Neuromuscular monitoring in intensive care patients: milliamperage requirements for supramaximal stimulation

Abstract

We investigated the effects of peripheral oedema on the supramaximal current required for neuromuscular monitoring of critically ill patients. We studied 32 sedated patients who had not needed a neuromuscular blocking drug. The presence of oedema over the volar aspect of both wrists was assessed by a blinded observer and graded (grade 0, no oedema; grade 1, mild oedema; grade 2, gross oedema). The supramaximal current was derived by applying an incrementally increasing current over the ulnar nerve and measuring the amplitude of the electromyographic (EMG) response of the first dorsal interosseous muscle. The supramaximal current was that current above which there was no significant increase in EMG amplitude. It was 40 mA in the absence of oedema. This current was significantly increased in the presence of grade 1 oedema (60 mA, Mann-Whitney test, P<0.01) and grade 2 oedema (82.5 mA, Mann-Whitney test, P<0.01). In the presence of oedema, the required supramaximal current decreased significantly after the application of pressure over the stimulating electrodes (Wilcoxon signed rank test, P<0.05). Supramaximal current in critically ill patients is increased in the presence of peripheral oedema. We recommend that nerve stimulators used for neuromuscular monitoring in the ICU are capable of delivering a stimulus current of at least 100 mA.

Electroencephalographic changes associated with non-invasive nociceptive stimulus in minimally anaesthetised dogs

“…This is a typical EEG response consistent with nociceptive response observed in many species of animals, such as rats, horses, lambs, calves, deer and dogs (Otto et al 1996, Murrell et al 2003, Johnson et al 2005a,b, Gibson et al 2007, Murrell et al 2007, Kongara et al 2010. Similar findings have also been reported in human patients with increasing strength of the stimuli as long as the magnitude of stimulus is kept below the critical supramaximal threshold (Harper et al 2001). A current of 50 to 60 mAs has been reported to be supramaximal in all patients during anaesthesia (Kopman and Lawson 1984).…”

“…A current of 50 to 60 mAs has been reported to be supramaximal in all patients during anaesthesia (Kopman and Lawson 1984). In a human study, median supramaximal current was 40 mAs in non-oedematous limbs compared to 60 mAs in Grade 1 edema and 82.5 mAs in Grade 2 edema (Harper et al 2001). The present results concur with findings in human studies and affirm that current between 40 and 60 mAs can be used for the noxious electric stimulus.…”

Neuromuscular electrical stimulation for preventing skeletal-muscle weakness and wasting in critically ill patients: a systematic review

“…It is conceivable that the benefits of NMES are greater for patients admitted to the ICU with respiratory complications (as suggested by the large effect sizes for patients with COPD) [47], or neurological complications, compared with patients with sepsis or trauma. For example, inflammation-mediated electrolyte changes and also edema may seriously affect conductivity and thus electrical current diffusion [52], which could lessen any systemic effect of NMES in these patient samples.…”

Monitorización intraoperatoria del bloqueo neuromuscular y la presión arterial con un solo dispositivo (TOF-Cuff): estudio comparativo con la mecanomiografía y la presión arterial invasiva

“…Cuando se aplica de forma continua, cada grupo de tren de estímulos se repite cada diez, quince, o veinte segundos para evitar debilitamiento 48,49 .…”

“…Con esta frecuencia bastan cuatro estimulaciones, ya que la fatiga muscular alcanza su grado máximo a partir de la cuarta respuesta 47 . Por tanto, en la estimulación nerviosa con TOF se aplican cuatro estímulos supramáximos con un intervalo de 0.5 segundos a una frecuencia de (2 Hz), con una duración individual de cada estímulo de 0.2 ms (Figura 8).Cuando se aplica de forma continua, cada grupo de tren de estímulos se repite cada diez, quince, o veinte segundos para evitar debilitamiento 48,49 .Cada estímulo del TOF provoca la contracción muscular, y la disminución de la respuesta aporta la base para la evaluación. El cociente entre la cuarta y la primera respuesta (T4/T1) se denomina relación del tren de cuatro (TOF-ratio) (Figura 8).…”