Best zero level for external ICP transducer.

BACKGROUND: Continuous monitoring of intracranial pressure (ICP) was introduced in the 1950s. For correct ICP recordings, the zero-reference point for the external pressure gauge must be placed next to a head anatomical structure. We evaluated different anatomical points as zero reference for the ICP device at different head positions and their relation to brain centre (BC), foramen of Monro (Monro), and brain surface. METHODS: Patients referred for neuroimaging due to e.g. headache all having normal 3D MRI scans were selected. Monro, BC, Orbit(O), external auditory meatus (EAM), and orbito-meatal (OM) line were identified and projected to mid-sagittal, or axial images. Each scan was evaluated like lying supine, 45° head elevations, upright, and 45° lateral position. Distances from skin to brain surface, BC, and Monro were measured. All values are presented as mean ± SD and/or range in millimetre. For conversion to mmHg, millimetre was multiplied by 0.074. RESULTS: Twenty MRI scans were examined. A zero reference at EAM or glabella was ideal at BC when head was strict supine or in the lateral position. At 45° head elevation, an overestimation of the BC-ICP by 4.8 ± 0.8 and in upright 5.6 ± 0.5 mmHg was found, and 45° lateral underestimated ICP-BC by 6.3 ± 1.0 mmHg. Monro was situated 45 ± 5 mm rostral to the mid-OM line and 24 (18-31) mm inferior and 13 (8-17) mm in front of BC. A zero-reference point aligned with the highest point of the head underestimated BC-ICP and Monro-ICP. If the ICP reading was added 5.9 or 6.3 mmHg, respectively, a deviation from BC-ICP was ≤ 1.8 mmHg and Monro-ICP was ≤ 0.9 mmHg in all head positions. CONCLUSIONS: EAM and glabella are defined anatomical structures representing BC when strict supine or lateral but with 12 mmHg variation with different head positions used in clinical practice. The OM line follows Monro at head elevation, but not when the head is turned. When the highest external point on the head is used, ICP values at brain surface as well as Monro and BC are underestimated. This underestimation is fairly constant and, when corrected for, provides the most exact ICP reading.

The intracranial pressure curve correlates to the pulsatile component of cerebral blood flow.

Current methods to measure cerebral blood flow (CBF) in the neuro critical care setting cannot monitor the CBF continuously. In contrast, continuous measurement of intracranial pressure (ICP) is readily accomplished, and there is a component of ICP that correlates with arterial inflow of blood into the cranial cavity. This property may have utility in using continuous ICP curve analysis to continuously estimate CBF. We examined the data from 13 patients, monitored with an intraventricular ICP device determining the pulsatile amplitude ICPamp as well as the area under the ICP curve (AUCICP). Using an elastance measurement, the ICP curve was converted to craniospinal volume (AUCΔV). The patients were examined with Phase Contrast Magnetic Resonance Imaging (MRI), measuring flow in the carotid and vertebral arteries. This made it possible to calculate CBF for one cardiac cycle (ccCBFMRtot) and divide it into the pulsatile (ccCBFMRpuls) and non-pulsatile (ccCBFMRconst) flow. ICP derived data and MRI measurements were compared. Linear regression was used to establish wellness of fit and ANOVA was used to calculate the P value. No correlation was found between ICPamp and the ccICPMRpuls (P = 0.067). In contrast there was a correlation between the AUCICP and ccCBFMRpuls (R2 = 0.440 P = 0.013). The AUCΔV correlated more appropriately with the ccCBFMRpuls. (R2 = 0.688 P < 0.001). Our findings suggests that the pulsatile part of the intracranial pressure curve, especially when transformed into a volume curve, correlates to the pulsatile part of the CBF.

A decision support model for prescribing internal cardiac defibrillators.

PURPOSE: Automatic internal cardiac defibrillators have various indications for placement. However, some patients may not fully benefit from this technology and the devices are expensive. Consequently, the aim of this paper is to describe a development model for clinical decision support to help providers offer their patients a more effective decision-making process. DESIGN/METHODOLOGY/APPROACH: A decision tree was built based on previous trials described in the cardiac literature. FINDINGS: A decision-making model for implanting these expensive but lifesaving devices is developed and a model for testing them (pre- and post-implantation) is described. PRACTICAL IMPLICATIONS: The model could be used to develop prospective trials. ORIGINALITY/VALUE: The paper demonstrates that the project's goal is better quality and cost-effective care.

Esophageal tear in a patient undergoing stereotactic brain biopsy under general anesthesia.

Injuries of the esophagus with resultant mediastinitis have been reported following endotracheal intubation. Herein, we report a case of esophageal perforation that resulted from difficulty with intubation in a patient with a stereotactic head frame. A 52-year-old woman underwent a stereotactic brain biopsy of a left temporal tumor. After a stereotactic head frame was applied, intubation for anesthesia required three attempts. On postoperative day 2, she complained of worsening dysphagia and chest pain. A 4-mm tear in the right posterior cervical esophagus was discovered and repaired. Esophageal perforation may arise from limited neck extension imposed by a stereotactic head frame. Unexplained dysphagia postoperatively is the hallmark of this rare complication.

Rhabdomyolysis after transnasal repair of anterior basal encephalocele.

BACKGROUND: Postoperative Rhabdomyolysis (RM) is rare after neurosurgical procedures. Furthermore, it has not been observed after transnasal approaches. The authors report a case of idiopathic RM occurring after transnasal resection of a sincipital encephalocele. CASE DESCRIPTION: A 32-year-old woman underwent a transnasal resection of a sincipital encephalocele after 6 years of intermittent clear nasal drainage. Postoperatively, she experienced severe back pain, peripheral neuropathy, associated with a markedly elevated creatinine kinase, and severe RM. The patient was treated with hydration and forced urine alkalization and treated symptomatically for her pain and neuropathy. She ultimately made a full recovery without complication. CONCLUSION: Rhabdomyolysis is a rare but known complication of neurosurgical procedures. We report the first known case report of RM after a transnasal procedure. Furthermore, a review of documented postneurosurgical cases of RM is presented and reveals that the causes and risk factors for this complication after neurosurgery are similar to those in other surgical subspecialties.

The ethics of rationing of critical care services: should technology assessment play a role?

The costs of health care continue to increase rapidly and steeply in the United States. One area of great expense is that of intensive care units (ICUs). The causes of inflation have not been addressed effectively. ICU resources could become stretched such that they may no longer be available. This paper discusses some of the ethics and concerns behind decision making when providing ICU services in the United States. In particular, the use of electronic records with decision making tools, risk-analysis methods, and documentation of patient wishes for extraordinary care may help with better utilization of resources in the future.

The anesthesia information management system for electronic documentation: what are we waiting for?

The anesthesia information management system (AIMS) will be part of the future of healthcare. An electronic medical records system or AIMS will provide clear and concise information and have the potential to integrate information across the entire hospital system, improve quality of care, reduce errors, decrease risks, and improve revenue capture. The practice of anesthesia requires a medical record system that can capture data in real time. In this article, we describe challenges that must be overcome to establish an efficient electronic medical record system for anesthesiology.

A comparison of intensive care unit physician staffing costs at the 3 Mayo Clinic sites.

OBJECTIVES: To determine the provider cost of administering intensive care unit (ICU) services, comparing 3 different staffing models for ICU coverage, and to compare the costs of using house staff vs nonphysician providers (NPPs). METHODS: Data were collected on total staff composition and number of beds In ICUs from January 1, 2004, through December 31, 2004, at the 3 Mayo Clinic sites: Rochester, Minn; Jacksonville, Fla; and Scottsdale, Ariz. Institutional or national average staff salaries were used to determine total staffing costs per ICU bed per year at each site. Medicare medical education reimbursements were also taken into account. RESULTS: Costs per ICU bed for physician staffing were $18,630 in Rochester, $37,515 in Jacksonville, and $38,010 in Scottsdale. When NPPs were substituted for house staff, the costs per bed were $72,466 in Rochester, $61,291 in Jacksonville, and $49,909 in Scottsdale. Incremental costs per ICU bed using NPPs were $53,836 in Rochester, $23,776 in Jacksonville, and $11,899 in Scottsdale. CONCLUSION: Use of residents and fellows in ICU staffing at a major tertiary health center is more cost-efficient than use of NPPs. This finding could have Implications for the cost of physician services in nonteaching community hospitals and the methods by which care is provided.

A correlation of catecholamine and vasoactive Peptide release with hemodynamics in patients undergoing resection of arteriovenous malformations.

INTRODUCTION: Control of blood pressure can be a problem for intracranial procedures. To investigate the relationship between hemodynamic variables and endogenous vasoactive substances, we studied patients undergoing resection of arteriovenous malformations (AVMs). METHODS: This was a nonrandomized, prospective study of six patients who had resection of an intracranial AVM and six patients who had clipping of an intracranial aneurysm (ICA) that had not bled. Operative and postoperative blood pressure was controlled with sodium nitroprusside. Heart rate (HR), mean arterial pressure, pulmonary capillary wedge pressure, and cardiac index (CI) were measured after induction of anesthesia; before, during, and after hypotensive anesthesia; immediately postoperatively; and at 12, 24, and 36 hours postoperatively. Blood samples were drawn simultaneously in the AVM group to measure levels of norepinephrine, epinephrine, renin, aldosterone, vasopressin, angiotensin I, and angiotensin II and correlated with significant hemodynamic changes. RESULTS: HR and CI increased significantly among patients with AVMs compared with patients with ICAs (p<0.001 and p=0.05, respectively). HR was significantly correlated with renin (r=0.60), norepinephrine (r=1.00), and vasopressin (r=0.66). CI was significantly correlated with epinephrine (r=1.00), renin (r=0.77), angiotensin II (r=0.71), and vasopressin (r=0.82). Patients with AVMs had a hyperdynamic state characterized by increases in HR and CI. These increases were accompanied by increased renin, norepinephrine, vasopressin, epinephrine, and angiotensin II serum concentrates. CONCLUSIONS: There were no significant differences in blood pressure changes between patients who had resection for AVM and those who had clipping of ICA, probably due to the use of sodium nitroprusside in the AVM group. Patients with AVMs had a hyperdynamic state with increases in epinephrine, norepinephrine, angiotensin II, plasma renin activity, and vasopressin. Whether this hyperdynamic state is caused by the resection of the AVM or the use of sodium nitroprusside (SNP) cannot be concluded. Blockage of these mediators preoperatively may help control blood pressure without sodium nitroprusside.

A prospective trial of diaspirin cross-linked hemoglobin solution in patients after elective repair of abdominal aortic aneurysm.

We evaluated the safety, pharmacokinetics, and pharmacodynamics of diaspirin cross-linked hemoglobin (DCLHb) solution in patients after repair of abdominal aortic aneurysm. We performed a randomized, single-blind controlled study with 10 patients in the surgical intensive care unit of a tertiary care facility. Within 24 hours after repair of an abdominal aortic aneurysm, each patient received an infusion of DCLHb (50 mg/kg or 35 mL for a 70-kg patient) or an equal volume of hetastarch. Variables were measured before infusion, at 15 and 30 minutes postinfusion, and at hourly intervals up to 72 hours. Compared with controls, the experimental group had significantly greater mean pulmonary artery pressure at 30 minutes (mean +/- SD, 26.4 +/- 3.18 vs. 22.8 +/- 2.86 mm Hg), greater mean arterial pressure through 30 minutes (100.8 +/- 8.67 vs. 81.6 +/- 13.8 mm Hg), and greater plasma hemoglobin through 2 hours (69.3 +/- 6.08 vs. 1.8 +/- 0 g/dL). Cardiac output was significantly less in the DCLHb group at 2 hours (5.34 +/- 7.92 vs. 6.18 +/- 0.54 L/minute), levels of serum bilirubin were significantly less at 24 and 48 hours (94 +/- 0.26 vs. 1.56 +/- 0.73 mg/dL), and platelet counts were significantly greater at 24 hours (128 +/- 35.8 vs. 101 +/- 55.7 mg/dL). The two groups did not differ in oxygen delivery or consumption. One patient treated with DCLHb had a myocardial infarction 36 hours postinfusion. No patient had antibodies to DCLHb. At this dosage, DCLHb was well tolerated without severe organ dysfunction or toxicity. However, its use may lead to decreases in cardiac output because of increases in afterload, which may pose serious problems with left ventricular function.

The effect of craniotomy location on postoperative pain and nausea.

PURPOSE: At least one retrospective study has suggested that the need for postoperative control of pain and nausea depends on the location of the cranial surgery. This prospective study was performed to examine the hypothesis that patients who have had infratentorial craniotomy experience more severe pain and more frequent nausea than those with supratentorial procedures. METHODS: We compared postoperative outcomes in 28 patients with infratentorial craniotomy, 53 with supratentorial craniotomy, and 47 with complex spinal cord surgery (the control group). Anesthesia was standardized for all three groups and the concentration of isoflurane was titrated to keep mean arterial pressure within 30% of preoperative values. Severity of pain and frequency of nausea and vomiting were recorded for 24 h after surgery. Pain was assessed with a verbal pain score scale of 0-10, with 10 being the worst pain imaginable. Data were collected for 24 h postoperatively. RESULTS: Because nausea and pain diminish drastically 2 h after surgery, pairwise differences were assessed at each point within the first 2 h. Within 30 min of extubation, median pain scores in the supratentorial and spine groups rose to 2 and in the infratentorial group to 5. The statistical differences between groups were not significant ( P > 0.06) by logistic regression. Also, the incidence of nausea was not significantly different (57% supratentorial, 57% spine, 67% infratentorial; P = 0.62) by Dunn's procedure. CONCLUSION: There were no significant differences in the severity of pain or the frequency of nausea based on the craniotomy site.