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Biomedical subjects

N J Harper

Publications and source records attributed to N J Harper.

At least 19 recordsLinked to original sources
PubMed2001

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

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.

Critical Care↗
PubMed2000

Is tourniquet use necessary for knee arthroscopy?

PURPOSE: With several studies identifying the tourniquet as a factor for increased risk of complications in knee arthroscopy, we wished to identify whether its use is necessary. TYPE OF STUDY: We performed a prospective randomized trial on 109 patients undergoing knee arthroscopy. MATERIALS AND METHODS: All patients had a tourniquet placed on the thigh and were assigned to either have it inflated or not inflated. Personal information, operative details, postoperative pain scores, analgesic requirements, and complications were recorded. RESULTS: The 2 groups were comparable. There was no significant difference between the 2 groups with respect to operative view, duration of operation, pain scores, analgesic requirements, or complications. The tourniquet required intraoperative inflation in 4 patients assigned not to have it inflated; in 1 patient, the tourniquet made no difference to the operative view. CONCLUSIONS: Many orthopaedic units continue to use a tourniquet routinely for knee arthroscopy, probably in the belief that a clear operative view can only be achieved with one. However, the findings in our trial indicate that knee arthroscopy may be performed adequately without the use of a tourniquet. Therefore, we recommend that its routine use for this procedure is discontinued.

Adolescent↗
PubMed1999

Residual neuromuscular block caused by pancuronium after cardiac surgery.

We studied 20 adult patients undergoing cardiac surgery. All received pancuronium as the sole neuromuscular blocking drug and no reversal agent was used. In the postoperative intensive care unit, mechanical ventilation was continued and patients were sedated with an infusion of propofol. Neuromuscular block was measured electromyographically at appropriate intervals until the train-of-four ratio (TOF) reached 0.8. At the time when the propofol infusion would normally be discontinued, 13 patients (65%) demonstrated a TOF of less than 0.8 (group median 0.23, interquartile range 0.11-0.6). Subsequently, the median time to achieve a TOF of 0.8 was 2 h 10 min (interquartile range 1 h-2 h 25 min). We found that if pancuronium was used during cardiac surgery, a significant proportion of patients remained partially paralysed when they would normally be allowed to emerge from anaesthesia in the ICU.

Aged↗
PubMed1998

The management of metformin overdose.

Only two cases of deliberate self-poisoning with metformin have been described in the literature. We report the management of three cases, all of which presented with severe lactic acidosis. Two cases had a fatal outcome. The options for treatment and previous cases reported in the literature are reviewed. Recommendations for the management of metformin overdose include early recognition, intensive support of the cardiovascular system, the correction of metabolic acidosis and the maintenance of body temperature. The use of venovenous haemofiltration against a non-lactate containing fluid may improve outcome when sodium bicarbonate alone fails to reverse severe systemic acidosis.

Acidosis, Lactic↗
PubMed1998

Neuromuscular monitoring by intensive care nurses: comparison of acceleromyography and tactile assessment.

We have compared tactile assessment of the train-of-four (TOF) count and TOF ratio by nursing staff, with measurements made by a new acceleromyographic monitor, the TOF-Watch. We assessed neuromuscular block in 30 sedated intensive care patients receiving a continuous infusion of atracurium. Five nurses made a tactile assessment of neuromuscular block in each patient within a 5-min period. Each assessment was paired with a blinded TOF-Watch measurement. The nurses were accurate in assessing twitch count in 55% of measurements and they tended to overestimate the degree of block using tactile assessment of TOF ratio.

Adult↗
PubMed1997

A comparison of cisatracurium (51W89) and atracurium by infusion in critically ill patients.

OBJECTIVE: To evaluate and compare the safety and efficacy of cisatracurium (51W89) and atracurium administered by continuous infusion to critically ill patients requiring neuromuscular blocking agents to facilitate mechanical ventilation. DESIGN: Open, randomized, multicenter study of patients receiving cisatracurium or atracurium infusion to facilitate mechanical ventilation. SETTING: Five university teaching hospital intensive care units in the United Kingdom. PATIENTS: Sixty-one adult patients requiring neuromuscular blocking agents to facilitate mechanical ventilation. INTERVENTIONS: Bolus doses followed by continuous infusions of cisatracurium or atracurium were administered. Onset, maintenance, and recovery of neuromuscular blockade were measured, using transcutaneous ulnar nerve stimulation and an accelerometer. MEASUREMENTS AND MAIN RESULTS: Forty patients received cisatracurium (mean duration 48.1 +/- 4.2 [SEM] hrs), and 21 patients received atracurium (mean duration 46.1 +/- 5.8 hrs). The infusion rate for patients receiving cisatracurium was 3.1 +/- 0.2 microg/kg/min, and for patients receiving atracurium 10.4 +/- 0.9 microg/kg/min. There were no significant differences in mean times to 70% recovery of Train-of-Four ratio (cisatracurium 60 mins, atracurium 57 mins), although there was considerable interpatient variation (20 to 175 mins with cisatracurium vs. 35 to 85 mins with atracurium). One patient who received cisatracurium exhibited intermittent bronchospasm during and after the study period. CONCLUSIONS: Cisatracurium, an isomer of atracurium, appears to be a suitable agent for providing muscle relaxation in critically ill patients.

APACHE↗
PubMed1996

The infusion requirements and recovery characteristics of cisatracurium or atracurium in intensive care patients.

OBJECTIVE: To investigate the infusion requirements and recovery characteristics of cisatracurium compared with atracurium when both are administered by prolonged continuous infusion. DESIGN: A prospective, randomised, single-blind study. SETTINGS: The Intensive Care Unit of the Manchester Royal Infirmary. PATIENTS: 20 patients requiring a continuous infusion of a neuromuscular blocking agent to facilitate mechanical ventilation. 12 patients received cisatracurium and 8 received atracurium. INTERVENTIONS: Cisatracurium or atracurium was administered by continuous infusion for a minimum of 24 h. The level of neuromuscular blockade was measured by recording the train-of-four responses using acceleromyography, the aim being to maintain 1-2 twitch responses of the adductor pollicis. At the end of the infusion period, the train-of-four was recorded until the ratio was greater than 0.7. MEASUREMENTS AND RESULTS: The mean infusion rate of cisatracurium was 0.23 mg kg-1 h-1, compared to 0.62 mg kg-1 h-1. No time-related increase in infusion requirements was seen for either drug. The mean recovery time to a train-of-four ratio greater than 0.7 was the same (46 min). There was no correlation between recovery time and age, duration of infusion or mean infusion rate. CONCLUSIONS: Cisatracurium provides a satisfactory level of neuromuscular blockade in adult ICU patients at approximately one-third the infusion rate of atracurium and with a similar recovery time.

Adult↗
PubMed1995

The clinical pharmacology of doxacurium in young adults and in elderly patients.

Neuromuscular blockade induced by doxacurium 30 micrograms.kg-1 was compared in 21 young (18-55 years) and 17 elderly (65-85 years) patients. Anaesthesia was induced with thiopentone and maintained with fentanyl, nitrous oxide in oxygen and isoflurane. Neuromuscular blockade was measured electromyographically (Datex Relaxograph) at the adductor pollicis using train-of-four stimuli at 20 s intervals. The depth of maximum neuromuscular blockade was similar in young and elderly patients (median 100% compared to 96%). However, the onset was significantly slower in the elderly: their mean (SD) time to 90% suppression of the first response of the train-of-four was 7.7 (1.8) min compared to 5.7 (1.7) min in the young (p = 0.002). Four min after doxacurium, the conditions for tracheal intubation were significantly poorer in the elderly (p < 0.001). Mean (SD) recovery of first response of the train-of-four to 25% of control was unaffected by age: young 79.0 (41.6) min; elderly 66.2 (32.1) min (p > 0.05). When the first response had reached 25% of control, neuromuscular blockade was antagonised with neostigmine 60 micrograms.kg-1. The mean time to first response to 90% of control was similar in the young and the elderly patients (9.1 min compared to 10.4 min). Recovery of the train-of-four ratio to 0.7 was significantly slower in the elderly: mean (SD) 17.1 (10.6) min compared to 10.1 (7.0) min (p = 0.03). Doxacurium was associated with clinically insignificant haemodynamic changes in both groups.

Adolescent↗
PubMed1994

Optimum dose of neostigmine at two levels of atracurium-induced neuromuscular block.

There is controversy about the optimum dose of neostigmine for antagonizing neuromuscular block. We have studied 57 patients undergoing gynaecological surgery to establish a dose-response relationship when neostigmine was given to antagonize atracurium-induced block. Anaesthesia was induced with thiopentone and fentanyl and maintained with nitrous oxide and enflurane in oxygen and neuromuscular block was produced with a bolus of atracurium 0.5 mg kg-1. At the time of antagonism of block, three groups received neostigmine 20, 40 or 80 micrograms kg-1 at 5-10% recovery of the compound muscle action potential of the adductor pollicis (profound block) and three groups received one of these doses at 40-50% neuromuscular recovery (light block). At profound block, antagonism was prolonged by reducing the dose of neostigmine from 40 micrograms kg-1 to 20 micrograms kg-1, but not shortened by increasing the dose from 40 micrograms kg-1 to 80 micrograms kg-1. At light block, there was no significant difference between the three groups in the time taken to reach a train-of-four ratio of 0.7. There was little benefit in increasing the dose of neostigmine from 40 micrograms kg-1 to 80 micrograms kg-1 when antagonizing profound neuromuscular block. When light block was antagonized, neostigmine 20 micrograms kg-1 was the optimum dose. We suggest that smaller doses of neostigmine than are given commonly produce adequate antagonism of atracurium-induced neuromuscular block.

Adult↗
PubMed1994

Monitoring neuromuscular block by acceleromyography: comparison of the Mini-Accelograph with the Myograph 2000.

The precision of the compact Mini-Accelograph (M-A) was compared with the Myograph 2000 (MYO). Neuromuscular block resulting from atracurium was measured simultaneously by the MYO and the M-A applied to contralateral thumbs. During onset, the M-A frequently underestimated the extent of block (maximal at approximately 50% twitch depression). The M-A control train-of-four (TOF) ratio was characteristically > 1.0 and remained greater than the MYO ratio during the onset of atracurium. During recovery, the difference between the MYO and the M-A was maximal at approximately 50% twitch depression, but the M-A frequently overestimated the extent of block. The mean differences between the MYO and the M-A were small in respect of the recovery index (RI) and the TOF. However, the limits of agreement were unacceptably wide for both TOF and RI. When the MYO TOF was 0.7, the corresponding M-A TOF varied between 0.4 and 1.0. The M-A was more susceptible to drift than the MYO.

Adult↗
PubMed1994

Intermuscular bupivacaine infusion for control of pain after renal surgery: a preliminary report.

OBJECTIVE: To assess the value of continuous bupivacaine wound infusion for post-operative pain relief after renal surgery. PATIENTS AND METHODS: The analgesic efficacy of continuous intermuscular wound infusion with 0.25% bupivacaine was studied in 10 patients (four men, six women), with a mean age of 47.5 years (range 25-71) and a mean weight of 71.2 kg (range 44-99), after renal surgery in a single-blind randomized trial. The results were compared with those of an age- and weight-matched control group of 10 patients (five men, five women) with a mean age of 47.7 years (range 27-73) and a mean weight of 67.3 kg (range 51-85). Post-operative pain was studied objectively by assessing individual patient's morphine requirements administered via a patient controlled analgesia system, and subjectively with pain scores. Patient mobility was assessed by ward nursing staff using mobility score charts. RESULTS: There was a lower demand for post-operative analgesia in the bupivacaine group compared with the control. Although there was no significant difference in the pain scores between the two groups, the bupivacaine group was significantly more mobile than the control group after surgery. There was no significant difference in the mean post-operative hospital stay between the two groups. CONCLUSION: Continuous intermuscular bupivacaine wound infusion is a simple and safe procedure which lowers the patients' post-operative analgesic requirements, allows for earlier mobility and may promote more rapid discharge from hospital.

Adult↗
PubMed1993

Suxamethonium and atracurium: sequential and simultaneous administration.

The interaction between suxamethonium and atracurium was investigated during anaesthesia with thiopentone, fentanyl, enflurane and nitrous oxide in oxygen with controlled ventilation. Electromyographic data (Relaxograph, Datex) from 30 patients in three, equal groups were analyzed. Group 1 received atracurium 0.23 mg kg-1. Group 2 received suxamethonium 1 mg kg-1 followed by atracurium 0.23 mg kg-1 when the EMG had recovered to 20% of its control value: a sequence intended to be representative of clinical practice. Group 3 received suxamethonium 1 mg kg-1 and atracurium 0.23 mg kg-1 in rapid succession. Plasma cholinesterase concentrations and Dibucaine and fluoride numbers were within normal limits in all patients. Suxamethonium given for endotracheal intubation (group 2) neither potentiated the subsequent atracurium blockade nor delayed spontaneous recovery. When suxamethonium and atracurium were given in rapid succession (group 3), the duration of suxamethonium blockade was reduced considerably but the recovery from the atracurium component of the blockade was not significantly different from groups 1 and 2. Although the intubation score at 60s was no worse in group 3, the duration of profound blockade suitable for intubation was reduced to such an extent that the simultaneous administration of suxamethonium and atracurium cannot be recommended in clinical practice when there is a requirement for rapid endotracheal intubation.

Adult↗
PubMed1991

Non-invasive measurement of cardiac output during induction of anaesthesia and tracheal intubation: thiopentone and propofol compared.

We have investigated the haemodynamic changes in response to induction of anaesthesia and tracheal intubation in patients who received either thiopentone 5 mg kg-1 or propofol 3 mg kg-1 followed by atracurium 0.5 mg kg-1 and fentanyl 1.5 micrograms kg-1. Anaesthesia was maintained with 0.6% enflurane and 50% nitrous oxide in oxygen with assisted ventilation. Cardiac output and heart rate (HR) were monitored continuously with a transthoracic impedence monitor. Mean HR did not change after induction in each group, but increased after tracheal intubation in both groups (P less than 0.01). Mean cardiac index (CI) decreased after induction (P less than 0.05) and decreased further after tracheal intubation in both groups (P less than 0.05). There was no difference between the two groups with respect to changes in CI and HR. Mean arterial pressure (MAP) and systemic vascular resistance (SVR) did not change significantly after induction in the thiopentone group. Both variables increased from preinduction values 1 min after tracheal intubation (P less than 0.001). In contrast, both MAP and SVR decreased after induction in the propofol group (P less than 0.001) and did not differ from preinduction values 1 min after tracheal intubation. MAP and SVR were greater in the thiopentone group compared with the propofol group after induction and tracheal intubation (P less than 0.01).

Adult↗
PubMed1990

Pain on injection of propofol. Methods of alleviation.

A controlled randomised double-blind design was used to study the effect of lignocaine on the pain produced by intravenous injection of propofol. Patients received a 2-ml pretreatment solution with temporary venous occlusion, followed by an induction solution. One hundred and three patients were assigned to one of five groups: saline pretreatment, followed by induction with propofol plus saline 2 ml; lignocaine 20 mg pretreatment, followed by induction with propofol plus saline 2 ml; lignocaine 40 mg pretreatment, followed by induction with propofol plus saline 2 ml; saline pretreatment, followed by induction with propofol plus lignocaine 20 mg; or saline pretreatment, followed by induction with propofol plus lignocaine 40 mg. Pain was reduced significantly in all groups in which lignocaine was used and a dose of 40 mg was more effective than 20 mg. There were no significant differences in the incidence of pain among the groups which received lignocaine as pretreatment and the groups which received lignocaine mixed with propofol. Sixty-eight percent of patients who experienced pain or discomfort recalled it in the postoperative period.

Double-Blind Method↗