Percutaneous fluoroscopic removal of a knotted Swan-Ganz catheter in a patient with a persistent left-sided superior vena cava.

Knotting of intravascular catheters is an uncommon but a well-recognized occurrence. The Swan-Ganz catheter (SGC) is the one that knots most commonly. A case of a knotted SGC is described in a patient with a persistent left-sided superior vena cava, and we propose that the presence of a left-sided superior vena cava is a risk factor for knot formation not previously reported. We review the published work on the risk factors for knot formation and on the techniques used to remove knotted SGC. We describe a technique using a gooseneck snare and Omni Flush catheter (Angiodynamics, Queensbury, NY, USA) to loosen and untie a knotted SGC.

Regional anesthesia for obstetrics.

The practice of administration of labor analgesia has undergone dramatic changes this decade. This is largely attributable to unparalleled interest in the field by many dedicated and capable investigators around the world. Through their efforts, this decade has witnessed the introduction of new techniques (pencil point needles, CSE, PCEA, ultradilute epidural regimens) that have permitted us to come closer than ever to realizing the goal of complete relief from the pain and suffering of labor while safeguarding the well-being of mother and child and minimizing effects on the labor process. Neuraxial anesthetic techniques and modern multimodal analgesic approaches to postoperative pain relief now minimize the effects of cesarean delivery on maternal satisfaction and participation in the birth process.

General anesthesia with remifentanil for Cesarean section in a parturient with an acoustic neuroma.

PURPOSE: To describe the anesthetic management of a parturient with a large acoustic neuroma undergoing general anesthesia with remifentanil for Cesarean section. CLINICAL FEATURES: A near-term parturient presented with a large intracranial mass. Cesarean section under general anesthesia was elected one week prior to craniotomy for tumour resection. Remifentanil infusion, 0.2-1.0 microg x kg(-1) x min(-1), was used from induction to emergence of general anesthesia. The neonate was born seven minutes after the remifentanil infusion was started. She had normal umbilical cord pH and her Apgar scores were 7 and 8, at one and five minutes respectively. Although the neonate received supplemental oxygen, she did not require naloxone. Both mother and neonate made an uneventful recovery. CONCLUSION: Remifentanil was effective in producing stable hemodynamic conditions, without severe neonatal respiratory depression, during induction and maintenance of general anesthesia for a Cesarean delivery in a parturient with a large intracranial tumour.

The effects of needle bevel orientation during epidural catheter insertion in laboring parturients.

UNLABELLED: Lateral needle bevel orientation during identification of the epidural space has been recommended to reduce the risk of postdural puncture headache (PDPH). Rotation to cephalad or caudad orientation before catheter insertion is assumed necessary for analgesic success. We prospectively compared the effects of catheter insertion through lateral- and cephalad-oriented Tuohy needle bevels in laboring parturients. Anesthesiology residents were randomized to identify the epidural space with bevels oriented cephalad or lateral. Catheters were inserted without needle rotation. Outcomes compared included ease of insertion, analgesic effectiveness, and complications. We evaluated 534 catheter insertions in 500 parturients. Initial catheter insertion produced satisfactory analgesia in 80.2% of the lateral group versus 91.1% of the cephalad group (P < 0.001). Resistance preventing catheter insertion accounted for the difference. There were no differences in i.v. cannulation (5.8% vs 5.1%), dural puncture (3.8% vs 2.0%), PDPH (0.4% vs 0.7%), or asymmetric block (31% vs 27%). There was a slightly higher rate of paresthesias in the lateral group (31% vs 23%; P = 0.048). In 78% of parturients experiencing both paresthesias and asymmetric block, the side of the paresthesia and greater extent of block were the same. Analgesic effectiveness, as measured by using a visual analog scale, was not different between the groups. IMPLICATIONS: Two methods of epidural catheter insertion were compared in laboring parturients. Catheter insertion with the needle orifice oriented cephalad was associated with the greatest initial success and the fewest complications.

Cardiovascular collapse associated with extreme iatrogenic PEEPi in patients with obstructive airways disease.

Chronic obstructive pulmonary disease (COPD) is commonly associated with positive alveolar pressure at end-expiration (intrinsic PEEP or PEEPi) caused by a prolonged expiratory time constant. Positive pressure ventilation (PPV) with large tidal volumes and high ventilatory frequencies may cause pulmonary hyperinflation, with increases in intrathoracic pressure and cardiopulmonary effects. We report two cases, one of fatal pulseless electrical activity, the other of life-threatening hypotension, both during vigorous manual PPV, in patients with severe COPD. This phenomenon has been well-recognized by intensivists but is reported poorly more widely.

Intrathecal hypobaric versus hyperbaric bupivacaine with morphine for cesarean section.

UNLABELLED: Both hyper- and hypobaric solutions of bupivacaine are often combined with morphine to provide subarachnoid anesthesia for cesarean section. Differences in the baricity of subarachnoid solutions influence the intrathecal distribution of anesthetic drugs and would be expected to influence measurable clinical variables. We compared the effects of hyper- and hypobaric subarachnoid bupivacaine with morphine to determine whether one has significant advantages with regard to intraoperative anesthesia and postoperative analgesia in term parturients undergoing elective cesarean section. Thirty parturients were randomized to receive either hyper- or hypobaric bupivacaine (15 mg) with morphine sulfate (0.2 mg). Intraoperative outcomes compared included extent of sensory block, quality of anesthesia, and side effects. Postoperative outcomes, including pain visual analog scale scores, systemic analgesic requirements, and side effects, were monitored for 48 h. Sedation effects were quantified and compared using Trieger and digit-symbol substitution tests. We detected no differences in sensory or motor block, quality of anesthesia, quality of postoperative analgesia, incidence of side effects, or psychometric scores. Both preparations provide highly satisfactory anesthesia for cesarean section and effective postoperative analgesia. IMPLICATIONS: Dextrose alters the density of intrathecal bupivacaine solutions and is thought to influence subarachnoid distribution of the drug. We randomized parturients undergoing cesarean section to one of two often used spinal bupivacaine preparations, hypobaric and hyperbaric. We detected no differences in clinical outcomes between groups.

The effects of general versus epidural anesthesia for outpatient extracorporeal shock wave lithotripsy.

UNLABELLED: Although many anesthetic techniques are described for immersion extracorporeal shock wave lithotripsy (ESWL), regional and i.v. techniques are the most commonly reported. This randomized, prospective study compared general anesthesia (GA) and epidural anesthesia (EPID) with regard to effectiveness, side effects, induction time, and recovery in patients undergoing ESWL using an unmodified Dornier HM-3 lithotriptor. Twenty-six healthy outpatients were randomized to GA (propofol, N2O, laryngeal mask airway) or EPID (lidocaine 1.5% with epinephrine). Intraoperative and postoperative supplemental medications, side effects, and complications were noted. Induction times and times required to meet standard recovery criteria were compared between groups. Patients were surveyed regarding their satisfaction with anesthesia. All patients in the EPID group had effective blocks with a single catheter insertion and local anesthetic injection. In the GA group, the LMA was inserted successfully in all patients. Time from room entry to procedure start was significantly less in the GA group (23 +/- 11 vs 34 +/- 9 min; P < 0.05). Patients in the GA group were ready for discharge home earlier (127 +/- 59 vs 178 +/- 49 min; P < 0.05). Only three patients experienced nausea (one in the GA group, two in the EPID group). There were no differences in patient or urologist satisfaction with anesthesia. We conclude that GA is associated with a rapid recovery compared with EPID. IMPLICATIONS: General anesthesia with propofol, nitrous oxide, and a laryngeal mask airway is comparable to epidural anesthesia with lidocaine for outpatient extracorporeal shock wave lithotripsy procedures. However, early recovery is more rapid after general anesthesia compared with epidural anesthesia.

Midazolam premedication increases sedation but does not prolong discharge times after brief outpatient general anesthesia for laparoscopic tubal sterilization.

Preoperatively administered midazolam may contribute to postoperative sedation and delayed recovery from brief outpatient general anesthesia, particularly in patients who receive significant postoperative opioid analgesics. We evaluated the effects of midazolam premedication (0.04 mg/kg) on postoperative sedation and recovery times after laparoscopic tubal sterilization (Falope rings) in 30 healthy women in a randomized, double-blind, placebo-controlled study. Patients received midazolam or saline-placebo intravenously 10 min before anesthesia. General anesthesia was induced with fentanyl, propofol, and mivacurium and was maintained with N2O and isoflurane. Sedation was quantified before and after premedication and 15, 30, and 60 min after emergence from anesthesia, using the digit-symbol substitution (DSST) and Trieger dot (TDT) tests. Management of postoperative pain and nausea and discharge criteria were standardized. Groups were similar with respect to age, weight, and duration of surgery and anesthesia. Midazolam was associated with impairment of performance on the TDT and DSST after premedication administration and 15 (TDT and DSST) and 30 (DSST) min after postanesthesia care unit (PACU) arrival. There were no differences in PACU time and time to discharge-readiness. In conclusion, midazolam premedication augments postoperative sedation in this population but does not prolong recovery times.

Densities of dextrose-free intrathecal local anesthetics, opioids, and combinations measured at 37 degrees C.

Dextrose-free anesthetic medications are commonly used to provide subarachnoid anesthesia and analgesia. Hypobaricity has been proposed as a mechanism to explain postural effects on the extent of sensory block produced by these drugs. Densities of dextrose-free solutions of local anesthetics and opioids, and commonly used anesthetic/opioid mixtures were determined at 37.00 degrees C for comparison with the density of human cerebrospinal fluid (CSF). Measurements accurate to 0.00001 g/mL were performed using a mechanical oscillation resonance frequency density meter. All undiluted solutions tested are hypobaric relative to human lumbar CSF with the exception of lidocaine 1.5% and 2.0% with epinephrine 1:200,000. All mixtures of local anesthetics and opioids tested are hypobaric. We observed good agreement between measured densities and calculated weighted average densities of anesthetic mixtures. While the influence of baricity on the clinical effects of dextrose-free intrathecal anesthetics remains controversial, attempts to attribute postural effects to the baricity of these drugs requires establishment of accurate density values. These density data may facilitate elucidation of the mechanisms underlying the behavior of dextrose-free intrathecal anesthetics.

Maternal posture influences the extent of sensory block produced by intrathecal dextrose-free bupivacaine with fentanyl for labor analgesia.

The cephalad extent of sensory block produced by intrathecal (IT) dextrose-free local anesthetics and opioids has been reported to be quite variable. Most reports describing the effects of IT analgesics do not control for patients posture. Because these medications are hypobaric relative to cerebrospinal fluid (CSF), parturients in a sitting position may develop greater cephalad extents of sensory block than those in a lateral position during IT injection. Parturients in labor were randomized to sitting or lateral position during IT administration of dextrose-free bupivacaine 0.25% with fentanyl 0.005%. Extent of sensory block was evaluated at intervals thereafter. Free flow of CSF was obtained in 20 parturients. Those in a sitting position during IT injection had significantly higher maximal cephalad extent of block than those in a lateral position (mean +/- SD, T-3.1 +/- 2.9 vs T-6.3 +/- 3.4, P = 0.036). Mean cephalad extent of block was greater in the sitting group at 20 and 30 min. When sensory block asymmetry was observed, the extent of block was greater on the nondependent side. Posture during IT injection of this dextrose-free analgesic combination affects extent of sensory block in laboring parturients.

Density of lumbar cerebrospinal fluid in pregnant and nonpregnant humans.

BACKGROUND: Dextrose-free local anesthetics and opioids, alone and in combinations, are being used increasingly to provide subarachnoid anesthesia and analgesia. These dextrose-free drugs have been described as hypobaric by some and isobaric by others. To accurately classify anesthetics with regard to baricity, the density of cerebrospinal fluid (CSF) must be known. The authors sought to determine the exact density of human CSF, and determine whether CSF density is altered by pregnancy. METHODS: Density measurements accurate to 0.00001 g/ml were made at 37.00 degrees C, using a mechanical oscillation resonance frequency density meter. Cerebrospinal fluid samples were obtained from 44 patients during spinal anesthesia. Five groups were studied: men, and premenopausal, postmenopausal, term pregnant, and postpartum women. RESULTS: Mean CSF densities in men (1.00064 +/- 0.00012 g/ ml), postmenopausal women (1.00070 +/- 0.00018 g/ml), and nonpregnant premenopausal women (1.00049 +/- 0.00004 g/ ml) were significantly greater than in term pregnant (1.00030 +/- 0.00004 g/ml) and postpartum (1.00034 +/- 0.00005 g/ml) women. Cerebrospinal fluid density did not correlate with age. CONCLUSIONS: Mean CSF density varies in different patient subpopulations. Pregnancy and the immediate postpartum period are associated with the lowest CSF densities. In addition, the cutoff values defining hypobaricity (mean CSF density minus three standard deviations) are greater than previously reported. Accurate CSF density values should be used when considering baricity as a mechanism for clinical observations of dextrose-free intrathecal local anesthetics and opioids. Gestational status also should be considered.

High spinal anesthesia after epidural test dose administration in five obstetric patients.

BACKGROUND AND OBJECTIVES: A commonly used test dose in parturients receiving continuous lumbar epidural analgesia for labor consists of 3 mL of dextrose-free 1.5% lidocaine with 1:200,000 epinephrine. METHODS: of 1,962 obstetric epidural anesthetics administered over a 17-month period, unintentional subarachnoid placement of the epidural catheter was detected by injection of the test dose in five laboring patients. The characteristics of the resulting subarachnoid blocks were studied. RESULTS: After negative aspiration for cerebrospinal fluid in each case, test dose injection resulted in the rapid onset of high sensory block with associated motor and sympathetic block, accompanied by significant hypotension requiring aggressive treatment. CONCLUSIONS: While this test dose appears to be a sensitive indicator of an unexpected subarachnoid catheter, the resulting excessive spinal blocks in these laboring patients raise the question of its safety.

Responses to nondepolarizing neuromuscular blockers and succinylcholine in von Recklinghausen neurofibromatosis.

Patients with type 1 neurofibromatosis (NF-1) have been reported to have prolonged responses to nondepolarizing (ND) neuromuscular blockers (NMBs). Responses to succinylcholine (SCh) have been described as increased, decreased, or normal. The purpose of this study was to assess responses to NMBs in NF-1 patients in order to determine the clinical significance of abnormal responses. We retrospectively identified all NF-1 patients who received anesthetics at Strong Memorial Hospital between January 1, 1984 and December 31, 1994. We then reviewed all anesthetic records to classify responses to NMBs as normal, abnormal, or indeterminate. Records of 114 anesthetics provided to 44 NF-1 patients were reviewed. Nondepolarizing NMBs were used during 73 anesthetic cases in 38 patients. Responses were normal in 69 cases and indeterminate in 4 (3 in patients with normal responses during other anesthetics). SCh was used during 42 anesthetic cases in 23 patients. Responses were normal in all but one case (indeterminate) in a patient who had had other documented normal responses. Standard milligram per kilogram doses of NMBs were used in all cases, and in none was there evidence of abnormal response. The risk of abnormal response to NMBs in individuals with NF-1 appears to be minimal. We recommend no alteration in dosing of either SCh or ND NMBs in patients with NF-1.