Noninvasive tissue oxygen saturation determined by near-infrared spectroscopy following peripheral nerve block.

BACKGROUND: Noninvasive physiologic measurement of cutaneous tissue oxygenation using near-infrared spectroscopy (NIRS) has become increasingly common in cardiovascular and plastic surgery. The aim of this study was to determine whether clinically available NIRS-based monitors could detect changes in tissue oxygen saturation (rSO(2)) following a variety of peripheral nerve blocks. We hypothesize that peripheral nerve blocks will produce detectable changes in cutaneous tissue oxygenation levels that can be measured by noninvasive NIRS-based oximetry. METHODS: Forty adult patients scheduled for pre-operative peripheral nerve block placement were enrolled. Prior to block placement, NIRS sensors were placed on the operative and nonoperative (control) limb. Baseline tissue oxygen saturation values were obtained prior to dosing of the nerve block, and measurements were recorded every 5 min thereafter. RESULTS: Initial rSO(2) values were higher in the operative vs. control limbs prior to nerve block placement. Tissue oxygen saturation increased in the blocked, but not control, limbs with time. Subgroup analysis suggested statistically significant differences in rSO(2) values in blocked vs. control limbs for cervical paravertebral, infraclavicular, and femoral nerve blocks. CONCLUSIONS: Our results demonstrated sustained increases in tissue rSO(2) values following peripheral nerve block placement, in addition to higher initial rSO(2) values in operative limbs prior to block placement. Further investigations are necessary to define the expected baseline rSO(2) values in operative and control limbs. Future efforts utilizing NIRS-based detection of tissue ischemia should consider the small but significant changes in rSO(2) resulting from a successful nerve block.

Surface mapping of peripheral nerves in children with a nerve stimulator.

Defining anatomical landmarks may be difficult in the growing child. With the aid of a peripheral nerve stimulator, the path of many superficial peripheral nerves can be 'mapped' prior to skin penetration by stimulating the motor component of the peripheral nerve percutaneously with a 2-3.5 mA output. The required current will vary and is dependent upon the depth of the nerve and the moistness of the overlying skin. This 'nerve mapping technique' has proved particularly useful for brachial plexus, axillary, ulna and median nerve blocks in the upper limb and femoral and popliteal nerve blocks in the lower limb. It is a useful teaching tool and improves the success rate of peripheral nerve blocks in children of all ages.

A comparison of propofol and remifentanil for sedation and limitation of movement during periretrobulbar block.

STUDY OBJECTIVES: To compare clinical conditions in patients sedated with propofol or remifentanil during combined peri-bulbar and retrobulbar block (PRBB) for cataract surgery. DESIGN: Prospective, randomized, double-blind study. SETTING: Private clinic. PATIENTS: 106 ASA physical status I and II patients scheduled for cataract surgery. INTERVENTIONS: Patients were randomized to receive either 0.5 mg/kg propofol (Group P) or 0.3 microg/kg remifentanil (Group R) as an intravenous (IV) bolus 1 minute prior to PRBB. At the same time, patients in both groups also received 0.5 to 1 mg midazolam IV. Movement of the hands, arms, head, and eyes were counted during each stage of the procedure by an observer who was blinded to the sedation used. Heart rate (HR), blood pressure (BP), respiratory rate (RR), expiratory CO(2) (PECO(2)), and hemoglobin oxygen saturation (SaO(2)) were recorded every minute for 10 minutes after the PRBB. Anesthetic complications, recall, and the pain experienced with the block and surgery were compared between the two groups. Means and variance of the results were compared with one-way analysis of variance and Fisher's exact test. MEASUREMENTS AND MAIN RESULTS: Movements of the hands, arms, and head were significantly greater in Group P during all stages of the block. Almost no movements were recorded in the remifentanil group. Immediately after the PRBB (1 to 6 min), HRs were higher in Group P (73 +/- 11 bpm vs. 67 +/- 10 bpm; p = 0.0075), whereas the RRs were slower in Group R for the period 1 to 5 minutes after the PRBB (16 +/- 5 breaths/min vs.14 +/- 4 breaths/min; p = 0.0206). At these times, the mean PECO(2) was higher in Group R (36 +/- 7 mmHgvs. 32 +/- 9 mmHg; p = 0.0125). Nineteen patients in the propofol group sneezed during the medial peribulbar injection compared with none in the remifentanil group. Anesthetic and surgical complications were unremarkable and similar for the two groups. CONCLUSIONS: Respiratory depression with remifentanil was mild and not clinically significant. Remifentanil sedation for this application was superior to sedation with propofol.

Effects of cerebrospinal fluid loss and epidural blood patch on cerebral blood flow in swine.

BACKGROUND AND OBJECTIVES: The purpose of this study was to test the hypothesis that loss of cerebrospinal fluid (CSF) causes cerebral vasodilatation, which is reversible with peridural injection of autologous blood. METHODS: Ten pigs were anesthetized with an infusion of propofol and remifentanil and mechanically ventilated to normocapnia with air and oxygen (60%). Cisternal puncture was performed and increments of 1 mL of cerebrospinal fluid were aspirated. After each milliliter was removed, hemodynamic and respiratory variables and cerebral blood flow (CBF) were measured, the latter with a transdural laser Doppler flowmeter (BLF 21; Transonic Systems Inc, Ithaca, NY) through a cranial burr hole. After 9 mL of CSF had been removed, 10 mL autologous blood was injected into the lumbar epidural space, and the CBF and other variables were measured immediately and 5 minutes thereafter. Ten milliliters of autologous blood was then injected subdurally and the measurements repeated. Data were analyzed for significant differences from the baseline and previous values by repeated analysis of variance. RESULTS: CBF increased from 44.7 +/- 7.97 tissue perfusion units (TPU) (mean +/- SEM) at baseline to 75.3 +/- 13.53 TPU after removal of the first 7 mL of CSF (P < .0001). Following injection of 10 mL of blood into the epidural space, CBF immediately decreased to 47.6 +/- 9.18 TPU. After subdural injection of blood, the CBF decreased further to 20 +/- 3.77 TPU. CONCLUSIONS: The increase in CBF probably represents cerebral vasodilatation. The immediate return of CBF to baseline values after epidural injections of blood, and to lower values after subdural injections of blood, was probably due to vasoconstriction. The data suggest that postdural puncture headache, and its successful treatment with epidural blood patch, can probably be ascribed to cerebrovascular dynamics.

Technical note: rotator cuff tear. Intraoperative electrical stimulation of the suprascapular nerve.

We describe a method of placing an electrically conductive catheter onto the suprascapular nerve for intraoperative electrical stimulation of the nerve. This causes contractions of the supraspinatus and infraspinatus muscles that indicate rotator cuff viability, suitability for repair, direction in which the fibers contract, and the tear pattern.

Intrathecal morphine. Double-blind evaluation of optimal dosage for analgesia after major lumbar spinal surgery.

STUDY DESIGN: A prospective, randomized, double-blind study. OBJECTIVES: To evaluate the efficacy and safety of three different dosages of intrathecal morphine sulfate for postoperative analgesia after lumbar spinal fusion. SUMMARY OF BACKGROUND DATA: Analgesia and respiratory depression after intrathecal morphine sulfate injection are dose related. The optimal dose to use for major spinal surgery is not known. METHODS: Sixty patients undergoing posterolateral lumbar fusion with or without decompression were divided randomly into 3 groups of 20 patients each. Anesthesia, monitoring, and surgery were similar for all patients. Just before closing of the wound, morphine sulfate was injected into the dural sack under direct visualization. Patients in groups 1-3 received 0.2 mg, 0.3 mg, and 0.4 mg morphine, respectively. Routine analgesia, consisting of diclofenac, was prescribed to use if necessary. Measurements were made and compared between the groups at zero hours (on admission to the Intensive Care Unit), 6 hours, 12 hours, 18 hours, and 24 hours after surgery. RESULTS: At zero hours and at 12 hours after surgery, pain levels were similar in groups 2 and 3, but were significantly higher in group 1 (P < 0.05). The respiratory rate was significantly lower in group 3 than in the other two groups (P < 0.05), and the arterial CO2 tension (PaCO2) was consistently higher in group 3. PaCO2 decreased in all three groups over the first 24 hours. Pruritus and nausea did not differ among the three groups. CONCLUSIONS: For adult patients undergoing posterolateral lumbar fusion, 0.3 mg (0.004 mg/kg) is probably the optimal dose of intrathecal morphine to manage pain.

A new technique of continuous interscalene nerve block.

PURPOSE: To describes a technique of indwelling interscalene catheter placement and to evaluate its complications. METHODS: One hundred and twenty patients undergoing major shoulder surgery received interscalene nerve block (ISNB) and were studied in three groups. Group 1 ISNB using Winnie's technique; group 2 by Winnie's technique with nerve stimulator and group 3 by epidural needle and catheter technique with nerve stimulator. All patients received 20 mL bupivacaine 0.5% and group 3 patients received an additional bupivacaine 0.25% infusion. Diaphragmatic movements were measured sonographically on emergence from anesthesia. Complications were noted. A visual analogue scale (0-10) was used to assess pain four hours postoperatively. RESULTS: Mean ipsilateral diaphragmatic movements were 4+/-8, 14+/-11 and 18+/-8 mm (mean +/- SD) in groups 1, 2 and 3 respectively. This was less than contralateral movements in all three groups (P < 0.05). None of the patients in groups 2 and 3 reported postoperative pain. The block failed in 10% of group 1 patients. Complete ipsilateral phrenic nerve block occurred in 85% of the patients in group 1, 35% of group 2 and 20% of group 3 (P < 0.05). Ipsilateral recurrent laryngeal nerve paralysis occurred in 20% of the patients in group 1, 5% of group 2 and in none of the patients in group 3 (P < 0.05). Horner's syndrome was noted in group 1 (30%), group 2 (12%) but not in group 3. None of the catheters in group 3 patients dislodged after an average use of 2.8+/-2.1 days. CONCLUSIONS: Indwelling catheter placement into the brachial plexus sheath as described in this communication was effective and associated with few complications.

Evaluation of anxiolysis and pain associated with combined peri- and retrobulbar eye block for cataract surgery.

STUDY OBJECTIVES: To evaluate five different preoperative anxiolytic regimens in cataract surgery performed under regional anesthesia; to quantify the pain associated with combined peri- and retrobulbar injection (PRBI) of local anesthetic drugs; and to describe a technique of painless eye block. DESIGN: Randomized, double blind, placebo-controlled study. SETTING: Private clinic. PATIENTS: 376 ASA I and II patients presenting for cataract surgery. INTERVENTIONS: Patients were extensively briefed by the nursing staff on the various procedures. Of the 376 study patients, 136 preferred to have no anxiolytic drug. The remaining 240 patients were randomly allocated to one of six groups to receive either 3 mg of bromazepam, 6 mg of bromazepam, 0.5 mg of alprazolam, 1 mg of alprazolam, 5 mg of diazepam, or a placebo on a double-blind protocol. All patients received a standard combined peri- and retrobulbar eye block (PRBB) before surgery. MEASUREMENTS AND MAIN RESULTS: Anxiety at various stages of the procedure and PRBB were measured on visual analog scale (0-10). PRBB pain was compared with pain of intravenous (i.v.) cannula placement. On admission, anxiety of the 136 patients who preferred no anxiolytic premedication was significantly less than that of the 240 patients assigned to one of the six treatment groups (p < 0.05). There was no difference between the six treatment groups in reported anxiety before surgery (p > 0.05) except for Group 1 (3 mg bromazepam), where anxiety increased before and during PRBB administration (p < 0.05). In all six treatment groups, anxiety decreased significantly 30 minutes after medication was administered (p < 0.05). For the total group, 61.18% of patients reported more or equal pain associated with the placement of the 20-gauge i.v. cannula than by the PRBB. Of the patients who received medication, 94% stated that, should they require another eye operation, they would like the same anxiolytic treatment. No patient requested general anesthesia for their next operation or to be rendered unconscious for PRBB. CONCLUSIONS: 1. There was interpersonal variation in the level of preoperative anxiety. 2. In patients who were anxious, the anxiolytic drugs and placebo decreasedanxiety although the level of anxiety did not differ between the anxiolytic drugs or between placebo and the anxiolytic drugs. The only difference was in Group 1 patients (3 mg promazepam), who reported slightly increased anxiety before and during PRBB administration (p < 0.05). 3. Placement of the PRBB is less painful than the insertion of a 20 g i.v. cannula.

Nicky's knot--a new slip knot for arthroscopic surgery.

Slip knots are commonly used for arthroscopic knot tying techniques. Nicky's knot is a "ratchet" knot. It is a one-way slip knot. It has excellent initial holding capacity, maintaining tension on soft tissue while additional hitches are being tied.

Comparison of sodium nitroprusside- and esmolol-induced controlled hypotension for functional endoscopic sinus surgery.

The purpose of this study was to compare surgical conditions for functional endoscopic sinus surgery (FESS) under general anaesthesia during controlled induced hypotension, using either sodium nitroprusside (SNP) or esmolol. Twenty patients, assigned to receive either of the drugs as the primary hypotensive agent, were studied. The same surgeon, blinded to the hypotensive agent used and the haemodynamic variables, performed all the operations. The surgeon used a category scale (0-5) to assess surgical conditions--a value of 2-3 being ideal. Patients were positioned in 5 degrees reverse Trendelenburg position and the mean arterial blood pressure (MABP) was reduced in steps of 5 mmHg. The anaesthetist prompted category scale estimations by the surgeon following a change in any of the haemodynamic variables. Average category scale (ACS) values were compared between the two groups for four data groups, i.e., MABP > 65 mmHg (mild), 60-64 mmHg, 55-59 mmHg and 50-54 mmHg. Pre-treatment MABP was 79.8 +/- 10.4 mmHg in the SNP group and 76.1 +/- 6.8 mmHg in the esmolol group. At mild SNP-induced hypotension, surgical conditions were poor (ACS = 3.63 +/- 0.22; mean +/- SEM), while in the esmolol group, ideal surgical conditions (ACS = 2.94 +/- 0.34) were recorded at MABP > 65 mmHg. The combined effects of increased venous drainage due to the reverse Trendelenburg position, hypotension as well as capillary vasoconstriction due to unopposed alpha-adrenergic effect on the mucous membrane vasculature in the esmolol group (as opposed to vasodilatation in the SNP group) probably caused the superior surgical conditions.

Inadvertent extra-arachnoid (subdural) injection of a local anaesthetic agent during epidural anaesthesia. A case report.

Profound hypotension occurring in a patient 2 hours after initiation of combined general and epidural anaesthesia for a myocutaneous free-flap graft was found to be attributable to subdural/extra-arachnoid injection of 0.5% bupivacaine. The initial diagnosis was based on a negative aspiration test, a delayed widespread sensory and sympathetic block, and the absence of any other obvious cause for the hypotension. This was confirmed by myelography, which demonstrated an extension of the contrast medium predominantly posteriorly in the spinal canal with excessive spread along the nerve roots. Posture and coughing did not affect the spread.

Fulminant adult respiratory distress syndrome after suction lipectomy. A case report.

The adult respiratory distress syndrome developing within 24 hours in a patient who underwent suction lipectomy for body contouring under general anaesthesia is reported. During surgery, in which a total of 1.3 l of suction matter was removed, the patient became haemodynamically unstable and mildly hyperthermic. Subsequently, clinical signs and symptoms of the fat embolism syndrome developed. Aggressive haemodynamic and respiratory support over an 8-day period resulted in patient survival. Malignant hyperthermia was excluded as cause for the clinical presentation on muscle biopsy and in vitro caffeine contracture studies. Although usually complication-free, suction lipectomy may be associated with life-threatening incidents. Even suction volumes as low as 1.3 l have potential hazards, therefore the procedure merits regular postoperative observation and re-assessment.

Low-dose intrathecal morphine sulphate as sole analgesic for pain of labour in combination with elective forceps delivery. A report of 10 cases.

Preservative-free morphine sulphate (0.5 mg in 0.5 ml normal saline) was injected intrathecally as the sole analgesic in 10 primiparous patients in the first stage of labour. Elective forceps were applied under pudendal block anaesthesia to assist the second stage of labour to prevent cephalad spread during bearing down, and so reduce the side-effects of morphine sulphate. All patients reported good analgesia during the first stage of labour. There was no loss of the bearing down reflex and, except for mild peri-oral itching in 6 patients, no side-effect attributable to intrathecal morphine was noted. No side-effects of morphine sulphate were observed in any of the infants delivered. It is concluded that intrathecal morphine sulphate combined with elective forceps delivery provides a satisfactory alternative to epidural anaesthesia in those patients whose cardiovascular status demands preservation of a normal or elevated systemic vascular resistance.

Prolonged fetal bradycardia during epidural analgesia. Incidence, timing and significance.

The mechanism of episodes of fetal bradycardia during epidural analgesia is unknown in the majority of cases. This retrospective study considers the relationship between prolonged fetal bradycardia and epidural analgesia during labour. Of 705 cardiotocographs recorded during administration of epidural analgesia for patients in labour, 207 were suitable for analysis. Prolonged fetal bradycardia occurred after 40 of 366 (11%) initial or repeat injections of local anaesthetic into the epidural space. The peak incidence of onset of bradycardia was 5-20 minutes after administration, but occurrences continued throughout the 60-minute period studied. In 1 patient a single episode of fetal bradycardia occurred before administration of the epidural block. In all cases studied the 5-minute Apgar scores were 7 or better. It is concluded that administration of epidural analgesia is significantly associated with episodes of prolonged fetal bradycardia, but that there is usually a return to pre-epidural patterns. The fetal heart rate should be monitored during epidural block administration to confirm the return to baseline rate and normal variability. Episodes of fetal bradycardia that return to a normal pattern do not necessitate early delivery.

Computerized axial tomo-epidurographic and radiographic documentation of unilateral epidural analgesia.

A 23-year-old primigravid patient who received epidural analgesia for pain of labour presented with persistent, apparently irremediable, unilateral analgesia. Computerized axial tomo-epidurography demonstrated absence of circumferential spread due to lateral placement of the catheter. Transforaminal escape of contrast medium into the paravertebral area had occurred and anterior and posterior midline partitioning of the epidural space was obvious. All the usual measures to promote contralateral analgesia, except re-insertion of the catheter, had been tried without success.