Development and evaluation of a score to predict difficult epidural placement during labor.

BACKGROUND AND OBJECTIVES: Difficult epidural placement (DEP) during labor may be distressing for the patient and may increase the risk of dural puncture. A score predicting DEP based on the combination of individual risk factors could identify high-risk patients. This study aimed to identify risk factors for DEP and build a prediction score. METHODS: Three hundred thirty patients were prospectively included. Difficult epidural placement was defined as more than 1 skin puncture with a Tuohy needle. Dura puncture occurrence was recorded. The population was randomly split into a training set and a validation set. In the training set, risk factors were identified with logistic regression and used to build a score defining 3 risk groups. Model and score discrimination was assessed with the C-index and clinical usefulness of the score with decision curves. RESULTS: Difficult epidural placement frequency was 30% (95% confidence interval [95% CI], 25%-35%). Dural puncture was more frequent in DEP patients (4% vs 0%, P = 0.007). Three independent risk factors for DEP were identified: difficult interspinous space palpation (odds ratio [OR], 6.1; 95% CI, 2.8-13.9), spinal deformity (OR, 2.4; 95% CI, 1.1-5.3), and inability to flex the back (OR, 3.0; 95% CI, 1.2-7.8). The C-index of the model was 0.81 (95% CI, 0.74-0.88) in the training set and 0.78 (95% CI, 0.70-0.86) in the validation set. A 5-point score was created to define groups with low risk (score 0), intermediate risk (score 1-2), and high risk (score 3-4), with predicted rates of DEP of 9.7%, 30.3%, and 68.9%, respectively. The C-index of the score was 0.79 (95% CI, 0.72-0.86) in the training set and 0.76 (95% CI, 0.69-0.84) in the validation set. Decision curves support the clinical usefulness of the score. CONCLUSIONS: This study confirms risk factors for DEP and proposes a score to predict DEP. The score identifies high-risk patients who may benefit from an intervention to decrease DEP. This hypothesis should be evaluated in an impact study.

The effect of preoperative heart rate and anxiety on the propofol dose required for loss of consciousness.

BACKGROUND: Conflicting results have been reported on the effect of anxiety on the propofol dose required for inducing loss of consciousness (LOC). The hemodynamic effects of anxiety, increased heart rate (HR), and cardiac output may account for these discrepancies. We therefore designed this study to address, first, the effect of perioperative HR on propofol dose required for LOC and, second, the effect of perioperative anxiety on HR. METHODS: Forty-five ASA physical status I-II female patients undergoing gynecological surgery were studied. Anxiety was assessed in the operating room with the State-Trait Anxiety Inventory (STAI)-state Spielberger scale (situational anxiety). After HR recording, anesthesia was induced with a 200-mL/h 1% propofol infusion with the Base Primea pump (Fresenius-Vial, Brezins, France) until LOC. The propofol dose was recorded at the time of LOC. Relationships between STAI-state and HR versus propofol dose at LOC were tested with the Spearman test with a P value of 0.01. RESULTS: A significant relationship was observed between HR and propofol dose at LOC (rho = 0.487, P = 0.0012) but not between STAI-state and propofol dose (rho = 0.330, P = 0.0306). However, a significant relationship was observed between STAI-state and HR (rho = 0.462 and P = 0.0054). CONCLUSION: Increased perioperative HR is associated with increased propofol dose required for LOC. Perioperative anxiety accounts for increased HR.

Predicted propofol effect-site concentration for induction and emergence of anesthesia during early pregnancy.

BACKGROUND: Pregnancy is associated with decreased hypnotic requirement, allegedly related to progesterone. However, the effects of pregnancy and progesterone on propofol requirement have not been thoroughly investigated. We conducted this study to determine whether propofol dose and predicted effect-site concentration for loss of consciousness (LOC) during induction of anesthesia, and eye opening during emergence from anesthesia, are decreased during early pregnancy. We also investigated whether blood progesterone was correlated with propofol dose and effect-site concentration for LOC. METHODS: We studied 57 ASA I-II women patients undergoing elective termination of pregnancy and 55 control patients undergoing transvaginal oocyte puncture for in vitro fertilization. Anesthesia was induced by administration of a 1% propofol infusion at 200 mL/min. Propofol dose and calculated effect-site concentration (Schnider model) were recorded at the time of LOC during induction. We also calculated effect-site concentration at the time of eye opening upon emergence from anesthesia. Blood progesterone was measured after surgery. RESULTS: Mean (+/-1 SD) propofol dose at LOC was significantly reduced in the pregnant patients compared with the nonpregnant control patients (108.57 +/- 20.04 vs 117.59 +/- 17.98 mg, respectively; P = 0.014). Similarly, the calculated propofol effect-site concentration at LOC was significantly lower in the pregnant patients than the nonpregnant control patients (4.59 +/- 0.72 vs 5.01 +/- 0.64 microg/mL, respectively; P = 0.0014). There was no difference in the calculated effect-site concentration on eye opening upon emergence. No significant relationship was observed between blood progesterone and propofol dose or calculated propofol effect-site concentration at LOC. CONCLUSION: Propofol dose and predicted propofol effect-site concentration at LOC are decreased during early pregnancy. Progesterone does not explain this result.