Slow Injection Group Research Articles

The influence of induction speed on the frontal (processed) EEG

The intravenous injection of the anaesthetic propofol is clinical routine to induce loss of responsiveness (LOR). However, there are only a few studies investigating the influence of the injection rate on the frontal electroencephalogram (EEG) during LOR. Therefore, we focused on changes of the frontal EEG especially during this period. We included 18 patients which were randomly assigned to a slow or fast induction group and recorded the frontal EEG. Based on this data, we calculated the power spectral density, the band powers and band ratios. To analyse the behaviour of processed EEG parameters we calculated the beta ratio, the spectral entropy, and the spectral edge frequency. Due to the prolonged induction period in the slow injection group we were able to distinguish loss of responsiveness to verbal command (LOvR) from loss of responsiveness to painful stimulus (LOpR) whereas in the fast induction group we could not. At LOpR, we observed a higher relative alpha and beta power in the slow induction group while the relative power in the delta range was lower than in the fast induction group. When concentrating on the slow induction group the increase in relative alpha power pre-LOpR and even before LOvR indicated that frontal EEG patterns, which have been suggested as an indicator of unconsciousness, can develop before LOR. Further, LOvR was best reflected by an increase of the alpha to delta ratio, and LOpR was indicated by a decrease of the beta to alpha ratio. These findings highlight the different spectral properties of the EEG at various levels of responsiveness and underline the influence of the propofol injection rate on the frontal EEG during induction of general anesthesia.

A New Suggested Strategy for Safe Injection of Ozurdex.

Ozurdex intravitreal injection is performed via a patented injection device. However, there is a common misconception among ophthalmologists regarding the relation between the speed of applicator button depression and the speed of pellet injection. Six dexamethasone intravitreal implants were injected into a calibrated ex vivo water bath. Three of the pellets were injected via rapid compression, whereas the other three implants were injected using a 3-second compression technique. The procedures were recorded using high-speed photography followed by calculation of pellet velocity and impact force. The mean impact velocity and force of the pellet insertion is significantly higher in the fast injection group compared to the slow injection group. By depressing the Ozurdex implant injector during a 3-second time interval, the impact force of the implant pellet is reduced by about 95%. This new technique will theoretically reduce the risk of retinal injury and vitreous hemorrhage from Ozurdex injections. [Ophthalmic Surg Lasers Imaging Retina. 2019;50:e23-e25.].

Comparison of priming versus slow injection for reducing etomidate-induced myoclonus: a randomized controlled study.

BackgroundEtomidate injection is often associated with myoclonus. Etomidate injection technique influences the incidence of myoclonus. This study was designed to clarify which of the two injection techniques—slow injection or priming with etomidate—is more effective in reducing myoclonus.MethodsThis prospective randomized controlled study was conducted on 189 surgical patients allocated to three study groups. Control group (Group C, n = 63) received 0.3 mg/kg etomidate (induction dose) over 20 s. Priming group (Group P, n = 63) received pretreatment with 0.03 mg/kg etomidate, followed after 1 min by an etomidate induction dose over 20 s. Slow injection group (Group S, n = 63) received etomidate (2 mg/ml) induction dose over 2 min. The patients were observed for occurrence and severity of myoclonus for 3 min from the start of injection of the induction dose.ResultsThe incidence of myoclonus in Group P (38/63 [60.3%], 95% CI: 48.0–71.5) was significantly lower than in Group C (53/63 [84.1%], 95% CI: 72.9–91.3, P = 0.003) and Group S (49/63 [77.8%], 95% CI: 66.0–86.4, P = 0.034). Myoclonus of moderate or severe grade occurred in significantly more patients in Group C (68.3%) than in Group P (36.5%, P < 0.001) and Group S (50.8%, P = 0.046), but the difference between Groups P and S was not significant (P = 0.106).ConclusionsPriming is more effective than slow injection in reducing the incidence of myoclonus, but their effects on the severity of myoclonus are comparable.

Comparison of priming versus slow injection for reducing etomidate-induced myoclonus: a randomized controlled study.

Etomidate injection is often associated with myoclonus. Etomidate injection technique influences the incidence of myoclonus. This study was designed to clarify which of the two injection techniques-slow injection or priming with etomidate-is more effective in reducing myoclonus. This prospective randomized controlled study was conducted on 189 surgical patients allocated to three study groups. Control group (Group C, n = 63) received 0.3 mg/kg etomidate (induction dose) over 20 s. Priming group (Group P, n = 63) received pretreatment with 0.03 mg/kg etomidate, followed after 1 min by an etomidate induction dose over 20 s. Slow injection group (Group S, n = 63) received etomidate (2 mg/ml) induction dose over 2 min. The patients were observed for occurrence and severity of myoclonus for 3 min from the start of injection of the induction dose. The incidence of myoclonus in Group P (38/63 patients [60.3%], 95% CI [48-71.5%]) was significantly lower than in Group C (53/63 patients [84.1%], 95% CI [72.9-91.3%], P = 0.003) and Group S (49/63 patients [77.8%], 95% CI [66-86.4%], P = 0.034). Myoclonus of moderate or severe grade occurred in significantly more patients in Group C (68.3%) than in Group P (36.5%, P < 0.001) and Group S (50.8%, P = 0.046), but the difference between Groups P and S was not significant (P = 0.106). Priming is more effective than slow injection in reducing the incidence of myoclonus, but their effects on the severity of myoclonus are comparable.

The effect of injection rate on etomidate-induced myoclonus

Background: Etomidate frequently causes myoclonus. Since the myoclonus is caused by a transient disequilibrium due to etomidate exposure in the CNS, we hypothesized that a slow rate of injection of the drug may decrease the incidence of myoclonus. We conducted a prospective randomized study to compare the effect of two different types of the etomidate injection rate on the incidence and severity of myoclonus. Methods: Fifty patients were randomly assigned to the fast-injection group (group F) or slow-injection group (group S): Group F patients received etomidate (0.3 mg/kg) over ten seconds. The same dose was administered over two minutes for group S patients. The response to the injection of etomidate was grade d on a four-point scale in a blinded manner. The time to loss of consciousness (LOC) was also recorded. Results: The incidence of myoclonus was significantly lower (P ＜ 0.001) in group S patients; 84% and 28% in group F and group S patients, respectively. The myoclonus was also significantly less severe in group S patients (P ＜ 0.001). The time to LOC was significantly longer in group S patients (106 ± 22 sec) than that of group F patients (49 ± 18 sec, P ＜ 0.001). Conclusions: With same dose, a slower rate of injection resulted in a lower incidence of myoclonus and can effectively reduce myoclonus without the use of a pretreatment agent. (Korean J Anesthesiol 2008; 55: 305～7)

Influence of the type and rate of subarachnoid fluid infusion on lethal neurogenic pulmonary edema in rats.

In patients who experience sudden death from spontaneous subarachnoid hemorrhage, more than 90% present with acute pulmonary edema. The underlying pathogenesis of this complication is poorly understood. In addition, the specific role of the extravasated blood products and the associated elevation in intracranial pressure leading to the systemic and pulmonary effects during subarachnoid hemorrhage are not well established. The authors tested a new model of acute and severe subarachnoid hemorrhage comparing fresh whole autologous blood (n = 20) with 5% albumin (n = 19) injected at two different rates (35 seconds versus 24 minutes) into the cisterna magna of anesthetized, mechanically ventilated rats. Cerebral and systemic hemodynamics and the corresponding pulmonary function were evaluated. The type of fluid injected had no influence on survival or hemodynamic and respiratory parameters. Rapid infusion of either blood or albumin (n = 14) produced an acute and transient rise in intracranial pressure (37.9 +/- 3.5 mm Hg) associated with systemic hypertension and increased cerebral perfusion pressure that was sustained in survivors but not in nonsurvivors. Slow infusion (n = 23) produced a more progressive increase in intracranial pressure to 31.2 +/- 7.1 mm Hg with a parallel and sustained increase of systemic blood pressure and preserved cerebral perfusion pressure in survivors, but produced a pattern of more severe hypertension followed by hypotension in nonsurvivors. Sixty-four percent of animals (rapid infusion) and 48% of animals (slow infusion) survived the challenge and presented no pulmonary alterations. In contrast, nonsurviving rats developed reduced lung compliance and gas exchange, an increased alveolar-arterial protein concentration ratio (0.36 +/- 0.02 versus 0.17 +/- 0.03 in survivors; P <.0001), and increased lung weight (5.7 +/- 0.3 g versus 2.0 +/- 0.1 g; P <.0001), demonstrating a fulminant increased permeability pulmonary edema, leading to death within one hour. These results indicate that the chosen rapid- and slow-injection rates resulted in a similar death rate of 50%. Mortality was similar for blood and albumin administration, pulmonary edema occurred in nonsurvivors in both the rapid- and slow-injection groups, and pulmonary edema is associated with more severe hypertension in the slow-injection group. Furthermore, these results suggest that the development of neurogenic pulmonary edema that is characterized by an acutely increased capillary permeability to proteins is independent of the degree of intracranial pressure increase or the type of fluid administrated.

Rate of injection through Whitacre needles affects distribution of spinal anaesthesia

A prospective, randomized, double-blind study was performed to investigate whether altering the rate of injection of local anaesthetic through a Whitacre needle had any effect on the spinal block achieved. Twenty patients scheduled for elective urological surgery under spinal anaesthesia received an injection of 3 ml of 0.5% plain bupivacaine either by hand (fast) over 10 s (18 ml min(-1)) or by infusion pump (slow) over 3 min (1 ml min(-1)). All patients were in the sitting position both during insertion of the spinal needle and for 3 min after the start of spinal injection, and they then changed to the supine position. The slow injection group achieved peak sensory block earlier, after a median interval of 20 (95% confidence interval 12.5-30) min vs 30 (22.5-45) min (P<0.05) for the fast group. The level of peak sensory block was similar: T3.5 (T2-T4.5) vs T4 (T1.5-T6.5). The time to lowest mean arterial pressure occurred earlier in the slow group, at 10 (8 to 18) vs 20 (15-31) min (P<0.05). Duration of the motor block was shorter in the slow group: 180 (152-242) vs 270 (225-300). We conclude that a slow spinal injection of plain bupivacaine results in a block of more rapid onset and recovery.

Influence of Injection Speed on the Subarachnoid Distribution of Isobaric Bupivacaine 0.5%

The purpose of this study was to compare the anesthetic characteristics after two radically different speeds of intrathecal injection of isobaric 0.5% bupivacaine during continuous spinal anesthesia. Forty consenting patients, undergoing hip surgery using continuous spinal anesthesia, were allocated randomly to two groups of 20 each according to the rate of injection of 2 mL (10 mg) of isobaric 0.5% bupivacaine: FI (fast injection = 2 mL during 2 to 3 s or approximately 0.75 mL/s) or SI (slow injection = 1 mL/min). No difference was observed between the two groups in terms of sensory and motor block or hemodynamic changes. However, the onset time to maximal sensory level was significantly shorter in the SI group (16 +/- 9 min vs. 24 +/- 6 min; P < 0.05). Those patients requiring reinjection entered the second part of the study (n = 23; 15 in the FI group and 8 in the SI group). Each of these remaining patients was used as his or her own proper control. Those in the FI group received a slow reinjection and those in the SI group received a fast reinjection which consisted in all cases of 10 mg (2 mL) of isobaric 0.5% bupivacaine. When looking at the anesthetic characteristics after reinjection, maximal sensory levels, as well as onset times, were very similar in both groups. At all times, the maximal sensory level obtained after reinjection was two dermatomes higher than after the initial injection. Duration of sensory block, which was calculated only in these 23 patients, was also comparable (126 +/- 44 min for FI and slow reinjection group vs 146 +/- 25 min for SI and fast reinjection group). In conclusion, regardless of the speed of injection, there are no differences in anesthetic characteristics of spinal anesthesia using isobaric 0.5% bupivacaine.

Injection rate: A factor in contrast reactions?

A prospective study comparing the frequency of contrast reactions by the rate of contrast injection is presented. One hundred patients undergoing excretion urography with meglumine diatriazoate (18%) and sodium diatriazoate (40%) mixture (Urografin 325) were randomised into slow (mean 0.975 ml/s) and rapid (mean 2.575 ml/s) injection groups. In the slow injection group 6 (12%) patients experienced a significant reaction as compared with 4 (8%) in the rapid injection group. There was no significant relationship between injection rate and contrast reaction (P greater than 0.1).

Effect of Injection Rate on Level and Duration of Hypobaric Spinal Anesthesia

The purpose of this study was to determine whether injection rate affects the spread of hypobaric spinal anesthesia. Hypobaric spinal anesthesia was performed on 20 patients for total hip arthroplasty. Dural puncture was performed with a 22-gauge Whitacre needle. All patients received 10 mg of hypobaric tetracaine with epinephrine. An electrically driven syringe pump was used to inject the anesthetic solution at either slow (250 sec) or fast (10 sec) rates. Ten patients received slow injections, and 10 received fast injections. Anesthetic levels, duration of anesthesia, and specific gravities of injectate and CSF were measured. Slow injection resulted in less spread of spinal anesthesia. Four-segment regression of anesthetic levels took significantly longer in the slow injection group. Local anesthetic mixtures used were consistently hypobaric compared to patient CSF. We conclude that slow injection of hypobaric tetracaine through a 22-gauge Whitacre needle produces lower levels of spinal anesthesia that tend to be of longer duration than levels resulting from fast injection.