Pretreatment with sedative-hypnotics, but not with nondepolarizing muscle relaxants, attenuates alfentanil-induced muscle rigidity

Study Objective: To evaluate and compare the efficacy of various pretreatment agents to attenuate or prevent opioid-induced muscle rigidity using a well-established, previously described clinical protocol.

Design: Prospective, controlled, single-blind, partially randomized study.

Setting: Large medical center.

Patients: ASA physical status I–III patients undergoing elective surgical procedures of at least 3 hours' duration.

Interventions: The effect of pretreatment with nondepolarizing muscle relaxants (atracurium 40μg/kg or metocurine 50,μg/kg), benzodiazepine agonists (diazepam 5 mg or midazolam 2.5 mg), or thiopental sodium 1 mg/kg on the increased muscle tone produced by alfentanil 175 ,μg/kg was compared with a control group (given no pretreatment).

Measurements and Main Results: Rigidity was assessed quantitatively by measuring the electromyographic activity of five muscle groups (biceps, intercostals, abdominals, quadriceps, and gastrocnemius). Rigidity also was rated qualitatively by attempts to initiate and maintain mask ventilation, attempts to flex an extremity, and the occurrence of myoclonic movements. Pretreatment with the two nondepolarizing muscle relaxants had no effect on the severe muscle rigidity produced by high-dose alfentanil. Whereas thiopental was only mildly effective, the benzodiazepines midazolam and diazepam significantly attenuated alfentanil rigidity (p < 0.05).

Conclusion: This study suggests that benzodiazepine pretreatment is frequently, but not always, effective in preventing opioid-induced muscle rigidity.     

The effect of muscle movement on the electroencephalogram during anesthesia with alfentanil

Using aperiodic analysis, we examined the impact on the electroencephalogram (EEG) of muscle activity from opiate-induced rigidity with alfentanil. We compared two groups of patients, one receiving alfentanil with neuromuscular blocking agents and the other group receiving no relaxants. The alfentanil-induced muscle rigidity exerted a noticeable effect on the EEG, with a moderate effect on total power at 1 Hz; a marked effect on the total number of waves, cumulative percent power at 3 Hz, and average power at 17 to 19 Hz; and a striking effect on F90, the frequency below which 90% of the power resides. The presence of electromyographic (EMG) noise in the EEG consistently altered the variables derived from the EEG, so that anesthetic depth appeared less than it actually was. This was true in spite of the fact that we gave slightly more alfentanil in the group not receiving a relaxant. Although the observed muscle activity was greater than that usually seen clinically, and may have differed qualitatively, the results do serve as a warning that muscle noise can interfere with the EEG. Currently, there is no computerized technique that will reject or account for this noise, and we must depend on observation to recognize the EMG patterns within the EEG, either with the raw recording or with a detailed analysis (such as aperiodic analysis), and to compensate for this noise if possible. Techniques that average the EEG or that present a single number have difficulty providing this information. These results do not detract from the usefulness of the EMG contained in EEG recordings as a supplementary or complementary indicator of anesthetic lightness.     

Abnormal developmental patterns of suck and swallow rhythms during feeding in preterm infants with bronchopulmonary dysplasia

Infants with bronchopulmonary dysplasia (BFD) often have difficulty achieving coordinated suckle feeding. To analyze rhythmic differences during feeding in infants with BPD we performed weekly studies of 14 infants with BPD (eight male, six female; postmenstrual age [PMA] 32.1 to 39.7 weeks); and a PMA-matched control group without BPD (n=20), from initiation of bottle feeding until discharge, with simultaneous digital recordings of pharyngeal and nipple (teat) pressure. Unlike the control group, there was no significant correlation between PMA and stability of suckle rhythm, aggregation of suckles or swallows into runs, or length of suckle runs. Comparing those infants >35 weeks' PMA, the group with BPD had significantly decreased stability of suckle rhythm (increased coefficient of variation of suckle-suckle intervals: 0.34, SE 0.02 vs 0.254, SE 0.014; p=0.003), decreased aggregation into suckle runs (71.1, SE 3.4% vs 85.4, SE 2%;p=0.001), and decreased length of suckle runs (7.2, SE 0.9 vs 13.1, SE 1.9 suckles/run; p=0.003). Percentage of swallows in runs was also decreased in the cohort with BPD (58, SE 3.8% vs 77.2, SE 3.5%; p<0.001), as was length of swallow run (5.3, SE 0.5 vs 10.7, SE 1.1;p<0.001). Thus, in infants with BPD, anticipated maturational patterns of suckle and swallow rhythms did not occur. Delay in attainment of stable suckle and swallow rhythms in preterm infants, especially after 35 weeks' PMA, may predict subsequent feeding and neurological problems.     

Changes in rhythmic suckle feeding patterns in term infants in the first month of life

To quantify parameters of rhythmic suckle feeding in healthy term infants and to assess developmental changes during the first month of life, we recorded pharyngeal and nipple pressure in 16 infants at 1 to 4 days of age and again at 1 month. Over the first month of life in term infants, sucks and swallows become more rapid and increasingly organized into runs. Suck rate increased from 55/minute in the immediate postnatal period to 70/minute by the end of the first month (p<0.001). The percentage of sucks in runs of > or =3 increased from 72.7% (SD 12.8) to 87.9% (SD 9.1; p=0.001). Average length of suck runs also increased over the first month. Swallow rate increased slightly by the end of the first month, from about 46 to 50/minute (p=0.019), as did percentage of swallows in runs (76.8%, SD 14.9 versus 54.6%, SD 19.2; p=0.002). Efficiency of feeding, as measured by volume of nutrient per suck (0.17, SD 0.08 versus 0.30, SD 0.11 cc/suck; p=0.008) and per swallow (0.23, SD 0.11 versus 0.44, SD 0.19 cc/swallow; p=0.002), almost doubled over the first month. The rhythmic stability of swallow-swallow, suck-suck, and suck-swallow dyadic interval, quantified using the coefficient of variation of the interval, was similar at the two age points, indicating that rhythmic stability of suck and swallow, individually and interactively, appears to be established by term. Percentage of sucks and swallows in 1:1 ratios (dyads), decreased from 78.8% (SD 20.1) shortly after birth to 57.5% (SD 25.8) at 1 month of age (p=0.002), demonstrating that the predominant 1:1 ratio of suck to swallow is more variable at 1 month, with the addition of ratios of 2:1, 3:1, and so on, and suggesting that infants gain the ability to adjust feeding patterns to improve efficiency. Knowledge of normal development in term infants provides a gold standard against which rhythmic patterns in preterm and other high-risk infants can be measured, and may allow earlier identification of infants at risk of neurodevelopmental delay and feeding disorders.     

Effect of Long-Term Angiotensin-Converting Enzyme Inhibitor Therapy on Arterial Oxygen Saturation in Patients With Mild to Moderate Heart Failure

Study Objective . To evaluate the effects of angiotensin-converting enzyme (ACE) inhibition on continuous pulse oximetry recordings of arterial oxygen saturation (SpO₂). Design . Open-label study. Setting . Cardiology clinics at two large teaching hospitals. Patients . Eight patients with New York Heart Association Functional Class (NYHA FC) II-III heart failure. Interventions . Patients were studied after an ACE inhibitor washout (baseline, B), and after 3 months following resumption of therapy (ACEI). Measurements and Main Results . Monitoring times for B and ACEI were approximately 22 hours. Reduction trends were observed for number (190 ± 170 vs 125 ± 67 B vs ACEI), magnitude (8.2 ± 1.4% vs 7.5 ± 1.8%), and duration (2.45 ± 2.8 vs 1.35 ± 0.8 min) of desaturations/monitoring period, and for nadir SpO₂/desaturation (88.1 ± 1.5% vs 89.9 ± 3.3%). The B desaturation index [(cumulative desaturation time/monitoring period time) × 100, a measure of hypoxic stress or burden] decreased from 19.4 ± 8.1% to 11.9 ± 8.1% at ACEI (p=0.024). Conclusion . Long-term ACE inhibitor therapy improves the profile of SpO₂ values over time in patients with NYHA FC II-III heart failure.     

Single center experience with percutaneous endovascular repair of superior vena cava syndrome

Objectives : To demonstrate short‐term effectiveness and long‐term efficacy of percutaneous transluminal angioplasty (PTA) with or without adjunctive therapy in treatment of superior vena cava syndrome (SVCS). Background : Recently, PTA with or without adjunctive therapy has evolved as first‐line therapy for SVCS. Despite growing evidence for PTA with or without adjunctive therapy, there are little data reflecting its short‐ and long‐term outcomes. Methods : We retrospectively reviewed 14 consecutive patients undergoing PTA with or without adjunctive therapy for SVCS, between July 2001 and September 2009. Results : A total of 14 patients (nine women; mean age, 49 ± 15 years) with SVCS underwent attempted PTA with or without adjunctive therapy. Causes of SVCS were indwelling catheters or pacemaker wires (n = 5), idiopathic (n = 5), thoracic outlet syndrome (n = 2), and cancer‐related thrombosis (n = 2). Obstruction of the SVC involved inflow branches in 86% of patients (n = 12). PTA with or without adjunctive therapy was attempted in all 14 patients and was angiographically successful in 93% (n = 13). PTA and stenting was performed in eight (57%) patients; three (21%) patients had PTA with thrombectomy/thrombolysis; one (7%) patient had PTA alone; and one (7%) patient had thrombectomy/thrombolysis alone. Symptom relief was seen in 86% (n = 12), and initial patency was 90%. There were no procedural complications. Mean follow‐up was 12 months, and no deaths were reported. In the 11 (79%) patients with follow‐up imaging, nine (82%) patients showed patency and two (18%) had residual symptoms, with one patient undergoing surgery. Conclusions : PTA with adjunctive endovascular stent therapy for SVCS is safe and effective at giving both rapid and sustained symptom relief. © 2011 Wiley‐Liss, Inc.     

An electroencephalographic comparison of alfentanil with other narcotics and with thiopental

Using aperiodic analysis, we compared the EEC produced by alfentanil with the EEGs produced by two other opiates—fentanyl and sufentanil—on the one hand and with the EEG produced by a barbiturate—thiopental—on the other hand. Alfentanil and thiopental were injected over 1 minute: fentanyl and sufentanil were injected over 10 to 15 minutes. From the aperiodic analysis we derived up to seven single-number variables computed over 30- or 60-second epochs. All the opiates induced EEGs that were qualitatively similar to each other, although the maximum or minimum values tended to be greater and the time course more rapid with alfentanil than with the other two opiates. This finding may have been related to the fact that we injected relatively more alfentanil and administered it more rapidly. The EEGs produced by alfentanil and thiopental differed markedly, both qualitatively and quantitatively. The total power at 1 Hz and cumulative power at 3 Hz went to higher peak values with alfentanil, the latter tending to decrease with thiopental. The total number ot waves per epoch went to lower peak values with alfentanil; there was little change with thiopental. The frequency below which 90% ot the power resides went to considerably lower peak values with alfentanil than with thiopental. Finally, total power at 10 to 12 Hz (alpha waves; and average power at 17 to 19 Hz (beta waves) went to very high peak values with thiopental, but decreased with alfentanil. In spite ot differences in the opiate studies in the timing ot injection and the relative amount ot drug injected, the variables that proved useful in their response to fentanyl and sutentanil also proved useful with altentanil. In contrast, almost all variables showed a difference in response between alfentanil and thiopental. Supported in part by Janssen Pharmaceutics, Inc. Pisacataway, NJ, and by Diatek Corporation, and the Veterans Administration Medical Center, San Diego, CA.     

Noninvasive continuous blood pressure measurement from the finger: Optimal measurement conditions and factors affecting reliability

We recorded finger arterial blood pressure (FINAP) in 50 male patients during various types of surgical operations. Three different types of cuffs were used on four fingers of each patient. Measurements were made by the arterial volume-clamp method of Penaz. The FINAP measurements were compared with pressure data obtained ipsilaterally from a radial artery catheter-transducer system (intraarterial pressure [IAP]) to find optimal recording conditions and to document factors affecting FINAP readings. The thumb, with a specially designed cuff, gave the most accurate results. The mean FINAP- IAP difference for the thumb was –4.8 mm Hg for systolic pressure, 1.49 mm Hg for diastolic pressure, and 0.29 mm Hg for mean pressure. The differences were statistically significant for systolic and diastolic pressure but not for mean pressure. The regression slope for thumb systolic FINAP/IAP was 0.979, that for thumb diastolic FINAP/IAP was 0.963, and that for mean thumb FINAP/IAP was 0.996, whereas the intercepts were 7.499 for systolic pressure, 0.802 for diastolic pressure, and 0.083 for mean pressure. The correlation coefficients were 0.945 (systolic), 0.884 (diastolic), and 0.949 (mean). The correlation coefficients with the other fingers ranged from 0.502 to 0.922 for systolic pressure, 0.757 to 0.932 for diastolic pressure, and 0.767 to 0.892 for mean pressure. The slopes for the various finger-cuff combinations ranged from 0.537 to 0.996, and the intercepts ranged from 0.083 to 32.387 from mean pressure. In 3 patients (6%) the FINAP measurement was not possible because of insufficient peripheral circulation. In 9 other patients (18%) the FINAP measurements were not accurate during some periods of time.In 5 of those 9 patients the difficulties were related to arterial cannulation and began immediately after cannulation. In 1 of those 5 patients the FINAP subsequently decreased dramatically after the onset of phenylephrine infusion because of peripheral vasoconstriction and diminished blood flow. In the 4 other patients the FINAP readings were accurate at the beginning of anesthesia but later decreased out of proportion to changes in IAP. These periods were associated with one-lung ventilation. The FINAP accurately reflects systemic arterial pressure. Measurements from the thumb fitted with a specially designed cuff approximate IAP best. Factors affecting peripheral circulation must be taken into consideration when this device is used in the monitoring of FINAP.