John H. Tinker

Role of monitoring devices in prevention of anesthetic mishaps: a closed claims analysis.

Anesthesiologist-reviewers examined 1,175 anesthetic-related closed malpractice claims from 17 professional liability insurance companies. The claims were filed between 1974 and 1988. The reviewers were asked to determine if the negative outcome was preventable by proper use of additional monitoring devices available at the time of the review even if not available at the time the incident occurred, and if so, which devices could have been preventative. In 1,097 cases sufficient information was available to make a judgment regarding preventability of the morbidity or mortality by application of additional monitoring devices. It was determined that 31.5% of the negative outcomes could have been prevented by application of additional monitors. Using the insurance industrys scale of 0 (no injury) to 9 (death), the median severity of injury for incidents deemed preventable was 9 compared with 5 for those deemed not preventable (P less than 0.01, scale detailed in text). The severity of injury scores were the same for preventable mishaps occurring during regional or general anesthesia, suggesting that additional monitoring devices may be equally efficacious in preventing serious negative outcomes during either regional or general anesthesia. The judgements or settlements of the incidents judged preventable by additional monitoring were 11 times more costly (P less than 0.01) than those mishaps not judged preventable. The monitors determined by the reviewers to be most useful in mishap prevention were pulse oximetry plus capnometry. Applied together, these two technologies were considered potentially preventative in 93% of the preventable mishaps.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of strategies to decrease postanesthesia care unit costs

Background: The goal of this study was to identify interventions that anesthesiologists can make to decrease total costs of a postanesthesia care unit (PACU). Methods: Data were collected retrospectively from patients who underwent ambulatory surgery at our tertiary care center. Results: Supplies and medications accounted for only 2% of PACU charges. Personnel costs, which depend on the peak number of patients in the PACU, accounted for almost all PACU costs. If nausea and vomiting could have been eliminated in each patient who suffered this complication, without causing sedation, the total time to discharge for all patients would have been decreased by less than 4.8% (95% confidence interval <7.3%). Arrival rates to and times to discharge from the PACU followed triangular and log-normal distributions, respectively. Computer simulations, using published times to discharge for drugs with «faster recovery,» such as propofol, showed that the use of these drugs would only decrease PACU costs if operating rooms were consistently scheduled to run later each day. Such earlier discharge also might be beneficial if used at night, but only if the PACU could close after a single patient leaves. However, reasonably achievable decreases in the times to discharge for all patients undergoing general anesthesia are unlikely to substantively decrease PACU costs. In contrast, arranging an operating room schedule to optimize admission rates would greatly affect the number of PACU nurses needed. Conclusions: Anestheslologists have little control over PACU economics via choice of anesthetic drugs. The major determinant of PACU costs is the distribution of admissions

Decreases in anesthesia-controlled time cannot permit one additional surgical operation to be reliably scheduled during the workday.

We tested whether anesthesiologists can decrease operating room (OR) costs by working more quickly.Anesthesia-controlled time (ACT) was defined as the sum of 1) the time starting when the patient enters an OR until preparation or surgical positioning can begin plus 2) the time starting when the dressing is finished and ending when the patient leaves the OR. Case time was defined as the time starting when one patient undergoing an operation leaves an OR and ending when the next patient undergoing the same operation leaves the OR. An actual case series was constructed of 709 consecutive patients who underwent one of 11 elective operations at a tertiary care center. Statistical analysis of measured OR times showed that ACT would have to be decreased by more than 100% to permit one additional scheduled, short (30-min) operation to be performed in an OR during an 8-h workday after a prior series of cases, each lasting more than 45 min. Anesthesiologists alone cannot reasonably decrease case times sufficiently to permit one extra case to be reliably scheduled during a workday. Methods to decrease ACT (e.g., using preoperative intravenous catheter teams, procedure rooms, and/or shorter acting drugs) may simply increase costs. (Anesth Analg 1995;81:1263-8)

Coagulation changes during packed red cell replacement of major blood loss

A greater proportion of blood replacement needs are being met by packed red cell concentrates rather than whole blood in situations of major blood loss. Twelve patients, who required major blood replacement during elective surgery, were studied to determine the changes in coagulation when packed red cells were used to replace major blood loss. In addition, the coagulation abnormalities present at the time an observer noted excessive bleeding were determined. Prior to blood product replacement and after the estimated loss of each 0.3 blood volume, coagulation tests were obtained including prothrombin time (PT), partial thromboplastin time (aPTT), platelet count, thrombin time (TT), fibrinogen levels, and assays of coagu. lation Factors V, VIII, and IX. Coagulation tests were repeated when clinical hemostasis was judged inadequate by the anesthesiologist and attending surgeon. Significant decreases in platelet count, fibrinogen levels, and Factor V, VIII, and IX levels occurred as increasing blood volumes were replaced. Increases in PT and aPTT above control occurred in nine of the 12 patients prior to replacement of 1 blood volume; none of the nine patients had increased clinical bleeding. In four of seven patients who had blood replacement of greater than 1 blood volume, increased clinical bleeding was noted by the observer. Platelet counts were less than 100,00O/mm3 in each of these four patients, and a platelet concentrate obtained by pheresis of a single donor was administered. In two of the four patients platelet counts increased, but clinical bleeding did not resolve. Freshfrozen plasma (FFP) in addition to the platelet concentrate was used in these two patients. In both patients fibrinogen levels were less than 75 mg/dl, and the PT and aPTT were 1.5 times control values prior to FFP. If prolongation of PT and PTT had been used as the indication for administration of FFP, nine of the 12 patients would have unnecessarily received FFP prior to the loss of 1 blood volume. In situations when packed red cells are used for major blood replacement, clotting factors in the form of FFP may not be necessary to maintain the PT or PTT at accepted normal levels.

Anterior Shift of the Dominant Eeg Rhythm during Anesthesia in the Java Monkey: Correlation with Anesthetic Potency

EEG amplitude dominance in awake man is posterior. During EEG monitoring in patients, the authors observed the abrupt appearance of anterior amplitude dominance during induction of anesthesia with halothane, enflurane, or thiopental. This EEG change is coincident with loss of eyelid reflex and loss of ability to respond to command. This EEG change was studied with several anesthetics in five Java monkeys to determine alveolar anesthetic concentration at which it occurred and to observe the effects of various stimuli on it. EEG recordings were obtained after equilibration at each level with increasing concentrations of halothane, enflurane or isoflurane in oxygen and each agent again in 30 per cent N2O, in separate experiments in the same animals. EEG amplitude dominance became anterior in each animal with each anesthetic and combination at concentrations less than MAC, which was also determined in the same experiments. At lower concentrations, stimulation at equilibrated anesthetic concentrations resulted in abrupt EEG return to posterior amplitude dominance. The end-tidal anesthetic concentration at which persistence of anterior EEG dominance was seen after stimulation was approximately 0.4 MAC for each anesthetic and combination tested. This is interpreted as support for physical solution-lipid solubility theories of anesthetic action. In addition, an EEG change common to various anesthetics may increase the clinical usefulness of EEG monitoring. It is speculated that this EEG change may signal loss of awareness. If so, observance of sustained anterior EEG amplitude dominance may provide assurance of obliteration of awareness during anesthesia.

The nonlinear responses of cerebral metabolism to low concentrations of halothane, enflurane, isoflurane, and thiopental.

The relationship between cerebral oxygen consumption (CMRO2) and anesthetic concentration has been assumed (based upon isolated measurements) to be approximately linear at concentrations less than 1 MAC. The shapes of the anesthetic dose-response curves for both CMRO2 and cerebral blood flow (CBF) were examined by multiple measurements made at small, progressive concentration increments from 0 to 2 MAC halothane (six dogs), enflurane (six dogs), and isoflurane (six dogs), and during a constant 23 mg/kg/hr infusion of thiopental (six dogs). The EEG was continuously recorded and changes in EEG patterns from “awake” to “anesthetic” were correlated with changes in anesthetic concentration, CBF, and CMRO2. The significance of changes in the slopes of regression lines for CMRO2, before, during and after changes in EEG patterns from “awake” “anesthetic” were then determined. Contrary to previous inferences, CMRO2, dose–response curves were found to be nonlinear at anesthetic concentrations less than 1 MAC for all anesthetics studied. CMRO2, decreased precipitously until a stable “anesthetic” pattern was observed on the EEG; thereafter, CMRO2, decreased at a markedly reduced rate. The onset of this change occurred at concentrations well below MAC for the inhalational anesthetics. With the thiopental infusion, CMRO2 decreased most rapidly during the first 25 minutes. With halothane and enflurane, CBF was maximal during the period of transition in the EEG from an “awake” to an “anesthetic” pattern. CBF was elevated at all concentrations of isoflurane studied. CBF decreased rapidly during thiopental infusion until the EEG pattern changed from “awake” to “anesthetic” and then more slowly. The results demonstrate that the change in the EEG to an “anesthetic” pattern, which occurs at concentrations well below MAC, is accompanied by an abrupt metabolic depression. It is speculated that these events coincide with the onset of functional depression.

A cost/benefit analysis of randomized invasive monitoring for patients undergoing cardiac surgery

The aim of this study was to determine the effect of choice of invasive monitoring on cost, morbidity, and mortality in cardiac surgery. Two hundred and twenty-six adults undergoing elective cardiac surgery were initially assigned at random to receive either a central venous pressure monitoring catheter (group I), a conventional pulmonary artery (PA) catheter (group II), or a mixed venous oxygen saturation (S&OV0540;O2) measuring PA catheter (group III). If the attending anesthesiologist believed that the patient initially randomized to group I should have a PA catheter, that patient was then reassigned to receive either a conventional PA catheter (group IV) or S&OV0540;O2 measuring PA catheter (group V). The total costs were defined as the total amount billed to the patient for the catheter used; the professional cost of its insertion; and the determinations of cardiac output, arterial blood gas tensions, hemoglobin level, and hematocrit. Mean total monitoring and laboratory costs in Group I (

Myocardial reinfarction following local anesthesia for ophthalmic surgery

591 ± 67) were statistically significantly (P < 0.05) less than costs in Group II (

Hypothermia after cardiopulmonary bypass in man: amelioration by nitroprusside-induced vasodilation during rewarming.

856 ± 231). Further, mean monitoring and laboratory costs in Group II were statistically significantly (P < 0.05) less than those in Group III (

Halothane relaxes previously constricted isolated porcine coronary artery segments more than isoflurane.

1128 ± 759). Patients in group IV incurred mean total costs of