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M P Paloheimo

Publications and source records attributed to M P Paloheimo.

12 recordsLinked to original sources
PubMed2001

Sensitivity of action potential triggering is normally distributed as a function of mean fractional receptor activation.

In 1968, Waud presented his general pharmacodynamic model consisting of two sub-functions that divide the pharmacodynamic cascade from drug concentration to cell effect/response into two successive steps: Step one (the internal function) characterizes the binding of agonist drug molecules to the post-synaptic receptors and the subsequent receptor activation, and step two (the external/effect function) characterizes the cell response induced by a critical receptor pool activation. According to Waud, the problem of determining the relation between drug concentration and cell response/effect reduces to the second step in the pharmacodynamic cascade. In this paper, we suggest a new external/effect-function, the cumulative Normal population-effect-function. It describes how muscle fibre excitability (all-or-none phenomenon) is distributed as a function of mean fractional receptor activation in a muscle fibre population. This function fits to empirical data and explains logically why the sigmoid muscle effect, from minimal to maximal, is seen in such a narrow range of antagonist concentrations and receptor occupancies.

Action Potentials↗
PubMed1999

Effects of small peripheral temperature changes on the evoked baseline electromyographic response.

BACKGROUND: Since muscle temperature seems to influence the electrically evoked compound muscle action potentials, we wanted to quantificate the effect of light external cooling and warming on evoked responses in a clinical setting. METHODS: In ophthalmic surgical patients (ASA I-III), evoked electromyographic (EMG) responses to supramaximal train-of-four stimuli were measured once a minute. After obtaining an initial baseline (100%) where temperatures of the first dorsal interosseal muscle and the skin above it had stabilised, the patients' hands were cooled to stable temperatures by a blower (room air). A new baseline was established and, subsequently, the hand re-warmed to the starting temperature. The cooling procedure was repeated, operation time allowing. RESULTS: The mean (range) muscle and skin temperature changes were from 36.0 degrees C (35.5-37.1) to 34.6 degrees C (33.2-36.1) and 35.7 degrees C (35.0-36.7) to 32.0 degrees C (29.4-35.6), respectively. The mean (range) change of the EMG-response was 8.0%/degree C (0.3-16.5) for the muscle and 4.1%/degree C (0.3-37.9) for the skin. Wide individual variability was evident. CONCLUSION: The electrically evoked EMG-response is sensitive to even small changes in temperature at the measurement site. Therefore, when applying the evoked EMG in neuromuscular studies, peripheral skin or muscle temperatures need to be monitored, and attempts to stabilise the temperature of the monitored muscles should be made.

Action Potentials↗
PubMed1995

Painless needle insertion in regional anesthesia of the eye.

We examined a new technique of applying topical anesthetic with cotton tip sticks to the conjunctiva before needle insertion in regional anesthesia of the eye. Oxybuprocaine 0.4% and lidocaine 4% were compared with balanced salt solution (BSS) as topical anesthetics of the conjunctiva in Study 1. Ninety patients were randomly assigned into three groups (n = 30) to receive one of the three topical anesthetics in a double-blind manner. Pain of the needle insertions was measured with visual analog scale score (VAS) and quantitative surface electromography (qEMG). Both oxybuprocaine and lidocaine reduced pain significantly when compared to BSS. In Study 2, with healthy volunteers, we compared our previous practice of merely applying three consecutive drops of oxybuprocaine on the conjunctiva before needle insertions to the new technique of placing additional cotton tip sticks soaked in oxybuprocaine on the conjunctiva. We found the needle insertion virtually pain free when the cotton tip sticks were added to the topical anesthesia. The use of this simple method of topical anesthesia before the eye block increases patient comfort significantly.

Adult↗
PubMed1994

Comparison of pH-adjusted bupivacaine 0.75% and a mixture of bupivacaine 0.75% and lidocaine 2%, both with hyaluronidase, in day-case cataract surgery under regional anesthesia.

Alkalinized bupivacaine 0.75% (pH 6.8) and a mixture (1:1) of bupivacaine 0.75% and lidocaine 2%, both with hyaluronidase, were compared in regional ophthalmic anesthesia for day-case cataract surgery. Eighty-two patients were randomized into two groups (n = 39 and 43) to receive one of the two solutions in a double-blind manner. Two intraorbital injections were administered initially: an inferolateral intraconal injection (3 mL) and a medial extraconal injection (3.5 mL). The progress of lid and globe akinesia was examined every 2.5 min up to 25 min and postoperatively. The block was supplemented at 10 and 20 min, if needed. Significantly better globe akinesia was achieved with the bupivacaine-lidocaine mixture; the patients who had received alkalinized bupivacaine needed additional injections significantly more often at 10 and 20 min. In lid akinesia, the onset time and recovery were similar in the two groups. One patient in the alkalinized bupivacaine group felt intraoperative pain, and eight patients in the bupivacaine-lidocaine group and seven in the alkalinized bupivacaine group sensed pain postoperatively from corticosteroid and antibiotic injections. Seventy percent of the pH-adjusted bupivacaine group and 8% of the lidocaine-bupivacaine group had diplopia the day after surgery. Of the two local anesthetic mixtures studied, lidocaine (2%) with bupivacaine (0.75%) provided regional ophthalmic anesthesia of better quality.

Aged↗
PubMed1993

Correlation of motor-evoked potentials, somatosensory-evoked potentials, and the wake-up test in a case of kyphoscoliosis.

The ability to monitor the descending motor pathways of the spinal cord during surgery is an important goal in neurophysiologic monitoring of spinal deformities. This report describes a case of a severe spinal deformity for which instrumentation and reduction carried a significant risk of neurologic complications. During the procedure, changes in neurologic status were monitored simultaneously using both SSEPs and tcMMEPs. The reliability of these two complimentary modalities was then verified by concurrent wake-up tests. This case provides documentation of the reliability of tcMMEP responses when an accurate assessment of motor function was necessary.

Adult↗
PubMed1990

Comparison of non-invasive respiratory and arterial blood gas analysis. A recovery room study on acute respiratory depression.

The effect on invasive and non-invasive oxygen, carbon dioxide and haemoglobin saturation measures of two repeated doses of alfentanil 0.5 microgram/kg were tested in 16 patients scheduled for elective cataract surgery under periocular anaesthesia. Alfentanil caused an acute respiratory depression, which was demonstrated as increased levels of arterial and end-tidal carbon dioxide and concomitant decrease in arterial and end-tidal oxygen levels as well as decreased arterial blood saturation and pulse oximeter readings. There was a good correlation between the non-invasive respiratory parameters and blood gas levels, as well as between pulse oximetry numbers and oxygen saturation of arterial blood. Therefore, hypoventilation and concurrent hypoxaemia can be predicted by monitoring end-tidal CO2.

Aged↗
PubMed1989

Upper facial muscle activity and survival after hypoxic insult in rats.

Spontaneous cerebral biopotentials were monitored during and after hypoxic insults in 30 ketamine-anesthetized rats. Upper facial electromyographic (EMG, mean integrated amplitude) and electroencephalographic (mean zero cross frequency (ZXF) and mean integrated amplitude (MIA] data were recorded within 30 min after reoxygenation and cardiopulmonary resuscitation. The animals were separated into 2 groups based on 24 h survival. EMG in Survivors (n = 16) recovered regularly to pre-insult levels by 30 min after resuscitation. At this time, EMG activity was consistently low in Non-survivors. In contrast, ZXF and MIA, albeit sensitive hypoxia detectors, did not totally discriminate between Survivors and Non-survivors. Absent EMG in Non-survivors may have reflected irreversible hypoxic damage at the brainstem level.

Animals↗
PubMed1989

Transcranial magnetic motor evoked potentials (tcMMEP) for functional monitoring of motor pathways during scoliosis surgery.

Transcranial magnetic motor evoked potentials (tcMMEP) were used to assess the functional integrity of the descending motor pathways. The tcMMEP, recorded bilaterally from anterior tibialis muscles, were evoked by an electric current induced in the motor cortex by a high-intensity transient magnetic field applied to the scalp surface. Potentials were recorded from ten of 12 volunteer subjects and preoperatively in 11 of 11 scoliotic patients. Group mean latency in the volunteers (32.0 +/- 2.1 msec) did not differ from that of the scoliotics (28.6 +/- 5.0 msec), but values in the latter group were more variable. During nitrous oxide-narcotic anesthesia, tcMMEP with reproducible latencies were obtained in 9 of 11 (82%) cases. A small, but statistically significant, increase in latency occurred during anesthesia. Compared with preoperative values (523 +/- 490 microV), individual tcMMEP amplitudes were significantly decreased intraoperatively (163 +/- 153 microV). Although the absolute amplitudes varied widely, the minimum recorded value was over 20 microV. Thus, intraoperative tcMMEP waveforms were readily discriminable from background electrical noise. These results demonstrate the technical feasibility of intraoperative tcMMEP monitoring. Combined somatosensory evoked potential and tcMMEP monitoring may provide a more complete picture of spinal cord function, intraoperatively.

Electromagnetic Fields↗
PubMed1988

Comparison of neuromuscular blockade in upper facial and hypothenar muscles.

Facial and hand muscles are used frequently for monitoring neuromuscular blockade. Therefore, we compared changes in electrically evoked muscle potential magnitude in upper facial and hypothenar muscles after fixed doses of neuromuscular blockers (succinylcholine, 750 micrograms/kg; pancuronium, 70 micrograms/kg; vecuronium, 50 micrograms/kg; and atracurium, 300 micrograms/kg). Face-hand comparisons were made in both anesthetized (nitrous oxide/narcotic, n = 51) and comatose (closed-head injuries, n = 5) patients. In 24 anesthetized patients, complete blockade of the hypothenar muscles prevented quantitative comparison. In the remaining 27 patients, the relaxant effect (as determined by the percentage change from prerelaxant baseline muscle potentials) was significantly smaller (P less than 0.0001) in the upper facial muscles (65 +/- 24% versus 92 +/- 8%, mean +/- SD). All four evoked muscle responses to train-of-four stimulation were detectable in upper facial muscles of the 19 patients receiving non-depolarizing neuromuscular blocking drugs; this pattern was seen in hand muscles of only 7 patients (P less than 0.001). The neuromuscular blockade in both the hand (49 +/- 54%) and the upper facial area (68 +/- 28%, P greater than 0.05) of comatose patients was smaller and more variable than that seen during anesthesia. These results illustrate the value of quantitative monitoring of neuromuscular function, especially during highly variable and unpredictable drug-induced blockade in the comatose state. We conclude that during narcotic-based anesthesia the upper facial and hand muscles are differentially sensitive to commonly used neuromuscular blockers.

Anesthesia, General↗
PubMed1988

A carbon dioxide monitor that does not show the waveform has value.

The author argues that a simple analog needle display can provide the anesthesiologist with the essential information he or she needs when monitoring carbon dioxide in the patient airway. He argues that essentially the most important information is virtually a binary, or all or none, phenomenon; in other words, carbon dioxide is either continuously present in the breathing circuit or is absent. Thus, circuit disconnects and undesirable endotracheal tube locations are readily identified. He relates the analog display of information to that of an automobile speedometer or the hands of a standard wrist watch. The author also compares analog meters with those used by pilots in aviation. He concludes with the argument that the carbon dioxide analyzer provides necessary information without the need to resort to expensive microprocessed displays that would include the waveform and trending, but would substantially increase the cost of the instrument.

Anesthesia, General↗
PubMed1988

Objective assessment of opioid action by facial muscle surface electromyography (SEMG).

1. Activity of the mimetic muscles of the upper face were recorded from awake and anesthetized patients by surface electromyography (SEMG). 2. High amplitude SEMG accompanied ketamine anesthesia and/or the presentation of pain-provoking stimuli. 3. During periods of elevated facial muscle activity, fentanyl or butorphanol decreased SEMG amplitude. 4. The opioid-induced SEMG depression was not consistently associated with either lowered vigilance or analgesia but did provide an objective measure of drug effect.

Adult↗