Preoperative measurement of maternal abdominal circumference relates the initial sensory block level of spinal anesthesia for cesarean section: An observational study.

OBJECTIVE: Lumbosacral cerebrospinal fluid volume is decreased as the enlarging uterus compresses the inferior vena cava during pregnancy. A subsequent greater cephalad spread of sensory blockade is observed. Gravid uterus plays a crucial role in affecting the spinal anesthesia level. We hypothesized that maternal abdominal circumference can reflect compressive effect of the uterus and investigated the relationship between abdominal circumference and the level of sensory blockade, and incidence of hypotension following spinal anesthesia with hyperbaric bupivacaine in term parturients. MATERIALS AND METHODS: Forty-two term parturients scheduled for elective cesarean section were studied. Abdominal circumference was measured before spinal anesthesia; 0.5% hyperbaric bupivacaine (2 mL, 2.2 mL, or 2.4 mL) was injected in to the subarachnoid space at the L3-L4 intervertebral level according to the parturient's height. The level of sensory blockade was assessed using an ice cube 1 minute, 5 minutes, 10 minutes, and 15 minutes after the spinal injection. The level of sensory blockade at the 15th minute was defined as the level of maximum sensory blockade. Statistical correlation coefficients were evaluated with Spearman's rank correlation. RESULTS: The correlation coefficient between the abdominal circumference and spinal level measured by cold sensation loss at 5 minutes after spinal anesthesia was significantly positive (right side ρ=0.43, p=0.005; left side ρ=0.46, p=0.003). No significant correlation was found between abdominal circumference and the level of maximum sensory blockade, the incidence of hypotension, ephedrine dosage, nausea, and vomiting after spinal anesthesia. CONCLUSION: Parturients with greater abdominal circumference value have a higher level of sensory blockade at 5 minutes after spinal anesthesia. Abdominal circumference cannot predict the maximum sensory blockade level and the incidence of hypotension.

Cardiovascular collapse after labetalol for hypertensive crisis in an undiagnosed pheochromocytoma during cesarean section.

Pheochromocytoma is a catecholamine-producing tumor but rarely delayingly diagnosed until during pregnancy. We reported a pregnant woman who underwent emergent cesarean section because of intrauterine growth retardation, oligohydramnios, and hypertension. The existence of an undiagnosed pheochromocytoma was suspected by the unusual hemodynamic response to spinal anesthesia, abdominal compressions, and operative stimulus. Hypertensive crisis occurred during the operation and she was sent to the intensive care unit for postoperative care. In the intensive care unit, cardiovascular collapse occurred after nonselective ß-adrenergic blockade. Unexpected hypertensive crisis during the perioperative period should alert clinicians to the possibility of a pheochromocytoma. For the treatment of choice, nonselective ß-adrenergic blockade should not be used before the α-blockade.

Premedication with mirtazapine reduces preoperative anxiety and postoperative nausea and vomiting.

BACKGROUND: Mirtazapine is a new antidepressant that blocks 5-HT2 and 5-HT3 receptors. With this receptor profile, it is possible that mirtazapine could provide both anxiolysis and efficacy for postoperative nausea and vomiting (PONV). We therefore tested the hypothesis that premedication with mirtazapine can reduce preoperative anxiety and PONV. METHODS: Eighty female patients with at least two PONV risk factors scheduled for gynecological surgery were enrolled. Dexamethasone 8 mg was given before induction of anesthesia and patients were randomly assigned to group M + D (mirtazapine plus dexamethasone) or group dexamethasone. An oral disintegrating mirtazapine 30 mg or placebo tablet was given 1 h before surgery. Preoperative anxiety level was assessed by a visual analog scale (VAS) before mirtazapine administration and 1 h thereafter. General anesthesia was induced with 1% propofol at the rate of 200 mL/h (until loss of consciousness) and was then maintained with sevoflurane in oxygen and air. An auditory evoked potentials index monitor was used to titrate sevoflurane. The incidence of PONV, the use of rescue antiemetic, complete response, postoperative Ramsay Sedation Scores, and VAS pain scores were assessed 1, 2, and 24 h after surgery and compared. RESULTS: The VAS anxiety scale was lower in group M + D after mirtazapine administration. There were no differences in the induction dose of propofol, the concentrations of sevoflurane during anesthesia, and recovery times between the two groups. The incidence of complete response to PONV over 0-24 h was lower in group M + D (80% vs 50%, P < 0.01). CONCLUSIONS: Premedication with mirtazapine 30 mg reduces the level of preoperative anxiety and the risk of PONV in moderate and high-risk female patients.

Simulation analysis of the performance of target-controlled infusion of propofol in Chinese patients.

BACKGROUND: The performance of target-controlled infusion (TCI) devices is important for the safety of patients. This study examined the performance of two propofol pharmacokinetic parameter sets in Chinese patients by computer simulation. METHODS: Two sets of propofol pharmacokinetic parameters respectively derived from Marsh's and Schnider's studies were compared with those obtained in Chinese subjects from Li's study. Pharmacokinetic parameters of propofol from Li's study for subjects of three different entities (average adult, obese adult, and elderly) were used to estimate the performance of Marsh's and Schnider's models. Sixty virtual patients were generated with Li's parameters. A computer program, STANPUMP, was used to perform the pharmacokinetic simulation. An induction dose of propofol at 2 mg/kg for average or obese adult, while 1.5 mg/kg for the elderly, followed by TCI of 4 microg/mL (average and obese adult) or 3 microg/mL (elderly) were simulated. The infusion schemes generated by STANPUMP using Marsh's or Schnider's model were put in to simulate the predicted plasma concentration based on the pharmacokinetic parameters from Li's study. The median performance error (MDPE) and absolute median performance error (MDAPE) were calculated to estimate the bias and inaccuracy. Differences between models were calculated using the paired t test. A P value < 0.05 was considered statistically significant. RESULTS: The bias and inaccuracy by Marsh's model in average adults were -11.9% and 18.5% respectively and by Schnider's model were -8.6% and 17.9%. For obese adults, the bias and inaccuracy were 6.3% and 26.2% respectively for Marsh's model and -6.6% and 22.6% for Schnider's model. Sohnider's model resulted in a significantly greater inaccuracy than Marsh's model (42.1% versus 15.5%) when applied to elderly patients. CONCLUSIONS: The performance of TCI infusion of propofol in Chinese patients is generally acceptable with Marsh's or Schnider's model apart from using Schnider's model in Chinese elderly patients. Further study to investigate the difference of propofol pharmacokinetics between Chinese and non-Chinese elderly patients is necessary.

Postoperative delayed respiratory failure caused by Guillain-Barré syndrome--a case report.

Postoperative respiratory failure caused by Guillain-Barré syndrome (GBS) is a rare complication after general anesthesia. We report a GBS patient who after receiving an operation for polycystic liver disease under general anesthesia developed weakness of upper and lower extremities on the 3rd postoperative day, with decreased deep tendon reflex, which ultimately evolved into respiratory failure. Slurred speech and bilateral ptosis were also noted. All these manifested an acute peripheral polyneuropathy combined with bulbar involvement. According to the clinical picture, CSF examination and results of nerve conduction tests, Guillain-Barré syndrome was diagnosed. Plasmapheresis was immediately arranged and her motor weakness problem was soon improved after treatment. No neurological sequelae were found two months after discharge. Postoperative muscle weakness is usually caused by residual effects of anesthetic agents or surgical complications. But it may sometimes be related to some rare neurological diseases. To prompt an accurate diagnosis of Guillain-Barré syndrome is important because it can help forestall fatal complications. In addition, the prognosis will be encouraging with early treatment.

Predicting blood pressure change caused by rapid injection of propofol during anesthesia induction with a logistic regression model.

BACKGROUND: Propofol is a common intravenous agent for induction and maintenance of anesthesia. The advantage of propofol is rapid recovery of consciousness when the continuous infusion is stopped. Additionally, it has antiemetic effect of reducing postoperative nausea and vomiting. On the other hand, rapid infusion of propofol is painful and may cause hypotension. In this study, we aimed to develop a logistic regression model to accurately predict blood pressure change caused by rapid infusion of propofol. METHODS: Seventeen variables (including demographic data, past medical history, laboratory data, and blood pressure before induction) were assessed in 200 patients who received propofol for induction of anesthesia for routine surgery. A logistic regression model was derived using these values as independent variables to predict whether a patient would suffer a significant blood pressure change (> 30% decrease from baseline). Sensitivity, specificity, and area under the receiver operating characteristic curve (AUC) were calculated to evaluate the performance of our prediction model. RESULTS: A cut-off value of 0.17 in the logistic regression model predicted decreased blood pressure with 90.0% sensitivity and, 67.3% specificity. The area under the receiver operating characteristic curve was 0.855. CONCLUSIONS: Our prediction model predicts propofol-induced hypotension with acceptable accuracy. Because of the straightforward mathematic formula used, our model can be integrated effortlessly into a hospital information system, providing a reliable and useful decision support for clinical anesthesia staff.