Mark A. 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.

Effect of Various Lithotomy Positions on Lower-extremity Blood Pressure

Background Compartment syndrome of a lower extremity from hypoperfusion is a rare but potentially devastating complication of the lithotomy position during surgery. The aim of this study is to determine the effects of various lithotomy positions on lower‐extremity blood pressures. Methods Blood pressure in eight young, healthy people was studied for 10 lithotomy positions. Blood pressure measurements were taken in both the upper arm (brachial artery) and the lower extremity (dorsalis pedis). The heart‐to‐ankle height gradient in each position was measured, and a predicted lower‐extremity systolic pressure was calculated. The measured and predicted lower‐extremity systolic blood pressures were compared with repeated measures analysis of variance. Results As a group, the mean systolic blood pressures in the lower extremities correlated closely with the predicted values. However, the difference between measured and predicted pressures varied among the 10 positions (P < 0.05). Conclusions Although lower‐extremity systolic blood pressures in the young, healthy volunteers correlated with predicted values, there was an additional reduction in pressure associated with the lithotomy position. This surprising finding suggests that a lengthy procedure necessitating the use of a lithotomy position for only a portion should be planned so the remainder of the procedure can take place before establishing the position or so the position can be changed to an alternative position when it is no longer needed.

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.

Perioperative Respiratory Complications in Patients with Asthma

Background Patients with asthma are thought to be at high risk for pulmonary complications to develop during the perioperative period, and these complications may lead to serious morbidity. Existing medical records were reviewed to determine the frequency of and risk factors for perioperative pulmonary complications in a cohort of residents of Rochester, Minnesota, who had asthma and who underwent anesthesia and surgery at the Mayo Clinic in Rochester. Methods Medical records were reviewed for all residents of Rochester, Minnesota, who were initially diagnosed as having definite asthma according to strict criteria from 1 January 1964 through 31 December 1983 who subsequently had at least one surgical procedure involving a general anesthetic or central neuroaxis block at the Mayo Clinic (n = 706). Results Bronchospasm was documented in the perioperative records of 12 patients (1.7% [exact 95% confidence interval, 0.9 to 3%]). Postoperative respiratory failure developed in one of these patients. Laryngospasm developed in two additional patients during operation. All episodes of bronchospasm and laryngospasm in the immediate perioperative period were treated successfully. No episodes of pneumothorax, pneumonia, or death in the hospital were noted. For univariate analysis, characteristics associated with complications included the recent use of antiasthmatic drugs, recent asthma symptoms, and recent therapy in a medical facility for asthma. Patients in whom complications developed were significantly older at diagnosis and at surgery. Conclusions The frequency of perioperative bronchospasm and laryngospasm was surprisingly low in this cohort of persons with asthma. These complications did not lead to severe respiratory outcomes in most patients. The frequency of complications was increased in older patients and in those with active asthma.

Perioperative Management of Pheochromocytoma

Pheochromocytomas are rare neuroendocrine tumors that produce and store catecholamines. Without adequate preparation, the release of excessive amounts of catecholamines, especially during anesthetic induction or during surgical removal, can produce life-threatening cardiovascular complications. This review focuses on the perioperative management of pheochromocytoma/paragangliomas, initially summarizing the clinical aspects of the disease and then highlighting the current evidence available for preoperative, intraoperative, and postoperative anesthetic management.PHEOCHROMOCYTOMAS ARE pharmacologically volatile, potentially lethal catecholamine-containing tumors of chromaffin tissue.1 They are usually found in the adrenal medulla, but they may occur wherever chromaffin tissue is located. Chromaffin cells are associated with the celiac, mesenteric, renal, adrenal, hypogastric, testicular, and paravertebral sympathetic nerve plexus. The major sites where pheochromocytomas occur are the adrenal medulla (90%), the paraganglia cells of the sympathetic nervous system, and the organ of Zuckerkandl.2 Approximately 10% of sporadic and 50% of familial adrenal tumors are bilateral, and approximately 10% of pheochromocytomas are multiple in location at the time of presentation.3 Paragangliomas are derived from neural crest cells that migrate in close association with autonomic ganglion cells, and all paragangliomas have the capacity to secrete catecholamines.4,5 Functional paragangliomas that secrete norepinephrine can occur and present similarly to pheochromocytoma. The proportion of catecholamine-secreting paragangliomas is thought to be high for adrenal pheochromocytomas, intermediate for aorticosympathetic and visceroautonomic tumors, and low for paragangliomas of the head and neck, also known as glomus tumors.5 Paragangliomas may present as painless swellings in the neck overlying the carotid bifurcation. These are also called carotid body tumors or chemodectomas.5 Of paragangliomas, 10% are malignant, but they can be locally invasive and can cause cranial nerve palsies.4 The resection of a pheochromocytoma or biochemically active paraganglioma has great potential for intraoperative and postoperative complications owing to release of catecholamines during manipulation of the tumor. Significant hemodynamic and metabolic effects are associated with a sudden decrease in catecholamine levels after removal of a tumor.6 In a series of 138 patients undergoing resection of pheochromocytoma tumors in a variety of anatomic locations between 1926 and 1970, surgical mortality was 2.9%.7 Desmonts et al8 reported a 3.9% mortality rate in their series of 102 patients between 1964 and 1976. A more recent series of 143 patients who underwent pheochromocytoma or paraganglioma resection showed no mortality and the absence of perioperative myocardial infarctions or cerebrovascular accidents.9 Advances in localization techniques, medical management, and anesthetic management have resulted in improved surgical outcomes.10 PRESENTATION

Lower extremity neuropathies associated with lithotomy positions

BackgroundThe goal of this project was to study the frequency and natural history of perioperative lower extremity neuropathies. MethodsA prospective evaluation of lower extremity neuropathies in 991 adult patients undergoing general anesthetics and surgical procedures while positioned in lithotomy was performed. Patients were assessed with use of a standard questionnaire and neurologic examination before surgery, daily during hospital stay in the first week after surgery, and by phone if discharged before 1 postoperative week. Patients in whom lower extremity neuropathies developed were observed for 6 months. ResultsLower extremity neuropathies developed in 15 patients (1.5%; 95% confidence interval, 0.8–2.5%). Unilateral or bilateral nerves were affected in patients as follows: obturator (five patients), lateral femoral cutaneous (four patients), sciatic (three patients), and peroneal (three patients). Paresthesia occurred in 14 of 15 patients, and 4 patients had burning or aching pain. No patient had weakness. Symptoms were noted within 4 h of completion of the anesthetic in all 15 patients. These symptoms resolved within 6 months in 14 of 15 patients. Prolonged positioning in a lithotomy position, especially for more than 2 h, was a major risk factor for this complication (P = 0.006). ConclusionsIn this surgical population, lower extremity neuropathies were infrequent complications that were noted very soon after surgery and anesthesia. None resulted in prolonged disability. The longer patients were positioned in lithotomy positions, the greater the chance of development of a neuropathy. These findings suggest that a reduction of duration of time in lithotomy positions may reduce the risk of lower extremity neuropathies.

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.

Preoperative Laboratory Screening in Healthy Mayo Patients: Cost-Effective Elimination of Tests and Unchanged Outcomes

We reviewed the results of preoperative screening laboratory tests in asymptomatic healthy patients who underwent elective surgical procedures at our institution in 1988. Substantially abnormal results were found in 160 of 3,782 patients. All such abnormalities involved five tests: aspartate aminotransferase, glucose, potassium, platelet count, and hemoglobin. Thirty of the abnormal test results were predictable on the basis of the history or physical examination. The abnormal test result prompted further assessment in 47 patients. No surgical procedure was delayed, and no association was noted between adverse outcome and any preoperative laboratory abnormality. Because of our findings in this analysis and similar studies on specific tests from other institutions, we no longer require preoperative laboratory screening tests for healthy patients.

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.