A rare cause of intra-operative hypoxaemia.

A 25-year-old man underwent left inguinal hernia repair. Following induction of anaesthesia, desaturation below 90% was noted which persisted despite correct placement of an endotracheal tube and ventilation with 100% oxygen. Surgery was allowed to continue, and the suspected diagnosis of pulmonary arterio-venous malformation was confirmed post-operatively by computerized axial tomography and arteriography. The investigation and treatment are described, and the diagnostic value of pulse oximetry in this case is emphasized.

The lateral position--dependant occipital approach--to pineal and medial occipitoparietal lesions. Technical note.

A recent modification of the occipital transtentorial approach to the pineal region and medial-posterior hemisphere is described. The patient is operated upon in a lateral reclining (park bench) position with the side to undergo occipitoparietal craniotomy, slightly dependant. Following dural opening to the margins of the superior sagittal and lateral sinuses, gentle traction with a brain spatula facilitates the occipital transtentorial and transfalcine approach to the incisural region. Ventricular or spinal fluid drainage is often helpful. The occipital lobe falls away from the midline and falcotentorial regions by gravity. Absence of occipital parasagittal bridging veins is a helpful feature and careful convexity dural opening allows the occipital lobe to move laterally. Microsurgical treatment of pineal, splenial, falcotentorial and medial posterior hemisphere lesions may be greatly facilitated. Our experience with six cases is presented. To date, published results of this operative approach have been excellent with the risk of hemianopsia, parenchymal venous infarction, and air embolus much lessened or eliminated.

Anaesthesia during the Falklands campaign. The experience of the Royal Navy.

The work of nine Naval anaesthetists deployed with the Task Force during the Falklands campaign is described. The anaesthetists worked in a field hospital (Ajax Bay), a hospital ship (SS Uganda), a troop ship (SS Camberra), aircraft carriers (HMS Hermes and HMS Invincible) and a Royal Fleet Auxiliary (Tidespring). The problems of staffing and providing the stores for various teams in different locations at short notice are discussed.

Subdural hematomas. I. Acute subdural hematoma: progress in definition, clinical pathology, and therapy.

A series of 206 patients with clotted subdural hematomas operated within 3 days of closed head injury is presented. Sixty-two percent (128) were operated within 24 hours of trauma (acute subdural hematoma) carrying a high incidence of sterotypic motor posturing, impaired oculomotor reflexes, and unilateral dilated fixed pupil. A functional recovery occurred in 27% and a vegetative state or death resulted in 62%. The remaining 38% were operated after 24 but within 72 hours from injury (early subacute subdural hematoma) and generally had less severe neurologic dysfunction. A functional recovery occurred in 54% and vegetative state or death in 34%. The 128 acute cases are presented in detail to establish a logical basis for time differential. The cases requiring operation within 12 hours of injury were the most challenging. Improved outcome is felt to result from prompt referral and large craniotomy in the earliest hours after injury, combined with careful postoperative monitoring. Clinical, operative and autopsy findings are presented and discussed in relation to pathogenesis.

Intravascular aggregation after acute intracranial hypertension by epidural balloon compression in cats.

The authors have studied the effect of acute intracranial hypertension produced by placement of an epidural balloon (control group) in cats, on cerebral perfusion, evoked responses, and hematological parameters. These elements were measured in similarly injured animals which underwent isovolemic hemodilution with dextran 75, after relief of intracranial hypertension. Four hours after balloon deflation, perfusion was markedly impaired in 30% of the control group, and was reduced to 11% in the dextran-infused group. The suppressed N1 amplitude of somatosensory evoked responses on the compression side, the reduced platelet aggregability, and the erythrocyte-deformability by intracranial hypertension were all significantly more restored in the dextran-infused group after decompression. The percentage of platelets with volumes between 21.75 and 48.75 cu mu (normal 9.75 to 12.75 cu mu) significantly increased after decompression. Activation of platelets during intracranial hypertension leads to an increase in platelet volume from platelet aggregation, and correlates with a decrease in platelet aggregability. It was also suggested that reduction of erythrocyte deformability was not caused by erythrocyte aggregation. The authors emphasize the role of intravascular factors such as vascular obstruction by platelet aggregates, and difficulty in passage of erythrocytes through capillaries due to reduced deformability, in the disturbance of the microcirculation following acute intracranial hypertension. The protective effect of dextran 75 by inhibition of platelets as well as hemodilution is stressed.

An unusual case of penetrating head injury with excellent recovery.

We report the remarkable case of the passage of a heavy metal rod through the head of a 42-year-old man. The patient had an excellent outcome because of prompt and efficient rescue efforts combined with transport to a major neurosurgical trauma center. Reference is made to a somewhat similar case publicized over 130 years ago.

Traumatic subdural hygroma.

The authors report a series of 80 cases of traumatic subdural hygroma and discuss the clinical and radiological features, management, surgical results, and pathogenesis. Changes in mental status without focal signs of brain damage were noted in over 50% of the cases. A clinical course marked by stabilization without complete recovery of neurological function was found in over 40% of the cases of "simple hygroma." The lumbar cerebrospinal fluid often showed hemorrhage and elevation of the protein content. Skull fractures were found in 39% of the cases, and subdural hygromas were associated with cerebral atrophy, cortical contusions, subdural hematomas, and overlying epidural hematomas. The characteristic angiographic and computed tomographic scan findings are discussed, as are surgical pathology and outcome. Several theories of pathogenesis are presented. The authors advocate simple burr hole drainage as the treatment of choice. Significant reaccumulation may occur occasionally.

Influence of respiratory stress and hypertension upon the blood-brain barrier.

The effects of acute hypertension and respiratory stress induced by Aramine (metaraminol bitartrate) upon blood-brain barrier (BBB) permeability to horseradish peroxidase (HRP) were studied in adult inbred white rats. The BBB permeability was quantitated by slicing the brain of each animal into 500-mu thick sections, incubating the sections using the Reese-Karnovsky method, and counting all observed HRP perivascular exudates. No evidence of BBB compromise or significant elevation of blood pressure (BP) was observed in the following experimental groups: 1) control group of five animals; 2) hyperventilated group of five animals (final mean arterial blood gases; pO2, 104.2 mm Hg; pCO2, 24.8 mm Hg; pH, 7.53); 3) anoxic-stress group of five animals (final mean arterial blood gases; pO2, 31.4 mm Hg; pCO2, 58.2 mm Hg; pH 7.21). However, in a group of 15 animals subjected to anoxic stress followed by hyperventilation, in addition to extreme changes in the levels of arterial blood gases, a significant BP increase occurred (mean BP increase per second, 3.43 +/- 0.25 mm Hg; final mean BP, 163.3 +/- 3.18 mm Hg); as well as significant BBB opening (mean number of HRP exudates per animal, 12.2 +/- 0.85). Likewise, a final group of 10 animals given intravenous Aramine displayed a significant systemic BP elevation (mean BP increase per second, 6.9 +/- 0.38 mm Hg; final mean BP, 165.8 +/- 3.16 mm Hg), accompanied by BBB opening (mean number of exudates per animal, 51.5 +/- 5.95). The variable most strongly associated with the degree of barrier opening was the rate of BP rise (correlation coefficient = +0.84).

Acute intracranial hypertension and auditory brain-stem responses. Part 3: The effects of posterior fossa mass lesions on brain-stem function.

The auditory brain-stem responses (BER's), infratentorial intracranial pressure (ICP), systemic blood pressure (BP), and heart rate were recorded before, during and after expansion of an infratentorial epidural mass in anesthetized cats. Two types of BER's to increasing posterior fossa pressure were noted. In Type 1, there was predominantly suppression of the electrical activity of the auditory nuclei of the upper brain stem (Waves V and IV) and upward transtentorial herniation of the midbrain. In Type 2, the neural activity of the lower brain-stem nuclei (Waves III and II) was affected as well as that of the upper brain stem. There was upward and foraminal impaction of the brain stem and cerebellum which was confirmed by the postmortem brain sections. The change in the amplitudes of BER Waves V and III proved useful in detecting upward transtentorial herniation of the midbrain and foraminal herniation of the cerebellum in acute expanding lesions of the posterior fossa. Medullary paralysis was also detected by observing Wave III.

Acute renal failure following cerebral angiography and infusion computerized tomography. Case report.

The authors report a case in which acute renal failure developed following angiography and computerized tomography with infusion of contrast material performed within the same day.

Acute intracranial hypertension and auditory brain-stem responses. Part 2: The effects of brain-stem movement on the auditory brain-stem responses due to transtentorial herniation.

Movement of the upper brain stem (inferior colliculus) was correlated with the alterations in the amplitude of wave V of the auditory brain-stem responses (BER's) during supratentorial brain compression in cats. In vivo observation of the brain stem and postmortem inspection show that suppression of the amplitude of BER wave V reflects the extent of caudal displacement of the inferior colliculus. Marked suppression of the amplitude of BER wave V (approximately 30% of control) correlates with the beginning of transtentorial herniation, and complete suppression of the wave V indicates complete transtentorial herniation of the brain-stem and supratentorial structures. The BER wave V is thought to be a sensitive index of caudal movement of the upper brain stem due to transtentorial herniation.

Acute intracranial hypertension and auditory brain-stem responses. Part 1: Changes in the aduitory brain-stem and somatosensory evoked responses in intracranial hypertension in cats.

Changes in auditory brain-stem responses (BER's) and somatosensory evoked responses (SER's) were investigated to correlate mass volume, intracranial pressure, and neurological dysfunction in mass-induced intracranial hypertension in cats. As the intracranial pressure was raised by expansion of a supratentorial balloon, the late components of the SER's were suppressed first, followed by the early components of the SER's, then Wave V and Wave IV of the BER's, in that order. This suggests that the nonspecific reticular projections are most vulnerable to compression ischemia, and the specific somatosensory pathways are the next most vulnerable. Neural activity of the auditory pathways in the upper brain stem was also gradually suppressed, but less so than that of the somatosensory pathways. After complete transtentorial herniation, in spite of immediate mass evacuation, the function of the somatosensory pathways was greatly impaired, often irreversibly. The neural activity of the auditory pathways in the upper brain stem revealed progressive recovery during a 3-hour period. The measurements of BER Wave V is thought to be useful in predicting transtentorial herniation.