Category: Unilateral Phrenic Injury

Recovery after Unilateral Phrenic Injury Associated with Coronary Artery Revascularization: Discussion (6)

Peripheral nerve growth rates have been shown to differ in the proximal and distal segments of a peripheral nerve ranging from 1 to 8 mm per day. Accurate regeneration rates have not been established for the phrenic nerve. The data from this study allow an approximation of the rate of recovery after injury during bypass surgery. Assuming that the injury occurs at the midpericardium, the…

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Recovery after Unilateral Phrenic Injury Associated with Coronary Artery Revascularization: Discussion (5)

Recovery after Unilateral Phrenic Injury Associated with Coronary Artery Revascularization: Discussion (5)

Indirect evidence has accrued to suggest that the phrenic nerve may become “frostbitten” during bypass surgery. Experimentally, damage to large myelinated fibers has been shown with 8°C exposure for as little as 30 min. Radiographic evidence of diaphragmatic dysfunction has been shown in patients undergoing CAB surgery with topical cold cardioplegia. This is less common with devices used to prevent direct contact between the slush…

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Recovery after Unilateral Phrenic Injury Associated with Coronary Artery Revascularization: Discussion (4)

When demyelination is more extensive, recovery occurs by synthesis of myelin by proliferating Schwann cells. Although this type of injury usually resolves by 12 weeks, internodal distances may be permanently shorter than normal, leading to a reduction in maximal conduction velocity. The time course of recovery in this study is most compatible with an axonal degeneration. Recovery after axonal degeneration is a complex process. If…

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Recovery after Unilateral Phrenic Injury Associated with Coronary Artery Revascularization: Discussion (3)

Recovery after Unilateral Phrenic Injury Associated with Coronary Artery Revascularization: Discussion (3)

The simultaneous comparison of measurements of phrenic nerve conduction, lung volume and inspiratory muscle strength facilitated an evaluation of the functional effects of unilateral phrenic nerve paresis or paralysis. The vital capacity increased when diaphragmatic EMG activity was first obtained. Similarly, inspiratory muscle strength improved, coincident with the first elicitation of a diaphragmatic EMG response. The Pimax was a more sensitive indicator of phrenic nerve…

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Recovery after Unilateral Phrenic Injury Associated with Coronary Artery Revascularization: Discussion (2)

Although phrenic nerve paresis or paralysis is generally believed to have a good prognosis, few studies to date have addressed the rate of phrenic nerve recovery. Chandler et al followed up five patients with bilateral diaphragmatic paralysis after bypass surgery and noted recovery, based on spirometric measurements, in four, partial recovery in three, and complete recovery in one. This recovery was variable occurring over approximately…

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Recovery after Unilateral Phrenic Injury Associated with Coronary Artery Revascularization: Discussion (1)

Recovery after Unilateral Phrenic Injury Associated with Coronary Artery Revascularization: Discussion (1)

Diaphragmatic paresis or paralysis is a well recognized complication of CAB surgery. The reported incidence of phrenic nerve palsy after bypass surgery has varied considerably depending on the methods used to evaluate the phrenic nerves. In two studies in which phrenic nerve electrophysiologic tests were utilized, phrenic nerve dysfunction was identified in ll2 and 9 percent of patients undergoing bypass surgery. Unilateral diaphragmatic paralysis, although…

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Recovery after Unilateral Phrenic Injury Associated with Coronary Artery Revascularization: Results (3)

Figure-2

Expiratory muscle strength was within normal limits in all five patients studied and changed little in any patient on successive retesting after surgery. The average percentage increase in PEmax was 13 percent, compared with a mean increase of 84 percent in Pimax. Buy Asthma Inhalers Online A restrictive pattern was noted on spirometric measurements in four of five patients on the initial study (FVC range,…

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Recovery after Unilateral Phrenic Injury Associated with Coronary Artery Revascularization: Results (2)

Figure-1

An elevated left hemidiaphragm and partial left lower lobe atelectasis were noted in all patients on postoperative day 3 and discharge chest radiographs (Table 1). Paradoxic movement of the left hemidiaphragm was seen fluoroscopically during sniff maneuvers in all patients on the initial study. Left phrenic paralysis was confirmed in four patients by absence of an electromyographic response to left phrenic nerve stimulation when first…

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Recovery after Unilateral Phrenic Injury Associated with Coronary Artery Revascularization: Results (1)

There was no indication on history or physical examination of preexisting pulmonary disease in any of the five patients studied. None had undergone previous thoracic or cervical surgery. Preoperative chest radiographs were normal in all patients. Coronary artery bypass surgery proceeded uneventfully in all patients. Pertinent operative details are provided in Table 1 for each of the five patients. Four patients had left internal mammary…

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Recovery after Unilateral Phrenic Injury Associated with Coronary Artery Revascularization: Methods (2)

Recovery after Unilateral Phrenic Injury Associated with Coronary Artery Revascularization: Methods (2)

The phrenic nerves were studied by measuring latency and the CDAP after transcutaneous supramaximal phrenic nerve stimulation. The diaphragm response was measured with two surface disc electrodes, one placed over the xiphoid process of the sternum and the other over the ipsilateral seventh intercostal space at the costochondral junction. The parameters measured were the time from stimulus to onset of diaphragmatic EMC activity (latency of…

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