Biomedical subjects

J E Scharf

Publications and source records attributed to J E Scharf.

7 recordsLinked to original sources

PubMed1998

Spectral analysis of photoplethysmograms from radial forearm free flaps.

OBJECTIVE: Photoplethysmography utilizes a green-light-emitting diode to transmit light into a tissue. Reflected light from hemoglobin in dermal capillary red blood cells is received by a photo detector and is analyzed as light intensity along a frequency spectrum. This method of analysis allows for the removal of "noise" above (stray light and alternating current [AC]) and below (room vibrations and respiratory motion) the peak signal (1 to 2 Hz) and results in a means to distinguish between perfused and nonperfused tissues. METHODS: Twenty-two of 30 consecutive radial forearm free flap (RFFF) patients were enrolled in an approved human studies protocol to collect descriptive data for RFFFs that were perfused, arterial occluded, and venous occluded. The protocol was performed following completion of flap elevation and prior to pedicle ligation, flap inset, and microvascular anastomoses. Six 90-second measurements per flap were obtained (n = 132), processed by fast Fourier transform (FFT), and analyzed by blinded reviewers to determine their state of perfusion. Signal was collected 5 minutes after the onset or release of individual vessel occlusion. RESULTS: The reviewers' interpretations were compared with the status of the pedicle and analyzed for sensitivity (0.96), specificity (0.95), and positive predictive value (0.98). CONCLUSIONS: FFT analysis of photoplethysmograms from RFFF patients provides an accurate and rapid means for determining RFFF pedicle vessel patency. Photoplethysmography may provide a clinically useful tool for postoperative perfusion monitoring of free flaps in the future.

Equipment Design↗

PubMed1997

Preemptive ketamine decreases postoperative narcotic requirements in patients undergoing abdominal surgery.

The aim of this study was to determine if preemptive administration of systemic ketamine decreases postoperative pain when compared with postwound closure administration of ketamine. Patients undergoing abdominal procedures were randomized into a preemptive or postwound closure ketamine administration group. Before surgical incision, patients in the preemptive group (n = 20) were given 0.5 mg/kg ketamine followed by a ketamine infusion of 10 micrograms.kg-1.min-1, which was discontinued at abdominal closure. The patients in the postwound closure (n = 20) group were given 0.5 mg/kg of ketamine immediately after abdominal closure. Postoperatively, all patients received intravenous (IV) morphine in the postanesthesia care unit (PACU) and were started on IV morphine patient-controlled analgesia after discharge from the PACU. Postoperative pain was assessed by measuring morphine consumption and visual analog scale (0-100 mm) pain scores at rest. Patients in the preemptive group had significantly lower morphine consumption on postoperative Days 1 and 2. No significant intergroup differences were seen in the pain scores throughout the study period. Preemptive ketamine decreased postoperative opioid requirements, which was observed long after the normal expected duration of ketamine.

Abdomen↗

PubMed1996

Malignant hyperthermia involving the administration of desflurane.

PURPOSE: This report describes an episode of malignant hyperthermia (MH) in a ten year old boy receiving desflurane anaesthesia. CLINICAL FEATURES: Following induction of general endotracheal anaesthesia with thiopentone and succinylcholine, desflurane was administered for maintenance of anaesthesia. Ten minutes after commencing desflurane administration, heart rate and PETCO2 increased to 165 bpm and 50 mmHg, respectively. Initially, the tachycardia was attributed to a sympathetic response secondary to desflurane. Desflurane was discontinued and isoflurane was started. Minute ventilation was increased to decrease PETCO2. Over the next five minutes, temperature increased to 38.4 degrees C as the PETCO2 increased to above 60 mmHg. Venous and arterial blood gases were drawn which showed acidosis and hypercapnia. Temperature and PETCO2 continued to increase, reaching peak values of 41 degrees C and 77 mmHg, respectively. Efforts to cool the patient were made. A total of 220 mg dantrolene sodium was administered iv. Following dantrolene, the temperature increase and acidosis subsided. Heart rate and PETCO2 decreased to 130 bpm and 36 mmHg, respectively. The surgical procedure was expeditiously performed. Postoperatively, in the Paediatric Intensive Care Unit, a dantrolene infusion of 20 mg.hr-1 was administered for 12 hr. The trachea was extubated the following morning. Several days later, the patient underwent another surgical procedure without complications using MH-safe anaesthetics. CONCLUSION: Onset of tachycardia in a patient receiving desflurane may initially be attributed to desflurane-induced sympathetic hyperactivity. This poses a clinical challenge in the diagnosis of MH during desflurane anaesthesia.

Anesthetics, Inhalation↗

PubMed1996

Signal processing methods for pulse oximetry.

Current signal processing technology has driven many advances in almost every aspect of life, including medical applications. It follows that applying signal processing techniques to pulse oximetry could also provide major improvements. This research was designed to identify and implement one or more techniques that could improve pulse oximetry oxygen saturation (SpO2) measurements. The hypothesis was that frequency domain analysis could more easily extract the cardiac rate and amplitude of interest from the time domain signal. The focus was on the digital signal processing algorithms that had potential to improve pulse oximetry readings, and then test those algorithms. This was accomplished using the Fast Fourier Transform (FFT) and the Discrete Cosine Transform (DCT). The results indicate that the FFT and DCT computation of oxygen saturation were as accurate without averaging, as weighted moving average (WMA) algorithms currently being used, and directly indicate when erroneous calculations occur.

Algorithms↗

PubMedDate not supplied

Effect of anesthetic technique on acute formalin-induced pain in mice.

BACKGROUND AND OBJECTIVES: The aim of this study was to determine if anesthetic technique influences the degree of acute formalin-induced pain in mice. METHODS: Mice were randomized to receive either combined spinal/general anesthesia or general anesthesia prior to a subcutaneous injection of formalin in a hindpaw. The mice in the combined spinal/general anesthesia group received halothane anesthesia and subarachnoid lidocaine. The mice in the general anesthesia group received halothane anesthesia only. After the mice recovered from anesthesia, paw-licking behavior was recorded for 1 hour. A statistical comparison was made using analysis of variance and the Kolmogorov-Smirnov test. RESULTS: The mice in the combined spinal/general anesthesia group (n = 20) had a significantly shorter time to first paw lick (mean +/- SD) after formalin injection compared to the mice in the general anesthesia group (n = 20) (16.1 +/- 4.5 vs. 22.1 +/- 6.3 min, P = .002). No difference was observed in the number of paw licks in the mice receiving either combined spinal/general anesthesia or general anesthesia (40 +/- 15 vs. 44 +/- 18, P = .47). No difference was observed in the duration of paw licking in either group (231 +/- 76 vs. 237 +/- 124 s, P = .84). CONCLUSIONS: The administration of a pre-emptive subarachnoid lidocaine block in the combined spinal/general anesthesia group did not reduce the degree of formalin-induced paw-licking behavior. Combined spinal/general anesthesia did not decrease acute formalin-induced pain in mice.

Anesthesia, General↗

PubMedDate not supplied

The effect of pre-emptive fentanyl on formalin pain in mice.

BACKGROUND AND OBJECTIVES: The aim of this study was to determine if pre-emptive systemic fentanyl administration would decrease the amount of formalin pain in mice. METHODS: Under halothane anesthesia, formalin was injected in the hindpaw of mice. The animals were randomly assigned to receive no systemic fentanyl (group 1; n = 20); subcutaneous fentanyl, 50 micrograms/kg 5 minutes prior to formalin injection (group 2; n = 20); or subcutaneous fentanyl, 50 micrograms/kg 5 minutes after formalin injection (group 3; n = 20). After recovery from anesthesia, the formalin-induced paw-licking response was observed for 1 hour. The time to first paw lick, the number of paw licks, and the duration of paw licking were compared among the groups with an analysis of variance. RESULTS: The fentanyl-treated mice in groups 2 and 3 had a significantly longer time to first paw lick, had a lower number of paw licks, and had a shorter duration of paw licking compared to the control mice in group 1. There was no significant difference in formalin pain behavior between the mice receiving fentanyl before or after formalin injection. CONCLUSIONS: Pre-emptive administration of subcutaneous fentanyl does not decrease the severity of acute pain in mice.

Analgesics, Opioid↗

PubMedDate not supplied

Effect of type of anesthesia and lower-abdominal laparotomy in mice on the cytokine response to acute stress.

BACKGROUND AND OBJECTIVE: Recent emphasis has been placed on the accuracy of systemic cytokine levels as an index to the severity of acute surgical stress. In this investigation, a murine animal model was developed to determine the effect of the type of anesthesia on the cytokine response to a standard surgical stress. METHODS: The initial phase was designed to assess the severity of the acute stress response to a standard surgical stimulus by measuring the release of proinflammtory cytokines in 30 Balb C mice subjected to halothane anesthesia and exploratory laparotomy. The severity of the operative stress was assessed by serum levels of epinephrine and C-reactive protein at 0, 1, 2, 4, and 6 hours and compared with systemic levels of interleukin-1, interleukin-6, and tumor necrosis factor-alpha. In the next phase, in order to assess the stress response associated with the induction of anesthesia without surgery. IL-6 was measured in 10 mice undergoing halothane anesthesia or combined halothane-spinal anesthesia. In the final series of experiments, designed to assess the effect of anesthetic type on the stress response induced by the standard surgical stress, 40 mice underwent halothane anesthesia with laparotomy or combined halothane-spinal anesthesia with laparotomy. RESULTS: Following exploratory laparotomy, serum epinephrine was significantly elevated at 2 hours (P < .05 vs time 0), while C-reactive protein became elevated at 6 hours (P < .05). Serum interleukin-6 rose rapidly, reaching a peak at hour 2 (P < .001) and then declining through hour 6, but interleukin-1 and tumor necrosis factor, were elevated in only a few animals undergoing laparotomy. Neither halothane nor combined halothane/spinal anesthesia had any effect on the interleukin-6 stress response in the absence of surgical stress. Similarly, the degree of operative stress after exploratory laparotomy was not affected by the type of anesthesia. CONCLUSIONS: Serum interleukin-6 was the best marker for acute surgical stress, which could not be induced by anesthetic interventions alone. The combination of halothane with spinal anesthesia was not able to attenuate the degree of stress as compared with halothane anesthesia alone in animals undergoing abdominal surgery.

Abdomen↗