Rodger E. Barnette

The use of somatosensory evoked potentials to determine the relationship between patient positioning and impending upper extremity nerve injury during spine surgery: a retrospective analysis.

Somatosensory evoked potential (SSEP) monitoring is used to prevent nerve damage in spine surgery and to detect changes in upper extremity nerve function. Upper extremity SSEP conduction changes may indicate impending nerve injury. We investigated the effect of operative positioning on upper extremity nerve function retrospectively in 1000 consecutive spine surgeries that used SSEP monitoring. The vast majority (92%) of upper extremity SSEP changes were reversed by modifying the arm position and were therefore classified as position-related. The incidence of position-related upper extremity SSEP changes was calculated and compared for five different surgical positions: supine arms out, supine arms tucked, lateral decubitus position, prone arms tucked, and the prone “superman” position. The overall incidence of position-related upper extremity SSEP changes was 6.1%. The lateral decubitus position (7.5%) and prone superman position (7.0%) had a significantly more frequent incidence of position-related upper extremity SSEP changes (P < 0.0001, Z-test for Poisson counts) compared with other positions (1.8%–3.2%). No patient with a reversible SSEP change developed a new postoperative deficit in the affected extremity. SSEP monitoring is of value in identifying and reversing impending upper extremity peripheral nerve injury.

Positioning patients for spine surgery: Avoiding uncommon position-related complications

Positioning patients for spine surgery is pivotal for optimal operating conditions and operative-site exposure. During spine surgery, patients are placed in positions that are not physiologic and may lead to complications. Perioperative peripheral nerve injury (PPNI) and postoperative visual loss (POVL) are rare complications related to patient positioning during spine surgery that result in significant patient disability and functional loss. PPNI is usually due to stretch or compression of the peripheral nerve. PPNI may present as a brachial plexus injury or as an isolated injury of single nerve, most commonly the ulnar nerve. Understanding the etiology, mechanism and pattern of injury with each type of nerve injury is important for the prevention of PPNI. Intraoperative neuromonitoring has been used to detect peripheral nerve conduction abnormalities indicating peripheral nerve stress under general anesthesia and to guide modification of the upper extremity position to prevent PPNI. POVL usually results in permanent visual loss. Most cases are associated with prolonged spine procedures in the prone position under general anesthesia. The most common causes of POVL after spine surgery are ischemic optic neuropathy and central retinal artery occlusion. Posterior ischemic optic neuropathy is the most common cause of POVL after spine surgery. It is important for spine surgeons to be aware of POVL and to participate in safe, collaborative perioperative care of spine patients. Proper education of perioperative staff, combined with clear communication and collaboration while positioning patients in the operating room is the best and safest approach. The prevention of uncommon complications of spine surgery depends primarily on identifying high-risk patients, proper positioning and optimal intraoperative management of physiological parameters. Modification of risk factors extrinsic to the patient may help reduce the incidence of PPNI and POVL.

Nominal Hemoptysis Heralds Pseudoaneurysm Induced by a Pulmonary Artery Catheter

Massive hemoptysis secondary to pulmonary artery rupture is a rare but often fatal complication of pulmonary artery catheters (PACs). We report a case of delayed fatal hemoptysis secondary to rupture of a PAC-induced pseudoaneurysm, which was heralded by a small amount of hemoptysis in association with a normal postinsertion CXR

Postoperative pain control by means of epidural narcotics in a patient with obstructive sleep apnea.

Airway obstruction has been reported in patients with sleep apnea after preoperative medication with parenteral diazepam or morphine (1). Presumably, the use of parenteral narcotics for pain control in the postoperative period would also increase the risk of airway obstruction in these patients. We describe the use of epidural narcotics for postoperative pain control in a patient with obstructive sleep apnea.

In vitro effect of fresh frozen plasma on the activated coagulation time in patients undergoing cardiopulmonary bypass

The in vitro effect of fresh frozen plasma (FFP) on the whole blood activated coagulation time (ACT) was examined in 18 patients undergoing cardiopulmonary bypass (CPB) during coronary artery bypass graft surgery. The addition of FFP to whole blood in vitro, after systemic heparinization, significantly prolonged the ACT from 451 2 21 seconds (mean ± SE) to 572 ± 41 seconds (P > 0.05). There was no significant correlation between the plasma antithrombin 111 activity and the prolongation in ACT after systemic heparinization, with or without addition of FFP. The addition of FFP to whole blood in three of the six patients who exhibited heparin resistance (ACT <400 seconds after administration of 350 unit/kg heparin) did not prolong the ACT to >400 seconds. Theseobservations suggest that infusion of FFP will further prolong the ACT after heparin administration in most patients including some with initial heparin resistance.

Anesthetic Considerations in Candidates for Lung Volume Reduction Surgery

The administration of anesthesia to patients undergoing lung volume reduction surgery (LVRS) requires a complete understanding of the pathophysiology of severe chronic obstructive pulmonary disease, the planned surgical procedure, and the anticipated postoperative course for this group of patients. Risk factors and associated morbidity and mortality are discussed within the context of patients with obstructive pulmonary disease in the National Emphysema Treatment Trial having surgical procedures. Preoperative evaluation and the anesthetic techniques used for patients undergoing LVRS are reviewed, as are monitoring requirements. Intraoperative events, including induction of anesthesia, lung isolation, management of fluid requirements, and options for ventilatory support are discussed. Possible intraanesthetic complications are also reviewed, as is the optimal management of such problems, should they occur. To minimize the potential for a surgical air leak in the postoperative period, positive-pressure ventilation must cease at the conclusion of the procedure. An awake, comfortable, extubated patient, capable of spontaneous ventilation, is only possible if there is careful attention to pain control. The thoracic epidural is the most common pain control method used with patients undergoing LVRS procedures; however, other alternative methods are reviewed and discussed.

Sequestration of vecuronium bromide during extremity surgery involving use of a pneumatic tourniquet

Background: We hypothesized that sequestration of a neuromuscular blocking agent could occur during surgery involving use of an extremity tourniquet and cause changes in neuromuscular function after tourniquet release.

The Use of Somatosensory Evoked Potentials to Determine the Relationship Between Intraoperative Arterial Blood Pressure and Intraoperative Upper Extremity Position-Related Neurapraxia in the Prone Surrender Position During Spine Surgery: A Retrospective Analysis.

BACKGROUND:Peripheral nerve injury is a significant perioperative problem. Intraoperative position-related neurapraxia may indicate impending peripheral nerve injury and can be detected by changes in somatosensory evoked potentials (SSEP). The purpose of this retrospective analysis of spine surgeries performed under general anesthesia with SSEP monitoring was to determine the relationship between intraoperative mean arterial blood pressure (MAP) and intraoperative upper extremity position–related neurapraxia in the prone surrender (superman) position. METHODS:We reviewed a computerized database of spine surgeries performed on adult patients in the prone surrender position. The authors reviewed intraoperative SSEP monitoring reports to identify the patients who developed intraoperative upper extremity position–related neurapraxia (case group) and patients who did not (control group). Propensity matching was performed to derive 2 demographically matched groups. Preoperative and intraoperative variables were included in the univariate Cox regression analysis of risk factors associated with neurapraxia. Multivariate Cox regression models were used to identify the independent risk factors. RESULTS:One hundred fifty-two patients were included in the analysis. The case group included 32 patients, whereas the control group included 120 matched patients. Intraoperative MAP <55 mm Hg for a total duration of ≥5 minutes was an independent risk factor associated with a greater incidence of upper extremity position–related neurapraxia compared with a duration of <5 minutes with MAP <55 mm Hg (hazard ratio, 3.43; confidence interval, 1.445–8.148; P = 0.0052). Intraoperative MAP >80 mm Hg for a total duration of >55 minutes was an independent predictor associated with a lower incidence of neurapraxia compared with a total duration ⩽55 minutes (hazard ratio, 0.341; confidence interval, 0.163–0.717; P = 0.0045). CONCLUSIONS:In this study, we identified the changes in intraoperative MAP as independent predictors associated with upper extremity position–related neurapraxia in the prone surrender position under general anesthesia.

ISRADIPINE FOR TREATMENT OF ACUTE HYPERTENSION AFTER MYOCARDIAL REVASCULARIZATION

Objective.To evaluate the efficacy and duration of action of iv isradipine in the control of postoperative hypertension immediately after myocardial revascularization. Design.Prospective, phase 2 trial. Setting.Surgical ICU, university hospital. Patients.Twenty-one (15 male, six female) patients, ages 49 to 75 yr (mean 65 ± 5), undergoing elective myocardial revascularization. Interventions.Twenty-one patients with postoperative hypertension after coronary artery bypass graft surgery received iv isradipine, a new dihydropyridine calcium-channel antagonist. Mean duration of the isradipine infusion was 96.9 ± 29 min. Mean dose of isradipine, indexed to weight, was 16.63 ± 6.66 μg/kg (n = 20). Measurements and Main Results.Twenty of the 21 patients achieved satisfactory BP control. The reduction in mean arterial pressure (MAP), first noted at the 15-min point, was maximal at 1 hr when MAP decreased from 102 ± 9 mm Hg baseline to 81 ± 5 mm Hg (p < .01), accompanied by a significant (p < .01) decrease in systemic vascular resistance from 1753 ± 339 baseline to 1180 ± 229 dyne-sec/cm5. The CVP, pulmonary artery diastolic pressure, and pulmonary artery occlusion pressure did not change significantly. Heart rate and cardiac index increased; however, stroke volume index did not change. Conclusions.Isradipine is an acceptable agent for the treatment of hypertension in this setting. (Crit Care Med 1991; 19:334)

Use of Neuromuscular Blocking Agents in the Intensive Care Unit

In the mid-1980s, the two intermediate-duration neuromuscular blocking (NMB) agents atracurium and vecuronium were introduced into practice; within a few years, these accounted for the majority of NMB agent use in critically ill patients. In association with the introduction of these new agents, there was an expansion of the indications for muscle paralysis in this country, which was at least partially related to new ventilatory modes and technologic advances that necessitated cooperative, sedate, or immobile patients. These new indications for an immobile patient, coupled with an expanded knowledge of available NMB agents, led to a dramatic increase in the use of muscle paralysis in the intensive care unit (ICU). In association with that increased use came a growing awareness of the potential for severe complications and side effects.