The effect of intra-abdominal pressure on sensory block level of single-shot spinal anesthesia for cesarean section: an observational study.

BACKGROUND: Increased intra-abdominal pressure in pregnancy is thought to affect intrathecal drug spread. However this assumption remains largely untested. The aim of this prospective study was to evaluate the association between intra-abdominal pressure and maximum sensory block level in parturients receiving spinal anesthesia for cesarean section. METHODS: Parturients having elective cesarean section with single-shot spinal anesthesia using hyperbaric bupivacaine 12.5mg were included. Intra-abdominal pressure was measured via a bladder catheter after establishing a T4 sensory block and at the end of surgery in the supine position with 10° left lateral tilt. We recorded demographic data, descriptive characteristics of pregnancy, self-reported weight gain and weight of the newborn. As secondary outcomes, we evaluated onset of sensory block, maximum sensory block, motor block, number of hypotensive episodes, fluid and ephedrine requirements, time to first analgesic request, time to one-point recovery of motor block and side effects. RESULTS: The median value of the maximum sensory block level was T2 in 117 parturients. Median [interquartile range] pre-incision and postoperative intra-abdominal pressure were 13 [11-16] and 9 [6-10]mmHg respectively. No association was observed between maximum sensory block level and pre-incision intra-abdominal pressure (P=0.83). Weight was associated with pre-incision intra-abdominal pressure with an estimated odds ratio of 1.04 per kg (99.4% CI: 1.00-1.08). There was a moderate correlation between pre-incision and postoperative intra-abdominal pressure with a Spearman correlation coefficient of 0.67 (99.5% CI: 0.5-0.79). There was no association between pre-incision intra-abdominal pressure and secondary outcomes. CONCLUSIONS: In parturients, intra-abdominal pressure was not associated with spinal block spread, block onset time, recovery or side effects.

The effects of subfascial wound versus epidural levo-bupivacaine infusion on postoperative pain following hysterectomy.

BACKGROUND: Local analgesia through wound catheters is used as a part of multimodal analgesia. The efficacy of continuous subfascial wound infusion compared to epidural analgesia is unknown for abdominal hysterectomy and bilateral salpingo-oophorectomy (TAH-BSO) via Pfannenstiel incision. The aim of this study was to compare the aforementioned two methods in this type of surgery for postoperative morphine consumption, acute and persistent postsurgical pain. METHODS: Fifty patients enrolled in the study were randomly allocated to receive continuous 10 mL/h levobupivacaine either via subfascial (Group S) or epidural (Group E) catheter for 48 h postoperatively. In Group S 0.25% levobupivacaine was used for the first six hours and 0.125% thereafter, whereas Group E received 0.125% levobupivacaine throughout the study period. Cumulative morphine consumption, static and dynamic pain, gastrointestinal recovery, ambulation, patient satisfaction, hospital stay, as well as pain at 2nd and 6th months were evaluated. RESULTS: Group S was superior to Group E regarding cumulative morphine consumption (16.8±7.2 mg and 28.7±10.3 mg respectively, P<0.001; mean difference -11.9 with 95% CI of the difference -17.1 to -6.7) and pain relief. Patient satisfaction was higher in Group S compared to Group E (P=0.006). Less postoperative vomiting was observed in Group S. No difference was detected in length of hospital stay and persistent postsurgical pain incidence. CONCLUSION: Wound analgesia via subfascial catheter with continuous levobupivacaine infusion decreases postoperative morphine consumption and increases patient satisfaction compared to epidural analgesia with no difference in persistent postsurgical pain following TAH-BSO via Pfannenstiel incision.

Supplemental intravenous crystalloids for the prevention of postoperative nausea and vomiting: quantitative review.

Hypovolaemia after overnight fasting is believed to exacerbate postoperative nausea and vomiting (PONV). However, data on the efficacy of supplemental i.v. crystalloids for PONV prophylaxis are conflicting. We performed a literature search using CENTRAL, MEDLINE, EMBASE, CINAHL, and Web of Science. We included prospective randomized controlled trials that reported PONV event rates in patients receiving supplemental i.v. crystalloids or a conservative fluid regimen after elective surgery under general anaesthesia. Studies were evaluated with regard to random sequence generation, allocation concealment, blinding of participants, personnel, and outcome assessment, incomplete outcome data, and selective reporting. We identified 15 trials (n=787 crystalloids; n=783 conservative fluids). Compared with conservative fluids, i.v. crystalloids reduced the risk of early postoperative nausea (PON) (relative risk 0.73, 95% confidence interval 0.59-0.89; P=0.003), late PON (0.41, 0.22-0.76; P=0.004), and overall PON (0.66, 0.46-0.95; P=0.02). I.V. crystalloids did not reduce the risk of early postoperative vomiting (POV) (0.66, 0.37-1.16; P=0.16) or late POV (0.52, 0.25-1.11; P=0.09), but did reduce overall POV (0.48, 0.29-0.79; P=0.004). I.V. crystalloids did not reduce the risk of early PONV (0.74, 0.49-1.12; P=0.16), but did reduce the risk of late PONV (0.27, 0.13-0.54; P<0.001) and overall PONV (0.59, 0.42-0.84; P=0.003). I.V. crystalloids reduced the need for antiemetic rescue treatment (0.56, 0.45-0.68; P<0.001). In summary, supplemental i.v. crystalloids were associated with a lower incidence of several PONV outcomes. However, a number of PONV outcomes failed to reach statistical significance, perhaps due to the lack of power. Thus, studies sufficiently powered for the less frequent outcomes (e.g. POV) are required.

Effect of nasal cannula oxygen administration on oxygen concentration at facial and adjacent landmarks.

An oxygen-enriched atmosphere enhances the potential for operating-room fires. We thus determined oxygen concentrations at various facial landmarks during oxygen administration via nasal cannulae. Thirteen supine volunteers were draped similarly to patients undergoing a cervical-node biopsy. Oxygen was delivered in random order through nasal cannulae at rates of 2, 4, and 6 l x min(-1). Oxygen concentration was measured at pre-determined facial landmarks and also distal to the drape at non-facial sites. At a flow of 2 l x min(-1), oxygen concentrations exceeded 23% only within a few centimetres of the nasal cannula. Concentration increased as a function of flow, but rarely exceeded 26%. At all flow rates, concentrations distal to the drape were < 24%. To reduce combustion risk, ignition sources should be kept at least 10 cm from the oxygen outlet when using nasal cannula at a flow rate > or = 4 l x min(-1).

Remifentanil for general anaesthesia: a systematic review.

We performed a quantitative systematic review of randomised, controlled trials that compared remifentanil to short-acting opioids (fentanyl, alfentanil, or sufentanil) for general anaesthesia. Eighty-five trials were identified and these included a total of 13 057 patients. Intra-operatively, remifentanil was associated with clinical signs of deeper analgesia and anaesthesia, such as fewer responses to noxious stimuli (relative risk 0.65, 95% CI 0.48-0.87), more frequent episodes of bradycardia (1.46, 1.04-2.05), more hypotension (1.68, 1.36-2.07) and less hypertension (0.60, 0.46-0.78). Postoperatively, remifentanil was associated with faster recovery (difference in extubation time of -2.03, 9.5% CI, -2.92 to -1.14 min), more frequent postoperative analgesic requirements (1.36, 1.21-1.53) and fewer respiratory events requiring naloxone (0.25, 0.14-0.47). Remifentanil had no overall impact on postoperative nausea (1.03, 0.97-1.09) or vomiting (1.06, 0.96-1.17), but was associated with twice as much shivering (2.15, 1.73-2.69). Remifentanil does not seem to offer any advantage for lengthy, major interventions, but may be useful for selected patients, e.g. when postoperative respiratory depression is a concern.

Ondansetron does not reduce the shivering threshold in healthy volunteers.

BACKGROUND: Ondansetron, a serotonin-3 receptor antagonist, reduces postoperative shivering. Drugs that reduce shivering usually impair central thermoregulatory control, and may thus be useful for preventing shivering during induction of therapeutic hypothermia. We determined, therefore, whether ondansetron reduces the major autonomic thermoregulatory response thresholds (triggering core temperatures) in humans. METHODS: Control (placebo) and ondansetron infusions at the target plasma concentration of 250 ng ml(-1) were studied in healthy volunteers on two different days. Each day, skin and core temperatures were increased to provoke sweating; then reduced to elicit peripheral vasoconstriction and shivering. We determined the core-temperature sweating, vasoconstriction and shivering thresholds after compensating for changes in mean-skin temperature. Data were analysed using t-tests and presented as means (sds); P<0.05 was taken as significant. RESULTS: Ondensetron plasma concentrations were 278 (57), 234 (55) and 243 (58) ng ml(-1) at the sweating, vasoconstriction and shivering thresholds, respectively; these corresponded to approximately 50 mg of ondansetron which is approximately 10 times the dose used for postoperative nausea and vomiting. Ondansetron did not change the sweating (control 37.4 (0.4) degrees C, ondansetron 37.6 (0.3) degrees C, P=0.16), vasoconstriction (37.0 (0.5) degrees C vs 37.1 (0.3) degrees C; P=0.70), or shivering threshold (36.3 (0.5) degrees C vs 36.3 (0.6) degrees C; P=0.76). No sedation was observed on either study day. CONCLUSIONS: /b>. Ondansetron appears to have little potential for facilitating induction of therapeutic hypothermia.