Power output and blood flow were determined in dogs for four muscles (gastrocnemius, latissimus dorsi, rectus abdominis, and triceps) to determine effects of choice of muscle, tetany or twitch rates, force loading of the muscle, and blood flow on muscle power output. Total power for a 20‐Kg dog was greatest for triceps at 0.77 watts (W) and least for rectus at 0.22 W; power per gram was greatest for gastrocnemius at 5.77 mW/g. Muscle perfusion of latissimus and rectus is greatly decreased by overstretching of the muscle. Overstretching also produces severe, persistent, power loss in latissimus and rectus muscles. Gastrocnemius and triceps tolerate stretching much better. We conclude that power can be improved without causing muscle fatigue by choice of muscle, choice of electrical stimulation parameters, linear geometry for contraction of the muscle, and matching the force load to each individual muscle.

A 15-year-old boy with cerebral palsy and epilepsy presented for a posterior spinal fusion as part of staged repair of thoracolumbar scoliosis. Total intravenous anaesthesia was induced and maintained with propofol, remifentanil and ketamine. Following prone positioning, cervical traction was applied. Polyuria developed intra-operatively, from 4 to 18 ml.kg À1 .h À1. There was a corresponding rise in plasma sodium concentration from 132 to 145 mmol.l À1. Haemodynamic stability was maintained with boluses of Hartmann's solution and a noradrenaline infusion. Given the possibility of diabetes insipidus due to reduced cerebral perfusion pressure, the cervical traction was removed. This initially showed a good response with a transient reduction in polyuria to 3 ml.kg À1 .h À1 before rising to 8 ml.kg À1 .h À1. Subsequently, a vasopressin infusion was started with normalisation of diuresis and plasma sodium concentration by the end of surgery. Diabetes insipidus is an endocrine disorder related to lack of production or insensitivity to vasopressin. In the peri-operative period, it is mainly associated with pituitary surgery and rarely with spinal surgery. To the authors' knowledge, this is only the second report of diabetes insipidus associated with staged scoliosis surgery. Cervical traction should be considered as a potential cause of intra-operative diabetes insipidus.

Spinal muscular atrophy is a neuromuscular disorder with degeneration of spinal motor neurons. Type I is a severe variant that was recently shown to be amenable to treatment with the antisense oligonucleotide nusinersen. As a result of increased life expectancy with this treatment, more children with spinal muscular atrophy type I are presenting for spinal correction surgery. In this case series, we present four such patients who underwent spinal surgery at our institution over the course of one year. Pre-operative assessment showed evidence of reduced respiratory function requiring nocturnal non-invasive ventilation in all four patients. A difficult airway was encountered in two of the four patients. Postoperative complications were ubiquitous and included CSF leak, poor wound healing, metal frame exposure, frame instability and wound infection. There were no postoperative respiratory complications and all four children returned to their respiratory baseline postoperatively. All patients underwent successful lumbar puncture and intrathecal nusinersen injection following their spinal surgeries. Given the risk of complications and prolonged recovery following spinal surgery, a detailed family discussion is advisable.