Effect of low-dose dexmedetomidine or clonidine on the characteristics of bupivacaine spinal block

BACKGROUND

The purpose of this study was to compare the onset and duration of sensory and motor block, as well as the hemodynamic changes and level of sedation, following intrathecal bupivacaine supplemented with either dexmedetomidine or clonidine.

METHODS

In a prospective, double-blind study, 60 patients undergoing transurethral resection of prostate or bladder tumor under spinal anesthesia were randomly allocated to one of three groups. Group B received 12 mg of hyperbaric bupivacaine, group D received 12 mg of bupivacaine supplemented with 3 microg of dexmedetomidine and group C received 12 mg of bupivacaine supplemented with 30 microg of clonidine. The onset times to reach peak sensory and motor levels, and the sensory and motor regression times, were recorded. Hemodynamic changes and the level of sedation were also recorded.

RESULTS

Patients in groups D and C had a significantly shorter onset time of motor block and significantly longer sensory and motor regression times than patients in group B. The mean time of sensory regression to the S1 segment was 303 +/- 75 min in group D, 272 +/- 38 min in group C and 190 +/- 48 min in group B (B vs. D and B vs. C, P < 0.001). The regression of motor block to Bromage 0 was 250 +/- 76 min in group D, 216 +/- 35 min in group C and 163 +/- 47 min in group B (B vs. D and B vs. C, P < 0.001). The onset and regression times were not significantly different between groups D and C. The mean arterial pressure, heart rate and level of sedation were similar in the three groups intra-operatively and post-operatively.

CONCLUSIONS

Dexmedetomidine (3 microg) or clonidine (30 microg), when added to intrathecal bupivacaine, produces a similar prolongation in the duration of the motor and sensory block with preserved hemodynamic stability and lack of sedation.

Resistance to cisatracurium in a patient with MELAS syndrome

There are conflicting reports on the response of mitochondrial myopathy patients to the neuromuscular blocking drugs, showing either normal response or marked sensitivity. We present a patient with MELAS syndrome who underwent Nissen fundoplication and gastrojejunostomy. Marked resistance to the nondepolarizing muscle relaxant, cisatracurium was observed. The anesthesia management, as well as the various causes of resistance to cisatracurium in this patient are discussed.

Does pancuronium or cisatracurium delay the rate of arousal following remifentanil-based anesthesia?

STUDY OBJECTIVE

The present report investigates the rate of arousal following remifentanil-based anesthesia associated with the coadministration of pancuronium, which inhibits butyrylcholinesterase, or cisatracurium, which is partially metabolized by nonspecific esterases, versus vecuronium that is eliminated independently of ester hydrolysis.

DESIGN, SETTING AND PATIENTS

Sixty patients, ASA I-II, scheduled for elective abdominal surgeries were enrolled in a double-blinded prospective study. In fact, patients were equally divided into three Groups with each Group receiving remifentanil and either one of the following three muscle relaxants: pancuronium, vecuronium or cisatracurium.

MEASUREMENTS

The rate of arousal following discontinuation of anesthesia was assessed by Modified Aldrete Score. Time to eye opening on verbal command, tracheal extubation, Modified Aldrete Score >9, and time to discharge from the recovery room were recorded.

MAIN RESULTS

Time to eye opening on verbal command, tracheal extubation, Modified Aldrete Score >9, and time to discharge from the recovery room were not significantly different between the three groups.

CONCLUSION

The results suggest that recovery following remifentanil-based anesthesia is not delayed by the coadministration of pancuronium, cisatracurium versus vecuronium; and by the use of neostigmine for reversal of neuromuscular blockade.

Comparison of three modes of patient-controlled epidural analgesia during labour

BACKGROUND AND OBJECTIVES

This study compares three modes of patient-controlled epidural analgesia in parturients during labour.

METHODS

Eighty-four women were randomized to one of three groups. The epidural solution used in all the three groups was 0.1% bupivacaine with fentanyl 2 microg mL(-1). Patients were able to self administer a demand dose of 3 mL with a lockout interval of 6 min in Group A, 6 mL with a lockout interval of 12 min in Group B and 9 mL with lockout interval of 18 min in Group C. All patients received a background infusion at a rate of 6 mL h(-1). Visual analogue pain scores, pinprick analgesia and motor block were assessed hourly by a blinded observer. The physician-administered supplementation and the cumulative dose of bupivacaine were also compared between the three groups.

RESULTS

Pain scores, sensory level and motor block were not different among the study groups. Patients' satisfaction was rated good to excellent with no difference among groups. The cumulative dose of bupivacaine was not significantly different. However, there was a trend towards a decreased need for rescue analgesia in Group C. Within each group, the physician-administered supplementations were significantly higher during the second stage of labour than during the first stage (P < 0.05).

CONCLUSION

The three modes of patient-controlled epidural analgesia supplemented by a background infusion of 6 mL h(-1) were equally effective for labour analgesia with a trend for decreased rescue analgesia in the group with a larger bolus dose and a longer lockout interval.

A Comparison of Sevoflurane-Propofol Versus Sevoflurane or Propofol for Laryngeal Mask Airway Insertion in Adults

In a prospective, randomized study, we investigated the incidence of successful insertion of laryngeal mask airway (LMA) at the first attempt and the incidence of side effects after LMA insertion using the combination of sevoflurane and propofol as compared with either sevoflurane or propofol alone for induction of anesthesia. Eighty-three unpremedicated ASA physical status I-II patients were anesthetized with a single vital capacity breath (VCB) of sevoflurane 8% supplemented with IV propofol 1.5 mg/kg, a single VCB of sevoflurane 8%, or IV propofol 3 mg/kg. The coinduction technique was associated with the most frequent incidence of successful LMA insertion at the first attempt (93.5%) than either sevoflurane alone (46%) or propofol alone (61.5%) (P < 0.001). Propofol-induced induction of anesthesia allowed the fastest insertion of LMA and was associated with the least frequent incidence of postoperative nausea and vomiting. However, this advantage of propofol was offset by a frequent incidence of pain on injection (69%) and the occurrence of movements during insertion of the LMA (50% in the propofol group versus 19% and 26% in the sevoflurane and sevoflurane-propofol groups, respectively; P < 0.05), as well as a more frequent incidence of apnea (84% in the propofol group versus 7% and 16% in the sevoflurane and sevoflurane-propofol groups, respectively; P < 0.001). The report shows that induction of anesthesia with sevoflurane-propofol combined provides a frequent incidence of successful LMA insertion at the first attempt that is associated with an infrequent incidence of apnea.

L’administration prophylactique de bleu de méthylène chez un patient atteint de méthémoglobinémie congénitale

PURPOSE

To report the beneficial effect of prophylactic methylene blue administration before induction of anesthesia in a patient with congenital methemoglobinemia.

CLINICAL FEATURES

A 26-yr-old male patient known to have congenital methemoglobinemia was scheduled for turbinectomy under general anesthesia. The patient was clinically cyanotic with a pulse oximetry of 91%. Arterial blood gas analysis showed a partial pressure of oxygen (PaO(2)) of 81.3 mmHg associated with a fractional oxyhemoglobin of 80.7%, and a methemoglobin fraction of 0.159. Preoperative iv administration of 1 mg.kg(-1) of methylene blue resulted, within five minutes, in a decrease of methemoglobin fraction down to 0.05 associated with an increase of the fractional oxyhemoglobin saturation up to 94.7%. After two hours, the methemoglobin fraction decreased to 0.01 and the fractional oxyhemoglobin concentration increased to 97.7%. Induction of anesthesia as well as intraoperative and postoperative course were uneventful without any episode of hypoxemia. Postoperatively, the methemoglobin fractions remained low for 24 hr, to be followed by a gradual increase up to 0.02 on the second day to reach 0.094 on the fifth day.

CONCLUSION

The prophylactic preoperative methylene blue administration in a patient with congenital methemoglobinemia significantly decreased the methemoglobin level and increased the fractional oxygen saturation with a consequent increase of the safety margin against perioperative hypoxemia.

Preoperative caudal block prevents emergence agitation in children following sevoflurane anesthesia

BACKGROUND

The frequency of emergence agitation in children is increased following sevoflurane anesthesia. However, controversies still exist concerning the exact etiology of this postanesthetic problem. Although this phenomenon is present with adequate pain relief or even following pain-free procedures, pain is still regarded as a major contributing factor.

METHODS

In a prospective, randomized, double-blind study, we enrolled 48 premedicated and calm 2-6-year-old children undergoing inguinal hernia repair. We assigned children to one of two groups: children assigned to the caudal group (n = 24) received a caudal block to supplement sevoflurane, while children assigned to the fentanyl group (n = 24) received a bolus injection of 1 microg kg(-1) intravenous fentanyl before skin incision to supplement sevoflurane. In the post anesthesia care unit, all children were received by their parent, and the incidence of emergence agitation and pain scores, as well as hemodynamic changes, were compared in both groups.

RESULTS

Forty-four children completed the study. In the fentanyl group, 59% of the children were agitated following emergence from anesthesia as compared to 4.5% in the caudal group (P < 0.001). Also, pain scores, mean values of heart rate and blood pressure as well as morphine requirement were significantly higher in the post anesthesia care unit in the fentanyl group compared to the caudal group.

CONCLUSION

Our results show that in children undergoing inguinal hernia repair, pain control with a preoperative caudal block as compared to intraoperative intravenous fentanyl significantly reduces the incidence of emergence agitation and pain scores following sevoflurane anesthesia.

End-tidal CO2 for prediction of cardiac output following weaning from cardiopulmonary bypass

This prospective study included 32 patients undergoing cardiopulmonary bypass (CPB) for elective coronary artery bypass grafting correlates the respiratory end-tidal CO2 (ETCO2) during partial separation from CPB with cardiac output (CO) following weaning from CPB. After induction of general anesthesia, a pulmonary artery catheter was inserted for measurement of cardiac output by thermodilution. Patients were monitored using a 5-lead ECG, pulse oximeter, invasive blood pressure monitoring, rectal temperature probe, and end-tidal capnography. At the end of surgery, patients were weaned from CPB in a stepwise fashion. Respiratory ETCO2 and in-line venous oximetry were continuously monitored during weaning. The ETCO2 was recorded at quarter pump flow and after complete weaning from CPB. Following weaning from CPB, CO was measured by thermodilution. The CO values were correlated with the ETCO2 during partial bypass and following weaning from bypass. Regression analysis of ETCO2 at quarter-flow and post-bypass CO showed significant correlation (r = 0.57, p < .001). Also, regression analysis of ETCO2 after complete weaning from bypass and post-bypass CO showed significant correlation (r = 0.6, p = .002). The correlation between ETCO2 and CO showed that an ETCO2 >30 mm Hg during partial CPB will always predict an adequate CO following weaning from CPB. An ETCO2 <30 mm Hg may denote either a low or a normal cardiac output and hence other predictive parameters such as SvO2 must be added.

Oxygenation using tidal volume breathing after maximal exhalation

We compared, in volunteers, the oxygenation achieved by tidal volume breathing (TVB) over a 3-min period after maximal exhalation with that achieved by TVB alone. Twenty-three healthy volunteers underwent the two breathing techniques in a randomized order. A circle absorber system with an oxygen flow of 10 L/min was used. The end-expiratory oxygen concentration (EEO(2)) was monitored at 15-s intervals up to 3 min. TVB after maximal exhalation produced EEO(2) values of 68% +/- 5%, 75% +/- 5%, and 79% +/- 4% at 30, 45, and 60 s, respectively, which were significantly larger (P < 0.05) than the corresponding values obtained with TVB alone (58% +/- 5%, 66% +/- 6%, and 71% +/- 5%, respectively). In both techniques, the EEO(2) increased exponentially, with time constants of 35 s during TVB after maximal exhalation versus 58 s during TVB without prior maximal exhalation. In conclusion, maximal exhalation before TVB can hasten preoxygenation by decreasing the nitrogen content of the functional residual capacity, with a consequent increase of EEO(2) to approximately 70% in 30 s and 80% in 60 s.

IMPLICATIONS

Oxygenation by using maximal exhalation before tidal volume breathing produced a significantly faster increase in end-expiratory oxygen concentration than oxygenation with tidal volume breathing alone.

Laryngeal mask airway for ventilation during diagnostic and interventional fibreoptic bronchoscopy in children

BACKGROUND

The use of the flexible fibreoptic bronchoscope in infants and children has expanded to include both interventional and diagnostic bronchoscopy. The present report utilizes the laryngeal mask airway (LMATM) for ventilation and anaesthesia administration in children during fibreoptic bronchoscopy using an adult bronchoscope.

METHODS

The technique was used in 10 children; their age ranged between 1.2 and 5 years. Six of these children had a history of foreign body aspiration and underwent interventional bronchoscopy, while four children underwent diagnostic bronchoscopy. Anaesthesia was induced by facemask using sevoflurane 6-8% followed by the insertion of a LMA size 2 or 2.5. A swivel adapter connected the proximal end of the LMA to the T-piece anaesthesia system. Anaesthesia was then maintained with spontaneous breathing of sevoflurane 2-4% in oxygen, delivered via the LMA. A flexible adult fibreoptic bronchoscope (outer diameter 4.9 mm) was inserted via the swivel adapter.

RESULTS

The procedure could be accomplished successfully in the 10 patients. However, one child developed laryngospasm that was easily relieved by deepening the level of anaesthesia. In a second child hypoxia and hypercarbia occurred and were relieved by intermittent withdrawal of the fibreoptic bronchoscope.

CONCLUSIONS

Laryngeal mask airway is a safe and effective adjunct to fibreoptic bronchoscopy under general anaesthesia in children. Its larger internal diameter compared with a tracheal tube permits the use of relatively large fibreoptic bronchoscope without a significant increase in airway resistance.

Amniotic fluid embolus: can we affect the outcome?

PURPOSE OF REVIEW

Amniotic fluid embolism is a rare catastrophe unique to pregnancy. Its mortality rate remains high despite efforts at prompt and aggressive management protocols, highlighting the need to maintain a high index of suspicion.

RECENT FINDINGS

The intrusion of amniotic fluid into the maternal bloodstream may lead in certain women to a complex series of physiological reactions mimicking those seen in human anaphylaxis or sepsis, negating the purely embolic phenomenon theory as previously understood. The clinical picture is the sudden onset of cardiovascular collapse, cyanosis, haemorrhage or disseminated intravascular coagulopathy, during or soon after delivery.

SUMMARY

The mainstay of a successful outcome remains the identification of high-risk patients, as well as early clinical diagnosis and management.

Intravenous lidocaine as adjuvant to sevoflurane anesthesia for endotracheal intubation in children

IMPLICATIONS

Supplementing a sevoflurane induction of anesthesia in children with IV lidocaine 2 mg/kg can suppress cough after tracheal intubation and thus improve intubating conditions. In addition, lidocaine minimizes blood pressure fluctuations after tracheal intubation.

Alarming hypoxemia during one-lung ventilation in a patient with respiratory bronchiolitis-associated interstitial lung disease

PURPOSE

To report a patient with respiratory bronchiolitis-associated interstitial lung disease (RB-ILD) who developed severe hypoxemia during one-lung ventilation (OLV).

CLINICAL FEATURES

A 27-yr-old female, ex-smoker presented with productive cough and dyspnea of 18-month duration. The chest x-ray revealed diffuse abnormalities involving both lungs consisting of interstitial emphysema with irregular shadowing. Preoperative PaO(2) was 88 mmHg and pulmonary function tests showed moderate obstructive disease. The patient underwent right open lung biopsy. After induction of anesthesia, a left double lumen tube was inserted and its position verified with auscultation and fibreoptic bronchoscopy. Upon initiation of OLV, the patient developed severe hypoxemia and the PaO(2) dropped from 500 mmHg during two-lung ventilation (TLV) to 50 mmHg. Hypoxemia was readily corrected by resuming TLV.

CONCLUSION

The severe hypoxemia during OLV in this patient with RB-ILD may be attributed to impaired hypoxic pulmonary vasoconstriction. Other causes were not excluded. Caution is warranted when initiating OLV in these patients.

Hypothermia and excessive sweating following intrathecal morphine in a parturient undergoing cesarean delivery

OBJECTIVE

Intrathecal morphine has been used for the relief of postoperative pain following cesarean delivery. We report a case of postoperative hypothermia down to 33.6 degrees C associated with excessive sweating in patient undergoing elective cesarean delivery under spinal bupivacaine anesthesia who received intrathecal morphine for postoperative pain management.

CASE REPORT

A healthy 31-year-old multigravida presented for elective cesarean delivery. Following prehydration with 500 mL hemaccel, she had a subarachnoid block, using hyperbaric bupivacaine 12 mg and morphine 200 microgram, via a 25-gauge Whitacre needle. In the recovery room, 3 hours after induction of spinal anesthesia, the patient's sublingual temperature was 33.6 degrees C and she was noted to be sedated and sweating excessively. During the next 2 hours, the patient was still hypothermic despite active warming. She also complained of severe nausea, vomiting, and moderate pruritus. Following administration of naloxone 400 microgram sedation, vomiting, and pruritus were relieved. Also, the patient experienced excessive shivering, and her body temperature started to increase in association with a concurrent decrease of sweating. The postoperative hypothermia and excessive sweating in our patient may be related to the cephalad spread of the intrathecal morphine within the cerebrospinal fluid (CSF) to reach the level of opioid receptors in the hypothalamus, causing a perturbation of the thermoregulatory center. This effect could be counteracted by administration of naloxone.

CONCLUSIONS

Intrathecal morphine may cause disruption of thermoregulation resulting in hypothermia associated with excessive sweating.

A combination of alfentanil-lidocaine-propofol provides better intubating conditions than fentanyl-lidocaine-propofol in the absence of muscle relaxants

PURPOSE

To compare the ease of tracheal intubation without the use of muscle relaxants following an alfentanil-lidocaine-propofol sequence vs a fentanyl-lidocaine-propofol sequence.

CLINICAL FEATURES

In 80 ASA I and II adult patients undergoing elective laparoscopic surgery, we compared the intubating conditions following alfentanil 20 microg x kg(-1), lidocaine 1.5 mg x kg(-1), propofol 3 mg x kg(-1) (Group I; n = 40) vs fentanyl 2 microg x kg(-1), lidocaine 1.5 mg x kg(-1), propofol 3 mg x kg(-1) (Group II; n = 40). The intubating conditions were scored by jaw relaxation, vocal cord position and response to intubation, as well as by blood pressure and heart rate changes. The intubating conditions were good or excellent in 95% of patients in Group I vs 62.5% of patients in Group II (P < 0.05). Blood pressure decreased from a preinduction value of 86 +/- 13 mmHg to 72 +/- 28 mmHg and 74 +/- 19 mmHg in Group I, and from 85 +/- 12 mmHg to 78 +/- 15 mmHg and 78 +/- 12 mmHg in Group II, one and five minutes following intubation (P < 0.05). This drop in blood pressure was not different between the two groups.

CONCLUSION

An alfentanil-lidocaine-propofol sequence offers significantly better intubating conditions than a fentanyl-lidocaine-propofol sequence in healthy adult patients.

Advancing the tracheal tube over a flexible fiberoptic bronchoscope by a sleeve mounted on the insertion cord

The advancement of an endotracheal tube (ETT) over a flexible fiberoptic bronchoscope (FOB) is often impeded at the glottis. This is attributed to the creation of a cleft by the difference in the outer diameter of the fiberscope and the internal diameter of the tube. We designed a conical-shaped polyvinyl chloride sleeve to fit the insertion cord. This report compares the ease of advancement of the tube over a sleeved versus a nonsleeved bronchoscope. General anesthesia was induced, and one anesthesiologist introduced the FOB (a 3.8-mm Olympus LF2). Patients were randomly assigned to undergo tracheal intubation with the regular bronchoscope (25 patients) or the sleeved bronchoscope (25 patients). The FOB was advanced to approximately 1 cm above the carina. A blinded operator advanced the tube over the bronchoscope. The ETT was successfully advanced over the nonsleeved bronchoscope into the trachea on the first attempt in 64% of the patients, whereas tracheal intubation succeeded from the first attempt in 96% of patients when the sleeved FOB was used (P < 0.05). Advancement of the ETT over the fiberscope can be facilitated by using a conically shaped sleeve mounted on the insertion cord.

IMPLICATIONS

This report shows that a conical sleeve mounted on the insertion cord of a fiberoptic bronchoscope will facilitate advancing the endotracheal tube into the trachea.