have their tracheobronchial airways directly examined after regurgitation, the presence of an infiltrate on postoperative chest roentgenogram that was not identified by preoperative roentgenogram or physical examination. ResultsPulmonary aspiration occurred in 67 patients (1: 3,216 anesthetics). Fifteen aspirations occurred in 13,427 (1: 895) anesthetics of patients undergoing emergency surgery, and 52 occurred in 202,061 (1:3,886) anesthetics of patients undergoing elective surgery (P <.001). Of the 66 patients who survived their surgery, 42 (64%) did not develop a cough or wheeze, a decrease in arterial hemoglobin oxygen saturation while breathing room air >10% less than the preoperative value, or radiographic abnormalities within 2 h of aspiration. These 42 patients had no respiratory sequelae. Of the 24 patients who had one or more of these findings, 13 required mechanical ventilatory support for more than 6 h. Three of the six patients whose lungs required mechanical ventilation for more than 24 h died from pulmonary insufficiency (overall mortality = 1:71,829 anesthetics). ConclusionsThis study suggests that patients with clinically apparent aspiration who do not develop symptoms within 2 h are unlikely to have respiratory sequelae.

Perioperative Pulmonary aspiration in infants and children

BACKGROUND Pulmonary aspiration of gastric contents during the perioperative period in infants and children may be associated with postoperative mortality or pulmonary morbidity. There has not been a recent determination of the frequency of this event and its outcomes in infants and children. METHODS The authors prospectively identified all cases of pulmonary aspiration of gastric contents during the perioperative courses of 56,138 consecutive patients younger than 18 yr of age who underwent 63,180 general anesthetics for procedures performed in all surgical specialties from July 1985 through June 1997 at the Mayo Clinic. RESULTS Pulmonary aspiration occurred in 24 patients (1: 2,632 anesthetics; 0.04%). Children undergoing emergency procedures had a greater frequency of pulmonary aspiration compared to those undergoing elective procedures (1:373 vs. 1:4,544, P < 0.001). Fifteen of the 24 children who aspirated gastric contents did not develop respiratory symptoms within 2 h of aspiration, and none of these 15 developed pulmonary sequelae. Five of these nine children who aspirated and in whom respiratory symptoms developed within 2 h subsequently had pulmonary complications treated with respiratory support (P < 0.003). Three children were treated with mechanical ventilation for more than 48 h, but no child died of sequelae of pulmonary aspiration. CONCLUSIONS In this study population, the frequency of perioperative pulmonary aspiration in children was quite low. Serious respiratory morbidity was rare, and there were no associated deaths. Infants and children with clinically apparent pulmonary aspiration in whom symptoms did not develop within 2 h did not have respiratory sequelae.

Predictors of survival following Cardiac arrest in patients undergoing noncardiac surgery: A study of 518,294 patients at a tertiary referral center

Background The authors determined the incidence of cardiac arrest and predictors of survival following perioperative cardiac arrest in a large population of patients at a tertiary referral center. Methods Medical records of patients who experienced cardiac arrest in the perioperative period surrounding noncardiac surgery between January 1, 1990, and December 31, 2000, were reviewed. Logistic regression identified characteristics associated with immediate (≥ 1 h) and hospital survival, with P ≤ 0.01 considered statistically significant. Results Cardiac arrest occurred in 223 of 518,294 anesthetics (4.3 per 10,000) during the study period. Frequency of arrest for patients receiving general anesthesia decreased over time (7.8 per 10,000 during 1990–1992; 3.2 per 10,000 during 1998–2000). The frequency of arrest during regional anesthesia (1.5 per 10,000) and monitored anesthesia care (0.7 per 10,000) remained consistent. Immediate survival after arrest was 46.6%, and hospital survival was 34.5%. Twenty-four patients (0.5 per 10,000) had cardiac arrest related primarily to anesthesia. From multivariate analysis, patients who experienced arrest due to bleeding were less likely to survive hospitalization (P = 0.001). Survival was also lower for patients who experienced arrest during nonstandard working hours (P = 0.006) and for patients who had protracted hypotension before arrest (P < 0.001). Conclusions The overall frequency of arrest for patients receiving anesthesia decreased during the study period. Most arrests were not due to anesthesia-related causes, and most patients experiencing anesthesia-related arrest survived to hospital discharge. Although many factors determining survival may not be amenable to modification, the fact that arrests during nonregular working hours had worse outcomes may indicate that the availability of human resources influences survival.

Perianesthetic risks and outcomes of pheochromocytoma and paraganglioma resection

Pheochromocytomas and paragangliomas are often surgically curable. However, resection of these tumors can be life threatening. We undertook this study to determine the frequency of, and risk factors for, perioperative complications in patients undergoing resection of pheochromocytoma or paraganglioma. We retrospectively reviewed the medical records of patients during 1983–1996 who underwent surgical resection of catecholamine-secreting pheochromocytoma or paraganglioma. Preoperative risk factors, adverse intraoperative events, and complications occurring in the 30 days after operation were recorded. Blood pressures were collected from manual records. The ranked sum test and Fisher’s exact test were used for analyses. Adverse perioperative events or complications occurred in 45 of 143 patients (31.5%; exact 95% confidence interval, 24.0% to 39.8%). Of these 45 patients, 41 experienced one or more adverse intraoperative events. The most common adverse event was sustained hypertension (36 patients). There were no perioperative deaths, myocardial infarctions, or cerebrovascular events. Preoperative factors univariately associated with adverse perioperative events included larger tumor size (P = 0.007), prolonged duration of anesthesia (P = 0.015), and increased levels of preoperative urinary catecholamines and catecholamine metabolites: vanillylmandelic acid (P = 0.019), metanephrines (P = 0.004), norepinephrine (P = 0.014), and epinephrine (P = 0.004). Despite premedication of most patients with phenoxybenzamine and a &bgr;-adrenergic blocker, varying degrees of intraoperative hemodynamic lability occurred. Implications Few patients who had pheochromocytoma or paraganglioma resection experienced significant perioperative morbidity and none died in the largest retrospective study on this topic to date. This study confirms the very good perioperative outcomes demonstrated in smaller studies on this high-risk population, and identifies several risk factors for adverse outcomes.

perianesthetic Dental Injuries : Frequency, Outcomes, and Risk Factors

BACKGROUND Dental injury is well-recognized as a potential complication of laryngoscopy and tracheal intubation. However, the frequency, outcomes, and risk factors for this problem have not been documented in a well-defined patient population. METHODS The authors analyzed the dental injuries of 598,904 consecutive cases performed on patients who required anesthetic services from 1987 through 1997. Dental injuries were defined as perianesthetic events (those occurring within 7 days) that required dental interventions to repair, stabilize, or extract involved dentition or support structures. A 1:3 case-control study of 16 patient and procedural characteristics was performed for cases that occurred during the first 5 yr of the study. Conditional logistic regression was used for data analysis. RESULTS There were 132 cases (1:4,537 patients) of dental injury. One half of these injuries occurred during laryngoscopy and tracheal intubation. The upper incisors were the most commonly involved teeth, and most injuries were crown fractures and partial dislocations and dislodgements. Multivariate risk factors for dental injury in the case control study included general anesthesia with tracheal intubation (odds ratio [OR] = 89), preexisting poor dentition (OR = 50), and increased difficulty of laryngoscopy and intubation (OR = 11). CONCLUSIONS Based on these data from a large surgical population at a single training institution, approximately 1:4,500 patients who receive anesthesia services sustain a dental injury that requires repair or extraction. Patients most at risk for perianesthetic dental injury include those with preexisting poor dentition who have one or more risk factors for difficult laryngoscopy and tracheal intubation.

The frequency of perioperative vision loss

The frequency of perioperative vision loss, especially for spinal surgery, has been increasing recently. We undertook a retrospective study to determine the frequency of this outcome in a large surgical population receiving general or central neuraxis regional anesthesia for noncardiac procedures from 1986 to 1998. Specific criteria were used to separate cases in which the surgical procedure likely directly contributed to the vision loss. Vision loss was present if any part of the visual field was affected. Initial database screening found 405 cases of new-onset vision loss or visual changes in 410,189 patients who underwent 501,342 anesthetics and who survived at least 30 days after their final procedures. Two hundred sixteen of these patients regained full vision or acuity within 30 days. Of the 189 patients who developed vision deficits for longer than 30 days, 185 underwent ophthalmologic or neurologic procedures in which ocular or cerebral tissues were surgically damaged or resected. The remaining 4 patients (1 per 125,234 overall; 0.0008%) developed prolonged vision loss without direct surgical trauma to optic or cerebral tissues. In this large study population of noncardiac surgical patients, including those who underwent spinal surgical procedures, the frequency of perioperative vision loss persisting for longer than 30 days was very small.

Outcomes of patients with no laboratory assessment before anesthesia and a surgical procedure

OBJECTIVE To estimate the frequency of perioperative morbidities in patients who underwent anesthesia and a surgical procedure with no preoperative laboratory testing. MATERIAL AND METHODS We conducted an electronic database search of medical records of 56,119 patients who underwent surgical or diagnostic procedures and anesthesia at Mayo Clinic Rochester in 1994 and found 5,120 who had no laboratory tests done within 90 days before the procedure. From this group, we randomly selected 1,044 patients (87 from each month) to document the absence of preoperative tests, the presence of preexisting disease (by organ system), the type of anesthetic agent, and the outcomes and tests intraoperatively and postoperatively. RESULTS The 1,044 patients ranged in age from 0 to 95 years (median age, 21). No deaths or major perioperative morbidities occurred (0.0%; exact 95% confidence interval, 0.00 to 0.35%). Although 10 patients underwent blood typing and screening for antibodies immediately preoperatively, no blood transfusions were necessary. Intraoperatively, 17 laboratory tests and 1 electrocardiogram were obtained, and 3 results were abnormal. Postoperatively, 42 blood tests and 2 electrocardiographic procedures were performed. Five of the 42 blood tests showed abnormal results (hemoglobin levels in 3, serum sodium in 1, and arterial blood gases in 1). One electrocardiogram showed normal findings, and the other revealed normal results except for premature ventricular contractions. No laboratory test done intraoperatively or postoperatively was found to change surgical or medical management substantially. One patient who had unanticipated blood loss during an outpatient procedure was admitted to the hospital for observation. CONCLUSION All 1,044 patients, 97% of whom were relatively healthy, with no recent laboratory testing safely underwent anesthesia and an operation. We conclude that patients who have been assessed by history and physical examination and determined to have no preoperative indication for laboratory tests can safely undergo anesthesia and operation with tests obtained only as indicated intraoperatively and post-operatively. Current anesthetic and medical practices rapidly identify perioperative indications for laboratory evaluation as they arise.

Cardiac arrest during neuraxial anesthesia: frequency and predisposing factors associated with survival.

The frequency and predisposing factors associated with cardiac arrest during neuraxial anesthesia remain undefined, and the survival outcome data are contradictory. In this retrospective study, we evaluated the frequency of cardiac arrest, as well as the association of preexisting medical conditions and periarrest events with survival after cardiac arrest during neuraxial anesthesia between 1983 and 2002. To assess whether survival after cardiac arrest differs for patients who arrest during neuraxial versus general anesthesia, data were also obtained for patients who experienced cardiac arrest under general anesthesia during similar surgical procedures during the same time interval. Over the 20-yr study period at the Mayo Clinic, there were 26 cardiac arrests during neuraxial blockade and 29 during general anesthesia. The overall frequency of cardiac arrest during neuraxial anesthesia for 1988 to 2002 was 1.8 per 10,000 patients, with more arrests in patients receiving spinal versus epidural anesthesia (2.9 versus 0.9 per 10,000; P = 0.041). In 14 (54%) of the 26 patients who arrested during a neuraxial technique, the anesthetic contributed directly to the arrest (high sympathectomy or respiratory depression after sedative administration), whereas in 12 (46%) patients, the arrest was associated with a specific surgical event (cementing of joint components, spermatic cord manipulation, reaming of the femur, and rupture of amniotic membranes). Patients who arrested during general anesthesia had a higher ASA classification than those who arrested during a neuraxial block (P = 0.031). Hospital survival was significantly improved for patients who arrested during neuraxial anesthesia versus general anesthesia (65% vs 31%; P = 0.013). The association of improved survival with neuraxial anesthesia remained statistically significant after adjusting for all patient/procedural characteristics, with the exception of ASA classification and emergency procedures. We conclude that a cardiac arrest during neuraxial anesthesia is associated with an equal or better likelihood of survival than a cardiac arrest during general anesthesia.

Clinical Efficacy of High Frequency Jet Ventilation During Extracorporeal Shock Wave Lithotripsy of Renal and Ureteral Calculi: A Comparison with Conventional Mechanical Ventilation

The use of high frequency jet ventilation compared to conventional mechanical ventilation during general anesthesia for extracorporeal shock wave lithotripsy of renal or ureteral calculi can reduce stone movement. This decrease in stone movement theoretically lessens the total shock and energy requirements for stone fragmentation and perirenal tissue damage. To assess these theoretical advantages of high frequency jet ventilation, we studied patients undergoing extracorporeal shock wave lithotripsy to determine differences in stone movement during high frequency jet and conventional mechanical ventilation (30 patients), and in total shock requirements (1,174 patients). Mean stone movement in the 30 patients was 34.3 +/- 4.3 mm. during conventional mechanical ventilation compared to 4.1 +/- 1.9 mm. during high frequency jet ventilation (p less than 0.001). Mean total shocks were 1,542 +/- 212 (452 patients) during conventional mechanical ventilation compared to 1,217 +/- 165 (722 patients) during high frequency jet ventilation (p less than 0.001). Only 1 patient in the study had clinically significant perirenal tissue damage. We conclude that high frequency jet ventilation when compared to conventional mechanical ventilation results in clinically and economically beneficial decreases in total shocks for extracorporeal shock wave lithotripsy fragmentation of renal or ureteral calculi.

Compartment syndrome in surgical patients.

COMPARTMENT syndrome is a potentially devastating postoperative complication that can occur during or after surgery. It is a tissue injury that causes pain, erythema, edema, and hypoesthesia of the nerves in the affected area. In general, fasciotomy must follow clinical diagnosis quickly to prevent permanent tissue damage. If undiagnosed or diagnosed late, it may cause severe rhabdomyolysis, irreversible nerve deficits, loss of limb, or even death. A high proportion of cases have been reported to occur in patients undergoing surgical procedures while in the lithotomy position. Perioperative compartment syndrome for which there is no readily apparent cause (e.g., secondary to trauma or arterial embolism after vascular surgery) is not wellunderstood. Therefore, we reviewed the outcomes of a large number of surgical procedures to determine this complication’s frequency and to further characterize its natural history and outcomes.