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C C Apfel

Publications and source records attributed to C C Apfel.

32 records · Page 2Linked to original sources
PubMed2001

What can be expected from risk scores for predicting postoperative nausea and vomiting?

Several risk scores have been developed to calculate the probability of postoperative nausea and vomiting (PONV). However, the power to discriminate which individual will suffer from PONV is still limited. Thus, we wondered how the number of predictors in a score affects the discriminating power and how the characteristics of a population--which is needed to measure the power of a score--may affect the results. For ethical reasons and to be independent from centre specific populations, we developed a computer model to simulate virtual populations. Four populations were created according to number, frequency, and odds ratio of predictors. Population I: parameters were derived from a previously published paper to verify whether calculated and reported values are in accordance. Population II: a gynaecological population was created to investigate the impact of the study setting. Populations III and IV: to meet ideal assumptions a model with up to seven predictors with an odds ratio of 2 and 3 was tested, respectively. The discriminating power of a risk score was measured by the area under a receiver operating characteristic curve (AUC) and an increase of more than 0.025 per predictor was considered to be clinically relevant. The AUC of population I was similar to those reported in clinical investigations (0.72). The study setting had a considerable impact on the discriminating power since the AUC decreased to 0.65 in a gynaecological setting. The AUC with the 'idealized' populations III and IV was at best in the range of 0.7-0.8. The inclusion of more than five predictors did not lead to a clinically relevant improvement. The currently available simplified risk scores (with four or five predictors) are useful both as a method to estimate individual risk of PONV and as a method for comparing groups of patients for antiemetic trials. They are also superior to single predictor models which are just using the patients' history of PONV or female gender alone. However, our analysis suggests that the power to discriminate which indvidual will suffer from PONV will remain imperfect, even when more predictors are considered.

Area Under Curve↗
PubMed2001

The detection of interatrial flow patency in awake and anesthetized patients: a comparative study using transnasal transesophageal echocardiography.

UNLABELLED: The Valsalva maneuver in the awake patient and the ventilation maneuver in the tracheally intubated anesthetized patient are two provocation methods to detect a patent foramen ovale (PFO) by means of contrast transesophageal echocardiography. In 60 patients undergoing posterior fossa surgery, a contrast agent was administered via a peripheral vein during a Valsalva maneuver immediately before anesthesia induction, followed by central venous administration during a ventilation maneuver in the same patients when anesthetized and endotracheally intubated. We evaluated both maneuvers with a 32-element monoplane transnasal transesophageal echocardiography probe to trace the atrial flow of the contrast agent in a 90 degrees bicaval view. A maneuver was rated positive when more than four bubbles appeared in the left atrium during the first three cardiac cycles after intrathoracic pressure release. The right atrial cross-sectional area before pressure release, and the peak septal excursion during atrial contrast opacification, were measured. McNemar's test was used to assess a paired dichotomous response on the two maneuvers for a significant difference. In 56 patients, the ventilation maneuver was significantly (P < 0.037) more often positive for PFO (n = 14) than the Valsalva maneuver (n = 7). Although there was no difference in the methods regarding the peak septal excursion, the mean right atrial area before pressure release was significantly smaller during the ventilation maneuver than during the Valsalva maneuver (11.2 +/- 3.1 cm(2) vs 14.4 +/- 3.3 cm(2), n = 42, P < 0.05). In the patients with a positive ventilation, but a negative Valsalva maneuver, the discrepancy was even larger (10.9 +/- 4.4 cm(2) vs 16.3 +/- 4.2 cm(2), n = 7, P < 0.001). We conclude that the ventilation maneuver is superior to the Valsalva maneuver in detecting PFO. Our data suggest that a peak pressure of 30 cm H(2)O during the ventilation maneuver achieves a more pronounced reduction in right atrial load and allows right atrial pressure to exceed left atrial pressure when intrathoracic pressure is released. IMPLICATIONS: A controlled ventilation maneuver in anesthetized patients immediately before posterior fossa surgery may be superior to the preoperative Valsalva maneuver in detecting a patent foramen ovale by contrast transesophageal echocardiography. This approach identifies patients at high risk for paradoxic embolism, but it is not practical for preoperative identification of patients who might benefit from patent foramen ovale closure before surgery.

Anesthesia↗
PubMed2000

[Risk factors for nausea and vomiting after general anesthesia: fictions and facts].

Numerous factors have been claimed to influence postoperative nausea and vomiting (PONV). A critical review of the literature reveals, that strong evidence based on original double-blind, randomized, controlled trials or their meta-analyses is only available for very few risk factors. For most other factors, although mentioned in narrative reviews, there is insufficient evidence. Sufficient evidence on original data or meta-analyses is present for female gender, a history of PONV or motion sickness, non-smoking-status, young age, volatile anaesthetics, nitrous oxide and postoperative opioids. Factors with conflicting results are the menstrual cycle, hypnotics for induction, mask ventilation and nasogastric tube, the experience of the anaesthetist, muscle relaxants and their antagonists and laparoscopic procedures. Insufficient evidence is present for the other types of operation, psychological factors including anxiety and pain. No evidence due to lack of data applies to postoperative movement, hemodynamic stability, hypercarbia and acid-base-shifts. For adipositas++ there is not only a lack of evidence for an effect but evidence for a lack of effect based on several multivariate analyses. In conclusion, we have developed the following simplified view: PONV is mainly caused by opioids and volatile anaesthetics when applied to susceptible patients (females, non-smoker, positive history of previous sickness).

Anesthesia, General↗
PubMed1999

A simplified risk score for predicting postoperative nausea and vomiting: conclusions from cross-validations between two centers.

BACKGROUND: Recently, two centers have independently developed a risk score for predicting postoperative nausea and vomiting (PONV). This study investigated (1) whether risk scores are valid across centers and (2) whether risk scores based on logistic regression coefficients can be simplified without loss of discriminating power. METHODS: Adult patients from two centers (Oulu, Finland: n = 520, and Wuerzburg, Germany: n = 2202) received inhalational anesthesia (without antiemetic prophylaxis) for various types of surgery. PONV was defined as nausea or vomiting within 24 h of surgery. Risk scores to estimate the probability of PONV were obtained by fitting logistic regression models. Simplified risk scores were constructed based on the number of risk factors that were found significant in the logistic regression analyses. Original and simplified scores were cross-validated. A combined data set was created to estimate a potential center effect and to construct a final risk score. The discriminating power of each score was assessed using the area under the receiver operating characteristic curves. RESULTS: Risk scores derived from one center were able to predict PONV from the other center (area under the curve = 0.65-0.75). Simplification did not essentially weaken the discriminating power (area under the curve = 0.63-0.73). No center effect could be detected in a combined data set (odds ratio = 1.06, 95% confidence interval = 0.71-1.59). The final score consisted of four predictors: female gender, history of motion sickness (MS) or PONV, nonsmoking, and the use of postoperative opioids. If none, one, two, three, or four of these risk factors were present, the incidences of PONV were 10%, 21%, 39%, 61% and 79%. CONCLUSIONS: The risk scores derived from one center proved valid in the other and could be simplified without significant loss of discriminating power. Therefore, it appears that this risk score has broad applicability in predicting PONV in adult patients undergoing inhalational anesthesia for various types of surgery. For patients with at least two out of these four identified predictors a prophylactic antiemetic strategy should be considered.

Adult↗
PubMed1998

[Postoperative vomiting. A score for prediction of vomiting risk following inhalation anesthesia].

UNLABELLED: Despite numerous factors are thought to affect postoperative vomiting (PV) recent studies demonstrated that the risk of PV can be predicted by considering just the most important ones. Therefore, the aim of this study was to present the clinically most relevant factors, a risk score based upon those factors and its clinical applicability for other types of surgery. METHODS: In a prospective study 2220 adult inpatients scheduled for elective surgery were monitored for PV after inhalational anaesthesia over 24 hours. None of the patients received prophylactic antiemetic treatment. Multivariate analyses were performed with data of patients who underwent otolaryngological procedures to identify the major risk factors and to derive a risk score. The applicability of the score in surgical and ophthalmological procedures was tested by linear regression analysis of expected and observed incidences. RESULTS: In the multivariate model, clinically most important risk factors for PV were female gender, young age, a positive history of postoperative nausea and vomiting or motion sickness, non-smoking and a long duration of anaesthesia, whereas the relative impact of the "type of operation itself" was small. Expected and observed incidences in patients undergoing other types of surgery were strongly correlated (R2 = 0.99, P < 0.001). CONCLUSION: The risk for PV after inhalational anaesthesia in adults can be predicted using a score which is based on individual risk factors and the duration of anaesthesia only.

Adolescent↗
PubMed1998

A risk score to predict the probability of postoperative vomiting in adults.

BACKGROUND: The aim of this study was to identify factors most relevant for postoperative vomiting (PV) and to develop a risk score to predict the probability of PV. METHODS: Adult inpatients scheduled for elective ear, nose and throat (ENT) surgery under general anaesthesia were offered to participate in a prospective study for PV over 24 h. No prophylactic antiemetics were used. The data of 1137 patients were randomized and split into an evaluation set (n=553) and a validation set (n=584). The evaluation set was subjected to logistic regression analysis to quantify the relative impact of anaesthetic, surgical and individual factors and to develop a risk score. The score was then tested by applying it to the validation set. The area under a receiver operation characteristic (ROC) curve was calculated and the predicted and actual incidences of patients were correlated. RESULTS: In the evaluation set, patient-related factors (female gender, young age, non-smoking, history of PV or motion sickness) and a high duration of anaesthesia were independent risk factors for PV. The probability of PV could be estimated from the equation: PV=1/(1+exp(-z)) where z=1.28 (gender)-0.029 (age)-0.74 x (smoking)+0.63 x (history of PV or motion sickness)+0.26 x (duration)-0.92. In the validation set this score achieved an area under the ROC-curve of 0.78 and the actual incidence correlated strongly with the predicted risks (R2=0.93, P<0.001). CONCLUSION: The data suggest that the probability of PV following ENT surgery under inhalational anaesthesia with low-dose opioids can be predicted by a score mainly based upon patient-related risk factors.

Adult↗
PubMed1998

The discriminating power of a risk score for postoperative vomiting in adults undergoing various types of surgery.

BACKGROUND: Recently, we have demonstrated that the probability of postoperative vomiting (PV) following ENT surgery with inhalational anaesthetics can be predicted using a risk score. This score is based on gender, age, smoking status, history of motion sickness or postoperative nausea and vomiting and the duration of anaesthesia. Therefore, it is of interest whether this score is also accurate in predicting PV in patients undergoing different types of surgery. METHODS: Inpatients scheduled for bone, vascular, general or eye surgery were included in a prospective survey for PV over 24 h. Data of 1091 patients were analyzed, of which 542 were used for the validation of the previously constructed risk score (Score I). The data of the remaining 549 patients were used to evaluate the risk factors that contribute to PV in this setting and to develop a new score (Score II). The discriminating power of both scores to predict PV was tested in the validation set (n=542) and compared by calculating the area under the receiver operating characteristic (ROC) curves. RESULTS: The area under the ROC curve of Score I was 0.77 (SD 0.024). Risk factors for PV in the evaluation set were female gender, young age, history of motion sickness or postoperative nausea and vomiting and the type of surgery. The area under the curve of Score II was 0.75 (SD 0.026) and was not significantly different from Score I (P=0.57). CONCLUSION: Score I was accurate in predicting PV in patients after most types of surgery with volatile anaesthetics, which suggests that this score might be useful for other centres as well.

Adult↗