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Biomedical subjects

J A Litch

Publications and source records attributed to J A Litch.

At least 19 recordsLinked to original sources
PubMed2001

Reascent following resolution of high altitude pulmonary edema (HAPE).

There is an absence of information in the literature regarding reascent to high altitude following resolution of HAPE (high altitude pulmonary edema). This report presents three cases of HAPE that are notable for later reascent to a high summit (up to 8,850 m) within the time course of each expedition. These cases illustrate that careful, gradual reascent following recovery and acclimatization after an episode of HAPE precipitated by rapid ascent may be considered. The pathophysiology of HAPE is reviewed with a focus on the evidence for rapid reversibility of pulmonary vascular injury. The evidence for protective pulmonary vascular remodeling is discussed to further support such a recommendation for cases of uncomplicated HAPE.

Acclimatization↗
PubMed2000

Ketamine anesthesia at high altitude.

There is a clinical need for a safe and effective anesthetic technique in high altitude and remote areas. This report presents a series of 11 consecutive cases documenting the use of ketamine anesthesia in a remote hospital at an altitude of 3,900 m, by primary-care physicians without specialist training in anesthesia. The method of administration is fully described. At a low dose of 2.0 mg/kg, ketamine produces a dissociative anesthesia that does not depress the hypoxic drive, or interfere with the pharyngeal or laryngeal reflexes. Although supplemental oxygen is useful in the recovery phase for less acclimatized individuals, it is usually not required as reductions in oxygen saturation can be raised by physical stimulation that encourages the patient to breathe faster and deeper. The common side effect of emergent nightmares was avoided using midazolam as premedication and a quiet recovery area. This study offers the first available evidence that ketamine with midazolam offers a safe and effective means of anaesthesia at very high altitude, without the need for specialist equipment or training, by careful clinicians experienced in basic airway management.

Acclimatization↗
PubMed2000

High-altitude global amnesia.

A variety of transient focal neurological signs presenting at high altitude have been described without associated acute mountain sickness or other concurrent illness. We report a case series of transient global amnesia at high altitude. The term high-altitude global amnesia (HAGA) is introduced to indicate this condition, and the pathophysiology is discussed. We hypothesize that because of the highly variable ventilatory response to hypoxia and to individual cerebral vasomotor reactivity, individuals with a marked hyperventilatory response could experience significant hypocapnic cerebral vasoconstriction that in turn could cause local hypoxia or ischemia to particular regions of the brain and resulting transient focal neurological impairment.

Adult↗
PubMed2000

Oxygen concentrators for the delivery of supplemental oxygen in remote high-altitude areas.

Oxygen concentrators are a relatively new technology for the delivery of supplemental oxygen. Readily available for domicile use in modern countries, these machines have proved reliable. The application of oxygen concentrators for the supply of medical oxygen in remote high-altitude settings has important cost-saving and supply implications. In our experience at a remote hospital at 3,900 m in the Nepal Himalayas, oxygen concentrators constitute an effective and affordable means to supply medical oxygen. Using an air compressor and 2 zeolite chambers, the machine traps nitrogen from room air compressed to 4 atm, thus concentrating oxygen in the expressed gas. At delivery flow rates of 2 to 5 liters per minute, oxygen concentrations greater than 80% can be maintained. An electric power requirement of less than 400 W can be provided from a variety of sources, including a small gasoline generator, a solar or wind power system with battery store, or a domestic or commercial power source. At our facility, a cost savings of 75% for supplemental oxygen was found in favor of the oxygen concentrator over cylinders (0.17 US cents per liter vs 0.79 US cents per liter).

Altitude Sickness↗
PubMed1999

Safety of rescuers.

Explore the source record for details and available documents.

Head Protective Devices↗
PubMed1999

Everest or bust: a cross sectional, epidemiological study of acute mountain sickness at 4243 meters in the Himalayas.

BACKGROUND: Thousand of tourists trek in the Himalayas every season and risk acute mountain sickness (AMS). Prior studies have shown that the rate of ascent is one of the primary risk factors for the development of AMS but the role of body hydration, age, gender, alcohol and medication usage, body weight, and altitude of residence continues to be in question. This study estimates the incidence of AMS at 4234 m at Pheriche in the Everest region, explores a number of risk factors predisposing trekkers to a diagnosis of AMS and attempts to quantify the relationship between the Lake Louise AMS diagnostic criteria and oxygen saturation. METHODS: Demographic data and information about risk factors felt to place trekkers at increased risk of AMS was collected from 550 trekkers for 1 mo in the fall of 1996 at 4234 m in the Everest region. RESULTS: Diagnosis of AMS was made in 29.8% (159 trekkers) of the study population. Low water intake (odds ratio 1.57; 95% confidence interval,1.02-2.40), the presence of respiratory symptoms (odds ratio 2.21; 95% confidence interval, 1.43-3.40), and an oxygen saturation below 85% at 4243 m (odds ratio 2.35; 95% confidence interval, 1.55-3.56) were identified as independent risk factors for AMS diagnosis in this sample. In addition, AMS risk decreased 18.7% (95% confidence interval, 3.8-31.2%) for each additional night spent between Lukla (2804 m) and the study site at 4243 m. CONCLUSION: Increased reported fluid intake decreased the risk of AMS in this cross sectional prospective study. Further studies need to be done to confirm this finding before recommendations can be made. In addition the rise in the risk of AMS as the rate of ascent increased along this popular Everest trek was quantified for the first time. Finally, AMS was also associated with respiratory symptoms and with a lower oxygen saturation.

Acclimatization↗
PubMed1998

Cough induced stress fracture and arthropathy of the ribs at extreme altitude.

Cough and chest wall pain at high altitude have only received passing mention in the medical literature. Increased minute ventilation of cold dry air at very high altitude is likely to cause airway irritation. This in turn may result in airway drying, mucus production, postnasal drip from vasomotor rhinitis, and bronchospasm acting individually or in combination to stimulate the vagal cough reflex. The cough is exacerbated further at extreme altitudes above 5500 m, and may result in intercostal muscle strain and single or multiple rib fractures. We present a case of multiple cough induced stress fractures and arthropathy documented by technetium-99 bone scan in a high altitude climber and suggest the addition of the term High Altitude Cough Syndrome (HACS) to the medical syntax to identify this discrete medical problem of exposure to very high altitude.

Adult↗