Intravenous Local Anaesthetic Compared with Intraperitoneal Local Anaesthetic in Abdominal Surgery: A Systematic Review

Introduction

Modern perioperative care strategies aim to optimise perioperative care by reducing the body’s stress response to surgery. A major facet of optimising an abdominal surgery analgesia programme is using a multimodal opioid sparing approach. Local anaesthetics have shown promise and there has been considerable research into the most effective route for their administration. This review aims to determine if there is a difference in analgesic efficacy between intraperitoneal local anaesthetic (IPLA) and intravenous local anaesthetic (IVLA).

Materials and Methodology

In concordance with the PRISMA statement, a literature search was conducted to identify randomised control trials that compared IVLA with IPLA in abdominal surgery. The primary outcomes of interest were opioid analgesia requirements and pain score assessed by visual analogue score. Data were extracted and entered into pre-designed electronic spreadsheets.

Results

This review has identified six papers that compared intravenous lignocaine to intraperitoneal lignocaine. This review showed significantly lower morphine consumption at 4 and 24 h in the intraperitoneal group. There was no significant difference in pain scores.

Conclusion

From the analysis of these studies, intraperitoneal local anaesthetic had an analgesic benefit over intravenous lignocaine with regard to decreased opioid consumption for abdominal surgery. Further research investigating IVL combined with intraperitoneal local anaesthetic is warranted.

     

Effects of forearm vs. leg submersion in work tolerance time in a hot environment while wearing firefighter protective clothing

This study compared physiological responses and total work tolerance time following forearm submersion (FS) or leg submersion (LS) in cool water, after performing work in a hot environment while wearing fire fighting protective clothing (FPC). Participants walked at 3.5 mph on a treadmill in a hot environment (WBGT 32.8 ± 0.9°C) until a rectal temperature (T(rec)) of 38.5°C was reached. Participants were then subjected to one of two peripheral cooling interventions, in a counterbalanced order. Forearms or lower legs were submerged in water (16.9 ± 0.8°C) for a total of 20 min, followed by a work tolerance trial. Results indicated no significant difference (p = 0.052) between work tolerance time (LS = 21.36 ± 5.35 min vs. FS = 16.27 ± 5.56 min). Similarly, there was no significant difference for T(rec) (p = 0.65), heart rate (HR) (p = 0.79), mean skin temperature (T(sk)) (p = 0.68), and rating of perceived exertion (RPE) (p = 0.54). However, LS ratings of thermal comfort (RTC) at Minute 14 (p = 0.03) were significantly lower for LS (10 ± 1) vs. FS (12 ± 1). Results indicate little difference between FS and LS for physiological measures. Despite a lack of statistical significance a 5-min (24%) increase was found during the work tolerance time following LS.     

Well-timed, brief inhibition can promote spiking: postinhibitory facilitation

Brief synaptic inhibition can overwhelm a nearly coincident suprathreshold excitatory input to preclude spike generation. Surprisingly, a brief inhibitory event that occurs in a favorable time window preceding an otherwise subthreshold excitation can facilitate spiking. Such postinhibitory facilitation (PIF) requires that the inhibition has a short (decay) time constant tauinh. The timescale ranges of tauinh and of the window (width and timing) for PIF depend on the rates of neuronal subthreshold dynamics. The mechanism for PIF is general, involving reduction by hyperpolarization of some excitability-suppressing factor that is partially recruited at rest. Here we illustrate and analyze PIF, experimentally and theoretically, using brain stem auditory neurons and a conductance-based five-variable model. In this auditory case, PIF timescales are in the sub- to few millisecond range and the primary mechanistic factor is a low-threshold potassium conductance gKLT. Competing dynamic influences create the favorable time window: hyperpolarization that moves V away from threshold and hyperexcitability resulting from reduced gKLT. A two-variable reduced model that retains the dynamics only of V and gKLT displays a similar time window. We analyze this model in the phase plane; its geometry has generic features. Further generalizing, we show that PIF behavior may occur even in a very reduced model with linear subthreshold dynamics, by using an integrate-and-fire model with an accommodating voltage-dependent threshold. Our analyses of PIF provide insights for fast inhibition's facilitatory effects in longer trains. Periodic subthreshold excitatory inputs can lead to firing, even one for one, if brief inhibitory inputs are interleaved within a range of favorable phase lags. The temporal specificity of inhibition's facilitating effect could play a role in temporal processing, in sensitivity to inhibitory and excitatory temporal patterning, in the auditory and other neural systems.     

Substance abuse and related diagnoses in early psychosis

Substance abuse seems to be common among those with early signs of evolving psychosis. This article seeks to determine the prevalence of substance abuse and substance use disorders (SUDs) and the association of abuse and SUD with vulnerability psychosis among a sample of first-degree relatives of schizophrenic patients (n = 70), help-seekers (n = 29), and control subjects (n = 34). The Structured Interview for Prodromal Symptoms (SIPS) 1.0 was used to define the vulnerability status and the Structured Clinical Interview for DSM-IV Axis I to diagnose the subjects. Data on various other measures, including premorbid adjustment, personality disorder symptoms, psychological distress, and abuse of substances, were collected. Those who were identified as vulnerable to psychosis reported significantly more lifetime alcohol abuse and had more commonly an SUD than controls. Substance use disorder, as well as alcohol and drug abuse, correlated significantly with personality disorder symptoms and current positive SIPS score and both types of abuse also with disorganization SIPS score. The odds ratio for having an SUD among those vulnerable to psychosis was 6.33 (95% confidence interval, 1.77-22.73). Early psychosis and substance abuse frequently occur together.     

Electrotonic structure of motoneurons in the spinal cord of the turtle: inferences for the mechanisms of bistability

Understanding how voltage-regulated channels and synaptic membrane conductances contribute to response properties of neurons requires reliable knowledge of the electrotonic structure of dendritic trees. A novel method based on weak DC field stimulation and the classical method based on current injection were used to obtain two independent estimates of the electrotonic structure of motoneurons in an in vitro preparation of the turtle spinal cord. DC field stimulation was also used to ensure that the passive membrane properties near the resting membrane potential were homogeneous. In two cells, the difference in electrotonic lengths estimated with the two methods in the same cell was 6 and 9%. The majority of dendritic branches terminated at a distance of 1 electrotonic unit from the recording site. The longest branches reached 2 lambda. In the third cell, the difference was 36%, demonstrating the need to use both methods, field stimulation and current injection, for reliable measurements of the electrotonical structure. Models of the reconstructed cells endowed with voltage-dependent conductances were used to explore generation mechanisms for the experimentally observed hysteresis in input current-voltage relation of bistable motoneurons. The results of modeling suggest that only some dendrites need to possess L-type calcium current to explain the hysteresis observed experimentally and that dendritic branches with different electrotonical lengths can be bistable. Independent bistable behavior in individual dendritic branches can make motoneurons complex processing units.