Use of Intraoperative Ultrasonography during Hepatolithectomy

Abstract. Complete clearance of intrahepatic stones has long been a major surgical challenge. To reduce the incidence of residual stones, we used intraoperative ultrasonography (IOUS) to localize them and guide lithectomy in 38 patients with hepatolithiasis between July 1988 and December 1993. All patients had multiple intrahepatic stones; 24 had accompanying extrahepatic calculi. Hepatic stones were confined to the left intrahepatic biliary tract in 13 patients, to the right in 9, and in both lobes in 16. Twenty-three patients underwent common bile duct exploration followed by T-tube drainage, 8 had transhepatic lithotomy with or without choledocholithotomy, 3 had choledocolithotomy and Roux-en-Y side-to-side choledochojejunostomy, and 2 had hepaticojejunostomy, left lobectomy was performed in the remainder. In 35 patients cholecystectomy was performed at the same time. Complete clearance of the stones was achieved in 36 patients (94.7%). The incidence of retained stone was decreased to 5.3%. No associated complications occurred. IOUS can accurately localize intrahepatic calculi, directly orient lithotomy instruments to approach the stones, demonstrate the spatial relation between stone and intrahepatic critical structure, and thereby choose an optical route for transhepatic lithotomy. Imaging can be repeated at any time with no radiation exposure to the patient or the medical staff.     

Scopolamine Prevents Dreams during General Anesthesia

Background: Dreaming during anesthesia is not a well-understood phenomenon. Anticholinergic drugs are used in anesthesia as premedication, but their use to decrease the incidence of dreams and psychological adverse reactions after anesthesia is not well established. The authors therefore studied the efficacy of intramuscular atropine and scopolamine for the prevention of dreams during general anesthesia with propofol and nitrous oxide.

Methods: Healthy women undergoing minor gynecologic surgery were randomly assigned to receive 2.5 [mu]g/kg scopolamine or 10 [mu]g/kg atropine intramuscularly (n = 50/group). In both groups, anesthesia was induced and maintained with propofol as a 2.5-mg/kg bolus, followed by 12 mg [middle dot] kg-1 [middle dot] h-1 as a continuous infusion and 70% nitrous oxide in oxygen. Two interviews regarding dreaming activity and characteristics were conducted at 20 min and 6 h after surgery.

Results: None of the patients in the scopolamine group and 47% of the patients in the atropine group reported the occurrence of dreams 20 min after recovery. The results were similar at 6 h: 6% of the scopolamine group and 43% of the atropine group reported dream activity. No differences in sedation or anesthetic requirements were found.     

Intraoperative Fluids and Fluid Management for Ambulatory Dental Sedation and General Anesthesia

Intravenous fluids are administered in virtually every parenteral sedation and general anesthetic. The purpose of this article is to review the physiology of body-water distribution and fluid dynamics at the vascular endothelium, evaluation of fluid status, calculation of fluid requirements, and the clinical rationale for the use of various crystalloid and colloid solutions. In the setting of elective dental outpatient procedures with minor blood loss, isotonic balanced crystalloid solutions are the fluids of choice. Colloids, on the other hand, have no use in outpatient sedation or general anesthesia for dental or minor oral surgery procedures but may have several desirable properties in long and invasive maxillofacial surgical procedures where advanced hemodynamic monitoring may assess the adequacy of intravascular volume.Key Words: Intravenous fluids, Ambulatory, Sedation, General anesthesia, Dentistry, Crystalloids, ColloidsIntravenous fluids are administered in almost every parenteral sedation and general anesthetic.¹ Historically, sedative medications were administered using a variety of methods that included barbotage, intramuscular injection, or inhalation of volatile agents. The goal of intravenous fluid therapy in anesthetic practice is to maintain adequate tissue perfusion and oxygen delivery,^1–3 and, in most cases, provide a fluid vehicle for drug administration. Decisions regarding the type and amount of fluids administered intraoperatively may affect postoperative outcomes.¹ This article reviews the physiology of body-water distribution and fluid dynamics at the vascular endothelium, evaluation of volume status, calculation of fluid requirements, and the clinical rationale for the use of various crystalloid and colloid solutions.     

Optimal Oxygen Concentration during Induction of General Anesthesia

Background: The use of 100% oxygen during induction of anesthesia may produce atelectasis. The authors investigated how different oxygen concentrations affect the formation of atelectasis and the fall in arterial oxygen saturation during apnea.

Methods: Thirty-six healthy, nonsmoking women were randomized to breathe 100, 80, or 60% oxygen for 5 min during the induction of general anesthesia. Ventilation was then withheld until the oxygen saturation, assessed by pulse oximetry, decreased to 90%. Atelectasis formation was studied with computed tomography.

Results: Atelectasis in a transverse scan near the diaphragm after induction of anesthesia and apnea was 9.8 +/- 5.2 cm2 (5.6 +/- 3.4% of the total lung area; mean +/- SD), 1.3 +/- 1.2 cm2 (0.6 +/- 0.7%), and 0.3 +/- 0.3 cm2 (0.2 +/- 0.2%) in the groups breathing 100, 80, and 60% oxygen, respectively (P < 0.01). The corresponding times to reach 90% oxygen saturation were 411 +/- 84, 303 +/- 59, and 213 +/- 69 s, respectively (P < 0.01).     

Transcranial Doppler Intraoperative Monitoring during Carotid Endarterectomy: Experience with Regional or General Anesthesia,with and without Shunting

p = 0.05). There was no significant difference when particulate and air microemboli were compared. During surgery TCD identified residual flow of less than 40% in the MCA in 17 patients (18.8%). TCD also identified hyperperfusion in two patients, shunt abnormalities in three patients, and influenced postop treatment in four patients, one of whom was returned to surgery. TCD is an important tool for identifying patients who would benefit from a shunt, preventing hyperperfusion, identifying postop emboli, and detecting technical errors.     

Intraoperative Modulation of Alveolar Macrophage Function during Isoflurane and Propofol Anesthesia

Background: Alveolar macrophages are a critical part of the defense against pulmonary infection. Thus the authors determined time-dependent changes in alveolar macrophage functions in patients having surgery who were anesthetized with isoflurane or propofol.

Methods: Patients anesthetized with propofol (n = 30) or isoflurane (n = 30) during orthopedic surgery were studied. Alveolar macrophages were harvested by bronchoalveolar lavage immediately, and 2, 4, and 6 h after induction anesthesia and at the end of surgery. The fraction of aggregated and nonviable macrophages was determined. Then phagocytosis was measured by ingestion of opsonized and unopsonized particles. Finally, microbicidal activity was determined as the ability of the macrophages to kill Listeria monocytogenes directly.

Results: Demographic and morphometric characteristics of the patients given propofol and isoflurane were similar, as were their levels of pulmonary function and hemodynamic responses. The fraction of alveolar macrophages ingesting opsonized and unopsonized particles, and the number of particles ingested, decreased significantly over time, with the decrease slightly but significantly greater during isoflurane anesthesia. Microbicidal function decreased progressively during anesthesia and surgery, with the decrease almost twice as great during isoflurane compared with propofol anesthesia. The fraction of aggregated macrophages and recovered neutrophils increased over time in the patients given each anesthetic.     

BIS Monitoring to Prevent Awareness during General Anesthesia

Background: Unexpected awareness is a rare but well-described complication of general anesthesia that has received increased scientific and media attention in the past few years. Transformed electroencephalogram monitors, such as the Bispectral Index monitor, have been advocated as tools to prevent unexpected recall.

Methods: The authors conducted a power analysis to estimate how many patients would be needed in an appropriately powered study to demonstrate the Bispectral Index monitor reduces awareness, as well as a cost analysis to assess the cost of using the monitor for this purpose alone.

Results: If unexpected recall is rare (1 in 20,000), it will require a large study to demonstrate that the monitor reduces awareness (200,000-800,000 patients), and the cost of using it for this purpose alone would be high ($400,000 per case prevented). If awareness is common (1 in 100), then the number of patients needed in a study to demonstrate that the monitor works becomes tractable (1,000-4,000 patients), and the cost of using the monitor for this purpose alone becomes lower ($2,000 per case prevented). Because there are reported cases of awareness despite Bispectral Index monitoring, the authors are certain that the effectiveness of the monitor is less than 100%. As the performance of the monitor decreases from 100%, the size of the study needed to demonstrate that it works increases, as does the cost of using it to prevent awareness.     

Heat Flow and Distribution during Induction of General Anesthesia

Background: Core hypothermia after induction of general anesthesia results from an internal core-to-peripheral redistribution of body heat and a net loss of heat to the environment. However, the relative contributions of each mechanism remain unknown. The authors evaluated regional body heat content and the extent to which core hypothermia after induction of anesthesia resulted from altered heat balance and internal heat redistribution.

Methods: Six minimally clothed male volunteers in an [nearly equal] 22 degrees Celsius environment were evaluated for 2.5 control hours before induction of general anesthesia and for 3 subsequent hours. Overall heat balance was determined from the difference between cutaneous heat loss (thermal flux transducers) and metabolic heat production (oxygen consumption). Arm and leg tissue heat contents were determined from 19 intramuscular needle thermocouples, 10 skin temperatures, and "deep" foot temperature. To separate the effects of redistribution and net heat loss, we multiplied the change in overall heat balance by body weight and the specific heat of humans. The resulting change in mean body temperature was subtracted from the change in distal esophageal (core) temperature, leaving the core hypothermia specifically resulting from redistribution.

Results: Core temperature was nearly constant during the control period but decreased 1.6 plus/minus 0.3 degrees Celsius in the first hour of anesthesia. Redistribution contributed 81% to this initial decrease and required transfer of 46 kcal from the trunk to the extremities. During the subsequent 2 h of anesthesia, core temperature decreased an additional 1.1 plus/minus 0.3 degrees Celsius, with redistribution contributing only 43%. Thus, only 17 kcal was redistributed during the second and third hours of anesthesia. Redistribution therefore contributed 65% to the entire 2.8 plus/minus 0.5 degrees Celsius decrease in core temperature during the 3 h of anesthesia. Proximal extremity heat content decreased slightly after induction of anesthesia, but distal heat content increased markedly. The distal extremities thus contributed most to core cooling. Although the arms constituted only a fifth of extremity mass, redistribution increased arm heat content nearly as much as leg heat content. Distal extremity heat content increased [nearly equal] 40 kcal during the first hour of anesthesia and remained elevated for the duration of the study.