André Boezaart - Academia.edu (original) (raw)

Papers by André Boezaart

We describe a method of dynamic assessment of patellar tracking intraoperatively during a Fulkers... more We describe a method of dynamic assessment of patellar tracking intraoperatively during a Fulkerson osteotomy. We utilize an electrically conductive catheter intraopertively to directly stimulate the femoral nerve to cause quadriceps muscle contraction. The resultant active knee ex- tension allows dynamic assessment of patellofemoral tracking prior to and after final Fulkerson fixation. This dynamic intraopertive technique allows us to approximate

Pain medicine (Malden, Mass.), Jan 29, 2015

Given their ability to process highly dimensional datasets with hundreds of variables, machine le... more Given their ability to process highly dimensional datasets with hundreds of variables, machine learning algorithms may offer one solution to the vexing challenge of predicting postoperative pain. Here, we report on the application of machine learning algorithms to predict postoperative pain outcomes in a retrospective cohort of 8,071 surgical patients using 796 clinical variables. Five algorithms were compared in terms of their ability to forecast moderate to severe postoperative pain: Least Absolute Shrinkage and Selection Operator (LASSO), gradient-boosted decision tree, support vector machine, neural network, and k-nearest neighbor (k-NN), with logistic regression included for baseline comparison. In forecasting moderate to severe postoperative pain for postoperative day (POD) 1, the LASSO algorithm, using all 796 variables, had the highest accuracy with an area under the receiver-operating curve (ROC) of 0.704. Next, the gradient-boosted decision tree had an ROC of 0.665 and the...

Pain Medicine, 2015

ABSTRACT

A & A case reports, 2015

Electrical storm (ES) is a syndrome characterized by recurrent ventricular fibrillation or tachyc... more Electrical storm (ES) is a syndrome characterized by recurrent ventricular fibrillation or tachycardia. It is a major clinical challenge and is often unresponsive to conventional drug therapy; instead, its treatment requires multiple attempts at electrical defibrillation. Sympathetic hyperactivity is an important modulator of ventricular arrhythmias, including ES. We report a case of ES treated safely and effectively with pharmacologic sympathectomy involving diagnostic continuous stellate ganglion blockade with local anesthetic followed by therapeutic neurolysis. This technique reduced ES in a patient for whom conservative medical and interventional procedures were ineffective.

Regional anesthesia and pain medicine

Regional anesthesia and pain medicine

A study using unblinded block performance and subjective outcome measurements suggested that &quo... more A study using unblinded block performance and subjective outcome measurements suggested that "opening the space" surrounding the femoral nerve with 10 mL dextrose 5% in water (D5W) before catheter placement facilitated placement and improved the quality of the nerve block. We conducted a double-blind, prospectively randomized study to evaluate this suggestion by adding objective measurements to the original subjective measurements. A Tuohy needle was directed toward the femoral nerve under ultrasound and nerve stimulator guidance. A quadriceps femoris motor response was identified by cephalad patellar movements with a maximum nerve stimulator output of 0.5 mA. The primary anesthesiologist either injected D5W or made no injection through the needle, depending on patient randomization. A second anesthesiologist, unaware of randomization, placed the stimulating perineural catheter. The primary measurement was the procedure time (in seconds) for threading the catheter. Additio...

Regional Anesthesia and Pain Medicine, 2012

Regional Anesthesia and Pain Medicine, 2009

... FV, Neal JM. A tale of two needle passes. Reg Anesth Pain Med. 2008;33:195-198. ... 3. Fredri... more ... FV, Neal JM. A tale of two needle passes. Reg Anesth Pain Med. 2008;33:195-198. ... 3. Fredrickson MJ, Ball CM, Dalgleish AJ. Successful continuous interscalene analgesia for ambulatory shoulder surgery in a private practice setting. Reg Anesth Pain Med. 2008;33:122-128. ...

Regional Anesthesia and Pain Medicine, 2006

Regional Anesthesia and Pain Medicine, 2005

Regional Anesthesia and Pain Medicine, 2006

Regional Anesthesia and Pain Medicine, 2006

The subgluteal approach is common for sciatic nerve block. Although the surface landmarks are cle... more The subgluteal approach is common for sciatic nerve block. Although the surface landmarks are clear, the depth of this nerve at this level is difficult to judge. The purpose of this study is to establish a method of estimating the sciatic nerve depth using the anteroposterior (AP) diameter of the thigh as a marker. The study was undertaken in 2 phases. Phase 1 entailed review of 100 magnetic resonance images (MRIs) of the pelvis and proximal lower extremity of patients. Measurements were taken of the AP diameter of the thigh at the midpoint of the lesser trochanter and then compared with distances of the sciatic nerves from the skin of the posterior aspect of the thigh at the same level. Phase 2 involved enrolling 40 patients undergoing lower-extremity surgery for whom subgluteal sciatic nerve blocks were indicated. The AP diameters of the thighs were measured from the subgluteal groove to the inguinal groove with the patient in the supine position. Placing the patient in the lateral position, the subgluteal sciatic block was then performed by using a stimulating needle. The distances from the skin at which the sciatic nerves were actually found, as estimated by maximum motor response to stimulus, were noted. Phase 1 showed a mean AP diameter of 18.94 cm +/- 2.61 cm (mean +/- standard deviation [SD]), mean nerve depth of 6.51 cm +/- 1.46 cm (mean +/- SD), and a linear regression slope of 0.48. Phase 2 showed a mean AP diameter of 16.28 cm +/- 2.73 cm (mean +/- SD), a mean nerve depth of 6.99 cm +/- 1.39 cm (mean +/- SD), and a linear regression slope of 0.43. The thigh diameters differed (P < .001) between the groups, but there was no difference in the depth to the sciatic nerve between the 2 groups (P = .07). Comparing phase 1 and phase 2 datasets shows the slopes of linear regression lines are nearly parallel. The clinical data from phase 2 verify the anatomical data collected in phase 1 and show that the sciatic nerve depth to AP diameter ratio is 0.43 or the depth of the sciatic nerve is approximately 43% of thigh diameter if the patient is positioned in the lateral decubitus position.

Regional Anesthesia and Pain Medicine, 2004

To minimize the risk of intraneural injection when performing nerve blocks, some authors caution ... more To minimize the risk of intraneural injection when performing nerve blocks, some authors caution against injecting through a needle placed with motor responses observed at nerve stimulator output settings of 0.3 mA or less. We present a case of placing a continuous cervical paravertebral catheter with brisk motor response while stimulating the catheter at 0.05 mA, with no adverse sequelae. A 56-year-old man scheduled for rotator cuff repair received a continuous cervical paravertebral block for intraoperative and postoperative pain control. A stimulating catheter was used for the block. During catheter placement, nerve stimulator output was decreased to 0.05 mA at 300 micros and the motor response remained brisk. The patient was not significantly sedated and experienced no pain during placement or with injection of 40 mL of 0.5% ropivacaine through the catheter. Narcotic drugs were not required during surgery, and the block provided excellent postoperative pain control. Catheter position was evaluated by fluoroscopy to further identify the catheter's relationship to the brachial plexus. The nerve trunks of C5 and C6 were clearly visible after 1 mL of iohexol (Omnipaque) was injected through the catheter. The catheter was removed the following day. At the follow-up visit 2 weeks later, the patient's neurological examination remained unremarkable. We present a single case of successful placement of a stimulating catheter with no neurological injury even when motor response occurred at very low nerve stimulator output settings.

Regional Anesthesia and Pain Medicine, 2004

The purpose of this case report is to describe the use of the cervical paravertebral block as the... more The purpose of this case report is to describe the use of the cervical paravertebral block as the sole anesthetic for shoulder surgery in a patient unable to tolerate general anesthesia. Recent literature describes the continuous cervical paravertebral block as an effective alternative to the interscalene block for the management of postoperative pain after shoulder surgery. An 85-year-old man with severe respiratory and cardiac disease presented for major shoulder surgery. The patient's complex medical history required an anesthetic technique that would avoid general anesthesia and preserve phrenic nerve function. This case report describes, to our knowledge, the first successful use of the continuous cervical paravertebral block as the sole anesthetic for shoulder surgery. Continuous cervical paravertebral block provided excellent surgical conditions and postoperative pain relief for this patient and allowed gradual and intermittent dosing of the catheter and continuous assessment of the anesthetic impact on respiratory function.

Regional Anesthesia and Pain Medicine, 2010

Regional Anesthesia and Pain Medicine, 2004

Identification of elicited muscle twitches while performing infraclavicular block of the brachial... more Identification of elicited muscle twitches while performing infraclavicular block of the brachial plexus is often confusing but is critical for success of the block. An easily defined endpoint when evaluating these motor responses to neurostimulation is essential, as it is necessary to block the appropriate cord or cords. In addition to an extensive review of the motor and sensory neuroanatomy of the upper extremity, we describe an easy method to learn and remember the motor response to stimulation of each of the cords of the brachial plexus. If the arm is positioned in the anatomical position, the 5th digit (pinkie) moves laterally (pronation of the forearm) when the lateral cord is stimulated, posteriorly (extension) when the posterior cord is stimulated, and medially (flexion) when the medial cord is stimulated. The pinkie thus moves "toward" the cord that is stimulated.

Regional Anesthesia and Pain Medicine, 2003

Regional Anesthesia and Pain Medicine, 2006

We describe a method of dynamic assessment of patellar tracking intraoperatively during a Fulkers... more We describe a method of dynamic assessment of patellar tracking intraoperatively during a Fulkerson osteotomy. We utilize an electrically conductive catheter intraopertively to directly stimulate the femoral nerve to cause quadriceps muscle contraction. The resultant active knee ex- tension allows dynamic assessment of patellofemoral tracking prior to and after final Fulkerson fixation. This dynamic intraopertive technique allows us to approximate

Pain medicine (Malden, Mass.), Jan 29, 2015

Given their ability to process highly dimensional datasets with hundreds of variables, machine le... more Given their ability to process highly dimensional datasets with hundreds of variables, machine learning algorithms may offer one solution to the vexing challenge of predicting postoperative pain. Here, we report on the application of machine learning algorithms to predict postoperative pain outcomes in a retrospective cohort of 8,071 surgical patients using 796 clinical variables. Five algorithms were compared in terms of their ability to forecast moderate to severe postoperative pain: Least Absolute Shrinkage and Selection Operator (LASSO), gradient-boosted decision tree, support vector machine, neural network, and k-nearest neighbor (k-NN), with logistic regression included for baseline comparison. In forecasting moderate to severe postoperative pain for postoperative day (POD) 1, the LASSO algorithm, using all 796 variables, had the highest accuracy with an area under the receiver-operating curve (ROC) of 0.704. Next, the gradient-boosted decision tree had an ROC of 0.665 and the...

Pain Medicine, 2015

ABSTRACT

A & A case reports, 2015

Electrical storm (ES) is a syndrome characterized by recurrent ventricular fibrillation or tachyc... more Electrical storm (ES) is a syndrome characterized by recurrent ventricular fibrillation or tachycardia. It is a major clinical challenge and is often unresponsive to conventional drug therapy; instead, its treatment requires multiple attempts at electrical defibrillation. Sympathetic hyperactivity is an important modulator of ventricular arrhythmias, including ES. We report a case of ES treated safely and effectively with pharmacologic sympathectomy involving diagnostic continuous stellate ganglion blockade with local anesthetic followed by therapeutic neurolysis. This technique reduced ES in a patient for whom conservative medical and interventional procedures were ineffective.

Regional anesthesia and pain medicine

Regional anesthesia and pain medicine

A study using unblinded block performance and subjective outcome measurements suggested that &quo... more A study using unblinded block performance and subjective outcome measurements suggested that "opening the space" surrounding the femoral nerve with 10 mL dextrose 5% in water (D5W) before catheter placement facilitated placement and improved the quality of the nerve block. We conducted a double-blind, prospectively randomized study to evaluate this suggestion by adding objective measurements to the original subjective measurements. A Tuohy needle was directed toward the femoral nerve under ultrasound and nerve stimulator guidance. A quadriceps femoris motor response was identified by cephalad patellar movements with a maximum nerve stimulator output of 0.5 mA. The primary anesthesiologist either injected D5W or made no injection through the needle, depending on patient randomization. A second anesthesiologist, unaware of randomization, placed the stimulating perineural catheter. The primary measurement was the procedure time (in seconds) for threading the catheter. Additio...

Regional Anesthesia and Pain Medicine, 2012

Regional Anesthesia and Pain Medicine, 2009

... FV, Neal JM. A tale of two needle passes. Reg Anesth Pain Med. 2008;33:195-198. ... 3. Fredri... more ... FV, Neal JM. A tale of two needle passes. Reg Anesth Pain Med. 2008;33:195-198. ... 3. Fredrickson MJ, Ball CM, Dalgleish AJ. Successful continuous interscalene analgesia for ambulatory shoulder surgery in a private practice setting. Reg Anesth Pain Med. 2008;33:122-128. ...

Regional Anesthesia and Pain Medicine, 2006

Regional Anesthesia and Pain Medicine, 2005

Regional Anesthesia and Pain Medicine, 2006

Regional Anesthesia and Pain Medicine, 2006

The subgluteal approach is common for sciatic nerve block. Although the surface landmarks are cle... more The subgluteal approach is common for sciatic nerve block. Although the surface landmarks are clear, the depth of this nerve at this level is difficult to judge. The purpose of this study is to establish a method of estimating the sciatic nerve depth using the anteroposterior (AP) diameter of the thigh as a marker. The study was undertaken in 2 phases. Phase 1 entailed review of 100 magnetic resonance images (MRIs) of the pelvis and proximal lower extremity of patients. Measurements were taken of the AP diameter of the thigh at the midpoint of the lesser trochanter and then compared with distances of the sciatic nerves from the skin of the posterior aspect of the thigh at the same level. Phase 2 involved enrolling 40 patients undergoing lower-extremity surgery for whom subgluteal sciatic nerve blocks were indicated. The AP diameters of the thighs were measured from the subgluteal groove to the inguinal groove with the patient in the supine position. Placing the patient in the lateral position, the subgluteal sciatic block was then performed by using a stimulating needle. The distances from the skin at which the sciatic nerves were actually found, as estimated by maximum motor response to stimulus, were noted. Phase 1 showed a mean AP diameter of 18.94 cm +/- 2.61 cm (mean +/- standard deviation [SD]), mean nerve depth of 6.51 cm +/- 1.46 cm (mean +/- SD), and a linear regression slope of 0.48. Phase 2 showed a mean AP diameter of 16.28 cm +/- 2.73 cm (mean +/- SD), a mean nerve depth of 6.99 cm +/- 1.39 cm (mean +/- SD), and a linear regression slope of 0.43. The thigh diameters differed (P < .001) between the groups, but there was no difference in the depth to the sciatic nerve between the 2 groups (P = .07). Comparing phase 1 and phase 2 datasets shows the slopes of linear regression lines are nearly parallel. The clinical data from phase 2 verify the anatomical data collected in phase 1 and show that the sciatic nerve depth to AP diameter ratio is 0.43 or the depth of the sciatic nerve is approximately 43% of thigh diameter if the patient is positioned in the lateral decubitus position.

Regional Anesthesia and Pain Medicine, 2004

To minimize the risk of intraneural injection when performing nerve blocks, some authors caution ... more To minimize the risk of intraneural injection when performing nerve blocks, some authors caution against injecting through a needle placed with motor responses observed at nerve stimulator output settings of 0.3 mA or less. We present a case of placing a continuous cervical paravertebral catheter with brisk motor response while stimulating the catheter at 0.05 mA, with no adverse sequelae. A 56-year-old man scheduled for rotator cuff repair received a continuous cervical paravertebral block for intraoperative and postoperative pain control. A stimulating catheter was used for the block. During catheter placement, nerve stimulator output was decreased to 0.05 mA at 300 micros and the motor response remained brisk. The patient was not significantly sedated and experienced no pain during placement or with injection of 40 mL of 0.5% ropivacaine through the catheter. Narcotic drugs were not required during surgery, and the block provided excellent postoperative pain control. Catheter position was evaluated by fluoroscopy to further identify the catheter's relationship to the brachial plexus. The nerve trunks of C5 and C6 were clearly visible after 1 mL of iohexol (Omnipaque) was injected through the catheter. The catheter was removed the following day. At the follow-up visit 2 weeks later, the patient's neurological examination remained unremarkable. We present a single case of successful placement of a stimulating catheter with no neurological injury even when motor response occurred at very low nerve stimulator output settings.

Regional Anesthesia and Pain Medicine, 2004

The purpose of this case report is to describe the use of the cervical paravertebral block as the... more The purpose of this case report is to describe the use of the cervical paravertebral block as the sole anesthetic for shoulder surgery in a patient unable to tolerate general anesthesia. Recent literature describes the continuous cervical paravertebral block as an effective alternative to the interscalene block for the management of postoperative pain after shoulder surgery. An 85-year-old man with severe respiratory and cardiac disease presented for major shoulder surgery. The patient's complex medical history required an anesthetic technique that would avoid general anesthesia and preserve phrenic nerve function. This case report describes, to our knowledge, the first successful use of the continuous cervical paravertebral block as the sole anesthetic for shoulder surgery. Continuous cervical paravertebral block provided excellent surgical conditions and postoperative pain relief for this patient and allowed gradual and intermittent dosing of the catheter and continuous assessment of the anesthetic impact on respiratory function.

Regional Anesthesia and Pain Medicine, 2010

Regional Anesthesia and Pain Medicine, 2004

Identification of elicited muscle twitches while performing infraclavicular block of the brachial... more Identification of elicited muscle twitches while performing infraclavicular block of the brachial plexus is often confusing but is critical for success of the block. An easily defined endpoint when evaluating these motor responses to neurostimulation is essential, as it is necessary to block the appropriate cord or cords. In addition to an extensive review of the motor and sensory neuroanatomy of the upper extremity, we describe an easy method to learn and remember the motor response to stimulation of each of the cords of the brachial plexus. If the arm is positioned in the anatomical position, the 5th digit (pinkie) moves laterally (pronation of the forearm) when the lateral cord is stimulated, posteriorly (extension) when the posterior cord is stimulated, and medially (flexion) when the medial cord is stimulated. The pinkie thus moves "toward" the cord that is stimulated.

Regional Anesthesia and Pain Medicine, 2003

Regional Anesthesia and Pain Medicine, 2006