H. Berg

Bio: H. Berg is an academic researcher from Copenhagen University Hospital. The author has contributed to research in topics: Neuromuscular transmission & Neuromuscular monitoring. The author has an hindex of 5, co-authored 5 publications receiving 716 citations.

Residual neuromuscular block is a risk factor for postoperative pulmonary complications: A prospective, randomised, and blinded study of postoperative pulmonary complications after atracurium, vecuronium and pancuronium

Abstract: Background: After anaesthesia involving pancuronium a high incidence of both residual neuromuscular block and postoperative pulmonary complications (POPC) has been reported. The aim of this study was to compare the incidence of POPC following the use of pancuronium, atracurium, and vecuronium, and to examine the effect of residual neuromuscular block on the incidence of POPC. Methods: A total of 691 adult patients undergoing abdominal, gynaecological, or orthopaedic surgery under general anaesthesia were randomised to receive either pancuronium, atracurium, or vecuronium. Perioperatively, the response to train-of-four (TOF) nerve stimulation was evaluated manually. Post-operatively, the TOF ratios were measured mechanomyograph-ically, and through a 6-day follow-up the patients were examined for pulmonary complications. Results: The incidence of residual block, defined as a TOF ratio <0.7, was significantly higher in the pancuronium group (59/226: 26%) than in the atracurium/vecuronium groups (24/450: 5.3%). In the pancuronium group, significantly more patients with residual block developed POPC (10/59: 16.9%) as compared to patients without residual block (8/167 4.8%). In the atracurium/vecuronium groups, the incidence of POPC was not significantly different in patients with (1/24: 4.2%) or without (23/426: 5.4%) residual block. Multiple regression analysis indicated that abdominal surgery, age, long-lasting surgery, and a TOF ratio<0.7 following the use of pancuronium were potential risk factors for the development of POPC. Conclusion: Postoperative residual block caused by pancuronium is a significant risk factor for development of POPC.

Tactile evaluation of the response to double burst stimulation decreases, but does not eliminate, the problem of postoperative residual paralysis.

Abstract: Background: Routine perioperative monitoring with accelero-myography might prevent residual block, whereas routine tactile evaluation of the response to train-of-four (TOF) nerve stimulation does not. The purpose of this prospective, randomised and blinded study was to evaluate the effect of manual evaluation of the response to double burst stimulation (DBS3.3) upon the incidence of residual block. Methods: Sixty adult patients scheduled for elective abdominal surgery were included in the study. Pancuronium 0.08 to 0.1 mg kg−1 was given for relaxation and tracheal intubation. For maintenance of neuromuscular block, pancuronium 1–2 mg was administered. The patients were randomly allocated into two groups. In group DBS (double burst stimulation) the degree of block during anaesthesia was assessed by manual evaluation of the response to TOF nerve stimulation. During reversal, when no fade was detectable in the TOF response, the stimulation pattern was changed to DBS3.3. The trachea was extubated when the anaesthetist judged the neuromuscular function to have recovered adequately and no fade in the DBS3.3 response could be felt. In group CC (clinical criteria) patients were managed without the use of a nerve stimulator, and the level of neuromuscular block and reversal were evaluated solely on the basis of clinical criteria. In both groups, the TOF ratio was measured by mechanomyography immediately after tracheal extubation. Also, the ability to sustain head lift for 5 s, to protrude the tongue, to open the eyes, and to lift one arm to the opposite shoulder were tested. Results: The TOF ratio, as measured immediately after tracheal extubation, was significantly lower in group CC than in group DBS (means: 0.68 and 0.78, respectively), and the incidence of residual neuromuscular block defined as a TOF ratio <0.7 was significantly higher in group CC than in group DBS (57 and 24%, respectively). The time from the first TOF measurement until the TOF ratio reached 0.8 was significantly longer in group CC than in group DBS (means: 11.5 and 6.2 min, respectively). No significant differences between the two groups of patients were found in duration of anaesthesia, in times from end of surgery to injection of neostigmine, tracheal extubation or TOF ratio 0.8, in dose of pancuronium, or in any other postoperative variable. Conclusion: Routine perioperative manual evaluation of the responses to TOF and DBS3.3 decreased the incidence and the degree of residual block following the use of pancuronium. It did not, however, exclude clinically significant residual paralysis, nor did it influence the amount of pancuronium used during the operation, the duration of anaesthesia or the time from end of surgery to tracheal extubation or to sufficient recovery of neuromuscular function (TOF=0.8).

Acceleromyography of the orbicularis oculi muscle II: comparing the orbicularis oculi and adductor pollicis muscles

Abstract: Background: The orbicularis oculi (OO) muscle has been recommended for neuromuscular monitoring when the adductor pollicis (AP) muscle is not available. We investigated whether neuromuscular block could be measured reliably from the orbital part of the OO muscle by the use of acceleromyography. Methods: During propofol, fentanyl, and alfentanil anaesthesia two TOF-Guards® (Organon Teknika NV, Boxtel, the Netherlands) with acceleration transducers placed on the distal phalanx of the thumb and over the middle of the eyebrow, respectively, were used to measure neuromuscular block simultaneously in 23 patients during vecuronium-induced and neostigmine-antagonized neuromuscular block. For both muscles, the simultaneously recorded first response (T1) in the train-of-four (TOF) and TOF-ratio were measured both during onset and recovery of the block. Furthermore, both the AP muscle T1 and TOF-ratio responses were plotted against 10% intervals of the OO muscle responses during onset and recovery, respectively. Results: The orbicularis oculi muscle had a shorter latency and a faster recovery to TOF-ratio 0.80 compared with the AP muscle. During onset and recovery, pronounced variations of the AP muscle T1 and TOF-ratio responses were observed when compared with the OO muscle. Conclusion: A significant clinical disagreement exists between the degree of paralysis measured at the OO and the AP muscles. It is impossible to obtain a reasonable estimate of the degree of block at the AP muscle when the block is measured from the OO muscle with acceleromyography. If used, there is substantial risk of overlooking a residual block, and adequate recovery of the block should be confirmed by a final AP muscle measurement.

Acceleromyography of the orbicularis oculi muscle I: significance of the electrode position.

Abstract: Background: This study aimed to establish the best position of the stimulating electrodes for facial nerve stimulation during acceleromyographic monitoring from the orbital part of the orbicularis oculi muscle. Methods: In 59 anaesthetised patients, an acceleration transducer was positioned over the middle of the eyebrow. In 47 patients, supramaximal train-of-four (TOF) stimulation was established for four electrode pairs with different positions along the facial nerve and behind the ear. The electrode pair with the lowest, the intermediate, and the highest supramaximal stimulating current based on first response (T1) in TOF was found in each patient. A possible response from direct muscle stimulation was evaluated during complete vecuronium block. In 12 patients, supramaximal stimulation was established using a stimulation sequence different from the one used in the first part of the study. Results: The best positions for the stimulating electrodes were either with both electrodes just lateral to the eye, or with one electrode lateral to the eye and one in front of the ear. In most patients, supramaximal stimulation was obtained at these positions at 20–60 mA. However, in 10–21% of the patients, supramaximal stimulation could not be obtained. During complete block, 1–4 responses with a twitch height of 3–11% were recorded in 80% of the patients. Conclusion: The best placements of the stimulation electrodes are either just lateral to the eye or along the zygomatic arch. However, supramaximal stimulation may often not be obtainable, and activation of other facial muscles may be a confounding factor that may impede correct evaluation of the degree of neuromuscular block.

The pharmacodynamics and pharmacokinetics of mivacurium in children

Abstract: Background: In children, onset time and duration of action of mivacurium are shorter than in adults. Some suggest that this is due to differences in plasma cholinesterase (pChe), whereas others indicate that there is no difference. The purpose of this study was to evaluate the pharmacodynamics and pharmacokinetics of mivacurium in phenotypically normal children aged 3–6 and 10–14 years old, respectively. Methods: Ten children aged 3–6 years and 10 children aged 10–14 years were studied during halothane anaesthesia. Before induction of anaesthesia, a bloodsample was drawn to measure the pChe activity and phenotype. The neuromuscular block was monitored at the thumb using train-of-four (TOF) nerve stimulation every 12 s and mechanomyography. The times to different levels of neuromuscular recovery following mivacurium 0.2 mg/kg were recorded. The concentrations in venous blood of the three isomers and the metabolites of mivacurium were measured. Results: No statistically significant difference was found in pChe activity or in the pharmacodynamics of mivacurium. The onset time was 1.4 min (0.8–1.9) median (range) and 1.3 min (1.1–1.9) and the time to first response to TOF nerve stimulation was 9.6 min (6.5–12.6) and 10.5 min (7.0–14.0) in young and older children, respectively. The pharmacokinetic data were too sparse to allow analysis of the two age groups separately (8 and 8 patients), hence the data were pooled. The median clearances of the cis-cis, the cis-trans, and the trans-trans isomer were 5.5, 51.0 and 30.5 ml/kg/min, respectively. Conclusion: Our data indicate that there are no major differences in pharmacodynamics or pharmacokinetics of mivacurium between young (3–6 years) and older (10–14 years) children.

Optimal preoperative assessment of the geriatric surgical patient: a best practices guideline from the American College of Surgeons National Surgical Quality Improvement Program and the American Geriatrics Society.

Abstract: The population of the United States (US) is growing and aging.The US Census Bureau projects that the number of Americans age 65 years and older will more than double between 2010 and 2050. The percentage of Americans 65 and older will grow from 13% to more than 20% of the total population by 2030, and the fastest growing segment of this group (individuals 85 years and older) is expected to triple in number over the next 4 decades.These changes in the age demographics of the US population are largely due to people living longer and the “baby boomer” generation

Residual neuromuscular block is a risk factor for postoperative pulmonary complications: A prospective, randomised, and blinded study of postoperative pulmonary complications after atracurium, vecuronium and pancuronium

Abstract: Background: After anaesthesia involving pancuronium a high incidence of both residual neuromuscular block and postoperative pulmonary complications (POPC) has been reported. The aim of this study was to compare the incidence of POPC following the use of pancuronium, atracurium, and vecuronium, and to examine the effect of residual neuromuscular block on the incidence of POPC. Methods: A total of 691 adult patients undergoing abdominal, gynaecological, or orthopaedic surgery under general anaesthesia were randomised to receive either pancuronium, atracurium, or vecuronium. Perioperatively, the response to train-of-four (TOF) nerve stimulation was evaluated manually. Post-operatively, the TOF ratios were measured mechanomyograph-ically, and through a 6-day follow-up the patients were examined for pulmonary complications. Results: The incidence of residual block, defined as a TOF ratio <0.7, was significantly higher in the pancuronium group (59/226: 26%) than in the atracurium/vecuronium groups (24/450: 5.3%). In the pancuronium group, significantly more patients with residual block developed POPC (10/59: 16.9%) as compared to patients without residual block (8/167 4.8%). In the atracurium/vecuronium groups, the incidence of POPC was not significantly different in patients with (1/24: 4.2%) or without (23/426: 5.4%) residual block. Multiple regression analysis indicated that abdominal surgery, age, long-lasting surgery, and a TOF ratio<0.7 following the use of pancuronium were potential risk factors for the development of POPC. Conclusion: Postoperative residual block caused by pancuronium is a significant risk factor for development of POPC.

Residual neuromuscular blockade and critical respiratory events in the postanesthesia care unit

Abstract: BACKGROUND:Incomplete recovery of neuromuscular function may impair pulmonary and upper airway function and contribute to adverse respiratory events in the postanesthesia care unit (PACU). The aim of this investigation was to assess and quantify the severity of neuromuscular blockade in patients wit

Preoperative Pulmonary Evaluation

Abstract: Postoperative pulmonary complications are an important part of the risk of surgery and prolong the hospital stay by an average of one to two weeks.1 Much of the literature on the assessment of perioperative risk has focused on identifying the now well-defined cardiac risk factors. However, clinically significant postoperative pulmonary complications are as common as postoperative cardiac complications. According to one review, pulmonary complications were at least as common as or more common than cardiac complications in 17 of 25 studies of postoperative complications.2 This article reviews patient- and procedure-related risk factors, clinical evaluation, pulmonary-function testing, and risk-reduction strategies. The . . .

Strategies to reduce postoperative pulmonary complications after noncardiothoracic surgery: systematic review for the American College of Physicians.

Abstract: This background review supports the American College of Physicians' clinical practice guideline on reducing postoperative pulmonary complications after noncardiothoracic surgery.